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ANS Student Conference 2025
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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.
Yong Hoon Jeong, Mujid S. Kazimi
Nuclear Technology | Volume 159 | Number 2 | August 2007 | Pages 147-157
Technical Paper | Fuel Cycle and Management | doi.org/10.13182/NT07-A3861
Articles are hosted by Taylor and Francis Online.
The hybrid sulfur cycle (often called the Westinghouse cycle) for decomposing water into hydrogen and oxygen has two steps. The sulfuric acid is decomposed into steam and sulfur trioxide, which is further decomposed into sulfur dioxide and oxygen at high temperature (~1100 K). Hydrogen is produced by electrolysis of a sulfur dioxide and water mixture at low temperature, which also results in the formation of oxygen and sulfuric acid.In this study, separation of decomposed products and internal heat recuperation are examined, and ways to optimize the energy efficiency of the hybrid cycle are explored by varying the electrolyzer acid concentration, decomposer acid concentration, pressure and temperature of the decomposer, and the internal heat recuperation. The analysis is based on currently available experimental data for the electrode potential.A cycle efficiency of 45.3% [lower heating value (LHV)] appears to be achievable at 1100 K (10 bar, 1100 K, and 60 mol% of H2SO4 for the decomposer, 60 wt% of H2SO4 for the electrolyzer). For a maximum temperature of 1200 K, 50.5% (LHV) appears to be the achievable cycle efficiency (10 bar, 1200 K, and 60 mol% of H2SO4 for the decomposer, 60 wt% of H2SO4 for the electrolyzer). Operation under elevated pressures (70 bar or higher) results in loss of cycle efficiencies due to lower yield of the SO2 in the decomposer but minimizes equipment size and possibly capital cost. However, the loss in efficiency as pressure increases is not large at high temperature (1200 K) compared to that at low temperatures (1000 to 1100 K). Therefore, high-pressure operation for minimizing capital investment would be favored only if the high temperature can be accommodated. The major factors that can affect the cycle efficiency are reducing the electrode overpotential and having structural materials that can accommodate operation at high temperature and high acid concentration.