Collective Dose Equivalent Research Articles

RADIOLOGICAL HEALTH IMPACT DUE TO ACTIVITY CONCENTRATIONS OF NATURAL RADIONUCLIDES IN THE SOILS FROM TWO MAJOR AREAS IN IJEBUNORTH LOCAL GOVERNMENT, OGUN STATE, NIGERIA

The soil samples from two major areas in Ijebu-North Local Government of Ogun State was analyzed for the concentrations of 40K, 226Ra and 232Th using gamma ray spectrometry method. The measured activity concentrations of 40K varied from 245.2 Bqkg-1 to 538.1 Bqkg-1 with a mean value of 367.9±74.1Bqkg-1 , 226Ra in the ranged from 10.4 Bqkg-1 to 30.2 Bqkg-1 with a mean value of 16.4±4.6Bqkg-1 and 232Th ranged from below detection limit (BDL) to 14.1Bqkg-1 with a mean value of 3.3±2.0Bqkg-1 . The mean external gamma absorbed dose rate in air at 1m above the ground level was 26.4±5.1 nGyh-1 which was just about one-half of 56.0 nGyh-1 recommended by UNSCEAR (2000). The mean annual outdoor effective dose rate was 32.3±6.3µSvy-1 . The collective dose equivalent was 9.18 manSv while the collective health detriment of the population was 0.15y-1 .

Collective dose estimates by the marine food pathway from liquid radioactive wastes dumped in the Sea of Japan

IAEA-MEL has been engaged in an assessment programme related to radioactive waste dumping by the former USSR and other countries in the western North Pacific Ocean and its marginal seas. This paper focuses on the Sea of Japan and on estimation of collective doses from liquid radioactive wastes. The results from the Japanese–Korean–Russian joint expeditions are summarized, and collective doses for the Japanese population by the marine food pathway are estimated from liquid radioactive wastes dumped in the Sea of Japan and compared with those from global fallout and natural radionuclides. The collective effective dose equivalents by the annual intake of marine products caught in each year show a maximum a few years after the disposals. The total dose from all radionuclides reaches a maximum of 0.8 man Sv in 1990. Approximately 90% of the dose derives from 137Cs, most of which is due to consumption of fish. The total dose from liquid radioactive wastes is approximately 5% of that from global fallout, the contribution of which is below 0.1% of that of natural 210Po.

Determinations of Organ or Tissue Doses and Collective Effective Dose Equivalent from Diagnostic X Ray Examinations in Japan

The frequency of diagnostic X ray examinations in Japan has been evaluated on the basis of the nationwide surveys of radiological examinations throughout the whole of Japan. For the determinations of organ or tissue doses, the technical factors for the radiological examinations were also investigated by the nationwide surveys. As an example of the results, the annual number of radiographs in 1986 totalled 497 million and the annual frequency of radiographic examinations was 141.5 million. The average number of the radiographs per examination was estimated to be about 3.5. The annual number of X ray CT examinations in 1989 was estimated to be 12 million. The resultant collective dose equivalent from X ray diagnosis including X ray CT was estimated to be about 2.4 × 105 person.Sv using organ or tissue doses determined with phantom measurements and the ICRP 1977 recommendation.

Radon: current challenges in cellular radiobiology.

Radon is by far the most important contributor to the collective dose equivalent. Most of what is known about the hazards of radon daughters comes from epidemiological studies of miners. There are a few well defined areas in which in vitro research can complement such studies: First, more data on the relative effects of differing energy (LET) alpha-particles would help: (1) understand the significance of the depth of sensitive cells in the bronchial epithelium--which varies between individuals, as well as between smokers and non-smokers, and between miners and non-miners; (2) understand the relative hazards of radon and thoron daughters. Second, reliable methods for predicting high LET responses from low LET response, would enable Japanese A-bomb survivor data to be applied with confidence. Third, understanding the effects of single-particle traversals of cells relative to multiple traversals could allow reliable extrapolation of epidemiological miner data to low exposures. Fourth, a better understanding of the nature of the interaction between tobacco and radiation damage would help predict the effect of radon on non-smokers.

Calculation of Individual Dose Equivalents on the Territory of Eastern Slovakia after the Chernobyl Accident

The accident in the nuclear power plant at Chernobyl in the USSR resulted in the release of substantial quantities of radioactive material and remarkable increases in radioactivity in the environment in many European countries. For an estimation of the accident consequences to population both the individual and the collective dose equivalents must be calculated. This paper deals with the calculation of the individual dose equivalents to persons living in the territory of eastern Slovakia. The calculation is based on real activity concentration measurements of environmental samples. For children the value of the total committed effective dose equivalent was calculated as 1.20 mSv, for adults it was 0.31 mSv

Trends in Radiation Protection of Medical Workers

Medical workers constitute the largest group of individuals occupationally exposed to radiation, and their collective dose equivalent is exceeded only by persons employed in the nuclear fuel cycle. Although medical workers have increased in number by about 50% over the past two decades, their collective dose has steadily declined. Factors that contribute to changes in the exposure patterns of medical workers include variations in demand for medical imaging procedures, changes in the way these procedures are administered to patients, and development of devices that utilize radiation more efficiently and display radiation-derived information more effectively. Trends such as the movement of imaging procedures into nonradiologic disciplines and nonhospital settings, and the imposition of economic and legal considerations into decisions about patient management and health care, may also ultimately affect the exposure of medical workers to radiation.

Use of a simulation model in occupational dose assessment at a high-level radioactive waste repository.

