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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.
Jim E. Morel, James S. Warsa
Nuclear Science and Engineering | Volume 156 | Number 3 | July 2007 | Pages 325-342
Technical Paper | doi.org/10.13182/NSE06-13
Articles are hosted by Taylor and Francis Online.
We consider two general finite-element lumping techniques for the Sn equations with discontinuous finite-element spatial discretization and apply them to quadrilateral meshes in x-y geometry. One technique is designed to ensure a conservative approximation and is referred to as conservation preserving (CP). The other technique is designed to preserve the exact solution whenever it is contained within the trial space and is referred to as solution preserving (SP). These techniques are applied in x-y geometry on structured nonorthogonal grids using the bilinear-discontinuous finite-element approximation. The schemes are both theoretically analyzed and computationally tested. Analysis shows that the two lumping schemes are equivalent on parallelogram meshes. Computational results indicate that both techniques perform extremely well on smooth quadrilateral meshes. On nonsmooth meshes, the preserving technique retains its excellent performance while the CP technique degrades. The reasons for this degradation are discussed. Although the SP scheme has proven to be generally effective on quadrilateral meshes in x-y geometry, it is not expected to be effective for quadrilaterals in r-z geometry or for hexahedra in three-dimensional Cartesian geometry. Thus, a full lumping procedure for general nonorthogonal meshes that possesses all of the desired properties has yet to be found. For reasons that are discussed, it appears unlikely that such a procedure exists.