Intercomparison of Reaction Rate and Gamma Scan Measurements and Calculation Analyses in a Pressurized Water Reactor

Abstract

Measurements made during cycle 1 operation of Commonwealth Edison Company's Zion Unit 2 pressurized water reactor core were used to validate the Electric Power Research Institute Advanced Recycle Methodology 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 X-Y gamma scan behavior supported the behavior of the calculated X-Y reaction rates. The measured X-Y gamma scans were found to be more accurate than the measured X-Y 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.