All of us receive a small amount of radiation all the time from natural sources such as cosmic radiation, rocks, soil and air. Uranium mining does not increase this discernably for members of the public, for aboriginal people living near the mines, or for others outside the industry.
A dose is the amount of medically significant radiation a person receives.
In Australia, mining operations are undertaken under the country's Code of Practice on Radiation Protection in the Mining and Milling of Radioactive Ores, administered by state governments (and applying also to mineral sands operations). In Canada, the Canadian Nuclear Safety Commission regulations apply. In other countries there are similar arrangements to set health standards for gamma radiation and radon gas exposure, as well as for ingestion and inhalation of radioactive materials. Standards apply to both workers' and public health.
The basis of radiation protection standards
In practice, radiation protection is based on the understanding that small increases over natural levels of exposure are not likely to be harmful but should be kept to a minimum. To put this into practice the International Commission for Radiological Protection (ICRP) has established recommended standards of protection (both for members of the public and radiation workers) based on three basic principles:
These principles apply to the potential for accidental exposures as well as predictable normal exposures.
Underlying these is the application of the "linear hypothesis" based on the idea that any level of radiation dose, no matter how low, involves the possibility of risk to human health. This assumption enables "risk factors" derived from studies of high radiation dose to populations (eg from Japanese bomb survivors) to be used in determining the risk to an individual from low doses (ICRP Publication 60). However the weight of scientific evidence does not indicate any cancer risk or immediate effects at doses below ablout 50 millisievert (mSv) per year.
Based on these conservative principles, ICRP recommends that the additional dose above natural background and excluding medical exposure should be limited to prescribed levels. These are: one millisievert per year for members of the public, and 20 mSv per year averaged over 5 years for radiation workers who are required to work under closely-monitored conditions.
The frameworks of radiation safety in countries where most uranium is mined are based on the full adoption of international recommendations. This is not the case in all parts of the world. Even the 1977 Recommendation of the ICRP has not been universally adopted.
The safety record of the uranium mining industry is good. Radiation dose records compiled by mining companies under the scrutiny of regulatory authorities have shown consistently that mining company employees are not exposed to radiation doses in excess of the limits. The maximum dose received is about half of the 20 mSv/yr limit and the average is about one tenth of it. (This compares with natural doses of up to 50 mSv/yr for some places in India and Europe, without any adverse effects being evident, and mean exposures of 750 mSv/yr in some East German mines from 1946 to 1954, resulting in thousands of cases of lung cancer.)
Furthermore, doses are reduced by programs of education and training, as well as engineering design.
Achieving effective radiation safety
A number of precautions are taken at a uranium mine to protect the health of workers:
See also Radiation Safety inUranium Mining & Milling, Supervising Scientist Group.
Radiation safety regulation in Australia
When the current era of uranium mining began in Australia in the 1970s, a review of the regulatory framework for radiation safety was undertaken. This resulted in the production of the 1975 Commonwealth Code of Practice on Radiation Protection in the Mining and Milling of Radioactive Ores (the 'Health Code'). The Health Code was formulated from recommendations made by the International Commission on Radiological Protection (ICRP) and the radiation dose limits adopted by the National Health and Medical Research Council (NH&MRC).
This Health Code has legal force in the States and Territories only when it is adopted under State and Territory Acts or Regulations.
In the Northern Territory (where the Ranger uranium mine is located), the Health Code was adopted as a Condition of Licence under the Mining Act Regulations, thus giving it legal status.
In South Australia the Health Code is given legal status through the Act setting up the Olympic Dam mine.
Responsibilities for administration of the Health Code are divided between the Health Department and the Mines Department or their equivalent bodies in the States and Territories. The Health Department is responsible for ensuring that the basic radiation exposure standards are complied with, while the Mines Department is responsible for the day-to-day overseeing of the general occupational health and safety requirements at mine sites.
The Health Code was revised in 1980 and again in 1987.
In addition to the Health Code there is the Code of Practice on the Management of Radioactive Wastes from the Mining and Milling of Radioactive Ores (1982) - the 'Waste Code', and the Code of Practice for the Safe Transport of Radioactive Substances (1990). These Codes are given legal force in the States and Territories in much the same way as the Health Code, i.e. they are imposed as Conditions of Licence under State and Territory Acts.
Radiation protection standards
Following the ICRP-60 recommendations published in 1991, the NH&MRC and the National Health & Safety Commission jointly prepared new Australian Recommendations for limiting exposure to ionising radiation and a National Standard for limiting occupational exposure. These are consistent with the Basic Safety Standards for radiation protection adopted in 1994 by various UN agencies.
The revised occupational exposure limit is 20 millisieverts per year averaged over five consecutive years. (Exposure limits for members of the public from radiation-related activities remained at 1 mSv per year, which is less than the average radiation background from the environment.)
In 1999-2003 the Health Code was combined with the Waste Code in a wide-ranging revision which incorporated the NHMRC recommendations.
Since the early 1990s, all mining companies have voluntarily agreed to adopt the ICRP-60 Recommendations, without waiting for the complete revision of the Health Code.
NHMRC 1995, Reccommendations for limiting exposure to ionizing radiation and National standard for limiting occupational exposure to ionizing radiation.
NRPB Bulletin # 175.
GPO Box 1649N, Melbourne 3001, Australia
phone (03) 9629 7744
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Email : uic@mpx,com.au