Conference call was held on 11/22/2011 with NRC SFST staff and Virginia Electric & Power Co and Dominion (the licensee). The purpose of the call was for the licensee to inform the NRC staff of actions it plans to take to inspect, evaluate, and repair the ISFSI Dry Cask Storage systems and components to ensure they remain capable of performing their required functions. The following is a summary of the licensee’s briefing and participants’ discussions.
NRC attendees: E. Love, J. Davis, J. Rankin, R. Temps, J. Sulima, C., Araguas, C. Fletcher Dominion attendees: Don Taylor, D. Sommers, T. Bayshore, B. Wakeman.
Dominion committed to providing a finalized action/inspection plan by mid-December covering the licensee’s ISFSI assessment activities and to provide weekly status reports during ISFSI assessment activities.
RIOB shall independently assess the licensee analysis and corrective actions to ensure that the licensee adequately addresses short- and long-term ISFSI issues. The review may include confirmatory walkdowns / inspections, and/or analyses, as appropriate.
Visual inspections by the licensee of both storage pads have been performed and more extensively, will continue through January, 2012. The licensee will utilize seismic data obtained from the reactor in order to estimate the peak acceleration values that occurred at both storage pad nos. 1 and 2. Dominion indicated that technical resources needed to perform spectrum analysis are now available. It is anticipated that the actual reactor spectrum will be translated to the ISFSI pads due to lack of seismic monitoring equipment at the pads. Dominion noted that completion of an engineering spectrum analysis is expected to be three to six months.
Once complete, the results will be made available to Transnuclear, Inc. (CoC holder) for system design and functional (DSC and HSM) evaluations. Further, Dominion stated a long-term sensitivity study for both pads using the translated seismic spectrum will be performed to address additional HSM loading scenarios and effects of the spectrum that occurred on components and any potential impact on future loadings. This sensitivity analyses will require an additional three months.
Concerning ISFSI Pad #1 (Casks), Dominion will consult SFST on the possibility of a licensing amendment to allow for sliding of the TN-32s and to address the deviation of 16 foot cask spacing requirement. Dominion also stated that seismic monitoring equipment will be installed at the ISFSI pads by end of December 2012. It is anticipated that installation of the seismic monitoring equipment at the ISFSl’s will be included as part of the licensee’s inspection plan.
ISFSI Pad No.2 (TN HUHOMS-HD 32PTH Horizontal Storage Modules (HSM»:
• Dry Shielded Canisters are stored in HSM-H horizontal storage modules and were loaded and are stored under a general license utilizing the Transnuclear storage
Certificate of Compliance (CoC) 1030.
• Dominion performed a Prompt Operability Determination and determined that the dry storage systems remain operable and continue to perform their design safety
• No damage or cracking occurred to the ISFSI pad.
• Damage to the HSMs was minimal. Spacing between several HSM roofs indicated slight movement of HSMs. Dominion concluded that minor damage to the loaded
HSMs did not impact structural capability of the HSMs.
• No movement of the bases of the loaded HSMs occurred.
• Radiological conditions are normal, no changes to HSM surface or area dose rates.
• Inlet and Outlet vents were inspected and no exterior blockage was found .
• More extensive visual examination of exterior and interior of loaded and unloaded HSMs.
• Three of thirteen loaded HSMs will be selected for interior inspection using a boroscope. In addition, doors of three HSMs will be removed to inspect seismic
ISFSI Pad No.1 (TN-32 Casks):
• The TN-32 casks stored on Pad 1 of the ISFSI were loaded and are stored under Dominion’s site specific ISFSllicense SNM-2507. The current licensing basis
requirements and commitments are described in the North Anna Site Specific ISFSI License FSAR and North Anna Site Specific ISFSI License technical Specifications.
• No damage or cracking occurred to the ISFSI pad.
• Radiological surveys indicated no changes to the casks surface dose.
• Visual inspections of the casks did not reveal any damage other than scraping of the coating (Non Safety Related) of the casks due to movement.
• Damage did not occur to the pressure monitoring system or remote monitoring panel.
No pressure monitoring alarms were received. No loss of electrical power at the ISFSI occurred.
• Pressure switch set-points had not drifted more than expected during normal operation and the helium overpressure was found to be normal on all casks.
• The licensee reviewed the data related to horizontal movement of the storage casks. The casks were installed at a spacing of 16 feet on center as described within the design feature section of the site specific ISFSI license Technical Specifications. Following the earthquake, the shortest distance observed between casks was 15 feet 3~ inches.
• The cask CoC holder, Transnuclear, Inc. (TN), performed a thermal analysis which evaluated casks at a 15 foot center-to-center spacing and below the decay heat
break point (27.1 kw). Negligible impact on the performance of the fuel cadding and that there would be no impact on components design function .
• Based on TN’s thermal calculations, the licensee currently advocates modifying the licenses to include the following new provisions:
– The casks not be returned to the original 16 feet separation Permit cask shifting (currently design basis does not include any shifting) and that a minimum allowable separation be established based on thermal effects calculations
• Visually examine five of the twenty five overpressure pressure monitoring systems by removing access covers.
- NRC – Dominion – Overview of North Anna Nuclear Power Plant Earthquake Response and Restart Readiness Demonstration Plan (enformable.com)
- Earthquake caused massive nuclear storage casks to move at North Anna (enformable.com)
- North Anna Asks for Exemption from CoC For 12 Fuel Assemblies Loaded In Dry Fuel Storage Over Decay Heat Limits (enformable.com)
- ISFSI Security Rule Status (enformable.com)
- NRC set to validate Dominion’s use of ‘unaccepted’ EPRI report to allow North Anna restart (enformable.com)
- March 31st, 2011 – Working on high priority spent fuel pool safety questions (enformable.com)