抄録
The Japan Atomic Energy Research Institute (JAERI) and the High Energy Accelerator Research Organization (KEK) are promoting a plan to construct a neutron scattering facility at the Tokai Research Establishment, JAERI, under the High-Intensity Proton Accelerator Project (the JAERI/KEK Joint Project). In the facility, 1 MW pulsed proton beam from a high-intensity proton accelerator will be injected into a mercury target in order to produce high-intensity neutrons for use in the fields of life and material sciences. The spallation mercury target system is designed for aiming to start its construction from FY2003. A spallation neutron source is proposed using a high-energy (3.0GeV) proton beam with a current of 0.333mA (1MW) and operating at 25Hz with a pulse duration less than 1μs. A cross flow type (CFT) mercury target has been designed in order to distribute mercury flow according to an axial heat generation distribution caused by spallation reaction. The inner structure arrangement of the mercury target vessel was determined in order to realize appropriate mercury flow distribution according to axial heat generation distributin, based on the thermal hydraulic analytical results of 3GeV, 1MW proton beam injection by using the STAR-CD code. This paper presents the final design of the CFT target using blade distributors, CFD analytical results of the CFT target. The flow distribution in the CFT target is one of key feasibility issues in order to effectively produce the CFT target design. The general computational fluid dynamics (CFD) code STAR-CD was used to analyze the time-averaged thermal hydraulics and flow distribution in the CFT target. In the analysis, an inlet temperature of 50℃ and an inlet mercury velocity of 1.0m/s were assumed. As results, a maximum velocity of 2.48m/s was observed near the front end of the outlet plenum and a maximum of 125.5℃ was observed near the beam window where the volumetric heat generation rate was relatively large. The maximum temperature of 125.5℃ is far below the mercury saturation temperature of 356℃ under atmospheric pressure. This result satisfied the thermal-hydraulic design criteria of " Maximum mercury temperature in the target shall be less than 300℃". A maximum outer surface temperature was obtained at the beam window and was calculated to be 207℃. On the other hand, a maximum inner surface temperature was calculated to be 132℃. A double walled safety hull with water jackets of heavy water is going to cover the mercury target in order to ensure the safety and to collect mercury in a case of mercury leakage caused by the target beam window failure.
