Lindsay Krall1,2,Allison Macfarlane3,Rodney Ewing4
Stanford University (former)1,Swedish Nuclear Fuel and Waste Management Company (current)2,The University of British Columbia3,Stanford University4
Lindsay Krall1,2,Allison Macfarlane3,Rodney Ewing4
Stanford University (former)1,Swedish Nuclear Fuel and Waste Management Company (current)2,The University of British Columbia3,Stanford University4
Small modular reactors (SMRs, <i>i.e.,</i> nuclear reactors that produce <300 MW<sub>elec</sub>, each) have attracted considerable attention because of inherent safety features and reduced cost, but there are remarkably few studies that analyze the impact of SMRs on the back-end of the nuclear fuel cycle, specifically with respect to changes in waste stream management and disposal. Here, we characterize the notional high-, intermediate-, and low-level waste streams for three, distinct SMR designs in terms of volume, (radio)chemistry, decay heat power, and fissile isotope composition<sup>1</sup>. Results reveal that the analyzed water-, molten salt-, and sodium-cooled SMR designs will increase the energy-equivalent volume of nuclear waste in need of management and disposal by two- to thirty-fold relative to an 1100 MW<sub>elec</sub> pressurized-water reactor. Much of the excess waste volume is attributed to the use of neutron reflectors and/or of chemically reactive fuels and coolants in SMR designs. That said, volume is not the most important parameter for assessing the implications for storage and disposal of a nuclear waste stream; rather the critical issues in the performance of a geologic repository are driven by the decay heat power and the (radio)chemistry of the spent nuclear fuel. SMRs provide no benefit for these two important parameters. For instance, SMRs will not reduce the energy-equivalent generation of geochemically mobile <sup>129</sup>I, <sup>99</sup>Tc, and <sup>79</sup>Se fission products—important dose contributors for various repository designs—relative to a full-scale commercial reactor. Instead, SMR spent fuel will contain relatively high concentrations of fissile nuclides and, therefore, will demand the development of novel approaches to criticality safety during storage and disposal, including increased handling, treatment, and conditioning operations. Since the properties of the waste streams are influenced by neutron leakage, a basic physical process that is enhanced in small reactor cores, SMRs will exacerbate the challenges of nuclear waste management and disposal.<br/><br/><sup>1</sup>Krall, L.M., Macfarlane, A.M., Ewing, R.C. (2022). Nuclear waste from small modular reactors. <i>Proceedings of the National Academy of Sciences. </i>119(23).