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Impact of Main Radiological Pollutants



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Impact of Main Radiological Pollutants on Contamination Risks ALARA Optimisation of Physico Chemical Environment and Retention Technics during Operation and Shutdown A Rocher Electricit de France GPR J L Bretelle Electricit de France GDL M Berger Electricit de France SEPTEN 1 Introduction The goal of this paper is to precise the behaviour of different radiochemical species in the primary coolant of PWR plants Managing these pollutants must lead to limit Reactor Coolant System RCS walls overcontamination to decrease the dose rates during the maintenance operations ALARA In French Plants Co 60 silver and antimony represent the major radiochemical pollutants which require a good knowledge of the different phenomena to ensure the lowest contamination risks The stakes deal with the control and the optimization of collective and individual doses including waste treatment with low costs These stakes represent primordial elements of nuclear acceptability 2 Normal contamination of circuits In French PWR plants More than 90 of integrated doses are due to contaminated walls in contact with the primary coolant because of activated corrosion products 80 of total dosimetry are integrated during outages In the absence of specific pollution the mean contribution of out of core deposits to dose rates is as follows results expressed as percentage equivalent dose rates in Sv h Co 60 50 the older the plant the greater the Co 60 quantity Co 58 30 with a higher level in 1300 MW units Ag 110m Sb 124 Cr 51 10 Usual contaminants come mostly from materials coolant interactions leading to soluble particulate colloidal products transport and corrosion products activation table 1 Nuclides Half life Co58 71 days Co60 5 3 years Ag110m 253 d Sb124 60 d Sb122 2 7 d Gamma energy keV emission 811 100 1173 100 1333 100 658 100 885 80 603 98 564 66 Beta energy keV emission 318 100 86 55 610 51 1400 63 Table 1 Gamma and beta energies and emission percentage 50 of major pollutant nuclides The dose rates



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