Spent Fuel Measurements with the Fork Detector at the Nuclear Power Plant of Doel

SCK•CEN is involved in the investigations and implementation of experimental methods for the burnup determination of spent fuel elements. One of these methods is the so-called Fork Detector, consisting of two cadmium wrapped polyethylene arms containing one fission chamber and one ionization chamber each. In the case of a spent fuel element, the measured neutron count rate is mostly due to the neutron emission from the spontaneous fission of 244Cm, taking into account a sufficient cooling time; this is related to the burnup by a power function whose parameters can be determined experimentally by measuring SFEs with well-known initial enrichments and irradiation histories. This detector has been successfully used for the burnup determination in the nuclear power plant of Tihange (B). This detection system was refurbished and upgraded to fit the requirements of the nuclear power plants of Doel (B). This paper reports about the measurement and qualification campaigns that were carried out at the NPP of Doel and the results obtained, and highlights its use for satisfying the safety requirements of the Authorities, related to reprocessing and transport of spent fuel.