Nuclear-Fueled Power Plants - Energy and the Environment - page 126

radiation over time is called a radiation dosage.
For example, the average person in the United States receives in one year a dosage of about 360
millirems (3.6 mSv), of which 200 is from radon-86, 27 from cosmic rays, 28 from rocks and soil,
40 from radioactive isotopes in the body, 39 from X rays, 14 from nuclear medicine, and 10 from
consumer products and other minor sources.
The average person on earth receives about 2.2 mSv y − 1 . A short-term dose of 1 Sv causes
temporary radiation sickness; 10 Sv is fatal. After the Chernobyl accident in the former Soviet
Union, the average dose received by people living in the affected areas surrounding the plant over a
10-year period, 1986-1995, was 6-60 mSv. The 28 radiation fatalities at Chernobyl appear to have
received more than 5 Sv in a few days; those suffering acute radiation sickness averaged 3-4 Sv.

An accumulation of absorbed α , β , and γ

6.3.2.1 Biological Effects of Radiation
The greatest risk to humans of nuclear power plant operations is associated with radioactivity, also
called ionizing radiation, because of the creation of ions left by the passage of rays and

neutrons. Radioactivity affects humans and animals, causing somatic and genetic effects. 13 Somatic
effects can be acute when an organism is subjected to large doses of radiation, or chronic when the
exposure is at low levels, but over protracted periods. Acute effects include vomiting, hemorrhage,
increased susceptibility to infection, burns, hair loss, blood changes, and, ultimately, death. Chronic
effects, which usually manifest themselves over many years, include eye cataracts and the induction
of various types of cancer, such as leukemia, thyroid cancer, skin cancer, and breast cancer. Genetic
effects may become apparent in later generations but not in the exposed person. These effects are
due to mutations in the genetic material—for example, chromosome abnormalities or changes in
the individual's genes that make up the chromosomes.

α , β , and γ

6.3.2.2 Radiation Protection Standards
The prescription of radiation protection standards is an onerous and controversial task. In the
United States, this task was vested in the Committee on the Biological Effects of Ionizing Radiation
(BEIR) of the National Academy of Sciences, and internationally it was vested in the United Nations
Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The task is difficult because
direct evidence on biological effects of radiation comes (unfortunately) from high-level exposures,
such as received by the population of Hiroshima and Nagasaki during atomic bombing and by
the workers at the Chernobyl and Tokaimura accidents. Lower-level exposure data can only be
obtained from animal studies, then extrapolated to humans. However, even in animals, the effects
of low-level exposure can only be established statistically, observing a large cohort of animals over
lengthy periods and over many generations.
In setting radiation standards, the following three assumptions are made:

(a) There is no threshold dose below which radiation has no effect.
(b) The incidence of any delayed somatic effect is directly proportional to the total dose
received.
(c) There is no dose-rate effect.

13 Somatic effects pertain to all cells in the body; genetic effects pertain to egg and sperm cells.