Decontamination test of gravel; Establishment of effective decontamination methods about paving gravel and ballast

Kato, Mitsugu; Tanabe, Tsutomu; Umezawa, Katsuhiro ; Wada, Takao

After the Fukushima-Daiichi Nuclear Power Station accident, widespread contamination by radioactive materials occurred. Thus, decontamination work have been developed because of reducing air dose rate. Of this, in order to examine decontamination effect about gravel which cover sites of houses, communal facilities and cemeteries, and about ballast laid on a track, JAEA examined a decontamination test by physical plural methods. The objective of this testing is to establish rational and high effective decontamination methods to decontaminate each different gravel of materials and the shape, using the equipment which have possibility of the decontamination effect by trituration or blast. From the test results, applicability of the decontamination method depending on a characteristic of the gravel and the decontamination effect (reduction rate) are confirmed. There are various characteristics with the thing said to be gravel. It is confirmed that one decontamination method cannot be applied to all types of gravel. Furthermore, it is confirmed that there is great variability among individual polluted condition in the gravel gathered from the same place. Therefore, it is important to measure the degree of pollution so that a measurement error becomes as little as possible. For example, to measure plural points of the measurement side and keeping the height of measurement constant.