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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.
Hans K. Fauske
Nuclear Science and Engineering | Volume 51 | Number 2 | June 1973 | Pages 95-101
Technical Paper | doi.org/10.13182/NSE73-A26584
Articles are hosted by Taylor and Francis Online.
A mechanism believed responsible for the explosive vapor growth observed in Armstrong’s experiment with LMFBR materials (liquid sodium injected into molten UO2) is discussed. Basically, liquid sodium globules can be entrained and wet the liquid UO2 surfaces. The lack of nucleation sites in the liquid-liquid-like system results in the overheating of the liquid sodium until homogeneous nucleation occurs. When the superheat limit is reached, vaporization is rapid enough to produce shock waves.The validity of the proposed entrainment-wetting-superheat mechanism to explain the observed UO2-Na explosions has been demonstrated by above surface injection of liquid Freon-11 (normal boiling point 23.8°C) into hot water (70 to 90°C). This liquid-liquid system is believed to simulate Armstrong’s UO2-Na system, since in the latter, the transition from film boiling to nucleate boiling based upon Henry’s film boiling correlation will take place at a temperature well above the melting temperature of UO2.Based upon this mechanism, large-scale coherent UO2-Na vapor explosions would appear impossible in a reactor environment. In a real reactor system, fission gases and fragments, as well as solid materials and gas bubbles entrained in the liquid sodium, would be present and would promote boiling prior to reaching the threshold for homogeneous nucleation in sodium, therefore resulting in mild interactions of the type observed in the TREAT in-pile experiments.