Accounting for Changing Source Distributions in Light Water Reactor Surveillance Dosimetry Analysis

A technique is described to account for effects of space- and time-dependent core source variations on pressure vessel surveillance dosimetry analysis. The procedure first defines an easily implemented geometry for a single adjoint transport calculation. The results from the adjoint calculation can then be combined with those from a single forward calculation, in conjunction with an adjoint scaling technique, to yield activities and pressure vessel fluxes simultaneously for a wide range of source distributions, dosimeter response functions, and detector locations. This method has been implemented in the LEPRICON code system for vessel fluence determination. An application to an R-θ model of an operating power reactor shows that effects of source perturbations resulting in 20% changes in the core leakage can be predicted within ∼3% at both downcomer and cavity dosimeter locations, for six different dosimeters, by choice of a single suitable adjoint response function.