Concentrations of uranium contained in the front glass of CRT (cathode ray tube) for television sets are measured by two methods: fission track counting and radioactivation analysis. The measurements are also made for other kinds of glass such as a laboratory dish. Systematic errors in the present experiment are shown to be less than about 15% for the uranium concentrations more than 3 ppm from the comparison between the results obtained with these two methods. Moreover, it is presented that the uranium concentrations obtained are 0.4-12ppm for the glass of CRT, whereas they are 0.2-0.7ppm for other kinds of glass. The presence of nuclides of uranium series should be, therefore, taken into account for measuring exactly the radiations near the front glass of CRT.
Effects of CBMIDA [catechol-3, 6-bis(methyleiminodiacetic acid)] on injected 239Pu were examined in rats; in our previous studies, CBMIDA had almost the same toxicity as those of DTPA and EDTA. Rats were injected intravenously with 239Pu (1.85×104Bq/kg) and divided into four groups of five rats each. Three groups were each injected intraperitoneally with a daily dose of 150μmol/kg of CBMIDA, Ca-DTPA or Zn-DTPA for 2 weeks, beginning at about 1h after plutonium injection. Rats were sacrificed 14 days later and the femur and liver were removed. All excreta were collected at 24-h intervals during the experimental period. Plutonium contents of the femur, liver, feces and urine treated by a wet ashing method were measured by a liquid scintilation spectrometry. The plutonium contents in the skeleton of administered dose were 11.5% for CBMIDA group, 19.0% for Ca-DTPA group, and 26.9% for Zn-DTPA group, whereas that was 63.9% for the control; those in the liver were 0.62% for CBMIDA group, 0.35% for Ca-DTPA group and 0.54% for Zn-DTPA group, whereas that was 7.74% for the control. The data obtained indicate that CBMIDA is superior to Ca-DTPA and Zn-DTPA on removing plutonium from bone, and also has almost the same effectiveness on removing it from liver as those of both Ca-DTPA and Zn-DTPA. The higher effectiveness of CBMIDA on removal of plutonium from the skeleton might be, besides the stronger chelating action, due to the inhibition of plutonium deposition into bone, judging from the results of our previous study wherein the effects of CBMIDA on bone metabolism were examined in beagle dogs. In conclusion, taking together the results obtained in this study and those from our previous studies on the toxicity, it was demonstrated that CBMIDA could be utilized, as a new chelating agent, to remove plutonium from human body.
Radiation fields of minimum ionizing charged particles were surveyed in the East Counter Hall of KEK 12-GeV Proton Synchrotron using a CsI (Tl) scintillation telescope. Existence of stray fields of minimum ionizing charged particles was confirmed and their characteristic features were investigated. As foreseen, they are formed downstream of the beam lines with cone figure. Effective energies evaluated from attenuation with iron absorbers was 1GeV, provided the response of the detector was only due to muons. Dose equivalent rate at the point was 0.66μSv/h.
Internal dose coefficients for ingestion and inhalation of radioiodine were preliminarily calculated considering the metabolic characteristics of Japanese. In the calculation, the fractional uptake by thyroid (f) of iodine entering blood and biological half-life in thyroid (Tb) were reflected among the data peculiar to Japanese concerning thyroid structure and iodine metabolism in thyroid. A metabolic model for iodine used here was based on the three-compartment recycle model described in the ICRP Publication 30. As to the parameters of f and Tb, the values of 0.2 and 40 days reported for Japanese were used instead of those of 0.3 and 80 days adopted by ICRP. The dose coefficients for Japanese calculated here are smaller than those for Reference Man of Caucasian. The author expects that the coefficients will be used for radiation protection purpose for workers and adults of the public in Japan.
Exposure to cosmic radiations in airflights and space missions are discussed. First, physical properties of the cosmic radiations including origins, compositions and energy spectra of galactic cosmic rays as well as solar particles are outlined, and main factors which influence the cosmic ray strength like solar activity and geomagnetism are presented. Structures along with formation mechanisms of the magnetosphere and Van Allen belt (radiation belt) are also mentioned. Second, exposure data measured in air and space vehicles are presented, and countermeasures to protect crews of foreign flights are introduced. Lastly, exposure control on space activities which is temporarily suggested is briefly mentioned in relation to the coming international experimental station in space.