Validation of toughness assessment methodology by RPV SAW sampling

The question of the independent validation of the irradiated toughness methodology and its comparison with actual data was raised in the early 1990s because of two factors  

Fast neutron doses were measured by counting the Mn activity on the cube samples through the RPV wall thickness. The doses obtained were in good agreement with those predicted by the MCBEND code. Chemical analysis of weld metal from all four layers showed remarkable consistency in composition both along and through the weld. Table 7.5 shows that the four weld compositions were similar and compared favourably with the weld compositions obtained from other vessel cut-outs and surveillance 

8 Fracture toughness data fronn Trawsfynydd RPV and surveillance SAWs. (Reproduced with the permission of the Institute of Materials, Minerals and Mining and W. S. Maney and Son Ltd.) 

The success of the sampling programme gave confidence in the methodology for RPV assessment and confirmed the value of a mechanistic understanding of the surveillance programme results. 

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