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Peter Ottensmeyer's picture
Peter Ottensmeyer
Mar 8, 2021 - 13:40

It is easy to throw one’s hands in the air in dismissal. It is more difficult to arrive at solutions that work.

Canada’s 60,000 tons used nuclear fuel comes has three flavours which can be separated by available recycling approaches such as pyroprocessing, with minimal left-overs (Till and Chang, Plentiful Energy, Amazon).

The largest separated part would be uranium, at 98.85% (59,300 tons), that is no more radioactive than natural uranium and therefore requires no more shielding during storage than natural uranium. That takes care of the bulk of the mass, a major reduction wrt "waste".

The second part is composed of 0.74% (440 tons) fission products, atoms that are about half the size of uranium, that result when uranium is split in the reactor to extract its energy. About 70% of these are non-radioactive immediately, while the rest have short half-lives of days, weeks or months. Only two types of atoms out of several hundred types have half-lives as long as 30 years, Sr-90 and Cs-137. About half a dozen have very long half-lives, and as a consequence have radioactivity levels less than the uranium from which they were created. These atoms, platinum-group metals and rare earths among them, require shielded storage over a short term, since they turn into valuable non-radioactive atoms and minerals worth about $ 3 million per ton.

The third and final part is composed of about 0.4% (240 tons) so-called transuranic actinides (TRUs), atoms heavier than uranium created in the reactor. They have long half-lives, with their radioactivity not returning to background uranium levels for close to a million years. It is these atoms in the used CANDU fuel “waste” that are the prime reason for a long-term DGR. However, almost 75% of them are fissile fuel atoms that are excellent starting fuel for the small modular reactors considered for Canada, all of which require enriched fissile fuel to operate. Consuming such TRUs from used CANDU fuel “waste” in such reactors serves at least two useful purposes. It eliminates their long-term radiotoxicity from the used fuel stockpiles, and they provide Canadian fuel for such SMRs, which otherwise would have to be imported from nuclear weapons states at twice the price (Ottensmeyer, NWMDER Conf., Ottawa, 2019).

Thus minimization occurs in several ways: 1) most of the bulk, over 59,000 tons of recovered uranium, goes into storage as fuel replenishment for SMRs, 2) the long-lived TRUs go into the well-shielded SMR reactor cores as fuel. Only the 440 tons of fission products require relatively short-term shielded storage until they too became non-radioactive valuable atoms and minerals. That’s quite a reduction from the current 60,000 tons. Moreover, the very slightly used CANDU fuel is once again regarded as the exceedingly valuable fuel that it really is, at 200 MeV of non-carbon energy from each and every heavy atom.

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