The fundamental critical issues of current nuclear energy production plants are notoriously represented by:

i) - excessive initial construction costs,
ii) - long construction times with unsustainable financial costs,
iii) - high operating and maintenance costs,
iv) - safety concerns regarding accidents,
v) - need for safe storage of radioactive waste in the very long term.

The panacea to these problems would be represented by the design and construction of Small Modular Reactors (SMR), a maximum of 300 MW, which would be built and assembled in the factory and then transported to the site ready to come into operation.

Nuclear power plant developers and vendors promise that these technologies will reduce financial burdens, safety costs and waste reduction associated with larger nuclear power plants operating at GigaWatt scale.

But spent fuel and radioactive waste are the Achilles' heel of SMRs.

In a substancial article published in the Proceedings of the National Academy of Sciences (PNAS), entitled “Nuclear waste from small modular reactors”, scientists from Stanford University and the University of British Columbia analyzed the management and disposal of nuclear waste streams produced by SMRs, reactors that are attracting attention due to claims of inherent safety features and reduced costs.

The authors made a detailed assessment of the impact of SMRs on the management and disposal of nuclear waste compared to that generated by larger commercial reactors of traditional design. Developers and proponents of nuclear technology often use simple metrics, such as bulk or total radiotoxicity, to suggest that advanced reactors will generate less Spent Nuclear Fuel (SNF) and less High Level Waste (HLW). ) compared to a GigaWatt-scale pressurized water reactor such as the “PWR – Pressurized Water Reactor,” the prevalent type of commercial reactor today.

The analysis results reveal that SMRs design, compared to GigaWatt-scale PWRs, will increase the equivalent volumes of nuclear waste requiring management and disposal. In particular, volumes of spent nuclear fuel (SNF) will increase by a factor of 5.5; the volume of high-level waste (HLW) will increase by a factor of 30 and finally the volume of low- and intermediate-level waste (LILW) will increase by a factor of 35.

The authors also argue that the volume of waste is not the most important evaluation parameter, but that it affects the performance of the geological repository, which is influenced by the thermal decay power and radiochemistry of the spent nuclear fuel, so SMRs provide no advantage.

Furthermore, SMRs will not reduce the generation of geochemically mobile fission products such as ¹²⁹I, ⁹⁹Tc, ⁷⁹Se, which are important contributors to the doses of radioactivity emitted and which must be taken into account in the design of geological repositories.

Furthermore, spent fuel from SMRs will contain relatively high concentrations of fissile nuclides, requiring new approaches to assess critical issues during waste storage and disposal.

Finally, because waste stream properties are affected by neutron leakage, the basic physical process that is enhanced in small reactor cores, SMRs, ultimately, will exacerbate the challenges of nuclear waste management and disposal.