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ANS Student Conference 2025
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Latest News
Norway’s Halden reactor takes first step toward decommissioning
The government of Norway has granted the transfer of the Halden research reactor from the Institute for Energy Technology (IFE) to the state agency Norwegian Nuclear Decommissioning (NND). The 25-MWt Halden boiling water reactor operated from 1958 to 2018 and was used in the research of nuclear fuel, reactor internals, plant procedures and monitoring, and human factors.
Mekiel Olguin, Christopher Perfetti, Forrest Brown
Nuclear Science and Engineering | Volume 196 | Number 11 | November 2022 | Pages 1323-1332
Technical Paper | doi.org/10.1080/00295639.2022.2087831
Articles are hosted by Taylor and Francis Online.
The dominance ratio is the ratio of the first higher-order mode eigenvalue of a system to the fundamental eigenvalue, k1/k0. It can be used to determine how well coupled the neutrons in a multiplying system are, as well as the computational difficulty of the power iteration method in a Monte Carlo simulation. The purpose of this study is to investigate the University of New Mexico’s (UNM’s) AGN-201M reactor’s unusually low dominance ratio of 0.632. The AGN-201M reactor is a small, thermal spectrum reactor located at the UNM. It is moderated by polyethylene, reflected by graphite, and uses fuel comprised of uranium microspheres embedded in polyethylene plates that are separated by an aluminum baffle. The investigation included a parametric study of the reactor’s fuel geometry, fuel density, and reflector thickness to examine their impact on the reactor’s dominance ratio. In addition, neutronically similar systems were examined to identify common causes for systems with low dominance ratios. The reason for the small dominance ratio of the AGN-201M reactor when compared to large thermal reactors was determined to be because of its size and fuel plate composition. The reflector’s effect on the dominance ratio is small in comparison to the other factors but was found to have a nonzero effect. Furthermore, the AGN-201M was found to have a significantly lower dominance ratio than systems with which it shares a very high ( > 95%) degree of neutronic similarity. However, the two most similar systems were close in size to the core of the AGN-201M reactor and were moderated with polyethylene as well.
