Thermal Analysis Of Vacuum Vessel Thermal Shield Efficiency With Pumping Holes


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ITER Team (Garching, Germany) - International Thermonuclear Experimental Reactor


The presented analysis is aimed to evaluate VVTS efficiency with pumping holes, i.e. define heat influx to the TFC structure at several several options of the pump holes location: a) from the Port side (in the thck fin 10mm) and b) in the thin fin (5mm) facing to the TFC side. To accomplish this task 3D thermal analyses of typical regular segments of the UPTS with the expected maximum temperature gradients over fins have been carried out.

Results:

- As calculation results showed, fabrication of the penetration holes in the thin (5 mm) fin facing to the TFC leads to significant (into 3.4 times) increasing of heat losses to the TFC structure under the VV LOCA condition (pessimistic case).

- Penetration of the thick fin leads to negligible (1 ё 2 %) increasing of heat losses to the TFC structure inside the range of the relative step between pumping holes from 0.04 (ratio of the hole diameter - 30 mm to the distance between them - 790 mm) to 0.11 (hole diameter - 10 mm, distance between them - 88 mm). Heat flux distribution for the middle option with the relative step of 0.06 (hole diameter - 30 mm, distance between them - 500 mm), as an example, is shown in Fig. 7-3. Heat distribution for the other options is the similar.

- Based on the obtained results, it can be stated that the penetration holes are to be made from the VV side. The relative step between pumping holes should be chosen only from the technology requirements and pumping condition point of view.

- The recommended distance between pumping holes and the flanges are to be less or equal to 50 mm.



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