ML18320A060
| ML18320A060 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 11/07/2018 |
| From: | Fletcher C Duke Energy Carolinas |
| To: | Juan Uribe Beyond-Design-Basis Management Branch |
| Uribe J | |
| References | |
| Download: ML18320A060 (8) | |
Text
From:
Fletcher II, Cecil Alexander To:
Uribe, Juan Cc:
Andrews, Sherry E; Guill, Paul F; Davies, Darrell K
Subject:
[External_Sender] FW: Catawba MSA Review - Info Needs #5 Date:
Wednesday, November 07, 2018 1:10:23 PM Attachments:
image001.png image002.png Catawba MSA Review -Info Needs Set. 5.pdf
- Juan,
Please see the Catawba response for the MSA Review, Info Needs #5 attached.
Best Regards,
Cecil Alexander Fletcher II Catawba Nuclear Station, Manager Nuclear Regulatory Affairs 803-701-3622 (Office) / 404-824-9212 (Mobile) cecil.fletcher@duke-energy.com
Mitigating Strategies Assessment - Flooding Audit Catawba Nuclear Station Information Needs Set #5
- 1. LIP Regarding the CDB FLEX strategies, the MSA states on Section 3.5 that flood barriers were determined to be necessary for the outside lower edge of doors AX656B and AX658A.
Regarding the protection of these doors, please:
Provide a physical description of the type of flood barrier that is being used, including dimensions. The description should confirm that the barrier has sufficient margin such that it is acceptable for use against the higher reevaluated hazard (0.6 delta).
CNS Response:
The flood barrier described in the portion of AP/0/A/5500/030 shown below is not designed for a specific height. It's design is to restrict water inflow through doors AX656B and AX658A (information for AX658A only shown below but information for AX656B is similar).
Since the flood barrier design basically plugs gaps in the doorway to restrict water flow, the amount of water ingress into the rooms protected by these doors will remain essentially unchanged with varying heights of flood levels. In other words, seepage of water through the Water Adsorbent Dam material and sandbags does not change appreciably due to different amounts of water pressure being applied (i.e. changes in flood elevation).
7-18-18 Update:
As follow-up to the NRC onsite audit on 7/11/18, Catawba Nuclear Station (CNS) will modify the existing flood barrier described in AP/0/A/5500/030 to eliminate in-leakage concerns at doors AX656B and AX658A. The modified flood barrier will be a sandbag type following the guidance found in the US Army Corps of Engineers Northwestern Division 2004 Sandbagging Techniques brochure and the US Army Corps of Engineers St. Paul District 2016 Flood Fight Handbook for a typical pyramid shaped barrier. The barrier for doors AX656B and AX658A will actually be one half of a pyramid since the vertical face of the barrier will be up against the door and Auxiliary building wall. The height of the barrier will be 3 feet (top elevation of approximately 596.5 ft. Mean Sea Level) which provides approximately 1.0 feet of margin above the maximum LIP flood level on the Unit 1 side of the site and approximately 0.9 feet of margin above the maximum LIP flood level on the Unit 2 side of the site. The width of the half pyramid will be approximately 4.5 feet at the base.
Mitigating Strategies Assessment - Flooding Audit Catawba Nuclear Station Provide a description of the estimated amount of time needed to deploy and setup the flood barriers. The description should confirm that the warning time deployment trigger of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> is adequate.
CNS Response:
Materials to install the flood barriers for doors AX656B and AX658A are stored on a pallet next to each door. It is estimated that it would take one person approximately 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> to deploy and install the flood barrier at one door as described in AP/0/A/5500/030.
7-18-18 Update:
Based on the revised response to the first bullet of Question #1, it is estimated that it will take three people approximately 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> to obtain about 350 sandbags from Building 7780 and install the new half pyramid design barrier for each door. Note that there are approximately 2000 sandbags stored in Building 7780.
Mitigating Strategies Assessment - Flooding Audit Catawba Nuclear Station If available, any pictures of the barriers installed and/or the staging area outside the Unit 1 and Unit 2 Auxiliary Buildings would be helpful in the response.
CNS Response:
See pictures below.
Unit 1 door AX658A
Mitigating Strategies Assessment - Flooding Audit Catawba Nuclear Station Unit 2 door AX656B
- 2. LIP Regarding the modified FLEX strategies, the MSA states on Section 6.2.2.7 that the LIP event coincident with an ELAP may cause the two groundwater drainage system (WZ) pumps (A and B pumps) to fail. Regarding the protection of the pumps, please:
Provide a physical description of the type of flood barrier that is being used, including dimensions.
