As in the case of liquid wastes, gaseous discharges from operating nuclear power plants have generally been small fractions of the licensed limits permitted by the aec. The principal radionuclides normally dis­charged that are of public health concern are the radioactive noble gases. Because of the differences in gaseous waste handling design between boil­ing water (bwr) and pressurized water (pwr) reactors, there are varia­tions in the radionuclides contained in the effluents from the two kinds of plants. A bwr discharges gaseous wastes continuously following a delay of approximately 30 minutes. Consequently, although higher total quanti­ties of gaseous effluents are discharged, they have relatively short half­lives (from seconds to a few minutes) and are, therefore, of reduced pub — * Monthly publication of the Bureau of Radiological Health, Environmental Con­trol Administration, Consumer Protection and Environmental Health Service, Pub­lic Health Service, U. S. Department of Health, Education, and Welfare.

lie health significance. The radionuclides normally contained in a bwr gaseous effluent would include isotopes of krypton and xenon with 88Kr, 135Xe, 138Xe, and 87Kr predominating. A pwr, with its much longer stor­age time which allows for radioactive decay would discharge predomi­nately 85Kr with some 133Xe, although in very small total quantities. Off­site dose contributions from gaseous discharges have been undetectable in the case of an operating pwr and only marginally above background for an operating bwr for those facilities studied by the Bureau.

Radioactive iodine is also a nuclide of public health concern because of the air-pasture-cow-milk chain which could permit concentration in a child’s thyroid. Although it is of concern, our own studies and a thorough review of surveillance data have not indicated iodine 131 to be of public health significance as a contaminant from normally operating nuclear power reactors. Iodine 131 was barely detectable in the gaseous effluent of the bwr studied, and extensive efforts to detect this nuclide in environ­mental milk samples faffed even with ultrasensitive analytical techniques. pwr waste treatment systems normally eliminate iodine 131 through stor­age and decay because of its short radioactive half-life (8 days). During our field study of an operating pwr, sampling in the environs faffed to de­tect iodine (Radiological Engineering Laboratory, Division of Environ­mental Radiation, 1970).