Core Inventory Verifier for Research Reactors

The Core Inventory Verifier (CIVR) is an indirect quantitative method for core inventory verification. For the reactor under inspection, which is considered as a ‘Black Box’, the kinetic behaviour, neutron flux distribution and neutron spectra are measured and compared with a set of reference data taken earlier (fingerprint).The conclusion ‘Nothing has changed’ indicates that all expected nuclear material really exists in the core. The basic module of the CIVR is the presently available Criticality Tester (CT). In 1997, the IAEA implemented it for routine inspection use following successful field testing. While the CT uses linear kinetics for automatic decision finding, the CIVR takes into account also reactivity feedback effects (non-linear kinetics). Changes in core geometry and core material composition on criticality, neutron flux distribution and neutron spectra have been investigated theoretically and experimentally. Calculations have been performed with the multigroup diffusion code RHEIN and the Monte Carlo code MCNP. Neutron spectra were taken with proton recoil methods. CIVR is one of the inspection methods under discussion for the FRM-II reactor in Munich. Fundamentals of CIVR, hard- and software concepts, calculations and experimental results will be presented.