A Prediction and Verification Methodology for Small Modular Reactor Safeguards

Abstract

The paper proposes a prediction and verification methodology that provides an independent verification of declared small modular reactor (SMR) operating conditions, and therefore fissile material content, for safeguards purposes. This methodology consists of high-fidelity simulations of “indicating parameters” (e.g., neutron flux profiles outside the primary reactor system) coupled with off-line neutron dosimetry of retrievable verification specimens. The methodology is intended to detect erroneous reporting and/or undeclared activities during reactor operation, through discrepancies between simulated and measured indicating parameters, confirmed by offline dosimetry of verification specimens. The indicating parameters are simulated using the Monte Carlo reactor physics code SERPENT. The proposed prediction and verification methodology is demonstrated on a small modular fluoride-salt-based molten salt reactor (sm-FMSR) and a micro- sized high-temperature gas-cooled reactor (m-HTGR). The results show that the flux profiles outside of the reactor primary system, which are unique in value and trend for different SMR designs, are effective indicating parameters for reactor operating conditions. With verified operating conditions, one of the most important nuclear safeguards parameters, the fissile material content in the reactor, can be determined.