ORNL Offers a Brief Look at MSR/LFTR Economies

A recent ORNL report, Fast Spectrum Molten Salt Reactor Options, offers some insight into the cost lowering potential of MSR nuclear technology. Since Nuclear Green has always had an interest in the cost lowering potential of MSR technology, I intend to review the cost related information included in this report, while in some cases offering a context for that information.

The "Fast Spectrum" report does not offer and cost evaluation in terms of dollar costs, indeed this would not be possible. The report offers an overview of technical options, and no dollar cost evaluation is possible outside the context of a specific design project. The report acknowledges,

A confident assessment of the economic performance of an FS-MSR is not yet possible. Technology, regulatory requirements, and market conditions have changed significantly over the 40 years since the economic assessments accompanying the MSBR; therefore, the cost inferences drawn from the earlier work have such large error bands that they provide little guidance. Additionally, the neutron spectrum of the present evaluation alters the fuel cycle both in and outside the power plant site sufficiently that direct analogies to other reactor concepts are challenging. The most challenging aspect of reporting a cost for an FS-MSR, however, arises from the concept flexibility. A no-heavy-metal reprocessing design variant has a plant layout much different from that of a full-recycle plant intending to directly accept used LWR fuel as its fuel source. Similarly, a plant intending to produce gasoline as its primary product has an entirely different power cycle compared with an electricity generator.

Overall economic tendencies, however, can be estimated by comparing FS-MSR attributes with those of other nuclear power systems. A summary of FS-MSR attributes and their cost implications is provided in Table 2. A primary cost metric for any power plant is its thermal efficiency. FS-MSRs, as high- temperature power plants, are anticipated to have 45–48% thermal efficiencies, a 12–15% efficiency advantage over LWRs. As refueling for an FS-MSR would be performed on-line, the plant availability would be expected to eventually, once maintenance techniques were developed and matured, surpass that for an LWR.

Thus costs are evaluated in relationship to the cost of Light Water Reactor costs. For example, the absence of a fuel fabrication requirement would lower FMSR costs and indeed all MSR costs relative to LWRs

Other FMSR characteristics that would tend to lower capital costs noted by the Fast Spectrum report would include,

* No fuel handling equipment or pool storage facilities
* No irradiated cladding or matrix material in ultimate waste stream
* Large temperature reactivity coefficient
* No cladding- or matrix-based temperature limits in accident scenarios
* Safe shutdown possible through geometry control in accident scenarios
* Higher primary coolant volumetric heat capacity
* Visually transparent, low-pressure, chemically stable coolant

In addition to these cost lowering characteristics, the capacity of all MSRs to operate at a one atmosphere pressure offers a further and important cost lowering potential.

The ORNL Fast Spectrum report also noted characteristics of FMSRs that would lower electrical costs to customers, or increase utility revenue per unit of electricity generated. These include,

* No cladding-based burn up limits
* Higher operating temperature
* Flexible input fuel chemical form
* Flexible input fuel isotopic content

A number of FMSR characteristics that would raise capital costs include,

* No cladding as fission product barrier with a substitute fission product barrier
* Higher operating temperature
* Highly radioactive, fissile-bearing primary coolant
* Potential for safeguards concerns with separated material
* Material corrosion problems

In the case of materials corrosion, it should be noted that there is a low cost work around, if the designer is willing to accept a somewhat lower but still high by LWR operating temperature.

One MSR characteristics offer a mixed cost picture. This was:

* Continuous separation of fission products (and reduction of source term in accident scenarios)

Not only did continuous separation have potential to lower safety related manufacturing and construction costs, but it offered a potential for dramatically lowering regulatory costs. If gaseous and volatile fission products are removed from a reactor as they are produced by nuclear fission, then the motive for most aspects of nuclear regulation is disappears. Thus the cost of nuclear regulation can be lowered. In addition, if separated from the coolant salts, many fission products become salable, either immediately or after a laps of some time. Thus fission product separation can lead to a new revenue stream. Finally although fission product removal devices add to capital costs, their cost can be lowered if Molten Salt Reactors are mass-produced.

It should be noted that the capital cost raising and lowering picture is similar other forms of MSR, with factors such as coolant salt choice, core design including graphite use, and relative neutron speed (thermal, epithermal, and fast), effecting capital costs.

The Fast MSR offers a tool for managing the actinide content of nuclear waste. . In 1991, Uri Gat, and J. R. Engel of ORNL, and C. H. Dodds, of the University of Tennessee, proposed burning fissile fuel from dismantled nuclear weapons in LFTRs, as a means of nuclear deproliferation. That is the process of destroying the raw materials of nuclear weapons.

V. V. Ignatiev, S. A. Konakov, S. A. Subbotine, and R. Y. Zakirov of the Kurchatov Institute in Moscow, and K. Grebenkine proposed the use of Molten Salt Reactors as a means of disposing of nuclear waste. They noted that LFTRs had advantages over Liquid Metal reactors for nuclear waste disposal. The Russian research has lead to the development of the MOSART reactor design. The MOSART is a liquid salt fuel reactor concept intended to burn nuclear waste.
A similar proposal has come from Charles W. Forsberg of ORNL.

The integral Fast Reactor can perform a similar function. and while I have come to appreciate the IFR design, it still has safety problems that would not trouble a fast MSR design. In addition, fast reactors require very large start up charges, in comparison to MSR thermal thorium breeders. The large size of fast start up charges limits their scalability. Thus ten times as many LFTR can be started with the plutonium from nuclear waste, as IFRs or FMSRs. Fast reactors thus are an option for disposing of plutonium from nuclear waste. LFTRs can be started with Reactor grade plutonium (RGP), U-235 or U-233 if it is available. They can be started with a mixture of reactor fuels, or they can be started with all three. The current American stockpile of RGP is gig enough to start enough LFTRs to supply the entire American electrical demand and then some.

Some IFR advocates argue that high breeding ratio IFRs are rapidly scalable because they can produce a very large amount of nuclear fuel. But IFR design research and development has to date largely focused on IFRs capable of burning RGP with breeding ratios similar to those of thermal LFTR breeders. Higher IFR breeding ratios are undoubtedly possible, but they would require much R&D and would never be as safe as FMSRs. Thus RGP can be disposed of by fast reactors, but Lars Jorgensen has established that a fleet of thermal LFTRs can dispose of our entire stock of RGP in under 300 years. Thus if it is viewed as desirable to use the RGP found in "nuclear waste" to start thermal breeder LFTRs, it can be used to start hundreds of LFTRs. Since actinide disposal is the largest single problem associated with the so called nuclear waste issue, the thermal LFTR-RGP start option may well represent the best option for nuclear waste management.

At any rate ORNL FMSR report, offers further support for the contention that MSRs have the potential for lowering nuclear costs. The cost lowering features of the FMSR are all available in high scalable thermal spectrum LFTRs, as well as uranium fueled MSR designs. In addition small MSRs can be built in large numbers in factories. Factory produced small MSR/LFTR modules can be shipped by truck or by train to final assembly sites, or completely assembled in factories and shipped by barge. Not only can they be used to provide electrical power, but they can produce industrial heat, serve as the basis of combined heat and power systems, and even include bottom cycle desalinization. Thus the small MSR may prove to have not only a lower cost than conventional nuclear power plants, but superior versatility.

It is clear then that if breeder scalability and rapid manufacture is desirable, the thermal MSR/LFTR path holds significant advantages over the FMSR or IFR fast breeder approach.

DA Ryan and the Miraculous MSR Graphite Fire

And the angel of the LORD appeared unto him in a flame of fire out of the midst of a bush: and he looked, and, behold, the bush burned with fire, and the bush was not consumed. - Exodus 3:2

When I began my investigation of the graphite fire risks this spring, I had formed no fixed opinion about the supposed danger. I had, of course, run across numerous references to graphite fire risks, including a statement from the redoubtable Ed Lyman of the ever vigilant anti-nuclear Union of Concerned Scientists. Lyman tells us,

A second unresolved safety issue concerns the reactor’s graphite coolant and fuel pebbles. When exposed to air, graphite burns at a temperature of 400°C, and the reaction can become self-sustaining at 550°C—well below the typical operating temperature of the PBMR. Graphite also burns in the presence of water. Thus extraordinary measures would be needed to prevent air and water from entering the core. Yet according to one expert, “air ingress cannot be eliminated by design.”

Yet a statement from General Atomics, a business which has designed and built graphite core reactors claims,

Numerous tests and calculations have shown that it is virtually impossible to burn high-purity, nuclear-grade graphites. Graphite has been heated to white-hot temperatures (~1650°C) without incurring ignition or self-sustained combustion. After removing the heat source, the graphite cooled to room temperature. Unlike nuclear-grade graphite, charcoal and coal burn at rapid rates because:

* They contain high levels of impurities that catalyze the reaction.
* They are very porous, which provides a large internal surface area, resulting in more homogeneous oxidation.
* They generate volatile gases (e.g. methane), which react exothermically to increase temperatures.
* They form a porous ash, which allows oxygen to pass through, but reduces heat losses by conduction and radiation.
* They have lower thermal conductivity and specific heat than graphite.

In fact, because graphite is so resistant to oxidation, it has been identified as a fire extinguishing material for highly reactive metals.

