Friday, March 20, 2009

Scaling the Liquid Fluoride Thorium Reactor: The Big Lots Reactor and the Aim High Reactor

I believe that we have reached the point in our understanding of the potential thorium/Liquid Fluoride Thorium Reactor future, where we can talk about our grand plan. I believe that we can show that the use of thorium fuel cycle LFTRs represents, if not the silver bullet, then at least the thorium bullet of future energy. The most important questions which we need to answer about thorium cycle/LFTR technology are:
1. Can it be built at a reasonable cost?
2. Is is scalable enough to meet our energy needs?
3. Can we complete world wide deployment of carbon technology replacing LFTR by what is often seen as the cut off date of 2050?
The answers to these three questions are related. Indeed, LFTR costs are a part of the scalability question.

Perhaps my only original idea about Liquid Fluoride Thorium Reactor (LFTR) design was more a marketing suggestion, which combined David LeBlanc's suggestion that capital costs for LFTRs could be lowered by using lower cost materials that would tolerate somewhat lower reactor performance. David LeBlanc's suggestions indicated that low cost LFTRs could be built from commonly available low cost materials. I saw that this would solve a major problem in all current plans to produce post carbon electricity, that is the absence of a low cost load following and peak reserve electrical production technology to replace natural gas. Indeed the Greenpeace "energy [r]evolution" plan is not a true post carbon energy plan because it calls for an increase in the capacity of natural gas powered generating facilities over the next 20 years in order to supply load following and peak energy capacity to the grid as a compensation for the increased penetration by wind powered generators.

I named the lower cost LFTR, the Big Lots Reactor after the store chain from which surprising bargains sometimes emerge. Unlike Big Lots which finds bargains among over stocked and close out items, our reactor bargain will come from intelligent approaches to reactor manufacture and site construction, more efficient use of labor and careful attention to containing financing costs.

When I read David LeBlanc's observations, I was aware that operating LFTR on a partial power or a part time basis decreases neutron damage to core material. At the same time load following power and peak load power is purchased by utilities at a premium price. It appeared to me that there was a potential for synergy here.

The LFTR has significant potential as both a load follower and a peak reserve power source. The trick would be to lower its price enough for LFTR load following/peak reserve to be economically viable. That is where David LeBlanc's suggestions come in. By lowering capital costs the cost of the reactor manufacture can be recovered while running it with a less than base load capacity factor.

Thus the Big Lots reactor can be run on a 16/7 or 16/5 schedule. It can be run on less full power for most of the day. A Big Lots Reactor can rapidly increase power if a major online generating unit suddenly goes down, or if the electrical utilities experience a surge in consumer electrical demand. It could even cope with the fluctuating electrical output of windmills.

The original Aim High plan calls for LFTR production from high performance and expensive materials. The Aim High Reactor would be designed to operate at maximum temperature compatible with current materials technology. The Aim High Reactor would be designed for base load power and/or the production of process heat. As a base load reactor the AIM High Reactor would be expected to produce maximum power on a 24/7 basis. It is very conceivable that a Generation II Aim High Reactors might be built. The first generation Aim High Reactor, to go into production about 2020, would be built using expensive Hastelloy-N in the core structure and Molten Salt piping. The Aim High I could operate at a temperature of up to 700 degrees C. A further Aim High Reactor, the Aim High II, might then be developed to provide Industrial process heat up to 1000 degrees C. The Aim High II would be built of more exotic materials like carbon-carbon composites, and would be able to produce power with a high level of thermal efficiency.

The Big Lot Reactor can be built in the same factory as the Aim High Reactor, and the two reactors might share many of the same parts. Parts like pumps, heat exchanges turbines, fuel processing units, helium handling equipment, and core graphite can be used in common. Core structural matter for the Big Lots Reactor would be stainless steel as would be the reactors external pipes. The Big Lots core design should use a moderated two fluid approach, and might use NaF-ZrF4-UF4 salt rather than LiF-BeF2-UF.

The Big Lots would be expected to operate no more than 2/3rds of the time and to operate at capacity factor of .60 or less. Since the lower capacity factor means less exposure to radiation over a given period of time, the stainless steel parts can be expected to be reasonably robust in the face of anticipated radiation levels. The Big Lots Reactor could be deliberately oversized in order to promote reserve peak capacity. Thus the Big Lots might be expected to operate at 25% of full capacity for part of the day, while more capacity could be brought on line quickly in the face of rising demand. Unlike the Light Water Reactor adding substantial increasing design capacity would not add proportionately to overall reactor costs.

Production of the Big Lots Reactor would be highly scalable because it is factory built. The production process can use labor savings machines at every stage of the production process. Given a large enough production volume, parts manufacture can be partially or even completely automated. Robots can replace workers in some assembly operation. It is anticipated that the factory produced Big Lots will be shipped to the reactor site for final setup in modular units. Labor savings equipment can be used in site preparation, component assembly and in finishing off the site.

