ML080710546
| ML080710546 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 02/29/2008 |
| From: | Mims D C Arizona Public Service Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 102-05819-DCM/GAM/DFS, GL-04-002 | |
| Download: ML080710546 (103) | |
Text
Generic Letter 2004-02 Dwight C. Mims Mail Station 7605 Palo Verde Nuclear Vice President Tel. 623-393-5403 P.O. Box 52034 Generating Station Regulatory Affairs and Plant Improvement Fax 623-393-6077 Phoenix, Arizona 85072-2034 102-05819-DCM/GAM/DFS February 29, 2008 Attn: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Dear Sirs:
Subject:
Palo Verde Nuclear Generating Station (PVNGS)Units 1, 2, and 3 Docket Nos. STN 50-528, 50-529, and 50-530 Supplemental Response to NRC Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors" The U.S. Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 2004-02 on September 13, 2004, to request that addressees perform an evaluation of the emergency core cooling system (ECCS) and containment spray system (CSS)recirculation functions in light of the information provided in the GL and, if appropriate, take additional actions to ensure system function.
Additionally, the GL requested addressees to provide the NRC with a written response in accordance with 10 CFR 50.54(f).
The request was based on identified potential susceptibility of the pressurized water reactor recirculation sump screens to debris blockage during design basis accidents requiring recirculation operation of the ECCS or the CSS and on the potential for additional adverse effects due to debris blockage of flowpaths necessary for ECCS and CSS recirculation and containment drainage.The enclosure to this submittal provides the Arizona Public Service Company (APS)supplemental response to GL 2004-02. This supplement conforms to the NRC's revised content guide for GL 2004-02 supplemental responses in the NRC letter to the Nuclear Energy Institute, dated November 21, 2007. This supplement contains the requested information with the exception of information not available as a result of the extensions approved by the NRC for Unit 2, dated December 13, 2006 (ADAMS Accession No. ML 063400177), and for Units 1, 2, and 3, dated December 27, 2007 (ADAMS Accession No. ML 073531095).
In the December 13, 2006, extension approval letter, the NRC accepted the APS commitment to complete installation of the A member of the STARS (Strategic Teaming and Resource Sharing) Alliance -Callaway 0 Comanche Peak & Diablo Canyon
- Palo Verde 0 South Texas Project 0 Wolf Creek ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Supplemental Response to NRC Generic Letter 2004-02 Page 2 Unit 2 strainer in the Spring 2008 refueling outage. In the December 27, 2007, extension approval letter, the NRC accepted the APS commitment to complete the containment sump strainer confirmatory testing, analysis and validation for PVNGS Units 1, 2 and 3 by June 30, 2008, and to provide the related information from these activities within the following 90 days.Appendix A of the enclosure identifies the location of information provided in the enclosure that addresses the issues identified in the NRC letter to APS, dated February 9, 2006, "Request for Additional Information Re: Response to Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors" (ADAMS Accession No. ML 060390350).
Sections 2.a and 2.b of the enclosure provide a summary of the remaining open issues which will be completed and submitted in accordance with the NRC approved extensions discussed above.There are no new regulatory commitments made in this submittal.
If you have any questions, please contact Glenn A. Michael at (623) 393-5750.I declare under penalty of perjury that the foregoing is true and correct.Executed on Sincerely, DCM/SAB/GAM/gat
Enclosure:
Supplemental Response to GL 2004-02 cc: E. E. Collins Jr. NRC Region IV Regional Administrator M. T. Markley NRC NRR Project Manager G. G. Warnick NRC Senior Resident Inspector for PVNGS Enclosure Supplemental Response to NRC Generic Letter (GL) 2004-02 Supplemental Response to NRC Generic Letter (GL) 2004-02 Arizona Public Service Company Palo Verde Nuclear Generating Station Enclosure Supplemental Response To GL 2004-02 Page i TABLE OF CONTENTS Table of C ontents ................................................................................................................................
i 1.0 COMPLIANCE AND CORRECTIVE ACTIONS .............................................................
3 2.0 General description and schedule for corrective actions ........................................
4 2.a New Strainer C onfiguration
.......................................................................................
4 2.b S chedule of C hanges ................................................................................................
6 3.0 METHODOLOGY TO DEMONSTRATE COMPLIANCE
.......................
9 3.a B reak S election (LO C A ) ...........................................................................................
9 3.a.1 B reak S election C riteria ............................................................................................
9 3.a.2 Secondary Line B reaks ............................................................................................
12 3.a.3 Basis for Limiting Break Size and Location ..............................................................
12 3.b Debris Generation/Zone of Influence (ZOI) (Excluding Coatings)
.............................
13 3.b.1 Methodology for Determination of ZOls ...................................................................
13 3.b.2 Z one of Influence
..................................................................................................
..15 3.b.3 Destruction Testing for Determination of ZOls ........................................................
17 3.b.4 D ebris G eneration
..................................................................................................
..17 3.b.5 Total Surface Area of All Signs, Placards, Tags, Tape, and Similar Miscellaneous Material ...........................................................
19 3.c Debris Characteristics
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.... ... ... ....... * ....... 19 3.c. 1 D ebris S ize C ategorization
.......................................................................................
19 3.c.2 D ensity of D ebris ..................................................................................................
..23 3.c.3 Assumed Specific Surface Areas for Fibrous and Particulate Debris .......................
26 3.c.4 Technical Basis for Debris Characterization Assumptions
....................
26 3 .d L a te nt D e b ris ...............................................................................................................
2 6 3.d.1 Methodology for Latent Debris Evaluation
..............................................................
26 3.d.2 Assumptions Used in Latent Debris Evaluation
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28 3.d.3 Results of Latent Debris Evaluation
........................................................................
28 3.d.4 Sacrificial Strainer Surface Area .............................................................................
29 3 .e D e bris T ra nspo rt ..........................................................................................................
2 9 3.e.1 Methodology Used to Analyze Debris Transport
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29 3.e.2 Debris Transport Assumptions
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I .....................
30 3.e.3 Debris Transport Evaluation
-Computation Fluid Dynamics (CFD) .........................
31 3 .e .4 D ebris Interceptors
................................................................................................
..33 3.e.5 Fine Debris Settlement versus Transport
..................................................................
33 3.e.6 Debris Transported to Sump Strainer .....................................................................
33 3.f Head Loss and Vortex Analysis ..............................................................................
35 3.f. 1 Methodology for Head Loss Determination
.............................................................
39 3.f.2 M inim um Subm ergence ..........................................................................................
40 3.f.3 Proof of Absence of Vortices ..................................................................................
40 3.f.4 Perform ance Tests ..................................................................................................
42 3.f.5 Ability to Accommodate the Maximum Volume of Debris .........................................
47 3.f.6 Ability of the Screen to Resist the Formation of a "Thin Bed" ..................................
47 3.f.7 Basis for the Strainer Design Maximum Head Loss ................................................
47 3.f.8 Strainer Maximum Design Head Loss .....................................................................
48 3.f.9 Strainer Clean Head Loss Calculation
.....................................................................
48 3.f. 10 Debris Head Loss Analysis ........................................
...... 48 Enclosure Supplemental Response To GL 2004-02 Page ii 3.f. 11 C om plete W ater S eal .............................................................................................
48 3.f. 12 N ear Field S ettling ................................................................................................
..48 3.f.13 Temperature/Viscosity Scaling of Head Loss Tests ...............................................
48 3.f. 14 Credit for Containment Accident Pressure in Flashing Evaluation
...........................
48 3.f.15 Absence of Flashing Behind Screen .........
- ..............................................................
49 3.g Net Positive Suction Head (NPSH) ..........................................................................
49 3.g.1 Flow Rates, Sump Temperature, Minimum Containment Water Level .....................
49 3.g.2 NPSH Evaluation Assumptions
...............................................................................
50 3.g.3 Net Positive Suction Head Required (NPSHR) ........................................................
51 3.g.4 Describe How Friction and Other Flow Losses are Accounted
.................................
51 3.g.5 System Response Scenario for LBLOCA and SBLOCAs .........................................
51 3.g.6 Operational Status of ECCS and CSS Pump ...........................................................
53 3.g.7 ECCS Single Failure Assumptions
..........................................................
I ...................
53 3.g.8 Determination of Containment Sump Water Level .................................................
54 3.g.9 Assumptions in Determination of Minimum Water Level for NPSH Margin ...............
54 3.g.10 Empty Spray Pipe, Water Droplets, Condensation and Holdup on Horizontal and V e rtical S urfaces ..................................................................................................
..55 3.g. 11 Assumptions for Equipment that Displace Water in Minimum Water Level D e te rm in a tio n ..............................................................................................................
5 6 3.g. 12 Assumptions for Water Sources to Minimum Water Level Determination
................
57 3.g.13 Containment Pressure for Determination of NPSH .........................
58 3.g.14 Assumptions to Minimize Containment Accident Pressure and Maximize Sump W ate r T e m pe rature ................................................................................................
..58 3.g.15 Containment Accident Pressure at Vapor Pressure Corresponding to the Sump Liq u id T e m pe ratu re ................................................................................................
..58 3 .g .16 N P S H M a rg in ..............................................................................................................
5 8 3.h C oatings Evaluation
................................................................................................
59 3.h.1 C oatings S ystem s ....................................................................................................
..59 3.h.2 Assumptions in Post-LOCA Paint Debris Transport Analysis ..................................
59 3.h.3 Head Loss Testing for Coatings Debris ...................................................................
59 3.h.4 Basis for Surrogate Materials in Head Loss Tests .................................................
60 3.h.5 Coatings Debris Generation
....................................................................................
60 3.h.6 Coatings Debris Characteristics
......................................
61 3.h.7 Coatings Condition Assessment Program ...............................................................
61 3.i D ebris S ource T erm ...............................................................................................
6 1 3.i.1 Programmatic Controls to Limit Debris Sources in Containment
..............................
61 3.i.2 Housekeeping Programmatic Controls ...................................................................
62 3.i.3 Foreign Material Programmatic Controls -Zone III Exclusion Area ........................
62 3.i.4 Programatic Control of Permanent Plant Changes Inside Containment
...................
62 3.i.5 Maintenance Activities Managed in Accordance with Maintenance Rule, 1 0 C F R 5 0 .6 5 ..............................................................................................................
6 3 3.i.6 Insulation Change-Out
....... : ..... .... ..........
...................................
64 3.i.7 Modifications to Reduce Debris .... ; ........................................
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64 3.i.8 Modifications to Equipment or Systems to Reduce Debris .......................................
64 3.i.9 Coatings Program Modifications or Improvements
..................................................
64 3.j Screen Modifications Package .................................................................................
65 3.j.1 Description of Sump Screen Design Modifications
.................................................
65 3.j.2 Other Modifications by the Strainer Replacement
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67 Enclosure Supplemental Response To GL 2004-02 Page iii 3.k Sum p Structural Analysis ..........................................................................................
67 3.k.1 Sum p Strainer Structural Analysis ..........................................................................
67 3.k.2 Fram e Structural Analysis ........................................................................................
70 3.k.3 Seism ic Analysis .....................................................................................................
71 3.k.4 Evaluations Performed for Dynamic Effects such as Pipe Whip ..............................
72 3.k.5 Credit for Backflushing Strategy ..............................................................................
72 3.1 Upstream Effects ....................................................................................................
72 3.1.1 Sum m ary of Upstream Effects Evaluation
..............................................................
72 3.1.2 Evaluation of Flow Paths from Postulated Breaks and Containment Spray W ashdown ..............................................................................................................
- .... 73 3.1.3 M easures Taken to M itigate Potential Choke Points .................................................
75 3.1.4 Evaluation of Water Holdup at Installed Curbs or Debris Interceptors
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75 3.1.5 Potential Blockage of Reactor Cavity and Refueling Cavity Drain ............................
75 3.m Downstream Effects -Com ponents and System s ....................................................
76 3.m .1 Com ponents ................................................................................................................
76 3.m .2 Verification that Com ponents are not Susceptible to Plugging ..............................
I ...... 77 3.m.3 Summary and Conclusions of Downstream Evaluations
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79 3.m .4 Sum m ary of Design and/or O perational Changes ....................................................
79 3.n Downstream Effects -Fuel and Vessel ...................................................................
80 3.n. 1 Reactor Vessel Internals
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80 3.n.2 Nuclear Fuel .....................................................................................
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80 3.o Chem ical Effects ..........................................................................................................
80 3.o.1 Head Loss Results ..................................................................................................
80 3.0.2 Content G uide for Chem ical Effects ........................................................................
80 3.p Licensing Basis ......................................................................................................
87 3.p.1 General Description of Changes ..............................................................................
87
4.0 REFERENCES
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88 5.0 APPENDICES
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93 Enclosure Supplemental Response to GL 2004-02 Page 1 NOTES ON FORMAT AND CONTENT In this supplemental response to Generic Letter (GL) 2004-02, Arizona Public Service (APS)followed the standardized format provided by the Nuclear Regulatory Commission (NRC) to the Nuclear Energy Institute (NEI) in a letter dated November 21, 2007. Any exceptions to NEI 04-07 (Reference 4.30) or the NRC Safety Evaluation (SE) (Reference 4.28) are clearly identified.
In this document each major section describes the evaluations and other corrective actions that impact conformance to the regulatory guidance listed in GL 2004-02. Each section also includes the basis for methods and key assumptions.
EXECUTIVE
SUMMARY
Arizona Public Service Company (APS) is resolving issues described in GL 2004-02 by using the guidance and requirements of NEI 04-07 (Reference 4.30) and the associated NRC Safety Evaluation (SE) (Reference 4.28), as well as industry guidance, industry testing and plant-specific testing. A comprehensive set of evaluations were performed of the effects of design basis accident conditions on the ability of structures, systems and components, to mitigate the consequences of analyzed accidents and to maintain long term core cooling in a manner consistent with governing regulatory requirements listed in GL 2004-02.New sump strainers have been installed at the existing emergency recirculation sump pits in Units 1 and 3 to accommodate the water levels postulated for post-accident conditions.
Strainers will be installed in Unit 2 in the Spring 2008 refueling outage to begin no later than April 28, 2008. Each new sump strainer contains strainer modules with an integral trash rack and pockets that maximize the strainer surface area. The -strainer pockets have perforated stainless steel plate surfaces with 0.083" nominal diameter holes to capture debris. While the original containment recirculation sump screens and trash racks had approximately 210 ft 2 of effective surface area per sump, the new replacement sump strainers have approximately 3,142 ft 2 of effective surface area per sump.APS has removed the Fiberfrax insulation from containment which was a significant debris source. PVNGS uses reflective metal insulation as the primary insulation for the nuclear steam supply piping and vessels.APS has implemented changes in programs and procedures to ensure and/or enhance the control of transportable debris (e.g., insulation, signs, and foreign materials) within the containment building in all 3 units.Interim compensatory measures have been implemented at PVNGS in accordance with NRC Bulletin 2003-01, "Potential Impact of Debris Blockage on Emergency Recirculation at Pressurized Water Reactor," as described in APS letter Nos. 102-05236, dated March 25, 2005, and 102-05335, dated August 30, 2005.This supplemental response contains currently available design basis information for the PVNGS strainers.
As discussed below, following completion of the confirmatory testing and validation, the supplemental report will be updated and resubmitted.
As a product of the Enclosure Supplemental Response to GL 2004-02 Page 2 completion of the confirmatory and validation activities the update to the supplemental report will identify the confirmed conservatisms and margins in the design.The following commitments and extensions have been approved by the NRC for PVNGS Unit 2 (ADAMS Accession No. ML 063400177) and for Units 1, 2, and 3 (ADAMS Accession No.ML 073531095):
- Install larger sump strainers in PVNGS Unit 2 Scheduled Completion Date: 2R14 refueling outage (to begin no later than April 28, 2008)* Complete the containment sump strainer confirmatory testing, analysis and validation for Units 1, 2, and 3 by June 30, 2008.Scheduled Completion Date: June 30, 2008* Submit the information from containment sump strainer confirmatory testing, analysis and validation for PVNGS Units 1, 2, and 3 within 90 days of their completion.
Scheduled Completion Date: September 28, 2008 Enclosure Supplemental Response to GL 2004-02 Page 3 1.0 COMPLIANCE AND CORRECTIVE ACTIONS The containment sump strainers in PVNGS Units 1 and 3 have been replaced under Design Modification Work Order (DMWO) 2822654 per commitments to the NRC as documented in APS Letter 102-05336, dated September 1, 2005. The Unit 1 sump strainers were replaced in the Spring 2007 refueling outage and the Unit 3 sump strainers were replaced in the Fall 2007 refueling outage. The sump strainers in PVNGS Unit 2 will be replaced in Spring 2008 as part of refueling outage 2R14 to begin no later than April 28, 2008. The modification was deemed necessary based on evaluations requested by GL 2004-02 and performed in accordance with the guidance in NEI 04-07, "Pressurized Water Reactor Sump Performance Evaluation Methodology" (Reference 4.30) and the associated NRC Safety Evaluation (SE)(Reference 4.28). The new sump strainers have been procured from Control Components, Inc. (CCI) per PVNGS Specification 13-MN-1003 (Reference 4.31).The new design increases the screen size from approximately 210 ft 2 to 3,142 ft 2 per sump (Reference 4.25), which will provide sufficient area to assure Emergency Core Cooling System (ECCS) and Containment Spray System (CSS) performance by accommodating any strainer blockage that is postulated to occur following a LOCA.This conclusion is based on the preliminary results of the CCI strainer testing head loss analysis.
This analysis will be finalized prior to June 30, 2008. DMWO 2822654 also removed, from all three units, the Fiberfrax insulation from piping penetrations in the bioshield (S/G D-ring) and Pressurizer shield walls which reduced the amount of transportable debris in the Containment.
The Fiberfrax penetration seals have been replaced with stainless steel sheet metal barriers to meet penetration isolation requirements.
New sump strainers are installed in the same location as the existing strainers and located on the containment floor directly over the sump pits. The new strainers incorporate diverse geometry in the design, which promotes uneven debris distribution and reduced head loss. The strainers are of modular construction which can be enlarged if needed, and are constructed of perforated stainless steel plate.The new strainers provide approximately 3,142 ft 2 of strainer surface area per sump with holes with a nominal diameter of 0.083". The new strainers do not utilize gaskets or soft sealants.In each PVNGS Unit, the suction supply for the ECCS and CSS pumps during recirculation following a Loss of Coolant Accident (LOCA) is provided by two containment emergency sumps, one for each safety-related train. The sumps are located on the lowest floor in the Containment Building and are physically separated to preclude simultaneous damage to both screens.Calculation 13-MC-SI-0309 (Reference 4.49) which evaluates the performance during post-accident scenarios of the original containment emergency sump strainers under the original licensing basis will be replaced with a new strainer head loss analysis from the sump strainer manufacturer.
Calculation 13-MC-SI-0309 (Reference 4.49) determined the maximum head loss across the screen as a result Enclosure Supplemental Response to GL 2004-02 Page 4 of estimated screen blockage in accordance with RG 1.82, Revision 0 requirements (50 percent screen blockage).
Calculations 13-MC-SI-0017 (Reference 4.32) and 13-MC-SI-0018 (Reference 4.33) verified adequate available Net Positive Suction Head (NPSH) for the ECCS and CSS pumps, respectively, based on the calculated screen head loss. The two NPSH calculations will be revised, with new head loss data for the replacement containment emergency sump strainers, upon completion of the new strainer head loss analysis.
The completion of the NPSH and head loss calculation will be prior to the PVNGS GL 2004-02 extension date of June 30, 2008., This response summarizes the technical basis for the Palo Verde design and procedural controls to satisfy the commitments relative to GL 2004-02. The new sump strainer design is in compliance with NRC guidance for determining the susceptibility of pressurized water reactor (PWR) recirculation sump screens due to the adverse effects of debris blockage during design basis accidents that require recirculation operation of the ECCS and CSS.2.0 GENERAL DESCRIPTION AND SCHEDULE FOR CORRECTIVE ACTIONS 2.a New Strainer Configuration As discussed above, APS has installed new containment sump strainers in PVNGS Units 1 and 3, and will install new strainers in Unit 2 in Spring 2008, to increase the effective screen area to 3,142 ft 2 per sump. To accomplish this, the existing screens and steel "roof" are removed. The existing vertical W6x25 columns are shortened and circumscribing beams are removed. A new stainless steel floor is attached to the existing structural steel base frame to cover the sumps at the 80'-7" level. This floor is supported by new stainless floor joists. The floor has eight large flow slots to accept flow from eight new strainer modules mounted on the new floor. Each module has flow coming from two of four sides but not the top of the module. Both sides consist of arrays of rectangular pockets. Each rectangular pocket is approximately 3" wide by 5" high by 16" deep. Flow enters each 3"x5" opening and is filtered through perforated plate on the other five sides. The nominal diameter of the holes is 0.083". Stainless steel sheet metal is used to form the modules. The flows from the two arrays of pockets meet in a plenum in the middle of the module and then flow down through the slot in the floor to the sump and then to the pumps located in the Auxiliary Building.To reduce the potential quantity of fibrous debris in containment, Fiberfrax was removed from containment in all three units. The piping penetrations in the containment bioshield walls were originally sealed with Fiberfrax.
These penetrations have been modified to remove the Fiberfrax and install stainless steel sheet metal barriers in the piping penetrations.
The existing sump temperature element was relocated to facilitate the installation of the replacement sump strainers.
The relocation of the temperature element did not Enclosure Supplemental Response to GL 2004-02 Page 5 change the design requirements of the instrument, only a physical re-location to accommodate the position of the penetration for the temperature element conduit.As described in Section 3.i, procedural controls are in place to verify containment cleanliness prior to containment closure following any entry or refueling outage to ensure that the areas affected by the containment entry are free of loose debris which can be transported to the containment emergency sump strainers.
Procedures provide control of transient materials taken into containment.
The description of the configuration of the replacement containment emergency sump strainers has been added to the PVNGS UFSAR with Licensing Document Change Request (LDCR) 06-F036.Documents generated or revised to support the GL 2004-02 response are listed below: Debris Generation Calculation (Reference 4.4)Debris Transport Calculation (Reference 4.14)Minimum Containment Flood Level Calculation (Reference 4.15)Latent Debris Calculation (Reference 4.13)Strainer Structural/
Seismic Analysis (References 4.22, 4.23, 4.24, 4.44)Post-LOCA Chemical Effects Analysis (Reference 4.16)Post-LOCA Fuel Deposition Analysis (Reference 4.60)Pump Seal Evaluation (Reference 4.45)Pump Seal Cyclone Separator Evaluation (Reference 4.61)Foreign Material Walkdown Reports (References 4.2, 4.5, 4.6)Procedure Revision for Containment Cleanliness (Reference 4.39)Downstream Effects Evaluations, per WCAP 16406, Revision 0 (References 4.56, 4.77)To meet the APS commitments approved by the NRC in the December 27, 2007, extension approval letter, the following in-process documents are scheduled for completion prior to June 30, 2008: Final Chemical Effects Test Report Strainer Head Loss Calculation NPSH Calculations Downstream Effects Evaluations, per WCAP 16406, Revision 1 with Safety Evaluation (SE)
Enclosure Supplemental Response to GL 2004-02 Page 6 2.b Schedule of Changes A description of and implementation schedule for the committed corrective actions that were identified while responding to GL 2004-02 is provided below. The corrective actions listed are more fully described in responses to items 2.c, 2.d, and 2.f.The description of and implementation schedule for GL 2004-02 Corrective Actions is as follows:
Enclosure Supplemental Response to GL 2004-02 Page 7 GL 2004-02 REGULATORY COMMITMENT LATEST PREVIOUS REVISED DUE (from APS Letter No. 102-05560 DUE DATE DATE or STATUS dated August 30, 2006)1 Evaluate the recommendations contained in December 31, 2005 Completed the Westinghouse downstream effects evaluation for PVNGS and establish an implementation schedule for appropriate recommendations. (RCTSAI 2826236)2. Perform confirmatory head-loss testing of June 30, 2008 approved No Change new strainer with plant specific debris to in NRC letter dated ensure an adequate design. (RCTSAI December 27, 2007 2826244) (ADAMS Accession No.ML 073531095)
- 3. Verify that a capture ratio of 97% or higher June 30, 2008 approved No Change can be achieved in the final design of the in NRC letter dated new sump screen to ensure that the fuel December 27, 2007 evaluation contained in the Westinghouse (ADAMS Accession No.downstream effects evaluation is bounding.
