Human Health Implications of Uranium Mining and Nuclear Power Generation
Uranium mining is the messiest and most contaminating stage of nuclear power generation. Yet, without it, the whole process cannot go ahead. The cost to the global environment, and to persons, of this stage must be factored into the cost of nuclear power generation.
Uranium mining, in particular open pit mining, which is what is currently proposed in several locations in southern Ontario, involves digging thousands of tons of radioactive rock out of a giant hole. (The Rossing uranium mine in Namibia is 1 km wide, 3 km long and 1/3 km deep (28)). Large quantities of this rock are dumped onto the earth’s surface.
The ore is then transported to a milling facility, usually nearby, and crushed to a 18 fine sand-like consistency, creating large amounts of radioactive dust and a huge volume of finely ground mill tailings. The uranium is separated out, usually with strong acids or alkalis. The sand-like tailings, containing about 85% of their original radioactivity, and often the chemicals used in the extraction process, are deposited in large tailings ponds or containments nearby. Dust containing uranium and its progeny is produced in large quantities by rock-crushing operations. This particulate matter, containing long-lived radioactive isotopes, can leave the site on wind.
Wind erosion of tailings piles can be significant as long as these remain exposed to weather. Radon gas is continuously produced by the decay of thorium 230, a radioactive decay product of uranium 238, through radium into radon. Thorium 230 has a half-life of 76,000 years, and will produce radon gas unabated for millennia. In undisturbed uranium deposits, most of the radon gas is trapped within rock formations until it decays into other radioactive byproducts. However, crushed tailings on or near the earth’s surface allow considerable radon to escape. In a 10 km/hr breeze, it can travel 960 km within 4 days; much further in higher winds. Radon gas decays sequentially into several other solid radioactive isotopes of polonium, bismuth and lead, before finally becoming the non-radioactive lead 206. These radioactive progeny of radon settle onto crops, bodies of water and soil. Their patterns of accumulation in the biosphere, including our food species, are not well known. The three isotopes of polonium produced by radon, in addition to being radioactive, are among the most toxic naturally occurring substances on earth. The toxicity of lead is well documented.
Radon is a major contributor to the excess of lung cancer seen in uranium miners (4, 5, 6). Radon at levels seen in some residences also carries a risk (29). Radon emanations from bedrock in certain areas may be unavoidable, however these can be greatly increased in the presence or proximity of crushed mine tailings or abandoned mine workings which provide pathways of migration to the surface. Some high residential radon readings are being found by homeowners near old mine sites in the Bancroft/Haliburton area (30).
Groundwater and surface water in the vicinity of uranium mining operations frequently become contaminated (31). At the advanced exploration stage of mine development, holes about 1-2" in diameter and up to 1200 feet deep are drilled into rock, usually into the most concentrated deposits. A hole of this depth is almost certain to penetrate 19 aquifers, giving water access to radioactive rock surfaces.
Many uranium compounds and decay products are soluble, toxic and radioactive. In an area of fractured granite bedrock, as found in some uranium bearing areas of Ontario, many of the aquifers interconnect and contamination quickly becomes widespread.
Uranium in drinking water, at levels in excess of the safe drinking water standard of .02 mg/L or 20 ppb, is principally toxic to the kidney, in particular the proximal tubules (32). Uranium can also affect fertility, fetal growth and postnatal viability (33). It may cause malformations in fetuses and might be associated with reproductive cancers. It concentrates in bone and may interfere with the activity of osteoblasts, possibly contributing to bone cancers and osteoporosis (
Tailings impoundments containing liquid material can leach contaminants into the soil and groundwater. Tailings dams can fail, releasing massive quantities of radioactive material into local waterways (35). Near the decommissioned mines at Elliot Lake, tailings piles were covered with water to prevent the escape of radon gas, a standard procedure.
Recent drought has caused serious difficulties with this maintenance protocol. A mere 15 years into the thousand-year period for which it was designed, this environmental safeguard system is underperforming (36). Over 100 million tons of uranium tailings are stored in the Elliot Lake area (37). Dry piles of uranium mill tailings are subject to erosion by wind and water.
In Ontario, near Bancroft and Haliburton, there are about 5 million tons of uranium mine tailings. Many of these were abandoned by mines which closed before 1977, and as such they are under the jurisdiction of neither the federal nor the provincial governments (40).
As a result, according to a study by the Canadian Institute for Radiation Safety (CAIRS) (40), many of the tailings "have not undergone any remedial work designed to place them in a safe condition." Tons of radioactive rock are laying around unprotected, with contaminants leaching out, wind blowing dust, radon gas escaping, fencing and signage falling into disrepair and the area being used more and more for hunting, hiking and recreation.
What are the risks from these tailings?
According to the CAIRS study, a person walking over a typical tailings pile for 1 hr every day will absorb a gamma radiation dose of, on average, 0.73 mSv/yr (41). This would be in addition to the ~1.0 mSv/yr of background gamma radiation we all receive. Consider that doubling a person’s exposure will in general double his/her cancer risk, and that this person will also be exposed to higher than normal levels of radon gas near the tailings. If a house were built on the tailings, or if substantial amounts of radioactive fill were used near this house, or to mix concrete for the house, and a person or family spent between 8 and 24 hrs/day in this house, their radiation exposure could be substantial.
URANIUM REFINING AND ENRICHING
After the uranium is mined and milled, it is refined. Canadian uranium from all sources is sent for further processing to a refinery in Blind River, Ontario or to a conversion facility in Port Hope, Ontario.
The UF6 is then sent to an enrichment plant in Kentucky where the isotopes U 238 and U 235 are separated from each other and remixed in more desirable proportions. Uranium with an excess of the fissionable U 235 is "enriched"- this leaves a stockpile of extra U 238 or "depleted" uranium.
Uranium ore, yellowcake (the milled uranium destined for Port Hope or Blind River for refining), and uranium fuel rods for use in reactors are all transported by rail or truck to their destinations. This carries with it the risk of an accident or major spill, with further risk of air, water and soil contamination.
Canadian CANDU reactors use unenriched uranium. Until 1965, all Canadian uranium was used exclusively for American nuclear weapons, including the Hiroshima and Nagasaki atomic bombs. After this, the Canadian government decided that Canadian uranium was only to be used for civilian purposes, such as electricity generation (25).
To read the whole report click or paste the link below:
http://www.safewater.org/PDFS/reportlibrary/HumanHealthImplicationsUraniumNuclear.pdf
