ML15274A599
| ML15274A599 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 10/01/2015 |
| From: | Lisa Regner Plant Licensing Branch IV |
| To: | |
| Regner L | |
| References | |
| GL-04-002, GSI-191 | |
| Download: ML15274A599 (12) | |
Text
Description of Supplement 2 to STPNOC Risk-Informed Licensing Application to Address GSI-191 and Respond to GL-2004-02 Public Phone Call Meeting with NRC October 1, 2015
Introduction and Agenda
- Introduction of STP participants
- Desired Outcomes:
- NRC staff understand the STPNOC licensing application and the changes from the previous supplement
- Resolve NRC questions and establish follow-up to resolve questions that remain open
- Identify steps remaining for going forward with the application 2
Introduction and Agenda
- Agenda
- Overview of changes from November 13, 2013 letter (ML13323A183)
- Effect on reported results
- Conservatism and acceptability of revised approach
- RoverD In-Vessel Cooling Analysis
- Specific Focus Areas
- Debris Test Margin
- Follow-up and Going Forward Actions 3
Overview of Changes from November 13, 2013 Letter
- Changed methodology to explicitly incorporate certain deterministically-based elements Risk over Deterministic approach (RoverD) that was described in March 25, 2015 letter (ML15091A440)
- Added the plant-specific testing deterministic basis (Letter Attachment 1-2)
- Addressed all the NRC content guide questions and responded to earlier RAIs (Letter -5)
- Added the RoverD risk-informed description (Letter Attachment 1-3)
- Expanded Defense-in-Depth and Safety Margin discussion (Letter Attachment 1-4)
- Clarification on exemptions
- Changed exemption to 10CFR50.46 to be to other requirements (10CFR50.46(d))
- Clarified that a specific exemption to single failure is not being requested
- Added proposed Technical Specification change for debris-specific effects (Letter Attachment 3) 4
Overview of Changes from November 13, 2013 Letter
- What is no longer in the scope of the application and should not be part of the review, including RAI responses:
- CASA Grande calculation of conditional failure probabilities
- Use of correlations for head loss, including bump-up factors
- Uncertainty quantification of pipe break probability distributions; replaced with conservative estimates
- Time dependent debris transport
- Applications of CASA Grande that are still used
- Debris generation
- Debris arrival to the containment pool (non-time dependent) 5
Results with Revised Methodology Remain in RG 1.174 Region III
- Conclusions are unchanged with revised methodology
- 2015 RoverD:
CDF: 1.23E-07/yr, LERF: 3.08E-10/yr
- 2013 CASA Grande/PRA:
CDF: 2.88E-08/yr, LERF: 1.40E-11/yr 6
Conservatism and Acceptability of Revised Approach 7
Conservatism and Acceptability of Revised Approach
- Deterministically tested debris
- Qualitative margin evaluation of July 2008 test determined that low density fiberglass is the only debris source term not bounded by the test
- Used weld/break characteristics from NUREG 1829
- Considers various break types and locations
- Conservatisms used in transport calculation 8
RoverD In-Vessel Cooling Analysis
- T-H and Debris Analyses Show Adequate Long-Term Cooling
- Analysis assuming total blockage of core and core bypass shows that there is sufficient cooling for all HLB and all SLOCA (CLB and HLB)
- FA tests show that there is insignificant pressure drop for bounding HLB conditions (DEGB, no credit for decay heat at time of recirculation) with 15 gm/FA including chemical effects
- STP strainer penetration testing shows that for all CLB, << 15gm/FA accumulates on the core
- Shows there is no CLB with potential for in-core debris effects, independent of T-H analysis
- Confirms that all risk-informed debris effects scope is due to blockage at the strainer 9
Specific Focus Items
- Breaks that have bounding debris transport fractions do not have direct spill paths to the containment floor
- Transport evaluation included 1, 2, and 3 trains operating
- Transport metrics from NUREG/CR 6772, NUREG/CR 6808, and Stokes Law were applied.
- Evaluation of transport of unqualified epoxy, particulate, and chips shows sufficient margin
- Erosion Methodology
- STP conditions are bounded by 30-day erosion testing showing factors below 10%
- Methodology shown in Table 10 of Att. 1-2 of 8/20/15 letter
- Early or late arrival is based on initial blow-down to pool or wash down by spray
- Small and large percentage are the eroded fractions from small and large debris
- Early and late arrival of fines based on initial blow-down to pool or wash down by spray
- Margin evaluation of July 2008 test shows that low density fiberglass is the only debris source term not bounded by the test 10
Debris Test Margin 11 DEBRIS AMOUNTS FOR JULY 2008 TEST Debris Item Debris Amount Test Surrogate Material Comment LDFG Fibers Total Fines 79.91 ft3 / Nukon Not bounding; was based on 7D ZOI Total Smalls 158.48 ft3 / Nukon Particulates Microtherm 33 lbm / Microtherm powder Not bounding; subsequently shown to be 29.3 lbm more Marinite Board 182.7 lbm Powdered Marinite board Bounding; subsequently removed from containment Latent particulate, dust, dirt 141.1 lbm / Dirt mix Bounding Coatings Zinc 1,368 lbm / Tin Powder Bounding; subsequently shown to be 637 lbm less Polyamide primer 10 lbm / Powder (Acrylic coating)
Bounding Alkyds 247 lbm / Powder (Acrylic coating)
Bounding Baked enamel 268 lbm / Powder (Acrylic coating)
Bounding Epoxy (outside ZOI) 106 lbm / Chips (Acrylic 1/64 to 1/4)
Not bounding; subsequently shown to be 259 lbm more Epoxy (ZOI) 57 lbm / Powder (Acrylic coating)
Total powder 1,950 lbm Total chips 106 lbm Chemical Precipitates Sodium Aluminum Silicate 1,432 lbm / WCAP AlOOH Bounding Aluminum Oxyhydroxide 143 lbm / WCAP AlOOH Bounding Calcium Phosphate 359 lbm / WCAP Ca3(PO4)2 Bounding LDFG fines accounted for in the risk-informed portion Microtherm and Epoxy offset by:
Marinite Zinc
Follow-up and Going Forward Actions
- November public meeting to resolve outstanding questions 12