Inhaled In body Total to be much higher, averaging 40 to 80 Bq/m3 (1 to 2 pCi/L). This is because the decay of each gram of radium naturally present in the ground produces about 0.10 mL of radon gas per day. As an ideal gas, radon moves readily through the soil, entering buildings through the foundation. About 1.18% of potassium consists of the radioactive isotope 40K. The 40K in our bodies contributes about 0.17 mSv/yr. Cosmic rays produce an exposure of 35 mR/yr at sea level, and 100 mR/yr at an altitude of 10,000 ft. Exposure to granitic bedrock produces about 90 mR/yr from natural isotopes, and sedimentary rock produces 23 mR/yr.
Nuclear power results in emissions at a number of points in the fuel cycle, such as mining, fuel processing, and power generation. A wide variety of radionuclides are produced in the power reactor. Besides the direct reaction products, neutrons striking other materials, such as air and impurities in cooling water, produce new radionuclides by neutron activation. This creates radioactive forms of carbon, nitrogen, argon, oxygen, copper, sodium, and many others. Some of these products are released to the environment. Atmospheric nuclear weapons testing up to 1973 released far larger quantities of radio-nuclides to the environment than nuclear power has.
The primary risk of concern with radiation exposure is cancer and hereditable genetic disorders. The International Commission on Radiation Protection (ICRP, 1990) estimates the probability of fatal cancer of all types for the general population to be 5% per sievert dosage and the probability of severe hereditary disorders to be 1% per sievert. Table 21.16 details these risks for individual tissues. Also given is the aggregated detriment, which
TABLE 21.16 Estimated Radiation Risk Probabilities for Specific Tissues and Organs
Probability of Aggregated
Fatal Cancer Detriment
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