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Togawa, Orihiko; Hokama, Tomonori; Hiraoka, Hirokazu; Saito, Shota
JAEA-Research 2023-011, 78 Pages, 2024/03
When radionuclides are released into the atmospheric environment at a nuclear emergency, protective measures such as evacuation and temporal relocation are carried out using motor vehicles such as private cars and buses to reduce radiation exposure to residents. To confirm conditions of contamination for the evacuated/relocated residents and the used motor vehicles, contamination inspection is conducted in the middle of the route from border areas of Nuclear Emergency Planning Zone to evacuation shelters. In the present inspection in Japan, a value of OIL4 = 40,000 cpm is used as decontamination criteria. For the details and derivation methods of the value, however, no official documents are found which give systematically detailed descriptions and explanation. It is also recognized that even few experts on nuclear emergencies can explain these subjects in detail as a whole. In order to explain scientifically and technically the OIL4 value of decontamination criteria used in contamination inspection in Japan, this report aims at investigating and estimating the deviation methods of OIL4, and examining and considering these results. To achieve the objectives, we show the bases for decontamination criteria, and investigate and estimate the derivation methods for limits of a surface contamination density corresponding to the generic criteria for each exposure pathway. Moreover, we give the OIL4 value some consideration and suggestions from a viewpoint of positioning and feature of OIL4 in Japan, and cautionary points at revising the value.
Iyoku, Tatsuo; Takikawa, Noboru*; Shiozawa, Shusaku; Sawa, Kazuhiro; *; Yamada, Kunitaka*; Sugihara, Tetsuya*
JAERI-M 93-002, 28 Pages, 1993/01
no abstracts in English
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Journal of Nuclear Science and Technology, 16(10), p.750 - 763, 1979/00
Times Cited Count:0no abstracts in English
Wakui, Takashi; Wakai, Eiichi; Naoe, Takashi; Kogawa, Hiroyuki; Haga, Katsuhiro; Takada, Hiroshi
no journal, ,
A mercury target vessel has been used for the spallation neutron source at J-PARC. It has a complicated multi-layered structure composed of a mercury target and surrounding double-walled water shroud, which is assembled with thin plates (minimum thickness of 3 mm) by welding. Thus, welding inspection during the manufacturing process is important. We investigated the applicability of new ultrasonic inspection, named as phased array ultrasonic method, to improve the accuracy of welding inspection for the mercury target vessel. It was measured that the new ultrasonic method could detect a 1-mm-long defect formed in a 3-mm-thick specimen with an error of about 7%. Moreover, simulations of the phased array ultrasonic method demonstrated that the outline of a 0.5-mm-long defect in a thin specimen got clearer in an ultrasonic echo image with increasing frequency of the sensor, suggesting a possibility of further improvement.