Thus the issue of graphite fires is open to question, and should be most properly settled by scientific investigation. The New Scientist published a discussion of the General Atomic claim in its November 4. 1989 edition. The New Scientist came to a graphite does burn reluctantly, and is not very dangerous view, pointing to research by Peter Kroeger's of Brookhaven National Laboratory for support. I concluded my initial investigation of the graphite fire danger by noting

Needless to say, Ed Lyman forgot to mention any of Peter Kroeger's research, the General Atomic's argument, or other arguments that makes his simple "Graphite burns" statement less than a serious inditement of pebble bed reactor safety.

Even less so, does the "graphite burns" statement a serious safety objection to the use of graphite in the core of Molten Salt Reactors. It should be noted that the presence of liquid fluoride salts would be a serious inhibitor of any graphite fire, and in the event of salt drainage from a MSR core, a graphite fire would not be a safety issue, because both fission products and nuclear fuel would drain out of the core along with the coolant salt. Thus even if we reject the General Atomic's contention that Nuclear Graphite does not burn, the graphite burns objection does not appear to raise a serious concern about Molten Salt Reactor safety.

My conclusions were based on facts - Peter Kroeger's graphite research, and the application of logic to those facts. Anyone wishing to disagree with my conclusions should either argue that I misrepresented Kroeger's research, or Kroeger's research was seriously flawed, or that I committed logical errors in reaching my conclusions. So far no one has used any of these rational approaches to dispute my claims.

My discovery of Kroeger's research was not the end of the line as fare as my investigation of the graphite fire risk. I had two supposed reactor graphite fire risks to explain. The Windscape fire, and the Chernobyl fire.

DA Ryan asserts

CB (Charles Barton) seem unable to absorb any information that contradicts their position.

What information? Ryan presents no facts, no analysis of logic which contradicts my views. Ryan's evidence is not based on research. In facts Ryan ignores all nuclear graphite fire risk research.

When I pointed out to Ryan a recent statement on the Windscale fire by the UK Nuclear Safety Advisory Committee that,

Inspections have shown that there was NOT a graphite fire: damage to graphite, caused by severely overheated fuel assemblies, was localised.

Ryan remarked,

the paper you point to with regard to Winscape is the minutes of a committiee meeting not an official statement or scientific anaylsis that has been subject to peer review. One could be unkind and describe it as “gossip”.

Yet the UK Nuclear Safety Advisory Committee reports the results of acrtual observations. None of the statements about the Windscape fire which Ryan refers to is based on evidence drawn from actual observation inside the core of the Windscape reactor. I went to the trouble of documenting several accounts of the Windscaple accident in0rder to show that the evidence in support of the UK Nuclear Safety Advisory Committee report has long been known, and that evidence includes photographs taken from inside the windscape reactor, and a link to a presentation by M.T. Cross, at the Brookhaven National Laboratory Graphite Research Reactor Workshop, May 9-10 2007. The presentation included numerous slides of photographs taken in the interior of the Windscape reactor that shows fuel capsules that were damaged or destroyed by fire, while the graphite structures that contain them are still intact. I wonder if Mr. Ryan would also categorize those photographs as "gossip."

If Mr. Ryan still can maintain his "Windscape was a graphite fire" position with a straight face, he must explain the miracle of the Windscape graphite, the graphite burned but was not consumed, just like Moses burning bush.

Mr. Ryan accuses me of ignoring the precaitionary principle, but he has managed to stumble very badly in his attempt to establish that there is a MSR core graphite fire risk. Ryan has posted a long response to my critique of his treatment of MSR technology, and to Bill Hannehan's critique. The first of Ryan's comments has to do with graphite fire. Ryan states:

Another critique of my critique of the LFTR can be found here:
http://nucleargreen.blogspot.com/2011/08/d-ryan-msrlftr-critique-not-ready-for.html
As with the previous ones they either deliberately missread my critique in an effort to build up stray man arguments or reading just isn’t one of Mr Bill Hannahan, or “Rank Amateur” (his words http://daryanenergyblog.wordpress.com/ca/#comment-126) Charles Barton’s stronger points. I’ll leave it to the reader to decide which.

Firstly, they misrepresent my views on graphite, which I point out is a “perceived fire risk” I was never suggesting it will catch fire if you put a match to it. I make this point repeatedly in the comments above, I even added a little section to chapter 6 to describe the two sides of the fire risk argument and clarify my position. But the fact opaque minds of BH and CB seem unable to absorb any information that contradicts their position. They also seem to have no idea about the concept of scientific uncertainty or the precautionary principle or the most basic concepts of how passive safety is guaranteed. These would require “some” action be taken on this issue. Indeed they compound there mistake by then misunderstanding why graphite is used in Class D fire extinguishers (for liquid metals!). Oh, and BH suggests you can use jet fuel to put out fires later on (yes really!). I’ll let the reader assess the practicalities of that!

Ryan starts off with a straw man argument, that is the suggestion that we were attributing to him the view that graphite

will catch fire if you put a match to it.

I never attributed that with to Ryan, and he, of course, can produce no quotes that say otherwise.

I do view Ryan's claims about about the fire risks posed by graphite cores in MSRs are at best exaggerations. Research on Graphite safety conducted in the United States after the Chernobyl nuclear accident, found that graphite was a safe material for nuclear cores, and that it posed little or no fire danger. I argued this because my own review of literature on graphite fire danger demonstrated that graphite posed no fire risks for Molten Salt Reactors. Mr. Ryan has not presented research evidence contradicting my conclusions.

Ryan attempts to discredit me by claiming that the word "perceived" in the phrase "perceived fire risk" some how invalidates our arguments against his position. In fact the word perceived has more than one meaning. It can be understood to mean, "detected by instinct or inference rather than by recognized perceptual cues," or it can mean, "detected by means of the senses." These two meanings are somewhat contradictory which makes the word "perceived"an excellent weasel word. Before we look further at what Mr. Ruan means when he uses the word "perceived," we ought first to look at what Ryan actually says about graphite and graphite fire risks. In his original essay, Ryan writes,

Another issue is that graphite core. As I detailed previously with regard to the HTGR (part 6.4.3) it’s a potential fire hazard. Thus we would need to put the MSR within a containment dome of sorts. Again, as with the HTGR, this dome need not be built to the same exacting standards of a LWR dome as we are merely trying to contain a graphite fire, not an out of control reactor.

The word perceived certainly does not decrease Mr. Ryan's certainty about the necessity of taking steps to control graphite fire risk. In addition to structural recommendations,

We would need an effective on plant fire control team and some form of fire detection and suppression system, within the containment dome and all the necessary gear that this entails. Again, I refer you the relevant section of the HTGR analysis, but needless to say such an arrangement would involve certain costs.

So Mr Ryan seems to mean by perceived fire risk, a plausible risk of graphite fire. But is there plausible risk of graphite fire in MSRs? Graphite fire research seems to show that there is none Ryan ignored that research when he made the graphite fire claims.

I argued that the evidence on graphite fire risks suggests that there are no circumstances in which the laws of nature would allow us to believe that a graphite core of a Molten Salt Reactor could catch on fire. If an idea contradicts the laws of nature, it is a misperception, a mistake, or a miracle. Mr. Ryan should have explained how the graphite core of a molten salt reactor could catch on fire despite the fact that a graphite fire in A MSR core would seemingly violate the laws of nature. Apparently Mr. Ryan's precautionary principle includes protecting the public from miracles.

Mr. Ryan fails to not the difference between assertion as rhetorical strategies, and actually demonstrating his case. Ryan acknowledges,

I could go thro this line by line but there’s no point, all they succeed in doing is demonstrating their own ignorance of the facts and inability to absorb any information that contradicts the LFTR gospel.

Ryan however, fails time after time to demonstrate that Bill and I are as ignorant as he says we are. He tells us that Bill is mistaken in asserting at low vapor pressure of MSRs is an advantage because,

The pressurization issue is a bit of red herring, the major materials stumbling block is the issue of the combination of corrosive attack under temperature, with a bit of radiation thrown in for good measure.

In this argument Ryan simply ignores ORNL finding from the MSRE. ORNL-TM-4171 (Postirradiation Examination of Materials from the Molten Salt Reactor Experiment ) reported that

The MoltenSalt Reactor Experiment operated very successfully. The fuel loop was above 500°C for 30,807 hr and contained fuel salt for 21,040 hr. A surveillance program was active during operation to follow the property changes of the graphite moderator and the INOR-8 structural material. After operation was discontinued in December 1969, several components were removed for examination. These included a graphite moderator element from the core, a control rod thimble, freeze valve 105, the sample cage and mist shield from the fuel salt pump bowl, a copper sampler capsule, tubes and a portion of the shell of the primary heat exchanger, and tubes and two thermocouple wells from the air-cooled radiator.

The overall findings were that

Examination of these materials showed excellent mutual chemical compatibility between the salts, graphite, and INOR-8. The INOR-8 exposed to fuel salt formed shallow intergranular cracks believed to be due to the ingress of the fission product tellurium. The INOR-8 was also embrittled by exposure to thermal neutrons, and this was attributed to the formation of helium by the (10)B(n,a)(7)Li transmutation.