ML 073531095)(RCTSAI 2826247)4. Perform sump strainer structural evaluation October 31, 2006 Completed to ensure seismic and operational integrity.(RCTSAI 2826250)5. Validate allocated margins for Chemical June 30, 2008 approved No Change Effects in strainer head-loss to ensure an in NRC letter dated adequate design. (RCTSAI 2826239) December 27, 2007 (ADAMS Accession No.ML 073531095)
- 6. Perform a confirmatory containment latent June 30, 2006 Completed debris walkdown of PVNGS Units 1 and 3.(RCTSAI 2826259)[Note: The containment walkdown for transportable debris was completed in Unit 2 as stated in Letter No. 102-05336, 9/1/05.]7. Perform a confirmatory containment June 30, 2006 Completed unqualified coating walkdown of PVNGS Units 1 and 3. (RCTSAI 2826260)[Note: The containment walkdown for transportable debris was completed in Unit 2 as stated in Letter No. 102-05336, 9/1/05.]
Enclosure Supplemental Response to GL 2004-02 Page 8 GL 2004-02 REGULATORY COMMITMENT LATEST PREVIOUS REVISED DUE (from APS Letter No. 102-05560 DUE DATE DATE or STATUS dated August 30, 2006)8. Review the existing programmatic controls November 30, 2006 Completed for containment coatings identified in the response to GL 98-04, "Potential for Degradation of the Emergency Core Cooling System and the Containment Spray System after a Loss-of-Coolant Accident Because of Construction and Protective Coating Deficiencies and Foreign Material in Containment," for their adequacy.(RCTSAI 2826262)9. Review the existing programmatic and November 30, 2006 Completed procedural controls in place to prevent potentially transportable debris (insulation, signs and foreign material) in the containment building to ensure that the bounding assumptions in the design of the new strainers will be maintained.(RCTSAI 2826263)10. Implement in Unit 1 changes to programs 1R13 refueling outage Completed and procedures to ensure and/or enhance (approximately the control of transportable debris in May 31, 2007)containment. (RCTSAI 2826264)11. Implement in Unit 2 changes to programs 2R13 refueling outage Completed and procedures to ensure and/or enhance (approximately the control of transportable debris in November 30, 2006)containment. (RCTSAI 2826267)12. Implement in Unit 3 changes to programs 3R13 refueling outage Completed and procedures to ensure and/or enhance (approximately the control of transportable debris in December 31, 2007)containment. (RCTSAI 2826269)13. Install larger sump strainers in PVNGS 1 R1 3 refueling outage Completed Unit 1. (RCTSAI 2826277) (approximately May 31, 2007)14. Install larger sump strainers in PVNGS 2R14 refueling outage No Change Unit 2. (RCTSAI 2826278) (to begin no later than April 28, 2008), approved in NRC letter dated December 13, 2006 (ADAMS Accession No. ML 063400177)
Enclosure Supplemental Response to GL 2004-02 Page 9 GL 2004-02 REGULATORY COMMITMENT LATEST PREVIOUS REVISED DUE (from APS Letter No. 102-05560 DUE DATE DATE or STATUS dated August 30, 2006)15. Install larger sump strainers in PVNGS 3R13 refueling outage Completed Unit 3. (RCTSAI 2826284) (approximately December 31, 2007)16. Remove installed Fiberfrax insulation in 1 R1 3 refueling outage Completed PVNGS Unit 1. (RCTSAI 2826282) (approximately May 31, 2007)17. Remove installed Fiberfrax insulation in 2R13 refueling outage Completed PVNGS Unit 2. (RCTSAI 2826283) (approximately November 30, 2006)18. Remove installed Fiberfrax insulation in 3R13 refueling outage Completed PVNGS Unit 3. (RCTSAI 2826284) (approximately December 31, 2007)19. After plant specific strainer testing has been To be submitted along This item is closed completed and the Westinghouse with the NRC RAI to new downstream effects evaluation for PVNGS response as soon in Commitments
- 20 has been evaluated, APS will submit an 2007 as the results are and #21 update to the NRC to report the validation available, and no later of the allocated margins for chemical than December 31, 2007 effects and identify any recommendations from the Westinghouse evaluation to be implemented. (RCTSAI 2826287)20. Contingent on NRC approval, APS commits June 30, 2008 approved No Change to complete the containment sump strainer in NRC letter dated confirmatory testing, analysis and validation December 27, 2007 for PVNGS Units 1, 2 and 3 by June 30, (ADAMS Accession No.2008. (RCTSAI 3106850) ML 073531095)
- 21. Submit the information from containment September 28, 2008, No'Change sump strainer confirmatory testing, analysis 2008 approved in NRC and validation for PVNGS Units 1, 2 and 3 letter dated December within 90 days of their completion (this will 27, 2007 (ADAMS provide information not submitted with the Accession No. ML GL 2004-02 supplemental response due by 073531095)
February 29, 2008). (RCTSAI 3106852)3.0 3.a METHODOLOGY TO DEMONSTRATE COMPLIANCE Break Selection (LOCA)Break Selection Criteria The "limiting" break is identified as the break that results in the type, quantity, and mix of debris generation that is determined to produce the maximum head loss Enclosure Supplemental Response to GL 2004-02 Page 10 across the sump screen. The debris types and mix were reviewed with the possible break locations and break sizes to determine several possible limiting break locations (Reference 4.4). The break selection process is described in the Methodology in Section 3.3.4 of NEI 04-07 (Reference 4.30) and the associated NRC SE (Reference 4.28).The largest lines in containment are as follows: Hot Leg (42-inch ID), Cold Leg Suction (30-inch ID), Cold Leg Discharge (30-inch ID), Main Steam (28-inch), Feedwater (24-inch), Shutdown Cooling from Reactor Coolant System (RCS)(16-inch ID), Safety Injection (SI) and Shutdown Cooling (SDC) to RCS (14-inch), and Pressurizer Surge Line (12-inch).
Recirculation is not required for Feedwater line breaks and Main Steam line breaks.Therefore, breaks in the Main Steam and Feedwater lines do not have to be analyzed.
Since the SI and SDC injection and discharge lines are located within the Steam Generator (S/G) D-ring walls, and are of smaller diameter than the RCS piping, these line breaks would be bounded by the hot leg break and thus are not analyzed.
Likewise, the Pressurizer spray lines located within the S/G D-ring and Pressurizer walls are bounded by larger line breaks in these areas. Hence, breaks in the hot and cold legs and the Pressurizer surge line are considered.
It is noted that Section 3.3.5.2 of the NRC SE (Reference 4.28) describes a systematic approach to break selection along individual piping runs that starts at an initial location along a pipe, generally a terminal end, and steps along in equal (5-ft.)increments, placing breaks at each sequential location.
The staff notes in the SE that the concept of equal increments is only a reminder to be systematic and thorough.
Section 3.3.5.2 of the SE goes on to say that the key difference between many breaks (especially large breaks) will not be the exact location along the pipe, but rather the envelope of Containment material targets that is affected.
At PVNGS, the exact break location along the pipe is not critical.
This is because the envelope of affected Containment material targets is defined by the S/G D-ring or Pressurizer enclosure, and nearly all Reflective Metal Insulation (RMI) in the S/G D-ring and Pressurizer enclosure is within the Zone Of Influence (ZOI) for a break in the corresponding location based on the large ZOI radius for mirror insulation.
Section 3.a.3 provides the basis for break selection that could cause the most debris and that could be transported in the most direct path. As provided in the general guidance of NEI 04-07, break exclusion zones were disregarded and all piping locations were considered.
NRC Branch Technical Position (BTP) MEB 3-1 was not used as a basis for determining potential LOCA break locations.
The location of breaks is shown in Figure 1.
Enclosure Supplemental Response to GL 2004-02 Page 11-NTS-: CoWT~nat-2 Eys~em' U5Ge1 In AtaChM1mr 8.4 OT MI~fS cUlalc~an.
FIGURE 1 -Break Locations Enclosure Supplemental Response to GL 2004-02 Page 12 In summary, the following four postulated breaks have been analyzed (Reference 4.4): Table 1 -Postulated Break Locations Break Break North- East-Name Location ID(2) Elevation South West Enclosure Location(')
Location(')
S-1 S/G 2 hot leg (063-42")
piping 42" 101.33' 28.5' south 1' east South S/G at the S/G D-Ring nozzle S-2 Loop 2A cold leg suction (E-073-30")
South S/G piping at the 30" 92.61' 28.5' south 18.36' east D-Ring Reactor Coolant Pump (RCP)nozzle S-3 Loop 2B cold leg suction 16.36' South S/G (E-084-30")
30" 92.61' 28.5' south west D-Ring piping at the RCP nozzle S-4 Surge line (E-028-BCAA-40.21'12") piping at 12" 110.42' 26.3' north west Pressurizer the Pressurizer nozzle (1) North-South and East-West locations are in reference to the containment Building center.(2) Nominal pipe diameter.3.a.2 Secondary Line Breaks Recirculation is not required for Feedwater line breaks and Main Steam line breaks.Thus, these breaks were not analyzed.
Since the SI and SDC injection and discharge lines are located within the S/G D-ring walls and are of smaller diameter than the RCS piping, these line breaks are bounded by the hot leg break. Thus, these breaks were not specifically analyzed.Basis for Limitinq Break Size and Location The hot leg is the largest line (42-inch ID) within the S/G cavity and would produce the largest ZOI. A break at the S/G nozzle will capture the most insulation debris. A break at this location also impacts coatings on sections of all S/G cavity walls, and 3.a.3 Enclosure Supplemental Response to GL 2004-02 Page 13 captures the most particulate debris. Since the south S/G D-ring is closest to the recirculation sumps, a break at the S/G 2 hot leg nozzle was analyzed.
The cold legs have a smaller diameter than the hot leg, hence producing a smaller ZOI.However, because of the location of the cold leg suction lines relative to the S/G pedestal and the S/G D-ring entrance/exit path at El. 80', water and debris from a break in the line from S/G 2 to RCP 2A or 2B would flow to only the east side (RCP 2A) or the west side (RCP 2B) of Containment.
The flow path from each of these locations to the containment emergency sumps is slightly different in terms of obstructions on El. 80'. Therefore, both of these break locations were analyzed since either could result in the transport of the largest quantity of debris to the containment emergency sumps. Small bore piping breaks were not specifically evaluated because they are not bounding.The Pressurizer is located in its own enclosure adjacent to the north S/G D-ring.Postulated breaks at this location would be bounded by hot and cold leg breaks in the S/G D-ring in terms of RMI debris quantity.
However, there is the potential for a greater quantity of fiber insulation debris since the Pressurizer enclosure includes Nukon and Temp-Mat insulation that would become debris. Based on this, a break at the Pressurizer surge line nozzle was analyzed.3.b Debris Generation/Zone of Influence (ZOI) (Excluding Coatings)3.b.1 Methodology for Determination of ZOls An analysis was performed (Reference 4.4) that determines the amount of debris generated in a Loss of Coolant Accident (LOCA) that will maximize the head loss across the containment emergency sump screen during recirculation for PVNGS Units 1, 2, and 3. The evaluation followed the guidance provided in NEI Baseline Methodology (NEI 04-07) and the associated SE. The NEI methodology was developed with the intent that all PWR owners would perform the evaluations in a consistent manner. The guidance of NEI 04-07 was used for the PVNGS evaluations.
There are three basic steps in determining the debris generated as defined by the NEI Methodology and the SE:* Break selection* Identify the ZOI for the break a Quantify the debris by type Debris generation was postulated at four different break locations which bound all other locations for debris generation that could be transported to the sumps. Breaks at the main steam and feedwater lines were not considered because recirculation is not needed in those instances.
Enclosure Supplemental Response to GL 2004-02 Page 14 The amount of debris generation was evaluated based on the Zone of Influence method whereby the radius of this ZOI was based on multiples of the diameter of the pipe where the break occurs (r/D). These values of r/D are in compliance with the SE of NEI 04-07 for the various types of insulation, etc. in the vicinity of the break.Conservative assumptions were made in grouping insulation types for small quantities (e.g., Alpha cloth).Coatings on steel, concrete and equipment in containment are also evaluated.
Qualified coatings at PVNGS for concrete are epoxy coatings which are evaluated for a 4.0 D ZOI based upon the results of testing presented in WCAP-16568-P (Reference 4.54). Qualified coatings for steel are inorganic zinc coatings which are evaluated for a 5.0 D ZOI based on Reference 4.54. Unqualified coatings are considered to be debris consistent with NEI 04-07 and its associated SE. Further discussion of coatings is contained in Section 3.h of this response submittal.
In accordance with NEI 04-07, all insulation material, paint, and other attached material within the ZOI was considered to be generated as debris.The cleanliness of containment and presence of foreign material, latent material, and the like that could dislodge and become debris under LOCA conditions was considered in the debris generation evaluation.
Such material is minimized to the greatest extent practical and is controlled by procedures (Reference 4.39, 4.40).Containment cleanliness is verified at the end of each outage prior to establishing containment integrity.
A latent debris walkdown was performed in each unit to confirm that the latent debris quantity used for sump strainer sizing is bounding.Other debris generation modes such as containment spray and submergence were considered, e.g., all unqualified coatings are assumed to fail and become debris.Turbulence induced debris generation phenomenon was considered but generally is not applicable because practically all insulation is jacketed in containment.
The velocities and location of this cascading water is not sufficient to cause debris generation.
Section 3.3.5.2 of the NEI 04-07 and the associated NRC SE describes a systematic approach to break selection along individual piping runs that starts at an initial location along a pipe, generally a terminal end, and steps along in equal (5-ft.)increments, placing breaks at each sequential location.
The staff notes in the SE that the concept of equal increments is only a reminder to be systematic and thorough.
Section 3.3.5.2 of the SE goes on to say that the key difference between many breaks (especially large breaks) will not be the exact location along the pipe, but rather the envelope of containment material targets that is affected.
At PVNGS, the exact break location along the pipe is not critical.
This is because the envelope of affected containment material targets is defined by the S/G D-ring or Pressurizer enclosure and nearly all RMI insulation in the S/G D-ring and Pressurizer enclosure is within the ZOI for a break in the corresponding location based on the large ZOI radius for RMI.
Enclosure Supplemental Response to GL 2004-02 Page 15 3.b.2 Zone of Influence Reference
4.4 documents
that the following types of insulation are located within the S/G D-ring and Pressurizer enclosures, which is where the analyzed breaks are postulated to occur.Table 2 shows ZOI Radii for qualified coatings and insulation materials (from NEI 04-07, Table 3-2 and 3.4.2.2).Table 2 -NEI 04-07 Zone of Influence Insulation/Coating ZOI Radius/Break Diameter (R/D)Protective coatings (Qualified) 10 Transco RMI 2.0 Min-K Mirror with standard bands 28.6 Temp-Mat with stainless steel wire retainer 11.7 Unjacketed Nukon 17.0 The following ZOI radius for various debris types in the PVNGS Units 1, 2 & 3 containments were used in the debris generation analysis (Reference 4.4): Table 3 -PVNGS Zone of Influence Radius/Diameter Insulation/Coating 1 ZOI Radius/Break Diameter (R/D)Piping RMI (Mirror and Transco RMI) 28.6 Equipment RMI (Transco RMI) 2.0 Nukon 17.0 Temp-Mat 11.7 Thermo-lag 17.0 (1)Qualified Coatings -Epoxy 4.0 Qualified Coatings -Inorganic Zinc 5.0 Unqualified Coatings and Damaged Qualified All assumed to fail Coatings I (1) There is no information in the NEI or NRC documents (References 4.28 and 4.30)regarding the ZOI for Thermo-lag 330. Analysis assumed that the ZOI for this material was equal to that of unjacketed Nukon (17.0 D). This is reasonable since the insulation is a robust particulate material with fiber binders and therefore would have a higher destruction pressure than Nukon.
Enclosure Supplemental Response to GL 2004-02 Page 16 The types of insulation present within the containments are as follows (Reference 4.4): Table 4 -Insulation Type and Location Insulation Type Equipment/Location Stainless Steel Reflective Metal Steam Generators (S/G), primary and Insulation (RMI) -Transco RMI secondary piping connections to S/Gs, Reactor Head, Reactor Coolant Pumps (RCP), Reactor Coolant System (RCS)piping Diamond Power Stainless Steel Safety Injection (SI), Shutdown Cooling Mirror Insulation (SDC), and Chemical & Volume Control (CH) system piping at RCS; Pressurizer spray and surge line piping; Main Steam, Feedwater, Auxiliary Feedwater, and S/G Blowdown piping at S/G; instrument and sample lines at RCS and S/G Microtherm
/ Min-K (encapsulated)
Located on Reactor Vessel Head underneath RMI insulation and is shielded from containment spray Transco Temp-Mat with SS Inner Pressurizer (at keyway locations) and Outer Skin (encapsulated)
Nukon (under RMI) Top of Pressurizer Unjacketed Nukon Pressurizer spray, Feedwater, and S/G Blowdown lines at piping supports Temp-Mat Pressurizer
("field packed" at isolated locations)
Thermo-Lag Electrical raceways and equipment Alpha-Cloth Instrumentation penetrations in north S/G D-ring Anti-Sweat (jacketed)
Chilled water lines outside S/G D-rings and Pressurizer enclosure Per Reference 4.4, the Transco RMI layers of foil per inch of insulation.
insulation on the Pressurizer contains three (3)Transco RMI is essentially the same as Mirror insulation except that Transco RMI has more robust securing bands, giving it a small break ZOI (2.0 D from NEI 04-07, Table 3-2). However, for the PVNGS evaluation all Transco RMI on piping was conservatively modeled as Mirror insulation (28.6 D). For Transco RMI installed on equipment, a ZOI of 2.0 D was used, consistent with NEI 04-07, Table 3-2.
Enclosure Supplemental Response to GL 2004-02 Page 17 Since information for Thermo-lag was not specifically provided in NEI 04-07, it was assumed that the ZOI for these materials was equal to that of unjacketed Nukon (17.OD). The basis for this is the Thermo-lag insulation is fibrous material, and the ZOI for Nukon is in the upper range of tested insulation materials.
This is reasonable since the insulation is a robust particulate material with fiber binders and therefore would have a higher destruction pressure than Nukon.Reference 4.4 also documents that there are various types of coatings within containment.
Coatings are classified as qualified or unqualified.
Qualified coatings are defined as coatings that will remain in place under Design Basis Accident (DBA)conditions.
These coatings, if in good condition, will become debris only in the ZOI.A ZOI radius of 4.0 D for qualified epoxy coatings and 5.0 D for qualified inorganic zinc coatings is used. These values are based on jet impingement testing to determine ZOI for qualified coatings (WCAP-16568-P, Referenrce 4.54)3.b.3 Destruction Testinq for Determination of ZOls WCAP-16568-P (Reference 4.54) has been used for determination of ZOls for qualified coatings.3.b.4 Debris Generation The total quantity of debris generated for the four postulated LOCA Breaks (Sl-S4)is given in Section 6.2.1 of Calculation 2005-06160 (Ref. 4.4) and is repeated in Table 5 below. These debris quantities are applicable to PVNGS Units 1, 2 and 3.
Enclosure Supplemental Response to GL 2004-02 Page 18 Table 5 -Total Debris Generated Debris Type ] Units Break S1 Break S2 Break S3 Break S4 INSULATION Mirror Foil -Within ZOI [ftz] 23,827 23,827 23,827 11,337 Transco RMI Foil -Within ZOI [ft'] 30,338 23,464 23,464 432 Nukon -Within ZOI 4) [ftJ] 13.38 13.38 13.38 12.59 Temp-Mat -Within ZOI [ft 0 0 0 0.15 Fiberfrax
-Within ZOI) [ft 1 0 0 0 0 Thermo-lag 330 -Within ZOI 3.53 3.53 3.53 2.39 Alpha-cloth
-CSS Generated
[ft] 0.1 0.1 0.1 0.1 QUALIFIED COATINGSt' i" Steel Coatings (IOZ) [ft"] 2.2 2.2 2.2 2.2 Concrete Wall Coatings (Epoxy) [ft 0.1 0.1 0.1 0.1 Concrete Floor Coatings (Epoxy) [Wti 1.8 1.8 1.8 1.8 DAMAGED COATINGS (IOZ) [ft] 0.01 0.01 0.01 0.01 UNQUALIFIED COATINGSt 1'Failure Mode Elim Blockage [ft 3] 0.36 0.36 0.36 0.36 Concern"R" Class Inorganic Zinc [W 0.12 0.12 0.12 0.12 Indeterminant Coatings [ft"] 0.55 0.55 0.55 0.55 Totals After May 1997 -Zinc [ft" 0.67 0.67 0.67 0.67 Totals After May 1997 -Epoxy ftL 0.32 0.32 0.32 0.32 Epoxy Floors [ft] 2.0 2.0 2.0 2.0 Epoxy Touchup [ftA 0.03 0.03 0.03 0.03 Zinc Primer/Cold Galvanizing
[ftl 0.13 0.13 0.13 0.13 High Temperature Aluminum t 1.02 1.02 1.02 1.02 Alkyd Enamel [ft] 0.25 0.25 0.25 0.25 LATENT DEBRIS [Ibm] 119.21 119.21 119.21 119.21 FOREIGN MATERIALS Duct Tape [ftz] 0.56 0.56 0.56 0.56 Glass Lighting [ftz] 139.2 139.2 139.2 139.2 Ty-Wraps [ft] 0.45 0.45 0.45 0.45 Foil Labels [ftL] 2.24 2.24 2.24 2.24 Metal Labels kL 41.63 41.63 41.63 41.63 Paper Labels [ft 1 17.78 17.78 17.78 17.78 Plastic Labels [W] 181.14 181.14 181.14 181.14 Velcro Labels [ft'] 0.55 0.55 0.55 0.55 (1)Da~lseU on1 bundinUIg coatingIl lSYStLll kali::nIIUII L"ICIUnIs:s) of coaings.Il.
(2) DMWO 2822654 removed the Fiberfrax from the PVNGS Unit 1, 2, and 3 Containments.
(3) Based on break ZOI of 5.0 D for steel coatings and 4.0 D for concrete coatings, design basis case, consistent with WCAP-1 6568-P (Reference 4.54) recommendations.
Break S1 is the bounding case for qualified coatings debris. This bounding case is applied to all break cases for qualified coating debris.(4) Upon removal of the Nukon from the letdown delay coils per DMWO 2822654 in Unit 2, the bounding value of Nukon in any of the three units in either the North S/G D-Ring or South S/G D-Ring is 9.82 ft 3.Therefore, for breaks S1, S2, and S3, the quantity of Nukon will decrease from 13.38 ft 3 to 9.82 ft 3.Note: Nukon was never installed on the delay coils in Unit 1 and has already been removed from Unit 3.
Enclosure Supplemental Response to GL 2004-02 Page 19 3.b.5 Total Surface Area of All Signs, Placards, Tags, Tape, and Similar Miscellaneous Material The total surface area of foreign material such as signs, labels, tags, tape, etc. is based on a walkdown and statistical sampling of the Unit 2 containment.
Unit 2 is representative of Units 1 and 3 based on the typical design similarities between PVNGS containments.
In addition, the plant labeling procedures are the same for all PVNGS units. The total quantity of foreign material based on walkdown is tabulated in Table 6. (Reference 4.4)Table 6 -Foreign Materials FOREIGN MATERIALS Units Quantity Duct Tape [ft 2] 0.56 Glass Lighting Ift ] 139.21 Ty-Wraps [ft 0.45 Foil Labels [ft2] 2.24 Metal Labels [ft2] 41.63 Paper Labels [ft ] 17.78 Plastic Labels ft 181.14 Velcro Labels [ft 1 0.55 3.c Debris Characteristics A brief discussion of the methodology used to determine the quantities for each type of debris is as follows.3.c.1 Debris Size Categorization Section 3.4.3.2 of NEI104-07 suggests a two category size distribution for material inside the ZOI of a postulated break: small fines and large pieces. The NRC Staff Evaluation for this section in the SE states that the two category size distribution is adequate, but can be problematic for debris transport refinements (e.g.Computational Fluid Dynamics (CFD) analysis) that more realistically treat the transport process (SE p. 36). Therefore, the debris size categorization for RMI foil debris outlined below utilizes more than two categories.
The Low Density Fiberglass (LDFG) and High Density Fiberglass (HDFG) debris size categorizations use two categories.
Values of debris size distribution from Calculation 2005-09080 (Reference 4.14) is provided below.Mirror and Transco Reflective Metal Insulation Debris Size Categorization The debris size distribution for RMI debris endorsed by the NRC SE (Ref. 4.28) is broken into two categories, small fines and large pieces. Small fines are defined as Enclosure Supplemental Response to GL 2004-02 Page 20 debris capable of passing through openings in gratings, trash racks, and radiological fences which are less than a nominal 4 inches (Reference 4.28). Thus, within small fines, there are fines and small pieces.The NEI 04-07 proposed distribution (Ref. 4.30) for RMI debris is 75% small fines (< 4 inch nominal) and 25% large pieces (> 4 inch nominal).
