Reactor instrumentations

Purpose: To surely maintain the performance and improve the reliability of measuring devices in a reactors even under the neutron irradiation over long period of time. Constitution: The inside of an ionizing chamber case made of austenite stainless steels is filled with an inert gas and sealed with insulation seals. The insulators and the insulating seals are constituted with ceramics as in the anode support plates. Since volume expansion phenomenon due to neutron irradiation is generally found in the reactor and the performance may be lost in a long time use. In view of the above, the anode support members, insulators and insulation seals are made of spinnel type ceramics, for example, MgAl2O4. The volume expansion coefficient of MgAl2O4 is substantially zero irrespective of the increase in the neutron irradiation dose and temperature rise. There is no structural change even long time use in the nuclear reactor and the insulation property can be maintained to provide a reliable performance. (Horiuchi, T.)