Partial Defect Testing of Pressurized Water Reactor Spent Fuel Assemblies

In our earlier papers we have reported a development of a novel technology to detect diversion of spent fuel from pressurized water reactor (PWR) spent fuel assemblies. The concept of spent fuel partial detection technology lies in the effective evaluation of thermal neutron and gamma signals measured inside guide tube holes of the PWR spent fuel assemblies. One of the key features of the data evaluation method is the concept of the base signature obtained by normalizing the ratio of gamma to neutron signals at each measurement position. As the base signature is relatively invariant to the characteristic variations of spent fuel assemblies such as initial fuel enrichment, cooling time, and burn-up, the methodology can be an extremely powerful tool that does not require operator declared data and can be used without moving the fuel from the storage rack in the pool. For the hypothetical case of a symmetric diversion, separate analysis can be applied using already available individual normalized gamma or neutron signature profiles. In this paper we report results from an experimental campaign conducted on PWR spent fuel assemblies which cover Westinghouse type 14x14, 16x16 and 17x17 fuel product lines, and their analysis. The experiments demonstrated the validity of the verification methodology. Thus, the envisaged PDET system would be a new powerful safeguards tool which does not require any operator provided data and that can potentially detect as low as 10% missing pins in an in-situ condition.