The ORNL report found that

The primary corrosion mechanism in the fuel salt system was selective removal of chromium by 2UF4 + Cr(in alloy) Z+ 2UF3 + CrF& salt), and the concentration of chomium in salt samples was the primary indicator of corrosion. . . . The total increase in chromium in the 4700-kg charge of fuel salt is equivalent to leaching all of the chromium from the 852 ft2 of INOR-8 exposed to fuel salt to a depth of about 0.4 mil.

Since the coolant salt did not contain uranium, the corrosion rate was extremely low. During operation, the chromium content of the coolant salt remained at 32 ppm, within the accuracy of the analysis.

ORNL scientists went on to identify two solutions to the intergranular cracking problem, and proposed to solve the minor chromium corrosion problem by removing chromium from metal alloys. Mr. Ryan failed to examine the results of the ORNL experiment that was designed to determine the effects of

the combination of corrosive attack under temperature, with a bit of radiation thrown in for good measure.

Those findings were that there were some developmental problems, but none that were show stoppers.

One way to avoid mistakes due to ignorance in scientific matters is to pay careful attention to what scientists say in research related documents, and to quote them exactly and in context. This would be the approach that both Bill and I take, but Mr. Ryan does not seem to regard it as necessary to examine the actual research before he makes sweeping and all encompassing judgements on all sorts of matters. Thus his pronouncements on MSR related problems are invariably made without reference to ORNL research work product, which would be the primary source of information on MSR research.

Most of Mr. Ryan's response is an personal attack on Bill and I have left it to Bill has answer those criticisms.

DA Ryan's attack on Bill Hannahan and Bill's Response

DA Ryan has recently posted a number of responses to Bill Hannahan's latest Nuclear Green post. Ryan wrote:

Another critique of my critique of the LFTR can be found here:
http://nucleargreen.blogspot.com/2011/08/d-ryan-msrlftr-critique-not-ready-for.html
As with the previous ones they either deliberately miss-read my critique in an effort to build up straw man arguments or reading just isn’t one of Mr Bill Hannahan, or “Rank Amateur” (his words http://daryanenergyblog.wordpress.com/ca/#comment-126) Charles Barton’s stronger points. I’ll leave it to the reader to decide which.

Firstly, they misrepresent my views on graphite, which I point out is a “perceived fire risk” I was never suggesting it will catch fire if you put a match to it. I make this point repeatedly in the comments above, I even added a little section to chapter 6 to describe the two sides of the fire risk argument and clarify my position.
http://daryanenergyblog.wordpress.com/ca/part-6_htgr/6-4-3-fire-risk-and-mitigation/
But the fact opaque minds of BH and CB seem unable to absorb any information that contradicts their position. They also seem to have no idea about the concept of scientific uncertainty or the precautionary principle or the most basic concepts of how passive safety is guaranteed. These would require “some” action be taken on this issue.
http://daryanenergyblog.wordpress.com/2011/07/31/the-precautionary-principle/
Indeed they compound there mistake by then misunderstanding why graphite is used in Class D fire extinguishers (for liquid metals!). Oh, and later on BH suggests you can use jet fuel to put out fires (yes really!). I’ll let the reader assess the practicalities of that!

I could go thro this line by line but there’s no point, all they succeed in doing is demonstrating their own ignorance of the facts and inability to absorb any information that contradicts the LFTR gospel.

“the author counters his own point” no I don’t! I was just trying to give a fair and balanced assessment, but don’t let facts get in the way of a good hatchet job.

“low vapour pressure” The pressurization issue is a bit of red herring, the major materials stumbling block is the issue of the combination of corrosive attack under temperature, with a bit of radiation thrown in for good measure. The low vapour pressure solves some problems but creates others due to the difficult it creates in getting decent thermal efficiency and that it increases the risk of intrusion of outside air (unless you surround the reactor in a inert gas Caladaria, but that would be pricy and “complicate things”).

“MS in solar energy” – BH doesn’t seem to understand that solar thermal plants are a different kettle of fish, different salt mixtures, temperatures and pressures and most importantly no radioactive thorium suspended within.

BH then goes into a detour unrelated to the article, but which came up in discussion, regarding his fantasy’s of removing uranium from sea water. This has been refuted by several peer reviewed papers (Barti 2007 and Barti etal 2011, Dittmar 2011) claiming that such a process would likely yield less energy back than it returned. Such proposals also ignore certain practicalities. Barti suggests http://www.theoildrum.com/node/4558 that we would have to cover the whole of North Sea with Uranium adsorption structures in order to get enough uranium for just 16% of the present world’s electric power production. Dittmar suggests http://greatchange.org/ov-dittmar,nuclear_option_ASPO.pdf that you would need to capture and filter the flow of 5 times that of the Rhine river to run just one nuclear power station, so clearly impractical! Of course building a dam and using such a flow for hydroelectricity would yield substantially more energy as would covering a small patch of the North Sea in wave energy machines. BH seems unable to absorb these facts. It was repeatedly pointed out to him in this discussion above and Barti and others in the blog he links to as well. BH seems to declare “victory” of sorts here on the fact that Barti gave up trying to get the message across (I don’t blame him!). Indeed if you view that blog string you’ll see even several pro-nuke bloggers running out of patience with BH one describing him as a “propagandist” http://europe.theoildrum.com/node/4558#comment-415499. He seems to think that just because everyone else left him mumbling to himself that counts as victory.

BH also brings up Radon (or does he mean Roswell? ;0) that’s not in my article, but in the discussion here and I rebutted his point but typically he ignored it. Oh well, I did try!
http://daryanenergyblog.wordpress.com/ca/#comment-135

“Publishing a quip that you know is misleading and prejudicial is unethical”…no it’s a quip, an amusing comment, you know? A joke! I know Americans lack our British sense of humour, but how old are you? grow up!

He then goes into a discussion about the CPP, making various stabs at it, that basically just confirms my worst fears (yet again) the LFTR fans have no idea how efficient this system will be, how to design it or what its implications to reactor operations are. Later he very wisely jettisons the idea, at least temporarily until the reactor is proven.

Indeed as part of this effort he also throws out Thorium, Air based cooling, the CPP, open cycle operation, small exclusion zones, baby, bath water and pram go flying over the side in a desperate fit of back peddling. Of course this puts his post in direct contradiction to the infamous wired mag article (which specifically highlighted the lack of large exclusion zones and Thorium as key positives of the MSR). Shall they be calling Wired asking for a retraction of these points? or indeed alter they’re own websites and all of those LFTR videos doing the rounds (and at this rate if BH keeps it up those 2 hr vids will be down to “hello” and “goodbye”) to reflect this new position? Well of course not! Who said we should let facts getting the way of a good techno fantasy!

Finally BH arrives at a point with a reactor design, not far removed from the Micro-fuji proposal, one that I acknowledged (8.12) had an air of plausibility surrounding it (of course he ignores this fact also). However BH neglects to point out the crucial arguments I made regarding cost. It’s clear that the MF will be rather expensive, far more so than any other reactor prototype of recent years and its difficult to avoid the argument that a follow on commercial unit will still be more expensive than existing LWR or HTGR technology. Given that we jettisoned all of the bits of the MSR that gave it its unique selling point, why would anyone invest in such an endeavor? You want cheap nuclear (relatively speaking!)? Use LWR’s. Want to burn Thorium? Use HTGR’s. Want cheap(ish) energy with no nuclear waste? We have renewables. We could add back in those bits of the MSR BH threw away, but that would greatly increase our R&D costs as well as the development time scale and increase the risk of the whole project failing.

He tries to counter my point about load cycling by quoting figures from the, as of yet untested, AP1000. He ignores the fact that the grid can see sudden changes in the order of GW’s per second, I believe it hits about a 2-4 GW swing (in a few seconds) here in the UK when a popular soap ends. While I acknowledge that newer reactors like the AP1000 should offer much greater flexibility than past reactors (but that’s unproven as no AP1000 reactor has yet been commissioned), they certainly don’t close the circle and a LFTR would be a very different beast (if he’d bothered to read my article), so it’s not a relevant comparison.

Also BH tries to disprove the well known toxicity of fluorine. He presents figures showing that fluorine (it doesn’t specify in which form) has a lethal dose (to a rat) of 300 mg (sounds pretty deadly to me!) and Chlorine at 4 times higher, with him then claiming that in fact it’s the other way around (i.e. the numbers suggest that Flourine is more deadly as it has a smaller lethal dose)…?…Also I would note that there’s a very big difference between both substances in various chemical forms or in the form of an easily inhaled gas, hence why people don’t keel over when brushing ones teeth!

I could go on, but its pointless. As I’ve shown, many LFTR fans see the world thro rose tinted glasses. They only absorb facts that support their technofantasy, can’t see the contradictions in they’re own arguments and assume any criticism is the work of Satan and it must be exorcised at once least the flock here of such heresy. Anyone who criticizes there views is either misinformed (even if he’s a respected nuclear scientist) or “one of them”…which brings us onto…
…Ad Homein comments? Pot calling the kettle black me thinks. Its strange that this is the opener from CB last time around (i.e. claim that I’m baised) and that the primary tool of LFTR fans is to attack the person and not the facts (as I think we’ve learnt most of them are “Rank amateurs”). Look at this rebuttal of the ecologist magazine article here: http://energyfromthorium.com/rees-article-rebuttal/. Almost all the various “rebuttals” of my critique online soon lurch into the form of personal attacks that question my credentials.

