One of the most important field studies has been conducted at the Dresden Nuclear Power Station in Illinois by the Bureau’s Radiological Engineering Laboratory, Cincinnati, Ohio, in cooperation with the Com­monwealth Edison Company, the Illinois State Health Department, and the AEC.

This site was selected because of the extensive operating experience with Dresden 1 and the development of other nuclear facilities on the same site. Dresden 1 has been in operation since 1962, and at the time of the study’s inception was the largest (200 megawatts electrical) operating boiling water reactor. The specific objectives of the study were to: (a) de­velop better data on which to base guidance for environmental surveil­lance programs; (b) obtain a more comprehensive knowledge of the prob­lems associated with effluent monitoring from nuclear facilities; (c) in­crease the depth of technical knowledge within the Bureau of Radiologi­cal Health in order to better assist states in developing surveillance pro­grams; and (d) evaluate the movement of radionuclides from nuclear fa­cilities into and through the environment.

Emphasis was placed on identifying critical pathways of radioactivi­ty from source to man including delineating any reconcentration media or indicator radionuclides within the pathways, and correlating stack dis­charges with the associated environmental levels produced. Since the site will soon contain other reactors and a fuel reprocessing plant, the effect of multiple sources may be investigated at a later date.

Various samples were collected at the Dresden Station for radio­nuclide analysis in three general areas: gas and particulates in the reactor discharge lines, liquid wastes, at various points within the plant, and sam­ples taken in the environment. This sampling procedure made it possible to determine the significant nuclides in the plant before release and to cor­relate these known quantities discharged with any radionuclides detected in the environment. Critical radionuclides and their pathways through the environment that could cause significant exposure to man were identified. Techniques employed to measure radionuclides during the study were of a type more sensitive than those normally used in routine environmental surveillance programs. This enabled a detailed quantitative evaluation of specific radionuclides to ensure that all possible “critical” radionuclides were identified.

The final report for this field study has been published (Radiological Engineering Laboratory, Division of Environmental Radiation, 1969), and some results can be summarized as follows: First, the critical pathway for possible exposure of the population from this reactor was determined to be via the atmosphere through the discharge of noble gases. Based on survey instrument and dosimeter measurements around the site, the aver­age exposure at the sampling locations during the study was estimated to be less than 5 mrem per year. A more precise estimate was difficult be­cause gaseous releases from Dresden have resulted in environmental ra­diation levels which were only marginally above background.

Second, both in-plant and environmental samples were collected over a period of several months for analysis. The types of samples col­lected were: in-plant — primary coolant, recycled demineralized water, fuel pool water, waste neutralizer tank, laundry wastes, delay line, con­tainment building ventilation filters, and turbine building ventilation fil­ters; plant discharges — water from discharge canal, and gas, particulate filters, and charcoal iodine filters from the stack; environs — plume, milk, cattle thyroids, rabbits, com kernels and husks, leafy vegetables, grass, soil, drinking water, rainwater, snow, river water, silt, and fish. The inter­pretation of data obtained from the analysis of the environmental samples indicates no detectable radioactivity resulting from the operation of the plant which could be considered a source of population exposure. These results are shown in the accompanying tabulation: levels of radioactivity in positive samples are given; negative samples included soil, leafy vege­tables, fish, grass, milk, rabbits, drinking water, river water, and rainwater.

In order to provide data on a pressurized water reactor to augment the field data obtained at Dresden 1, a study was initiated at the Yankee Atomic Power Station in Rowe, Massachusetts. Since the fieldwork was only recently completed, results of this study are not yet available; how­ever, these will be published as soon as all of the data have been evaluated

(Radiological Engineering Laboratory, Division of Environmental Ra­diation, 1970).

A similar study is currently under way at the Nuclear Fuel Services, Inc., spent-fuel processing plant in New York State. The routine dis­charges from a fuel reprocessing plant are somewhat different from a nu­clear power plant in both magnitude and in character. The results of this field study are expected to contribute significantly to our ability to monitor this type of facility adequately.