PROBLEMS OF DECOMMISSIONING GAS COOLED REACTOR

1 Gas cooled nuclear generating plants In commercial operation In the U.K. at the present time are based either on the magnox reactor system or the advanced gas cooled reactor system. The magnox reactor systems utilise single cavity pressure vessels, the earlier ones being of steel construction, the later ones of prestressed concrete. The advanced gas cooled reactor systems utilise either single cavity or multicavity pressure vessels of prestressed concrete construction. 

3 Site plans of and sections through typical magnox and advanced gas cooled stations are shown in figures 1,2,3 and 4. 

5 These different types of problem are discussed more fully in Sections 5.2 and 5.3 below. 

3 It is In the breaking up and removal of this inner layer of active concrete and its embedments and attachments, whilst maintaining the integrity of the structure to retain dust, that the major civil engineering problems of decommissioning the pressure vessel lie. 

4 In considering radiological problems associated with decommissioning it is important to recognise the differences between the activity of a material, the radiation dose a person would receive from being in the proximity of such a material and contamination. 

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