Occupational radiation exposure in nuclear fuel cycle facilities

Full text: This symposium forms an essential part of the continuing tradition of subjecting nuclear energy to periodic review to assess the adequacy of radiation protection practices and experiences and to identify those areas needing further study and development. Specifically, the symposium focused on a review of statistical data on radiation exposure experience to workers in the nuclear fuel cycle through 1978. The technical sessions were concerned with occupational exposures: experienced in Member States; in research and development facilities; in nuclear power plants; in nuclear Fuel reprocessing facilities; in waste management facilities; and techniques to minimize doses. A critical review was made of internal and external exposures to the following occupational groups: uranium miners; mill workers; fuel fabricators; research personnel, reactor workers; maintenance staff; hot cell workers; reprocessing plant personnel; waste management personnel. In particular, attention was devoted to the work activities causing the highest radiation exposures and successful techniques which have been used to minimize individual and collective doses. Also there was an exchange of information on the trends of occupational exposure over the lifespan of individual nuclear power plants and other facilities in the nuclear fuel cycle. During the last session there was a detailed panel discussion on the conclusions and future needs highlighted during the symposium. While past symposia on nuclear power and its fuel cycle have presented data on occupational dose statistics, this symposium was the first to focus attention on the experience and trends of occupational exposure in recent years. The papers presented an authoritative account of the status of the levels and trends of the average annual individual dose as well as the annual collective dose for occupational workers in most of the world up to 1979. From the data presented it became evident that considerable progress has been made over the past several years in reducing occupational exposures throughout the nuclear power industry. It was consistently reported that current annual occupational exposures are averaging approximately 10% of the limits recommended by the International Commission on Radiological Protection (ICRP). Countries throughout the world recognize the ICRP guidance on radiation protection. It was also expressed at the meeting that the highest exposures come from external sources. As for internal sources, about 99% of the workers receive less than 1% of the recommended limits with the exception of some underground uranium miners. Discussions during the symposium reaffirmed the adequacy of many of the current radiation protection practices. The radiation exposures of utility personnel were described for nuclear power plants in Canada, Federal Republic of Germany, German Democratic Republic, Sweden, the UK and the United States. The Swedish boiling-water reactor (BWR) plants have attained radiation exposures which are significantly less than those for BWR plants in the United States. Similarly, plants in Canada and the UK expose their personnel to much less radiation, however the Canadian and British plants are designed and operated very differently from US nuclear power plants, making direct comparisons inappropriate. Efforts to reduce nuclear power plant radiation fields have been particularly successful at one of the Canadian pressure-tube heavy-water reactors. Decontamination and careful control of coolant chemistry were identified as the most significant influences. Steam generator modifications were performed recently in the USA and significantly reduced radiation exposure, compared to a similar previous modification, was obtained by incorporating the experience from the first modification into the design, planning and training for the more recent modifications. Research is underway in the USA on techniques to reduce radiation exposure, with particular emphasis on: (1) determination of the trends in plant radiation fields, (2) control of the sources of radiation, e.g. through quality control of materials used in construction, (3) testing coolant purification techniques, (4) investigating the influence of coolant chemistry control, and (5) developing techniques for decontamination. The previously mentioned Canadian and Swedish experiences together with some significant Japanese results are being incorporated in these US research efforts. Radiation exposure experiences were described for fuel reprocessing plants in Belgium, Federal Republic of Germany, France and the United States using both direct and indirect maintenance. Exposures were similar to those received by nuclear power plant operators, maintenance and health physics personnel, all were well within international guidelines. The major part of the discussion centered around the following topics: the difficulties of applying cost/benefit analysis; the need for uniform reporting of exposure data; the necessity of preparing and designing for high-exposure maintenance activities; the desire for epidemiological studies on radiation workers which will include exposure; to other carcinogenic agents, smoking habits and medical and natural exposures; the reasons behind reported dose reductions. A great deal of practical experience is now available on minimizing industrial and collective doses to radiation workers, as well as on advanced techniques to control occupational exposure at nuclear fuel cycle facilities. (author)