Table 3-3 of the SE (Reference 4.28) confirms this distribution.
Further support of this distribution can be found in Appendix VI to the SE, which explains that the classification comes from the testing of a Diamond Power Specialty Company (DSPC) MIRRORTM RMI cassette as reported in NUREG/CR-6808 (Reference 4.71).Section 3.2.2.4 of NUREG/CR-6808 (Ref. 4.71) relates the details of the Siemens Metallic Insulation Jet Impact Tests (MIJIT) which were conducted between October 1994 and February 1995 and are the basis for the NEI and SE endorsed size distribution for all RMI. Figure 3-7 of NUREG/CR-6808 (Ref. 4.71) is used to refine this distribution as follows (the figure is also contained in Appendix VI of the SE (Ref.4.28), as Figure VI-2): 5% are fines (1/4-inch square and smaller), 70% are small pieces (larger than 11/4-inch square and smaller than 4-inch square) and 25% are large pieces (4-inch square and larger).Table 7 -RMI Debris Size Distribution Category Catego Percentaye Fines/particulates
(-5 1/4 inch) 5%Small pieces (> 1/ inch but < 4 inches) 70%Large pieces (> 4 inches) 25%Low Density Fiberglass (Nukon) Insulation Debris Size Categorization LDFG debris such as Nukon can be divided into four categories to allow for some degree of transport analysis refinement.
The four categories are presented in the Table 8 (NRC SE to NEI 04-07, Appendix VI, Table VI-1).
Enclosure Supplemental Response to GL 2004-02 Page 21 Table 8 -Fibrous Debris Sizes Size Description JAirborne Behavior [Waterborne Behavior Fines Individual fibers or Readily moves with Easily remains small groups of airflows and slow to suspended in water-fibers settle out of air, even even relatively after completion of quiescent water blowdown Small Pieces of debris Readily moves with Readily sinks in hot Pieces that easily pass depressurization air water and transports through gratings flows and tends to settle along the floor when out when airflows slow flow velocities and pool turbulence are sufficient.
Subject to subsequent erosion.Large Pieces of debris Transports with dynamic Readily sinks in hot Pieces that do not easily depressurization flows water, and can pass through but generally is stopped transport along the gratings by gratings floor when flow velocities and pool turbulence are sufficient.
Subject to subsequent erosion.Intact Damaged but Transports with dynamic Readily sinks in hot Pieces relatively intact depressurization flows water, and can pillows but is stopped by, transport along the gratings; may remain floor when flow attached to piping velocities and pool turbulence are sufficient.
Still encased in its cover, thereby not subject to subsequent
____ ____ __ ____ ____ ___erosion.
Of the sizes listed in the table, fines and small pieces fall into the small fines category of the two category size distribution suggested in NEI 04-07. Similarly, large and intact pieces fall into the large pieces category of the two category size distribution.
Sections 3.4.3.2 and 3.4.3.3.1 of NEI 04-07 (Ref. 4.30) propose that 60% of all fibrous material within the ZOl becomes small fines. This position, accepted as conservative (although not realistic) in the Staff Evaluation of NEI 04-07, Section 3.4.3.2 in the SE (Ref. 4.28, p. 36), is based on a single LDFG debris generation test performed by Ontario Power Generation (OPG). In this test, 52% of Enclosure Supplemental Response to GL 2004-02 Page 22 the debris generated was small fines (see Table 3-7 of NUREG/CR-6808, Ref. 4.71).The use of 60% is also confirmed in Appendix II to the SE.Therefore, the fibrous debris category distribution is as follows: Table 9 -LDFG (Nukon) Debris Size Distribution Category Category Percentage Fines/Small Pieces 60%Large/Intact Pieces 40%Nukon debris is not subject to erosion when this NRC-approved size distribution is utilized.High Density Fiberglass (Temp-Mat)
Insulation Debris Size Categorization In addition to Nukon, Temp-Mat HDFG insulation debris can be generated at PVNGS. Section 3.4.3.3.1 of NEI 04-07 (Ref. 4.30) proposes that 60% of all Temp-Mat fibrous material within the ZOI becomes small fines since Temp-Mat has a higher destruction pressure than Nukon. This position, accepted as conservative (although not realistic) for Nukon in the Staff Evaluation of NEI 04-07 Section 3.4.3.2 in the SE (Ref. 4.28, p. 36), is based on a single LDFG debris generation test performed by OPG. In this test, 52%-of the debris generated was small fines (see Table 3-7 of NUREG/CR-6808, Ref. 4.71). The use of 60% fines for Temp-Mat is also confirmed as conservative in Section 11.3.1.2 of Appendix II to the SE.Table 10 -HDFG (Temp-Mat)
Debris Size Distribution Category Category Percentage Fines/Small Pieces 60%Large/Intact Pieces 40%Temp Mat debris is not subject to erosion when this NRC-approved size distribution is utilized.Debris Size Categorization for Thermo-Lag 330 Guidance pertaining to the size of debris whose destruction properties are unknown (such as Thermo-lag 330) is provided in Section 3.4.3.3 of NEI 04-07 as well as in the Staff Evaluation of NEI 04-07 Section 3.4.3.3 in the SE (SE pg. 39). The Staff agrees that modeling this type of debris as 100% small fines is conservative for plants that can substantiate formation of a thin fiber bed at the sump screen;therefore, Thermo-Lag 330 debris (both the fiber and particulate portions) are modeled as small fines herein.
Enclosure Supplemental Response to GL 2004-02 Page 23 Debris Size Categorization for Coatings Debris Guidance provided in NEI 04-07 and the NRC SE (SE pg. 21-23) indicates the following effects for coatings:* all coatings in the ZOI will fail* .all qualified coatings outside the ZOI remain intact unless damaged or degraded* all unqualified coatings in containment will fail Per Section 3.4.3.2 of NEI 04-07, all qualified coatings within the ZOI are considered small fines. This size is also conservatively applied to all unqualified coatings and all qualified damaged coatings outside the ZOI per the SE (SE pg. 21) which states the following in its interpretation of NEI 04-07:... the coating debris size within the ZOI is applicable to all "unqualified," indeterminate, and "unacceptable" coatings that fail outside the ZOI.In addition, Item 2 in the Staff Evaluation of NEI 04-07 Section 3.4.3.6 in the SE is clear in stating that its interpretation of the baseline guidance is that all coatings debris outside the ZOI has a particulate size of 10 pm.Debris Size Categorization for Latent Debris Guidance pertaining to the size of latent debris is provided in the Staff Evaluation of NEI 04-07 Section 3.6.3 in the SE (Ref. 4.28 pg. 60) which states that all debris generated outside the ZOI is small fine debris. This position is consistent with the concept that latent debris consists of loose fibers and dirt/dust particles.
3.c.2 Density of Debris The bulk densities and material densities for fibrous and particulate debris are provided below.Stainless Steel Reflective Metal Insulation Properties Transco and mirror RMI are comprised of thin layers of stainless steel foil. Stainless steel has a density of 490 Ibm/ft 3.Inorganic Zinc (IOZ) Coatings Properties IOZ coatings properties are provided in Table 3-3 of NEI 04-07 and are repeated in Table 11.
Enclosure Supplemental Response to GL 2004-02 Page 24 Table 11 -Inorganic Zinc Coatings Properties Parameter Value Particle Density (pp) 457 Ibm/ft 3 Characteristic Size (Dp) 10 pm (3.28x10-5 ft)EDoxv/Eooxv Phenolic Coatinas Properties Epoxy/epoxy phenolic coatings properties are provided in Table 3-3 of NEI 04-07 and are repeated in Table 12.Table 12 -Epoxy/Epoxy Phenolic Coatings Properties Parameter Value Particle Density (pp) 94 Ibm/ft 3 Characteristic Size (Dp) 10 pm (3.28x10-5 ft)Alkyd Coatinqs Properties Alkyd coatings properties are provided in Table 3-3 of NEI 04-07 and are repeated in Table 13.Table 13 -Alkyd Coatings Properties Parameter Value Particle Density (pp) 98 Ibm/ft 3 Characteristic Size (D,) 10 prm (3.28x10-5 ft)Latent Debris Properties Latent debris properties are provided in the Staff Evaluation of NEI 04-07 Section 3.5.2.3 in the SE (SE pg. 50-53) and are repeated below. The properties are based on the "Method 2" debris characteristic definitions.
Enclosure Supplemental Response to GL 2004-02 Page 25 Table 14 -Latent Debris Properties Parameter Value Latent Particulate Percentage by mass of latent debris inventory 85%Particle Density (p.) 2.7 g/cm 3 (168.6 Ibm/ft 3)Latent Fiber Percentage by mass of latent debris inventory 15%As-Fabricated (theoretical packing) Density (co) 2.4 Ibm/ft 3 Fiber Density (pf) 1.5 g/cm 3 (93.6 Ibm/ft 3)(1) To determine the properties of latent fiber, the SE recommends using the head loss properties of commercial fiberglass.
Since Nukon blankets are the most prevalent commercial fiberglass insulation in the PVNGS containment, its characteristic size is used for latent fiber.Nukon Properties Nukon properties are provided in Table 3-2 of NEI 04-07 and are repeated in Table 15.Table 15 -Nukon Insulation Properties Parameter Value As-Fabricated (theoretical packing) Density (co) 2.4 Ibm/ft 3 Fiber Density (If) 159 Ibm/ft'Temp-Mat Properties Temp-Mat properties are provided in Table 3-2 of NEI 04-07 and are repeated Table 16.Table 16 -Temp-Mat Insulation Properties Parameter Value As-Fabricated (theoretical packing) Density (co) 11.8 Ibm/ft 3 Fiber Density (pf) 162 Ibm/ft 3 Enclosure Supplemental Response to GL 2004-02 Page 26 3.c.3 Assumed Specific Surface Areas for Fibrous and Particulate Debris Specific Surface Areas for Debris The specific surface area (S,) is only used for preliminary analytically determined head loss values across a debris laden sump screen using the correlation given in NUREG/CR-6224.
Since the head loss across the installed sump screen is determined via testing, these values are not used in the design basis for PVNGS.Therefore, these values are not provided as part of this response.3.c.4 Technical Basis for Debris Characterization Assumptions The head loss properties of Nukon, Temp-mat, RMI, epoxy coatings, inorganic zinc coatings, and alkyd coatings are as provided in NEI 04-07. The latent debris head loss properties are based on the "Method 2" debris characteristic definitions in the NRC SE.3.d Latent Debris 3.d.1 Methodology for Latent Debris Evaluation Latent debris includes dirt, dust, lint, fibers, etc. and is a contributor to head loss across the sump screen. In accordance with recommendations in NEI 02-01, Condition Assessment Guideline:
Debris Source Inside PWR Containments, Revision 1, actual samples of discreet locations were collected as documented in Walkdown Reports (References 4.10, 4.11, and 4.12). APS performed a detailed walkdown for transportable debris in the containment building in each unit. The walkdown inventoried the amount and types of materials that could become transportable which would contribute to the sump blockage and cause detrimental effects if allowed to pass the sump strainer.Reference 4.13 (Calculation 2005-06305) determined the total latent debris in Containment based on the sample measurements and Containment areas. The total latent debris in PVNGS Unit 1, 2, and 3 containment vessels was calculated using statistical analysis, "Student t distribution," from sample collection measurements and containment surface areas and building, equipment and component surface areas using arithmetic and trigonometric formulas for basic geometric shapes.Surface areas for horizontal surfaces of round pipes, ducts, tanks, etc. considered only the top hemisphere surface. Surface areas for vertical surfaces of round pipes, ducts, tanks, etc., considered the entire circumferential surface area. Dimensions were taken from scaled drawings and reference documents.
The reactor cavity is not included since any debris washed down will drain to the reactor cavity sump.The refueling pool and transfer pool areas are not included because these areas are not concrete (steel lined) and are subject to water fill/drain activity each refueling outage. In addition, the liner surface of the containment dome is not considered in Enclosure Supplemental Response to GL 2004-02 Page 27 the calculated liner surface area because it is inverted or tangent to the vertical plane.Several methodologies were used in determining surface areas of piping, each based on specific piping characteristics within containment.
Insulated piping within containment is predominately Mirror Insulation installed by Diamond Power or Reflective Metal Insulation installed by Transco, Inc., which detailed fabrication drawings were used in totaling pipe footage and insulation diameters.
Uninsulated stainless steel piping surface areas were calculated based on pipe footage and diameters taken directly from the PVNGS piping isometric drawings.
Uninsulated carbon steel piping and 10 inch diameter CSS (uninsulated stainless steel) piping surface areas were obtained from calculations 13-NC-ZC-0208, Appendix A, Table A, page 43 and 13-NC-ZC-0237, Table 2.1, page 3. Separation of vertical and horizontal surface areas for this piping was determined based on calculated ratio of vertical and horizontal surface areas on counted pipe from detailed piping insulation drawings.Surface areas of steel beams and shapes supporting grating within containment considered the top horizontal surface of the beam or shape only. Identification and lengths of the steel beams or shapes were determined from direct take-off from the steel framing drawings.
Widths of the steel beams or shapes were determined from Manual of Steel Construction.
Foreign Materials Foreign materials inside containment may become debris during a LOCA or during Containment Spray and may add to the debris loading of the sump screen.Examples of foreign materials are valve tags, cable tray and conduit tags, etc. The type, size, and quantity of foreign materials are provided in the Walkdown Reports for Unit 2, Reference 4.2. All foreign materials except plastic labels secured with metal wire or screws were presumed to be a debris source regardless of location.Plastic labels secured with metal wire or screws were only presumed to be a debris source if within the ZOI for postulated breaks.The fire hoses inside Containment meet the requirements of NFPA 1961 and UL 19.Hence, they will not become debris sources when during a LOCA provided they are outside the ZOI of the postulated pipe break. Since all of the fire hoses are outside the S/G D-Rings and the Pressurizer enclosure, they are not included as a debris source.
Enciosure Supplemental.
Response to GL 2004-02 Page 28 3.d.2 Assumptions Used in Latent Debris Evaluation In Calculation 2005-06305 (Reference 4.13), the following assumptions are made: 1 .It is assumed that the debris is normally distributed for a given sample type.This assumption is supported by walkdown observation that debris distribution appeared uniform for a given surface type.2. The total surface area quantity of uninsulated carbon steel and 10 inch CSS piping is taken from calculations in references 4.46 and 4.47 (quantities are identical in both calculations).
To determine the horizontal and vertical quantities, multipliers of 0.72 1 (horizontal) and 0.279 (vertical) are assumed.These multipliers represent the ratio of horizontal and vertical insulated piping within containment as identified in "Appendix A" of the calculation.
- 3. Conservative assumptions were used to determine basic geometric shapes to represent the building, equipment and component in the calculation of surface area.4. Where containment surface areas (ventilation duct, equipment and pipe) were calculated based on Unit 2 specific document references, "Appendix A", itUs assumed that these values are representative of all three plant units for purposes of surface area calculation.
While it is recognized there may be unit unique variances to equipment locations and/or duct and pipe routings, these unit unique differences are not of significant variance to affect the calculation applicability to each of the three units due to the conservatism employed by the calculation.
3.d.3 Results of Latent Debris Evaluation Walkdowns were performed in all three units to determine the latent debris quantity.The Unit 2 walkdown identified 119 lbs of latent debris using the sampling methods described in NEI 02-01. Unit 2 latent debris quantity is bounding for all three units.Other potentially transportable debris was also inventoried in Unit 2 such as fibrous materials insulation, equipment labels and miscellaneous stickers (paper/foil).
The total latent debris quantity generated in each containment vessel (Reference 4.13) is totalized as follows: Unit 1 -The total weight of latent debris in containment is 101.17 lb.Unit 2 -The total weight of latent debris in containment is 119.21 lb.Unit 3 -The total weight of latent debris in containment is 105.82 lb.
Enclosure Supplemental Response to GL 2004-02 Page 29 3.d.4 Sacrificial Strainer Surface Area The total strainer surface area is 3,142 sq. ft. A sacrificial strainer surface area of 400 sq. ft. is conservatively used for chemical effects testing and head loss analysis.The sacrificial area is retained on the strainer surface area for labels, tags, stickers, placards and other miscellaneous or foreign materials.
The sacrificial strainer surface area of 400 sq. ft. is greater than the recommended 75% of the total foreign material debris area as described in NEI 04-07.3.e Debris Transport 3.e.1 Methodoloqy Used to Analyze Debris Transport As part of the response to GL 2004-02, an evaluation was performed in accordance with the methodology outlined in the NEI 04-07 guidance report and it's associated NRC SE to determine the debris loading that will result in the maximum head loss across the containment emergency sump screens. Additional guidance is taken from Regulatory Guide 1.82. The evaluation quantifies the High Energy Line Break (HELB) generated debris that will transport to the containment emergency sump screens. The amount of debris generation and characteristics of debris transport are used to determine debris accumulation.
The blockage of the strainers and its effect on NPSH of the pumps is considered conservatively when the accumulation has reached its maximum. The time dependent rate of accumulation is not credited to reduce the effect of the blockage.Debris transport was considered during fill-up and recirculation.
In determining debris transport, Computational Fluid Dynamics utilizing FLUENT was used to chart flow velocities in a three dimensional model. CFD analysis considered bulk flow velocity, turbulence and hydrodynamics in great detail and is evaluated in a three dimensional model of the sump pool. None of the debris is naturally buoyant, but much of it is fine enough to remain in suspension.
All debris remaining in suspension due to turbulence is considered to transport to the strainers.
Each type of debris was considered as to its size distribution.
Conservative assumptions have the debris breaking down to its minimum size initially, so no further particle size reduction will occur during transport.
Experimental transport data was used in conjunction with CFD to predict debris transport.
The CFD modeling techniques are consistent with NUREG/CR-6773.
All debris generated within ZOls inside the S/G D-rings is assumed to be transported to the pool at the bottom of the S/G D-rings. No significant debris blockage upstream of the strainers which could lead to water hold-up will occur. The water holdups in containment amount to a small percentage of the total water inventory and are conservatively accounted for in the minimum water level calculation.
Enclosure Supplemental Response to GL 2004-02 Page 30 There is no buoyant debris and the strainers are submerged by more than two inches so as to make this mode of blockage not applicable.
Additionally, the top of the strainers are not perforated but solid plate.The strainers are completely submerged at RAS. CS and HPSI pump suctions are piped together so RAS switchover is simultaneous for all pumps.Transport Modes Debris transport is the estimation of the fraction of debris that is transported from debris sources to the sump screen. In accordance with the guidance provided in Section 3.6.1 of NEI 04-07, four major debris transport modes were considered." Blowdown Transport
-the horizontal and vertical transport of debris by the break jet. All fiber, particulate, and RMI debris is transported to the containment floor.No debris is transported upwards to the containment dome.* Washdown (Containment Spray) Transport
-the vertical transport of debris by the containment sprays/break flow. Since all fiber, particulate, and RMI debris is modeled as transporting to the containment floor during blowdown, there is no washdown transport.
- Pool Fill-up Transport
-the horizontal transport of the debris by break and containment spray flows to active and inactive areas of basement pool. All fiber, particulate, and RMI debris is transported out of the S/G D-rings to the sump pool. No transport to inactive volumes is modeled." Recirculation Transport
-the horizontal transport of the debris in the active portions of the basement pool by the recirculation flow through the ECCS/CSS.The velocity contours provided in the CFD analysis (Reference 4.14, Attachment
- 1) are used to determine whether each debris type will stall or transport to the sump.3.e.2 Debris Transport Assumptions Certain assumptions are inherent in the PWR sump evaluation methodology presented in NEI 04-07, the SE, and various NUREGs. Additional assumptions include (Reference 4.14):* All latent fiber is assumed to have the same fiber diameter as Nukon insulation.
- Thermo-lag 330 generates debris, but no debris information is provided in NEI 04-07 for Thermo-lag.
Therefore, debris properties are assumed to be 5%Nukon fiber and 95% epoxy particulate.
For debris transport, it was conservatively assumed that the run-out flow from the CSS, Low Pressure Safety Injection (LPSI) and High Pressure Safety Injection (HPSI) pumps for both trains is exiting one pump bay. This was done to maximize debris transport to the sump and thus provide a conservative head loss evaluation.
Enclosure Supplemental Response to GL 2004-02 Page 31 3.e.3 Debris Transport Evaluation
-Computational Fluid Dynamics (CFD)The debris transport evaluation performed uses the guidance provided in the NRC SE in addition to portions of the simple methodology presented in Section 3.6 of NEI 04-07. The blowdown and washdown transport analyses were performed consistent with Section 3.6 of NEI 04-07 and Appendix VI of the SE. Pool fill-up transport analysis is performed consistent with Appendix III of the SE; however, no inactive volumes are modeled. An analytically refined recirculation transport analysis is performed using a computational fluid dynamics model of the post-LOCA recirculation flow patterns in containment.
Guidance for the recirculation transport analysis is provided in Appendix III of the SE.3.e.3.1 Computational Fluid Dynamics:
Modeling Process CFD is computer modeling of a fluid as it behaves in complex geometry with various fluid inlet sites and outlets. It can predict fluid velocities at many points in a three dimensional fluid field. With respect to the GSI-191 strainer project, a CFD analysis was performed using software package FLUENT Version 6.1.22 on the pool of water in the basement of the Palo Verde Containment during a LOCA, Reference 4.14.The flow patterns and velocities attained are used as inputs to the debris transport analysis.
The CFD modeling techniques are consistent with the NRC SE (Reference 4.28) and NUREG/CR-6773.
CFD is accomplished in several steps. Model Development involves the creation of a three dimensional computer model of the system geometry using a CAD package.During the model geometry creation process some conservative assumptions are made. These simplifications are based on experience and an understanding of the flow details of interest.
For the first stage of grid generation the model is divided into thousands of three dimensional cells within which the flow equations are solved.Afterwards the areas of special interest and of high velocity gradients are adapted to increase the number of cells. All factors influencing the flow conditions, boundary conditions, are then assigned to the model. These include inlet flows, properties of the water, and pressure loss thru the sump screens. The simulation processing consists of the computer solving a complex and coupled set of numerical equations for each of the cells within the modeled space. Finally, the results of all calculations in each of the cells must be interpreted in post processing.
This is most effectively communicated through the creation of graphical plots and animation.
Scenarios LOCA Scenarios Simulated using the CFD model (Reference 4.14) are listed in Table 17.
Enclosure Supplemental Response to GL 2004-02 Page 32 Table 17 -LOCA Scenarios Simulated Containment Break Flow Break Entry Point Sump(s) Spray Flow Scenario # Rate (gpm) Operating Rate (gpm)1 1,400 Southeast stairwell Southeast 4,885 2 2,800 Southeast stairwell Southeast and 9,770 Southwest 3 1,400 SIG D-ring opening Southwest 4,885 4 1,400 Northwest 4 ___1,400___
S/G D-ring opening Southwest 4,885 Northwest Southeast and 5 12,800 S/G D-ring opening Southwest 10,400 Scenario #5 involves both trains of the LPSI pumps operating.
However, during a recirculation actuation signal (RAS), both LPSI trains are off.3.e.3.2 Assumptions The walls and floor of Containment have been assumed smooth, i.e., the roughness height is zero. This results in a conservatively higher velocity near the surface.The top surface of the water pool was modeled as a rigid frictionless lid. This results in a CFD model that has a top of constant elevation.
3.e.3.3 Design Inputs Geometry -The geometry and inlet flow conditions used for Scenarios 1 through 4 are presented in Figure Al of Reference 4.14. This figure shows the location and flow rate of each of the spray flows as well as the location of the breaks. The drawings listed in Section 6 of Reference 4.14 were used to create the model.Figure A2 of Reference 4.14 shows the detailed geometry near the sump pit and the surrounding inner mesh screens. The grating and screens that surround the sump pit were combined into a single surface as noted in the figure. The water level is 4.5 ft above the floor for all the scenarios.
Blockages such as columns, tanks, equipment, etc., are noted. There are two sumps located in the containment, one on the southeast side and one on the southwest side.The hallway area north of the primary shield wall within the S/G D-ring will bypass a fraction of the flow. However, for conservatism, this hallway area is modeled as inactive for all breaks. All Tri-Sodium Phosphate (TSP) baskets are conservatively modeled as solid boxes.
