Abstract
Efforts are underway at Oak Ridge National Laboratory to improve the nuclide inventory validation basis for spent nuclear fuel at high burnups. Recently conducted radiochemical assay experiments provided new measurement data for nine samples of fuel irradiated in a pressurized water reactor, with estimated sample burnups in the 30 to 70 GWd/t range. This type of destructive assay data is essential for validating computational methods, tools, and nuclear data applied in nuclear safety analyses and for improving our understanding of the bias and uncertainty in code predictions. The measurement data include key actinides and fission products that span a gamut of needs and interests for nuclear science and engineering applications in criticality safety, reactor physics, nuclide inventory, decay heat, and radiation shielding. The SCALE 6.3 code system with ENDF/B-VII.1 cross-section libraries was used to simulate the irradiation histories of the measured fuel samples. The calculated nuclide concentrations are compared to corresponding measurement data. The significance of the comparisons is discussed, emphasizing how the addition of the new measurement data fills gaps in the validation basis at high burnups and contributes to the decrease in bias and uncertainty for predicted nuclide concentrations. The discussion addresses the effect of the sample burnup used in the simulation—which is based on reactor operator records or on calibration to measured data for burnup indicator fission products—on the validation results.
| Original language | English |
|---|---|
| Journal | Nuclear Science and Engineering |
| DOIs | |
| State | Accepted/In press - 2025 |
Funding
This manuscript has been authored by UT-Battelle, LLC under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). Validation data gaps are particularly evident for higher burnups and higher enrichments for UO-fueled LWRs, as illustrated in for pressurized water reactor (PWR) spent fuel. The color mapping in this figure indicates the origin of the measured fuel by reactor name for a total of 13 reactors. To address the need to fill existing validation data gaps for PWR fuel with characteristics typical of current commercial LWRs and for high burnups, RCA experiments are underway at Oak Ridge National Laboratory (ORNL). These experiments, made possible through joint funding from the U.S. Nuclear Regulatory Commission and the U.S. Department of Energy (DOE), will provide high-quality RCA data for 16 samples selected from fuel irradiated in the North Anna PWR. These 16 fuel samples were selected from 6 of the 25 fuel rods collectively known as sister rods. The sister rods, with rod-average burnups between 48 and 59 GWd/t, have been the subject of extensive nondestructive post-irradiation examinations performed by ORNL and Pacific Northwest National Laboratory under the multi-institutional High Burnup Spent Fuel Data Project funded by the DOE Office of Nuclear Energy, to study transportation and long-term storage for high-burnup LWR fuel. On-site availability of these fuel rods at ORNL presented an opportunity to conduct RCA experiments to fill in existing nuclide inventory validation gaps for high-burnup fuel data relevant to storage, transportation, recycling, and disposal of spent nuclear fuel. 2
Keywords
- Nuclide inventory
- SCALE 6.3
- high burnup
- spent nuclear fuel
- validation