JPS5458079A - Monitor for radioactivity in dusts - Google Patents

Abstract

PURPOSE: To prevent accumulation of radioactivity on unnecessary filter paper by measuring the radioactivity of dusts for a time from the start of dust collecting operation to the instant when the radioactivity takes a preset level or a level lower than the former so that the concentration of the radioactivity in the dusts may be obtained from the measured value and that time.

CONSTITUTION: When control command signals to a next step are fed from a comparator circuit 18, a control device 16' feeds the signals to a filter paper drive device 20, a sampling device and a time measuring circuit 19 so as to measure the gases at the next point. Clean filter paper 13 is fed to a radioactiviry detector 15, and a pump 20 is operated so that the gases are fed to the filter paper through an electromangetic valve which is opened in accordance with the next measuring point. When the dust collected are increased as the time elapses while containing radioactive substances, the output level of the detector 15 is increased to a preset level. Then, control command signal to the next step are fed from the circuit 18 to the circuit 16' and further to the circuit 19. In response to these signals, the device 16' feeds the command of the initial condition to the device 20, the sampling device and the circuit 19

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