Full System Decontamination (FSD) with the CORDR Family prior to Decommissioning - Experiences at the German NPP Obrigheim 2007

Minimizing personal radiation exposure and obtaining material free for release are the highest priorities for the decommissioning of a NPP. This calls for a FSD as the first and most effective measure. AREVA NP has a long experience with FSDs, not only for operating plants but also for decommissioning in particular. Starting 1986 with the first decontamination for decommissioning at the NPP FR2, a German research reactor, AREVA NP has performed more than 10 FSDs worldwide prior to NPP dismantling. Based on these long term decontamination experiences including the successful performance of the FSD at the German PWR in Stade 2005, AREVA NP received the contract for the FSD prior to decommissioning at the German PWR in Obrigheim (357 MWe). The NPP Obrigheim was permanently shut down in May 2005 after 36 years of operation. The decontamination of the complete primary circuit and the auxiliary systems RHR and CVCS was performed in the first quarter of 2007. The total system volume was 160 m3, total system surface approximately 8100 m2. Decontamination was carried out with the worldwide approved decontamination process HP/CORD D UV, using NPP own systems and the AREVA NP AMDA decontamination equipment. In the paper detailed results of the decontamination will be outlined. An important value for further decommissioning activities was the remarkable dose rate reduction at the heavy components, especially the steam generators. The average decontamination factor achieved at the systems exceeded the value of 600. (author)