Neutron absorbing performance monitor

The device of the present invention can monitor neutron absorption characteristics of a tested member such as a neutron absorption tube at high accuracy, easily and rapidly. That is, the tested member is kept by a holding mechanism and neutrons are emitted from a neutron source disposed at a predeterminable position in the tested member. The emitted neutrons are partially absorbed by the neutron absorption characteristics of the tested member and partially transmit the tested member. The intensity level of the transmitted neutrons is monitored by a neutron monitor opposed to the neutron source. The monitoring operation is previously conducted also for a standard test member, the neutron absorption rate of which is already known, and the neutron absorption characteristics of the tested member is determined by the intensity level ratio of the transmission neutrons. With such procedures, the neutron absorption characteristics of the tested member can be obtained in a non-destructive manner, rapidly and at a high accuracy. (I.S.)