Extrapolation of surveillance dosimetry information to predict pressure vessel fluences

The traditional method of extrapolating comparisons between measured and calculated saturated foil activities at a surveillance position located near a reactor pressure vessel is to normalize the calculated fluxes to the unfolded measurements and assume the fluxes at the pressure vessel may be scaled by the same factors. A new method for obtaining both the fluence and an estimate of its uncertainty at any position extrapolated from information obtained at a surveillance position has been formulated. The technique involves a least-squares adjustment of the more sensitive nuclear data used, the measured activations, and the biases arising from methods approximations, followed by a corresponding modification of the calculated extrapolated fluence. Adjustment of the calculated fluence at the surveillance position is not necessary.