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Fusion Science and Technology
Latest News
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.
A. Nicolai, P. Börner
Fusion Science and Technology | Volume 12 | Number 1 | July 1987 | Pages 119-136
Technical Paper | Blanket Engineering | doi.org/10.13182/FST87-A25056
Articles are hosted by Taylor and Francis Online.
The main objective of this numerical study is to investigate how to minimize the tritium content in the first wall of a tokamak reactor. Mainly pulsed tokamak operation with 100-s cycle durations, 75-s duty times, and outgassing phases with durations τg between 500 and 3000 s is envisaged. These outgassing phases are started after every Np cycle (20 < Np < 70). For modeling, a multicode is applied that describes the surface and volume processes determining the tritium inventory in and the permeation through the first wall, the neutral gas background due to the recycling of the plasma, and the transport processes governing the parameters of a three-species burning plasma. The calculations show that control of the wall temperature Tw, determined by the heat transfer to the coolant and the radiation loading by the plasma, is decisive for the tritium buildup. Cooling is achieved by pressurized water or helium at a pressure pHe = 30 bar. The coolant channels are assumed to be composed of a corrugated steel sheet and the first wall, both connected in a panel-type construction. The main results are as follows: 1. In long outgassing phases (τg = 3000 s, Np = 70) at elevated temperatures (Tw = 300° C), the tritium content (˜20 g) after 1400 pulses is ˜2.5 times lower than in continuous irradiation with time-averaged intensity. 2. Shorter but more frequent outgassing phases, e.g., τg = 500 s, Np = 20, are less efficient. 3. Good outgassing efficiency at elevated temperatures is obtained at the expense of an enhanced tritium permeation to the outside. 4. An oxide layer, acting as an ideal diffusion barrier at the outside of the vessel, prevents permeation but effects a tritium content 30% higher than in case 1.
