Sensitivity studies on the production of Cm isotopes in spent fuel for safeguards applications

The verification of spent fuel elements is a major task for nuclear safeguards inspectors. The so-called Fork detector is often used in the verification of spent fuel elements. With this device one measures the total neutron emission that is originating mainly from the spontaneous fission decay due to 242,244Cm produced during irradiation. The neutron emission of a spent fuel element can be estimated from operator declared data by using depletion and evolution codes; the information obtained with these codes can be used together with experimental data to draw safeguards conclusions. To understand and compare the performances of measurements methods, it is important not only to have an estimation of the associated neutron emission but also of its uncertainty, which is often not given by depletion and evolution codes. The work presented here focuses on sensitivity studies to identify the nuclear data that mostly affect the production of Cm isotopes. In addition, this study assesses the impact of the uncertainty of nuclear data on the uncertainty of Cm abundances for a given irradiation case. The obtained results show that the contribution of the uncertainty in the decay data is smaller than the contribution of the uncertainty in the radiative capture cross section data. Uncertainties in the radiative capture cross section of 242mAm and 241Am are the largest contributors to the uncertainties in the abundance of 242Cm, while uncertainty in the radiative capture cross section of 243Am and 242Pu are the main contributors to uncertainty in 244Cm abundance.