Mechanistic framework to develop dose-damage relationships DDRs

13 Mechanistic framework to develop dose-damage relationships (DDRs) 

The insight developed into the mechanisms of controlling matrix damage formation and solute clustering have led to the adoption of a simple mechanistic framework that underpins the development of dose-damage 

The mechanistic framework comprises three major components  

The first two mechanisms contribute to embrittlement by increasing the hardness of steel as illustrated in Fig. 9.41. The third mechanism induces embrittlement without hardening. The latter mechanism is not necessarily found in all RPV steels under operating conditions. Indeed, for Mn-Mo-Ni steels irradiated in surveillance schemes in western light-water reactors (LWRs), the observed embrittlement is associated with the first two mechanisms (see Fig. 9.41), i.e. the total shift in the ductile to brittle transition, as measured at the Charpy 41J level, is 

There has been successful development of DDRs for both C-Mn and Mn-Mo-Ni steels.The approach has been to base the mathematical forms of the expressions within the DDR, and the inclusions of particular input variables (e.g. Cu content, irradiation temperature) on mechanistic understanding (such as the framework depicted in Fig. 9.41). The values of the associated coefficients were then determined by fitting to the surveillance database. Different DDRs have been developed in different 

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