This 24-hour report is being issued in accordance with the requirements of NRC Certificate of Compliance 1030, Amendment 0, for the
NUHOMS Storage System,
Technical Specification (TS) 2.2, Functional Operating Limit Violations.
During a review of historical Surry NUHOMS Dry Storage Canister (DSC) loading certification documents, a discrepancy was identified. The NUHOMS Certificate of Compliance 1030 Amendment 0 Technical Specifications include a Figure 2, 'Heat Load Zones' which specifies the maximum decay heat load for each of the 32 assembly locations in a DSC. The figure includes limits for two zone '1b' locations and two zone '1a' locations in the four center locations of the DSC. The zone '1b' decay heat limit of 0.800 kw is specified for the two 'upper compartments' and zone '1a' decay heat limit of 1.05 kw is specified for the two 'lower compartments' on the figure. Contrary to this, the loading certifications for 6 of 12 DSCs already loaded at Surry were not developed to maintain this orientation when loaded in the horizontal storage module (HSM). As a result, the DSC zone '1b' heat load limits were exceeded in some cases for these 4 DSCs.
The heat load limit for all other zones in the DSCs are symmetric, and those assemblies were verified to the correct limit and are unaffected by this error. In addition the total heat load limit for the sum of the center assemblies was met for all DSCs. The maximum heat load of any zone '1b' assembly at the time of loading was 0.806 kw, which is slightly higher than the 0.800 kw limit. The lower heat load of assemblies in the other compartments offset the slightly higher heat load effects, and it is expected that the thermal analysis acceptance criteria would still have been met at the time of loading.
The decay heat of the assemblies has continued to decrease since their initial loading and all assemblies currently meet the upper central compartment limits. The affected fuel assemblies are in a safe condition as required by NUHOMS TS 2.2.1.
The NRC Resident Inspector has been notified of this event.