I intend to post my own response to Ryan's comments, but Bill has beaten me to the punch.

From Bill Hannahan: My response to Ryan’s comment. http://daryanenergyblog.wordpress.com/ca/#comment-220

“Firstly, they misrepresent my views on graphite, which I point out is a “perceived fire risk” I was never suggesting it will catch fire if you put a match to it.”

A small sliver of coal can be ignited with a match.

“we cannot conclusively conclude that there is no fire risk (as some mistakenly do), particularly given the evidence from Chernobyl.”

The Chernobyl reactor is as different from an MSR as the F-104 Starfighter is different from a Boeing 747. If someone used the F-104 accident rate as a reason to prevent the R&D of new improved airliners would you consider that a good argument?

“any ideas we have about building HTGR’s without containment domes”

First, no nuclear power plants are going to be built without containment. Second, chapter 8 is about MSR's, which have liquid fuel, making the fire analysis much different than for a solid fueled HTGR.

“BH suggests you can use jet fuel to put out fires (yes really!). I’ll let the reader assess the practicalities of that!”

Actually I showed that the temperature of burning jet fuel is lower than the normal operating temperature of an MSR, so jet fuel could be used to cool a MSR. Furthermore if you somehow induced a pile of nuclear grade graphite to burn, spraying it with jet fuel would lower its temperature well below the ignition temperature, putting out the graphite fire, and once all the residual jet fuel burns up the fire would stay out if there is no other source of heat to re-raise the temperature of the graphite.

I never claimed that real MSR plants will keep large storage tanks of jet fuel for use in response to a fire. The point of the example is to illustrate the fact that machines designed for very high temperature operation are easier to cool than machines made of low temperature materials. R avoids addressing this key technical point by deflecting with ridicule and misdirection.

“I could go thro this line by line but there’s no point”

Please do, your vague generalities and irrelevant references leave your case unsupported.

“the major materials stumbling block is the issue of the combination of corrosive attack under temperature, with a bit of radiation thrown in for good measure.”

Which is why I support building several small experimental plants of promising designs using the best materials available to get the needed performance data.

“The low vapour pressure solves some problems but creates others due to the difficult it creates in getting decent thermal efficiency and that it increases the risk of intrusion of outside air”

Here R is just making stuff up. If the salt had a lower boiling point it would have to be pressurized and that would somehow raise thermal efficiency? Nonsense.

“BH doesn’t seem to understand that solar thermal plants are a different kettle of fish”

I understand that solar thermal plants will be very large, expensive, use large quantities of land, concrete, steel and salt, and have only a few hours of storage, with a limited capacity factor, especially during periods of bad weather. But my recommendation, R’s, is to push R&D in all potential sources of energy, including solar, as hard as possible.

http://www.theoildrum.com/node/7275#comment-755200

“BH then goes into a detour unrelated to the article, but which came up in discussion, regarding his fantasy’s of removing uranium from sea water.”

No doubt in 1902 some people were chiding the Wright Brothers for pursuing their fantasy of flight.

“Dittmar suggests http://greatchange.org/ov-dittmar,nuclear_option_ASPO.pdf that you would need to capture and filter the flow of 5 times that of the Rhine river to run just one nuclear power station, so clearly impractical!”

Dittmar could prove that the tuna industry is uneconomical by calculating how much sea water you would have to pump through a tuna extraction plant to fill a 5 ounce can. Obviously a real uranium extraction process would take advantage of ocean currents. Dittmar’s predictions have proven largely wrong so far.

http://nextbigfuture.com/?cx=partner-pub-2647001505857353%3A7695799466&cof=FORID%3A10&ie=UTF-8&q=dittmar&sa=Search&siteurl=nextbigfuture.com%2F#1402

“Barti suggests http://www.theoildrum.com/node/4558 that we would have to cover the whole of North Sea with Uranium adsorption structures in order to get enough uranium for just 16% of the present world’s electric power production.”

As I said before, seawater uranium does not have to supply all our uranium to guarantee a price under $200 per pound, it only has to replace the conventional portion that is over that price, which is zero in the foreseeable future.

More importantly, our pre Model T reactors only split about 1% of the uranium atoms mined to fuel them. A fast Breeder reactor would only need about six pounds of uranium per day. It could get that from the sea water used to cool its condenser.

“we’re not “destroying” radioactive material in a reactor, we’re merely transmuting it from one form to another and were still left with a large pile of “nasty stuff” sitting in a storage container which we now have to either re-bury or baby sit for a few millennia.
So all in all I’d argue uranium mining causes as many (if not more) problems than it solves.”

Show us your references and calculations, deaths, brain damage, respiratory illness for uranium vs. fossil fuel, or you could study this report.

http://theenergycollective.com/karenstreet/63318/earthquake-tsunami-and-nuclear-power-japan

““publishing a quip that you know is misleading and prejudicial is unethical”…no it’s a quip, an amusing comment, you know?

What other forms of disinformation do you believe are ethical?

“It’s clear that the MF will be rather expensive, far more so than any other reactor prototype of recent years and its difficult to avoid the argument that a follow on commercial unit will still be more expensive than existing LWR or HTGR technology.”

The first handful of Chevy Volt’s cost GM several millions of dollars, and the first MSR's will cost more than conventional plants. What will #100 cost? What will #1000 cost?

Given their compact size and reduced material requirements factory mass production of major components and modules becomes possible leading to big cost and time savings.

“He tries to counter my point about load cycling by quoting figures from the, as of yet untested, AP1000. He ignores the fact that the grid can see sudden changes in the order of GW’s per second, I believe it hits about a 2-4 GW swing (in a few seconds) here in the UK when a popular soap ends.”

And what is that as a percentage of total power? Split that 2-4 GW between hundreds of power plants and it is not a problem. How do you think they handle it now?

“While I acknowledge that newer reactors like the AP1000 should offer much greater flexibility than past reactors (but that’s unproven as no AP1000 reactor has yet been commissioned), they certainly don’t close the circle and a LFTR would be a very different beast (if he’d bothered to read my article), so it’s not a relevant comparison.”

Actually, I cited the AP 1000 performance in response to the authors claim that “existing nuclear stations are capable of some level of power cycling anyway just not much!”

When Boeing and Airbus design a new aircraft, they usually perform within a few percent of the design point by the end of the development process. Does R suggest that the AP 1000 design is so slipshod that it could be off by a large margin?

It is interesting that R can draw damming conclusions about future MSR's based on the totally different 60 year old Windscale reactor design, but the AP 1000 is off limits.

The most important thing is that for the first few decades MSR's will be run continuously at 100% because their fuel cost will be lower than any fossil plant and lower than the fuel cost for most other nuclear plant designs. MSR's will not have to load follow until the grid is almost all nuclear powered.

“BH tries to disprove the well known toxicity of fluorine. He presents figures showing that fluorine (it doesn’t specify in which form) has a lethal dose (to a rat) of 290 mg”

Here is a cut and paste of the section R is referring to;

{ “Fluorine gas is extremely toxic (several times more deadly than chlorine”

Toxicity Data, Fluorine
LC50 inhal (rat)
185 ppm (300 mg/m3; 1 h)

Toxicity Data, Chlorine
LC50 inhal (rat)
293 ppm (879 mg/m3; 1 h)

http://www.nap.edu/openbook.php?record_id=4911&page=320

By volume fluorine is less than twice as toxic as chlorine. The U.S. consumes ten billion kg of chlorine each year; enough to kill every man woman and child in the U.S. every 45 minutes. Essentially all of that is manufactured and consumed under conditions less secure than those inside a reactor containment building.}

R claims it does not specify the form, but anyone familiar with toxicity data would know it is for elemental gas. R claims I said the lethal dose is 290 mg, but as you see, the units are mg/m3, and the number is 300.

R goes on to say;

“(sounds pretty deadly to me!) and Chlorine at 4 times higher, with him then claiming that in fact it’s the other way around”

So lets do the math for R; 293/185 = 1.58 which is less than 2 by VOLUME as I specified.

R tries to prove me wrong by doing a MASS calculation, but he gets that wrong too. 879/300 = 2.9 which is less than 4 and less than “several times”.

R’s focus on insults and silliness, his failure to engage on the important points and his amazingly high error rate shows the weakness of his position. Here are key questions and issues from my review comment that he has not addressed.

1. Our cheapest fossil fuel is coal. To generate an 80 year lifetime supply of electricity for one person in the U.S. with coal we burn 1,140,000 pounds of coal, producing 2,440,000 pounds of CO2 and thousands of pounds of toxic waste, much of it released into the atmosphere. Lifetime fuel cost with coal is $34,000, $424/year.

The simplest uranium burning MSR will need about 12 pounds of uranium to make a lifetime supply of electricity. What would the price of uranium have to be to make MSR fuel more expensive than coal per kWh?

LFTR will need six ounces of thorium to make a lifetime supply of electricity. What would the price of thorium have to be to make LFTR fuel more expensive than coal per kWh?

2. MSR's can be designed to operate without graphite. Do you support R&D of those designs?

3. The Windscale reactor had large fans blowing air through the core. How could a large flow of air pass through a MSR reactor vessel?

3a. What is the driving source of pressure gradient?

3b. How are the required holes created in the reactor vessel and containment walls?

3c. At Windscale and Chernobyl the solid fuel, moving air and graphite were in direct contact. In a MSR, the graphite is normally submerged in salt. Can graphite burn while submerged in salt?

