• Journal of Energy Engineering
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• v.21 no.3
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• pp.221-227
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• 2012

The CANDU 9 shield cooling system was designed and layout with the objective of promoting natural circulation on loss of forced flow. In the present study, the shield cooling natural circulation was analyzed using verified the thermal-hydraulic code when the coolant pump or the heat exchanger was lost. This study showed that thermosyphoning cooled the end shields and prevented the end shields and the reserve water tank from boiling for at least 8 hours on loss of the shield cooling pumps but the heat exchangers still operational. With the loss of both pumps and heat exchangers, the end shields remain subcooled for up to 4 hours. To enhance thermosyphoning, the bypass connection to the line from the reserve water tank should be relocated to a point as low as possible.

• Journal of Korean Vacuum Science & Technology
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• v.7 no.2
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• pp.27-32
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• 2003

A large cryo-pumping system composed of 4 cryosorption pumps was designed and manufactured to satisfy the pressure requirements of the NBI test stand. The cryosorption pump consists of a thermal shield/baffle assembly and a cryopanel coated with activated carbon granules. The thermal shield is cooled by liquid nitrogen, and the cryopanel by a commercial helium refrigerator. The operation characteristics and vacuum performance of the cryosorption pump were investigated. The cooling down time of the cryopanel to 20 K was about 6 hours with a liquid nitrogen consumption rate of about 35 L/hr. The maximum pumping speed of the cryosorption pump for the hydrogen gas measured by the steady pressure method was about 90,000 L/s.

• Progress in Superconductivity and Cryogenics
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• v.15 no.4
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• pp.53-58
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• 2013

KSTAR in-vessel cryo-pump has been installed in the vacuum vessel top and bottom side with up-down symmetry for the better plasma density control in the D-shape H-mode. The cryogenic helium lines of the in-vessel cryo-pump are located at the vertical positions from the vacuum vessel torus center 2,000 mm. The inductive electrical potential has been optimized to reduce risk of electrical breakdown during plasma disruption. In-vessel cryo-pump consists of three parts of coaxial circular shape components; cryo-panel, thermal shield and particle shield. The cryo-panel is cooled down to below 4.5 K. The cryo-panel and thermal shields were made by Inconel 625 tube for higher mechanical strength. The thermal shields and their cooling tubes were annealed in air environment to improve the thermal radiation emissivity on the surface. Surface of cryo-panel was electro-polished to minimize the thermal radiation heat load. The in-vessel cryo-pump was pre-assembled on a test bed in 180 degree segment base. The leak test was carried out after the thermal shock between room temperature to $LN_2$ one before installing them into vacuum vessel. Two segments were welded together in the vacuum vessel and final leak test was performed after the thermal shock. Commissioning of the in-vessel cryo-pump was carried out using a temporary liquid helium supply system.

• Progress in Superconductivity and Cryogenics
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• v.24 no.4
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• pp.59-64
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• 2022

The cryogenic system of RAON which is Korea's first heavy ion accelerator was numerically modeled and simulated. EcosimPro which is widely used off-the-shelf numerical software for a large scale cryogenic system was used for the simulation. The model of SRF TF cryogenic system, which is the testbed of cryomodule, was firstly established. The integrity of system of SRF TF was confirmed by comparison of simulation and experimental results. The cool-down strategy to minimize the thermal stress of the cavity was simulated and an optimal strategy was established. In addition, the influence of valve and pump control parameters on the cooling time was investigated, and optimal control parameters were also derived. The cryogenic system of SCL3 that is a low-energy acceleration section including 55 cryomodules, valve boxes, and helium supply lines was also modeled. The soundness of the thermal shield system and interlock system of SCL3 was investigated.