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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.
Joonhong Ahn, Shinichi Nakayama
Nuclear Technology | Volume 97 | Number 3 | March 1992 | Pages 323-335
Technical Paper | Radioactive Waste Management | doi.org/10.13182/NT92-A34640
Articles are hosted by Taylor and Francis Online.
Numerical results are presented for an analysis of diffusion of237Np, a redox-sensitive radionuclide, in engineered barriers consisting of overpack and bentonite-filled buffer regions, with oxidation-reduction kinetics of neptunium with iron and dissolved oxygen. Steady-state distributions of Fe(II) and dissolved oxygen are first obtained by considering the oxidation reaction of Fe(II) with oxygen. Based on these profiles, the neptunium diffusion models for pH 6.5 and 9.0 are established. Analytical or finite element solutions are obtained for the corresponding mathematical problems. At pH 9.0, even if dissolved oxygen intrudes on the buffer region from the rock/buffer interface, the penetration of oxygen into the overpack region and to the surface of the waste solid can be avoided. Thus, less soluble, strongly sorbing Np(IV) is released from the waste solid. At pH 6.5, dissolved oxygen can reach the waste surface. Weakly sorbing, soluble Np(V) is released from the waste solid. Although the released Np(V) is reduced to Np(IV) by Fe(II) in the overpack region, the Np(IV) is quickly oxidized by Fe(III) and dissolved oxygen at the overpack-buffer interface. Neglecting the existence of dissolved oxygen and assuming that the repository is kept under a reducing environment so that only Np(IV) migrates might lead to quite an optimistic estimate of the neptunium release rate from the engineered barriers.