3d. When solid fuel melts it can release a large burst of volatile fission products acumulated over a period of months or years. MSR's do not accumulate volatile fission products.

Do you acknowledge that MSR's will not contain a large mass of volatile fission products that can be released in an accident? If you disagree, what is the concentration, chemical composition, melting point, boiling point of the fission products that would be problematic in a MSR accident? Compare those numbers with the numbers for solid fuel reactors. Why don’t these highly volatile compounds come out of solution during Normal operation?

3e. If the graphite is exposed to air, most fission products are below the liquid line in a chemical form that is stable at very high temperature. How would the graphite burning in air volatilize a large quantity of low volatility fission product compounds in the salt below the fire or in a remote tank?

4. The only nuclear accidents to release large quantities of fission products are those where a direct path to the atmosphere is provided by design or by explosion. MSR's have continuous online refueling. There is only enough reactivity for normal operation. I do not know of any way to make an MSR explode. Do you, explain the mechanism in detail?

5. It is interesting that out of hundreds of fission products, only a few of the most volatile constitute most of the risk in solid fuel reactors.

Cesium is by far the most problematic long term fission product in an accident. It melts at 28C, the boiling point is 671 C. When a cesium atom is produced in a MSR it immediately hooks up with a fluorine atom to make cesium fluoride, melting point 682C, boiling point 1251 C, so it has much lower volatility resulting in greatly reduced emissions under accident conditions. Very little cesium will be released in a MSR accident. Provide detailed mechanism if you disagree?

By the way R. I am sure you can post your comments on Charles Barton’s blog, he does not engage in censorship as you do.

The D A Ryan MSR/LFTR critique: Not ready for Prime Time

A blogging engineer named D A Ryan has recently written a critique of Molten Salt Reactor/LFTR/thorium nuclear technology that is decidedly a mixed bag. Most of the comments land off the mark, some seem to wonder away from reality. Many comments in the Energy from Thorium Comment Forum can be taken as critiques of MSR/LFTR technology. Any serious attempt to criticize MSR technology should review the technical discussions on EfT, before making an assessment of molten salt technology. This is quite a chore, but familiarity with the subject is a requirement of serious criticism. While Ryan is familiar with EfT, he has not gone to the trouble of checking out his criticisms with the EfT discussion forum. Ryan then is not a serious critic of nuclear power, but that is not his point. Ryan's conclusion is actually his starting point,

clearly, as regards the current discussion, we cannot run the world on nuclear energy; indeed we’d struggle to meet a tiny portion of global energy needs, for any prolonged period (and I mean a lot less that we currently manage!) with nuclear power, neither generation IV reactors, nor Thorium, nor even Fusion power will help much on this point. Even the most optimistic nuclear energy program we can realistically conceive of still has a substantial energy gap that something else will have to fill. And given our limited fossil fuel supplies (long term at least) that inevitably means alot more renewable energy, which has to take priority over nuclear.

Does Ryan reach this conclusion by sound reasoning, or dies he misrepresent facts, and engage in fallacious arguments? We need go no further than this comment to realize how dubious Ryan's enterprise is,

Another issue is that graphite core. I detailed previously with regard to the HTGR (part 6.4.3) it’s a fire hazard, i.e. Graphite is basically ultra high grade coal! Thus we would need to put the MSR within a containment dome of sorts. Again, as with the HTGR, this dome need not be built to the same exacting standards of a LWR dome as we are merely trying to contain a graphite fire, not an out of control reactor. We would need an effective on plant fire control team and some form of fire detection and suppression system, within the containment dome and all the necessary gear that this entails. I refer you the relevant section of the HTGR anaylsis, but needless to say such an arrangement would involve certain costs.

But is there a fire danger from Graphite? My regular readers might recall thata few months ago I looked at some questions related to the topic of graphite flammability and looked at the question, "Did the Graphite in the Windscale Reactor Burn?" My finding was,

When The UK Nuclear Safety Advisory Committee (NuSAC) meet in 2009 to examine evidence from the Windscale reactor, it found,

• Inspections have shown that there was NOT a graphite fire: damage to graphite, caused by severely overheated fuel assemblies, was localised.

In a third post, titled "Did Chernobyl Graphite Burn," I reviewed sections of a document prepaired for the Nuclear Regulatory Commission by Brookhaven National Laboratory, NUREG/CR-4981 "A Safety Assessment of the Use of Graphite in Nuclear Reactors Licensed by the U.S. NRC." NUREG/CR-4981 was a document intended to answer the question for the NRC. The Brookhaven researchers determined,

Experimental studies on graphite burning have shown that for all the geometries tested which Involved the conditions of small radiation and conduction heat losses, it was not possible to develop self-sustained rapid oxidation for graphite temperatures below about 650 C when the air temperatures were below the graphite temperature. At both high and low flow rates, the graphite was cooled by heat losses to the gas stream even under conditions where other heat loss mechanisms such as radiation and conduction were negligible.

At temperatures above about 650°C, in realistic geometries where radiation is a major heat loss mechanism, graphite will burn only in a limited range of flow rates of air and only when the air temperatures are high. At low flow rates, inadequate ingress of air restricts burning. At high flow rates, the rate of cooling by the flowing gas can exceed the rate of heat produced by oxidation.

Studies have shown that burning will not occur when there is no mechanism to raise the graphite temperature to about 650°C [Schweitzer, 1962a-f]. If the temperature is raised above 650°C, burning will not occur unless a flow pattern is maintained that provides enough air to sustain combustion but not enough to cause cooling. Since the experiments were designed to minimize all heat losses other than those associated with the air flow, 650°C can be considered a lower bound for burning. . . . . in order to have self-sustained rapid graphite oxidation in any of these reactors certain necessary conditions of geometry, temperature, oxygen supply, reaction product removal and favorable heat balance must exist.

The Soviets claimed and American nuclear safety experts like H.J.C Kouts accepted the notion that graphite could burn like charcoal.

The emission of radionuclide continued for about nine days, aided by burning of the graphite. It is estimated that upwards of ten percent of the graphite in the core burned, in a manner similar to the rapid oxidation of charcoal.

We know that Kouts view cannot be correct, nuclear graphite does not burn like charcoal, and the assertion that only 10% of the Chernobyl core graphite burned does not suggest graphite was the major source of the Chernobyl fire. There were, of course other materials in the Chernobyl reactor core that burned hot enough to oxidize nuclear graphite.

Both the NRC and a separate study commissioned by the United States Department of Energy determined that graphite reactor could be operated safely.

The NRC's answer to the original question which I asked at the beginning of this series is ";yes, graphite does burn" but only under a very limited set of conditions. Given this information it is quite possible to design a reactor in which those conditions will never occur.

Ryan references the wikipedia for his claim that "Graphite is basically ultra high grade coal!" What the Wikipedia actually says is,

Graphite may be considered the highest grade of coal, just above anthracite and alternatively called meta-anthracite, although it is not normally used as fuel because it is difficult to ignite.

Nuclear graphite is even more difficult to ignite than natural graphite. The wikipedia article on graphite also states,

during a fire, the graphite expands and chars to resist fire penetration and spread . . . .

What can I say? Here we have clear evidence of extremely shallow research or something worse. Ryan claims that

That big graphite core is a serious worry. As one nuclear physics put it to me “graphite is basically just high grade coal”. Obviously enough, building a nuclear reactor core out of coal doesn’t sound like a sensible idea! Its worth remembering that part of what made Chernobyl the disaster that it was, and why Fukushima is likely to have a much smaller level of fallout (despite 4 reactors involved, one fuelled with MOX against a single reactor at Chernobyl fuelled with only lightly enriched uranium) is because the graphite moderated core at Chernobyl caught fire. It was this fire and the smoke it generated that allowed the radioactive material from the core to spread over such a large area.

So clearly any FMEA process would zero in on this as a major issue that needs tackling. We need to take care in our design to make sure that any potential fire can be safely contained. Obviously this means that any ideas we have about building HTGR’s without containment domes, as some supporters of these reactors suggest we can (and indeed the UK’s AGR’s and Magnox reactors were also built without containment domes), wouldn’t be a good idea. I should note that the containment dome over a HTGR wouldn’t need to be build to the same exacting standards as one over a LWR as our goal is to contain a fire, not a melting down reactor core. This is important as it’s largely been the delays and difficulties in pouring concrete for these cores that is responsible for the messy cost overruns on the various new LWR reactor projects that are ongoing.

Our HTGR’s containment dome would need to be fitted out with some form of automatic fire detection and suppression system, specifically one that can cope with a high temperature graphite fire. As the Windscale power plant fire showed proper planning and equipment would be essential. At Windscale the initially attempt to put out the fire using CO2 failed, as the high temperatures of the fire simply stripped the oxygen from the CO2. The operators finally gambled and poured in water, knowing that this risked setting off an explosion, which fortunately didn’t happen. So clearly we’d need to be better prepared, an inert gas (Nitrogen, Argon or Xenon) or Halon gas should do the trick, if we have enough of it on site. I would note that a number of Halon’s have some potentially nasty environmental issues, such as being known carcinogens and mucking up the ozone layer, so inevitably storing a large quantity of them on site (never mind using them!) would have some environmental implications. Also, we don’t want to be relying, as at Chernobyl, on the local fire crew showing up and doing a Matrosov. Having a dedicated on-site fire crew covering the plant at all times (or nearby covering several plants in a geographical area), as is standard practice for airports, would be sensible. This fire crew, would be specifically trained in dealing with a high temperature graphite fire and be properly equipped to tackle such an event (i.e have working radiation suits! Unlike the situation at Chernobyl). These measures would close off this safety loop hole, but it will come with a cost.