Enclosure Supplemental Response to GL 2004-02 Page 33 Inlet and Outlet Boundary Conditions
-Break flow from HPSI will enter the pool through the four stairwells.
Conservatively, the break flow is modeled as flow through the closest stairwell to the break. The Containment spray flow rates emerging from each of the four access doors to the SG Bays are equal. The flow resistance of the existing sump screens was modeled. The outlet piping is not modeled, due to its minimal impact on velocity distribution.
Water Properties
-The water properties for density and viscosity were taken at a temperature of 2520 F for modeling because it has a lower viscosity.
Containment Spray Flow Rates -The CSS flow is distributed among six areas along the periphery of containment basement and six discreet entry points. The flow division of the 12 inlets is commensurate with the percentage of CSS that gets funneled into each. The total CSS flow is 4,885 gpm for all scenarios; but, 9,770 gpm for Scenario 2.3.e.3.4 Results Flow patterns were derived for the five scenarios.
The highest continuous velocities are used into the debris transport calculation so as to define the amount of settling that the debris experiences in the water flow path before it reaches the applicable sump.3.e.4 Debris Interceptors No debris interceptors are installed or credited.3.e.5 Fine Debris Settlement versus Transport Per the Staff Evaluation for NEI 04-07 Section 3.6.3 in the SE to NEI 04-07, all small fines debris, regardless of type, is modeled as transporting to the sump (transport fraction to sump screen =.1.0).3.e.6 Debris Transported to Sump Strainer The calculated debris transport fractions and the total quantities of each type of debris transported to the strainers are determined in Reference 4.14 and are tabulated in Table 18.
Enclosure Supplemental Response to GL 2004-02 Page 34 Table 18 -Bounding Debris Quantity at Sump for Bounding Break (SI)for PVNGS Units 1, 2 & 3 Debris Fraction of Debris Debris Quantity at Debris Type Units at Sump Screen Generated Sum Insulation within Break ZOI _..__.. .. .....SS Mirror RMI Foil [ft 2] 0.050 23,827 1,191 SS Transco RMI Foil [ft2] 0.050 30,338 1,517 Nukon [ft 3] 0.600 13.38 8.03 Temp-Mat [ft 3] Not generated for Break S1 Thermo-lag 330 (fiber)1 [ft 3] 1.00 0.18 0.18 Thermo-lag 330 [ft 3] 1.00 3.35 3.35 (particulate) 1 CS Generated Debris _Alpha-cloth
[ft 3] 1.00 0.1 0.1 Coatings ______ ...._.. .. ..Qualified IOZ [ft 3] 1.00 2.2 2.2 Qualified Epoxy [ft 3] 1.00 1.9 1.9 Unqualified IOZ [ft3] 1.00 1.28 1.28 Unqualified Epoxy [ft 3] 1.00 2.9 2.9 Unqualified Alkyds [ft 3] 1.00 0.25 0.25 Unqualified High [ft 3] 1.00 1.02 1.02 Temperature Aluminum Damaged Qualified IOZ [ft 3] 1.00 0.01 0.01 Foreign Materials Foreign Materials
[ft 2] 1.00 383.55 383.55 Latent, Debris .Latent Debris [Ibm] 0.85 170 170 (Particulates)(2,3)
Latent Debris (Fiber)(2'3) [Ibm] 0.15 30 30 (1) Volume of Thermo-lag 330 (3.53 ft 3) is modeled as 5% Nukon fiber and 95% epoxy particulate per Section 3.c.1.(2) Latent debris total conservatively increased from 119.21 Ibm (PVNGS Unit 2) to provide margin and account for potential future increases in latent debris quantities.
(3) Per NEl 04-07, Volume 2, Section 3.5.2.3, 85% of the latent debris is particulate and 15% is fiber.
Enclosure Supplemental Response to GL 2004-02 Page 35 3.f Head Loss and Vortex Analysis The procurement specification for the new strainers defines the maximum head loss across the new strainers considering the applicable debris load as 5.0 feet at a flow of 11,600 gpm. This flow is based on one LPSI pump (5,000 gpm), one CSS pump (5,200 gpm) and one HPSI pump (1,400 gpm) operating at runout flow. Only the HPSI and CSS pumps are credited in the PVNGS UFSAR Chapter 6 and 15 analyses.
The LPSI pump is shut-off at the start of recirculation; however, if the CSS pump is not operable the LPSI pump can be used and the CSS pump can be shut-off in the long term. Thus, all three pumps would not operate at the same time during the sump recirculation mode. Either the HPSI and CSS pumps or the HPSI and LPSI pumps will operate. See Figures 2 -4 for schematic diagrams of the ECCS and CSS systems. For conservatism the maximum possible strainer flow with the HPSI, LPSI, and CSS pumps was specified.
Since the available NPSH margin at a flow of 11,600 gpm is 9.8 feet (excluding the strainer), this head loss retains a NPSH margin of 4.8 feet. This margin is retained to counter any increase due to chemical effects.APS has received an extension to complete the confirmatory testing, analysis and validation for PVNGS Units 1, 2 and 3 by June 30, 2008. The head loss analysis including chemical effects will be completed prior to this extension date.
Enclosure Supplemental Response to GL 2004-02 Page 36 Figure 2 -Simplified Diagram of ECCS and CSS Systems During Recirculation Enclosure Supplemental Response to GL 2004-02 Page 37 HPS12 405 478 Containment Sump Containment Sump 205 874 HPSI 1673 Cold Leg Loop 2A 217 Cold Leg Loop 2B-N-133 541 227 Cold Leg C 'Loop IA 542 237 Cold Leg 4 Loop 1 543 247 Figure 3 -Recirculation LOCA, HPSI Enclosure Supplemental Response to GL 2004-02 Page 38 Containment Sump 673 Cs 1T T I C?45 684 678 686 687 672 688 Figure 4 -Recirculation LOCA, Containment Spray Enclosure Supplemental Response to GL 2004-02 Page 39 3.f.1 Methodologqy for Head Loss Determination CCI determined the head loss characteristics across the new sump strainer in a small-scale test loop with a representative strainer specimen and in a large-scale test loop with a complete strainer module. Head loss tests, including chemical effects, were also performed at the Multi Functional Test Loop, MFTL. The basic geometry and dimensions of a typical strainer pocket are shown in Figure 5 and Table 19.The basic dimensions of a pocket are shown here Perfoated porara ed_Figure 5 -CCI Strainer Pocket Enclosure Supplemental Response to GL 2004-02 Page 40 The following table shows the measurement of the filtering surface of the test specimen with six pockets (Reference 4.18).Table 19 -Filter Surface Dimensions INPUTS TEST POCKETS Units mm inch A 109 4.29 B 70 2.76 C 288 11.34 Radius= A/2 54.5 2.15 3.f.2 Minimum Submergence The minimum containment flood water level is elevation 84.5 ft (Reference 4.15).This is approximately
2.1 inches
above the top of the strainers.
The vortex analysis for the strainers was performed considering this minimum water level and the elevation of the top of the strainer.3.f.3 Proof of Absence of Vortices The vortex evaluation will be supplemented or replaced with a new evaluation based on recent testing by CCI. The new evaluation will be finalized prior to the PVNGS extension date of June 30, 2008.CCI conducted tests which showed the absence of air vortexes in the case of unperforated cover plates as installed at PVNGS (Ref. 4.20). Under various test conditions, no vortices were observed entering the filter pockets from the water surface.The sequence of events and the range of parameters of the CCI tests for unperforated covers are shown in Table 20.
Enclosure Supplemental Response to GL 2004-02 Page 41!Table 20 -Air Vortexes -Unperforated Cover Plates Time Water Pump Status History Flow Rate Delta P Temperature Cover Comments Observations hr: min Gpm In WC OF In (m /hr) (cm WC) O (cm)Pump is during 275.2 3.94 Running 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> (62.5) (10)Shut Down 09:19 85.1 3.94 Clean water, escaping air (29.5) (10) bubbles from two upper pockets during 66 sec after shut down Restarting 09:34 275.2 38.9 85.1 3.94 No vortex (62.5) (99) (29.5) (10)09:44 275.2 41.3 3.94 No vortex (62.5) (105) (10)09:47 308.2 45.9 3.94 No vortex (70) (116.5) (10)09:49 352.2 50 3.94 No vortex (80) (127) (10)09:51 396.3 55.1 3.94 No vortex (90) (140) (10)09:56 418.3 68.9 85.1 3.94 No vortex (95) (175) (29.5) (10)10:03 418.3 70.5 3.15 No vortex (95) (179) (8)Shut Down 10:07 A few single air bubbles Restarting 10:09 275.2 40.1 3.15 No vortex (62.5) (102) (8)10:12 398.5 56.3 3.15 No vortex (90.5) (143) (8)10:19 398.5 59.8 1.38 No vortex (90.5) (152) (3.5)10:25 275.2 40.6 3.94 No vortex (62.5) (103) (10)10:30 275.2 41.3 3.94 No vortex (62.5) (105) (10)
Enclosure Supplemental Response to GL 2004-02 Page 42 It can be seen from the test data that the lowest water coverage was 1.38 inches or (3.5 cm), which is below the 2.1 inches or (5.33 cm). It is shown in the following that the conditions for forming vortices in the test (which showed actually no vortex) were more severe than the Palo Verde condition.
The Froude number (basically a ratio of a dynamic pressure, the driving force of the vortexing, to a static pressure, the water head above the screen), is two times the head loss (HL) across the strainer surface of 5 feet (1.524 m) divided by the submergence.
This produces a local "clean screen window" velocity which would otherwise enter the term as v 2 in the Froude number divided by the submergence elevation h.For Palo Verde, the Froude number is: Fr(PV) = 2* HL / h = 2 *1.524 / 0.0533 = 57.2 For the test case with the lowest water level coverage of 3.5 cm or 1.4 inch, the Froude number becomes: Fr(test) = 2
- HL / h = 2
- 1.52 / 0.035 = 86.9 From tests with the perforated cover plates, the water coverage limit between the regimes vortex/no vortex is roughly proportional to the Froude number. Therefore, the test results for the Palo Verde can be converted by the Froude number to obtain: h(test, corrected)
= 0.035
- 57.2 / 86.9 = 0.023 m = 2.3 cm = 0.9 inch This water coverage can be considered sufficient to preclude air vortexing based on the tests. The Palo Verde installation is designed for 2.1 inches minimum water coverage.Therefore, it is determined that air vortexing is not a concern.3.f.4 Performance Tests Small scale filter tests and large scale filter tests were performed to develop strainer sizing requirements for PVNGS. The small scale and large scale tests are briefly described in the following sections.
The chemical effects tests were performed on the multi-function test loop (MFTL) for validation of strainer sizing.3.f.4.1 Small-Scale Filter Test CCI "Small Filter Performance Test Specification" (Reference 4.29) defines the test requirements to determine head losses across a representative strainer module, with 6 pockets installed in a vertical flow test loop.
Enclosure Supplemental Response to GL 2004-02 Page 43 For the "small size" tests a representative strainer specimen with six pockets was fabricated and installed in the-CCI test loop in vertical flow orientation.
This orientation allows very little sedimentation effects and forms a fairly uniform debris bed, which is more easily adaptable to theoretical modeling with head loss equations.
The CCI small-scale test loop is a closed recirculation loop as shown in Figure 6 (Reference 4.18).FIGURE 6 -CCI Small Scale Strainer Test Loop Enclosure Supplemental Response to GL 2004-02 Page 44 3.f.4.2 Large-Scale Test Loop Assembly The CCI large-scale test loop is a closed recirculation loop with a test pool, piping, pump and measuring devices as shown in Figure 7 (Reference 4.19).The water recirculation in the loop is realized by means of a centrifugal pump. The flow rate is adjustable by means of controlling the speed of the pump motor and by a throttle valve. Water flow rate is measured using an annubar within the suction pipe.Six CCI strainer cartridges with 44 pockets open (unblocked) were used in the test.__1___h_ 2T0 'I ___--~~ ~~ S~~nretidule
.L~ Water entry I ------l FIGURE 7 -CCI Test Pool Dimensions with the Strainer Segment, All Pockets are Shown Open. (Elevation View)3.f.4.3 Multi-Functional Test Loop For the chemical effects tests at the multi functional test loop a representative strainer specimen with 2 CCI cartridges with 20 pockets each was fabricated and installed in the CCI test loop in a horizontal flow orientation shown in Figure 8. This orientation simulates the real conditions at Palo Verde. For the chemical effects testing, due to the curb in front of the strainer, the lowest row of four pockets were blocked off.
Enclosure Supplemental Response to GL 2004-02 Page 45 FIGURE 8 -multi-function test loop (MFTL)3.f.4.4 MFTL Test Results The test results in Reference 4.43 are based on the chemical test specification and the MFTL test report and the corresponding test protocols.
The head loss values are normalized by the ratio of the pure water viscosities to 680 F (200 C) which allows direct comparison of the values for different data points. The clean strainer head loss through the test module for the 100 percent flow rate is 0.0235 ft. water column (WC).The relevant head losses from the tests including debris and chemicals are shown in the following Table 21 (Reference 4.43).Table 21 -Strainer Head Loss Test Results Head Loss (HL)Fluid Temp Max Head Loss Normalized to Test # Chemicals (j F) (Ft. Water) 68 F (Ft. WC)2 100% 80.8 7.23 8.47 3 100% 84.9 7.23, 8.94 2 140% 80.2 10.71 12.40 3 140% 85.5 6.28 7.80 Enclosure Supplemental Response to GL 2004-02 Page 46 Note: The dynamic viscosity at 680 F is 1.002 E-3 kg/(s m).It can be seen that test #2 is bounding for the conservative quantity of 140% debris load. Therefore, the conservative head loss of 12.4 ft. WC at a flow rate of 11,600 gpm and the temperature of 680 F can be scaled to higher temperatures, linearly by the viscosity; and linearly by the flow rate.Note: The test was performed at the scaled maximum flow rate of 11,600 gpm.However, the actual design flow rate is reduced to 6,600 gpm within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.The expected lowest initial air pressure in the containment is 10.12 psig which corresponds to a water vapor threshold temperature of 1940 F (90° C). Since chemicals have some effect on the viscosity of the water, CCI added 5 percent to all head loss values. The final normalized head loss at 68 F and 11,600 gpm is therefore:
HL (debris, nominal) = 1.05
- 12.40 = 13.0 ft.-WC Table 22 -Overall Head Loss as a Function of Temperature Temperature (0 C) 20 90 Temperature ( F) 68 194 Flow Rate (gpm) 6,600 11,600 Clean Head Loss (ft. WC) 0.03 0.092 Dynamic Viscosity (1 E-3 kg/sm) 1.002 .3144 Scaled Debris HL (ft. WC) 7.40 4.08 Total Head Loss (ft. WC) 7.43 4.17 The total calculated head loss is 4.17 feet WC for the design temperature of 1940 F, which is below the limit of 5.0 feet required in the sump strainer specification (Reference 4.31). The head loss at low temperature (7.43 feet) is above the criteria identified in the strainer specification.
However, PVNGS retained an additional 4.8 feet of margin when establishing the head loss criteria for the specification (References 4.31, 4.32, 4.33). Therefore, the calculated head loss at low temperature is below the margin available for the sump strainer of 9.8 feet.3.f.4.5 Chemical Effects Test For the chemical tests at the multi functional test loop a representative strainer specimen with 2 CCI cartridges with 20 pockets-each was fabricated and installed in the CCI test loop in a horizontal flow orientation.
This orientation simulates the conditions at Palo Verde. Due to the curb in front of the strainer and the raised strainer subfloor above the containment floor, the lowest row of four pockets was blocked off. Sedimentation effects as well as formation of a non-uniform debris bed Enclosure Supplemental Response to GL 2004-02 Page 47 show head loss margin between the theoretical modeling with head loss equation and the real condition at Palo Verde.Two chemical tests were run (Test 2 and Test 3) with identical procedure, duration, and quantity of debris. The results show two different trends." Test 3 has a thin bed effect behavior with a rapid increase of head loss while adding the debris. During the addition of the chemical debris, often the debris layer broke through and was reformed by the debris. Simultaneous with this, the head loss increased then decreased.
The head loss then stabilized and at the end of the test, the head loss was 147 mbar (4.9 ft.)." Test 2 did not show a thin bed effect during addition of debris. The head loss increased continuously while adding the chemical debris. The head loss increased gradually over time and at test end was 319 mbar (10.7 ft.).A two minute stop was made after each test end and it was shown that there is a small head loss decrease after restart, however, the head loss increased back to the value prior to the stop after ten minutes.Sedimentation of debris in front of the strainer was approximately 20%.The test report and subsequent head loss analysis have not yet been finalized.
These documents will be completed prior to the June 30, 2008 extension date for PVNGS.3.f.5 Ability to Accommodate the Maximum Volume of Debris There are two fully redundant containment emergency sumps, each servicing one train of ECOS and OSS. The calculated debris loads for strainer sizing is based on all the transportable debris at one sump. The strainer head loss testing is based on this maximum debris load. Finalization of the test report and analysis will be completed prior to the June 30, 2008 extension date for PVNGS.3.f.6 Ability of the Screen to Resist the Formation of a "Thin Bed" As stated in item 3MfA above, testing did show the formation of a thin bed effect during addition of debris during one of the tests.3.f.7 Basis for the Strainer Design Maximum Head Loss The specified maximum strainer head loss including chemical effects is 5 ft at the maximum sump flow rate for the post-LOCA recirculation phase. The head loss criteria for strainer sizing is based on 11,600 gpm for the first hour of RAS and then 6,600 gpm for the remaining duration of the ECOS mission time. This head loss criteria retains approximately 4.8 ft of margin between required and available NPSH.
Enclosure Supplemental Response to GL 2004-02 Page 48 3.f.8 Strainer Maximum Design Head Loss Finalization of the strainer head loss analysis will be completed prior to the June 30, 2008 extension date for PVNGS.3.f.9 Strainer Clean Head Loss Calculation Finalization of the strainer head loss analysis will be completed prior to the June 30, 2008 extension date for PVNGS.3.f.10 Debris Head Loss Analysis Finalization of the strainer head loss analysis will be completed prior to the June 30, 2008 extension date for PVNGS.3.f. 11 Complete Water Seal The top of the strainer is submerged at a minimum of 2.1 inches below the minimum containment flood level. There are no vents above the water level.There are two pipes and a conduit that penetrate the strainer floor plates and extend above the containment flood water level. The conduit is for the sump temperature element and is sealed below the strainer floor. The pipes are the low temperature overpressure (LTOP) relief line and a pipe that serves as a valve stem extension protector for the sump suction line isolation valve. The LTOP line is isolated and the stem extension pipe is sealed at the valve actuator.
Appendix B provides additional details of the pipes and conduit.3.f.12 Near Field Settling The MFTL test specification states that debris is to be introduced in front of the strainer; therefore no credit was taken for near-field effects. Additionally, limited sedimentation (20%) was observed during the MFTL testing.3.f. 13 TemperatureNiscosity Scaling of Head Loss Tests The head loss values from the MFTL testing are normalized by the ratio of the pure water viscosities to 68° F (200 C) which allows direct comparison of the values. The justification for the linearity between head loss and viscosity is given in NUREG/CR-6224 (Reference 4.66).3.f.14 Credit for Containment Accident Pressure in Flashing Evaluation The containment accident pressure following a LOCA is used in the flashing evaluation.
The absolute pressure after the screen is shown to be higher than the vapor pressure at the sump water temperature to ensure that flashing does not Enclosure Supplemental Response to GL 2004-02 Page 49 occur. This evaluation will be part of the head loss calculation to be completed prior to the June 30, 2008 extension date for PVNGS.3.f. 15 Absence of Flashing Behind Screen Table 23 calculates the pressure difference between the containment pressure at various time points after 1000 seconds and the vapor pressure of the sump water: Table 23 -Flashing Investigation Pressure Time Pressure Temperature Sat. Pressure Difference sec Psia (mbar) 0 F (0C) (bar) (bar)1000 68 (4.6886) 180 (82.2) (0.517) (4.17)10000 52 (3.5854) 240 (115.6) (1.724) (1.86)100000 32(2.2064) 215 (98.9) (0.974) (1.23 Basis: Pressure/Temperature profiles from specification 13-MN-1003, Rev. 0, (Reference 4.31, Attachment 5). Time points from 1000 sec considered (no recirculation before this time).The containment POST-LOCA pressure and temperature profiles are taken from Attachment 5 of specification 13-MN-1003 (Reference 4.31). The minimum pressure difference of all scenarios is 1.23 bar = 1.25 m WC = 41.1 ft. WC. This is much more than all the calculated debris head loss values. The absolute pressure after the screen is always much greater than the vapor pressure according to the sump water temperature at the same time. Therefore, no flashing with two phase flow is occurring within the debris and behind the screen.3.g Net Positive Suction Head (NPSH)The NPSH requirements for the LPSI and HPSI pumps are taken from Calculation 13-MC-Sl-0017 (Reference 4.32) and the NPSH requirements for the CSS pumps are taken from Calculation 13-MC-SI-0018 (Reference 4.33). The NPSH requirements for the LPSI, HPSI and CSS pumps are based on maximum pump flow rates during recirculation, consistent with the current NPSH calculations.
The procurement specification for the new strainers requires that the head loss of the strainers with the applicable debris load be no more than 5.0 feet.The NPSH calculations will be revised upon completion of the head loss analysis to validate adequate NPSH to the ECCS and CSS pumps. This will be complete by the June 30, 2008 extension date for PVNGS.3.g.1 Flow Rates, Sump Temperature, Minimum Containment Water Level The maximum pump flow rate of 11,600 gpm is based on HPSI, LPSI, and CSS pumps operating at pump runout flow. The runout flows for the HPSI, LPSI, and Enclosure Supplemental Response to GL 2004-02 Page 50 CSS pumps are 1400 gpm, 5000 gpm, and 5200 gpm respectively.
The assumption of the LPSI pump operating is conservative since the LPSI pumps receive an automatic signal to stop upon initiation of RAS. The flow rate of 11,600 is used to determine the strainer clean head loss. The head loss including chemical effects uses the runout flow rate of three pumps operating (HPSI, LPSI, CSS) for the first one hour following a RAS and then the runout flow rate of the HPSI and CSS pumps for the remainder of the mission time. One hour is used as a conservative time delay for the operators to stop the LPSI in the event the LPSI pumps fail to automatically stop upon a RAS. The containment sump water temperature profile is provided in Reference 4.50. The peak containment sump temperature is 242.5 F. The minimum containment water level at the initiation of RAS is 84.5 ft. The strainers are fully submerged by approximately
2.1 inches
at the minimum water level.3.g.2 NPSH Evaluation Assumptions The determination of the recirculation flow rate conservatively assumes runout flow of the operating pumps.The containment response for determination of maximum sump temperature assumes loss of offsite power coincident with a LOCA and the most severe single active failure is hypothesized to be loss of a containment spray pump with no failure of the Emergency Diesel Generator (EDG) System.For purposes of determining a minimum flood height, the assumptions were selected to minimize available water to the sump via various hold up mechanisms (see Section 3.g. 10).
Enclosure Supplemental Response to GL 2004-02 Page 51 3.g.3 Net Positive Suction Head Reauired (NPSHR)The flow rate for the HPSI, LPSI, and CSS injection and recirculation are conservatively assumed to be equal to the pump runout flow rate specified by the pump vendor. The vendor specified pump runout flow rate represents the maximum service flow rate that the pump will satisfactorily perform provided that sufficient NPSH, specified at that flow rate, is available.
Table 24 -NPSH Requirements Pump Mode Flow Rate NPSHR Basis Pump Mode(GPM) (Ft)CSS Injection
-5200 22 NPSHR as prescribed by vendor.Spray CSS Recirc -Spray 5200 22 NPSHR as prescribed by vendor.HPSI injection assumes runout HPSI Injection 1400 25 flow rate and corresponding NPSHR as prescribed by vendor.HPSI Recirculation 1400 25 HPSI H/C Injection 1400 25 LPSI injection assumes runout LPSI Injection 5000 20 flow rate and corresponding NPSHR as prescribed by vendor: LPSI recirculation mode conservatively assumes 520 5000 gpm. Original design interface requirements evaluate ECCS NPSH @ 3500 gpm.NPSHR as prescribed by vendor.Shut Down See Calculation 13-MC-SI-0015 for NPSH analysis for SDC.P S Con 5Current SDC flow rate is (SDC) _5000 gpm with NPSHR of 20 ft.3.g.4 Describe How Friction and Other Flow Losses are Accounted The ECCS and CSS line loss values were not directly affected by the modification of the sump strainer.
