Boiling commencement detecting means for reactor

Object: To detect the point at which boiling begins by measuring void distribution from neutron flux with a simple means by making use of the idle time of a device for measuring neutron flux in the direction of the reactor axis. Structure: A detector for detecting neutrons within a transportable reactor is inserted from the lower portion of the core, and as it is lowered from the upper portion the neutron flux as the output of a neutron flux calculator is recorded in an X-Y recorder. The output of the neutron flux calculator is coupled to a band-pass filter, which extracts components due to the void influence. Then, the void distribution in the axial direction is derived by using a squarer and an integrator. At this time, the void distribution can be recorded in the X-Y recorder by connecting a selection switch to the side of void extent measurement. The point at which boiling commences is one at which the value of the void distribution recorded in the X-Y recorder suddenly increases. (Kamimura, M.)