Thursday, November 5, 2009

Small Reactors, Mass Reactor Deployment, and the LFTR

There is at present no end of projects to build small and mini reactors. Most of these projects will not get beyond the concept stage, but a few probably will. I distinguish between mini and small reactors by power output. I would class reactors that generate less than 100 MWe as mini reactors, and reactors that generate from 100 MWe to 400 MWe as small reactors.

Mini reactors are primary useful in situations in which you need small stand alone energy producing units. Think of cities like Juneau, Alaska, where about 30,000 people live. Juneau is too small to rate a big power plant, and too remote to rate an electrical grid hookup. Juneau thus needs a very reliable and low cost, 24 hours a day, 365 days a year electrical technology, to keep all of its dishwashers, and hair blowers running. The 25 MWe Hyperion reactor would appear to offer everything Juneau needs, and at a cost Juneau can afford. Of course. the prototype Hyperion mini-reactor has not been built yet, so estimates of cost and claims about practicality might be subject to revision.

In addition to providing electricity, mini reactors could provide district heat for cities like Juneau. If Juneau had a water shortage, electricity from the reactor could be used to desalinate sea water through reverse osmosis. Local industries could use the Hyperion's heat as input into chemical and manufacturing processes. Clearly then mini-reactors are potentially useful then, but perhaps most useful to smaller communities that are off the grid.

Small reactors are large enough to be useful on a grid, but small enough to be partially or completely factory produced. The proposed Babcock & Wilcox 125 MWe mPower reactor is an ideal example of the small reactor. While engineers will argue in theory that small reactors will be more expensive than large reactors, factory production can change that. Babcock & Wilcox appear to be planning to build their small reactor as a lit in a factory, and then assemble the kit on site. Westinghouse is planning to build the much larger AP-1000 using the same kit system, so Babcock & Wilcox does not seem likely to save a great deal of money with its small reactors, and indeed the amount of on site labor Babcock & Wilcox appears to believe it will need to manufacture the mPower will not lead to a major cost breakthrough.

The Tennessee Valley Authority (TVA) is planning to buy the first mPower, and to set it up in East Tennessee. Was planning to build as many as 4 big reactors, and still might build them, but the mPower means that TVA can buy reactors in smaller chunks and thus encounter lower financial risk. A large reactor could cost the TVA as much as $7 billion and possibly more. The mPower would be expected to cost under $1 billion, and begin producing power more quickly than a large reactor. Producing power means you don't have to carry interest.

Thus the advantage of a small conventional reactor like the B&W mPower, is that it lowers risks. The mPower has some slight advantages in deployability, but apparently very little advantage in price over larger reactors.

One way to get costs down is to to get better control of labor costs. One good way to do that is to build your reactors in India. Indian built reactors are, even by Chinese standards, inexpensive, and as I have frequently argued the Indians may be about to eat everyone's lunch through low energy prices. The Indians have been building small reactors for years, perfecting their design, and trying out cost savings tricks. What they have learned is impressive, and if they start manufacturing reactor kits in factories as the Chinese are doing, they will stand on
the edge of an energy revolution.

So one way to lower nuclear costs would be to employ Indian labor in reactor construction. But that would not work in the United States or other advanced societies. We have to bring labor costs down by increasing labor productivity. In addition we face a time limit. Climate scientists say we need to bring CO2 emissions under control by 2050. Under control means something like an 80% reduction in CO2 emissions, so that means replacing most of the world's current sources of energy. Thus energy replacements need to be hugely scalable, and they need to be cheap. Conventional reactors are neither scalable enough nor cheap enough, The mPower example demonstrates that small conventional reactors are not going to do the trick. In order to meet our need for low cost and high deployment, we need a compact reactor that is small enough to be transported by rail, truck or barge, easily and quickly assembled on site, and online within a few months. The whole energy generation system has to be low price, and its nuclear fuel will have to be both low cost and abundant.

When I figured this out, the answer to how to do this became amazingly clear. My father had done research on just such a reactor over a 20 year period of time at Oak Ridge National Laboratory. That reactor, the Molten Salt Reactor, was known to be capable of operating on the thorium fuel cycle. Researchers believed it to be extremely safe. It was so good at destroying nuclear waste that it had been actually proposed for use in a nuclear waste destroying system. The MSR was both simple and compact, ideal for factory production, and transportation. The MSR was extremely efficient. Thus building a huge reactor was not required in order to efficiently produce electricity. In fact a 100 MWe MSR could produce electricity more efficiently that a 2000 MWe conventional reactor. Nor did the power production system require elaborate housing. You could ship in the turbines and generators by truck, rail or barge, set them up in an old power plant or factory, hook them up to the grid, and to the reactor, and you are ready to produce power.

If you are worried about terrorist attack, you can dig a hole and stick your reactor in it. Kirk Sorensen has produced such designs. Once your reactor is in the hole, it is not going to be damaged by truck bombs, or aircraft attacks. On-site set up and assembly can be facilitated by highly automated machinery.

What about fuel, you ask. It turns out that there is a great deal of thorium just laying around. There is something like 400,000 tons of thorium sitting on beaches in India. As David Walters would say, all you need is 4 Indians with shovels and a pickup truck. In an afternoon, they can dig up enough thorium to produce 1 GWe for a year. Thorium in easily recoverable amounts is found in mine tailings, thus we don't need new thorium mines to produce it, we can simply scoop up thorium that is already on the surface. Even in seemingly small concentrations the energy recovery potential from thorium is such, that the energy investment required to bring about that recovery is worth while.

There would not seem to be any potential impediments to the Liquid Fluoride Thorium Reactor solution to our energy issues. They can be built in large numbers in factories. Small LFTRs are efficient and easily transported. They can be set up anywhere. The do not require water for cooling, they can be cooled with air. They are not good nuclear proliferation tools. They are safe. Their materials output is safe after 300 years, and need not be considered waste.
What is wrong with the LFTR? Some money needs to be spent on their development. A crash development program that cost less than what is spent on the NASA Space program in a year would probable come up with a commercial LFTR model in 5 years or so. Thus considering the enormity of the energy challenges we face, the LFTR provides a doable solution.

So called energy experts claim that there is no such thing as a silver energy bullet, but there is a thorium bullet, and we have every reason for using it. Small Liquid Salt Thorium cycle reactors hold amazing promise for solving the energy problems that confront us during the next 40 years.

1 comment:

Laurence Aurbach said...

Well stated, Charles. Every study and forecast I have seen indicates we need to be thinking in terms of thousands of reactors to truly replace fossil fuels. If they are mini or micro reactors, we need to be thinking on the scale of tens of thousands. Obviously, mass production is the only way to accomplish such a goal.

Along with the engineering and financial planning, we (meaning governments, industry and citizens) need to develop the management and administrative plans for such a scheme. Even if the engineering is perfect, it would be wise to assume that mistakes will always be made, that there will always be temptations to cut corners in construction and operations. So it's vital to think about how such a hugely expanded nuclear sector should be managed to ensure adequate safety, efficiency, security, and control of expenses at all stages. It would be helpful to hear input from experts in large-scale program management, regulatory administration, and organizational psychology. The experience of the French nuclear bureaucracy would be particularly relevant.

I have the feeling that management and bureaucracy makes a lot of people's eyes glaze over, but it's no less essential than engineering.


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