The wrong answer in this case is quite shoddy indeed. Terrestrial Energy's rebuttal is scathing. For example The authors then quote a value of greater than

The wrong answer in this case is quite shoddy indeed. Terrestrial Energy's rebuttal is scathing. For example The authors then quote a value of greater than 10^12 n/cm2-sec as the IMSR’s thermal flux reaching the vessel; they conclude this will make the used vessel very radioactive. However, they reference a university paper (REF 29), whose authors clearly state they are unfamiliar with the IMSR design and that they merely made assumptions to do their modeling. There are lots of other inaccuracies. Here's another quite grievous mistake. The whole assertion that SMR's produce "increase the volume of nuclear waste in need of management and disposal, by factors of 2 to 30" relies in the calculation for sodium-cooled reactors, where the factor was found to be 30. For all other reactors, the factor was 5 or less. Now, for sodium-cooled reactors, their claim is that the vast majority of the waste (about 75%) is the sodium itself: Ultimately, the sodium coolant generated several hundred cubic meters of low-level radioactive waste. The 30-MWth Toshiba 4S reactor might generate 115 m3/GWth-y of contaminated pyrophoric sodium coolant in need of treatment, conditioning, and disposal. They forget to mention how low level the radioactive waste is. Fortunately, wikipedia gives us the answer [1] Sodium has only one stable isotope, sodium-23. Sodium-23 is a weak neutron absorber. When it does absorb a neutron it produces sodium-24, which has a half-life of 15 hours and decays to stable isotope magnesium-24. So those 115 cubic meters of waste become completely non-radioactive after one month. [1] https://en.wikipedia.org/wiki/Sodium-cooled_fast_reactor https://en.wikipedia.org/wiki/Sodium-cooled_fast_reactor