Occupational radiation dose assessment at a nuclear facility can benefit from a systems approach that recognizes the complex dynamics of the facility. A simulation model can be a useful tool for accomplishing this goal. This technique can quantify the uncertainty in estimates of occupational dose equivalent and illustrate the effects of system interactions. A simulation model of operations at a high-level radioactive waste repository together with a radiological dose assessment model were used to illustrate this technique. Annual individual and collective occupational dose equivalents were estimated in the truck cask receiving and handling stations at a repository. The uncertainty of these estimates is shown through the use of complementary cumulative distribution functions. The effects of changing parameters in cask handling operations are examined.

Changes in per capita and collective dose equivalent due to natural radiation in Taiwan (1950-1983).

This paper deals with the changes in per capita and collective dose equivalent in Taiwan in the past three decades based on the measured terrestrial and cosmic radiation levels and the population distribution as well. Over 70% of the population is concentrated in three population centers which have been naturally formed in the north, middle and south of Taiwan along the west coast as a result of industrialization and population growth. The population has increased 2.5 times in the past 33 y and reached to 1.9 X 10(7) persons, yet the migration of population was from the rural areas where the natural radiation is usually high to the urban areas where the natural radiation is usually low. The resulting collective dose equivalent has been increasing, yet the per capita dose equivalent, on the contrary, has been decreasing.

Radiation exposure to personnel in departments of gynaecologic oncology in Sweden.

Radium-226 and cesium-137 are used at six departments of gynaecologic oncology in Sweden. A survey of radiation exposure (dose equivalents) to the personnel is reported. The measurements were performed with TL dosemeters. From dose distribution measurements, the dose equivalents in different parts of the body, related to different working procedures, were determined. Effective dose equivalents and collective dose equivalents were also estimated. The estimated collective dose equivalent for this category of personnel in Sweden was 1.3 manSv. The effective dose equivalent was less than the dose equivalent measured with dosemeters worn on the chest, and was less than half the annual limit set by ICRP.

Personnel radiation exposure analysis in a radiotherapy center: Fourteen year retrospective study

The radiation exposure to the staff in the Ontario Cancer Institute between 1964–1977 was analyzed based on data from personnel film monitors. The annual collective dose equivalent was found to vary from 320 to 720 person-mSv. Of this, about 75% was attributable to the use of radionuclides for intracavitary and interstitial therapy, about 17% the use of external radiation therapy equipment, and the remaining, about 8% was equally attributable to diagnostic X ray and a mixture of many radiation sources used in research. The most influential factor to the annual collective dose equivalent was the number of patients treated with intracavitary and interstitial therapy. The dose per such application to this population was about .70 mSv, and was further broken down into .48 mSv to nurses in the wards where these patients were admitted, .11 mSv to personnel who handle these sources, .08 mSv to the operating room staff, and .04 mSv to the others. The collective dose per external radiation daily treatment was about .0008 mSv. For a course of 20 treatments, the collective dose equivalent will be in the order of .02 mSv. For diagnostic radiology, the collective dose per patient visit was in the order of 0.0003 mSv.

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.

Estimations of population doses and risk estimates from occupational exposures in Japan, 1978 Part 2. Population doses and risk estimates.

The population doses and risks of stochastic effects from occupational exposures in Japan in 1978 were estimated on the basis of a nationwide survey. The survey was conducted on annual collective dose equivalents by sex, age group and type of radiation work for about 82, 500 workers other than the workers in nuclear power stations. The data on the workers in nuclear power stations were obtained from the offitial publication of the Japan Nuclear Safety Commission. The total number of workers except for nuclear power stations was estimated to be about 170, 000 persons. Radiation works were subdivided as follows: medical works including dental; nondestructive inspectional ; non-atomic energy industrial; research and educational; atomic energy industrial and nuclear power industrial. The annual collective dose equivalents were estimated to be about 6, 000 man rem for medical workers, 450 man rem for non-destructive inspectional, 450 man rem for non-atomic energy industrial and 13, 300 man rem for nuclear power industrial, respectively. The population doses from occuaptional exposures in Japan were calculated to be about 0.14 mrad person-1 year-1 for the genetically significant dose, 0.15 mrad person-1 year-1 for per Caput mean bone marrow dose, 0.14 mrad person-1 year-1 for the leukemia significant dose and 0.07 mrad person-1 year-1 for the malignancy significant dose, respectively. The risks of stochastic effects to individual and the Japanese population from occupational exposures were estimated using the data on the annual collective dose equivalent to individual and on the population doses, respectively. The total risk of population was estimated to be about 4 persons year-1. The analyses of occupational exposures such as the dose equivalent per unit electrical power generated by nuclear energy or per radiological practice to patients were carried out.

職業上の被ばくの現状と問題点

The dose assessment of radiation workers from external exposure is principally carried out with the aid of personal monitoring device such as film badges or thermoluminescent dosimeters. This paper describes the present status of occupational exposures in Japan on the basis of the data concerning the individual annual cumulative dose equivalent by sex, age-group and type of radiation work which were obtained from a nationwide survey on the occupational exposure in 1978. According to the 1977 report of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and the Recommendations of the International Commission on Radiological Protection (ICRP), the collective dose equivalent, the special factor of dose distribution, Ω, and the index of harm for radiation-induced somatic and genetic effects were calculated from the cumulative dose equivalents determined with the personal monitoring devices.In spite of increasing in the number of radiation workers who must be monitored for neutron exposure, the collective dose equivalent of neutrons was negligibly small compared with the X and gamma-ray dose equivalent. In Japan, the NTA film badges are commonly used as the personnel neutron dosimeters for radiation-protection purposes. The problem of personnel neutron monitoring is discussed in this paper, together with the determination of quality factor. Also, this paper reviews a few problems in the determination of the effective dose equivalent and dose equivalent index.