The status quo on HTGR decommissioning

Abstract

Five High-Temperature Gas-Cooled Reactors, which have been operated in the past, are now in different stages of decommissioning. The present status, technical approaches and experiences are described for AVR, DRAGON, FSV, Peach Bottom Unit 1 and THTR.After defueling the core, the Reactor Pressure Vessel (RPV) of AVR has been grouted with low-density cellular concrete and removed from the containment building. The RPV is now stored in a new interim storage building, on the site of the Juelich research center. The DRAGON reactor was operated in UK from 1965 until 1976 when it was defueled and put into safe storage. It was partially decommissioned in 2005 and is now facing further removal steps with a target decommissioning completion date of 2022. The 330 MWel Fort Saint Vrain (FSV) HTGR in US was shut down in 1989 and undergone immediate dismantling with a fixed-price contractor. The plant site was released for unrestricted use in August 1997. The Peach Bottom Unit 1 was shut down in 1974. The spent fuel was transferred to INL. Decommissioning is not expected until 2034, when the other LWR units at this site are scheduled to shut down. The German 300 MWel Thorium High-Temperature Reactor (THTR) was closed-down in 1989 and resides under Safe-Enclosure conditions since 1997, after having evaluated the radiological consequences of direct dismantling vs. 30 years safe enclosure.The 32 MWel Windscale Advanced Gas-Cooled Reactor (WAGR) prototype shows some relevant design similarities to modular HTGR. Lessons learned from the WAGR and other relevant decommissioning projects are therefore addressed, too.As a general conclusion, it can be stated that the decommissioning procedures need to be thoroughly reflected already during the design of any new HTGR project.The paper has been elaborated within the European GEMINI+ project and is based on the deliverables of the Task ‘Decommissioning and Waste Management of the GEMINI+ system’.