Intercomparison of reactor rate and gamma scan measurements in a PWR

Measurements made during Cycle 1 operation of Commonwealth Edison Company's Zion Unit 2 PWR core were used to validate the Electric Power Research Institute sponsored Advanced Recycle Mehodology Program. In addition to the usual reaction rate and axial trace measurements for determining power distributions, gamma scan measurements were available to provide additional data to validate the calculated power shapes. The parallel occurrence of gamma scan measurements and standard nuclear instrumentation measurements provided a unique opportunity to intercompare the results of these measurement methods. The calculated XY gamma scan behavior supported the behavior of the calculated XY reactor rates. The measured XY gamma scans were found to be more accurate than the measured XY reaction rates, with the latter showing significant differences among some symmetrically located assemblies. For both types of measurement, however, the modeling of the asymmetrically loaded assembly located furthest in the core periphery produced the poorest results. The axial gamma scan calculation proved very accurate except at the inlet and outlet regions