Sources of radiation – over 80% from natural environment
We are exposed to radiation in our everyday life. In fact, over 80% of radiation comes from natural sources such as sunlight, soil, rocks, water, plants, animals and our own bodies. Man-made sources account for ~18% (eg. computers, cell phones, TVs, X-rays – medical procedures make up the majority of man-made radiation exposure). Less than 1% is due to the nuclear industry (including uranium exploration and mining).
A person’s exposure to radiation is measured in units called millirem (mrem). A millirem is a scale of radiation exposure similar to the degree scale used to measure temperature. The amount of radiation to which an average person is exposed per year from all sources is about 360 mrem. However, it is not uncommon to receive much higher doses due to activities such as medical procedures and air travel. The international standard limit is 5,000 mrem/year for persons working with and around radioactive material.
A nuclear plant worker receives less radiation (~300 mrem/year) than a person who makes one transcontinental round trip flight across Canada (~500 mrem). A resident outside a nuclear plant is exposed to about two mrem/year while a person standing 100 feet from a moving vehicle transporting spent nuclear fuel would receive 0.0004 mrem. Burning coal emits more radiation than nuclear power generation – and the radiation from coal is vented directly into the atmosphere. A person living next to a coal plant for one year receives approximately 20 mrem/year – 10 times higher than someone living next to a nuclear plant.
Uranium exploration and mining – radiation exposure limits
Radiation has been extensively studied, is easily measured and can be safely controlled. International radiation safety regulations have been applied at uranium mines in the Western world for more than 40 years.
The Canadian Nuclear Safety Commission’s workplace limit for exposure of an individual is 5,000 mrem/year in any location including flight crews and personnel in nuclear power plants and uranium mines. The average yearly exposure of personnel in the nuclear industry is 300 mrem. The general public limit is recommended to be 100 mrem/year, which is the same recommended exposure limit for uranium exploration.
In exploration, potential radiation exposure comes primarily from uranium in the soil, outcrops of rock, rock specimens, during drilling and splitting of drill core for sampling, as well as in the core storage sheds. Based on Canadian guidelines, exposure rates to core or outcrop with <1,000 counts per second (cps) at 1 metre is considered safe.
Action Level for Radiation Protection Controls:
>1,000 cps at 1 metre from source
1,000 cps at 1 metre = ~0.1 mrem = ~0.1% U3O8
(for a large outcrop or core shed)
For safety purposes, high grade uranium ore is considered at >0.3% U3O8. The average grade of U3O8 Corp’s uranium resource in Guyana is 0.1% U3O8 (~1,000 cps). Exploration work in an outdoor environment is in the same range as radiation exposure from natural sources. While exposure in U3O8 Corp’s exploration area is generally low at <1,000 cps, we have implemented precautionary measures in our exploration work including the use of protective gear, worker radiation monitoring devices, contamination controls and monitoring practices.
In the case of uranium mining, radiation exposure is minimal in an open pit uranium mine, because there is sufficient natural ventilation (eg. at Australia’s Ranger mine, levels seldom exceed 1% of allowable levels). An underground mine requires good forced-ventilation system (eg. Australia’s Olympic Dam averages <100 mrem/year. Canadian doses (in mines with high grade ore) average about 300 mrem/year).
Sources: World Nuclear Association, National Council on Radiation Protection and Measurements, Canadian Nuclear Safety Commission, 2008 Secondary Energy Handbook, U.S. Department of Energy, Alberta Department of Energy