But as we have seen Nuclear graphite is extremely difficult to ignite, and only burns when subject to heat of over 650 C, and then only if supplied with oxygen, and is not in contact with materials that are below 650 C.

Lets list some of Ryan's errors in this account:

1. He failed to note that the difference between the easy ignition of coal, and the ignition difficulties of graphite.

2. He ignores the mention in the wikipedia of graphite fire qualities.

3. His claim that a graphite fire was the primary cause of the Chernobyl radioisotope release is inconsistent with the evidence that 90% of the Chernobyl graphite did not burn, and the research that demonstrates that graphite does not burn in the absence of other heat sources and very hot air.

4. His claim that the Windscale accident included a major graphite fire is based on nothing more than old speculation that is now known to be untrue.

5. The word Chernobyl is used 6 times, Yet the basic premise of the Chernobyl discussion, "the graphite moderated core at Chernobyl caught fire" has been shown to be false. The relatively small amount of core graphite burning that toke place, had to be ignited by an external source and had to be continuously fed by a stream of very hot air.

6. The suggestion that HRGRs pose a fire danger is not supported by evidence.

7. The claim that HTGRs need containment domes is not on the invalid HTGR fire danger argument, thus is not supported by valid reasoning.

8. The argument regarding the supposed problems and costs related to containment dome concrete, is supported by an invalid chain of reasoning, and therefore is invalid itself.

In his account of the alleged graphite fire problems of MSRs, Ryan simply points to his invalid arguments related to the alleged HTGR graphite fire problem and then claims that MSRs will need specially trained fire fighting teams, special equipment, and a containment dome. All of this is hot air, because Ryan has not established reasonable grounds for believing that a MSR graphite fire problem exists.

Ryan criticizes both EfT and Nuclear Green,

Another misconception is that LFTR’s can be air-cooled (here and here) rather than being dependant on the water cooling process we utilise in most other power stations.

The Here and Here refer to one of my posts and a post by Kirk Sorensen.

How does Ryan justify this?

He claims,

Firstly, fire safety, air is an oxidising substance. Fires start all the time at power stations (fossil fuel fired and nuclear ones), especially in the turbine halls and the last thing we want in an emergency is a load of big cooling fans blasting in air and literally fanning the flames! In this scenario we’d face the dilemma between stopping the fans and cutting of the source of cooling (forcing us to SCRAM the reactor to prevent a LOCA scenario) or risk the fire spreading out of control, possibly to the point where it compromises the reactor’s safety. This was of course very similar to the dilemma faced during the Windscale fire, which was air cooled (although in this case directly, rather than indirectly as we currently discussing). And on the subject of Windscale, you will recall what I said earlier about fires and that Graphite core, so we’d be opening a very serious potential safety loophole.

But in nuclear plants, the turbine room is always separated from the reactor by a fire wall. The reference to the Windscle fire is simply confused. In the Windscale reactor air passed directly through the reactor core. There is no proposal to allow cooling air into the reactor core. Thus the Windscale analogy collapses and with it Ryan's first fire argument.

Ryan's second objection has to do with cooling fans

Cooling fans also aren’t terribly reliable, which is why the MSRE was down for several months due to a cooling fan failure. Air based cooling is also very weather dependant, indeed I note that the fans at the MSRE seems to have failed in the summer, when they would have likely been struggling to cope with higher daytime temperatures.

If cooling fans are unreliable, we can use a stack effect to accomplish passive air cooling. The reference to the MSRE cooling fan failure refers to a single incident early in the multiyear MSR test. Once the problems with the cooling fan were identified and corrected, the fan ran for something like 20,000 hours without a problem. The observations about summer related problems is bogus.

Finally we have a third argument

Thirdly, it’s the matter of thermal efficiency. Air based cooling is not very efficient, largely because air has such a low heat capacity compared to water (1.15 against 4.2 J/kg K). A typical COP (Co-efficient of Performance) for fans would be of the order of 2 – 3.7, while you can get 5 – 7.5 with water based cooling. Assuming a COP of 3 (it would be more like 2.5 at the temperatures in question, but bear with me!) and assuming a 1,000 MWth LFTR with a thermal efficiency of 50% (to keep my numbers easy!) = 500 MWe. Our cooling fans, in order to dispose of that 500 MW’s of excess heat, would be consuming 166.67 MW of electricity, dropping our effective plant efficiency down to 33%, barely Rankine cycle levels! This is why we use water in most power stations for cooling.

This argument is preposterous. The B&W mPower reactor is designed to be either air or water cooled. The air cooled mPower is rated at 125 MWe, while the water cooled mPower is reportedly rated at 136 MW, but officially described as a 125 MW reactor.. Thus the active air cooling system at worst consumes 11 MWs more electricity than the water cooling system does. We could probably expect even better performance is we use a stack effect based cooling system.

Ryan adds a further argument:

Also this air based cooling argument strikes me as a bit of a red herring, LFTR fans essentially inventing reasons why their “precious” is better than anything else. With the exception of a few geothermal power stations in arid areas (or hydroelectric plants!), I’m unaware of any major power project that was derailed for lack of cooling water. Either you can use cooling towers (forced draught or natural convection types) and minimise water losses to an acceptable level or simply move the plant next to a ready water source and transmit the power to where it is needed. Many desert countries operate large thermal power stations from around the coasts and several such as Iran, UAE and Libya are even planning to build nuclear stations too. So I fail to see how “air based” cooling offers any real benefits.

In fact water based cooling is usually considered by engineers to offer more thermal efficiency but the fact that Ryan is unaware does not mean consideration is not being given. In fact, as I have indicated, plans for an air cooled mPower reactor are moving forward, and plans for large air cooled solar thermal power plants are being considered in the Southwestern United States.

In addition this passage suggests an attack on Kirk Sorensen and myself for our enthusiasm about Molten Salt nuclear technology. The use of the word “precious” is highly inappropriate, and the use of the quotation marks would untruthfully attribute the word to us. Neither Kirk nor I have used the term “precious” to refer to the LFTR or MSR technology.

Furthermore, Ryan makes other attacks on LFTR/MSR supporters. Ryan describe us

the LFTR fanatics need to come off the Kool-Aid. I’ve gone to great lengths to debunk many of their crazy ideas because such cargo cult science as they are promoting does a great disservice to science, and gets in the way of more realistic and practical proposals. They also serve to confuse the public, and I mean even Wired News appears to have been taken in by this con, which makes the whole job of real scientists pursing real projects, all that harder. As I’ve shown many of the supposed advantages of the LFTR are simply figments of certain bloggers overactive imaginations. The fact that many of the LFTR supporters are Libertarians, individuals not entirely known for their grasp of basic physics, economics or social norms doesn’t help matters

This amounts to little more than a string of attacks on the character of LFTR supporters. The mention of Libertarians is especially silly. LFTR supporters come from the extreme right the extreme left and everywhere in between. The chinese communists who recently decided to invest in LFTR R&D are certainly not Libertarians. Nor am I. We regard MSR technology as promising, and even very promising, but that does not make us cargo cult scientists. The foundational ideas for the LFTR came from Eugene Wigner and Alvin Weinberg, who both were major figures in history of reactor science. LFTR supporters continue to look critically at alternative MSR technologies. The discussion pages of EfT are filled with debate on numerous MSR technology related topics.

In addition to my critique, the blogger uvdiv offers us a

Summary of some of the biggest howlers

* Claims MSRs have "Isotope Separation Plants" which separate 233U and 232U (the trace contaminant)
* Warns of hazardous fission products, such as thorium isotope "T-232" [sic], which supposedly is a disadvantage of thorium-fuelled reactors because of its 14 billion year half-life
* Warns that electrolyzing nuclear fuel salts is energy-intensive
* Warns that heat inputs in fluoride reprocessing are energy-intensive
* Asserts that thorium MSRs are constrained to a lower temperature limit of 1,110 °C, the melting point of pure ThF4. Concludes MSRs must be built entirely from ceramics
* "Obviously, once we exhaust the world’s U-235 stockpiles, LFTR’s and any other Thorium fuelled reactors will cease to function."
* Argues against using molten fuel salt as a working fluid in a gas turbine

"Uvdiv suggest that Ryan holds a misconception that

He has the misconception that 233U/232U isotopic enrichment is necessary for MSR operation. Spends many paragraphs speculating on this imaginary thing, finally concluding it will consume up to 25% of an MSR's electric output:

Uvdid find absurdities in Ryans accounts of fission products. Ryan quite literally describes Th-232 (Ryan calls it T-232) a fission product. Then uvdiv notes a strange error in Ryan's text,

The dendrite problem above demonstrates that the LFTR/LFUR has a relatively narrow thermal window. Its filtering plant will not work if the temperature of the fluid drops much below a certain threshold and the danger of fuel solidification raises the risk of the reactor being damaged. With UF4 the solidification temperature is 1,036 °C and its vapourisation temperature is 1,417 °C. [...] With TF4 our “window” is 1110 – 1,680 °C, but again we can potentially move this by lowering the pressure (or raising it if we want to go the other way…not that we do!). A low vapour pressure also creates a few potential problems in terms of keeping the reactor sealed (air is more likely to leak in if the pressure inside is less than atmospheric…possibly starting a fire!) and maintaining a good flow rate from our pumps.

