Collective dose

In terms of health effects, none of the evacuees from the 30 km radius evacuation zone displayed any symptoms of radiation sickness. Their collective dose from external exposure wa.s estimated to be 1.5... 

Nielson SP, Iosjpe M, Strand P. 1997. Collective doses to man from dumping of radioactive waste in the Arctic Seas. Sci Total Environ 202 135-146. 

Collective dose—The sum of the individual doses received in a given period of time by a specified population from exposure to a specified source of radiation. Collective dose is expressed in units such as man-rem and person-sievert. 

The selection of the 1980-82 measurements (Swedjemark and MjOnes, 1984) was made on dwellings built before 1976 and with the aim of determining dose distributions and the collective dose to the Swedish population from the exposure of the short-lived radon decay products. This was done by using the statistical selection made by the National Institute for Building Research intended for an energy study of the Swedish stock of houses. From a selection of 3 100 houses in 103 municipalities, 2 900 were inspected. The data was found to be in substantial conformity with data from the land register and the population census of 1975. For the study of the radon concentration 752 dwellings were selected at random. 

All these comparisons support the hypothesis of an increase. The arithmetic means and thereby the collective doses seem to have increased by about a factor of four to six. If the aerated concrete based on alum-shale had not been used, the country-wide average has been estimated to be 30 % lower (Swedjemark 1985). 

For the collective dose, however, the decrease will be very slow because of the low building rate compared with the housing stock. It has been estimated tha the average for the Swedish radon daughter concentration, 50 Bq/m EER, may be decreased to half that value after about 100 years, if the requirements mentioned above are fulfilled. 

Ettenhuber E, Lehmann R. 1986. The collective dose equivalent due to the naturally occurring radionuclides in building materials in the German Democratic Republic. Part I External exposure. Health Phys 50 49-56. 

Several accidents in nuclear facilities have been extensively analyzed and reported. The three most widely publicized accidents were at Windscale (now known as Sellafield), United Kingdom, in 1957 Three Mile Island, Pennsylvania, in 1979 and Chernobyl, Ukraine, in 1986 (UNSCEAR 1988 Severn and Bar 1991 Eisler 1995). From the accident at Windscale about 750 trillion (T)Bq 22 TBq Cs, 3 TBq Sr, and 0.33 TBq °Sr were released and twice the amount of noble gases that were released at Chernobyl, but 2000 times less and Cs. From the Three Mile Island accident, about 2% as much noble gases and 50,000 times less than from the Chernobyl accident were released. The most abundant released radionuclides at Three Mile Island were Xe, Xe, and but the collective dose equivalent to the population during the first post-accident days was <1% of the dose accumulated from natural background radiation in a year. 

The unit used for expressing the collective dose to a population is the person-sievert (person-rem), which is the product of the number of people exposed times the average dose per person, e.g., 10 mSv to each of 1,000 people = 10,000 person-mSv = 10 person-Sv (1 rem to each of 1,000 people = 1,000 person-rem). 

The dose of radiation delivered by an internally deposited radionuclide depends on the quantity of radioactive material residing in situ. This quantity decreases as a function of the physical half-life of the radionuclide and the rate at which the element is redistributed or excreted (i.e., its biological half-life). Because the physical half-life is known precisely and the biological half-life can be characterized within limits for most radionuclides, the dose to a tissue that will ultimately be delivered by a given concentration of a radionuclide deposited therein can be predicted to a first approximation. The collective dose to a population that will be delivered by the radionuclide—the so-called collective dose commitment—serves as the basis for assessing the relevant long-term health effects of the nuclide. 

The calibration of the in-line detector is accomplished by comparing the end-of-elution collected dose (as measured in a dose calibrator) to the differential elution profile (as measured by the in-line detector). With data collection at 1 sec intervals, a... 

Rb-82 yield improves at faster flow rates with less activity being lost to decay. Integral outputs are shown in Figures 5 and 6. These values represent, respectively, the administered dose and the collected dose. The former data, which represent the integrated dosimeter readings of the on-line detector, must be considered in establishing the duration of infusion consistent with... 

Recommendations on Exemption Principles. IAEA has developed recommendations on general principles for exemption of radioactive material from regulatory control (IAEA, 1988). Any practice or source could be exempted from regulatory control if (1) the annual dose to individuals would be less than 10 xSv and (2) the annual collective dose from an unregulated practice would be less... 

Principles and Application of Collective Dose in Radiation Protection (1995)... 

Hadditional dose commitment by a risk coefficient and a value of individual (collective) dose. The life-long risk coefficient characterizes reduction of the duration offull-valuelifeby 15 years (on average) per one stochastic effect (due to fatal cancers, serious hereditary effects and non-fatal cancers with similar-to-fatal-cancer consequences). 

