Removal of Standpipes

1 The standpipe assembly is contained within a 10m diameter circle of the pressure vessel top cap. It is central about the vertical axis of the reactor core and Is the means of access for fuelling and defuelling the reactor. Provision Is also made in the assembly for service penetrations used in monitoring and moderating the operational condition of the reactor. 

3 The extensive fabrication of the standpipe assembly Is completely attached to the liner roof and therefore ensures that the latter Is securely anchored to the top cap concrete of the pressure vessel. Any attempt at dismantling this area of a PCRV would automatically have to take Into consideration some method of detaching or dismantling the standpipe tubes. 

5 The layout of the standpipe assembly Is a function of the working of a nuclear reactor and It Is not envisaged that this layout could be changed In any way purely to facilitate decommissioning of a PCRV. The standpipe region has to withstand the internal pressures of a PCRV and consequently Its structural depth has to be consistant with the required minimum structural thickness of the PCRV. 

6 Activity levels, particularly in the lower portion of the standpipes, would require some or all of the dismantling in this area to be carried out by remote control methods. 

7 Hhllst the proposed method of dismantling a reactor core is not within the scope of this study it would seem that, from a practical demolition point of view, control of the dismantling of the reactor core would be greatly facilitated if a substantial overhead means of access were provided. This could be achieved if the entire standpipe assembly were removed thus providing a 10m diameter access directly over the core. 

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Outline scheme for removal of standpipe region to give access for removal of reactor core and Internals. 

Fig 41 OUTLINE SCHEME FOR REMOVAL OF STANDPIPE REGION TO GIVE ACCESS FOR REMOVAL OF REACTOR CORE AND INTERNALS... 

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