From operational safety perspectives, several quantities are to be known ( Broadhead et al., 1995 Gauld and Ryman, 2001 Hu et al., 2016 Govers et al., 2019): the neutron and γ-ray emission rates and spectra are of interest for radiation protection, the decay heat rate is required for SNF thermal performance and ageing assessment and the inventory of fissile nuclides is one of the main drivers for criticality safety considerations and nuclear safeguards. The study includes a code-to-code and code-to-experiment comparison using different nuclear data libraries.Ĭharacterisation of spent nuclear fuel (SNF) is essential for the back-end of the fuel cycle to support a safe, secure, ecologic and economic handling, transport, storage and disposal of SNF. Results of these measurements were used to study the performance of depletion codes, i.e., ALEPH2, SCALE, and Serpent2. Measurements of a segment of a spent nuclear fuel rod were carried out at SCK CEN resulting in an absolute and non-destructive measurement of the neutron production rate avoiding any reference to a representative spent nuclear fuel sample to calibrate the device. Experiments with 252Cf(sf) sources, certified for their neutron emission rate, were carried out at the Joint Research Centre to determine the characteristics of the detection device. The method relies on a transfer procedure that is adapted to the hot cell facilities at the Laboratory for High and Medium level Activity of SCK CEN in Belgium. A neutron well counter designed for routine nuclear safeguards applications is applied. 4European Commission, Joint Research Centre (JRC), Ispra, ItalyĪ method to determine the neutron production rate of a spent nuclear fuel segment sample by means of non-destructive assay conducted under standard controlled-area conditions is described and demonstrated.3Jožef Stefan Institute (JSI), Ljubljana, Slovenia.2Belgian Nuclear Research Centre (SCK CEN), Mol, Belgium.1European Commission, Joint Research Centre (JRC), Geel, Belgium.This paper analyzes time correlated induced fission (TCIF) from fresh MTR fuel assemblies due to 252Cf and AmLi active interrogation sources.Peter Schillebeeckx 1*, M. In this work, two MTR fuel assemblies varying both in size and number of fuel plates were measured using 252Cf and AmLi active interrogation sources. The induced fission (IF) neutrons are also time correlated resulting in more correlated neutron detections inside the 3He detector, which helps reduce the statistical errors in doubles when using the 252Cf interrogation source instead of the AmLi source. The 252Cf source spontaneously emits bursts of time-correlated prompt fission neutrons that thermalize in the water and induce fission in the fuel assembly. In this study, experiments were performed to calibrate the AEFC instrument and compare use of the 252Cf spontaneous fission source and the AmLi (α,n) neutron emission source. Owing to the difficulty in obtaining an AmLi source, a 252Cf spontaneous fission (SF) source was used during a 2014 field trail in Uzbekistan as an alternative. In the past, most of the active interrogation systems along with the AEFC used an AmLi neutron interrogation source. Active coincidence measurement data is used to measure residual fissile mass, whereas the passive coincidence measurement data along with passive gamma measurement can provide information about burnup, cooling time, and initial enrichment. The 3He detectors are used for active and passive neutron coincidence counting while the ion chamber is used for gross gamma counting. The AEFC is comprised of six 3He detectors as well as a shielded and more » collimated ion chamber. Since spent fuel assemblies are stored in water, the system was designed to be watertight to facilitate underwater measurements by inspectors. The Advanced Experimental Fuel Counter (AEFC) is a nondestructive assay (NDA) system developed at Los Alamos National Laboratory (LANL) combining both neutron and gamma measurement capabilities. To accomplish this goal various nondestructive and destructive assay techniques have been developed in the US and around the world. The effective application of international safeguards to research reactors requires verification of spent fuel as well as fresh fuel. As such, it gives insight into the room-return characteristics of this new experimental area and the adequacy of the UT-calculated response matrix for Bonner spheres.
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