Antineutrino Monitoring of Thorium Reactors

TL;DR

This study estimates the antineutrino spectrum from thorium molten salt reactors and evaluates the feasibility of detecting U-233 diversion, finding current methods are insufficient for timely detection within IAEA standards.

Contribution

First estimation of the antineutrino spectrum from U-233 fission and assessment of detection feasibility for diversion scenarios in thorium reactors.

Findings

U-233 antineutrino spectrum estimated for the first time

Detection of 8 kg U-233 diversion exceeds current IAEA timeliness goals

Current antineutrino monitoring methods are insufficient for timely diversion detection

Abstract

Various groups have demonstrated that antineutrino monitoring can be successful in assessing the plutonium content in water-cooled nuclear reactors for nonproliferation applications. New reactor designs and concepts incorporate nontraditional fuels types and chemistry. Understanding how these properties affect the antineutrino emission from a reactor can extend the applicability of antineutrino monitoring. Thorium molten salt reactors (MSR) breed U-233, that if diverted constitute a direct use material as defined by the International Atomic Energy Agency (IAEA). The antineutrino spectrum from the fission of U-233 has been estimated for the first time, and the feasibility of detecting the diversion of 8 kg of U-233, within a 30 day timeliness goal has been evaluated. The antineutrino emission from a thorium reactor operating under normal conditions is compared to a diversion scenario by evaluating the daily antineutrino count rate and the energy spectrum of the detected antineutrinos at a 25 meter standoff. It was found that the diversion of a significant quantity of U-233 could not be detected within the current IAEA timeliness detection goal using either tests. A rate-time based analysis exceeded the timeliness goal by 23 days, while a spectral based analysis exceeds this goal by 31 days.