Decommissioning the research reactors of the German Cancer Research Center in Heidelberg. Experience accummulated in 'Safe Enclosure' and 'Direct Disposal' as shown by the examples of the TRIGA HD I and TRIGA HD II reactors

Between 1966 and 1977 and 1978 and 1999, the German Cancer Research Center (DKFZ) in Heidelberg ran 2 TRIGA Mark I research reactors to produce radioisotopes for medical applications and for cancer therapy. In its approaches to decommissioning and disposal of the 2 reactors, the DKFZ at different points in time carried out both 'safe enclosure' and 'direct disposal'. The TRIGA HD I research reactor was put into 'safe enclosure' following its last decommissioning phase in August 1977, and has been in the final stages of dismantling since January 2006. The TRIGA HD II research reactor, which was shut down in December 1999, has been in the direct demolition and disposal phases since September 2004. Decommissioning these 2 reactors of similar designs, and evaluating the information available about the 2 decommissioning projects, allows the two decommissioning options to be compared and their potential pros and cons to be worked out in the light of practical, albeit special, examples. The article presents some initial findings made in this comparison. It should be noted, however, that these results must not be generalized or translated directly to other decommissioning projects. (orig.)