Year
2013
Abstract
The diversion of spent nuclear fuel (SNF) is one pathway to acquire a nuclear weapons capability. There are few places where it can be obtained: nuclear reactor core, SNF wet storage, SNF dry storage and during SNF transportation. Different types of safeguards tools are available to monitor fuel inside the core and storage pools. However, once SNF is removed to dry storage, there is no non-intrusive option to verify individual SNF assembly attributes. Moreover there is a lack of efficient safeguard tools for re-verification of dry cask content. The International Atomic Energy Agency (IAEA) wants the future safeguards systems to be remote in an effort to reduce the number of on-site inspections wherever possible. Thus, this study focuses on the development of the conceptual design for a remote monitoring system (RMS) that would be able to detect neutron and gamma signals coming from SNF and detect removal of both central and peripheral SNF assemblies from a dry cask. A computational approach was used to develop the proposed RMS. MonteCarlo N-Particle transport code (MCNP) was employed to develop a dry cask model. The ORIGEN-ARP fuel burn-up and depletion code was used to generate a radiation source term. A series of MCNP simulations were performed to investigate the neutron and gamma flux behavior inside and outside the dry cask. The results of these simulations aided the design of the RMS and determination of the optimal location for its components. The proposed RMS design was tested through SNF diversion analysis, and it was able to detect all considered diversions with a non-detection probability less than 5%. It was also shown that the false alarm probability could be reduced to 1% with an increase of measurement time, which will yield a non-detection probability of essentially 0% for all considered diversion scenarios. In addition to remote operation, the choice of the detectors and simple operation principle ensures system robustness and easy signal processing.