Atomic Show #178 – Nuclear Process Heat
One of the persistent myths left over from the first Atomic Age is that nuclear reactors can only be used to produce electricity in massive, central station power plants.
That application is only one of many ways to use the heat from fissioning uranium, plutonium or thorium. In the US, fully 1/3 of the 100 quadrillion BTUs (Quads) of energy used each year is consumed by industrial process heat applications. Nearly all of that is supplied by burning hydrocarbons (some is supplied at paper mills and lumber processing plants by burning biomass).
With some clever engineering that takes advantage of research initially conducted to attempt to enable solar heat to be made available when the sun is not shining, Cal Abel is working on ways to produce, distribute or store nuclear fission heat.
We are joined in our discussion by Bob Apthorpe, another man with a degree in nuclear engineering from the University of Wisconsin, the same place where Cal earned his BS and MS.
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There is another myth that nuclear power process heat. That is that the reactor has to be at process heat temperatures to be useful for process heat. This is not necessarily true. There are a slew of patents that seek to “amplify” nuclear heat to be used in process heat applications. Most of these are centered around HTGR’s (High Temperature Gas Reactors).
In the podcast, I talked about reactors that were much cooler, with core outlet temperatures around 500 C. I added to the slew of patents out there and designed a heat pump system (like what we use in the south to heat our homes in the winter except it uses S-CO2). My design will take 450C reactor outlet and raise it to 820C which is hot enough to gasify coal or anything else that contains carbon.
A lower temperature reactor is easier and generally more inexpensive to build. That and the US-DOE has a lot of history with reactors operating <650C and is where most Gen-IV reactors are anticipated to operate, at least in their first incarnation.
The concept of rolling reserve is vastly different under the energy storage situation. The rolling reserve is only constituted in pipes, heat exchangers, heat rejection, and a very small brayton heat engine. The construction is entirely non-nuclear and can be modularized so the construction costs would be on par with a combustion turbine (heat exchangers are what are really expensive and drive cost differences)
1 m^3 of solar salt (costing $949 one time capital investment) can hold 190 kW-hr(t) (500C-260C) or 70 kW-hr(e) (38%) on a per dollar and per pound basis, there is not much out there that can come close to matching this. See reference below table 2:
http://pointfocus.com/images/pdfs/saltw-troughs.pdf
Back of the envelope a 10m diameter by 10m thermos of solar salt can hold 55 MW-hr(e). TVA would need approximately 24,000 MW-hr(e) storage per day of energy storage capacity, roughly 430 flasks (758 m^3 each) (not counting pumped hydro), a 340 million dollar investment in salt. The thermoses (need twice the volume of thermoses for given volume of salt) and the pipes will add significantly to this cost, but will be on the same order of magnitude. Couple that with a heat source that is ~$30/MW-hr(t) and the price of electricity will drop and become very elastic which is good for the consumer and our economy.
Maybe this is too obvious: Why not have an industrial park near a nuclear power plant and pipe the heat after the turbine over to the businesses? Is there some reason that would not be possible?
TVA thought of doing that with Watts Bar. The quality of the heat, temperature, is very important for the type of industrial use. Thus the hotter the better. Waste heat does have industrial applications, but they are generally limited.
The main reason why this is not being done is due to a policy constraint of the NRC, where everything that is located next to the reactor has to be evaluated and everything that comes in contact with the reactor that could have an effect on reactor power must be controlled. This constraint has almost single handedly prevented the use of waste heat at existing LWR’s and has driven a large amount of the capital cost of the steam plant. One can’t just take a steam plant from a coal power plant and hook it up to a reactor, it does not have the necessary pedigree to do so. Obtaining that pedigree is very expensive and takes a long time even though the materials and construction techniques are almost exactly the same.
My goal with this concept is to assuage the concerns of the NRC over power feedback from the process loads using the time delay of the storage, and then with the blast wall provide a physical barrier that will protect the reactor from any potential missile hazards (e.g. a turbine spinning at 2000 rpm disintegrating) or an overpressure event (a chemical explosion in the process yard).
Cal i have recently read about new way to split water using heat: http://www.zeitnews.org/energy/caltech-chemical-engineers-devise-new-way-to-split-water.html; maybe this will be interesting for you.