HIGHLY SENSITIVE CONTINUOUS MONITOR OF RADIOACTIVITY IN WASTE LIQUID

摘要

PURPOSE:To make it possible to maintain the sensitivity of a detector at a lower limit of 10-7muCi/Ml for a long time by rinsing the inner wall of a cylindrical reservoir for the detector in case the radioactivity in the waste liquid from an atomic facilities is monitored with the use of a NaI detector. CONSTITUTION:A portion of the waste liquid flowing in a pipe 1 in the direction of arrow is guided by a bypass pipe 2 into a cylindrical sample reservoir 3 in a lead shielding member 6. By means of a NaI detector 5 covering most of the surface of the reservoir 3, the waste liquid in the reservoir 3 is monitored and then returned to the pipe 1 by the action of a pump 4. A rinsing mechanism 7 is periodically driven by an automatic control mechanism 14 so that the redioactive nuclides contaminating the inner wall of the reservoir 3 may be removed by the vertically sliding brush 8. This brush 8 is made to pass through a moving guide 10 by a wire 9 and is returned to a brush rinsing portion 13, which is composed of a chemically rinsing portion 11 and a water rinsing portion 12, so that the contaminants may be removed from the brush 8. During the rinsing operation, the sample liquid is stopped from flowing into, and the rinsing water is supplied from a tank 15.