Charpy trend-curve development based on PWR surveillance data

A least-square analysis has been used to determine functional relationships connecting (a) the irradiation-induced increase in the 41 J Charpy transition temperature, (b) the pressure vessel steel chemistry, and (c) the irradiation fluence. The data base consisted of 41 weld metal points and 106 base metal points. Functional forms investigated were of the type Temperature Increase = F (chemistry).(fluence)/sup N/. The exponent N was weakly fluence dependent. In the least=square procedure, the temperature shift and the fluence were both considered inexact quantitites. Fluence errors were included in the quantity to be minimized. This is necessary to avoid a bias in the exponent that would misrepresent the extent of saturation. Separate equations were used for plates and welds, resulting in standard deviations of 15.6 deg F and 26.4 deg F, respectively. Covariance matrices are supplied for use in error propagation calculations. A method is given for converting the formulas to use dpa as an exposure unit for applications involving deep wall penetration. A tabular description shows the range of chemistry (Cu, Ni) values available in the data. (author)