MOX Fuel Characterization for Burnup Credit Application: Extension of Nondestructive Method Qualified for LEU Fuels

• Published in: Nuclear technology Vol. 154; no. 2; pp. 186 - 193
• Main Authors: Riffard, C., Toubon, H., Pelletier, S., Batifol, M., Vidal, J. M.
• Format: Journal Article
• Language: English
• Published: La Grange Park, IL Taylor & Francis 01.05.2006; American Nuclear Society
• Subjects: Applied sciences; Energy; Exact sciences and technology; Fuels; Nuclear fuels; Preparation and processing of nuclear fuels; Uncertainty; Safety analysis; nuclear measurements; Computation code; Burnup; Reprocessing; Nuclear reactor; Non destructive method; Accuracy; Depletion; nuclear spent fuels; Mixed fuel; burnup credit; Plutonium oxides; Uranium oxide; Criticality; Pressurized water reactor
• ISSN: 0029-5450; 1943-7471
• DOI: 10.13182/NT06-A3727

Before the reprocessing of low-enriched uranium (LEU) fuels at La Hague plant, the assemblies are characterized with a nondestructive assay based on neutron emission (NE) and gamma-ray emission combined with the CESAR depletion code, giving the burnup (BU) with a good accuracy (±5% within a batch of fuels from one of COGEMA-La Hague's clients). The measurements confirm the hypothesis of the safety-criticality analysis of the process, in the context of the BU credit allowance. There is a need to extend the allowance of the reprocessing plants to the case of more highly enriched LEU fuels and to the case of mixed-oxide (MOX) fuels. The aim is to propose an upgraded method, valid for both LEU and MOX fuels, giving the average BU with an uncertainty lower than ±15% for MOX fuels (without any modification of the current acceptance criteria for UO 2 fuel, i.e., ±15%), with a complementary module checking the operator data using the gamma-ray emission and the CESAR depletion code. In particular, the NE was interpreted with depletion calculations in the case of MOX fuels, which is the principal aim of this paper. This allows the BU determination of MOX fuels, which has been qualified during a measurement campaign in La Hague with 20 MOX assemblies. The mean BU of pressurized water reactor MOX assemblies has been determined for the first time with a maximum discrepancy of ±5% compared to the declared value.