ML121800306
| ML121800306 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 06/28/2012 |
| From: | David Bice Entergy Nuclear Operations |
| To: | Kalyanam N Plant Licensing Branch IV |
| Kalyanam N, NRR/DLPM, 415-1480 | |
| Shared Package | |
| ML121800304 | List: |
| References | |
| TAC ME8282 | |
| Download: ML121800306 (17) | |
Text
License Amendment Request NFPA 805 Acceptance Review Arkansas Nuclear One Unit 2 June 29, 2012
Technical Acceptance Issues
- Modification Details
- The modifications for transition need to be described and, as appropriate, modeled in the probabilistic risk analysis (PRA) to properly estimate the change in risk associated with transition
- The License Amendment Request (LAR) needs to be supplemented with the descriptions of these modifications and provide adequate information to review the evaluations supporting these modifications supporting these modifications
- Risk Estimates for Recovery Actions (RAs)
- About one third of the fire areas in the Additional Risk of RAs column of Table W-2 of the LAR do not contain a quantitative risk result
- The LAR needs to be supplemented with the quantitative RA risk estimates to demonstrate that the evaluations supporting the transition have been satisfactorily completed
Technical Acceptance Issues
- RAs Credited for Control Room (CR) Abandonment
- Attachment G of the LAR states that ANO-2 has no primary control station, besides the main CR, yet only eight RAs are identified for Fire Area G
- Unclear how both the total change in risk and the additional risk from RA is bounded by a risk estimate of 0.0
- The LAR needs to be supplemented with additional discussion about the planned modifications and RAs, and how these are d l d i th PRA i ffi i t d t il t l i th modeled in the PRA in sufficient detail to explain the unexpected results
- Sensitivity Study
- Two sensitivity studies compare the results based on one unaccepted method to results based on another unaccepted method
- The LAR needs to be supplemented with the risk results (in relation to the sensitivity analyses for non-suppression probability for long-term fires and adjustment factor for electrical cabinet ignition frequency) calculated using an acceptable analysis method
Technical Acceptance Issues Response Overview Modification Details
- Attachment S revised to provide additional detail for proposed modifications Risk Estimates for Recovery Actions (RAs)
- Additional analysis performed to address the risk estimates of the quantitative RAs and included in revised Table W-2.
RAs Credited for Control Room (CR) Abandonment RAs Credited for Control Room (CR) Abandonment
- Additional information to be provided relating to Fire Area G and how the modifications and RAs were modeled in the Fire PRA. Table G-1 and Table W-2 are revised accordingly.
- List of defense-in-depth RAs will be included Sensitivity Study
- A new sensitivity analysis has been completed in compliance with NUREG/CR-6850 for comparison to the current results
- Further analysis is needed to accurately reflect the risk and minimize the need for unnecessary plant modifications
- Attachment V revised to capture revised sensitivity analysis.
- The modifications for transition need to be described and, as appropriate, modeled in the PRA to properly estimate the change in risk associated with transition
- The LAR needs to be supplemented with the descriptions of these modifications and provide Item 1 Modification Details descriptions of these modifications and provide adequate information to review the evaluations supporting these modifications
- Detailed final plant configuration descriptions have been completed and will be discussed for the 16 modifications identified
- Attachment S revised to provide additional detail for proposed modifications Item 1 Modification Details
- Modifications will be implemented in a manner that supports the assumptions of the Fire PRA
Proposed Attachment S Revision
Item 2 Risk Estimates for RAs
- About one third of the fire areas in the Additional Risk of RAs column of Table W-2 of the LAR do not contain a quantitative risk result
- The LAR needs to be supplemented with the quantitative RA risk estimates to demonstrate quantitative RA risk estimates to demonstrate that the evaluations supporting the transition have been satisfactorily completed
Item 2 Risk Estimates for RAs
- The delta risk from recoveries have been generated and the results are being finalized
- Delta risk of recoveries are based upon post transition model with modifications
- Results will be provided in a revision to Attachment W of the LAR
Item 2 Risk Estimates for RAs - Example
- Attachment G of the LAR states that ANO-2 has no primary control station, besides the main CR, yet only eight RAs are identified for Fire Area G
- Unclear how both the total change in risk and the additional risk from RA is bounded by a risk Item 3 RAs Credited for CR Abandonment additional risk from RA is bounded by a risk estimate of 0.0
- The LAR needs to be supplemented with additional discussion about the planned modifications and RAs, and how these are modeled in the PRA in sufficient detail to explain the unexpected results
- The 0.0 for delta CDF and LERF will be removed from Attachment W and replaced with actual change in risk values
- Attachment G updated for Fire Area G (CR) to show defense in depth actions in addition to the Item 3 RAs Credited for CR Abandonment show defense-in-depth actions in addition to the key risk based RAs
- A description of the modeling details for CR abandonment will be included in the supplement
- Two sensitivity studies compare the results based on one unaccepted method to results based on another unaccepted method
- The LAR needs to be supplemented with the risk results (in relation to the sensitivity analyses for non-suppression probability for long-term Item 4 Sensitivity Study for non suppression probability for long term fires and adjustment factor for electrical cabinet ignition frequency) calculated using an acceptable analysis method
- A new sensitivity analysis based upon post transition model with modifications is being completed to comply with NUREG/CR-6850 for comparison to the current results
- Public meeting on June 12, 2012 provided preliminary results of unscreened fire scenarios due to sensitivity without reliance on panel factors Item 4 Sensitivity Study
- Additional unscreened scenarios have been added stemming from the adjustment of manual suppression of long term fires that were lower than.001
- Delta risk input has also been calculated and is available for review
- Further analysis is needed to accurately reflect the risk and minimize the need for unnecessary plant modifications
Impact on ANO-1 LAR
- The ANO-1 LAR will require revision to address items identified for ANO-2
- The ANO-1 LAR submittal is scheduled for August 31, 2012
Summary ANO-2 supplemental response will be provided by July 11, 2012 addressing identified gaps in the original LAR.
Questions ??