SPENT FUEL CASK CONTAMINATION IN GERMANY: ANALYSIS, FINDINGS AND SOLUTIONS

The problem of contaminated spent fuel casks became internationally apparent end of April 1998. At this time the Director of the French Nuclear Installations Safety Directorate (DSIN) informed French Ministries and foreign authorities of countries like Germany and Switzerland that in the past a substantial fraction of spent fuel shipments when arriving at the railway terminal in Valognes operated by COGEMA had shown contamination events on casks and railcars. The International Transport Regulations impose limits of 4 Bq/cm² for β/γ-emitting and 0.4 Bq/cm² for α-emitting radionuclides for the non-fixed surface contamination on packages carrying radioactive material. According to the control measurements on spent fuel casks leaving nuclear power plants for the reprocessing plant at La Hague the non-fixed surface contamination was originally below the specified limits. But control measurements on casks and transport wagons upon arrival showed that in a larger percentage of cases the 4 Bq/cm² limit was exceeded and in some cases by large factors. These findings initiated very intensive investigations and activities to solve this contamination problem in France, Germany, UK, Switzerland and other countries. In Germany this issue had a very high public and political weight for a long time and was broadly perceived as a major failure of nuclear industry. It became quickly evident that the observed contamination events when transporting spent fuel casks revealed deficiencies in contamination prevention and control measures, in administrative procedures and in the information system among the companies involved and to the authorities.