Thursday, March 26, 2009

Nuclear Green and the Big Lots Reactor

I created Nuclear Green to voice things that need to be said. I had come to Nuclear Blogging through a long and unusual route that went back into my childhood. The route was part of the story. But there was more than that. I had concluded that we, as a civilization, faced a serious crisis involving future sources of energy. The term energy crisis is not new, and there would be no resolution of the energy issue until the human community could settle on a long term energy source that would not threaten life on this planet. I already knew the answer a long time before I started thinking about the problem in 2007. It was simply a matter of applying what I knew. The primary candidates for to replace fossil fuels were wind, solar and conventional nuclear. I asked the most simple and obvious question first. Where do you get electricity once the sun goes down or the wind stops blowing. Well after dark, electricity is suppose to come from wind, and the wind is only going to stop blowing only in the day time, renewables advocates like David Roberts and Joe Romm told me in 2007. Other renewables advocates told me that all of the problems would be solved with extra large rechargeable batteries, pumped storage and compressed air. When I read about those and other energy storage solutions I quickly concluded that they were not ready for prime time. That meant that renewables, always at the beck and call of mother nature, were not ready for prime time either.

The big complaint about conventional nuclear is that Light Water Reactors are very complex. It takes a lot of work to build them. Millions of hours of work. Millions of hours of work translates into building projects that stretch out for several years. Henry Ford has the solution to building reactors more quickly and with fewer hours of work a century ago. Reactors had to be built on the assembly line and made simpler. It was absurd to think you could transport a 1 GW light water reactor from a factory to its building site, but the Molten Salt Reactor was much smaller and lighter than a LWR. I knew about the MSR because my father had worked on it over a nearly 20 year period at ORNL. MSRs were also more efficient than LWRs. It was my idea then to build relatively small - small for the sake of easy transportation - Molten Salt Reactor (LFTRs) in factories. I do not claim originality for the factory manufactured small reactor idea. Later I was to add other unoriginal components to the mix, underground housing, and recycling coal fired steam plant sites, for LFTR localities. All in the name of cost lowering.

I also focused on cost lowering with the Big Lots Reactor. I do claim the Big Lots Reactor idea was original. The most important concept in the Big Lots idea is the notion that the LFTR is good business. A manufacturer can build thousands of them and make money on every one. Utilities that buy them will make money too, and the public will get low cost reliable electricity. No one loses. The best thing that could happen to the Big Lots idea is that someone will see it as an opportunity to get rich and take advantage of it. Not the government, but someone who wants to get rich can make the Big Lots Reactor happen.


Bobcat said...


Quick question for you. I have read in the Wall Street Journal that some thermal power plants are having difficulty because of water concerns.

You can view that article by clicking on the link below.

My question is how do Liquid-Fluoride Thorium Reactors do with water consumption? If water consumption is less than other types of power plants then that will be a major selling point, especially out here in the arid west.

Charles Barton said...

Bobcat, LFTRs can be either air cooled or water cooled. One advantage of relatively small reactor size, is less coolant is needed for each reactor, Because LFTRs have greater thermal efficiency, they need less coolant pewer unit of power output as well. It should be noted that the water shortage problem effects all thermal power sources. This would include solar thermal power which uses as much water as conventional nuclear plants. Water shortages in the southwest would be a serious difficulty for solar thermal facilities, because they require the desert environment. Solar voltaic facilities may not use water, although cooling PV panels does increased their efficiency.

Anonymous said...


As a matter of fact, as small LFTRs are very cheap fuel-wise, optimal thermodynamic efficiency is not necessarily an issue. So, in dry locations, why not use aeroderivative turbines with a salt/air heat exchanger on the secondary loop? No cold source issue.

It would be a return of sorts to the first MSR of all, the Aircraft Reactor Experiment and the original MSRE itself was air cooled and never had problems with its salt/air exchangers properly said.

donb said...

To extract energy from a heat source, there also needs to be a heat sink. If the heat source is hotter, the heat sink can also be hotter and still maintain efficiency. Maximum theoretical thermodynamic efficiency is given by:
[T°hot - T°cold]/T°hot
where both temperatures are absolute (either Kelvins or degrees Rankine).

Conventional reactors use a steam cycle, which has limits on the hot side. In addition, the steam is condensed to water on the cold side. It is a whole lot easier to condense steam using cooling water (as opposed to dry air), since water can absorb a lot of heat, and conducts heat very well in a heat exchanger (water is much denser than air). At cooler condensing temperatures, the steam condensor will pull a vacuum (as opposed to needing pressure to force the steam to condense). Having a vacuum at the outlet of the steam turbine allows the turbine to extract more energy from the steam.

There are several ways one might run a LFTR. The most efficient way is to take advantage of it higher output temperature by using a Brayton cycle, where the heat transfer and work is done by something that stays in gaseous form (e.g., helium) at all points. Starting with such a high T°hot allows the plant designer to dump the waste heat to a higher temperature sink like hot, dry air, and still maintain good efficiency.

Conventional reactors have limits on the hot side. Due to the relatively poor heat transfer between the oxide fuel pellets and the outside of the fuel rods, the hot side temperature as seen by the water is lower than what is seen in coal fired plants, so efficiency suffers. Repowering an existing plant by substituting a LFTR for the coal-fired boiler, while not the most efficient, is actually a rather good plan (more efficient than conventional nuclear, re-uses the rest of the infrastructure).


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