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There had been an immense amount of hype, and considerable nonsense written about Small
Modular Reactors. When you are trying to solve a problem as big as the Gordian knot, the
closely coupled issues of electricity poverty and planet heating, small is not beautiful. There
are strong economies of scale in nuclear power generation. Any solution that does not recognize
this will be hopelessly wasteful. But it is also true that we must take advantage of the order of magnitude improvement in productivity and quality associated with assembly line manufacture,
as compared to conventional on site construction. What we need is Big Modular Reactors,
the biggest reactors we can build on an assembly line.
Hi Jack. Thanks for your work. I find it very informative.
I would like to ask 2 question that maybe you can address in future writings.
Q1). with regard to radiation, I understand the distinction between alpha, beta and gamma radiation. However I never hear about
neutron radiation or neutron flux and its effects. Why is that? Inside the reactor, neutron flux and neutron damage is important and it
would seem to be a type of ionizing radiation — but it is not listed in the trilogy.
Q2). With molten salt reactors, I have heard the claim that in the case of a plumbing failure and release of primary (radioactive) molten salt, the salt is chemically stable and will freeze into a solid that will prevent radioactive elements from being transported or from reacting with the environment. This seems very plausible. Since many salts are very soluble in water, my question is: With the salts used for molten salt reactors, can the radioactive solid salts be dissolved in water and transported into waste water, rivers and oceans?
Many thanks.
Paul (pymont@gmail.com)
Paul,
Two good questions.
Neutrons are indeed ionizing radiation. In fact, because of their mass and lack of charge,
they are both damaging and penetrating. Their Sv/Gy ratio is about 10. And they totally dominate
the flux produced by an operating reactor. Reactor shielding is all about neutrons.
However, as soon as the chain reaction stops either because the reactor has been shut down
or blown itself apart (Chernobyl), the neutron flux stops very quickly. As a result, neutrons have
been a non-factor in all the releases to date, and almost certainly will be in future releases,
at least as far as the public is concerned. The Flop book tries perhaps too hard to keep things
as simple as possible, so it does not get into neutrons.
BTW, neutrons do have to be considered in dry cask design, thanks to the spontaneous fission
of Cm. But the neutron decay is faster than the fission product gamma decay, so The Flop
glosses over this as well.
Fluoride salts do not react with water. ORNL actually did an experiment where they threw
something like 100 kg of molten salt into a tank full of water and all they got was vigorous boiling. MSR’s where there is the possibility of mixing water and salt have to be prepared to handle this steam.
Fluoride salts are soluble in water, some such as CsF, highly so. If the salts
are released into a body of water, the amount of dilution and the shielding properties
of the water will determine the dose rates, etc. You have to work out the plume calcs, etc.
I think you will find that for any sizable body of water, the area of detectable harm will be small.
Detectable harm is totally different from detectable radiation, a point The Flop makes over and over, ad nauseum.
BTW, the idea that the salt will quickly solidify is in my view misleading. In the design, I’m
most familiar with the time between a drain and the salt starting to solidify is about 3 weeks.
This is because of the decay heat. And in a way it is a plus. We need the salt liquid, so we can move it around.