Since 1987 through 1990, we have observed in diurnal and seasonal variation of radon concentration in and out of the house in Shanghai urban district. The equilibrium factor between radon and radon decay products of in- and outdoors environment was estimated to be 0.5 and 0.7 respectively. The indoor radon concentration was estimated to be 9.92±1.66 (GSD) Bq/m3 and the outdoor radon concentration was estimated to be 4.25±1.75 (GSD) Bq/m3 in Shanghai city. The occupancy factor at urban district was estimated to be 0.82 indoors and 0.18 outdoors for adults, 0.87 and 0.13 for children. In 1989 the population-weighted annual effective dose in Shanghai city was estimated to be 0.39mSv, and the annual collective effective dose was 5, 000 manSv, which may cause the excess lung cancer death up to 277 cases among 12, 767, 500 people that accounted for 6.0% of total number of the lung cancer death.
It is very important to know characteristics of the variation of ultraviolet radiations (UVR) in the natural environment for planning radiation protection on the basis of quantitative risks of the UVR. From this point of view, observation of diurnal and annual variations in the natural environment has been carried out using a portable UVR irradiance meter from May 1991 to April 1992. It is quite possible from the diurnal variation that the UVB scattered in the sky become significant when the sun approaches the horizon and from the annual variation that UVB irradiances become weaker than expected ones in summer. It is apparent that the UVA scattered in the sky vary depending on the surroundings of measuring points and that remarkable seasonal variations can be seen in the UVB scattered in the sky.
This paper is concerned with an optimal planning in a multiple objective decision-making problem of allocating radiation workers to workplaces associated with occupational exposure. The model problem is formulated with the application of goal programming which effectively follow up diverse and conflicting factors influencing the optimal decision. The formulation is based on the data simulating the typical situations encountered at the operating facilities such as nuclear power plants where exposure control is critical to the management. Multiple goals set by the decision-maker/manager who has the operational responsibilities for radiological protection are illustrated in terms of work requirements, exposure constraints of the places, desired allocation of specific personnel and so on. Test results of the model are considered to indicate that the model structure and its solution process can provide the manager with a good set of analysis of his problems in implementing the optimization review of radiation protection during normal operation.
Effects of a new type of calcium product (Seaweed-calcium complex: SWCa) and combination of SWCa and Ca-DTPA on removal of injected 239Pu were examined in rats. SWCa is a natural product consisting of mixed calcined oyster shell (COS) which is composed of calcium salt probably in the form of calcium oxide and a natural material extracted from seaweed to transport calcium actively throughout the small intestine. In experiment I, a 2% solution of SWCa, COS, CaO, CaCl2 or CaCO3 was injected into the small intestinal loops of rats to compare the intestinal absorption rate of each calcium salt. In experiment II, 25 male Wistar rats, 3 months of age, were divided into five groups given; a control diet with 1% CaCO3 (group A), a SWCa diet with 1% SWCa to replace the 1% CaCO3 after plutonium injection (group B), a SWCa diet 1 week before plutonium injection until the end of the experiment (group C), a SWCa diet and intraperitoneal injections of a daily dose of 150μmol/kg of Ca-DTPA (group D), and a control diet and intraperitoneal injections of the same dose of Ca-DTPA as group D (group E). The rats were injected intravenously with plutonium, 1.85×104Bq/kg, and killed 14 days later and the femur and liver were excised. All excreta were collected at 24-h intervals during the experimental period. The plutonium concentration was measured by a liquid scintillation spectrometry after a wet ashing treatment. The levels of serum total and ionic calcium were elevated more rapidly and were higher after the injection of SWCa than after those of COS, CaO and CaCO3. The percent of plutonium content to administered dose in the skeleton was 69.3, 63.6, 58.8, 10.4 and 19.0%, and that in the liver was 7.74, 6.93, 6.43, 0.22 and 0.35% for groups A, B, C, D and E, respectively. The plutonium contents in the urine and feces were increased during the first 2-3 days after plutonium injection in the SWCa groups. The results indicated that the elevation of serum calcium by the oral administration of SWCa could lower the plutonium content in the skeleton and liver both before and after plutonium injection and the effects were increased by the combination of SWCa and Ca-DTPA. In conclusion, SWCa not only lowered the plutonium content after exposure but also prevented plutonium deposition in the bones and liver.
In a previous paper, we reported on the yearly trends during 1973-1983 in the occupational deaths in seven categories of industry in Japan (forestry, fisheries, mining, construction, manufacturing, transportation and communication, and electricity, gas, water, steam and hot water supply). The accidental average death rate in seven occupational industries was 141per million per year. In the present study, these data were extended to 1990. The accidental death rate of all seven industries showed a tendency of decrease year-by-year. However, the accidental death rate of mining was still high (821per million per year) and then has decreased in forestry, fisheries, construction, the most safety industry being electricity and others supply (19per million per year). The averaged accidental death rate of all seven industries during 1984-1990 was 85per million per year. Trends with time in fatal accident rate during 1973-1990 were calculated about 1.86per annual change in forestry and 4.87 in electricity and others supply, respectively. Compared with those figures in ICRP or other countries, the accidental death rates in industries in Japan were more rapidly decreased.
When we obtain public acceptance for the peaceful use of atomic power, one way is to compare the radiation risks with other various risks, for example risks from occupational or daily-life accidents. In the present paper, the fatality risks from accidents in various leisure sports and accidents in daily life were assessed during the period of 1981-1989. The risks were calculated as the ratio of the number of deaths to the population of all Japan or the population that participated in each leisure sport, respectively. The average actual death numbers per year during 1981-1989 examined were 413 in fishing and 387 in swimming at sea, the risk being 1.0×10-5 and 2.5×10-5, as expressed in participated population. The most dangerous sport is sky-diving from a paraglider or parachute, although the actually participated population is very small. The average risk is about 1.0×10-5 in all leisure sports, 1.1×10-5 in aquatics, 6.4×10-6 in land sports and 4.0×10-5 in aerosports. These risks were compared with fatality risks from occupational accidents (8.5×10-5), car accidents (1.0×10-4) and the accidents at home (5.0×10-5) as well as cancer risk per Sv proposed by ICRP.
A calibration method has been studied for the surveymeters used for estimating the doses from skin contamination. Two types of surveymeters with ionization chamber and GM tube were calibrated with newly developed β-ray sources simulating skin contamination. Ion-exchange membrane sources were used for preparation of the calibration sources. The tissue absorbed dose rates from the sources were directly determined with an extrapolation chamber. The ratios of the reading of surveymeter to the dose rate from the sources were measured about maximum β-ray energy, active area and source-to-detector distance. The ratios for the infinite plane source were reasonably determined with 6 calibration sources and many small membrane sources. Through the calibration works, the validity and reliability of this method were discussed.
By using a NaI(Tl)/CsI(Tl) phoswich detector we have developed a method to measure radioactivity of Pu in various types of solid samples. The minimum detectable radioactivity for 33% error was proved to be 0.64Bq for 1h counting and 0.11Bq for 24h counting. This method can save plenty of time for sample preparation and can preserve the condition of the sample for other research purposes. This method also ensures radiation safety, because the sample can easily be sealed. In biological studies of inhalation toxicology of Pu, we are using this method for activity measurement of solid samples such as air sampling filters, elements of cascade impactor or animal tissues.