Development of cold moderator vessel for the spallation neutron source flow field measurements and thermal hydraulic analyses in cold moderator vessel

摘要

The Japan Atomic Energy Research Institute is developing a several MW-scale spallation target system under the High-Intensity Accelerator Project. A cold moderator using supercritical hydrogen is one of the key components in the target system, which directly affects the neutronic performance both in intensity and resolution. Since a hydrogen temperature rise in the moderator vessel affects the neutronic performance, it is necessary to suppress the recirculation and stagnant flows which cause hot spots. In order to develop the conceptual design of the moderator structure in progress, the flow field was measured using a PIV (Particle Image Velocimetry) system under water flow conditions using a flat model that simulated a moderator vessel. From these results, the flow field such as recirculation flows, stagnant flows etc. was clarified. The hydraulic analytical results using the standard k-ε model agreed well with experimental results. Thermal-hydraulic analyses in the moderator vessel were carried out under liquid hydrogen conditions. Based on these results, we clarified the possibility of suppressing the local temperature rise within 3K under 2MW operating condition.