Embrittlement correlation methods Europe

In France, initially, US Regulatory Guide 1.99, Revision 1 was recommended. Then several irradiations were made in test reactors with split melts varying the level of residual elements. From these data, Guionnet and co-workers produced several equations. These trend equations included the effect of known embrittling elements but also included the effect of elements such as P, Sn and N. An analysis of a larger database was made by Brillaud et al., and from this evaluation the so-called FIS and FIM formulae were derived. 

The FIM equation corresponds to mean behavior and is of the general form of [CF]-[FF]  

The FIS equation is very similar, but has margin built in to bound the predictions  

It is important to note that in these formulae Ni and Cu have a synergistic effect, the efficiency of P is significantly greater than that of Cu (per wt%), and the fiuence exponent is close to 1/3. 

There are four main types of reactors in France CPO (900MWe), CPY (900MWe), P4 and P 4 (1300MWe) and N4 (1400MWe). The surveillance data from six CPO reactors and 26 CPY reactors as well as the test reactor data, including those obtained after the development of the FIS model, were used for the calibration of a new embrittlement correlation method. The surveillance database includes 139 pieces of base metal data, 130 weld metal data, 131 heat-affected zone (HAZ) data and 93 standard reference material (SRM) data, while the test reactor database contains 36 pieces of 

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