Measurement of depth-directional radioactive cesium distribution in soil with several detectors

It was found that the depth-directional distribution of radioactive cesium in soil could be roughly estimated with imaging plate strips, glass dosimeter fibers or a tube with built-in Si PIN photodiodes, which were put into the ground. Especially, it was confirmed that ordinary and inexpensive Si PIN photodiodes could be satisfactorily used as beta-ray detectors. The response of the photodiode to beta-rays and gamma-rays was examined by use of a ¹³⁷Cs standard checking source. The pulse height distributions of the photodiode showed that it had sufficiently higher detection efficiency for beta-rays than for gamma-rays and also detection signals of beta-rays from radioactive cesium could be successfully discriminated from gamma-ray background and electromagnetic noises. (author)