The smear test is one of the important ways to measure surface contamination. The loose contamination under the high back-ground radiation, which is more significant in handling non-sealed radioisotopes, can be evaluated by this method. The removal factor is defined as the ratio of the activity removed from the surface by one smear sample to the whole activity of the removable surface contamination. The removal factor is greatly changed by the quality and condition of surface materials. In this study, the values of removal factor at several typical surface conditions were evaluated experimentally and the practical application of those values was considered. It is required the smear should be pressed by moderate pressure when wiping the surface. The pressure from 1.0kg to 1.5kg per filter paper was recommended. The removal factor showed lower value in wiping by the pressure below 1.0kg. The value of 0.5 for the removal factor could be applied to the smooth surface of linoleum, concrete coated with paint or epoxy resin, stainless steel and glass with the statistical allowance.

View full abstract

The bio-kinetics of radon ingested from drinking water was investigated for eight Japanese subjects. A whole-body counter at National Institute of Radiological Sciences (NIRS) was used for the measurement of the ²¹⁴Bi transfer half-life from the stomach to the small intestine. The transfer half-life seemed to be affected by water quality (chemical/physical properties) as well as the meal ingested before the experiments. The shortest transfer half-life among the subjects was about 50 minutes. During the whole-body counting, the air expired by the subjects was sampled and its radon concentration was measured using two ionization chambers. The changes in radon concentration in the expired air could be classified into three patterns. (1) It decreased with time after ingestion. (2) A peak appeared at the 15 minutes after ingestion. (3) A peak appeared at the 25 minutes after ingestion. These patterns seemed to be related to the ²¹⁴Bi transfer half-life and the amount of ingested water.

View full abstract

Application of coal combustion ashes in building materials has been limited by the presence of minor components such as radioactive substances. ²²⁶Ra, ²³²Th, and ⁴⁰K accumulated in the ash during the burning of the coal may result in significant, several doses of mSv annually. Radon exhalation is usually low, but in some cases a significant dose (5-15mSv/y) may be calculated upon due to the ²²²Rn emanating from this kind of building materials. Therefore a radiological survey, classification of these materials is necessary before utilization.

View full abstract

The Japan Atomic Energy Agency (JAEA) has carried out expeditions in the Japanese and Russian exclusive economic zones (EEZ) of the Japan Sea for 10 years to clarify seawater circulation and transport processes of radionuclides in the sea. The Japan Sea expeditions by JAEA started with its participation in the Japanese-Korean-Russian joint expeditions of 1994 and 1995. Through 18 expeditions, JAEA succeeded in covering almost all areas of the Japan Sea that can be observed at present. As a result, for the first time, JAEA has made distribution maps of anthropogenic radionuclides in the Japan Sea and outlined the transport processes of radionuclides in the sea. Furthermore, we also obtained the results on water circulation and oceanographic features of the Japan Sea. This review summarizes representative and important results obtained in the Japan Sea expeditions by JAEA. The dataset on the distribution of anthropogenic radionuclides established by this study provides background data in assessing the radiological consequences in cases of radioactive waste disposal in the sea or nuclear emergency response to accidental releases of radionuclides in or near the Japan Sea.

View full abstract

The study on the establishment and maintenance of the traceability on radon measurements at the Ningyo-toge Environmental Engineering Center of the Japan Atomic Energy Agency (JAEA Ningyo-toge) is illustrated in this paper. The primary standard is a radium solution provided by the National Bureau of Standard (present the National Institute of Standards and Technology) in the USA, and the secondary standard is the method with gas-filled ionization chambers calibrated with the solution. The radon reference chamber is utilized to provide reference atmospheres in calibration experiments for other monitors. Through the intercomparison experiments among the international reference institutes, it was confirmed that the reliability and consistency of the secondary standard of the JAEA Ningyo-toge have been retained since 1984. It shows that the calibration and measurement techniques associated with the traceability system constructed have been maintained well at the JAEA Ningyo-toge. Since there is no reference field as a national standard and no method regulated by the Japanese Industrial Standard, this paper provides not only reliability and accuracy of the radon measurements at the JAEA Ningyo-toge, but also useful information for the standardization of radon measurements in Japan.

View full abstract