Radiological protection report 2017

In this report on radioprotection 2017, the Swiss Federal Nuclear Safety Inspectorate (ENSI) gives an overview of the radioprotection in its surveillance domain. Part A treats the protection of the personnel of the nuclear plants against the risk of ionizing radiation. It includes specially the sum of individual doses accumulated by the personnel. Applying the optimization principle, the yearly collective doses in the Swiss nuclear plants could be significantly reduced since the beginning of operation thanks to important efforts deployed by the plant operators, but also by the authorities. In 2017, on 5586 persons measured, 3478.2 pers.-mSv were accumulated. The collective doses have reached a low value, corresponding to the good radiological state of the plants and to the necessary work in the controlled zones (for instance non-destructive tests). The high value in the reviewed year compared to the preceding year is explained by a more important effort foreseen during the checks and related activities in the radiation domain at the Leibstadt nuclear plant. The individual doses of persons working in 2017 in the domain under ENSI surveillance remained clearly lower than the limit of 20 mSv for persons professionally exposed to radiation, with a maximum value of 14.2 mSv and a mean value of 0.6 mSv. The release of radioactive substances from the nuclear plants through air exchange and used water systems are treated in part B. In 2017 as well, the nuclear plants operators fulfilled the limits of effluents fixed by the authorities with large margins. On the basis of very conservative calculations, ENSI confirms that the effluents from the Swiss nuclear plants contributed to a dose lower than 0.007 mSv per year in their immediate neighbourhood. The comparison with a radiation dose of 5.8 mSv absorbed as a mean value each year by every Swiss resident shows that the part coming from nuclear facilities reaches a maximum of 0.1%. The liquid effluents from all Swiss nuclear facilities remained under the target value of 1 GBq per year (without tritium) fixed by ENSI on the basis of international recommendations. As the authorities require from the operators of the nuclear plants and in accordance with the international practice, tritium is separately limited and must be examined consequently. The definition of a target value allows to assure that the possibilities offered by the state of science and techniques are verified and applied on the form of technical solutions. By means of inspections and comparative measures, ENSI ascertains that the measurement instrument used for radioprotection, calibrated and standardized, are available and consistently used in order to determine correct measurement values. For this purpose, ENSI operates its own test laboratory accredited under ISO 17025. The measurement network operated by ENSI for the automatic surveillance of the dose rate in the vicinity of the nuclear plants (MADUK) works all the year and 24 hours per day. The mean values per hour, per day and for 10 minutes can be consulted on the ENSI site in real time. For the authorities and against the public opinion, this measurement network acts as a preservation of proofs. During the year under review, no increased dose rate value was recorded which could be attributes to effluents of nuclear plants. Some increased values can be explained by fluctuations of the natural radiation, for instance after rain falls. From the beginning of 2016, the program JRODOS (Java-based Real-time Online Decision Support System) is used for the simulation of the atmospheric spread and the dose rate calculation in case of incident. JRODOS allows direct use of 3D data from the meteorological forecast provided by the COSMO-1 model which is systematically used by MeteoSwiss with a 1 km mesh size. To take account of the landscape structure at small scale of Switzerland and the South region of Germany, JRODOS used the altimeter model at ultra fine spacing (DHM25) of the Swiss Federal Topography Office swisstopo. With these resources ENSI disposes of useful and precise instruments for the evaluation (diagnostics) and the forecast of the radiological status, as well as for formulating recommendations for protection measures for the population. These instruments are regularly tested during exercises. In 2017 a general emergency exercise was conducted with the nuclear plant at Muehleberg. A large number of partners participated in the exercise, as well as staffs or contact points in the neighbour states and the IAEA. The emergency organization of ENSI showed a high degree of performance in view of its mandate as described in art.9 of the ordinance on emergency protection. During the year under review, all the limit values of the radioprotection ordinance were fulfilled. The nuclear plants announced no event leading to an inadmissible radiation exposure for the staff or the population. ENSI concludes that the nuclear plants go on leading a good quality radioprotection by applying efficiently the optimization principle.