Man Sv Research Articles

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.

Radiation doses in countries of the northern hemisphere from the chernobyl nuclear reactor accident

Abstract Radionuclides released from the Chernobyl accident have been dispersed throughout the Northern Hemisphere. Values are collected here of the estimates so far provided of the resultant radiation exposures in countries. The collective effective dose equivalent commitment is of the order of 800,000 man Sv. Average individual dose commitments outside the USSR range up to 4 mSv, which is approximately twice the normal annual dose from natural background radiation. The estimated average doses in countries decrease in a regular fashion with distances from the accident site.

Carbon-14 discharges from the nuclear fuel cycle: 2. Local effects

Environemtnal 14C levels around various types of nuclear installations within the UK have been monitored during recent years. Enhanced 14C levels have been detected around both the nuclear fuel reprocessing plant as Sellafield and the thermal nuclear power station complex at Hunterston. From these measurements, the radiological impact of the 14C discharges on the local population is assessed. It is conservatively estimated that the 14CO 2 emissions from Sellafield between 1952 and 1985 could have delivered an 8·4 man Sv collective effective dose equivalent commitment to the population living within 40 km of the site. The maximum possible collective dose to the population within 15 km of Hunterston in 1984 was 15 × 10 −3 man Sv. Conservative estimates of maximum annual effective dose equivalents to individuals around Sellafield and Hunterston are 0·2 mSv (in 1982) and 12 μSv (in 1984), respectively. These dose levels do not exceed the limits recommended by ICRP but the former value clearly indicates that, for the larger discharges at least, consideration and optimisation of 14C releases are fully justified. The same 14C measurements are also used to test the validity of two atmospheric dispersion models, the Gaussian plume and the so-called ‘hyperbolic’ models. The former is excellent in predicting downwind 14C levels around Hunterston but is unsatisfactory when applied to Sellafield, whereas the latter proves reliable at both sites. Further investigations suggest that the Gaussian plume model's poor performance at Sellafield can be explained by inaccurate input data.

Consequences of the Chernobyl reactor accident on the 137Cs internal dose to the Japanese population

The consequences of the Chernobyl reactor accident on the Japanese population are assessed here, for the one-year period from May 1986, in terms of the internal dose due to 137Cs. The calculations are made via an approach which combines whole body counting with analysis of food intake data. First, the dose from 137Cs is assessed, for a group of healthy adult males, on the basis of their observed body burdens of 137Cs determined by whole body counting. The annual individual dose estimate thus obtained is 1·5 μSv, which is 6–15% and 3·7% respectively of the doses determined by whole body counting in UK and the Federal Republic of Germany. The temporal change in the average body burden is successfully explained here by a single-compartment model. Secondly, this latter model is used, along with the daily 137Cs intake data for each district in Japan, to calculate the dose for the whole of Japan. Appropriate values were chosen for the relevant biological parameters for each age and sex group. The estimates of the population dose and the average individual dose thus obtained are 148 man Sv, for the population of 120 million, and 1·24 μSv, respectively. Although comparatively small, these values nonetheless also include the residual contribution from past nuclear weapon tests. The average annual individual dose of 1·24 μSv corresponds to 0·7% of the dose from natural 40K in the body. Although whole body counting indicates that 137Cs burdens were still increasing as of May 1987, it is concluded that, in terms of radiocaesium, the effect of the Chernobyl reactor accident on Japan was negligible.

The Chernobyl reactor accident and the aquatic environment of the UK: a fisheries viewpoint

The monitoring programme undertaken by the Directorate throughout the UK following the Chernobyl reactor accident is described. The results of sampling and analysis of fish, shellfish, seaweed and other materials are discussed. Chernobyl fallout was readily detected in all sectors of the aquatic environment, particularly during May when the highest concentrations were observed. An assessment of the radiological impact of the fallout shows that freshwater fish were the most important source of individual (critical group) exposure though, based on cautious assumptions, the effective dose equivalent is around 1 mSv in a year. The collective effective dose equivalent commitment from Chernobyl due to aquatic ingestion pathways, predominantly marine fish, is estimated to be 30 man Sv.

Occupational Radiation Doses in Norway 1981-1983

Annual occupational radiation doses for 1981-1983 from the four personal dosimetry services in Norway are reported. For 1983, the data include all occupationally exposed workers being monitored. Unrecorded collective doses, due to individual exposures below the detection limit, are calculated on the basis of log probability distributions. For 1983, a total collective dose of 5.75 man Sv for medical occupations is calculated, giving a relative collective dose of 1.39 man Sv per 106 population. The mean individual annual dose for industrial radiography is calculated to 1.33 mSv. These figures take into account estimates of the collective doses below the detection limit.

An assessment of the radiological impact of the Windscale reactor fire, October 1957.

On the 10th and 11 October 1957 a fire in the No 1 Pile at the Windscale establishment in Cumbria led to an uncontrolled release of activity to the atmosphere. The resultant cloud subsequently dispersed and radionuclides could be detected over England, Wales and parts of northern Europe. The extensive environmental measurements which were made during and after the release enabled a fairly accurate estimate to be made of the radiation doses to the most exposed individuals in the local population. Until recently, no estimates of the population dose resulting from the release had been published. This paper describes assessments which have been made by the NRPB of the population or collective dose from the release and of the possible associated health impact. In addition to the fission products that escaped, radionuclides were released from materials undergoing irradiation in the pile at the time of the fire. The assessment has included the results of a review of previously unpublished data which established the quantity of these nuclides released and considers their impact on both individual and population doses. The collective effective dose equivalent commitment from the release is estimated to have been 2.0 x 10(3) man Sv. The route of exposure which contributed the most to the collective dose was the inhalation pathway. Iodine-131 was the most important radionuclide, contributing nearly all of the collective dose to the thyroid and a large part of the collective effective dose. Polonium-210 and caesium-137 also made significant contributions; that from caesium-137 came in the longer term via external irradiation from ground deposits and the ingestion of contaminated foodstuffs. The methodology used in the study has been validated to a certain degree by comparing the predicted levels of individual thyroid activity and those measured directly in the weeks following the accident in London, Leeds and Cumbria.

Collective doses and risks from dental radiology in Great Britain.

The continued expansion of dental radiology in Britain up to the end of 1981 is demonstrated, with a rate of increase much in excess of that seen for general medical radiography. Of the total of 7.8 X 10(6) dental X-ray examinations undertaken in 1981 approximately 6.7 X 10(6) were intra-oral, 1.5 X 10(5) were extra-oral and 9.1 X 10(5) were pantomographic. Weighted dose equivalents for typical examinations in each of these categories were calculated using specific weighting factors for the important "remainder" organs. Values of 20 muSv, 30 muSv and 80 muSv were obtained for intra-oral, extra-oral and pantomographic techniques, respectively, corresponding to risks of fatal malignancy of 0.33, 0.5 and 1.3 per million. The estimated collective weighted dose equivalent of 212 man Sv to the population of Britain from the current level of dental radiology is predicted to result in no more than about three extra cases of fatal cancer when the age- and sex-related opportunity for manifestation of radiation-induced cancers is taken into account.