Positive Energy

Monday, May 24, 2004

Are We Safe Yet?

There is no question about the safety of CANDU reactors in operation. And we know how to store the nuclear fuel that has been used once. So the nuclear energy cycle is exceptionally clean and safe from the operational stage on. But what about the earlier stages of this process, the mining and refining steps? There are lots of handling, moving, processing, and storing tasks involved. How safe are these activities?

The first fact needed to understand this situation is that uranium itself is not dangerous. The mining and refining process extracts it as uranium oxide, a yellow powder. It is stored in 200 litre drums. If you stand beside one of these drums the radiation rate is about half that received from cosmic rays when you fly in a commercial airplane. So once we get away from the mine with the product things are OK. Some basic precautions are reasonable when handling this material, but the issues are manageable.

This leaves the mine itself as a point of concern. Some Canadian mines have exceptionally high grade ore. It contains a lot of uranium, and a lot of other elements that are dangerous such as radium and radon. In these mines robotic equipment is used to minimize the exposure of humans. Canada has not had any cases of radiation illness among its miners, so in this sense we seem to be doing a good job.

However, there are concerns about mine tailings, the stuff left behind after the uranium has been extracted. This waste material contains everything that is not uranium in the ore. When it was in the ground the uranium was decaying, as uranium does, leisurely breaking down into radium, radon, lead, and other elements. These byproducts could not go anywhere, and the ore has been there for a long time, so there is quite a build up associated with the uranium. These byproducts are dangerously radioactive. This is the stuff left behind when the uranium is extracted. It makes the tailings measurably radioactive. So the tailings from uranium mines need to be handled with care.

Uranium mines in Canada must be returned to a natural state when the ore is exhausted. In this natural state the radioactivity at the mine site must be the same as the general background radioactivity in that area. This is feasible, but takes some careful work to do it right. For this reason every mine has a bond posted that will provide enough money to do the clean up chores after the mine shuts down. Canadian mines are well regulated in this sense - provisions have been made up front for site restoration.

The tailings have to be stored while the mine is in use. We don't want people camping on them, and we don't want water washing through and spreading the solid material into unprotected areas. The tailing dumps are usually a controlled low area, sometimes a valley with a human-built dam at one end. Water is not allowed to run off. The water can evaporate, since this leaves the heavy products behind. When the mine stops operating the tailings can be put back into the mine itself, or covered where they sit with enough clay and rock to lower the radiation level to the background level. These closed sites then need annual monitoring to ensure that leaks have not begun.

Note that the overall radioactivity in an area is not increased by mining. The radioactive elements left in the tailings are just those that were there originally. If they are covered or put back into the mine there is no net change in the area.

My impression is that the nuclear power cycle can be run in a clean and safe manner. Instead of hundreds of mines extracting coal we have six mines extracting uranium. Just by being a lot smaller it is a lot safer. Instead of flooding thousands and thousands of hectares to dam rivers to a height sufficient for hydrodynamic electricity, we have a few tailing areas to manage. This is a much less destructive and safer process. Instead of floating thousands of tankers on the ocean with a certain percentage of them rupturing every year, we have a few trucks hauling a harmless yellow powder around. In total, the safety advantages of the nuclear energy cycle are compelling.



Uranium Mining Wastes

Include Radionuclides in CEPA list


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