Temperature control for spallation target in accelerator driven system

In an accelerator driven critical or sub-critical system (ADS), a spallation target is irradiated by high-power proton beam to drive a reactor. To continuously produce very intense neutrons, it is very important to ensure that the target operates in a setting temperature environment. This paper reports several techniques of temperature control for the spallation target in China initiative ADS system, where tungsten granules in the target container are used as both coolant and target materials. In order to avoid high temperatures at the target center due to the Gaussian distribution of beam intensity, the proton beam should be scanned on the surface of the target to provide a high degree of uniformity in energy deposition. The target temperature can be controlled by adjusting automatically the speed of the coolant. If the speed attains the maximum setting value, the beam intensity will be decreased for a given value to reduce the heat generation. To evaluate the proposed control techniques, the heat transfer model of particles has been employed to investigate the spatio-temporal variations of the target temperatures. The simulation results indicate that the beam scanning technique reduces dramatically the temperatures. The target temperatures can be controlled by adjusting automatically both the granular speed and the beam intensity. The target can operate normally in the setting working temperature range even if the target is irradiated by the proton beam with the maximum power.