Saturday, October 18, 2014

Molten Salts and the question of costs.

I have been accused of advocating Molten Salt Reactors, because of my father's 20 year career as a MSR chemistry researcher at Oak Ridge National Laboratory (ORNL).  In fact, in my first debate, with David Roberts on Grist, I argued in support of Pressurized Water Reactors.  Roberts offered several weak arguments against nuclear power.  Roberts argued that nuclear power was unsafe.  This was a weak argument, because Roberts was extremely ill informed of nuclear safety concepts, advances in nuclear safety technology, and possible future technological advances, Roberts was also unaware that accidents in American nuc power generation reactors have never produced a dingle casualty, while both wind and solar have produced multiple casulties.  Unfortunately Roberts has never recognized the power of experience, in determining the weakness of his nuclear safety argument.  

The second argument which Roberts used was a complaint about "nuclear waste."  The term, "nuclear waste," refers to the remaining fule, at the end of the fuel cycle in a water cooled reactor, togeather with other actinides, and fission products.  the big problem in Nuclear waste, is plutonium, produced primarily by U-238 and fission neutrons.  Much of the Plutonium burns in light water reactors, but a significant amounts does not burn.  Thus plutonium remaining in Nuclear waste becomes a big problem, and remains so for a long time.  
There are a number of well researched solutions to the nuclear waste problem, what is lacking is the political will to solve it.  The best solution is to fuse spent light water and heavy water fuel, in breeder reactors.  Plutonium, which is the biggest problem in nuclear waste, can be extracted from the used fuel mik, and used to power either breeder reactors, or as all or part of the start charge in LFTRs and other MSRs.  Plutonium can be burned in both thermal and fast Molten Salt Breeders.  Once plutonium and minor actinides are removed from the spent nuclear fuel, Uranium, which makes up most of the spent fuel can be recycled to fast reactors, and burned until it is transformed into fission products, which become harmless in 300 years.  Needless to say, after 7 years  of debating nuclear advocates, David Roberts does not know any of this.

David Roberts' third point was nuclear proliferation.  Roberts, has little understanding what the words proliferation risk means. If he knew something about nuclear fuel, hhe wqould be aware how expensive and difficult it would be to extract Plutonium from "Nuclear waste, and how the military qualities of that plutonium would be far inferior to the almost pure Pu-239 used in conventional nuclear weapons.  In addition light water reactor fuel is packaged in a ceramic.  It is difficult and expensive to extract the plutonium from LWR.  Finally if a would be nuclear proliferator, were to build a weapon from Reactor Grade Plutonium (RGP), he or shewould find that Pu-240, a major component of RGP, spontaniously fissions at a rapid pace, releasing a steady stream of neutrons and heat.  If the would be proliferator tested a RGP device, he would likely be disappointed by its relatively weak explosive power.  David Roberts was and appearantly still is blissfully unaware of these facts, which seem to point to water cooled reactors that use ceramic nuclear fuels, as exceedingly poor proliferation tools.  

Finally,  Roberts argued that new power reactors were exceptionally expensive, so that we never could afford nuclear power.  Contrasry arguments suggested partial factory construction, fewer parts, less material and well organized construction plans, as well as lower material input, fewer parts, all made for lower manufacturing costs.  Reactors like the Westinghouse AP-1000 featured all these.  The weakness of both Roberts argument and mine, was that both were speculative.  The truth was that future nuclear costs could only be guessed, and that the guesses were speculative.  Thus while Roberts argument was weak, my argument, although perhaps a little stronger, was by no wise strong enough to be incontrovertible.

However, while it was impossible to prove that reactors were going to be cheap enough to be affordable, what could be established was that it was possible to significantly lower nuclear costs.  I began to look for ways of lowering reactor costs, and quickly came accross Per Peterson's work on the Advanced High Temperature Reactor.  The AHTR was a molten salt cooled reactor what used solid rather than liquid fuel.  The fuel was encased in graphite slabs, or in peggles, similar to those used in gas cooled, Pebble Bed Reactors.  The switch fron Gas to salt cooling ment that the core could be many times smaller, and thus cost could be drastically lowered compared to either gas cooled or water cooled reactors.  Rhe reactor design would be much simpler than gas or water cooled reactors.  Thus small, but very useful reactors could be entirely be built in factories, while larger reactors could be transported in larger units on trucks, or by rail cars.  

Small examples of Petersons, AHTR cores would be easily transportable via truck, or railroad, thus the core would be easily manufacturable in a factory, and then shipped to its housing site.  I first found the idea for factory production of reactors in a page created by Robert Harsraves.  In 2007 Robert had yet to be informed about LFTRs, and was a supporter of Pebble Bed Gas Cooled Reactors.  Later Robert was to become a major figure in the LFTR movement.    

Robert advocated factory manufacture of Pebble Bed Reactors, However a Per Peterson study showed that a AHTR core would be less than 10% of the size of a Gas Cooled Pebble Bed Reactor core.  The bulkier size of Gas Cooled PBR cores created transportation problems for factory produced GCPBRs, while factory produced PB-AHTRs.  Factory production would lower manufacturing costs.  Housing costs,  could be lowered by the potential for transporting whole cores to its housing sites, via trucks, barges or rail cars.  As it turned out, the use of small reactors, offered several advantages including providing electricity for powering off the grid communities, providing electricity from a multi unit facility, when one ore more units are down for for maintenance, the rest can produce electricity.  Also the electrical output of the facility can be closely matched to consumer demands.  

The AHTR is closely related to Molten Salt Reactor, with A solid nuclear fuel being inbedded in graphite pebbles, or other graphite structures in the AHTR, rather than chemically linked to Fluorine, and desolved in a Floride salt mixture.  The mixture is heated several hundred degrees and then serves both as a fuel carrier and primary reactor coolant.  

I was familiar With the Molten Salt Reactor (MSR), but not the AHTR.  My father Had spent much of the first 19 years of his ORNL career doing MSR related research.  Years later I learned the full extent of my fathers contribution to MSR research.  This was part of a process, which was to make me one of the few nuclear laymen in the world who was familiar with MSRs.  Since I was less familiar with the AHTR, In was inclined to go with the one who brung me.  THe MSR was closely similar to the MSR.  Parts werew similar but rearranged.  Size and costs, were thus likely to be similar.  Thus it could be inferred from Per Peterson's reports that the cost of MSRs were likely to be significantly cheaper than the cost of LWRs.  Later I was able to point out several more cost lowering paths.  Then David LeBlanc found several more.  In fact LeBlanc believes that he can build MSR cores so cheaply that users could afford to replace them every seven years.

In short, there are many potential paths to making Molten salt reactor power cheaper.  Many of these paths can be followed at the same time.   Some of these paths can be followed by other nuclear technologies.  So far, crits of Nuclear power have not found any flaws in argument that MSRs offer a significant cost lowering potential to the future of nuclear power.  


Ronald Shapiro said...

Charles its nice to see you posting again.

John in the Lot said...

I love your pieces and long may you continue to write them. I have followed your health problems and I know that you have very bad eyesight, so I hope you don't mind that I have corrected the "Molten Salts and the Question of Costs" piece on your behalf. I can't publish it below due to the 4096 character limit but if you send me your email address to I will send it straight back.
John Preedy

Charles Barton said...

John, Unfortunately my vision problem prevents me from managing an email account.


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