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Nuclear Criticality Safety
NCSD provides communication among nuclear criticality safety professionals through the development of standards, the evolution of training methods and materials, the presentation of technical data and procedures, and the creation of specialty publications. In these ways, the division furthers the exchange of technical information on nuclear criticality safety with the ultimate goal of promoting the safe handling of fissionable materials outside reactors.
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ANS Student Conference 2025
April 3–5, 2025
Albuquerque, NM|The University of New Mexico
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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.
Kodai Fukuda, Delgersaikhan Tuya, Jun Nishiyama, Toru Obara
Nuclear Science and Engineering | Volume 194 | Number 3 | March 2020 | Pages 181-189
Technical Paper | doi.org/10.1080/00295639.2019.1665459
Articles are hosted by Taylor and Francis Online.
Removal of fuel debris is regarded as one of the most important operations in the decommissioning of the Fukushima Daiichi nuclear power station (1F-NPS) to decrease long-term risk. To begin the operation, the consequences of possible criticality accidents must be evaluated in advance. In this work, we evaluated radiation doses during possible criticality accidents at 1F-NPS in assumptive fuel debris systems. In particular, the relationship between the water level surrounding the fuel debris and the radiation dose was investigated. This is because the water level surrounding the fuel debris is thought to have an impact on radiation dose during accidents as it affects both the reactivity and shielding of radiation. A combination of space-dependent kinetic analysis and radiation transport analysis was carried out in order to consider the special characteristics of fuel debris systems in water. Instead of traditional point-kinetics analysis, we used the Multi-region Integral Kinetic (MIK) code, which is a unique method based on Monte Carlo neutron transport calculations. The radiation transport calculation code Particle and Heavy Ion Transport Code System (PHITS) was used as well. The analyses revealed that the dose caused by criticality accidents may be the largest in systems in which part of the fuel debris is exposed to the air.