Another dose concept is that of the collective dose. It is based on the assumption that cancer is induced by a stochastic single process, independently of the dose rate and the dose fractionation, and it imphes that the detriment is the same whether one person receives 20 Sv or 20 000 persons receive 1 mSv each. In both cases the collective dose is 20 man sieverts (man Sv) and there should be a 100% probability of one disease of cancer. The collective dose concept is often apphed to assess the effect of the natural radiation background. At an average level of 3mSv/y, 0.015% of the population should die each year due to natural radiation. As the frequency of deaths by cancer is about 0.2% per year, it is not possible to confirm the collective dose concept by epidemiological investigations. 

Similai ly, a collective committed dose is obtained by integrating the collective dose. 

It is estimated that between March 28 and April 15, the collective dose (total population dose) resulting from the radioactivity released to the population living within a 50 mile radius of the plant was 2000 person-rems. The estimated annual collective dose to this population from natural background radiation in this area is 240 000 person-rems. Thus, the increment of radiation dose to persons living within a 50 mile radius due to the accident was somewhat less than 1 % of the annual background level. 

For simplicity, we consider only whole body doses although the collective dose concept is equally useful for organ or tissue risk evaluations (mine workers, thyroid patients, etc). In the equation, / refers to a situation where each of the n persons has received differ t personal doses, j. 

For example, in the Chernobyl accident (1986), it is estimated that the 24000 people that were evacuated from the Pripyat area received a collective dose of 11 000 manSv. According to (18.4), this would mean an expected increase in cancer incidents of 550 cases spread over the lifetime of these people. 

The collective (effective) dose concept is commonly applied to natural radiation background. At an average level of 3 mSv/y 0.015% (18.4) of the population should die of cancer each year from natural radiation. For a population of 50 M people, the collective dose becomes 150 000 manSv/y and corresponds annually to 7 500 additional cancers (out of an expected 100000 cancer deaths/y). Consequently, the background radiation may be responsible for about 5 — 10% of all cancers a more prudent statement is 10% of all cancers". This claim is not possible to confirm by epidemiological investigations. 

Suggestions have been made to also apply the collective dose concept to chemical poisons. We illustrate the consequence of this with an example copper is a natural and needed constituent of our body (0.00010%) that takes part in enzyme reactions. However, an amount of 6 g of copper as a salt is lethal minimum lethal dose). Using the collective dose concept, one finds that one of every 6 X10 persons should die of copper poisoning. This is a condition for which there is no scientific support. 

The collective dose concept allows for extrapolation of the consequences from large scale introduction of nuclear power, which, in turn, establishes the need to ensure that the total annual dose stays within agreed safe limits. If it is assumed that fission power will be used for only about 1(X) y, the dose commitment integral may be limited to 100 y (sometimes called "incomplete collective dose"). 

Legal release limits are usually set so that a critical groiq> of the general public should at most get an insignificant additional dose, typically 0.1 mSv/y. It is also customary to put a legal limit on the collective dose (usually per GW installed gmerating capacity) arising from operation of a nuclear power plant. 

Kr, Tc and are of major concern. The liquid effluents firom nuclear power plants and from reprocessing plants are about equally responsible for the global collective dose commitment of nuclear power generation (i.e., 0.8 man Sv per GW y of the total 2.5 man Sv). 

Atmospheric discharges have been well within the limits and within the range of 2 to 10 Ci/day (522 Ci/year in average) and they tend to decrease there have actually been no liqiud radioactive effluents from the plant while it being operated. The average release of the solid radioactive waste is 22 mVyear. The average collective dose of the plant personnel is 84 rem/year. 

How can we evaluate the year 1997 with respect to safety problems This was not a typical year for Minatom. According to impartial assessments, Minatom achieved its best results in 1997. Our Ministry experienced the lowest level of traumatic injuries in the history of plant operations on the basis of sampling done for more than 40 years. We achieved the lowest level in Russia of traumatic injuries. At our plants, the lowest rate of worker death was achieved 0.006-0.06 man per 1000 workers. As to radiation factors, the least collective dose was attained for all technologies, including fuel cycle. But, in 1997, we had a fatal accident caused by radiation. A research engineer from an institute in Sarov received an absorbed body dose of 5000 rad and died. This was a shocking situation for Minatom. Ten years after the Chernobyl accident, we were faced with the fact of death from radiation. 

The interesting data concerning the risk for man and the environment from atomic engineering were reported by M. Dreicer et al. [1]. In a calculation for the population of 10 billion men for 100,000 years, the collective dose from all the stages of the Nuclear Fuel Cycle (NFC) makes 13 man Sv/ (TW hour). 

The upper bound estimate of collective dose (external + internal) for this project is 644 man-mSv over a 7-year duration, with the highest individual dose being <15 mSv (external + internal) over any 12-month period. 

Comprehensive radiation survey has been carried out to ensure shielding efficiency in the cells having primary radiation components and cover gas system. The measured dose rates have been found to be less than the design values. The average annual collective dose is 2.2 P-mSv. This indicates very low radiation exposure from the plant. 

---