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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.
Salman Alzahrani (Missouri S&T/KACST), Shoaib Usman (Missouri S&T)
Proceedings | Advances in Thermal Hydraulics 2018 | Orlando, FL, November 11-15, 2018 | Pages 1189-1201
Twisted-tape is one of the most important members of passive heat transfer augmentation techniques for forced convection in many applications. In this paper, a numerical investigation of the heat transfer, pressure drop and secondary flow under the normal operating conditions of the NuScale SMR reactor for sub-channel with and without twisted tape geometry are performed. 3D models for twisted tapes on 2 x 2 rod bundle inside spacer grid fitted was developed. Subsequently, a twisted tapes on 2 x 2 along the entire sub-channel, that spacer grid and the gap between spaces were evaluated through the comparison with no twist tapes and with several twist ratios (p/d = 4.2, 1.7 and 0.85). The results have revealed a strong effect of twist ratios on pressure drop and secondary flow (SF) increases with decreasing twist ratio. Moreover, the Nusselt number (Nu) is increased with Reynolds number (Re) and there is a significant improvement in the Nusselt number when a twisted tape is inserted into the entire sub-channel under the same Reynolds number. For p/d=0.85, heat transfer (Nu) enhancement of 25% and 101% was observed for twisted tapes inside spacer grid and the entire sub-channel respectively. Results showed that the pressure drop with twisted tapes inside spacer grid and the entire sub-channel are influenced by variation of twisted ratio. The highest pressure drop is achieved for the twist ratio of p/d =0.85 which is the lowest twist ratio in this study. Pressure drop showed an almost linear dependence on the twist ratios. Likewise, the secondary flow is observed to be much more pronounced when the entire channel length contained the twisted tape. Interestingly, SF seems to be peaking at the exit point of the spacer grid where the twisted tape ends. SF seems along the entire sub-channel when the entire length contained the tape. The highest SF is achieved for the twisted ratio (p/d =0.85) which is the lowest twist ratio in this study by about SF=.0.16.