Dynamic behavior of the cryogenic hydrogen system using only a heater control

Abstract

The J-PARC cryogenic hydrogen system provides supercritical hydrogen to three moderators and absorbs a nuclear heating of 3.75 kW for a 1-MW proton beam operation. A pressure control system, which consists of a heater for the thermal compensation and a cryogenic accumulator with a bellows acting as a volume controller, is prepared to mitigate a pressure fluctuation caused by the sudden heat load of kW-order. Stable operation with a 120-kW proton beam power, where the heat load is 450 W, has been conducted since November 2009. However, a major problem with cryogenic accumulator occurred during a short maintenance period in February 2010. In order to resume the 120-kW proton beam operation as soon as possible, an operational approach without using the cryogenic accumulator was studied and the hydrogen loop was partially altered. It was confirmed through an on-beam commissioning that only the approach could successfully mitigate the pressure fluctuation below the allowable value of 0.1 MPa, although it was eight times higher than that for the use of the pressure control system. The 120-kW proton beam operation was successfully resumed two months later.