The calculation of suction piping friction losses for total system performance during recirculation is based on runout flow rate of the ECCS and CSS pumps in the common suction pipe.System Response Scenario for LBLOCA and SBLOCAs 3.g.5 When a large break LOCA occurs, the Safety Injection System (SIS) and the CSS are actuated.
The total time delay is assumed to be 30 seconds from the time that Enclosure Supplemental Response to GL 2004-02 Page 52 the pressurizer pressure reaches the Safety Injection Actuation Signal (SIAS)setpoint to the time that the SIS flow is delivered to the RCS.The CSS is automatically actuated by a Containment Spray Actuation Signal (CSAS)from the Engineered Safety Features (ESF) Actuation System. The CSAS is initiated by a coincidence of two-out-of-four high-high containment pressure signals, or two remote manual signals from the control room, or by loss of power to two-out of-four actuation logic channels.
The CSAS may also be initiated manually in the control room.The CSS supportive systems are automatically actuated by a SIAS from the ESF Actuation System. The SIAS is generated prior to or coincident with the CSAS by a two-out-of-four high containment pressure signals, or remote manual signals from the control room, or by the loss of power to two-out-of-four actuation logic channels.The SIAS is also actuated by low pressurizer pressure signals. The CSS suction is automatically changed from the Refueling Water Tank (RWT) to the containment emergency recirculation sump by a Recirculation Actuation Signal (RAS) from the ESF Actuation System.The CSAS starts the CSS pumps and opens the spray header isolation valves to the containment.
The specific sequence of pump and valve actuation depends on which power source is available.
If offsite power is available, then all equipment may receive power simultaneously.
If offsite power is not available, the safeguards loads are divided between the two plant emergency diesel generators and the CSS pumps are sequentially started after the diesel generators are running. During the injection mode, the minimum flow lines just downstream of each spray pump are kept open to prevent dead headed operation.
Water which passes through the minimum flow lines is returned to the RWT.Once the spray pumps are started and the valves are opened, the spray water flows into the containment spray headers. These headers contain spray nozzles which break the flow into small droplets, thus enhancing the water's cooling effect on the containment atmosphere.
As these droplets fall to the containment floor they absorb heat until they reach thermal equilibrium with the containment.
When the water reaches the containment floor it drains to the containment emergency sump where it remains until the recirculation mode begins.When RWT inventory is reduced to approximately 10% level, a two out of four low RWT level signal initiates a RAS. The RAS closes the minimum flow line isolation valves (SI-664 and 665), and opens the containment ESF sump isolation valves (SI-673, 674, 675, & 676). Upon indication that transfer to recirculation has occurred, the operator verifies that the appropriate amount of water has been discharged into the containment, and the flow path from the containment emergency sump to the suction of the injection pumps is opened. The operator also checks to see that the miniflow isolation valves are closed to prevent depletion of containment emergency sump inventory.
Following this, the operator closes the RWT isolation valves (CH-530 & 531). The RAS may also be manually initiated at the component level.
Enclosure Supplemental Response to GL 2004-02 Page 53 For a large break LOCA, the time to recirculation is taken for the limiting case for containment peak pressure, which is the Double Ended Discharge Leg Slot Break with maximum SI flowrate (Ref. 4.50). This analysis assumes a loss of off-site power and one train of containment spray flowrate.
For this case, recirculation occurs at 1438 seconds. At 1410 seconds after LOCA, the sump water mass is 3,960,000 Ibm and the sump water temperature is 178.8 0 F at 66.6 psia. At 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after a LOCA, the sump mass is 4,130,006 Ibm; and the sump temperature is 216.5 0 F at 35.3 psia.A small break LOCA may not lead to sump recirculation mode. In the event sump recirculation is required to mitigate the small break LOCA, the quantity of debris at the containment emergency sump will be less than the bounding debris transport case for the large break LOCA. Also the flow rate requirements for the ECCS or CSS pumps are less than that for a large break LOCA. Based on these reasons, the limiting case for NPSH is the large break LOCA.3.g.6 Operational Status of ECCS and CSS Pump Per the PVNGS UFSAR, Table 6.2.1-10, upon a double-ended suction leg break, after 2735 seconds, the ECCS injection mode ends and the ECCS recirculation mode begins. After 5400 seconds, the ECCS flow is realigned to provide 50 percent of the flow to the hot leg and 50 percent of the flow to the cold leg.Following a large break LOCA, the SIAS initiates operation of the LPSI pumps and HPSI pumps and the CSAS initiates operation of the CSS pumps. Initially, the water inventory for the pump suction is the RWT. Upon low level in the RWT, the RAS actuates and the pump suction source is switched from the RWT to the containment emergency sump. Upon initiation of RAS, the LPSI pumps are shut off and only the HPSI and CSS pumps continue to operate.3.g.7 ECCS Single Failure Assumptions Emergency core cooling is provided by the SIS. The system is designed to provide abundant cooling water to remove heat at a rate sufficient to maintain the fuel in a coolable geometry and to assure that zirconium-water reaction is limited to a negligible amount (less than one percent).The system design includes provisions to assure that the required safety functions are accomplished with either onsite or offsite electrical power system operation, assuming a single failure (qualified as follows) of any component.
The single failure may be an active failure during the initial period following an accident (coolant injection phase of emergency core cooling) or an active or limited leakage passive failure during the long term cooling (coolant recirculation) phase of emergency core cooling. Though the ECCS is designed to accommodate a limited leakage passive failure during the recirculation phase, it does not accommodate arbitrary large leakage passive failures such as the complete double-ended severance of piping, which are extremely low probability events.
Enclosure Supplemental Response to GL 2004-02 Page 54 3.g.8 Determination of Containment Sump Water Level The minimum water level in the post-LOCA sump pool during the recirculation mode is 84.5 feet (54 inches above the containment floor at elevation 80'-0") as documented in Calculation 13-MC-SI-0804 (Reference 4.15) for all evaluated breaks.The bounding break is the evaluated scenario where no RCS spillage or SIT volumes are credited.The calculation considers that a volume of RWT water may be diverted to the Volume Control Tank via the Boric Acid Makeup (BAM) pumps.The volume of water needed to fill the CSS supply piping is considered.
In addition to the water volume lost to the containment atmosphere and on containment surfaces, water may be lost to the reactor cavity, depending on break location.
A large break LOCA is assumed such that the coolant completely fills the reactor cavity.3.g.9 Assumptions in Determination of Minimum Water Level for NPSH Margin The following assumptions are made in calculation 13-MC-SI-0804 (Reference 4.15)for minimum flood level conservatism:
- The large break LOCA is assumed to result in debris that would block the reactor cavity drain line. Therefore, water from the break will not exit the reactor cavity until it reaches an elevation of 96'-8" which is the top of the reactor cavity cooling fans.* The large break is assumed such that the coolant completely fills the reactor cavity." The surge line break is assumed to occur at the surge line's highest elevation, which is the bottom of the Pressurizer.
- A portion of the containment spray is delayed in the containment building.
The maximum containment spray flow rate for two train operation is assumed to conservatively maximize the containment spray hold up." The amount of water needed to fill the CSS is the volume of CSS piping above the minimum Technical Specification level.* The maximum containment atmospheric conditions at RAS are assumed for each scenario to maximize water that would be held up in the atmosphere." Calculation of the water held up on the containment surfaces assumes a film thickness applied over containment vertical and horizontal surfaces.
The total surface area for containment walls, structures, and equipment is consistent with that used for the latent debris evaluations.
- RCS volume shrinkage is considered for the evaluated breaks.* ECCS leakage outside containment is assumed to be at its maximum allowable value.* The minimum RWT and SIT volumes are assumed to minimize water transferred to the containment floor during injection.
Enclosure Supplemental Response to GL 2004-02 Page 55 3.g. 10 Empty Spray Pipe, Water Droplets, Condensation and Holdup on Horizontal and Vertical Surfaces Containment spray water may be held up in the Containment Atmosphere, in the Containment Spray droplets, and in the condensation on containment building and equipment surfaces.
The following paragraphs provide the calculated volume of water held up in these items (Reference 4.15).A fraction of the total water delivered to containment evaporates in the containment atmosphere.
The quantity that evaporates is calculated based on the steam mass and pressure conditions at RAS as determined in the associated analyses.Containment spray volume holdup is determined by calculating the fall time at terminal velocity for water droplets from the PVNGS main spray median header.height and the average drop diameter, and the fall time at terminal velocity for droplets from the PVNGS auxiliary spray median header height and average drop diameter.
The delayed volume is thus the product of the fall time and the maximum spray flow rated for each system.Condensation holdup on horizontal and vertical surfaces is determined by calculating a total surface area and then applying a uniform water film thickness.
The total surface area for containment walls, structures, and equipment is consistent with that used for the latent debris evaluations.
This value is considered conservative as no distinction is made for surface area orientation; the water film is assumed uniform over all horizontal and vertical surfaces.
Enclosure Supplemental Response to GL 2004-02 Page 56 3.g. 11 Assumptions for Equipment that Displace Water in Minimum Water Level Determination
- The equipment that will displace water in the containment below the containment flood water level was based on plant drawings.
The following are assumptions used in the determination of equipment volume.* The volume of containment piping with a diameter less than 3 inches is negligible.
For simplification, the reactor vessel lower head is considered a 10' diameter, 3' high cylinder in the 65'- 0" to 78' -3" level and a 14' diameter, 1.7' high cylinder in the 78'-3" to 80'-0" level. (Based on inspection of reactor vessel drawings.)" The volume of major equipment.is calculated based on simple geometric figures.The maximum dimensions from the geometric figures are obtained from the containment building drawings." The miscellaneous structural steel is assumed to be evenly distributed.
Stairs are assumed to be uniformly designed.
Ladders are assumed to be 900 vertical stairs for purposes of volume displacement.
- It is assumed that the Reactor Cavity Sumps MRDNP01A/B at 55'-0" and the Rad Waste sumps MRDNP02/03 at 76'-0" have pumps with a 4 ft 3 displacement based on geometry of pumps shown in the pump vendor drawing.* The surface area of the concrete (Acs) is estimated using simple geometric figures. The calculated displaced volume of the concrete includes the concrete slab floors, unlined concrete and supports, the reactor cavity and concrete walls at the examined elevation." The reactor cavity is surrounded by a reinforced concrete wall (primary shield wall) and is included as part of the concrete volume when calculating the free volume of containment outside the reactor cavity above 80'-0" elevation.
- The steel volume of the TSP baskets is approximately 1% of the volume of the TSP chemical based on estimation using the TSP basket drawing." The guide tubes for incore detector cable are 2" pipes (2.38" O.D.) based on coil outer diameter of 1.75" and for the volume of the supports for these guide tubes another 100% was added. All such volume is distributed below the 65'-0" elevation.
Based on inspection of the vendor drawing each guide tube has an average length of 40 feet.* Duct near the Reactor Cavity HVAC Normal Cooling fans are considered 48" ID up to the 92' level. Above 92' the duct and fan interior is considered 30" ID to account for the fan motor, blades, etc.
Enclosure Supplemental Response to GL 2004-02 Page 57" Since centerline of Reactor Drain Tank is at elevation 85' and radius is 3.0', 45% of volume is assumed below 84.5'. Since the top of the RDT is at 88'elevation, 10% is assumed above 87'. The RCP Lube Oil Tank has a centerline at 82'-10" with radius of -1.9'. Since the top of the tank is at -84.7', it is therefore assumed 100% of displaced volume is in section 80' to 84.5'." The replacement emergency recirculation sump strainer has a total volume of 97.4 ft 3 and the original strainer had a volume of 23.5 ft 3.In order to take a conservative approach to the minimum flood level, 23.5 ft 3 is used at an elevation below 86' and the difference of the two is added once above 86.13'.* Monorail -A monorail (M-ZCN-G03) exists in the east area of the containment, outside the S/G D-ring at an approximate elevation of 85'. The I-Beam is shown as a W8 on the containment drawing and is assumed to be 8.12 inch flange or a W8 x 35 which would be a cross sectional area of 10.3 in 2.It also shows in overall length of approximately 16.5'. The hoist itself was estimated to have a volume of 2 ft 3.* Wet Layup Pumps -Two wet layup pumps (M-SGN-PO1A and M-SGN-PO1 B)are located in the east part of the containment on the El. 80' floor. From the Pedestal details, an estimated volume of 4 ft 3 was used for both pedestals.
Treating the pumps has a cylinder with a radius of 4.5" and a length of 44" results in a total volume of 3.24 ft 3.3.g.12 Assumptions for Water Sources to Minimum Water Level Determination
- Water sources available to provide flood water volume are the RWT volume, the RCS volume spill, and the four SITs (Reference 4.15).* The minimum required water transferred from the RWT during injection is ensured by RWT volume controls.
Existing administrative controls for RWT level ensure the strainers remain covered for the break case where no RCS or SIT volumes are credited as described below.* Conservative RCS and SIT tank volumes are added to the RWT inventory to establish the total volume of water available for flooding.
A break case has been recently evaluated where no RCS spillage or SIT volumes were credited for flooding.
For this case it could not be demonstrated that the strainers would remain fully submerged without the administrative controls described above.This case is being refined to evaluate, among other things, the blowdown from the RCS that would occur in this scenario in order to determine a more realistic flood level. This final evaluation will either obviate the need for the administrative control or will result in a Technical Specification change to ensure the proper RWT level.
Enclosure Supplemental Response to GL 2004-02 Page 58 3.g.13 Containment Pressure for Determination of NPSH Credit is not taken for containment accident pressure in determining available NPSH, however, minimum partial pressure of air in containment prior to the accident is considered.
This minimum partial pressure is only used for sump water temperature where vapor pressure of water is less than the partial pressure of air. Otherwise, the partial pressure is not used. The minimum partial pressure of air in the containment is 10.12 psi.It is assumed that water vapor and air are the only significant componentsof the atmosphere inside the containment during normal operation.
To minimize the partial pressure of air in containment prior to a LOCA, the total pressure in the containment is minimized and the partial pressure of water vapor is maximized.
To minimize the partial pressure of air, the containment is assumed to cool to 50°F.The maximum allowed containment temperature during normal operation (120'F) is used to determine the maximum saturation pressure of water. This maximum saturation pressure of water maximizes the partial pressure of water in the containment, thereby minimizing the partial pressure of air.3.g.14 Assumptions to Minimize Containment Accident Pressure and Maximize Sump Water Temperature The following assumptions were used to determine the accident containment pressure (Reference 4.62).* The containment response assumes loss of offsite power coincident with LOCA and the most severe single active failure is hypothesized to be loss of a containment spray pump.* The initial (pre-LOCA) containment temperature is assumed to be 120'F.* The relative humidity at pre-LOCA conditions is assumed to be 50%.3.g. 15 Containment Accident Pressure at Vapor Pressure Corresponding to the Sump Liquid Temperature Credit is not taken for containment accident pressure in determining available NPSH, however, minimum partial pressure of air in containment prior to the accident is considered.
This minimum partial pressure is only used for sump water temperature where vapor pressure of water is less than the partial pressure of air. Otherwise, the partial pressure is not credited.3.g.16 NPSH Margin The specified maximum strainer head loss including chemical effects is 5 ft at the maximum sump flow rate for the post-LOCA recirculation phase. The head loss criteria for strainer sizing is based on 11,600 gpm for the first hour of RAS and then Enclosure Supplemental Response to GL 2004-02 Page 59 6,600 gpm for the remaining duration of the ECCS mission time. This head loss criteria retains approximately 4.8 ft of margin between required and available NPSH.Since the documentation and evaluation of the testing is not yet complete for the new strainer configuration, the NPSH calculations can not be updated at this time. These calculations will be revised when the chemical effects test report and head loss analysis is completed, prior to the June 30, 2008 extension date for PVNGS.3.h Coatings Evaluation The volume of coating was determined as the product of component surface area and coating thickness.
Conservative assumptions were made where details were not readily available.
The coating thickness was conservatively taken as the maximum of the possible coating systems used.3.h.1 Coatings Systems The coating systems and corresponding maximum coating thicknesses are summarized in Table 26 (Reference 4.14).Table 26 -Coatings Coating Description Coating System Maximum Thickness Concrete and Masonry (Epoxy)Sealer Valspar 1.5 mils (1)Keeler & Long El Topcoat Valspar 17.5 mils (2)Carbon Steel (Inorganic Zinc, IOZ)Prime Coat Mobil 5 mils Valspar Carboline) Represents primer/sealer only, which is applicable to concrete walls without wainscot applied (2) Represents primer and topcoat(s), which is applicable to floors and concrete walls with wainscot applied 3.h.2 Assumptions in Post-LOCA Paint Debris Transport Analysis All coating debris is considered particulate and is assumed to transport to the sump, per the Staff Evaluation for NEI 04-07 Section 3.6.3 in the SE to NEI 04-07, (transport fraction to sump screen = 1.0).3.h.3 Head Loss Testing for Coatings Debris Stone flour/powder is used as a surrogate material for the epoxy coating debris (see References 4.18 and 4.21). For qualified and unqualified inorganic zinc coatings, carboline special zinc filler (ID Number: 02290904B00) was used (see Reference 4.21).
Enclosure Supplemental Response to GL 2004-02 Page 60 3.h.4 Basis for Surroqate Materials in Head Loss Tests The basic justification for using stone flour/powder is based on the assumption that the average particle size of 10 pm with the same total volume occupation is characterizing the typical head loss characteristic based on the Sv (average specific area) value equivalence.
There is a density difference between the coatings debris and the surrogate material.The volume of the surrogate material was equivalent to the volume of paint debris.The volumetric weight for the tests was determined with the surrogate material which insured the correct volume quantity for the head loss.In principle, the density difference can affect the settling of the coatings debris before it is transported to the strainer pockets. However, the significance of its settling behavior is relatively low due to the small particle size fraction.
The settling differences primarily affect only the larger particles of the size distribution.
3.h.5 Coatinqs Debris Generation For equipment and platform support steel, the length (scaled from drawings) and designation of each member within the 5.0 D ZOI radius is calculated for each break.The length is then multiplied by the cross-sectional perimeter of the member and the coating thickness to obtain the volume of coating debris generated.
Conservative assumptions are made where details are not readily available.
An additional 10% is added to the equipment/support steel coating debris volume for each break to account for any miscellaneous coated metal surfaces not tabulated.
For coated, uninsulated carbon steel piping within the 5.0 D ZOI radius, the volume of coating debris generated is determined by multiplying the outside perimeter of the piping by the piping length and coating thickness.
In order to determine what coated piping is located within the S/G D-ring and Pressurizer enclosure, piping isometrics for piping within Containment were reviewed.
The uninsulated carbon steel piping is assumed to be coated.For floor and wall coatings, the 4.0 D ZOI radius is truncated at the intersection with the floor or wall. The width of the ZOI projection is taken as the entire wall segment width. The minimum and maximum wall elevations are calculated based on the break elevation and the distance from the break to the wall.For the purpose of calculating the volume of coating debris, all coating within the applicable break ZOI and all damaged coating is assumed to have the maximum of the thickness values of the coatings systems used in containment.
This conservatively results in the maximum coating debris being transported to the sumps.
Enclosure Supplemental Response to GL 2004-02 Page 61 3.h.6 Coatings Debris Characteristics Per Section 3.4.3.2 of NEI 04-07, all qualified coatings within the ZOI are considered small fines. This size is also conservatively applied to all unqualified coatings and all qualified damaged coatings outside the ZOI per the SE (SE pg. 21).3.h.7 Coatings Condition Assessment Program PVNGS procedure 81 DP-OAP02 provides the overall guidelines and conditions for the "PVNGS COATINGS PROGRAM." The procedure defines the criteria to ensure coating systems are properly supplied and maintained so the coatings can perform their intended function.
The Civil Engineering organization is responsible for the PVNGS Coatings Program. Their responsibilities include specifying and approving coatings materials, and selecting appropriate color codes, performance monitoring of coatings in Containment and maintaining the Unqualified Coatings Program. The implementation of specifications, procedures, and inspections are coordinated through Civil Engineering.
The frequency of inspections is based on the conditions of the work. The Coatings Planner and/or Engineering may choose to impose higher inspection and verification based on the conditions of the work. The PVNGS Coatings Program shall specify and verify control measures to ensure that inspections and verifications are adequate to achieve the required quality. The PVNGS QA program allows for inspections (verifications) to be performed through worker verification, second party verifications, independent verification, and/or independent inspection.
Coating activity inspections at PVNGS are performed primarily by second party verifications.
3.i Debris Source Term 3.i.1 Programmatic Controls to Limit Debris Sources in Containment Specification 13-AN-0448 (Reference 4.63) identifies the technical requirements to control the temporary installation of maintenance and monitoring equipment in Seismic Category I Building to ensure the safe and continued operation of PVNGS.Transient materials are unattended/uncontrolled temporary equipment and/or material in areas containing SSCs that are safety related whenever they are required to be operable or available for safe shutdown and/or continued safe shutdown.Transient materials and equipment include nylon or tefzel wrap, cable wraps (e.g., blue tefzel cable wraps), weld attachments, anchor bolts, chain, nylon rope, wire rope, scaffolding, tie wire, and snow fencing in temporary bull pens. Operations tracks and monitors the acceptable placement and restraint of transient material.
All short term transient material that has safety related SSCs within two times its zone of influence is required to be restrained per the specification.
Transient material is required to be removed as soon as the work or activity is complete.A maximum of 66 square feet of transient materials is permitted in Containment provided the area (square footage) is quantified and tracked (Reference 4.39).
Enclosure Supplemental Response to GIL 2004-02 Page 62 Procedure 4OST-9ZZ09 (Reference 4.39) requires a surveillance to verify cleanliness of the Containment prior to establishing Containment integrity.
The purpose of the procedure is to perform a visual inspection which verifies that no loose debris or latent fibrous debris is present in the containment which could be transported to the Containment Sump and cause restriction of the pump suctions during LOCA conditions.
Visual inspections are performed in all accessible areas of the containment, at least once daily in affected areas of containment entry, and all affected areas during final entry when Containment Integrity is established.
Once all work and testing is complete, all personnel are prohibited from entering containment.
The two main goals of the procedure (Reference 4.39) are that no loose materials could be transported to the containment emergency sump under LOCA conditions; and any loose materials that could be transported to the sump screens will not cause damage to SI System components, e.g., erode SI pumps, clog valves, etc.Thermo-lag fireproofing is controlled in containment requiring that none is added or modified in containment without engineering analysis and approval with respect to debris generation (Reference 4.69).3Ji.2 Housekeeping Programmatic Controls The site housekeeping procedure, 3ODP-OWM12 (Reference 4.78), encompasses all work activities as it pertains to cleanliness of the plant. Procedure 1 3-AN-0448 (Reference 4.63) invokes the installation specification for control of transient materials.
3Ji.3 Foreign Material Programmatic Controls -Zone Ill Exclusion Area Walkdowns were performed in all three units to quantify the latent debris. The Unit 2 latent debris quantity of approximately 119 lbs is bounding for the three units. The debris transport calculation conservatively assumes 200 lbs of latent debris.Transient materials in Containment are controlled by procedure, and visual inspection for loose debris is performed prior to establishing Containment Integrity.
See Sections 3Ji.1 and 3Ji.2.3Ji. Programmatic Control of Permanent Plant Changes Inside Containment The Design Inputs Requirements Checklist (DIRC) of the Design Change Procedure 81TD-OEE10 establishes controls such that no large volumetric items are added or deleted in containment that could affect the water level to free volume relationship (tank curve) of containment or LOCA flood level. Topical Question 7 requires the identification of any material which might affect the amount of aluminum in containment, corrosion compatibility with existing plant components, and protective coatings.
Topical Question 10 requires the identification of any proposed change that would adversely affect the ECCS and CSS pump NPSH as a result of a change in the amounts of fibrous materials and or unqualified coatings or as a result of a change in the amounts generated and transported to the sumps. In addition, it is also required to evaluate if the change affects. the flow paths of water to the Enclosure Supplemental Response to GL 2004-02 Page 63 recirculation strainers or water holdups in containment; or increase or decrease the free volume in containment, the LOCA flood level, or the effective heat sink characteristics; or add surfaces that can collect latent debris, or add zinc or aluminum, TSP, or uncoated concrete in containment that could affect post-LOCA chemistry.
3.i.5 Maintenance Activities Managqed in Accordance with Maintenance Rule, 10 CFR 50.65 PVNGS Coating Program defines the criteria to ensure coating systems are properly applied and maintained so that the coatings perform their intended function (Reference 4.36). The program also defines the different categories of coating activities.
