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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.
Jeffrey A. Favorite, Ashley D. Thomas, Thomas E. Booth
Nuclear Science and Engineering | Volume 168 | Number 2 | June 2011 | Pages 115-127
Technical Paper | doi.org/10.13182/NSE09-72
Articles are hosted by Taylor and Francis Online.
Particle fluxes on surfaces are difficult to calculate with Monte Carlo codes because the score requires a division by the surface-crossing angle cosine, and grazing angles lead to inaccuracies. We revisit the standard practice of dividing by half of a cosine “cutoff” for particles whose surface-crossing cosines are below the cutoff. We concentrate on the flux crossing an external boundary, deriving the standard approach in a manner that explicitly points out three assumptions: (a) that the external boundary surface flux is isotropic or mostly isotropic, (b) that the cosine cutoff is small, and (c) that the minimum possible surface-crossing cosine is 0. We find that the requirement for accuracy of the standard surface flux estimate is more restrictive for external boundaries (a very isotropic surface flux) than for internal surfaces (an isotropic or linearly anisotropic surface flux). Numerical demonstrations involve analytic and semianalytic solutions for monoenergetic point sources irradiating surfaces with no scattering. We conclude with a discussion of potentially more robust approaches.