Saturday, August 16, 2008

MSR/LFTR Development: Moir Again

Ralph Ralph Moir, building on work by Oak Ridge National Laboratory (ORNL), Forsberg, and Furukawa et al., set out larger scale MSR/LFTR developmental issues, in "Recommendations for a restart of molten salt reactor development", (Energy Conversion and Management 49 (2008) 1849–1858).

Dr. Moir had completed a prior study on the economics power production with the ORNL MSBR design,
"Cost of electricity from Molten Salt Reactors (MSR)", (Nuclear Technology 138 93-95 (2002)10/2/2001). In that study he estimated that the cost of produced with the MSBR would be about 7% less. But in "Recommendations", Moir estimated that the cost of electricity would be 10% to 20% lower from MSR than from LWR. Moir did not take the "full court press" approach to MSR cost savings, that I advocate in my "Keys" series. Thus the potential for cost savings by switching to MSR technology is even greater than Moir estimated. Thus the cost savings potential for MSR technology would be considerable, and initial development would not be extremely expensive. Moir points out that many of the developmental tasks envisioned by ORNL scientists during the 1970's have already been accomplished. He estimates that a 10 year, $100 million a year program would, be required to complete development. The 10 year time frame is based on "business as usual", and does not fully take into account the crises we face. Moir told me that a Manhattan project style development program would be justified.

In addition to the developmental program Moir envisioned, there would be the cost of building a test reactors. Moir suggested, "[t]he first reactor might be an electricity producing version of 10MWe modeled after the successful MSRE that operated at ORNL at 8MWth". It would be quite reasonable to replicated the MSRE. First it would give a design team a chance to have hands on design experience by updating the design of the original MSRE. Such an approach would be a quick and dirty route to building a working MSR that could be used for experiments, and obtaining operating experience. The MSRE II could be built with the potential to do fuel processing, but fuel processing equipment need not be a part of the initial build, and can be added later.

Moir suggests,"The next reactor might be a demonstration of a future commercial reactor
operating at a hundred or a few hundred MWe. These two steps might cost $9B ($450M/year for 20 years)". But would completion of these steps really require take 20 years? First many tasks can be performed in parallel tasks. By using the original MSRE plans, the fabrication or unmodified parts can begin while the design modification process is going on. Site construction can begin during the design phase as well. As design modifications are completed, the fabrication of modified parts can be commenced. Thus even before the completion of the modified design, reactor assembly could be underway. The second reactor could be a working developmental prototype.

There is no reason why MSR/LFTR electricity producers need be 1000 MWe+ size reactors. (I say this despite the fact that many LFTR supporters do not believe this. The advantage of the small 100 MWe to 300 MWe sized reactors is that it can be mass produced in a factory, and transported in as a single unit, or in several modules to a final set up site.

While the design of the MSRE II is still going on, the design of the LFTR developmental prototype could begin. Thus by the time the MSRE II is complete, the design of the LFTR prototype would be well underway. In parallel with the design of the LFTR prototype, the design of the manufacturing system could also be underway. The manufacturing team would not only design the factory system for building production LFTRs, but also siting and how to conduct efficient site setup. In addition, decommissioning and fission product disposal should be studied. It should be assumed that not all fission products are waste, and thus the study of FP uses would be a developmental task.
Moir's thinking on time frame is influenced by the Japanese approach of Furukawa, et al. Thus assumptions like "deployment rate" that do not violate "the norms of growth and investment rates in new industries" may not accomplish what we need. The Japanese may plan for growth over a 100 year time span, but that is not the way things are done in Texas. In Texas a the oil industry began in the late 19th century,  Oil really got going in Texas after the 1901 Spindletop gusher.  The Texas oil business peaked around 1950, and in 1956, oil geologist M. King Hubbert foresaw the coming decline of not only Texas oil, but the world wide oil business.  Texas oil production peaked in 1972 at just around 3.4 million barrels a day.  By the end of the 20th century Texas oil production had withered to less than 1/3 the 1972 peak.  World oil production, for all intent and purposes has peaked, and a similar decline is expected to soon begin.   This history would not encourage people who live in Texas to think in terms of business planning on a 100 year time frame,  or in terms of business as usual.   Texans are known for developing energy sources in a hurry, but unlike oil, a speedy development of the MSR/LFTR would not be followed by its equally speedy departure. Considering its parsimonious use of nuclear fuel, the MSR/LFTR may be around for a very long time.   