At PVNGS, the civil engineering department is responsible for the implementation for the coatings program. Responsibilities include specifying and approving coatings, materials, and selecting appropriate color codes, performance monitoring of coatings in containment, and maintaining the Unqualified Coatings Program. The implementation of specifications, procedures, and inspections are coordinated through Civil Engineering.
Coating work performed on structures and components for containment are classified at Q-Class. All materials used for this application are also Q-Class.Safety-related coatings are coatings that are applied inside of containment (Reference 4.35). The detachment of the coatings could affect the safety function of a safety-related structure, system, or component (SSC). Coating can be classified as follows: 1) Service Level 1 Coatings, 2) DBA Qualified Coating Systems, 3) DBA Unqualified Coating Systems, and Exempt Coatings.
Service Level 1 coatings are used in areas inside containment where coating failure could adversely affect the operation of post-accident fluid systems and may impair safe shutdown.
DBA Qualified Coating Systems are single or multiple coatings applied in accordance with the tested configuration with ANSI N1 01.2 or ASTM D391 1 for material testing.Reportable DBA Qualified Coatings are applications that are located within the containment building secondary shield walls. DBA Unqualified Coating Systems are coating applications that deviate from the original DBA tested configuration or have not been DBA tested. Exempted coatings is a historical designation for coatings inside of containment prior to U1R13, U2R13, and U3R13 to which Regulatory Guide 1.54 requirements were not imposed. During and after U1 R12, U2R13 and U3R13, all coatings that do not meet the requirements for DBA Qualified Coatings Systems shall be included in DBA Unqualified Coating systems. Exempted coatings include line items such as motors, hand wheels, electrical cabinets, loudspeakers, color code markings on pipe, and surfaces inside of cabinets or enclosures such as the interior of the Polar Crane cab. There is no immersion safety-related or non-safety related coatings identified for containment use.Materials procured for safety-related applications for containment shall meet the criteria of 10CFR 50 Appendix B and the PVNGS UFSAR requirements for coating applications.
These materials shall be a DBA qualified coating system in accordance with PVNGS requirements.
DBA Qualified Coating Systems are single or multiple coatings applied in accordance with the tested configuration that complies with Enclosure Supplemental Response to GL 2004-02 Page 64 ANSI N101.2 or ASTM D3911 for testing, and ANSI N101.4 or ASTM D3843 for application documentation requirements.
Inspections are an integral part of a coatings application project. The PVNGS Coating Program includes measures to ensure that inspections and verifications are adequate to achieve the required quality. The PVNGS QA program allows performance of inspections and verifications through worker verification, second party verifications, independent verification, and/or independent inspection.
Coating activity inspections are PVNGS are performed primarily by second party verifications.
Coating applicators are required to complete the appropriate Coatings Inspection training and possess the Qualification Card for Coating applications.
Coatings both qualified and non-qualified are controlled in containment requiring that none are added or modified in containment without engineering analysis and approval with respect to debris generation.
Specification A0-AN-0449 and the coatings program procedure 81 DP-OAP02 govern any such application of coatings.3.i.6 Insulation Change-Out DMWO 2822654, Revision 0 removes Fiberfrax insulation from the containment building secondary shield wall pipe penetrations in Units 1, 2 and 3. The effect of this change is to reduce the debris burden at the strainers which decreases the expected head loss across the sump screen. In addition, some Nukon insulation was removed from around the letdown delay coils which were previously installed after original plant design and construction.
3.i.7 Modifications to Reduce Debris Per DMWO 2822654 Revision 0, the removal of Fiberfrax and Nukon insulation as described in Section 3.i.6 reduces the debris burden at the sump strainer during DBAs requiring recirculation operation of the ECCS and CSS.3.i.8 Modifications to Equipment or Systems to Reduce Debris PVNGS has not made any modifications to equipment or systems to reduce the potential debris burden at the sump strainers.
3.i.9 Coatings Program Modifications or Improvements The current PVNGS coating program and specification (References 4.36 and 4.57)consist of the specifications of materials, protection of plant equipment, surface preparation, application, and inspection procedures.
The purpose of the coatings program for painting and coatings activities is to provide controls for painting and coating activities.
The Maintenance Coatings Program outlines the requirements for the painting and coatings program, and the implementation of engineering requirements established in procedure 81 DP-OAP02 and specification AO-AN-0449.
The Maintenance Coatings Program is divided into industry driven categories that are based on the impact to the plant. Safety related and non-safety related coatings, Enclosure Supplemental Response to GL 2004-02 Page 65 pertains to the potential impact that the coatings has on the safe shutdown of the unit. Failure of non-safety related coatings applications does not affect safe shutdown of the unit, however, coating applications used in these areas can be significant, with the consequence of failure of the coating jeopardizing equipment reliability, performance, and creating an economic impact on PVNGS. The various coatings categories used at PVNGS are as follows: 1) Safety Related Coatings, 2) Exempted Coatings, 3) DBA Unqualified Coating Systems, 4) Safety Related Immersion Coatings, 5) Non-Safety Related Immersion Coatings, and 6) Non-Safety Related Coatings.Under theCoatings Program, inspections of coatings systems are scheduled every outage on a pre-established basis to verify containment liner coating thickness.
General visual surveillance of other coatings in containment is also conducted in conjunction with the coating program. In accordance with the program, a total surface area equivalent to one unit will be inspected among the three units over a period of approximately ten years.3.J Screen Modifications Package 3.j. 1 Description of Sump Screen Design Modifications Two sumps are installed, each serving one train of ECCS and 055 pumps. The sumps are installed in separate depressions in the containment floor. The sumps are located at the lowest practical elevation in containment, below the floor at elevation 80'. There is a 3 inch curb that impedes heavy debris that can be swept along the floor from clogging the strainers.
The curb also provides protection from'surface drains. No drains from upper regions impinge on the screen assemblies.
There is no significant physical barrier between the strainers above the floor, but the distance between them is 26 feet. Physically separated sumps preclude simultaneous damage to both screens. Main Steam line breaks or Feed Water line breaks do not require the function of the recirculation sumps. There are no high energy pipe lines in the vicinity of the sumps or screens. Therefore, pipe whip and impinging jets are not issues to be considered.
The screen is fabricated from austenitic stainless steel and zinc-coated carbon stee~l.Both materials have a low sensitivity to spray-induced corrosion and will not be adversely affected by periods of inactivity.
The strainers are designed for complete submergence below the minimum calculated water level. The new strainers are of robust design and can easily withstand the modest pressure differential loads even considering debris build-up.There is a top to the strainer modules, but the manner of construction and fit up is such that the sheet metal will not be absolutely sealed. Any air that would initially be inside the strainer modules would self-vent.
The strainer configuration is designed with an access manhole in the new stainless steel floor that supports the strainer modules. This will allow personnel access to Enclosure Supplemental Response to GL 2004-02 Page 66 inspect the valves, piping, and vortex breakers within the sumps. The Inservice Inspection Program specifies the frequency and details of these inspections.
The new strainers are of advanced passive design using convoluted structure.
The strainer assemblies consist of horizontal cassette pockets made of perforated plate that provide the screen area (see Figure 9). The strainer modules resemble "pigeon holes" or rectangular pockets which greatly increases effective area on a limited floor footprint.
Each pocket is approximately 3 inches wide by 5 inches high, and the leading edge is solid plate, which acts as an integral trash rack to protect the perforated portion of the pocket from debris. With the horizontal cassette pocket (specialty) design, the strainers consist of both vertical and horizontal flow paths through the screening elements.
All pockets are submerged at the minimum post-LOCA flood level. Since the new strainers are approximately 3,142 ft 2 vs. the original 210 ft 2 'screens, design liquid flow velocity through the new strainers is less than that for the original screens.(1)(2)7X 16 Cartridge Unit 1X 10 Cartridge Unit 10" Pipe Vent 2875 SQ FT 266 SQ FT 1 SQ FT TOTAL FLOW AREA APPROX 3142 SQ FT SIZE OF SCREEN PERFORATIONS:
0.083 IN FIGURE 9 -WEST SUMP SCREEN ARRANGEMENT (East sump is similar in arrangement)
Enclosure Supplemental Response to GL 2004-02 Page 67 The sumps are designed to preclude air ingestion because of the very low velocity through the new strainers and the vortex breakers on the inlet pipe in the sumps are retained.
No other detrimental hydraulic effects will occur at the sump or at the inlet to the pumps.3.j.2 Other Modifications by the Strainer Replacement To install the new sump strainer floor and strainer module cartridges, the containment sump temperature element, associated conduit, and the sump access ladder were relocated.
3.k Sump Structural Analysis 3.k.1 Sump Strainer Structural Analysis The new strainers are installed in locations that are remote to high energy line breaks and are located outside of the bio-shield wall. The strainers consist of pocket cartridges, which are assembled together in strainer modules. These modules, which are tied together using a module support structure, are supported at the base by a subfloor that covers and seals the entire sump pit. The subfloor is attached to the base of the columns of a modified version of the previous sump screen frame.CCI analyzed the imposed stresses on the ECCS sump strainer standard module cartridge (Reference 4.22), the strainer module and support structure (Reference 4.24), and the supporting subfloor (Reference 4.23). These components were further assessed for a larger differential pressure by CCI (Reference 4.67).The modified version of the previous sump screen frame was analyzed for the applied loads from the CCI subfloor.In the strainer component and supporting structure final stress evaluation, the limits of the American Institute of Steel Construction (AISC) Manual of Steel Construction, 9th Edition and the limits of the ASME B&PV Code, Subsection NF are both satisfied.
The requirements of the American Iron and Steel Institute (AISI) manual were also considered for the thin sheets of the strainer.The strainer is not a pressure retaining part. Therefore, it is not subjected to any pressure transients or hydrostatic pressure during normal operation of the plant. If the strainer areas are covered with debris and the pumps are in use, then there is flow through the strainer.
Hence, the critical load components, due to loads caused by the pressure drop, are the perforated sheets.The strainer components and supporting structures were evaluated for the load combinations in the Palo Verde UFSAR. In the analysis, it was determined that the governing load combination was 1.7 S > D + P + Ta + E where S is the AISC normal allowable stress, D is dead load, P is the stresses caused by differential pressure across the strainer during flooded condition, E' are safe shutdown earthquake (SSE)induced stresses, and Ta are accident thermal stresses.
As the LOCA condition governs, the earthquake induced stresses include the effects of sloshing and (
Enclosure Supplemental Response to GL 2004-02 Page 68 consideration of the hydrodynamic masses. The amount of debris taken under consideration for the calculation of the equivalent pressure which acts over the two strainer modules (large and small modules) is 520 lbs and 325 lbs. This corresponds to 32.5 lbs/cartridge since there are 16 or 10 cartridges in the two strainer modules.The analysis of the cartridges was performed using ANSYS, version 10.0. Stresses were calculated for both the perforated and unperforated plates. For the AISC evaluation, an allowable stress increase factor of 1.7 for SSE is used in accordance with the load combinations.
For the ASME evaluation, an allowable stress increase factor of 1.5 is used. For both the perforated and unperforated plates, the maximum membrane stress, om, is less than 1.7 x 0.6 times the yield stress (AISC) and less than 1.5 times the calculated allowable stress (ASME). The maximum membrane plus bearing stress, am + ob, is less than 1.7 x 0.66 times the yield stress (AISC) and less than 1.5 times the calculated allowable stress x 1.5 (ASME). Thus, all stresses are below the stress limits for load combinations for SSE accelerations.
The analysis of the modules was also performed using ANSYS, Version 10.0. Since standard modules consist of the support, the duct, and either 10 or 16 cartridges, a module with 16 cartridges is conservatively considered in the analysis.
The maximum membrane stress, am, is less than 1.7 x 0.6 times the yield stress (AISC)and less than 1.5 times the calculated allowable stress (ASME). The maximum membrane plus bearing stress, 0m + Ob, is less than 1.7 x 0.66 times the yield stress (AISC) and less than 1.5 times the calculated allowable stress x 1.5 (ASME). Thus, all stresses are below the stress limits for load combinations for SSE accelerations.
For the various component parts of the strainer module, e.g. duct lower plate, duct upper plate, duct side panel, etc., the maximum membrane stress, am, is less than the material yield strength.
Further, the maximum membrane plus bending stress, am + ob, is less than the cumulative maximum stress plus bending stress.In the sub-floor calculation, the limits of the American Institute of Steel Construction (AISC) Manual of Steel Construction, 9th edition are satisfied.
The strainer modules are included with a beam and spring model representing its real center of gravity, mass, and stiffness.
The springs were defined so that the beam model and the structural model have the same fundamental natural frequencies in all coordinate planes.ANSYS computer program was used to perform the plate stress calculation at the strainer opening. The maximum membrane plus bending stress is less than the allowable membrane stress limit. The computer program also calculated the bending stresses for quadratic and rectangular plate geometries.
The maximum bending stresses were below the allowable stress limit. Also, the maximum bending stresses for the sump access base plate and access cover are below the allowable stress limit.CCI calculation 3SA-096.043 (Reference 4.67) structurally evaluates the maximum allowable stress difference of the three major strainer components;
- 1) Cartridge, 2) Module, and 3) Subfloor as calculated in References 4.22, 4.23, and 4.24. The Enclosure Supplemental Response to GL 2004-02 Page 69 calculation uses the same geometry and calculation models to find the maximum allowable pressure difference.
The calculations show that the maximum allowable stress difference over these three major strainer components is as follows:* Cartridge:
6,527 psi (0.045 MPa)* Module: 4,496 psi (0.031 MPa)* Subfloor:
6,527 psi (0.045 MPa)The weakest component and the limiting condition is the module (frame structure).
Maximum Allowable Pressure Difference The original analyses performed in References 4.22, 4.23, and 4.24 were based on a maximum allowable pressure difference of 5 feet water column (WC). An additional analysis was performed in Reference 4.67 to determine the maximum allowable pressure difference.
The maximum allowable pressure difference for the strainer structure and the subfloor was determined to be 10.4 feet WC at the material temperature of 70°F (Reference 4.44). The yield strength (Sy) of 304 L stainless steel is temperature dependent.
Since the allowable pressure difference is proportional to this Sy, the maximum allowable head loss for the strainer structure at 194 0 F was computed to be 8.98 ft. WC.Design Codes and Engineering Handbooks The following Design Codes and Engineering Handbooks were used in the analysis of the sump strainer structural analysis:* 2004 Edition ASME Boiler and Pressure Vessel Code, Section I1: Part D-Properties
- AISC, Manual of Steel Construction, 9th Edition* AISI, North American Specification for the Design of Cold-Formed Steel Structural Members, 2001 Edition* T. Kirk Patton, Tables for Hydrodynamic Mass Factors for Translational Motion* Hurty, W. and Rubinstein, M., Dynamics of Structures, Prentice Hall Inc., Englewood Cliffs, New Jersey* Roarks' Handbook of Formulas for Stress & Strain, Sixth Edition, Warren C. Young* Palo Verde NGS Design Basis Manual C6, Revision 6, Category I Building Topical Enclosure Supplemental Response to GL 2004-02 Page 70 3.k.2 Frame Structural Analysis The existing frame for the sump strainers was modified and supports the strainer subfloor.
The design of the modified sump frame for the attachment of the new CCI Sump Strainers was modeled in GTStrudl with the actual horizontal forces acting at the center column members on the two longer sides of the frame. This is consistent with the CCI structure load transfer (connection) points to the existing PVNGS strainer frame (Reference 4.3). The equivalent static seismic loads, hydrodynamic loads, and sloshing loads were also applied to the model. GTStrudl was used to check the Interaction Coefficients (IC) for W6 column members. The GTStrudl model was used to determine the plate stresses and anchor forces under the applied loads. The plate stresses were shown to be less than the allowable plate stresses determined using AISC, times an allowable stress increase factor of 1.7. The anchor bolt forces (tension and shear) were shown to be less than the allowable tension and shear loads for cast-in-place anchors.The hydrodynamic mass was calculated in the two horizontal orthogonal directions according to the column orientation and the loading direction.
The sloshing loads were conservatively calculated for the loads parallel to the flanges and perpendicular to the flanges.The frame design calculations were performed according to the 9 th Edition of the AISC manual. Based on no differential pressure or thermal roads, the following load combination governs: 1.7 S > D + E' (SSE)Where E' is SSE induced stresses which includes hydrodynamic and sloshing effects during flooding conditions.
S is the AISC normal allowable stress and D is dead load.The calculation (Reference 4.3) has evaluated the frame design per the applicable specifications and standards and these are the maximum interaction coefficients:
IC maxCol = 0.285 < 1.7, maximum IC value for W6 column members IC weld = 0.403 < 1.7, maximum IC value for the weld between the column members and the baseplate ICplate = 1.567 < 1.7, IC value for the base plate ICanchor = 0.862 < 1.0, IC value for anchors on the base plate ICstfplate
= 0.786 < 1.0, maximum IC value of the stiffener plate IC stfweld = 0.646 < 1.0, maximum IC value of the stiffener weld By evaluation of the existing frame design of the containment emergency sump for the attachment of the new CCI sump strainers, it is clear that the member stresses, Enclosure Supplemental Response to GL 2004-02 Page 71 the member connections, the base plates and anchors are qualified according to the Palo Verde specifications for the revised screen configuration.
3.k.3 Seismic Analysis The strainers are Seismic Class 1 structures.
The natural frequencies are calculated for the strainer sub-floor for submerged strainers.
For the pool filled condition, the hydrodynamic water masses are considered in addition to the steel mass.In Reference 4.23, Attachment A, CCI calculated the loads due to sloshing of water subjected to horizontal acceleration.
The maximum sloshing load per module is 578 lbf while the incidence load height is 2.258 ft. The conservatively calculated hydrodynamic water mass covers the influence of the sloshing effect from Attachment A in the y-direction of the large strainer module and in the x-direction of the small strainer module.In Reference 4.23, Attachment B, the ANSYS model calculated the dominant mode frequencies in the x, y, and z-direction as 11.50 Hz., 11.06 Hz., and 14.46 Hz., respectively.
The seismic response spectra is given in Tables 27 and 28 and Figure 10. The damping values of 5% for horizontal and 7% for vertical accelerations of the critical damping are used for SSE. The SRSS combination method was used to combine the results for the x, y, and z-direction.
Table 27 -Seismic Accelerations, g Levels Freg. 0.1 0.171 1 1.7 12.6 12.8 13.6 13.8 1 5 10I 20 25 33 100 SSE Horiz. 0.02 0.05 0.5 1.12 1.12 0.95 0.95 1.00 1.00 0.65 0.34 0.31 0.31 0.31 (D=5%)Table 28 -Seismic Accelerations, g Levels Freq. 0.1 0.17 0.5 1 2.5 1 5 I 10 20 25 33 100 SSE Vert. 0.01 0.05 0.18 0.33 0.67 0.67 0.39 0.39 0.39 0.34 0.34 (D=7%)
Enc losure Supplemental Response to GL 2004-02 Page 72 Figure 5-1 Seismic Accelerations SSE 1: to to 2 \.° .,/0,1 I 10 goo 0.f to Mi FIGURE 10 -Seismic Accelerations SSE Evaluations Performed for Dynamic Effects such as Pipe Whip 3.k.4*The new sump strainer modules are located between the bioshield wall (outside the S/G D-Ring) and the containment liner. Therefore, the new strainer design is not exposed to dynamic effects such as pipe wipe, jet impingement, and missiles associated with high-energy line breaks.Credit for Backflushinq Strategy 3.k.5 3.1 PVNGS sump strainer does not have back flushing capability.
Upstream Effects Summary of Upstream Effects Evaluation 3.1.1 The path of water flow through the containment upstream of the containment emergency sumps during a LOCA is affected by debris collecting at possible restrictions.
Water could be retained at possible pockets or holdups that would effectively reduce the amount of water available for recirculation.
To address these potentials, equipment location drawings were reviewed to determine likely flow paths and possible choke points. A walkdown of the flow paths for all floor elevations was conducted inside and outside the S/G D-rings in PVNGS Unit 2. This walkdown was performed following guidance from NEI 02-01, and the results are documented in Reference 4.2 (PVNGS Document N001-1106-00007).
Based pn design similarities between PVNGS Units 1, 2, and 3, the Unit 2 walkdown results' are applicable to all PVNGS Units.
Enclosure Supplemental Response to GL 2004-02 Page 73 The containment structure outside of the S/G D-Rings consists of four distinct floor elevations excluding the fuel pool and reactor cavity area. These floor elevations are 80'-0", 100'-0", 120'-0" and 140'-0". Above floor elevation 140'-0" are miscellaneous partial equipment/personnel platforms that do not obstruct water flow to the sumps.The walkdown verified that clear flow paths exists to the sumps such that injected water would not be held up and could freely flow back to the sumps. During the walkdown no choke points were identified.
3.1.2 Evaluation
of Flow Paths from Postulated Breaks and Containment Spray Washdown Upper Elevations Floor elevations 100'-0", 120'-0" and 140'-0" consist of concrete slabs and industrial grating. There are no gross openings through these floor elevations other than penetrations for pipe, duct, electrical tray/conduit and equipment.
Stairways accessing each floor elevation are made of grating. Typical attributes of each floor elevation include the following (floor elevation 80'-0" will be discussed separately):
- There is a level transition where the concrete floor slab meets floor grating* There is a 3" gap between the concrete floor slab and containment liner and at all of these junctures there is a 4" high steel toe-plate on the concrete floor slab.* There is no gap between floor grating and the containment liner.* There are 3-1/2" to 4" high toe-plates at all penetrations through both the concrete floor slabs and floor gratings.Flow paths through floor elevations 100'-0", 120'-0" and 140'-0" appear unobstructed.
Water from containment spray will typically rain through the grating and flow from the concrete floor slabs and through the grating. Debris would typically need to fit through grating slots to get below. There is a sufficient open concrete/grating interface to negate development of choke points for the water/debris mix flow from concrete floor slabs onto the grating.On floor elevation 100'-0", there are labyrinth-type openings to each RCP bay.These openings were discounted as flow paths in or out of the S/G D-Ring by the walkdown team. This is because each opening opens to a small triangular shaped concrete slab inside the S/G D-Ring before transitioning to grating or open space.Due to the S/G D-Ring structural geometry, it is assumed that all water flowing into or originating from inside the S/G D-Ring will flow down to the 87'-0"/80'-0" elevation and exit the 80'-0" labyrinth-type openings on its way to the sumps. Refer to the discussion of the 80'-0" floor elevation for a more detail account of the labyrinth-type openings.Storage containers/racks for lead shielding blankets and scaffolding were observed on floor elevations 100'-0", 120'-0" and 140'-0" and were assessed by the walkdown team to not be in a location that would impact water/debris flow.
Enclosure Supplemental Response to GL 2004-02 Page 74 The head inspection stand has adequate drainage which would not impede flow from containment spray. A small amount of water will puddle in slight variations of the solid floors and other horizontal surfaces and water drops will cling to the vertical surfaces.
However, no other obstructions will significantly impede water flow from the upper elevations of containment to the 80'-0" elevation.
Doors to S/G Bays at Elevation 80'-0" Each S/G D-Ring has one door at the 100'-0" elevation and 2 doors at the 80'-0" elevation.
The doors at the 100'-0" elevation probably will not pass any water in that they are above the maximum water flood level and water will collect at the lower elevations.
During normal operation, each opening has a closed steel framed door with "pressure-relief' panels. The elevation 80'-0' door pressure relief panels are held in place by clips. The panels will release during a LOCA at various pressure differentials according to Reference 4.4. The highest such differential inside over outside is 1.0 psi which is a water column difference of approximately 2.3 feet. This ensures that the doors' panels will open and stay open for a LOCA and will not be an impediment to flow.The top of the S/G D-Ring walls are at elevation 155'-0" and is open down to the S/G D-Ring floor at elevation 87'-0". The floor at elevation 87'-0" transitions to the containment basement elevation 80'-0" by way of a vertical 7' precipice bounded by a handrail and 4" toe-plate.
This edge is unobstructed at the metal stairs down to elevation 80'-0". Water from a LOCA and Containment Spray would flow out from the S/G D-Rings to the basement of Containment via these labyrinth-type openings.Each S/G D-Ring space from El. 155'-0" to E. 87'-0" is occupied by the Steam Generator, two RCPs, miscellaneous catwalks and platforms at elevations 100'-7", 107/108'-0", 117'-9 1/8", 128'-0", 136'-1-1/4", 148'-9" and stairs down from 157'-6".The southwest and southeast labyrinths open into the containment basement approximately 25' from the west side of the southwest sump and east side of the southeast sump, respectively.
