Publications Details

Burnup Verification Measurements at U.S. Nuclear Facilities Using the Fork System

Ewing, Ronald I.

Burnup verification measurements have been performed using the Fork system at the Oconee Nuclear Station of Duke Power Company, and at Arkansas Nuclear One (Units 1 and 2), operated by Energy Operations, Inc. Passive neutron and gamma-ray measurements on individual spent fuel assemblies were correlated with the reactor records for burnup, cooling time, and initial enrichment. The correlation generates an internal calibration for the system in the form of a power law determined by least squares fit to the neutron data. The average deviation of the reactor burnup records from the calibration determined from the measurements is a measure of the random error in the burnup records. The observed average deviations ranged from 2.2% to 3.5% for assemblies at the three reactor sites, indicating a high degree of consistency in the reactor records. Anomalous measurements were also observed but could be explained by the presence of neutron sources in the assemblies. The effectiveness of the Fork system for verification of reactor records is due to the sensitivity of the neutron yield to burnup, the self-calibration generated by a series of measurements, the redundancy provided by three independent detection systems, and the operational simplicity and flexibility of the design.