Moir assumes that by "2050 only a few hundred GWe seem possible for this new or for practically any new fission technology, which is about equal to the present world nuclear capacity". He adds, "the number of light water reactor (LWR) can grow some but quickly is limited by fuel limitations and waste management". This observation is frequently repeated by nuclear power critics.

I would argue that far more deployment is possible by 2050. First, large numbers of reactors can be mass produced in factories, and on site set up can be greatly simplified. Small reactor size mean that large grid modifications are required to accommodate a large power flow. A modular approach coupled with siting at existing coal and natural gas powered generating plants, would mean that grid tie in is possible with minimal modifications.

Nor would the availability of nuclear fuel be a problem. Thorium Energy, Inc., has recently reported that its Lemhi pass claim contains "600,000 tons of proven thorium oxide reserves. Various estimates indicate additional probable reserves of as much as 1.8 million tons or more of thorium oxide contained within these claims". In addition, "vein deposits of thorite (ThSiO 4), such as those that occur in the area of the Lemhi Pass, present the highest grade thorium, mineral, and are believed to contain approximately 25 to 63 percent thorium oxide (ThO 2) per ton of raw ore. Thus one ton of thorium ore could potentially yield as much as 500-1,200 lbs. of high grade thorium oxide (ThO 2), as compared with less than one percent of raw Uranium ore that is typically utilizable. The deployment of Lemhi Pass Thorium represents a more economically feasible source of nuclear grade ore than Uranium deposits".

Thorium cycle LFTRs requires fissionable U235 or Pu239 for reactor start up in the absence of U233, but there is plenty U235 and Pu239 available in nuclear weapons and in post weapon stockpiles. Both are also found in "spent nuclear fuel".

For once through Light Water Reactors 600,000 tons of nuclear fuel is not a lot, but LFTRs can burn Thorium at 98% efficiency. Thus 600,000 tons of Thorium can supply the United States with all of its required energy for 400 years.

Thorium is three to four times as abundant in the earths crust as uranium. And little effort has gone into exploration for thorium world wide. It is unlikely that that the Lemhi Pass Stake is the only such Thorium ore body in the world. Lower grade but recoverable thorium reserves are believed to exist in the White Mountains of Vermont, where Rice University geologists observed in the early 1960;s that local granite appeared to contain tens of millions of tons of low grade but recoverable Thorium ore.

Moir suggests using both uranium and thorium fuel cycles in MSRs. there is a strong case to be made for that. Nuclear waste, less fission products, could serve as nuclear fuel in moderated MSRs. Indeed, if nuclear waste is processed by burning and breeding in MSRs, the present supply of depleted Uranium and "spent nuclear fuel" alone could supply the United States with all of its energy for hundreds of years.

While noting the French view that unmoderated MSRs would resolve the graphite problem, Moir appears to favor graphite moderated MSRs. He believes that "power flattening" would increase "graphite life time and increases the fuel inventory". But "load following results in
reduced average power and reduced revenues but longer life until graphite damage requires shutdown for replacement [of graphite]". He adds, A base load plant can have 30 years graphite life time for a diameter of about 10m at1 GWe or 5m at 150MWe. A load following plant can have a diameter of about 5m at 230MWe. Core design can change these numbers somewhat.

Moit correctly notes, "The core size is related to factory manufacture of the vessel and transportation to the reactor site, which is a favorable factor for diameters up to about 5m. At 10m the constructionis likely an expensive field operation or more elaborate transportation to the site by barge for example".

But Moir agues against small MSRs:

"In the course of development of the MSR and during the early deployment of the first few power plants, the size of the vessel will not be a concern, but extensive deployment is expected to be highly driven by ‘‘market pull” resulting in a tendency towards larger vessels. Economic competition will be intensive with mature LWRs whose sizes today are approaching 2GWe for economy of scale reasons. This means the MSR might have to deliver large plants in order to be competitive. Of course smaller markets away from transmission grids will still have a market for small plants".