Obstacles in the flow path primarily consist of platform support steel columns, platform access stairs, miscellaneous pumps and TSP baskets.Water flowing outside the S/G D-Rings on the containment at 80' elevation from the north side to the south side would experience a very open floor plan as it approached the containment emergency sumps.Other Upstream Effects The bottom of the Pressurizer Compartment is at elevation 100'-0". However, at this elevation there is a 2'x 16'-6" opening to elevation 80'-0" below. Water from a LOCA inside the Pressurizer Compartment would pour through this opening (which is above the northwest labyrinth-type opening to the S/G D-Ring) and flow to the sump via the west side of containment elevation 80'-0".
Enclosure Supplemental Response to GL 2004-02 Page 75 The following upstream effects are already appropriately considered in the calculation of LOCA minimum water level (Ref. 4.15):* Water will be retained in the Containment Spray droplets as they fall.* Water that fills the Containment Spray headers also reduces the depth of water at the strainers.
- Water inventory at the sumps is also reduced by the large amount of water vapor in the LOCA Containment environment.
3.1.3 Measures
Taken to Mitiqate Potential Choke Points Walkdowns performed to verify flow paths in containment to the containment emergency sumps identified no potential choke points. No changes to mitigate choke points is required.3.1.4 Evaluation of Water Holdup at Installed Curbs or Debris Interceptors There is a 3" curb at the base of the containment emergency sump strainer.
This curb does not result in water holdup. Debris Interceptors have not been installed at PVNGS.3.1.5 Potential Blockage of Reactor Cavity and Refueling Cavity Drain The Refueling cavity is a cavity surrounding the upper part of the reactor and extends from the operating floor at 140'-0" elevation down to the reactor flange at the 114'-0" elevation.
The western part of the cavity encompasses the fuel upender which extends down to the 98.5' elevation.
This cavity will collect approximately 11%of the containment spray flow and would fill except for two floor drains. Both are 10" diameter drain pipes in the floor of the Refueling Cavity Liner. One drain is west of the reactor and the other is east of the reactor and both drain to the 80'-0" elevation area.A concern with the refueling cavity is the potential of pieces of debris (e.g., a 10"x1 0" piece of sheet metal insulation jacket) migrating to one or both drains and greatly restricting the flow such that the Refueling Cavity would fill. The east part of the refueling cavity is at Elevation 114'-0", the same elevation as the reactor flange.Blockage of the east 10" drain opening would not result in an appreciable water hold up. The lower west part of the refueling cavity is deeper with greater floor area to gather Containment Spray flow which could hypothetically hold thousands of cubic feet of water if its drain were blocked.This scenario is deemed highly unlikely.
No debris generating high energy pipes are in the near vicinity of the 10" openings that drain the refueling cavity. Debris would need to be at least 10" in dimension in order to bridge the opening and cause blockage.
Smaller debris would just pass straight through. Debris would also need to be planar in order to adequately seal the opening. A crumpled piece of sheet metal would not seal the opening.
Enclosure Supplemental Response to GL 2004-02 Page 76 The reactor vessel head insulation is a hybrid design consisting of both metal and non-metallic insulation.
In the area directly above the upper-most section of the head, some of the foil sheets have been replaced with a layer of Microtherm or Min-K insulating material encapsulated in stainless steel. The total volume of fiber insulation is 10 ft 3 maximum per PVNGS Design Master Work Order (DMWO) 2513158. The reactor vessel head insulation is shielded from breaks in the main RCS loop piping by the reactor pressure vessel cavity concrete.
This insulation could be dislodged by a control element drive mechanism (CEDM) ejection or vent line break and transported to the recirculation sump via the 10 inch Refueling Cavity drains. However, the worst case quantity of fiber (10 ft 3) and RMI insulation would be bounded by other larger line breaks being evaluated (Reference 4.4). Therefore, a break in the piping at the Reactor Vessel Head is not specifically analyzed.It is assumed that the debris generated due to the LOCA will block the reactor cavity drain line in the determination of minimum containment flood level.3.m Downstream Effects -Components and Systems The downstream effects reports discussed here were prepared based on guidance in WCAP-16406, Revision 0 (Reference 4.38). These reports will be revised as necessary to implement guidance in WCAP-164061 Revision 1 with SE. This will be completed prior to the extension date of June 30, 2008, for PVNGS.3.m.1 Components Westinghouse generically performed an evaluation of the downstream impact of sump debris on the performance of the ECCS and CSS following a LOCA. This evaluation was performed in accordance with the methodology presented in WCAP-16406-P, Revision 0 (Reference 4.38) and NEI 04-07, except for conservative deviations.
An evaluation of the downstream impact of sump debris on the performance of the ECCS and CSS following a LOCA was performed in order to support Palo Verde's compliance to NRC Generic Letter (GL) 2004-02. The evaluation considers the effect of debris ingested through the containment sump screen on the following operable components:
- ECCS Orifices" CSS Nozzles* Piping and Instrument Tubing" Reactor Vessel Water Level System (RVWLS)* Reactor Vessel Internals" Nuclear Fuel The PVNGS evaluation used a conservative evaluation approach which considered larger sized debris to passing through the sump screen larger than the actual size of the holes in the sump screen. This was done to maximize the adverse Enclosure Supplemental, Response to GL 2004-02 Page 77 consequences of debris-laden fluid on ECCS and CSS components downstream of the sump. Deformable objects of up to two times a sump screen hole size of 0.09" are assumed to pass through the sump screen, and are assumed to deform to pass through any downstream clearance equal to or larger than the sump screen hole size. The new sump screen design has a nominal hole diameter of 0.083".The basis for concluding that inadequate core or containment cooling would not result from the debris-laden fluid effects is that the acceptance criteria of WCAP-16406-P are met by evaluation or by plant modifications.
3.m.2 Verification that Components are not Susceptible to PluQgging 3.m.2.1 Valves The valves were evaluated for plugging, erosion and sedimentation.
These issues are not a concern with ECCS and CSS valves. The Westinghouse downstream evaluation contained a recommendation regarding potential emergency operating procedure changes. APS is currently evaluating the recommendation.
3.m.2.2 Pumps The results of the pump hydraulic wear evaluation show that neither the ECCS nor the CSS pumps' wear gaps increase to the point of causing a hydraulic performance or pump vibration concern due to the containment sump debris (Reference 4.56).The results of the hydraulic wear calculation on the HPSI and CSS Pumps are shown in Table 29.Table 29 -Pump Hydraulic Wear Evaluation Results Pump Erosive Abrasive Total Design Increased 2X Design Wear Wear Wear Clearance Clearance Clearance (mils) (mils) (mils) (mils) (mils) (mils)HPSI 6.OE-3 14.3 14.3 23 37.3 46 CSS 6.OE-3 17.1 17.1 25 42.1 50 From WCAP-16406-P, Figure 8.1-3 (Reference 4.38), as long as the resulting wear gap clearance, including the effects of both normal and abrasive wear, is within the replacement range of two times the initial design clearance, no further evaluation is required.
From WCAP-16406-P, the change in the wear gap due to normal wear is assumed to not exceed 3 mils. Because the increased clearance for the pumps is within the 2X design clearance criteria, no effect on their hydraulic performance is expected.The CS, LPSI, and HPSI pumps utilize seal flush taken from the pump discharge and passed through a cyclone separator.
Particles passing through the cyclone separator will be carried into the seal chamber. It is expected that there would be a reduction of 70:1 or better in particles larger than 10 microns in the fluid routed to the pump seal (Reference 4.45). This reduction in debris coupled with an initial debris Enclosure Supplemental Response to GL 2004-02 Page 78 concentration of 2,000 ppm means that the flushing connection would initially be delivering fluid which has debris concentration on the order of 30 ppm. With a debris depletion constant of 0.07 per hour, within 26 hours3.009259e-4 days <br />0.00722 hours <br />4.298942e-5 weeks <br />9.893e-6 months <br /> the debris level would be comparable to the 5 Nephelometric Trubility Unit (NTU) (-ppm) of solids allowed in drinking water by the Environmental Protection Agency drinking water standards.
The use of cyclone separators on the flushing water puts the Palo Verde pumps in the category of not having debris laden flushing water pumped into the pump seals.Testing of cyclone separators installed at Exelon owned plants shows that the cyclone separators will not plug when exposed to the level of debris expected to occur during a postulated LOCA (Reference 4.61). The part numbers of the cyclone separators in Wyle Test Report WLTR 53637 dated 30 Mar 2007, are the same as the part numbers on the cyclone separators installed at PVNGS. The fiber concentration of the recirculated fluid during a postulated LOCA at PVNGS is comparable to the fiber concentration used in testing other cyclone separators.
The test report indicates that the cyclone separator was tested with more than 6 ppm of fiberglass in addition to other particulate debris constituents.
The fiber concentration is 4 times more concentrated than the 1.2 ppm concentration documented in SDOC N001 -1106-00011, Revision 1 (Reference 4.77) for.the PVNGS cyclone separators.
The Exelon cyclone separators were tested with more than 60 pounds of particulate debris in 600 gallons. The equivalent mass of debris at Palo Verde's concentration would be less than 10 pounds.Wyle Test Report WLTR 53637 is applicable to the Palo Verde Separators and shows that the Palo Verde cyclone separators are qualified to perform their design function when exposed to the debris that would be expected during a postulated LOCA (Reference 4.61). Hence, the cyclone separators installed at PVNGS will perform their intended design function while passing 4 times the expected concentration of fibrous material expected during a postulated LOCA at PVNGS.3.m.2.3 Heat Exchangers The Shutdown Cooling heat exchanger tube plugging evaluation demonstrated that the tube ID is larger than the anticipated debris particle size. Consequently, tube plugging will not occur. The heat exchanger wear evaluation demonstrated that tube failure due to erosion is not a concern., 3.m.2.4 Nozzles and Orifices The spray nozzle plugging evaluation demonstrated that the orifice bore diameter is larger than the anticipated debris particle size. Consequently, plugging will not occur. Also, for the spray nozzle wear evaluation, the nozzles will perform their design basis functions.
The orifice plugging evaluation demonstrated that no orifice bore size is smaller than the largest particle that could pass through the sump strainer, therefore, plugging is not a concern. The findings of the orifice wear evaluation concluded that the orifices will perform their design basis functions.
Enclosure Supplemental Response to GL 2004-02 Page 79 3.m.2.5 Instrument Lines The instrumentation tubing evaluation demonstrated that the transverse ECOS recirculation flow velocity meets the WCAP-16406-P acceptance criteria to prevent debris settlement.
Consequently, debris settlement does not occur and the instrumentation will perform its design basis functions.
3.m.3 Summary and conclusions of Downstream Evaluations Westinghouse (Reference 4.56) evaluated the downstream impact of sump debris on the performance of the ECCS and CSS following a LOCA at Palo Verde. The effects of debris ingested through the containment sump screen during the recirculation mode of the ECCS and CSS include erosive wear, abrasion, and potential blockage of flow paths. The smallest clearance found for the Palo Verde heat exchangers, orifices, and spray nozzles in the recirculation flow path is 0. 1875 inches for the auxiliary header containment spray nozzles; therefore no blockage of the ECCS flow path is expected with the sump screen hole size of 0.083 inches.The instrumentation tubing is also evaluated for potential blockage of the sensing lines. The transverse velocity past this tubing is sufficient to prevent debris settlement into these lines, therefore no blockage will occur.The heat exchangers, orifices, and spray nozzles were evaluated for the effects of erosive wear for an initial total debris concentration of 2046 ppm over the mission time of 30 days. The erosive wear on these components is determined to be insufficient to affect the system performance.
For pumps, the effect of debris ingestion through the sump screen on three aspects of operability, including hydraulic performance, mechanical shaft seal assembly performance, and mechanical performance (vibration) of the pump were evaluated.
The hydraulic and mechanical performances of the pump were determined to not be affected by the recirculating debris. There will be no blockage of the cyclone separators for this debris concentration.
3.m.4 Summary of Design and/or Operational Changes No design or operational changes to systems or components has been implemented at PVNGS based on the results and conclusions from the Westinghouse study.
Enclosure Supplemental Response to GL 2004-02 Page 80 3.n Downstream Effects -Fuel and Vessel 3.n.1 Reactor Vessel Internals The smallest flow clearance found in the reactor vessel internals evaluation is 0.75", which means that any replacement sump screen hole size smaller than 0.37" will not cause plugging by either deformable or non-deformable debris (Reference 4.60).The hole size in the new sump strainers is designed to be less than 0.09".3.n.2 Nuclear Fuel Calculation 2007-19863 (Reference 4.60) evaluates the deposition of debris material on the fuel rods that may potentially interfere with the transfer of heat to the coolant.This may result in excessive fuel cladding temperatures using plant specific conditions and methodology recommended in Westinghouse Calculation WCAP-16793-NP (Reference 4.58) and software transmittal OG-07-534 (Reference 4.59). The primary mode of deposition is boiling in the core. The plate-out of the chemicals that are introduced into the containment sump as a result of a LOCA in the containment building is analyzed.
These chemicals are from materials that are in the reactor coolant (boric acid and lithium hydroxide), that dissolve in the containment (i.e., aluminum, insulation, and concrete, and that are added to the recirculating water in the sump (i.e., boric acid and trisodium phosphate).
The maximum fuel cladding temperature and deposit thickness determined from the analysis is compared to the maximum acceptable temperature of 800°F and the conservative maximum deposition thickness of 50 mils (1,270 microns) as indicated in Westinghouse calculation WCAP-1 6793-NP, Section 2.4.2 and Appendix A-5 (Reference 4.58). The final calculated deposition thickness is 6.3 mils (160 microns)which is less than the recommended upper limit of 50 mils. The calculated maximum temperature of the fuel cladding over the 30 days following the LOCA is less than 3550F which is less that the recommended maximum cladding temperature of 8000F.Based on the results of Calculation 2007-19863 (Reference 4.60), the effect of the dissolved chemicals plating out on the fuel cladding is acceptable.
3.o Chemical Effects 3.o.1 Head Loss Results The head loss test results will be submitted upon finalization of the test report and analysis.
This will be completed prior to the extension date of June 30, 2008, for PVNGS.The in-vessel chemical effects analysis is described in the response to Section 3.n.3.o.2 Content Guide for Chemical Effects Enclosure Supplemental Response to GL 2004-02 Page 81 Responses to the content guidance in the letter from the NRC to NEI dated November 21, 2007, are provided in the following subsections.
Specific Content Guide chemical effects items not addressed in the following sections will be completed prior to the extension date of June 30, 2008, for PVNGS.3.0.2.1 Simplified Chemical Effects Analysis Palo Verde is not performing a simplified chemical effects analysis.
The quantity of chemicals (aluminum, calcium, and silicon) dissolved in the post-LOCA sump pool is determined using WCAP-16530-NP (Reference 4.70) and associated letters and SE.The dissolved chemical quantities along with the boron and phosphate concentrations due to the borated sump water and TSP, respectively, were provided to the screen vendor, CCI, so that prototypical chemical effects head loss tests were performed with precipitates generated in the test loop.3.0.2.2 Debris Bed Formation The debris quantities provided to the screen vendor for head loss testing are based on a break on the Reactor Coolant System (RCS) Loop 2 hot leg at the steam generator nozzle which results in the greatest quantity of debris detrimental to head loss (fiber, particulate, Thermolag) at the strainer (Reference 4.14, 4.52). The limiting breaks for Palo Verde Units 1, 2 and 3 have more (or an equivalent amount of) Nukon, coatings, and Thermolag than any other modeled break. Break selection criteria are discussed in detail in the response to Item 3a.The maximum 30-day dissolved chemical quantities (aluminum, calcium, and silicon)for Palo Verde Units 1, 2 and 3 were provided to the screen vendor for head loss testing. The maximum dissolved chemical quantity is based on the break which generates the most debris (Nukon, Alpha Cloth, and Thermolag) which can lead to chemical precipitates.
This break is the same break which leads to the most debris detrimental to head loss. However, the chemical effects analysis (Reference 4.52) is determined using the WCAP-16530-NP methodology in the chemical effects analysis (Reference 4.52) and were based on conservative debris quantities which result in 16% margin on the quantity of E-glass and 42% margin on the quantity of Thermolag particulate susceptible to dissolution in the post-LOCA environment; thus, the chemical effects analysis is conservative.
Inputs to the chemical effects analysis are described in more detail in the response to Item 3.o.2.3.Thus, the worst case debris load and dissolved chemical quantities were provided to the screen vendor for chemical effects head loss testing.3.o.2.3 Plant Specific Materials and Buffers The chemical effects analysis for Palo Verde Units 1, 2 and 3 is documented in Calculation 2006-05860 (Reference 4.52). This calculation determines both the quantity of chemicals which are dissolved in the post-LOCA sump as well as the predicted quantity of precipitate present in the post-LOCA sump using the methodology (and spreadsheet) outlined in WCAP-1 6530-NP (Reference 4.70).
Enclosure Supplemental Response to GL 2004-02 Page 82 Descriptions of the primary inputs to the chemical effects analysis are provided in the following paragraphs.
Palo Verde Units 1, 2 and 3 are similar, therefore all inputs apply to all three units unless otherwise specified.
References for all input, if not provided, can be found in Calculation 2006-05860 (Reference 4.52).The materials in containment which are exposed to the sump pool and containment spray in the post-LOCA environment and which, when dissolved, may lead to precipitates in the post-LOCA sump pool are: Nukon, Thermolag, Alpha Cloth, latent debris, exposed aluminum metal, and exposed concrete.
Some LOCA generated debris (i.e. stainless steel reflective metal insulation (RMI) and epoxy and inorganic zinc coatings) does not contribute to the quantity of dissolved chemicals in the post-LOCA sump pool since these debris types are not soluble. This is consistent with the guidance in WCAP-16530-NP (Reference 4.70).All soluble LOCA generated debris (Nukon, Thermolag, Alpha Cloth, and latent debris) is modeled as being submerged in the sump pool. Nukon and Alpha Cloth are modeled as E-glass and release primarily calcium and silicon, and a smaller amount of aluminum.
Thermolag is a particulate debris with integrated fibers which is modeled as a combination of fiberglass (E-glass) and Microtherm (silica bearing component).
Therefore, Thermolag releases mostly silica, with some calcium.Latent debris is modeled as 85% particulate concrete and 15% fiberglass, and it releases calcium, silicon, and aluminum.
The debris quantities are based on the debris generation calculation (Reference 4.4) for Palo Verde, with margin, as explained in the Section 3.o.2.2 response.
This results in conservative calcium, silicon, and aluminum releases in the post-LOCA sump pool.The following equipment in containment contains exposed aluminum metal: reactor coolant pumps, refueling equipment, movable incore detector drives, aluminum terminators, temperature switches, excore system, equipment hatch hoist assembly, Rosemount transmitters, four instruments, Dwyer Series 1800/2000 devices, four Limitorque motor operators, Fisher pressure regulators, Keene stair nosings, and the fuel transfer tube quick closure unit. The aluminum quantity is similar for all three PVNGS units.In the chemical effects analysis, aluminum metal is modeled as submerged or non-submerged.
The submerged aluminum metal in containment has a surface area of 35 ft 2 and a mass of 143 Ibm (values include 25% margin) for the chemical effects analysis.
The non-submerged aluminum metal in containment has a surface area of 632 ft 2 and a mass of 1743 Ibm (values include 5% margin).Exposed concrete is concrete which is coated with unqualified coating or coated with qualified coating within the break zone of influence (ZOI). This concrete is subject to dissolution in the post-LOCA environment.
The quantity of debris, aluminum, and concrete which dissolves is dependent upon the characteristics of both the post-LOCA sump pool and the containment spray.The sump pool properties are used to determine dissolution of submerged materials and the spray properties are used to determine dissolution of non-submerged Enclosure Supplemental Response to GL 2004-02 Page 83 materials. .The properties of the sump pool and spray which are most important are: the sump pool volume, the sump water and containment atmosphere temperature profiles, the sump and spray pH profiles, and the spray duration during the injection phase.The maximum sump pool volume is conservatively used in the chemical effects analysis since it results in the greatest quantity of dissolved material.
The material dissolution rate is dependent on the concentration of material already dissolved in the sump pool per the WCAP-16530-NP (Reference 4.70) methodology; i.e. more material dissolves when the material concentration in the sump pool is lower. The maximum sump pool mass is determined in Calculation 13-MC-SI-0016 (Reference 4.27).The sump water and the containment atmosphere temperature profiles are taken from Calculation 13-NC-ZC-0238 (Reference 4.50). This analysis determines the long-term equipment qualification (EQ) temperature (containment atmosphere and sump) and pressure profiles in containment using realistic assumptions which maximize the temperature response to design-basis mass and energy release events. The containment atmosphere and sump water temperature profiles are repeated in Figure 11.350 300 -Max Temp. -305.23 F 250 : Max Sump Temp = 234.85 F@ @ 17 sec Vapor Temp -193.6 F.... .f" /Sump Temp l16.4 F@ 24hr a 200-Vapor Temperature
-.---- Sump Temperature E 150 I.- "Vapor Temp = 161.4 F \Sump Temp = 171.7 F@d 1 E+60 oc 100 GOO 5o 0 1.00E-01 1.00O4+0 1.00E 01 1.OOE+02 1.005,03 1.00E*04 1.00E+05 1.005+06 1.00E407 Time (sec)FIGURE 11 -Containment Steam and ECCS Sump Water Temperatures The sump and spray pH profiles used in the chemical effects analysis are based on the pH of the water in RWT and on the pH of the sump water as determined in Enclosure Supplemental Response to GL 2004-02 Page 84 Calculation 13-MC-SI-0016 (Reference 4.27). The maximum sump pH is 8.1. In this pH range, larger pH values result in greater aluminum and concrete dissolution.
This pH is applicable to both the sump and spray during the recirculation phase once the TSP buffer is dissolved in the sump pool. Since the spray draws water from the Refueling Water Tank (RWT) during the injection phase, the spray pH is lower than the sump pH prior to recirculation.
The RWT boron concentration ranges from 4000 to 4400 ppm which corresponds to a pH range of 4.4 to 4.3 (Reference 4.52).In the base pH range, the lower pH results in more aluminum and concrete dissolution.
Therefore, during the injection phase, the spray pH is 4.3 from 92 seconds (when spray is initiated) to 1438 seconds (when recirculation begins)and during the recirculation phase (time greater than 1438 seconds), the spray pH is 8.1. The initial sump pH is 4.4 based on the initial sump water boron concentration of 4241 ppm as boron. Therefore, the sump pH is 4.4 from time 0 until the time at which containment spray starts (92 seconds), at which point the sump pH is conservatively modeled as 4.3 (the spray pH) until recirculation begins at 1438 seconds. As stated above, the sump pH during recirculation is 8.1 (the maximum sump pool pH). All pH values are selected to maximize the amount of material dissolution.
The event mission time also impacts the quantity of dissolved materials.
The chemical effects analysis is performed using a post-LOCA mission time of 30 days in accordance with Section 2.0 of the NRC Safety Evaluation (SE) on NEI 04-07 (Reference 4.30). Therefore, the chemical quantities dissolved in the sump and the predicted precipitate quantities are based on a 30 day event duration.
Containment spray is conservatively modeled as remaining on for 30 days post-LOCA which maximizes dissolution of non-submerged materials.
3.o.2.4 Chemical Effects Testinq Plant specific chemical effects testing has been performed by the screen vendor, CCI. CCI has performed laboratory bench tests and head loss tests with precipitates in the test loop. Questions on the CCI chemical effects testing methodology were presented at the public meeting on GSI-1 91, October 24, 2007 with respect to the uncertainty in the chemical precipitate properties and the repeatability of the process.CCI has performed lab bench tests to address these questions and confirm that the chemical testing methodology employed by CCI is appropriate.
3.o.2.5 Method of AddressinQ Plant-Specific Chemical Effects The methodology in WCAP-16530-NP (Reference 4.70) is used to determine the quantity of chemicals which dissolve in the post-LOCA sump for Palo Verde.3.o.2.6 AECL Model The AECL model is not used by Palo Verde.
