Radiation protection issues for EPR reactor

As part of the EPR (European Pressurized Reactor) project being deployed at Flamanville, EDF has pro actively made the decision to focus on radiation protection Radiation Protection aspects right from the start of the design phase, as it has done with nuclear safety. The approach adopted for managing Radiation Protection-significant activities has been to include all involved stakeholders - designers, licensee and contractor companies - in the three successive phases, starting with a survey among workers and designers, followed by a proposal review, and finally ending with the decision-making phase entrusted to an ALARA committee. The Radiation Protection target set by EDF for this new reactor is to engage in an effort of continuous improvement and optimisation, through benchmarking with the best performing plants of the fleet. The collective dose target is currently set at 0.35 Man Sv/year per unit. In addition to other aspects, efforts will focus on shortening the duration of the highest-dose jobs, with a new challenge being set for work performed in the reactor building during normal operations, the aim being to improve plant availability. The plan is for work to be performed 7 days prior to shutting down the reactor and 3 days afterwards, in order to make logistical arrangements for forthcoming jobs. Without this reduction, the estimated drop is currently 4.5% of annual dose. For this purpose, two areas have been set up in the E.P.R.'s reactor building: one no-go area for containing leaks from the primary circuit, and one accessible area for normal operations, separated from the no-go area by purpose-built ventilation equipment and facilities. To offer protection against radioactive flux (neutrons and high energy), Radiation Protection studies have resulted in the installation of a concrete floor and of nuclear shielding at the outlets of primary circuit pipes. Steam generator bunkers and pumps have also been reinforced. All these measures will ensure that the accessible area can be posted as a green area (dose rate < 25 μSv/h), with a neutron dose rate of less than 2.5 μSv/h. In order to optimise radiation exposure on the EPR, efforts have focused on two parameters factored into dose calculation: dose rate and work volume exposed to radiation. The main R.P. design upgrades are improvements upon the most recent N4 plant series. In order to ensure radiological cleanliness, contamination must be contained as close to the source as possible on working units. This type of zoning is essentially aimed at enabling the plant to generate conventional waste from the radiologically controlled area in order to reduce the quantity of nuclear waste produced, to reduce nuclear waste volumes during the dismantling phase and to reduce the number of areas with a contamination risk, thereby preventing the transfer of contamination to areas outside the plant. In total, this optimisation effort has resulted in a saving of 21% when comparing the reference dose with the optimised EPR dose. A strategic priority for the EDF Group, radiation protection is gradually becoming less and less confined to the happy few, and is becoming a cross-functional area where multi-disciplinary team work is of paramount importance from the very start of the design phase. (authors)