After several hundred years of relatively rapid decline (as illustrated in Figure 9–4), the radioactivity is within a factor of 10 of that in the original ore, and from that point forward, the radioactivity is dominated by the slowly decaying actinides. The shielding requirements for this latter phase are much less demanding than the initial requirements.

The technical problems of waste disposal are not considered major. (These are discussed in detail in chapter 5.) Among the schemes that have been proposed, deep-mined repositories in geologically sound locations seem to offer storage at reasonable cost and acceptable risk.*

The government urgently needs to initiate a program of radioactive waste management, including that of mines and mills. While improved schemes may be developed in the future, waiting for their emergence and demonstration does not seem sensible in view of the practical measures that can be taken now. Rather than searching for a once-and-for-all solution, research should be undertaken to assure that each increment of waste is disposed of by the best technology available. The committee’s recommendations on the management of radioactive waste can be found in chapter 5.

Combustion

To control pollution of the atmosphere from combustion, the Environmental Protection Agency establishes and enforces two sets of standards: one set that limits emissions and another that stipulates the ambient air quality to be maintained (or bettered, if possible). Standards for emissions from power plants are detailed in chapter 4. In this chapter, five principal pollutants are considered. For each, one or more national ambient air quality standards have been set that may not be exceeded anywhere. These standards are defined as the amount of pollutant in a cubic meter of air, or as an allowable fraction of the total atmosphere.

There are similarities and differences in the nature of the standards applied to chemical and radioactive pollutants. The emission standards for combustion devices (chapter 4) are analogous to those for radionuclides emitted from reactors. On the other hand, the ambient air quality standards for chemicals relate to possible exposure, whereas the standards for radiation are stated in terms of the absorbed dose in the tissue of interest. In this respect, the practice of radiation protection is more sophisticated. The difference is not academic, since the major difficulty in estimating the hazards of the chemical pollutants stems from lack of knowledge of the dosage.

*

Statement 9–5, by J.P.Holdren: The decision on acceptability is not this committee’s to make.



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