Beta ray flux measuring device

This patent describes a beta ray flux measuring device connectable to a reactor vessel containing a reactor coolant at a pressure, for detecting a beta ray flux emitted from respective portions of an activated member irradiated at corresponding sensing positions within the vessel. It comprises: a pressure boundary defining an inner space with a central axis and being connectable to the reactor vessel so that the inner space contains some of the reactor coolant at substantially the pressure; an outer insulator positioned around the central axis within the inner space; a collector ring having a response characteristic and being positioned within the inner space and around the central axis; and an inner conductor positioned around the central axis and within the collector ring so as to be electrically isolated from the collector ring