Analysis of the VENUS PWR Engineering Mockup Experiment - Phase I: source distribution

Technical Report · Wed Aug 01 04:00:00 EDT 1984

OSTI ID:6505493

Morakinyo, P O; Williams, M L; Kam, F B.K.

The neutron fission source distribution in the core of the VENUS PWR Mockup Experiment is computed and compared to experimental measurements. This experiment is an important component of the USNRC's program goal of benchmarking reactor pressure vessel (RPV) fluence calculations in order to determine the accuracy to which RPV damage can be computed. Of particular concern is the accuracy of the source calculation near the core-baffle interface. Calculations were performed with two-dimensional discrete ordinates transport theory, using cross sections based on ENDF/B-IV data. In addition to in-core fission rate calculations, several ex-core fission chamber responses were computed. The accuracy of the calculations were evaluated by comparison with the experimental measurements. Results indicate that the calculated neutron source distribution within the VENUS core agrees with the experimentally measured values with an average error of less than 3%. At the important core-baffle interface, the agreement is within 3% error, except at the baffle corner, where the error is about 6%. The ex-core results are also in good agreement with measurements, except at the circular steel barrel, which was approximated into a rectangular geometry. It was discovered that a better accuracy in the calculations can be obtained by applying a detailed space dependent cross-section weighting procedure to the core-baffle interface region. Using this cross-section weighting in a two-dimensional transport theory calculation of a well-defined LWR core, the maximum error introduced into the predicted RPV fluence due to source errors should be on the order of 5%. However, in power reactor analysis, additional complexities (such as the time-dependent core composition and the use of few group diffusion theory) could affect this uncertainty value.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6505493
• Report Number(s): NUREG/CR-3888; ORNL/TM-9238; ON: TI84015873
• Country of Publication: United States
• Language: English

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