Antineutrino Detection for Safeguards: Concepts and Feasibility for Storage Facilities

Nuclear power plants generate spent nuclear fuel (SNF) during operation. This spent fuel requires long-term safeguarding during interim storage and final disposal to ensure the non-proliferation of fissile materials. These safeguards measures for spent fuel storage facilities (SFSFs) include a combination of material accountancy, containment and surveillance (C/S), and design information verification (DIV), combined with regular inspections to verify declarations at random intervals.

In recent years, antineutrino detection techniques have been proposed and prototyped for reactor safeguards, utilising the antineutrino emission from the continuous beta decay of fission fragments within nuclear fuel. One of the key features of interest is the ability of antineutrinos to pass through dense material - such as shielding, facility walls or geology - unhindered. The detection techniques employed for reactor antineutrinos can also be adapted to SNF but due to the extended cooling time of SNFs the antineutrino flux tends to be lower by two or more orders of magnitudes and the emitted lower in energy, requiring adaptation to the facilities and scenarios in question.

In this study, the antineutrino emissions of SNF are simulated and modelled for a range of different SNF ages and distribution in SFSFs to determine the expected signal in various types of detectors, including scintillation detectors and time projection chambers (TPCs) filled with liquid organic (LOr) target media. Using this simulation framework, various levels of background activity are analysed to estimate detector sensitivity in various usage scenarios, including passive continuous monitoring, re-verification of facilities or specific containers. This study then compares the feasibility of antineutrino-based detection approaches and formulates minimum technical requirements (e.g. background levels, detection efficiency) required for the safeguards monitoring of SNF.