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The division's objectives are to promote the advancement of knowledge and understanding of the fundamental physical phenomena characterizing nuclear reactors and other nuclear systems. The division encourages research and disseminates information through meetings and publications. Areas of technical interest include nuclear data, particle interactions and transport, reactor and nuclear systems analysis, methods, design, validation and operating experience and standards. The Wigner Award heads the awards program.
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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.
T. J. van Rooyen, G. P. de Beer
Nuclear Science and Engineering | Volume 114 | Number 2 | June 1993 | Pages 87-101
Technical Paper | doi.org/10.13182/NSE93-A24020
Articles are hosted by Taylor and Francis Online.
Prompt fission neutrons (PFNs) constitute the most important component of the source term for nuclear reactor shielding calculations. The determination of the PFN source term for reactor shielding calculations has traditionally been performed using a number of simplifying assumptions. Very simple closed analytical expressions are normally used for the PFN spectrum. The Watt PFN spectrum for 235U, with coefficients determined by Cranberg et al., has become a virtual industry standard in the reactor shielding community. The source term is usually treated as a separable function of spatial location and energy, only the 235U spectrum is considered, and the effect of burnup on the source term is neglected. In reality, the PFN spectra of 235U, 238U, and 239Pu differ markedly, and their fractional contributions to fission are a function of burnup, which, in turn, is a time-dependent function of the spatial position within the reactor core. Recent theoretical developments have led to the advent of sophisticated microscopic models for the calculation of PFN spectra and multiplicities of various fissioning systems. Spectra for 235U, 238U, and 239Pu, calculated with the Madland-Nix model with fragment spin correction, were used in this investigation. An improved reactor source term model that calculates spectrally and spatially burnup-compensated source terms for nuclear reactor shielding calculations is developed and applied to a typical light water reactor (LWR).,Neutron, gamma-ray, and total absorbed dose rate distributions were calculated through four diverse biological shields with a thickness of 250 cm. At end-of-life core conditions, the traditional source term model leads to an underestimate of the transmitted absorbed dose rates by slightly more than a factor of 2. This discrepancy lies within the error margins quoted for LWR shielding calculations. We conclude that despite their age and simplicity, the Watt formula and the simple source term model are of sufficient accuracy for continued service. The more rigorous source term model presented here may be useful for accurate benchmark calculations and for the design of highly efficient shields for high-burnup reactors.
