Spent nuclear fuel management: new approaches to evaluating radiotoxicity of long-lived high-level nuclear wastes of fast reactors

In this paper, radiotoxicity of long-lived high-level by-products arising from spent nuclear fuel from BREST-OD-300 is considered in terms of radiological equivalence between lifetime radiation-associated risks for human health from the nuclear wastes and natural uranium (radiological equivalence), as well as radiation equivalence between committed effective doses from the wastes and natural uranium (radiation equivalence). Detailed analysis of the above equivalences is given in previous papers. The toxicity level is measured by time period between unloading the spent nuclear fuel and the equivalence achievement time. The most effective method for reducing committed effective doses is partitioning and transmutation (P&T) of americium, Am, use and holding cesium, Cs, and strontium, Sr, 70-year holding curium, Cm, followed by plutonium partitioning. According to calculations, radiological equivalence is achieved about 3 times earlier than radiation equivalence. Twenty seven scenarios of nuclear spent fuel removed from the BREST-OD-300 management was considered. The shortest period between unloading the fuel and radiological equivalence achievement is in case when the waste consists 0.1% of Am and 100% of Cm, and 95% of fission products Cs, Sr, Tc, I are removed. Due to uncertainty in radiation risks estimates, radiological equivalence achievement period increases when radiation risks for Russian young adults are assessed. If adults aged 20 years are considered achievement period can increase from 184 to 210 years (the upper endpoint of 95% confidence interval). To estimate radiological equivalence achievement time for children further research is needed.