Information from plant operating experience available over the past years has shown that nuclear power plants discharge relatively small quan­tities of radioactive wastes to the environment. The Bureau of Radiologi­cal Health has compiled most of these discharge data obtained both by plant operators and by state health agencies. In developing plans for a co­ordinated national surveillance program, consideration should be given to the publication of this type of data in a uniform manner in a journal such as Radiological Health Data and Reports. The recent studies at operating facilities by the Bureau referred to earlier confirm that the discharge of ra­dioactive effluents into the air and water environment have not produced radiation levels at these facilities that would result in significant radiation doses to the population. The Bureau will, however, continue to assess these sources of environmental radiation to determine both short — and long-term levels and make estimates of their radiation effects on man.

From a public health standpoint, a major purpose of environmental surveillance programs, as noted earlier, is to obtain data that are useful for assessing the radiation exposure to man. The identification of the critical radionuclides and pathways for these nuclides to reach man generally re­quires that relatively few environmental media be analyzed in order to es­timate population exposure from the operation of a nuclear power plant. For this reason, the Bureau of Radiological Health is considering the fea­sibility of a graded environmental surveillance system which is based on a detailed knowledge of the effluent released. Studies have demonstrated that detailed analysis of the plant effluents can be quite meaningful, where­as it is difficult, if not impossible, to detect radioactivity in the environ­ment that has resulted solely from plant operation. Under such a concept, detailed and frequent field monitoring of radionuclides outside the plant boundary would be dependent on the level and kind of effluent released, except for continuous monitoring of the critical pathway for that particu­lar nuclear plant. The use of an integrating dosimeter to measure the ex­posure owing to the release of noble gases would be an example of the continuous monitoring required. In addition, a basic monitoring program such as that given on page 64, might be conducted on a periodic basis in order to keep the surveillance system operable.

Although the previous discussion has been concerned with surveil­lance requirements for the environment, it should be noted that the dis­charge of radioactivity to the environment from nuclear facilities is regu­lated by the aec so that the levels leaving the controlled area will not ex­ceed concentrations established in Title 10, Part 20 of the Code of Federal Regulations (10CFR20). In the case of liquid effluent, average concen­trations in the condenser water cooling canal must stay within these limits. The concentrations will be further diluted as the canal flows into the re­ceiving stream. For gaseous discharges, the discharge rate is normally con­trolled such that average concentrations in the atmosphere will not exceed 10CFR20 limits at the site boundary. Thus, increasing the flow rate of air discharged from the stack will lower the discharge concentration, but will not affect the total quantity of radioactive material discharged to the en­vironment or the resultant exposure of the population in the vicinity of the site.