A cycle configuration for large-scale helium refrigerator for fusion devices towards complete mitigation of the effects of pulsed heat load

• Large-scale helium refrigerators are subjected to pulsed heat load from fusion devices.
• As a result plants may trip hindering continuous cooling of superconducting magnets.
• Proposed a cycle configuration for complete mitigation of such effects in plants.
• It includes cold-compressor, supercritical buffer and parallel heat exchanger.
• Dynamic simulation revealed almost complete mitigation can be obtained.

Large-scale helium refrigerators in fusion devices work in pulsed heat load condition. The immediate effect of pulsed heat load is mass flow rate fluctuation at the low pressure return stream to the cold-box of the refrigerator. As a result, thermodynamic properties of all the intermediate state points of the cold-box vary widely and may go beyond operating limits. Therefore, for continuous operation, the refrigerators need modification in cycle configuration in order to mitigate the effects of pulsed heat load generated out of the operation of the fusion devices. A number of mitigation techniques exist and none of them is capable of mitigating the mass flow rate fluctuation completely. However, combinations of two or more methods have been found to be effective in mitigation of the effects of pulsed load to the maximum possible extent. In this paper, a cold-end configuration has been proposed that is constituted of combination of different mitigation schemes proposed in previous works. Dynamic simulations are performed to predict the performance of the modified cycle configuration and for validation of the concept towards achievement of complete mitigation. Results of the work have revealed that through the proposed cold-end configuration, almost complete mitigation can be obtained.