ALARA-based Strengthening of Radiation Protection in a high Dose Rate Nuclear Power Plant A practical overview

摘要

In the first years of operation the dose rates at G?sgen Nuclear Power Plant increased more stronglythan expected. Co-60 has been the main radiation contributor from the beginning. As an immediate step,investigations were initiated to find and remove unknown cobalt sources. System modifications and optimizationin water chemistry were carried out to reduce material and activity transport within the primary system. As aresult the dose rates were stabilized after a couple of years – unfortunately on a high level. To reduce the doserate levels and the occupational radiation exposure, further long term measures were implemented. Systemdecontamination and source replacement were considered as well as the implementation of enhanced shieldingprocedures and a more source oriented chemistry. As a result the dose rates have reduced significantly and theoccupational radiation exposure has been decreased by more than a factor of 2 over the last two decades. Thereduction of the mean individual dose turned out even better and was cut by a factor of 5. On terms of plant andpersonal safety, G?sgen Nuclear Power Plant decided to improve Radiation Protection using a smooth step bystep action plan and has been very successful with it. Currently the technical possibilities have been developed toa high standard. Further improvements will be selective only. In future the focus will be set to personal behaviorand human performance, using enhanced target settings, briefings, debriefings, experience feedback and(international) experience exchange. Nevertheless it will be essential to avoid unnecessary administrative andcounterproductive short term hurdles. Strengthening of Radiation Protection is and will be a long term andcontinuous process. G?sgen Nuclear Power Plant will continue to introduce further actions one by one.