CNS Response:
The maximum reevaluated LIP flood levels from HDR calculation CNS-194292-009 Rev. 0 (CNS Site Analysis of Local Intense Precipitation) for Node 7 is 595.5 ft. MSL (general location of WZ sump room B) and 594.9 ft. MSL for Node 15 (general location of WZ sump room A). Therefore, an adequately designed flood barrier will only need to be provided at the B WZ sump room door since the A and B WZ sump room door thresholds are at elevation 595.0 ft. MSL.
Mitigating Strategies Assessment - Flooding Audit Catawba Nuclear Station In the FLEX strategies, it is preferred to use the WZ pumps versus portable sump pumps to help control any additional internal Auxiliary Building flooding caused by external flooding inputs into the WZ sumps (Note that the Auxiliary Building WZ sumps are interconnected via an underground drainage system. As such, water entering the B WZ sump will also flow into the A WZ sump). When evaluating internal Auxiliary Building flooding for the MSA LIP event, it was determined that the portable sump pump FLEX strategy could not be implemented in time to protect FLEX related equipment within the Auxiliary Building when considering the additional Beyond Design Basis LIP event input via the B WZ sump room.
Since the FLEX strategies work under Current Design Basis LIP flooding conditions, there are presently no flood barriers used to protect the B WZ sump room and one will need to be developed.
7-18-18 Update:
Catawba Nuclear Station (CNS) will provide a typical pyramid shaped sandbag type flood barrier for the B WZ door using the guidance found in the US Army Corps of Engineers Northwestern Division 2004 Sandbagging Techniques brochure and the US Army Corps of Engineers St. Paul District 2016 Flood Fight Handbook. The barrier for the B WZ door will actually be one half of a pyramid since the vertical face of the barrier will be up against the door and Auxiliary building wall. The height of the barrier will be 3 feet (top elevation of approximately 596.5 ft. Mean Sea Level) which provides approximately 1.0 feet of margin above the maximum LIP flood level. The width of the half pyramid will be approximately 4.5 feet at the base.
Provide a description of the estimated amount of time needed to deploy and setup the flood barriers. The description should confirm that the warning time deployment trigger of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> is adequate.
CNS Response:
Assuming CNS will use a typical US Army Corps of Engineers sandbag barrier type design for the B WZ sump room door, it is estimated that it will take one person approximately 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> to retrieve the sandbags from a storage location and build the barrier.
7-18-18 Update:
Based on the revised response to the first bullet of Question #2, it is estimated that it will take one person approximately 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> to obtain about 125 sandbags from Building 7780 and install the new half pyramid design barrier for the B WZ sump room door.
Mitigating Strategies Assessment - Flooding Audit Catawba Nuclear Station Identify whether any of the proposed door barriers will inhibit personnel access or deployment of the FLEX TDAFW sump pumps (or alternate portable pumps) and the associated portable diesel generators that power these pumps.
CNS Response:
The only doors that need to be opened to support FLEX strategies are the Electrical Penetration Room doors AX656B and AX658A. Per the Catawba FLEX Strategy Timing Study, deployment of equipment from the storage building does not begin for at least 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> from the start of the event. At the 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> timeframe, the reevaluated LIP flood levels are below the threshold elevations for AX656B and AX658A. As such, there are no concerns with opening these doors and removing any flood barriers previously installed.
The flood barriers are small enough that personnel could step over them if necessary.
There is also adequate margin in the Timing Study to perform any barrier removal activities to improve personnel or equipment movement through these door locations.
If available, any pictures of the barriers installed and/or the staging area outside the 7780 Building would be helpful in the response.
CNS Response:
B WZ Sump Room Door
Mitigating Strategies Assessment - Flooding Audit Catawba Nuclear Station Sandbags Stored in Building 7780
- 3. Estimated Completion of Proposed Actions The MSA states on Section 6.5 that FLEX strategies will be modified in order to address the unbounded LIP mechanism. These actions include:
Evaluation of the flood barriers in accordance with the guidance of NEI 12-06, Appendix G and the revision of flooding related procedures.
Revision of plant procedures to address the warning time.
Validate plant procedures in accordance with the guidance of NEI 12-06, Appendix E.
Please provide an estimated completion schedule of the proposed activities.
CNS Response:
The above actions will be completed no later than 2 years from effective date of the proposed Mitigating Beyond Design Basis Events Rule 10CFR50.155. The above actions are being tracked as an NTM (Nuclear Task Management) item.