New monitoring technique could catch secret fuel swaps in small nuclear reactors
Researchers have validated a method to detect unauthorized changes to reactor fuel by measuring neutron leakage patterns—offering a low-cost way to verify nuclear safeguards without human inspection. The technique could become critical as small modular reactors proliferate globally, reducing reliance on on-site monitoring and cutting operational costs for both utilities and regulators.
Originaltitel: Simulation of Neutron Leakage Variations at Fuel Substitution in a Small Modular Reactor and Implications for Unattended Safeguards Monitoring
<p>According to a recently proposed nuclear safeguards technique, monitoring the power-normalized, ex-core neutron detection rate over time could be used to detect undeclared changes to the fissile composition of a reactor core. In this study, Monte Carlo simulations have been used to verify some of the underlying assumptions of this technique and the possibilities of using it to detect undeclared fuel substitutions during the first 2-year cycle of a light water small modular reactor. Depletion calculations and neutron transport simulations were used to study the changes in the power-normalized neutron leakage rate 𝐽b/𝑃core through the core barrel upon fuel substitutions and whether these changes are fully explained by changes in the core fissile composition. Several substitution scenarios have been studied, where partially depleted fuel assemblies were substituted with fresh fuel assemblies after 1 year of irradiation.</p>