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WIPP: Lessons in transportation safety
As part of a future consent-based approach by the federal government to site new deep geologic repositories for nuclear waste, local communities and states that are considering hosting such facilities are sure to have many questions. Currently, the Waste Isolation Pilot Plant in New Mexico is the only example of such a repository in operation, and it offers the opportunity for state and local officials to visit and judge for themselves the risks and benefits of hosting a similar facility. But its history can also provide lessons for these officials, particularly the political process leading up to the opening of WIPP, the safety of WIPP operations and transportation of waste from generator facilities to the site, and the economic impacts the project has had on the local area of Carlsbad, as well as the rest of the state of New Mexico.
Abhishek Chakraborty, Suneet Singh, M. P. S. Fernando
Nuclear Science and Engineering | Volume 196 | Number 6 | June 2022 | Pages 715-734
Technical Paper | doi.org/10.1080/00295639.2021.2011670
Articles are hosted by Taylor and Francis Online.
Large nuclear reactors operating in the thermal spectrum are prone to both global and regional oscillations in power due to variation of 135Xe concentration. These power oscillations are self-stabilizing up to a certain operating power level, beyond which spatial power control becomes necessary for suppressing these oscillations. Especially for large pressurized heavy water reactors (PHWRs), which are natural uranium–fueled reactors using heavy water as coolant and moderator, the modes of xenon instabilities decide the extent and scheme for spatial power control. In this paper, the effect of spatial control on the bifurcation characteristics is demonstrated using a two-region model. The error signal for movement of the reactivity device has a global component for bulk power control and a local component for regional power control. The amount of regional power control determines the power level at which the spatial xenon oscillations stabilize. Using bifurcation analysis, it is found that in case of limited regional control, both supercritical and subcritical Hopf bifurcations exist, whereas in the case of increased regional control only supercritical Hopf bifurcations exist. However, these supercritical Hopf oscillations are due to time lag in control and have short timescales and lower amplitudes as compared to xenon oscillations. Hence, a proper choice of spatial control enables a PHWR to operate at rated full power capacity without any spatial Xenon instability.
