Sunday, February 15, 2009

The Greatest Bargain of the 21st Century.

In May of 2008, I posted a series of posts on the cost lowering potential of LFTR technology for nuclear power. I was able to point to a number of areas in which significant cost lowering potential was present, especially in comparison with Light Water reactor costs. I did not attempt to assign a cost number but a figure of 25% of the cost of conventional nuclear power generating reactors seemed plausible. It is possible that LFTR costs might not be that low, if attention is not paid to rigorous application of the cost lowering potentials.

Why does the LFTR have such cost lowering potential?

First because its design is very simple compared to LWRs. LWRs require many hundreds of valves, miles of pipes, numerous pumps, thousands of supports, miles of cables, hundreds of embedded instruments and other parts, each built to very exacting specifications and requiring intensive highly skilled labor for their installation. Mistakes in parts installation may necessitate large scale rebuilding. Constant monitoring of the quality of reactor construction is of the utmost necessity, and consumes many hundreds of thousands of hours of supervisors time. The LWR has two active control systems. It has at least two cooling systems, and a massive 8" thick pressure vessel that surrounds the reactor. The LWR operates under high pressure conditions. Coolant water is pumped under high pressure through hundreds of channels in the reactor's core. The entire core coolant system is built to very exacting specifications. Even a minor failure of the coolant system could lead to core damage. Thus the LWR is a highly complex machine, requiring hundreds of thousands of parts and millions of hours of labor to construct. LWR construction requires great organizational skills, and extremely diligent supervision. It is relatively easy for very costly problems to emerge during the construction. For example, if cement used in the reactor construction does not conform to design specifications, structures built with inferior cement have to be torn down and rebuilt. Such problems can lead to delays in construction schedule, and significantly contribute to project cost. The construction method, which requires the use of a huge amount of on site labor , is very difficult to organize and control. Problems associated with the complex reactor construction labor system contribute to overall reactor costs.

In contrast Molten Salt Reactors including the LFTR are very simple. A liquid coolant fuel mixture is pumped through the reactor core and then through a heat exchanger and back into the reactor. There may be a secondary cooling system if the primary system breaks down, there would also be an emergency back up system that would automatically drain the core if both cooling systems failed. The core would be drained into specially designed tanks that would be passively cooled, by a naturally circulating air or water coolant system.

The LFTR reactor can be designed to include several small chemical processing units. These units greatly improve the efficiency of LFTR operations. While they add to LFTR complexity, even with a full array of chemical processing units, the LFTR is still far less complex than the LWR. One of the keys to lowering LFTR costs is the simplicity of the LFTR design.

The LFTR operates at a much higher temperature than LWRs. For that reason a small LFTR will operate with greater thermal efficiency than a very large LWR. This opens the door to greater design flexibility. With LFTRs, designers have significant design options related to size. LFTRs can be designed for modular use. Several small LFTRs can be clustered to produce the power equivalent of one large reactor. There are a number of advantages in doing so. Small reactors can be factory built, and transported by truck, train or barge to a final set up site. Factory production would use labor more efficiently, and product quality could be much more easily controlled. A serial production process would lead to rapid learning, improved quality and lower price. Reactors could be built in periods of a few months rather than several years. The significantly shorter construction time would have a positive effect on overall reactor costs:
A. The cost of accrued interest during the construction phase would be significantly less or factory built small reactors than for site-built large reactors.
B. Small reactors can be set up and brought on line within months of being ordered, thus quickly adding to the owner's revenue stream.
C. Small, low cost, quickly set up reactors have fewer risks. Lower risk premium, lower capital costs.
Small modular LFTRs allow greater flexibility in reactor siting and housing:
A. Old coal and natural gas power plant sites can be recycled with considerable economies.
B. New grid hookups would not be required. LFTRs sited at old power plant sites, could use the existing grid hookup.
C. On site facilities could be reused, decreasing construction expenses.
D. The location of small reactors close to electrical consumers would conform more closely to a distributive model, and would assure greater grid stability by bringing electrical production close to the customers. This reduces the necessity of making costly additions to the grid.
LFTRs do not require expensive, hard to obtain materials that could compromise LFTR production. In addition to materials options explored at ORNL between the 1950's and the 1970's a variety of other materials options appear to be available. These include Carbon-carbon composites which can be used with very high performance LFTRs that can produce industrial process heat, and commodity materials like stainless steel, that can be used to lower LFTR costs even further. Ultra low cost LFTRs might be used to replace natural gas fired generators that are currently used in peak reserve capacity.

The LFTR opens the door to relatively novel, innovative and low cost housing options, that can enhance reactor safety while lowering costs. Underground or underwater housing should be explored. LFTRs can be housed in underground chambers on existing power plant sites. Such chambers need not require massive amounts of steel, and concrete, as present reactor containment structures do. Underground reactors would have superior protection against terrorist attacks through car bombs or large aircraft attacks. They could easily be made relatively impervious to attempts by terrorists to seize the reactor. Finally underground reactor can be designed to include multiple anti-proliferation barriers, making the underground reactor a highly undesirable target for would be proliferating nuclear terrorists. These very desirable goals can be achieved without the high cost of above ground massive containment structures.

In addition to the use of recycled coal plants for underground sites, mines could be used for LFTR siting. Salt mines make a very interesting option, with the potential of clustering a relatively large number of modular LFTRs in salt mines, with no above ground structures required.

In addition to the many cost lowering options available to LFTR designers and operating utilities, the LFTR can be designed to operate without operational staff. Since the LFTR is highly stable under passive control, no operator input is required in order to assure the highest level of safety. Thus while security staff would be required to protect LFTRs from terrorists and misguided acts of vandalism, no operators are required for safe and efficient LFTR operation and an operational staff would be redundant. This would lead to further economies in LFTR design, construction and operation.

It is quite obvious that LFTR costs could be substantially less than Light Water Reactor costs. At the moment it is far future LWR costs that are far from clear. My own guess is that if all of the LFTR economies I have mentioned were implemented the relative cost savings of the LFTR would be greater than 50% of the cost of Light Water Reactors, and LFTRs might well cost 25% of the cost of LWRs. If we consider that large amounts of LFTR fuel has already been mined and is currently regarded as mine waste, the LFTR could well turn out to be the greatest bargain of the 21st century.


Anonymous said...

Very interesting, Charles

It could be intersting to list kg of steel, rebar, etc.. for kW of LFTR vs LWR

Charles Barton said...

The Materials input into reactors is known, however the material input into LFTRs has not been calculated.


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