Design problems in reactor decommissioning

The paper will use two examples from the decommissioning programme of the Windscale Advanced Gas-Cooled Reactor to illustrate the kinds of design problem encountered and the approaches to their solution. The examples are: removal of the core restraint bands and removal of insulation from the exterior of the pressure vessel. The first case consists of careful investigation and analysis to predict the present state of the core and restraint bands before removal methods can be considered. There is much uncertainty involved in the design process to find the best method. In contrast, the condition of the vessel insulation is known to a high degree of certainty, as are most of the design constraints to this problem. The paper will discuss the work so far undertaken on the restraint band problem and the design methods to be employed to determine a suitable technique for removing the insulation. (author)