Natural radiation background

The presence of radiation in the workplace - which is an inevitable consequence of the radioactivity of uranium - requires that additional safety precautions be taken over and above those observed in other similar workplaces. There are generally three sources from which radiation exposure may occur (i) radiation emitted from uranium ore in-situ and/or during handling (ii) airborne radiation resulting from the decay of radon gas released from the ore and uranium dust and (iii) contamination by ore dust or concentrate. Radiation levels around uranium mining and milling facilities are quite low - for the most part only a few times the natural background levels - and they decrease rapidly as the distance from... 

In most cases, we used the natural background radiation levels reported in the original property surveys. However, in several cases we modified the background value to reflect the influence of building materials when a mean background value could be calculated for parts of a structure that had no apparent relationship to contaminated materials and when such an adjustment was warranted by the nature of the building materials. 

For comparison, the health effects calculated from exposure to natural background radiation levels for typical residential properties were all about 0.01 per property, with radon daughters accounting for more than 50% of the total health effects estimated. 

Measurement of concentrations of naturally occurring radionuclides and natural background doses in the environment as a baseline for studies on radiation effects (Templeton et al. 1971)... 

The human body is equipped to deal with nominal levels of radiation doses. Background (natural) radiation from radon gas, cosmic sources, soil, and water produces an average dose of about 0.3 rem (0.003 Sv) per year.4 However, large doses of radiation generated after a terrorist attack can overwhelm the body s ability to repair damage, leading to stochastic or acute health effects. 

NCRP, Exposure of the Population in the United States and Canada from Natural Background Radiation, Report 94, National Council on Radiation Protection and Measurements, Bethesda, MD, 1987. 

If levels of radiation above natural background are discovered, a plant manager should consult a health physicist. At levels greater than 2 mrem/hour, aU industrial site activities should cease until the site has been assessed by an industrial health scientist or licenced environmental engineers. 

Recommended exposure limits are set by the US National Council on Radiation Protection (NCRP) and worldwide by the International Council on Radiation Protection (ICRP). The occupational exposure guidelines are 100 mSv in 5 years (average, 20 mSv per year) with a limit of 50 mSv in any single year. For the general public, the standard is 1 mSv per year. This must be put in the context of natural background radiation, which is approximately 3 mSv/year depending upon location (such as elevation) as well as other variables. 

Cothern CR, Lappenbusch WL, Michel J. 1986. Drinking water contribution to natural background radiation. Health Phys 50 33-47. 

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. 

Measurement of concentrations of naturally occurring radionuclides and natural background doses in the environment as a baseline for smdies on radiation effects (Templeton et al. 1971) Refinement of models of radionuclide transfer in food chains to aid in the assessment of radioactive releases from nuclear reactors and other point sources, including possible biomagnification by trophic components and turnover rates by receptor organisms (Kitchings et al. 1976)... 

Natural Background Radiation in the United States (1975) [Superseded by NCRP Report No. 94]... 

Life on earth has evolved in the presence of naturally occurring ionizing radiation, which is continuous and ubiquitous. In addition to natural background radiation exposure, mankind is now exposed also to radiation from various man-made sources. 

Tb a considerable extent, these risk estimates and risk comparisons are merely exposure comparisons. Their interpretation is aided by comparing them with natural background radiation exposure and its variations or comparison to the other risks of a particular activity or to the risks associated with safe industry . 

Lifetime (70 years) exposure to natural background radiation 1 mSvjri (100 mrem jr ) 1 X 10- ... 

Exempt Radioactive Wastes. The radioactive waste classification system in the United States does not include a general class of exempt waste (see Table 1.1). Rather, many products and materials that contain small amounts of radionuclides (e.g., specified consumer products, liquid scintillation counters containing 3H and 14C) have been exempted from requirements for use or disposal as radioactive material on a case-by-case basis. The various exemption levels are intended to correspond to low doses to the public, especially compared with dose limits in radiation protection standards for the public or doses due to natural background radiation. However, the exemption levels are not based on a particular dose, and potential doses to the public resulting from use or disposal of the exempt products and materials vary widely. 

The acceptable risks for substances that induce stochastic responses discussed in this Section are values in excess of unavoidable risks from exposure to the undisturbed background of naturally occurring agents that cause stochastic responses, such as many sources of natural background radiation and carcinogenic compounds produced by plants that are consumed by humans. This distinction is based on the assumption of a linear, nonthreshold dose-response relationship for substances that cause stochastic responses and the inability to control many sources of exposure. Risk management can address exposures to naturally occurring substances that induce stochastic responses, but only when exposures are enhanced by human activities or can be reduced by reasonable means. 

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