Uvdiv then comments,

I don't know what confusion of his provoked this nonsense. Maybe he hasn't done his basic research, that all MSR proposals involve solvating actinide fluorides in other fluoride salts -- mixtures of LiF, NaF, BeF2, ZrF4, and/or others -- with the mixture having far lower melting points than actinide fluorides. Or maybe he's under the illusion that individual components of a chemical solution precipitate out at their pure melting points. At any rate, his chain of reasoning starts from this major error and leads to others:

Uvdiv then lists another chain of errors,

With the LFTR however, I doubt you could operate one made out of any Nickel alloy, contrary to everything said on the internet. Bare in mind I’m thinking in terms of a good lengthy service life with a sensible factor of safety, not a flimsy test reactor in a lab (with a 100 mile exclusion zone!).

[...]

Thus the pressure vessel of any LFTR would likely have to formed out of Ceramics (very expensive and difficult to form, especially given how critical getting an air tight seal is given the graphite core) and key internal components out of Refractory metals, as would be the case for certain high temperature parts of any ISP (in both the LFTR and LFUR cases) given talk of operating temperatures in the range of 1600 °C.

[...]

So my instinct from a materials science point of view would be to drop the LFTR idea altogether and focus instead on a LFUR. While this isn’t able to use the Thorium cycle, the point was raised earlier about how the Thorium cycle isn’t all its cracked up to be. Its going to be a lot easier to build a LFUR than a LFTR, cheaper (relatively speaking) and likely safer too. Of course it does come at the disadvantage of a slightly awkward acronym! but overall that would be my focus of attention.

We see once more Ryan's tendency to compound errors.

Uvdiv points to one Ryan error that did make me laugh out loud,

Another misconception is that a LFTR or LFUR can operate on an open cycle with a gas turbine. While true, it could be run this way, there are a host of practical reasons not to do it. Not least of them the fact that our turbine would have to be designed to withstand having a mixture of molten salt and fluorided fuel passed through it at very high temperatures. This would be tricky to say the least, likely requiring the use of those super expensive refractory metals, and while using such materials to make the odd turbine blade is one thing, an entire turbine casing is an entirely different matter. It would likely cost much more than the reactor itself!

Ryan confuses open cycle hear powered gas turbines, with fluoride salt turbines which indeed would be a difficult matter.

At this point I think we have enough. Further discussion and debate can be found here, and here.

I originally intended to write Good, Bad and Ugly critique of Ryan's essay on MSR/LFTR technology, but even the good is so tainted with the bad and the ugly that I find this impossible to do.

Are safer reactors possible?

Critics of nuclear power argue that all reactors are inherently dangerous, and point to nuclear accidents such as Three Mile Island, Chernobyl and Fukushima as evidence of the danger. The primary worry about nuclear power stems from the release of radioactive fission products, and other radioactive materials that are produced inside reactor cores. Among those materials Plutonium which is produced by a nuclear process which occurs when Uranium-235 and U-238 fail to fission following the absorption of neutrons inside reactor cores. Tritium a hydrogen isotope is also viewed with concern, although in practice tritium is viewed as so safe that it is used to illuminate the hands and dials of some wrist watches. The Nuclear Regulatory Commission (NRC) explains,

Tritium (H-3) is a weakly radioactive isotope of the element hydrogen that occurs both naturally and during the operation of nuclear power plants. Tritium has a half-life of 12.3 years and emits a weak beta particle. The most common form of tritium is in water, since tritium and normal hydrogen react with oxygen in the same way to form water. Tritium replaces one of the stable hydrogens in the water molecule, H2O, and creates tritiated water, which is colorless and odorless.

Tritium can be found in self-luminescent devices, such as exit signs in buildings, aircraft dials, gauges, luminous paints, and wristwatches. It is also used in life science research and in studies investigating the safety of potential new drugs.

In fact, if there were any significant danger from tritium, the NRC would outlaw using it in wrist watches. Just how dangerous is tritium? Recently a very small tritium leak from the Vermont Yankee power and was the subject of a big todo in Vermont. Nuclear critics insisted that the tritium represented a huge danger to the people of Vermont. The blog Minor Heresies suggested,

Tritium causes all the usual radiological effects: cancer, genetic defects, cell death, birth defects, and loss of fertility. . . .

My conclusion from all this is that the present tritium leak at Vermont Yankee is no small thing. The material is dangerous at low concentrations, persistent in the human body, impossible to filter, and hard to contain. The leak is limited to the area in and around the plant for now, but I can’t imagine the isolation and cleanup is going to be easy.

Well not exactly. Not in the amount we are talking about.

The silliness of the Vermont Yankee tritium scare was captured by a former Naval Officer who served in nuclear powered submarines, Rod Adams, who is currently a well regarded blogger on the uses of nuclear energy. Adams noted,

Based on reading a number of different articles and checking through the tables provided by the Vermont Department of Health, the fluid that was leaking into the ground contained tritium at a concentration of approximately 2.5 million picocuries per liter. That is equal to 2.5 x 10^-6 curies per liter. The rate that it was leaving the pipe was roughly 100 gallons (370 liters) per day. If the leak had been going on for a year before being detected and stopped, the total quantity of fluid that left the pipe would equal 138,000 liters. The total activity released would be 0.35 curies.

If a single person consumed every drop of that water, their whole body radiation dose would equal roughly 30 rem. According to a 1977 UNSCEAR study, the LD-50 (lethal dose for 50% of the population receiving the exposure) for tritium in adult rats was determined to be 1000 Rad. For the kind of low energy beta emissions that are produced by tritium, a rem is equal to a Rad. A dose of 30 rem received over a 1 year period would be unlikely to cause any immediate health effects, though it might add an additional risk of developing cancer sometime during the person's life. The magnitude of that risk could be computed using the conservative linear, no-threshold dose assumption.

Of course, a person who tried to drink 378 liters per day for a year would have problems more immediate the possibility of increasing their lifetime risk of cancer.

I also was asked to put this discharge into some kind of perspective, so I decided to compare it to the allowable and measured releases from a well operated and safe CANDU reactor in Ontario. Pickering B has a Derived Release Limit (DRL) for tritium of 490,000 terabecquerels each year. That is 4.9 x 10^17 Bq or 13 million curies.

Critics of nuclear power would insist that if we had a release of 13 million curies of tritium in the United States, we would have a crop of two headed babies. However, in Canada where 13 million curies annual releases of tritium are the norm, two headed babies are not being born.

On the other hand no one doubts that the escape of plutonium from a reactor can be a dangerous matter. Yet unlike tritium which is less dangerous than salt, but likely to escape from a reactor, Plutonium os very dangerous, but very unlikely to escape from a reactor. Nuclear critics love to recited how dangerous plutonium is. For example, journalist David McNeill stated

We might also cite the example of MOX fuel and plutonium, a substance so toxic “that a teaspoon-sized cube of it would suffice to kill 10 million people,”

In fact the Guardian reported,

In a possible sign that the contamination is more widespread than previously thought, a university researcher said at the weekend a small amount of plutonium had been identified a mile from the front gate of the Fukushima plant.

It is the first time plutonium thought to have originated from the complex has been detected in soil outside its grounds.

But was the escaped plutonium dangerous? The Guardian reportsed,

Masayoshi Yamamoto, a professor at Kanazawa University, said the level of plutonium in the sample was lower than average levels observed in Japan after nuclear weapons tests conducted overseas.

In conventional Light Water Reactors plutonium is produced inside fuel pellets. The fuel pellet is a ceramic and in almost every case the fuel plutonium will remain there. The only way the plutonium might escape the fuel pellet, would require that the reactor core overheat to such an extent that the ceramic fuel pellets start to melt. Once the plutonium escapes the fuel pellet, it faces a further barrier, the pressure vessel, which contains the reactor core inside a thick steel wall. If the plutonium managed to get past the wall of the pressure vessel, it would face one or more cement barriers, and then the forces of gravity as it pulled the plutonium to the outside grounds of the nuclear power plant. So how did the plutonium manage to travel a mile away from the Fukushima reactors? The answer is probably because it was ejected from the reactor building by a hydrogen explosion. More likely the plutonium was contained inside the spent fuel pellets that were housed in a pool above the Fukushima reactors. It is far from satisfactory that any plutonium managed to escape from the beyond the grounds of the Fukushima reactors, but in fact the amount that escaped was so tiny that it could do no harm.

So is there anyway, to insure that no plutonium ever escapes from a reactor core? Yes there is, in fact no plutonium can escape from a reactor if plutonium is not produced inside the core. But how is that possible? First while a lot of plutonium is produced in uranium fuel cycle reactors, less than 10% of that amount is produced in the thorium fuel cycle. A 1 GW LFTR would produce about 40 Pounds of Plutonium a year. If the goal is to minimize plutonium production this can be easily done. If the goal is to destroy plutonium, the presence of thorium in a reactor core facilitates the burning of plutonium. Finally if the goal is to produce no plutonium, then the use of fluid fuel thorium breeders (LFTRs) is highly recommended, because Neptunium-237, a plutonium predecessor isotope can be cleaned from a molten salt coolant before it can be converted from neptunium into plutonium by absorbing a neutron. Cleaning NP-237 from molten salt fluid is a relatively easy and low cost procedure. Once out of the LFTR core the neptunium can be destroyed in a burner reactor.

