4.1 Radiation risks of nuclear waste

4 RISKS FOR THE ENVIRONMENT AND HUMAN HEALTH

Radioactive waste poses risks to the environment and human health. “Risk” is defined here as a function of both hazard and exposure: the most likely consequence of a hazard, combined with the probability of exposure to it. This chapter will focus on higher activity nuclear wastes (see chapter on classifications) and highlight potential unresolved dangers and problems. Although nuclear waste poses both radiological and chemical risks, it will concentrate on the former, as these are generally more serious.

Although risks arise from every step in the lengthy nuclear fuel chain, this chapter will focus on the hazards and risks of nuclear waste arising from the following:

• uranium mining, milling, enrichment, and fuel fabrication

• operation of nuclear power plants

• spent nuclear fuel

• reprocessing of spent nuclear fuel, and

• reactor decommissioning.

4.1 RADIATION RISKS OF NUCLEAR WASTE

Nuclear waste can give off several types of radiation: alpha particles, beta particles, and gamma rays. While alpha particles are most easily stopped, even by thin barriers such as paper, their effects are particularly damaging. They are very detrimental when inhaled or ingested and have a radiation weighting factor 20 times greater than gamma rays per unit of exposure. Beta particles are more penetrating than alpha particles, but can still be attenuated by denser materials such as plastic and aluminum. Gamma rays are highly penetrating; dense materials such as lead and thick concrete are required to attenuate them.

Radiation from radioactive waste is carcinogenic, mutagenic, and teratogenic (a teratogenic substance is one that can damage a fetus or embryo). Radiogenic65 cancer risks depend on the type of cancer, the tissues exposed, the dose, dose rate, and type of radiation. The final risk to individuals will also depend on their gender, age, and the time that has passed since exposure. Radiation is also increasingly implicated in a wide range of other diseases including cardiovascular diseases, strokes, eye cataracts, and mental effects.

According to the International Commission on Radiological Protection (ICRP), an external whole-body radiation dose of one sievert (Sv) results in an approximately ten percent risk of fatal cancer in adults. However, the ICRP later reduced its estimate by half to five percent through its use of a dose and doserate effectiveness factor (DDREF) of two for solid cancers.66 DDREFs were formerly used to reduce risks derived from the Japanese bomb survivors’ exposures to low dose and low dose-rate radiation. Older cell and animal studies had indicated these exposures were less harmful than those to higher doses

65 Radiogenic means produced by or determined from radioactivity. 66 International Commission on Radiological Protection 2007, “The 2007 Recommendations of the International Commission on Radiological Protection”, ICRP publication 103.37