Enclosure Supplemental Response to GL 2004-02 Page 85 3.o.2.7 WCAP Base Model 3.o.2.7.1 Deviations from WCAP Base Model The WCAP-16530-NP base model spreadsheet was originally issued in February 2006, along with the WCAP document (Reference 4.70). Following the initial issuance, errors were discovered in the spreadsheet as described in Letter WOG-06-102 (Reference 4.70.1) and a revised spreadsheet was issued on March 17, 2006 via Letter WOG-06-103 (Reference 4.70.2). Additional errors in the spreadsheet were discovered and were described in Letter OG-06-232 (Reference 4.70.3). These errors were corrected, and a revised spreadsheet was issued on August 7, 2006, via Letter OG-06-255 (Reference 4.70.4). Following this issuance of the spreadsheet, one additional error in the spreadsheet was discovered as described in Letter OG-06-273 (Reference 4.70.5), dated August 28, 2006.However, no revision to the WCAP spreadsheet was issued following the issuance of Letter OG-06-273 (Reference 4.70.5).The spreadsheet used in Calculation 2006-05860 (Reference 4.52) is based on that issued via Letter OG-06-255 (Reference 4.70.4); however, the spreadsheet was modified to address the error described in Letter OG-06-273 (Reference 4.70.5).The error correction involved changing a cell reference in several worksheets as is described in Letter OG-06-273 (Reference 4.70.5). Letter OG-06-273 (Reference 4.70.5) states that this error impacts plants which use TSP for a buffer;therefore, it did impact Palo Verde.In addition, sheets were added to the WCAP-16530-NP base model spreadsheet to explicitly address particulate concrete separately from exposed concrete.
These sheets were added since the WCAP-16530-NP spreadsheet modeled the dissolution of exposed concrete as a function of surface area, not thickness.
Hence, dissolution of exposed concrete continues throughout the duration of the event based on the implicit assumption that there is an unlimited quantity of concrete.
Given the limited mass of particulate concrete, the assumption of indefinite dissolution was not appropriate.
Therefore, separate sheets were added such that dissolution of particulate concrete continued only to the point at which all particulate concrete was dissolved.
Other than the modifications mentioned above, no other changes to the WCAP base model spreadsheet were made in the Palo Verde chemical effects analysis.
Also, no plant-specific refinements were incorporated into the WCAP base model spreadsheet.
Enclosure Supplemental Response to GL 2004-02 Page 86 3.o.2.7.2 Precipitate Quantities The maximum quantities of dissolved chemicals in the post-LOCA sump are determined in Calculation 2006-05860 (Reference 4.52). The dissolved chemical quantities are conservatively lower than the chemical quantities tested during head loss testing performed by the screen vendor, CCI. Both values are presented in the Table 30. The values presented in the table below are the nominal (100%) quantities of chemicals which dissolve in the post-LOCA sump due to material dissolution over 30 days following a LOCA. The quantity used as a basis for the CCI head loss tests presented in Table 30 is the "100% chemical load." However, chemical effects head loss tests were performed with up to 140% of the nominal chemical load.Table 30 -Dissolved Chemical Quantities Dissolved Quantity Calculated Dissolved Quantity Used as Chemical in Chemical Effects Analysis Basis for CCI Head Loss Tests Aluminum 19.2 kg as Al 19.4 kg as Al Silica 53.8 kg as Si0 2 54.0 kg as Si0 2 Calcium 10.6 kg as Ca 10.8 kg as Ca In addition to the dissolved chemical quantities, the chemical effects analysis also predicts the quantity of precipitate which will form over 30 days following a LOCA due to the dissolved chemicals.
These quantities are provided in the Table 31.These quantities were not used by the screen vendor since the precipitates were obtained by chemical injection into the test loop.Table 31 -Mass of Chemical Precipitate Precipitate Mass of Precipitate Sodium Aluminum Silicate, NaAlSi 3 0 8 78.2 kg Aluminum Oxyhydroxide, AIOOH 24.7 kg Calcium Phosphate, Ca 3 (PO4)2 27.4 kg 3.0.2.8 WCAP-16530-NP Refinements The Palo Verde chemical effects analysis, Calculation 2006-05860 (Reference 4.52), does not utilize any of the refinements described in WCAP-1 6785-NP (Reference 4.53). Specifically, the analysis does not model aluminum passivation, or credit solubility of phosphates, silicates, or aluminum alloys.The type and amount of predicted plant precipitates based on WCAP-16530-NP (Reference 4.70) analysis are provided in the response to Item 3.o.2.7.2.
Enclosure Supplemental Response to GL 2004-02 Page 87 3.o.2.9 Solubility of Phosphates, Silicates and Al Alloys 3.o.2.9.1 Refinements (plant-specific inputs) to the base WCAP-1 6530 Model The Palo Verde chemical effects analysis, Calculation 2006-05860 (Reference 4.52), does not utilize any of the refinements described in WCAP-16785-NP (Reference 4.53).3.0.2.9.2 Inhibition of Aluminum that is not Submerged The Palo Verde chemical effects analysis, Calculation 2006-05860 (Reference 4.52), does not utilize any of the refinements described in WCAP-16785-NP (Reference 4.53). Specifically, the analysis does not model aluminum passivation.
3.o.2.9.3 Solubility of Phosphates, Silicates and Al Alloys The Palo Verde chemical effects analysis, Calculation 2006-05860 (Reference 4.52), does not utilize any of the refinements described in WCAP-16785-NP (Reference 4.53). Specifically, the analysis does not credit solubility of phosphates, silicates, or aluminum alloys.3.o.2.9.4 Type and Quantity of Precipitates The Palo Verde chemical effects analysis, Calculation 2006-05860 (Reference 4.52), does not utilize any of the refinements described in WCAP-1 6785-NP (Reference 4.53). The type and amount of predicted plant precipitates based on WCAP-16530-NP analysis are provided in the response to Item 3.o.2.7.2.
3.p Licensing Basis 3.p.1 General Description of ChanQes Activities are currently underway to ensure that ECCS and CSS recirculation functions under debris loading conditions at PVNGS Units 1, 2 and 3, will be in full compliance with the regulatory requirements listed in the Applicable Regulatory Requirements section of Generic Letter 2004-02 by June 30, 2008. Full compliance will be achieved through analysis, mechanistic evaluations, modifications to increase the available sump screen area, changes to the plant to reduce the potential debris loading for the containment recirculation sump strainers, and programmatic and process controls to ensure continued compliance.
Fiberfrax insulation has been removed from PVNGS Units 1, 2, and 3. New, larger sump strainers have been installed in Units 1 and 3. New strainers will be installed in Unit 2 during the 2R14 refueling outage in Spring 2008. The new strainers increase the available screen area from 210 ft 2 to 3,142 ft 2 in each of the two containment sumps. The new strainers will occupy the same foot print as the existing strainers.
Enclosure Supplemental Response to GL 2004-02 Page 88 The UFSAR will be updated with these changes in accordance with 10 CFR 50.71(e)following implementation of the design changes. The changes were identified as part of the design change preparations prior to implementation of the changes in the first PVNGS unit. The description of the replacement strainers has been added to the UFSAR with Licensing Document Change Request (LDCR) 06-F036.
4.0 REFERENCES
Various calculations are referenced above that are associated with a specific system/topic.
Additional documents used in the development of this study are as follows: 4.1 SDOC MN725-A00153, Revision 0, "Turbine-Generator Final Report 105% Core Thermal Uprate Study" 4.2 SDOC N001-1 106-00007, Revision 0, "Unit 2 Debris Walkdown Report" 4.3 Calculation 13-CC-ZC-0197, Revision 6, "Containment Bldg. Misc. Structures Part 2" 4.4 SDOC N001-1106-00002, Calculation 2005-06160, Revision 2, "Debris Generation Due to LOCA within Containment for Resolution of GSI-191" 4.5 SDOC N001-1106-00022, Revision 0, "Walkdown Report for Evaluating Fibrous Sources Inside PVNGS-1 Containment," Revision 1 4.6 SDOC N001-1106-00024, Revision 0, "Walkdown Report for Evaluating Fibrous Sources Inside PVNGS-3 Containment," Revision 0 4.7 SDOC AN449-A00090, Revision 1, "Unit 1 Unqualified Coatings Walkdown Report" 4.8 SDOC AN449-A00086, Revision 1, "Unit 2 Unqualified Coatings Walkdown Report" 4.9 SDOC AN449-A00091, Revision 1, "Unit 3 Unqualified Coatings Walkdown Report" 4.10 SDOC N001-1106-00021, Revision 0, "Walkdown Report for Evaluating Latent Debris inside PVNGS Unit 1 Containment for Resolution of GSI-1 91," Revision 1 4.11 SDOC N001-1106-00008, Revision 0, "Walkdown Report for Evaluating Latent Debris inside PVNGS Unit 2 Containment for Resolution of GSI-1 91," Revision 0 4.12 SDOC N001-1106-00023, Revision 0, "Walkdown Report for Evaluating Latent Debris inside PVNGS Unit 3 Containment for Resolution of GSI-1 91," Revision 1 4.13 SDOC N001-1106-00001, Revision 0, Calculation 2005-06305, "Latent Debris Generation due to LOCA within Containment for Resolution of GSI-1 91," Revision 1 4.14 SDOC N001-1106-00003, Calculation 2005-09080, "Post LOCA Debris Transport for Resolution of GSI-191," Revision 1 Enclosure Supplemental Response to GL 2004-02 Page 89 4.15 Calculation 13-MC-SI-0804, Revision 6, "Containment Building Water Level During LOCA" 4.16 SDOC N001-1106-00004, Revision 0, "GSI-191 Chemical Effects and Margin Evaluation," Revision 0 4.17 NRC letter dated 12/13/2006, "PVNGS Unit 2 -Approval of GL 2004-02 Extension Request" 4.18 SDOC N001-1 106-00027, Revision 0, " Q00384747, CCI Small-Filter Performance Test Specification, Revision 3" 4.19 SDOC N001-1106-00028, Revision 0, "CCI Large-Filter Performance Test Specification," Revision 3 4.20 SDOC N001-1106-00040, Revision 0, "Proof of Absence of Air Vortices above Strainers," Revision 2 4.21 SDOC NOO1-1106-00220, Revision 0, "CCI Large-Scale Strainer Performance Test," Revision 4 4.22 SDOC N001-1106-00032, Revision 0, "Structural Analysis of a ECCS Strainer Standard Module Cartridge," Revision 4 4.23 SDOC N001-1106-00038, Revision 0, "Seismic Analysis Report Strainer Subfloor," Revision 1 4.24 SDOC N001-1106-00037, Revision 0, "Structural Analysis of Strainer Module and Support Structure," Revision 2 4.25 SDOC N001-1 106-00033, Revision 3, "CCI Fabrication Drawing -Strainer," Revision F 4.26 Calculation 13-NC-ZC-0202, Revision 10, "Post-LOCA Hydrogen Generation" 4.27 Calculation 13-MC-SI-0016, Revision 4, "Tri-Sodium Phosphate Basis Calculation" 4.28 Safety Evaluation by the Office of Nuclear of Reactor Regulation Related to NRC Generic Letter 2004-02, Nuclear Energy Institute Guidance Report (Proposed Document Number NEI 04-07), "Pressurized Water Reactor Sump Performance Evaluation Methodology," issued December 6, 2004 4.29 SDOC N001-1 106-00029, Revision 0, "CCI Small Filter Performance Test Report" 4.30 Nuclear Energy Institute (NEI) Document Number NEI 04-07, Revision 0,"Pressurized Water Reactor Sump Performance Evaluation Methodology," dated December 2004.
Enclosure Supplemental Response to GL 2004-02 Page 90 4.31 Specification 13-MN-1003, Revision 0, "Emergency Recirculation Sump Strainers" 4.32 Calculation 13-MC-SI-0017, Revision 6, "Safety Injection System Interface Requirements Calculation" 4.33 Calculation 13-MC-SI-0018, Revision 7, "Containment Spray System Interface Requirements Calculation" 4.34 NRC Regulatory Guide 1.82 "Water Sources for Long-Term Recirculation Cooling Following a Loss-of-Coolant Accident," Revision 3 4.35 Procedure 38DP-OMI01, Revision 8, "Control of Painting and Coating Operations" 4.36 Procedure 81 DP-OAP02, Revision 2, "PVNGS Coatings Program" 4.37 Westinghouse LTR-CSA-05-21, "Downstream Effects Evaluation to Support the Resolution of GSI-191 for Palo Verde Nuclear Generating Station," August 30, 2005 4.38 Westinghouse Document WCAP-1 6406-P, "Evaluation of Downstream Sump Debris Effects in Support of GSI-191, June 2005 4.39 Procedure 40ST-9ZZ09, Revision 18, "Containment Cleanliness Inspection" 4.40 Procedure 30DP-9MP03, Revision 11, "System Cleanliness and Foreign Material Exclusion Controls" 4.41 SDOC N001 -1106-00219, Revision 0, "Unit 2 Fiber Walkdown Report," Revision 0 4.42 CCI Report 680/1380, "Chemical Effect Test," Revision 0 (Preliminary) 4.43 CCI Calculation 3SA-096.063, "Head Loss Calculation," Revision 0 (Preliminary) 4.44 SDOC N001 -1106-00176, Revision 0, "Evaluation of the Maximum Allowable Pressure Difference," Revision 1 4.45 SDOC N001-1106-00226, Revision 0, Calculation 2007-22843, "Evaluation of Palo Verde ECCS Pump Seal Based on WCAP-16406-P," Revision 1 4.46 Calculation 13-NC-ZC-0208, Revision 9, "Passive Heat Sinks for Containment P/T Analysis" 4.47 Calculation 13-NC-ZC-0237, Revision 4, "Maximum Passive Heat Sink for Hydrogen Generation
& ECCS Evaluation" 4.48 NUREG/CR-6874, "GSI-191:
Experimental Studies of Loss-of-Coolant-Accident-Generated Debris Accumulation and Head Loss with Emphasis on the Effects of Calcium Silicate Insulation," April 2004 4.49 Calculation 13-MC-SI-0309 Revision 5, "Emergency Pump Screen Blockage" Enclosure Supplemental Response to GL 2004-02 Page 91 4.50 Calculation 13-NC-ZC-0238, Revision 3, "System Design LOCA Analysis" 4.51 SDOC N001-1106-00033, Revision 3, CCI Calculation 3SA-096043, "CCI Fabrication Drawing-Strainer," Revision F 4.52 Calculation 2006-05860, "Post-LOCA Chemical Effects Analysis in Support of GSI-191," Revision 0 4.53 Westinghouse Document WCAP-16785-NP, "Evaluation of Additional Inputs to the WCAP-16530-NP Chemical Model," Revision 0, May 2007 4.54 Westinghouse Document WCAP-16568-P, "Jet Impingement Testing to Determine the Zone of Influence (ZOI) for DBA-Qualified/Acceptable Coatings," Revision 0 4.55 Procedure 40EP-9EO03, Revision 24, "Loss of Coolant Accident" 4.56 N001-1106-00012, Revision 0, "Palo Verde Sump Debris Downstream Effects Evaluation for ECCS Equipment," Revision 1 4.57 AO-AN-0449, Revision 4, "Specification for Coating Activities at Palo Verde Nuclear Generating Station" 4.58 Westinghouse Document WCAP-1 6793-NP, "Evaluation of Long-Term Cooling Considering Particulate, Fibrous, and Chemical Debris in the Recirculating Fluid," May 2007 4.59 OG-07-534, "Transmittal of Additional Guidance for Modeling Post-LOCA Core Deposition with LOCADM Document for WCAP-1 6793-NP (PA-SEE-0312)," December 14, 2007 4.60 SDOC N001-1106-00223, Revision 0, Calculation 2007-19863, "Post-LOCA Fuel Deposition Analysis in Support of GSI-191" 4.61 SDOC N001-1106-00225, Revision 0, Calculation 2008-00603, "Evaluation of Effects of Debris on the Palo Verde ECCS Pump Seal Cyclone Separators" 4.62 Calculation 13-NC-ZC-0232, Revision 9, "Loss of Coolant Accident Pressure and Temperature Containment Analysis for Limiting Case" 4.63 Specification 13-AN-0448, Revision 0, "Installation Specification for the Control of Transient Material" 4.64 NUREG/CR-3616, "Transport and Screen Blockage Characteristics of Reflective Metallic Insulation Materials" 4.65 NUREG/CR-6772, "GSI-191:
Separate-Effects Characterization of Debris Transport in Water" Enclosure Supplemental Response to GL 2004-02 Page 92 4.66 NUREG/CR-6224, "Parametric Study of the Potential for BWR ECCS Strainer Blockage Due to LOCA Generated Debris" 4.67 SDOC N001-1106-00176, Revision 0, Calculation 3SA-096.043, "Evaluation of the Maximum Allowable Pressure Difference," Revision 1 4.68 81DP-OZZ01, Revision 12, "Civil System, Structure, and Component Monitoring Program" 4.69 EDC 2006-00486 to Specification 13'-MN-0169, Revision 9 4.70 WCAP-16530-NP, "Evaluation of Post-Accident Chemical Effects in Containment Sump Fluids to Support GSI-191," Revision 0, dated February 2006, supplemented by the following letters: 4.70.1 Letter WOG-06-102, "Distribution of Errata to WCAP-16530-NP, "Method for Evaluating Post-Accident Chemical Effects in Containment Sump Fluids" (PA-SEE-0275)," dated March 17, 2006 4.70.2 Letter WOG-06-103, "Distribution of WCAP-16530-NP, " Method for Evaluating Post-Accident Chemical Effects in Containment Sump Fluids" (PA-SEE-0275)," dated March 17, 2006 4.70.3 Letter OG-06-232, "PWR Owners Group Letter Regarding Additional Error Corrections to WCAP-16530-NP (PA-SEE-0275)," dated June 17, 2006 4.70.4 Letter OG-06-255, "PWR Owners Group Letter Releasing Revised Chemical Model Spreadsheet From WCAP-16530-NP (PA-SEE-0275)," dated August 7, 2006 4.70.5 Letter OG-06-273, "PWR Owners Group Method Description of Error Discovered August 16, 2006 in Revised Chemical Model Spreadsheet (PA-SEE-0275)," dated August 28, 2006 4.71 NUREG/CR-6808, "Knowledge Base for the Effect of Debris on Pressurized Water Reactor Emergency Core Cooling Sump Performance" 4.72 NUREG/CR-6773, "GSI-191:
Integrated Debris-Transport Tests in Water Using Simulated Containment Floor Geometries" 4.73 Continuum Dynamics, Inc. (C.D.I.) Report No. 96-06, Revision A, "Air Jet Impact Testing of Fibrous-and Reflective Metallic Insulation." (Included in Volume 3 of BWR URG, NEDO-32686-A, Reference 4.)4.74 Continuum Dynamics, Inc. (C.D.I.) Report No. 95-09, Revision 4, "Testing of Alternate Strainers with Insulation Fiber and Other Debris." (Included in Volume 2 of BWR URG, NEDO-32686-A, Ref. 4.76)
Enclosure Supplemental Response to GL 2004-02 Page 93 4.75 NUREG/CR-2982, "Buoyancy, Transport, and Head Loss of Fibrous Reactor Insulation" 4.76 GE Document NEDO-32686-A, DRF A74-00004, Class I, Volume 1, "Utility Resolution Guide for ECCS Suction Strainer Blockage," dated October 1998 4.77 N001-1106-00011, Revision 1, "Palo Verde Units 1, 2, 3, GSI-191 Downstream Effects Debris Ingestion," Revision 2 4.78 30DP-OWM12, Revision 17, Housekeeping
5.0 APPENDICES
Appendix A -Index of RAI Responses Appendix B -Evaluation of "Straw Effect" at Containment Sump Enclosure Supplemental Response to GL 2004-02 APPENDIX A Page 1 of 1 INDEX OF RAI RESPONSES GL Response Subsections RAI Questions 1.0 Overall Compliance
2.0 General
Description of and Schedule for Corrective Action 3.0 Methodology for Demonstrating Compliance
- a. Break Selection 40, 41 b. Debris Generation/ZOI 42 (excluding coatings)c. Debris Characteristics 30, 32, 39, 42 d. Latent Debris 31, 32, 39 e. Debris Transport 47 f. Head Loss and Vortexing 43, 44, 46 g. Net Positive Suction Head 7, 8, 10, 12, 45 (NPSH)h. Coating Evaluation 25, 37 i. Debris Source Term 25, 33, 34, 37 Refinements
- j. Screen Modification Package 36, 38 k. Sump Structural Analysis 36 I. Upstream Effects 43, 45 m. Downstream Effects -14, 35 Components and Systems n. Downstream Effects -Fuel and Vessel o. Chemical Effects 5, 7, 8, 10, 11, 12,14 p. Licensing Basis RAI Questions 2, 3, 4, and 6 The ICET tests are not specifically used by APS for the analyses to evaluate the chemical effects to validate sump strainer sizing. APS has performed plant specific chemical effects testing for evaluation.
Description of the plant specific debris types and debris quantities generated is provided in the response to Section 3.b and the description of the chemical effects evaluations are provided in the response to Section 3.o. The chemical effects test report and head loss analysis will be completed prior to the PVNGS extension date of June 30, 2008.RAI Question 9 Palo Verde uses TSP to buffer the containment pool pH following a LOCA. There are no plans to change to a different chemical as the buffering agent. APS has removed the Fiberfrax insulation, which was a significant debris source.
Enclosure Supplemental Response to GL 2004-02 APPENDIX B Page 1 of 2 EVALUATION OF "STRAW EFFECT" AT CONTAINMENT SUMP Background Discussions at the CCI User's Group meeting held June 28 -June 29, 2007, included discussion of an effect of potential air drawn into the suction pipe from pipes that are submerged in the sump pit on one end and are open to the containment air environment on the other end.If the pressure required to drain the water in such a line is less than the differential pressure across the sump strainer, then air will be ingested in the suction pipe via the partially submerged pipes. This issue needs to be reviewed for applicability to Palo Verde.Evaluation Based on review of the Palo Verde Containment sump configuration, there are: (a) two pipes-14" LTOP sparger lines, (b) two valve stem extension pipes-sump containment isolation valve stem extension protector pipes, and (c) one conduit (with one end submerged in the sump pit and the other end above the minimum containment flood level) -3/4" conduit for the sump temperature element.(a) The 14" LTOP sparger line is open to the sump pit via holes in the wall of the pipe to distribute the force of the discharge fluid. This line is closed above the flood water level as this line is the discharge line from the shutdown cooling relief valve. (References 1, 2, 3, 4,5,6,7)(b) The valve stem extension cover is open at the bottom in the sump pit. This pipe is bolted to the valve body bracket. At the top, this pipe is bolted to the valve actuator.
The actuator gear box compartment is a bolted enclosure that is well sealed with gaskets and o-rings. Since the top of the stem extension cover is enclosed and sealed using gaskets and o-rings, the draw down concern is not applicable. (References 8, 9, 10, 11, 15)(c) The 3/4" conduit for the sump pit temperature element is routed through the strainer subfloor.
The temperature elements use a conduit seal below the containment flood level that is qualified for the containment sump environment.
The TE elements are procured and installed as Q Class instruments and qualified for the sump environment.
Therefore, the conduit does not need to be considered as a potential air entrainment source.(
References:
12, 13, 14)Conclusion The review of the pipes and conduit that penetrate the strainer subfloor has determined these components to be adequately closed or sealed to prevent air ingestion via these pipes and conduit.
Enclosure Supplemental Response to GL 2004-02 APPENDIX B Page 2 of 2 References
- 1. 01-M-SIP-0002 Rev 32, P & I Diagram Safety Injection and Shutdown Cooling System 2. 02-M-SIP-0002 Rev 26, P & I Diagram Safety Injection and Shutdown Cooling System 3. 03-M-SIP-0002 Rev 31, P & I Diagram Safety Injection and Shutdown Cooling System 4. 01-P-SIF-0151 Rev 1, Ctmt Bldg Iso Sfty Inj Sys Shtdwn CIg Overpress Relief 5. 02-P-SIF-0151 Rev 0, Ctmt Bldg Iso Sfty Inj Sys Shtdwn CIg Overpress Relief 6. 03-P-SIF-0151 Rev 0, Ctmt Bldg Iso Sfty Inj Sys Shtdwn CIg Overpress Relief 7. N001-1 106-00033 Rev 3, CCI Fabrication Drawing-Strainer
- 8. N001 -1104-00282 Rev 10, 24" Class 150 Wafer Valve Assy SI-673,675 V-CE-1 6690 30JN82 9. N001 -1104-00274 Rev 8, 24" Class 150 Wafer VIv Assy SI-UV-673
& 675 10. N001-1104-00275 Rev. 8, 24" Class 150 Wafer VIv Assy SI-UV-673,675
- 11. 13-P-ZCG-1 12 Rev 15, Containment Building Misc Embedded Pipe Details Below EL. 80'-0" 12. 13-E-ZCC-0074 Rev 25, Containment and MSSS Bldg. Post LOCA Devices Conduit Seal Requirement.
- 14. J556-00086 Rev. 3, General Purpose Head / Hex Nipple / Sensor/ Mounting Bracket 15. VTD-L200-00006 Rev 3, Instruction and Maintenance Manual for Limitorque Type HBC (PUB. #HBCI-90).