The Application of Adjoint Transport Calculations to Ex-core Detector Calibration

Abstract

Ex-core detectors at the core periphery are regularly calibrated to correctly measure core power axial offset during operation. A conventional method for ex-core detector calibration requires use of in-core detectors to measure core power distribution several times. It employs the least square method to obtain proportional constants used for ex-core detector calibration. Simplified Ex-core Detector Calibration (SEDC) presented here requires only a core power distribution measurement. It combines three-dimensional power distribution calculated from a nodal calculation and weighting factors calculated from (r-z)and (r-q) adjoint transport calculations to generate detector response factors. The detector response factors involves effects of assembly-wise importance of neutron as well as core axial importance of neutron to a ex-core detector. The effects of core burnup, coolant temperature and core power on the accuracy of the SEDC are also explored using Koriunit 3 data. The application of the SEDC to Kori unit 3 cycle 9, 10 and 11 shows average error of 0.179% and maximum error of 0.629%.