Conceptual Development of Remote Monitoring System for PWR Spent Fuel Dry Cask Storage

Abstract:

The International Atomic Energy Agency (IAEA) needs to enhance its capabilities for safeguarding spent nuclear fuel (SNF) stored in dry cask storage facilities and for maintaining persistent continuity of knowledge (CoK) about it. Current safeguards approach relies heavily upon containment and surveillance measures, where seals are placed inside and outside the dry cask. The disadvantage of this approach is that, if a seal is broken, no method exists currently to verify the dry cask content other than opening it and checking the internal seal and the SNF from inside. This study focused on the development of remote monitoring system (RMS) for dry cask storage which is capable of detecting neutron and gamma radiation emitted by the SNF and the signal thus generated can then be continually transmitted to the IAEA to maintain the CoK about the dry cask contents. The remote option was chosen after reviewing the current IAEA needs. The IAEA requires new safeguards systems to be remote, cheap and robust. Computational approach was used to develop the proposed RMS. Monte Carlo N Particle transport code (MCNP) was employed to develop a dry cask model with 32 SNF assemblies inside. ORIGEN-ARP fuel burn-up and depletion code was used to generate radiation source-term. A series of MCNP simulations as well as analytical calculations were performed to investigate the neutron and gamma flux behavior inside the dry cask. The results of these simulations and analysis aided the design of the RMS and determination of the optimal location for its components. The RMS was placed inside the dry cask on the top of multi-purpose canister (MPC). The final conceptual design of the RMS included two fission chambers (to detect neutrons) and one ionization chamber (to detect gamma radiation) enclosed in a polyethylene box with a thin cadmium plate separating chambers from the polyethylene bottom layer.