Here I would disagree with Dr. Moir. He does not look analyze a cost comparisons of in field custom construction costs for "giant economy size" nuclear plants and and small factory produced reactors. The giant economy size approach uses a manufacture technology pioneered by the Egyptians with the construction of the Pyramides. While giant the on site product may be, economical it is not. At least not compared to the economies that can be wrung from small reactors. A brief list of economies will be sufficient. The Factory production of LFTRs will:

1. Reduce labor cost by using less skilled labor more efficiently than highly skilled laborers are used in custom manufacture, and by allowing the large scale use of labor saving machines in the reactor factory.
2. Decrease manufacturing and on site set up time, the greatly reducing the time which plant owners will be paying interest without revenue being generated.
3. Allow for the use of sits which may already partially prepared, such as fossil fuel power plant sites, but which may not be appropriate for large LWRs.
4. Allow the use of reactor for industrial process heat/electrical cogeneration in situations in which a huge reactor would be hugely inappropriate for the application. LFTRs bottoming heat would be useful for desalination while the reactor is producing power.
5. For some grid uses, LWRs of any size would not be an attractive option to LFTRs. These include load following, which investors would see as an attractive option because it would prolong core life, while LWR are inferior load followers. A further grid advantage for LFTRs would be as peak load generators. A MSR that is not generating electricity, would carry a higher level of heat in its salts than it would if operating at full power. As the reactor goes online, heat would be drawn from the salt, and the chainreaction in the reactor core would increase, replacing the lost heat in the salt. Thus the LFTR would function well as a peak reserve power source.

Dr Moir concludes:

"The MSR has so many favorable features, many discussed here that one is at a loss to explain why the reactor has not already been developed. Once a program has been killed there is a stigma attached that creates a legacy of its own. Several decades ago reactor accidents, low number
of orders for new reactors, low uranium prices and low-cost natural gas have discouraged reactor development such as the MSR but all these things have reversed. I strongly recommend independent thinkers to re-look at and invest in the MSR. China and India could take on this task to their great advantage. Even a philanthropist or venture capitalist
could breathe new life into this concept–as mall 10MWe (or even much smaller) test reactor would provide relevant information useful to proceeding on to a commercial power reactor and represents a low risk, low cost first step".

I am in complete agreement with Dr. Moir's conclusion.


jimcrea said...

The technique that the Pebble Bed Modular Reactor uses to solve the large reactor requirement is the concept of the reactor cluster. In the PBMR cluster up to ten small modular reactors are linked together under the control of one centralized control room, and share one or more power turbines.

This ability allows for the small clustered PBMR to support the following advantages:

• Centralize control room
• Maintains factory mass production and quality control.
• The safety of reduced power density.
• A small exclusion /evacuation zone in case of failure.
• The ability of the cluster to grow smoothly, as the need for power increases.
• The reduced need for capital to get a cluster started.
• The advantages of n + 1 fault tolerance.
• Maintenance of a cluster module without a shutdown of the entire cluster.

This ability to support clustering gives the PBMR a decisive advantage over the MSR/LFTR reactor approach that you have described so far.

This clustered design is not easy to define and implement, but it is well worth while thinking about for MSR/LFTR reactor design. It could give the design approach the lift it needs to get off the ground.

Charles Barton said...

Similar concepts for small MSR are quite obvious. Small MSR/LFTRs can be clustered in any number to provide base power, The MSR can be automatically follow power loads. Also MSRs can be operated reak load reserve. Heat retained in the salt can put power on line within seconds. As salt heat drops, the fuel is drawn into the core, increasing reaction rate, and increasing ther heat available. any number of MSR's can be clustered together. MSR's have all the advantages of PBR's and in addition can breed their own fuel. Thorium cycle fluoride reactors burn up to 98 percent of Thorium run through the reactor, thus producing very little "nuclear wasre".

Ray The Money Man said...

I really believe it will be countries like China and India that will lead the way in this type of technology becoming common place. Thanks, great Post!

Charles Barton said...

The Chinese are developing a Pebble Bed Reactor, but give no sign of interest in the LFTR. The Indians might b4 more inclined to be interested, because they have q large thorium reserve,

Neurovore said...

So, if I understand correctly, the main difference between the LFTR and the MSR is the fact that one uses liquid fluoride as a coolant while the MSR uses liquid sodium. Bewteen the two designs, which one seems to be the better reactor? I have looked at the posts on the Energy From Thorium blog talking about the difficulty of using molten sodium as a coolant because of its corrosiveness and the fact that it is quite reactive, but I am not sure how serious of a problem that would be in the design of the MSR.

Charles Barton said...

The LFTr is a type of MSR. MSRs can either run with thorium or uranium fuel cycles. They can also use Fluoride or chloride salts. Thus the LFTR uses fluoride salts and runs a Thorium fuel cycle.

Neurovore said...

Oh, I see. Thank you for clarifying that for me. I must have misread something.

By the way, do you have any posts detailing just how much the idiotic idea of "clean coal" is being promoted in the US? I have heard about this from other sources, and I have a sinking feeling that the future of nuclear power in the US will lose out to a heavily marketed scheme pushing FutureGen.


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