Design Features and Operating Experience for Reducing Man Rems in French PWR

摘要

Operation of 900 MWe class PWRs in France and Belgium has shown that average collective radiation doses due to operation and maintenance are lower than those in other countries such as the United States of America. This can be explained by the fact that the design precautions taken by Framatome and the operating procedures established by the Electricite de France help to keep the dose levels low. As a result of R and D activities, Framatome has initiated concrete measures to help reduce personnel radiation exposure. These include reduction in the source and quantity of activable products, and in the duration of personnel exposure during maintenance. To reduce occupational radiation exposure, the following measures have been implemented: (1) reduction of the source and quantity of corrosion products susceptible to activation, and (2) reduction of maintenance personnel exposure time through adequate training before intervention on full-scale mock-ups and use of improved maintenance tooling. A better understanding of the migration process has been obtained by the development of analytical models and by the validation of these models by periodic dose field measurements on reactors. An optimized lithium hydroxide strategy for chemical control of the primary coolant is currently in use to reduce the deposition of corrosion products on equipment surfaces. Better specified materials used for the primary system and more stringent limitations on cobalt values for structural and fuel materials can also contribute to lower doses. The development of training on the decontamination system before intervention and use of maintenance tooling for servicing steam generator are also key-factors for reducing operating dose. (ERA citation 13:018183)