Safety

Of major concern regarding nuclear reactors is the possibility of an accident exposing the public to harmful levels of radiation.

In addressing this concern it should first be mentioned that radiation is released naturally from the environment constantly (referred to as “background radiation”) and we, as humans, are quite able to handle low doses of it. In fact, of the total amount of radiation that the average person is exposed to, 90% comes from nature, 10% from medical sources and a negligible amount is from nuclear power. In 12,000 cumulative reactor-years of operation there have only been two major accidents – Three Mile Island and Chernobyl, and of these two, only Chernobyl resulted in the public being exposed to radiation doses higher than those that result from nature.

The Chernobyl reactor was an antiquated design. Over the past couple of decades reactor designs have become safer and more efficient. Today’s reactors consist of a series of physical barriers whose purpose is to contain radioactive material. Firstly, the fuel itself consists of solid ceramic uranium pellets where most of the radioactive by-products are contained. The pellets are sealed in zirconium alloy rods. The reactor vessel has steel walls that are 8 inches thick, and is surrounded by a three foot thick concrete container. And lastly, the containment building in most cases is lined with steel and has concrete walls that are four feet thick.

Even with all of these physical containment barriers, decades-long testing and analysis has showed that less radioactivity escapes from fuel than initially believed and that radioactive material is not very readily mobilized beyond the immediate internal structure. Therefore, even if there was a rupture of the containment building, it would still be highly effective in preventing the release of radioactive material.

It should also be noted that a commercial reactor cannot, under any circumstances, explode like a nuclear bomb.

Nuclear Waste Disposal

The disposal of nuclear waste is also of public concern. To begin with, the amount of waste produced from nuclear generated electricity is very small relative to the wastes produced by fossil fuel burning. And in contrast to the latter, the waste from a nuclear reactor can be harnessed and contained where it can’t be of harm to the public or the environment.

The first advancement in the area of spent fuel disposal is the reprocessing of spent reactor fuel. Used fuel contains some of the original active uranium as well as various plutonium isotopes that can be separated for re-use in nuclear reactors.

Radioactivity of all nuclear waste decays over time, the key is protecting people and the environment from the radioactivity while the decay takes place. This involves isolating or diluting the waste so that the rate or concentration of radionuclides (radioactive isotopes of the uranium) returned to the environment is harmless.

For the first 40 – 50 years, spent reactor fuel is stored at the reactor site, within the containment building, to allow heat and radioactivity to decay to levels which make handling and storage easier. Currently, the majority of the world’s nuclear waste is still at reactor sites. The plan for long term storage is ‘multiple-barrier’ geological disposal. First, the waste will be immobilized in an insoluble matrix, and then sealed inside a corrosion-resistant container. The containers will then be buried deep underground in a stable rock structure. Several countries including Finland, Sweden, and the U.S. already have planned sites for this deep geological storage. This will ensure that no significant environmental release occurs over the tens of thousands of years it takes for decay to occur.