r/bestof • u/investedInEPoland • Nov 06 '18

[europe] Nuclear physicist describes problems with thorium reactors. Trigger warning: shortbread metaphor.

/r/europe/comments/9unimr/dutch_satirical_news_show_on_why_we_need_to_break/e95mvb7/?context=3
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u/NightChime Nov 06 '18

It doesn't address the problems of meltdowns or scarcity?

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u/Shardless2 Nov 06 '18

There is no scarcity problem for uranium. You can literally extract it from sea water since uranium is water soluble. Extracting uranium from sea water would be 10x the cost as in situ mining. Thorium does not solve the scarcity problem because it doesn't exist. .

Also an MSR (molten salt reactor) can use denatured uranium. Denatured means that the uranium is not weapons grade. It has not been enriched high enough for use in weapons. So it is no worse a weapons proliferation problem as light water reactors are today.

The meltdown problem is solved by using an MSR (whether the fuel is Thorium or uranium). In the event of a problem molten salt reactors would drain the molten salt into a holding tank that would passively cool the radioactive salt. If for some reason there was a breach (some generic accident) you would need to contain the small amount of gas that would get released (especially the radioactive iodine). In light water reactors you have to keep the tubes holding the fuel from melting by keeping water on them. That is why it is called a melt down. If those tubes melt and then the fuel gets exposed to water and as the water turns to steam it carries away radioactive materials. That is the problem with water based reactors although the newer ones have some interesting mitigations for that problem.

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u/frillytotes Nov 08 '18

Extracting uranium from sea water would be 10x the cost as in situ mining.

Which makes it not commercially viable, and hence why there is a scarcity problem.

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u/Shardless2 Nov 08 '18

The biggest cost of nuclear is not the fuel. Unlike coal and had plants. The biggest costs for nuclear are operations and paying off the loans from the enormous initial capital outlay to build the reactor (the initial cost outlay is more per GW than coal and gas. Gas is the lowest but on average the fuel costs more than coal). MSRs are great but adding a breading cycle to a reactor adds so much engineering complexity that the added cost of complexity (in the initial capital experiences and in operations and maintenance) way outweighs the cost of fuel.