Improving NSSS design to reduce occupational radiation exposure

Operating experience with 900-MWe and 1300-MWe nuclear units in France and Belgium has shown that average collective doses during plant operation and maintenance are lower than those recorded in other countries, including the USA. 80 % of collective doses are a result of the activation of corrosion products in the primary coolant system. To reduce occupational radiation exposure (ORE) it is necessary: 1) to decrease the source and quantity of corrosion products susceptible to activation; and 2) to reduce maintenance personnel exposure time through training and improved maintenance tooling and robotics. Experiments in test loops and plant measurements have been carried out to understand corrosion product deposition and migration processes. A computer program named PACTOLE and developed by the CEA (French Atomic Energy Commission) has been qualified on several loop experiments for predicting dose rates. Periodic decontamination is being considered for steam generator channel heads to facilitate maintenance or heavy repairs. To reduce occupational radiation exposure of maintenance personnel, Framatome's service division has developed and built a large variety of remotely operated tooling to avoid maintenance personnel being in high radiation areas while work is being carried out on reactor equipment during plant shutdown. 1 fig., 1 tab