The Big Lots factory would be large, but not larger than a modern aircraft assembly factory. Component modules need not be produced in the same factory. The modules would be major reactor components. The assembly of the modular components should be relatively simple and quick, with most of the assembly being performed in factory settings.

The goal of the Big Lot/Aim High Program should be the production and distribution of enough LFTRs that by 2050 to assure that world wide carbon production could be lowered by 80% from 2009 levels by 2050. This will be made possible by massive production and deployment of Big Lot Reactors after 2020.

The role of the Big Lots reactor would be to assure that material shortages would not prevent the the construction of the required number of reactors. By using a common material like stainless steel, sufficient building materials should be available to insure the required number of reactors can be built. Production facilities can be designed with the capacity to handle a large number of reactors. In the United States, Europe, Japan and South Korea, highly mechanized and automated assembly/construction methods would be used to limit labor input. However in India and China less mechanized site preparation and final assembly approaches might be used.

Site design should be standardized to the extent possible. To the extent possible old power plant sites should be recycled as Big Lots sites, with structures and equipment reused to the extent possible.

The Big Lots Reactor should be designed with cooling options. It could be air cooled or water cooled depending on the availability of water.

Start up options for all LFTRs would include recycling plutonium from nuclear waste or nuclear weapons, using U-235 from nuclear weapons, or by breeding U-233 from Th-232 in LFTRs and other Molten Salt Reactors. Indian technology would also create the potential to breed U-233 from Th-232 in LMFBRs. U-235 can be enriched to HEU levels using laser technology and then used for LFTR start up.

LFTR Costs
I have recently pointed out reports that Indian LMFBRs costs will run at an estimated $1.4 billion per GW, while Chinese LWR costs run between $1.6 and $1.75 billion per GW. In neither case does the cost of reactor R&D play a major role in reactor costs. In both cases it would appear that financing costs are a lower percentage of total reactor costs than they would be in the United States or Europe. The rest of the cost savings would appear to come from the cost of labor. In the case of the Chinese reactor we know that the total hours of labor are similar to those required to build reactors in Europe and North America. We can suspect that the Indian LMFBR requires significantly fewer hours of labor than Chinese LWRs require.

The cost of electricity is a fundamental measure of the competitiveness of a society. The low labor and financing costs of Asian reactors would seem to give China and India significant competitive advantages during the second half of the 21st century unless energy related financial and labor costs can be better controlled. By shifting reactor manufacturing methods and settings, and by taking innovative approaches to reactor siting and facilities construction labor costs can be lowered. Controlling labor costs, the time required to build reactors will make significant contribution to closing the the gap in the cost of financing rectors. Thus it seems possible that LFTRs can be be built at a cost that would be comparable to the Asian cost range of $1.4 to $1.75 billion per GW. More research is needed, and beyond research a nearly fanatic commitment to keep LFTR manufacturing costs under control. Nothing less than the fate of a civilization rests on this.

Is There Enough Thorium?
Thorium is estimated to be three times as abundant as uranium in the the Earths crust. Millions of tons of thorium are present in mine tailings scattered around the world. The LFTR is several hundred times more efficient at extracting energy from thorium as the current generation of Light Water Reactors are in extracting energy from uranium. If we extracted no thorium from the earth and only recovered the thorium found in mine tailings and other surface sources enough thorium could be recovered to provide energy to all human societies at a level that is equivalent to those enjoyed in Western Europe for thousands of years. Recoverable thorium resources are large enough to sustain human society for millions of years.

Can we start all of the LFTR?
This brief study is based on the assumption that the major obstacle to replacing carbon based energy technology with post carbon based energy technology would be factors like materials availability, and labor and financing related costs. I have argued that by focusing on LFTR technology and what might be described as a full court press approach to LFTR cost savings, that it would be possible to manufacture and deploy world wide, enough power generating reactors to replace current carbon based energy sources with low CO2 emitting energy sources. I have elsewhere argued that it would be possible to start these reactors with plutonium from spent reactor fuel, plutonium-239 and uranium-235 form nuclear weapons, U-235 produced by laser enrichment, and by U-233 bred in Molten Salt Reactors including LFTRs. It would also be possible to breed U-233 in Indian LMFBRs.

Is thorium/LFTR technology scalable enough to reach our 2050 energy goals?
The Aim High plan, the plan to substitute thorium/LFTR energy sources for carbon based energy sources by 2050 is feasible. Thorium/LFTR technology is scalable. Indeed, the Aim High Plan is the only feasible option that would allow Europe, North America, Japan, South Korea China and India to adopt their energy requirements to the necessity of finding post carbon energy sources. Plans to use renewable energy and conventional nuclear power simply will inevitably fall short.

What are the obstructs to the realization of the Aim High Plan?
The answer is simple, knowledge of the potential of thorium/LFTR technology, and commitment to its development and use. The road is open, we have only to see it, and chose to follow it.


donb said...

Charles Barton wrote:
This brief study is based on the assumption that the major obstacle to replacing carbon based energy technology with post carbon based energy technology would be factors like materials availability, and labor and financing related costs.

