Thorium reactors. Do they exist? Are they still just theoretical? Why aren’t we investing more in it?
In: Chemistry
They only exist in research labs, there are some national and commercial investments, some in the US but most in China, trying to develop a commercially viable reactor. I, for one, don’t expect any of them to succeed. Ever.
The problem no one ever talks about is Protactinium.
You see, Th-232 isn’t nuclear fuel, but fuel stock. You use it to breed U-233, and THAT produces the fission, the heat, the steam, etc. But to get U-233, you must first produce Pa-233.
So the process is: Th-232+n -> Pa-233 -> U-233
Pa-233 has a half-life of 27 days. This is important, you can’t leave this stuff in a reactor or it will pick up neutrons and become something else, it has to be extracted. This is why Thorium research is all around MSRs, because if you’re going to have any chance of extracting Pa-233 economically and in time, you’re going to liquify your fuel.
So what’s the catch? 1g of Pa-233 has a radioactivity of 769 TBq and a dose rate of 20,800 mSv/h. Still don’t get it? The legal whole body exposure limit is 1 mSv/yr.
Think this through: if you have to replace a pump, an there’s 1 mg of Pa-233 left on the equipment, the technicians will receive their annual dose in under an hour. If you have any leak in the system, you can’t go in and fix it for MONTHS, and you’ll have lost revenue the whole time.
It’s not that the theory isn’t sound, it’s the very practical, tangible, physical, engineering constraints that will make this impossible. You have to actually build the thing, which is the easy part, but then you have to maintain it. With people. And you just can’t. The theoretical operating costs and revenue losses kill thorium reactors.
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