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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.
Uncheol Shin, Warren F. Miller, Jr.
Nuclear Science and Engineering | Volume 128 | Number 1 | January 1998 | Pages 27-46
Technical Paper | doi.org/10.13182/NSE98-A1943
Articles are hosted by Taylor and Francis Online.
Using an asymptotic expansion, we found that the modified time-dependent simplified P2 (SP2) equations are robust, high-order, asymptotic approximations to the time-dependent transport equation in a physical regime in which the conventional time-dependent diffusion equation is the leading-order approximation. Using diffusion limit analysis, we also asymptotically compared three competitive time-dependent equations (the telegrapher's equation, the time-dependent SP2 equations, and the time-dependent simplified even-parity equation). As a result, we found that the time-dependent SP2 equations contain higher-order asymptotic approximations to the time-dependent transport equation than the other competitive equations. The numerical results confirm that, in the vast majority of cases, the time-dependent SP2 solutions are significantly more accurate than the time-dependent diffusion and the telegrapher's solutions. We have also shown that the time-dependent SP2 equations have excellent characteristics such as rotational invariance (which means no ray effect), good diffusion limit behavior, guaranteed positivity in diffusive regimes, and significant accuracy, even in deep-penetration problems. Through computer-running-time tests, we have shown that the time-dependent SP2 equations can be solved with significantly less computational effort than the conventionally used, time-dependent SN equations (for N > 2) and almost as fast as the time-dependent diffusion equation. From all these results, we conclude that the time-dependent SP2 equations should be considered as an important competitor for an improved approximate transport equation solver. Such computationally efficient time-dependent transport models are especially important for problems requiring enhanced computational efficiency, such as neutronics/fluid-dynamics coupled problems that arise in the analyses of hypothetical nuclear reactor accidents.
