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Latest News
What’s the most difficult question you’ve been asked as a maintenance instructor?
Blye Widmar
"Where are the prints?!"
This was the final question in an onslaught of verbal feedback, comments, and critiques I received from my students back in 2019. I had two years of instructor experience and was teaching a class that had been meticulously rehearsed in preparation for an accreditation visit. I knew the training material well and transferred that knowledge effectively enough for all the students to pass the class. As we wrapped up, I asked the students how they felt about my first big system-level class, and they did not hold back.
“Why was the exam from memory when we don’t work from memory in the plant?” “Why didn’t we refer to the vendor documents?” “Why didn’t we practice more on the mock-up?” And so on.
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.
