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Izaki, Kenji; Noda, Kimio; ; Kashimuta, Yoshio*
JNC TN8410 2001-005, 30 Pages, 2001/01
JNC-TN8410-2001-005.pdf:0.62MB
Stack monitoring is the most important work in radiation control works. Exhaust monitors used for stack monitoring have the background (which is the counts by natural radio-nuclides) on normal condition, and the values of the background vary with the facilities. Therefore, if the value of background is high, it is difficult to estimate rapidly the radioactive concentration in the exhaust. In order to estimate rapidly the radioactive concentration in exhaust, we analyzed the behavior of natural radioactivity in the facilities and examine the technique fo reducing the value of the background. As a result of the examination, we found that it is possible to estimate rapidly if we change over the monitoring point to immediately after the HEPA filters on the exhaust duct. In this reports, the analyzed results of behavior of natural radio-nuclides in the facilities and the technique for reducing the values of the background are described. To reduce the value of the background has a major effect on not only rapidly estimating the radioactive density in the exhaust but also finding the unusual things on stack monitoring.
Morishita, Yuki; Yamamoto, Seiichi*; Izaki, Kenji; Nemoto, Norio; Kashimuta, Yoshio*
no journal, ,
Nuclear fuel materials such as uranium and plutonium were handled at a nuclear fuel facility. Early detection of a contamination due to these materials is important to prevent internal exposure of workers. ZnS(Ag) scintillation detector has been widely used to detect these materials by measuring alpha-particles. It cannot directly measure narrow space. ZnS(Ag) scintillation detector does not have an ability to distinguish nuclear fuel materials from naturally occurring alpha emitters such as radon daughters. To solve this problem, we developed a new imaging detector named "flexible alpha camera". We actually measured plutonium specimen and radon daughters by the flexible alpha camera. In the result of 2-dimensional distribution, plutonium specimen was imaged as point. Spatial resolution of plutonium specimen was only 0.36 mm FWHM. Plutonium was distinguished from radon daughters based on differences of 2-dimensional distribution and energy by using the flexible alpha camera.