Effective Dose Equivalent Rates Research Articles

Photon shielding for 241Am surface and point sources.

To determine radiation protection requirements for work with actinide elements, a method for rapidly estimating effective dose-equivalent rates from low-energy photons has been developed. This paper describes results obtained from a personal computer program that incorporates the point kernel technique to predict radiation fields from shielded and unshielded sources containing 241Am. Information generated has been used to determine procedures and to design facilities for handling actinides at Argonne National Laboratory's site at the Idaho National Engineering Laboratory. Area or point sources can be treated; effects of Compton scattering in air and in solid shields are considered. Users can select an appropriate response function; their choice has a strong influence on predicted dose rates from unshielded sources.

Whole-Body Cesium 137 Activity up to 4 Years After the Chernobyl Reactor Accident in Premature Newborns, Newborns, Infants, and Children

Cesium 137 activity was measured after the Chernobyl incident in a whole-body radiation counter (4-pi-scintillation counter) in 85 premature and mature newborns (group 1), 174 infants and young children up to 2 11/12 years (group 2), and 48 children between 3 and 8 years (group 3) from Bonn (Germany) and surroundings. In 1987 the mean level of radioactivity in group 2, at 3.7 Bq/kg body weight corresponding to a mean radiation exposure of 11 muSv/y, was lower than that of group 1 (5.8 Bq/kg, 17 muSv/y) and 3 (9.4 Bq/kg, 28 muSv/y). Up to 1990 the values of all groups revealed a continuous decrease. The latest measurements showed mean values of 0.5 Bq/kg (1.5 muSv/y) in group 1, 0.6 Bq/kg (1.8 muSv/y) in group 2, and 0.8 Bq/kg (2.4 muSv/y) in group 3. A comparison with present cesium 137 values and determinations of the end of the 1950s and beginning of 1960s, both in adults, showed good agreement. The effective dose-equivalent rates amounted to less than 1% of that from natural radiation exposure. These levels should present no teratogenic risks to the population studied and, while there are theoretical mutagenic risks, the dose is so low that no increase in measurable mutagenic effects should be observed.

自然放射線における空気吸収線量から実効線量当量への換算係数の評価

A practical conversion factor to estimate the value of effective dose equivalent rate in Sv unit from absorbed dose rate in air in Gy unit was examined for natural gamma radiations. The experimental examination was carried out by two methods; one measures the effective dose equivalent rate directly by using a measuring instrument having effective dose equivalent response for isotropic gamma radiations and the other obtaines it from calculation applying the gamma flux-to-effective dose equivalent factor to actual gamma energy spectrum measured in various indoor and outdoor places.From these investigations the value of the quotient of effective dose equivalent to absorbed dose in air was found do be 0.748±0.007 Sv per Gy for natural radiation exposures in various environments. The value of the quotient 0.7, which is adopted to applied to environmental gamma radiations in the UNSCEAR 1982 and 1988 Reports, was clarified to be about 7% lower than the one obtained experimentally for natural gamma radiations.

Carbon-14 discharges from the nuclear fuel cycle: 1. Global effects

The radiological impact of 14C produced by the nuclear fuel cycle is assessed using an advanced 25-box model of the carbon cycle coupled with a range of feasible energy-use scenarios. In particular, this study estimates both the short- and long-term dose implications to the global population. In the former context, it is predicted that the atmospheric 14C specific activity in the year 2050 will be 234 Bq kg −1 (carbon), corresponding to delivery of an individual effective dose equivalent rate of 15 μSv year −1. The contribution of reactor-derived 14C to the individual dose rate increases steadily throughout this period, reaching 1·8 μSv year −1 in 2050, well within ICRP limits. In the longer term, however, the collective effective dose equivalent commitment is conservatively estimated at 141 man Sv TBq −1, corresponding to 480 man Sv (GW(e) year) −1. These figures indicate that 14C could generate one of the largest contributions to the total dose to man from nuclear power production.