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Latest News
Deep Space: The new frontier of radiation controls
In commercial nuclear power, there has always been a deliberate tension between the regulator and the utility owner. The regulator fundamentally exists to protect the worker, and the utility, to make a profit. It is a win-win balance.
From the U.S. nuclear industry has emerged a brilliantly successful occupational nuclear safety record—largely the result of an ALARA (as low as reasonably achievable) process that has driven exposure rates down to what only a decade ago would have been considered unthinkable. In the U.S. nuclear industry, the system has accomplished an excellent, nearly seamless process that succeeds to the benefit of both employee and utility owner.
Mahmoud Z. Youssef, Neil Morley, Anter El-Azab
Fusion Science and Technology | Volume 34 | Number 3 | November 1998 | Pages 697-705
Neutronics Experiments and Analysis | doi.org/10.13182/FST98-A11963696
Articles are hosted by Taylor and Francis Online.
Innovative concepts are being explored and evaluated in the Advanced Power Extraction (APEX) study to enhance the capability of removing high power density and surface wall load while satisfying all other blanket functional requirements. The minimum surface and neutron wall load considered is ∼1.5 MW/m2 and 7 MW/m2, respectively, with account taken for peaking factors. Liquid first wall is among the concepts considered in which a flowing layer is introduced from the top of the Tokamak. Liquid lithium, Flibe, and Li17Pb83 are among the candidate materials considered. The objectives of the present work are: (a) determination of the spatial range over which X-ray from the plasma deposits its energy across the protective liquid layer under a realistic spectrum, (b) evaluation of the impact of difference in the neutron moderation among the liquid studied on the volumetric heat deposition rate across the layer as well the structured blanket behind it, and (c) assessment of the percentage of tritium bred only in the liquid layer relative to the total tritium bred in the entire system. In this paper, it is shown that X-ray deposits its energy over a finite depth in the layer; contrary to what have been assumed in previous studies. This assessment gives the correct input source for the thermal hydraulic analysis and leads to a large decrease in the liquid surface temperature. It is shown that: (a) still high heat deposition rate is attainable at the layer surface due to the fraction of the Bremsstrahlung spectrum below ∼80 eV (Li) and ∼200 eV (Flibe) which constitutes only ∼0.4% of the incident spectrum, (b) Flibe is more powerful in moderating neutrons than Li, leading to a factor of 2–9 reduction in the volumetric heating rate (and thermal stresses) across the structured blanket, and (c) the fraction of the total breeding ratio, TBR, attributed only to the convective layer is ∼25% although the liquid layer is only ∼9% of the layer/blanket length.
