Hitachi, Ltd.

Masaaki Fujii

Hiroshi Kitaguchi

Takehiko Kitamori

Tsuguo Sawada

Masashi Kudo

This invention relates to an apparatus for measuring the radioactive concentration of a radioactive material-containing liquid. In order to improve the measuring sensitivity of and miniaturize the apparatus, it includes a vertically-disposed outer cylinder, an inner cylinder disposed in and concentrically with the outer cylinder, a radiation detector disposed in the inner cylinder, a radioactive liquid feed means for supplying a radioactive material-containing liquid in the form of an annular current into an annular space between the inner and outer cylinders, a first cleaning water feed means for supplying a cleaning liquid along the inner surface of the outer cylinder, and a second cleaning water feed means for supplying a cleaning liquid along the outer surface of the inner cylinder. The cleaning water prevents the radioactive material from being deposited on the inner surface of the outer cylinder and the outer surface of the inner cylinder, and the measuring sensitivity of the apparatus from decreasing.

Radioactive concentration measuring apparatus

A photoacoustic analyzer comprises an analyzing cell having a beam entrance window and including a cylindrical piezoelectric transducer element forming at least a part of the wall thereof, and a laser beam emitter emitting a laser beam directed toward and into the analyzing cell through the beam entrance window. In the photoacoustic analyzer, the ratio r/r.sub.o between the radius r of the inner side of the analyzing cell and the radius r.sub.o of the incident laser beam is selected to lie within the range of 1.ltoreq.r/r.sub.o .ltoreq.8.

Photoacoustic analyzer

An apparatus for measuring the concentration of radioactivity in a radioactive fluid discharged from a nuclear power plant. The apparatus comprises a radioactivity concentration measurement pipe arranged to extend vertically, fluid supplying means for supplying the fluid into the measurement pipe in such a manner that the fluid flows down through the measurement pipe along the axis of the measurement pipe without contacting the inner surface of the latter, radioactivity concentration measuring means disposed at the outside of the measurement pipe for measuring the radioactivity concentration in the fluid flowing in the measurement pipe, and means for discharging the radioactive fluid to the outside of the measurement pipe. The apparatus further comprises a gas supply pipe opening at its one end to the atmosphere and communicated at its other end with the inside of the measurement pipe, and a check valve disposed in the gas supply pipe and operated at a pressure higher than the atmospheric pressure. When the pressure in the measurement pipe has come down below the atmospheric pressure, the check valve is operative to always maintain the internal pressure in the measurement pipe at the atmospheric pressure, thereby to prevent the fluid level in the measurement pipe from being raised to reduce the background noise during the measurement of the radioactivity concentration.

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Katsuta, Japan

Masaaki Fujii