Abstract: A method of detecting liquid leakage from a wall portion of apparatus and/or tubes containing a liquid. A cover member is attached to an outer surface of the wall portion to form a space defined between the cover member and the wall portion, and an optical fiber is inserted into the space through a hole in the cover member. A light beam is supplied through a palarized beam splitter to the optical fiber such that reflected light from the end of the optical fiber is measured, and the presence of leakage is determined in accordance with the amount of reflected light.

Abstract: A condenser microphone utilizable at high temperature and intense radioactive rays. The microphone has a tension ring and a backplate, both of which are made of a metal having a small coefficient of linear expansion relative to the other parts of the microphone. The tension ring is fitted to a tension ring holder, and the backplate is mounted on the tension ring holder through an insulating material so that the tension ring and the backplate are held together to form a unitary structure.

Abstract: A system and a method of confirming the operation of a steam relieving safety valve for a water-cooled nuclear reactor are provided. Acoustic vibration generated by steam relieved from the safety valve when the latter is opened is detected by an acoustic emission sensor. The acoustic emission sensor is mounted on the safety valve or a steam relief pipe connected to the safety valve.