Thus if preventing the escape of plutonium from a reactor core is a major nuclear safety goal, designing molten salt thorium fuel cycle reactors that feature neptunium cleaning from core salts, would prevent the production of plutonium. If there is no plutonium production there can be no escape of plutonium.

Thus we have a choice of safety approaches to plutonium management, with the possibility of complete elimination of plutonium from waste stream a real possibility if it was desirable to do so. Total burn of plutonium would be yet another option.

A further approach to Plutonium safety issues would involve the use of underground reactor placement. If the reactor core and all radioactive fluids were kept underground. In Thorium fueled underground power plant based on molten salt technology, Ralph Moir and Edward Teller, Nuclear Technology 151 334-339 (2005), the authors explain,

An important feature of our proposal is to locate every- thing that is radioactive at least 10 m underground—where all fissions occur—while the electric generators are located in the open, being fed by hot, nonradioactive liquids. The reactor’s heat-producing core is constructed to operate with a minimum of human interaction and limited fuel additions for decades. . . .

Under- grounding will preclude the possibility of radioactive contam- ination in case of airplane disasters. A combination of 10 m of concrete and soil is enough mass to stop most objects. It would eliminate tornado hazards and, most particularly, contribute to defense against terrorist activities. In case of accidents, under- grounding, in addition to the usual containment structures, en- hances containment of radioactive material. The 10-m figure is a compromise between safety and plant construction ex- pense. We anticipate the cost to construct underground with only 10 m of overburden using the berm technique will add ,10% to the cost.

Moir and Teller note the safety advantage of underground placement,

A fourth safety measure is locating the reactor underground, which itself is one extra “gravity barrier” aiding confinement. A leakage of material would have to move against gravity for 10 m before reaching the atmosphere.

Plutonium is very heavy. In order for plutonium to overcome the "gravity barrier" some force would have to transport it to the surface. That force cannot be an explosion, because there is nothing in the reactor or its fluid salts that cannot explode. Nor can it be a fire, because no fire is possible. Thus the plutonium is trapped underground. In "Migration Paths for Oklo Reactor Products and Applications to the Problem of Geological Storage of Nuclear Wastes," G. A. Gowan repotted that plutonium along with many fission products including Zr, Nb, Ru, Pd, Ag, Te, Bi, and the rare earths, were immobile the the Oklo natural reactors core areas over a period of time of well over a billion years.

D.G Brookins found,

The actinides . . . were all retained in the host pitchblende.

In fact it appears that less than 10% of the actinides present when the original Oklo deposit was laid down had been lost to natural causes over a nearly two billion year period of time. Thus we can have a high degree of certainty that plutonium would be contained in underground reactor chambers, following the very unlikely event of the release of plutonium carrying salt inside the underground reactor chamber.

As noted what holds true for Plutonium also holds true for many fission products. The Oklo Reactors "natural experiment," that an underground reactor accident would not lead the the release of most fission products and actinides in a reactor or in a nuclear cool down storage. Neptunium would be a potential exception and for that reason it should be removed from long term storage of nuclear wast and disposed of by nuclear burning.

The fission products that are likely to escape in the event of a nuclear accident are well known and their behavior is well understood. They are noble radioactive gases, and volatile fission products. In fact the noble gases appear to pose little danger, and while volatile fission products are more dangerous, that danger can easily be mitigated. However, in Molten Salt Reactors it is easy to prevent the escape of fission products from the core fluid simply be removing them by simple and well understood processes. Reactor researcher, David LeBlanc states,

The volatile fission products such as the noble gases and noble metals come out of the salt as produced. Noble gases simply bubble out and are stored outside the reactor loop. Noble and semi noble metals will plate out on metal surfaces and can be collected by replaceable high surface area metal sponges within the loop.

Ralph Moir and Edward Teller note,

The molten salt reactor that operated in the 1960s had a big advantage in the removal of many fission products without much effort. Gases ~Kr and Xe! simply bubble off aided by helium gas bubbling, where these gases are separated from the helium and stored in sealed tanks to decay. Noble and semi noble metals precipitated. In the planned reactor, the old method of removing the gases may be repeated.

And what of Tritium? Tritium can be completely eliminated from MSRs by elimination of Tritium predecessor isotopes from the salt formula, or if that is not considered desirable for other reasons, it can simply be trapped in coolant salts, or by venting it in the off gas system and then trapping it in sodium fluoroborate.

Clearly then if the public wishes to be assured that it will never be exposed to radioactive isotopes from reactor cores that can be accomplished at a relatively trivial cost without sacrificing any of the advantages offered by nuclear power. I can not assess how much safety the public will want or view necessary in order to be comfortable with nuclear safety, but the technology to provide the public with safety that would assure no human deaths due to accidental releases of radioactive isotopes in a reactor core accident. This standard may not be rational, but the Oklo Natural reactors demonstrate that such a standard is obtainable, and with Molten Salt Reactor technology it is obtainable without paying a high financial cost.

Third Thorium Energy Alliance marks rapid progress toward fulfillment of dreams

My health, although still not as good as I would like has been improving since my hospitalization last December. I am, however, not in good enough health to travel. This is unfortunate because I would very much have liked to attend the Third Thorium Energy AllianceConference in Washington, D.C., earlier this month. Energy from Thorium has a brief account of the Conference in Energy from Thorium. In addition the Thorium Energy Alliance has posted Power Point Presentations from the Conference on its web page. Judging from the presentations it is probably safe to say that Molten Salt Reactor technology has entered the age of entrepreneurs.

Presentations by Kirk Sorensen, DavidLe Blanc and Charles S Holden indicated that they were either currently involved in entrepreneurial activities or were seeking entrepreneurial opportunities. Kirk has left Teledyne Brown to found a company, Flibe Energy, the purpose of Flibe is to product LFTRs and perhaps uranium fueled MSRs. The relationship between Teledyne Brown and Flibe is not clear, but the money to pay Kirk's salary has to come from somewhere. The Flibe prospectus indicates that the company founders envisage going after such markets as isolated communities, and medical isotopes, as well as stable fission product sales.

Charles "Rusty" Holden probably wants to go after some of the Same Markets Kirk is targeting. Holden's company, Thorenco LLC, is planning to build a 40 MW MSR. The reactor is designed to produce about 15 MWe at maximum. Holden intends to come out of the starting gate with a full LFTR. The reactor is a pool type reactor which involves a large pool of molten coolant salts acting as a thermal sink. I am not a big fan of pool type reactors, although they are safe. This is safety at a cost. The coolant pool will contain 93,200 Liters of coolant salt which will weigh 450 tons. The function of the pool is far from clear since the reactor design includes a dump tank.

The reactor core contains no graphite, Moderation will be by Beryllium in the form of BeF2 in the salts. This is a two fluid reactor with blanket salts doubling as coolants. The core structure uses metal (no doubt Hastelloy N) tubing. With the tubes containing fuel salts surrounded by outer tubes containing coolant salts. Since there is no core core graphite, neutron speed will be relatively bast, likely falling in the Epithermal range. The core is surrounded by a thorium reflector, neutron absorption in the reflector converts some thorium into U-233. The reactor will be a converter, and will require 1600 kilograms of U-233 fissile load, which is an enormous amount given the modest amount of U-233 14 kgs per year, which the reactor will burn,

At this point I will stop, and pronounce Holden's reactor DOA. Too much material goes into it, and too little electricity will come out. Fundamental questions are left unanswered, for example startup. 1600 kgs of U-233 is probably more U-233 than exists in the whole world right now. Where is the U-233 going to come from? There are quite a few more problems and questions. As David LeBlanc noted in his Conference talk, "Softer Spectrum" means "much smaller fissile start up." David is still on the outside looking for an opportunity. In his Conference talk, David noted,

␣ Corporate interest will always be difficult to attract
␣ No lucrative fuel fabrication contracts
␣ Min 15 year return on investment a tough sell to shareholders (no matter how big the return may be)
␣ Existing nuclear players have their choices in place

Money is still the hard part, at least for now. Despite this enormous progress is being made by LFTR/MSR advocates. A month ago, Kirk Sorensen marked the fifth anniversary of Energy from Thorium. At that time a handful of people knew what thorium was. Even fewer knew about Molten Salt Reactors. Kirk set out to educate people using social media tools, and others followed his lead. What Kirk has managed to do is to start a bottom up social movement.

Where are we headed? Japanese Researcher Takashi Kamei of Ritsumeikan University, Kyoto, Japan offered some answers in the wake of the great Japanese earthquake-tsunami of 2011, not to mention the crisis related to Fukushima reactors. Takashi pictures MSRs beginning a rapid increase around 2025and with the number of LFTRs growing more slowly before 2050. He also suggests a growing number of LFTRs after 2035. Takashi estimates a total MSR output of 258 GWe to 317 GWe by 2050. My view is that much more is possible. The future will belong to the dreamers.