Re-establishment of the continuity of knowledge in the safeguards of interim storages using NDA techniques

This paper aims to provide an answer to the question: is it possible to detect the diversion of a fuel assembly from a Castor container by means of passive neutron measurements?Monte Carlo simulations performed on suitably validated models suggest a correct way to tackle the problem with success perspectives.Under the assumption of ideal boundary conditions, that is neglecting the effects related to the presence of other canisters and of the environment surrounding the cask, we have demonstrated that it is possible to establish a sort of “fingerprint” of a sealed Castor cask. This fingerprint could be used for future verification of the integrity of the cask in order to re-establish the continuity of knowledge in case of failure of the C/S measures.In particular we have shown that it is possible to detect the removal of a PWR bundle from a Castor V21/A cask by means of passive neutron measurements, only if the removed bundle was originally located in peripheral positions of the fuel basket grid.