These same factors are present no matter what we do, unless we decide to slide back to the pre-industrial civilization. I think it can be argued that the LFTR would minimize materials use and financing costs. Take materials, for example. Not only does the LFTR produce a lot of energy given the materials input, it can be placed near load centers so that long distance power transmission lines do not need to be constructed.

Charles Barton also wrote:
The answer is simple, knowledge of the potential of thorium/LFTR technology, and commitment to its development and use. The road is open, we have only to see it, and chose to follow it.

Simple does not mean easy. There is a big hurdle in overcoming the fear of radiation (promoted by the likes of Greenpeace). There is a big hurdle in overcoming government regulation that focuses excessively on safety while failing to see the dangers in NOT going forward with advanced nuclear energy. Don't get me wrong -- nuclear energy should be safer than what we are doing now, but making something as safe as possible only delays the deployment of safer energy sources. The net result is worse safety! Also, while we can still live in relative comfort using fossil fuels, there is a lack of foward thinking that needs to be overcome. It seems to take a crisis (like $4+ gasoline) to get people moving on solving problems, but by then years are necessary for the solutions to be implemented, all the while the pain continues.

The way forward is clear. But it will take bold initiatives by visionary leaders, much like the race to the moon, to move to the goal.

Anonymous said...

For me, the Big Lot Reactor is a LFTR that has no moving parts; no pumps, no pipes, no heat exchanger, no operators, no maintenance requirements, and is a small nuclear battery at 70 MWt with heat pipe heat transfer interface to an external steam turboelectric generator. Deployed underground, its operational life time is 30 years.

It utilizes a thick hot pressed thorium carbide containment vessel with a thin stainless steel outer substrate to provide a combined U233 neutron breeding blanket and gamma shield. Heat pipes using potassium remove the heat from the core and blanket to the gen set.

The thorium blanket barrier would provide very high temperature resistance since the melting point of thorium carbide is about 2600°C. But the operating temperature of the Big Lot Reactor would only be about 500C.

A solid blanket would be impervious to the effects of corrosion; a large amount of thorium carbide can decompose at the inner edge of the blanket in a redux reaction to fluoride core salt without affecting the structural integrity of the blanket shell on the whole.

Almost all of the neutrons generated by the reaction would stay inside the reactor and be absorbed in the thorium blanket to produce a very pure U233 in solid suspension in the thorium carbide; that is, most blanket reaction products would be contained inside the crystal matrix of the blanket material including U232/233.

The carbon in the carbide would moderate and thermalize the reaction in the blanket increasing the efficiency of the blanket reaction producing a maximum amount of U233.

The blanket would be safe from proliferation. A small amount of uranium-238 carbide can be added to the solid blanket to increase the proliferation resistance of the solid blanket. Some plutonium would be produced but in very small amounts and it will degrade to very poor quality reactor grade levels as the blanket ages.

In order to get to this U233 that has been produced inside the very walls of this 200 ton reactor containment vessel, a proliferator must destroy and disassemble the reactor, lift its heavy reactor core out of a many meters deep reinforced aircraft crash proof hole in the ground, then cut the thorium up into small pieces while enduring heavy gamma radiation exposure, next reprocess these reactor pieces using isotopic separation since the U233 is denatured with enough U238 to make chemical separation of bomb grade U233 impossible, and do all this without being detected. Now, this is a tall order for any proliferator and may just be an impossible assignment.

With the U238 and a large amount of carbon present in the blanket, and the very massive size of the blanket segments, together with U-232 buildup over time producing hard gammas, the solid blanket will be very proliferation resistant.

To be clear, the main advantage of a solid breeding blanket integral to the very structure of the reactor itself is that proliferation of the U233 contained within is impossible without destroying the reactor.

Fabrication of the blanket is straight forward with much experience existing widely throughout the industry; the thorium in the thorium carbide is very inexpensive and can be recycled during the reprocessing of the blanket during the removal of the U233.

This recycling happens at the end of the service life of the BIG Lot reactor, the reactor vessel is sent back to the factory where it is reduced to liquid fluoride salts that become the feedstock of a next new Big Lot. This feedstock can only be used by the new Big Lot and not for bombs. The small amount of waste products are held at the factory for a few hundred years to cool down before they are mined for the many precious elements contained within like platinum and iridium!

The Big Lot can be deployed safely anywhere in the world, and can be manufactures cheaply, in the factory, and in high volumes.


Anonymous said...

Excellent job Charles.

The most important thing I learned form the LeBlanc lecture is the fact that we can build a once through MSR that produces high temperature high pressure steam using ¼ of the uranium requirement of conventional reactors.

The chemical reprocessing system design is the most problematic and time consuming aspect of developing a liquid fueled breeder reactor. Eliminating that system leaves a very simple reactor design that could be developed and tested in the minimal time span.

Given the abundant supply of affordable uranium from sea water these simple MSR’s could meet the worlds need quickly and for as long as necessary to allow R&D of a full blown breeder reactor.

I would also suggest combining the MSR concept with the floating plant concept so that we can provide high paying jobs selling these plants all over the world.

Bill Hannahan


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