ML20195E139
| ML20195E139 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/12/1998 |
| From: | Scherer A SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-98-04, GL-98-4, NUDOCS 9811180247 | |
| Download: ML20195E139 (8) | |
Text
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$OOffit RN CAlllORNI A A. Edward Scherer LJ EDISON ML,m an umos nnnuun u-own November 12, 1998 J
United States Nuclear Regulatory Commission Attention: Document Control Desk Washington DC 20555-0001 Gentlemen:
Subject:
NRC Generic Letter 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. San Onofre Nuclear Generating Stations Units 2 and 3 This letter provides, as an enclosure, the information requested in Generic Letter 98-04.
Information is provided which includes the evaluation requested of the San Onofre Units 2 and 3 programs for ensuring that Service Level 1 protective coatings inside containment do not detach from their substrate during a design basis Loss of Coolant Accident and interfere with the operation of the Emergency Core Cooling System and the safety-related Containment Spray System.
The information provided in this response was based on the Pressurized Water Reactor template developed by NEI to assist in responding to Generic. Letter 98-04.
If you have any questions or would like additional information on this subject, please let me know.
Very truly yours, i '... e(U
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Enclosure cc:
E. W. Merschoff, Regional Administrator, NRC Region IV J. A. Sloan, NRC Senior Resident Inspector, San Onofre Units 2 & 3 J. W. Clifford, NRC Project Manager, San Onofre Units 2 and 3 h
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ENCLOSURE Generic Letter 98-04 Response San Onofre Units 2 and 3 Item (1)
A summary description of the plant-specificprogram orprograms impi riented to ensure that Service Level 1 protective coatings usedinside the containment are procured, applied, and maintained in compliance with applicable regulatay requirements and the plant-specipc licensing basisfor thefacility. Include a discussion ofhow theplant-specificprogram meets the applicable criteria of10 CFR Part 50, Appendix B, as wellas information regarding any applicable standards, plant-specipcprocedures, or other guidance usedfor: (a) controlling the procurement afcoatings andpaints used at thefacility, (b) the quahfication testing ofprotective coatings, and (c) surface preparation, application, surveillance, and maintenance actwiticsfor protective coatings. Maintenance activities involve reworking degraded coatings, removu:g degraded coatings to sound coatings, correctlypreparing the surfaces, applying new coatings, and verifying the quality of the coatings.
Response to Item (1):
Southern California Edison has implemented controls for the procurement, application, and maintenance of Service Level 1 protective coatings used inside the containment in a manner that is consistent with the licensing basis and regulatory requirements applicable to San Onofre Units 2 and 3. The requirements of 10 CFR Part 50, Appendix B are implemented through specification of appropriate technical and quality requirements for the Service Level I coatings program which includes ongoing maintenance activities.
For San Onofre Units 2 and 3, Service Level I coatings used in containment that are procured, applied and maintained by Southern California Edison or their contractor comply with ANSI N101.2 and Regulatory Guide 1.54, except as discussed below. Protective coatings used inside containment, excluding components limited by size and/or exposed surface area, are demonstrated to withstand the design basis accident conditions via compliance with ANSI N101.2 and Regulatory Guide 1.54, except as identified in Updated Final Safety Analysis Report (UFS AR) paragraph 3A.I.54 (
Reference:
UFSAR, Section 6.1.2.1). This UFS AR paragraph addresses San Onofre 2 and 3's use of unqualified coatings ihr the Nuch up and repair of ferrous metals inside l
containment as long as these surfaces were predously coated with qualified coating material and the repair or touch up area is limited to less than 30 square inches. This UFSA.R section also j
states that such repair and touch up activities need not be consistent with Regulatory Guide 1.54 l
with respect to surface preparation and documentation (
Reference:
UFSAR, Section 3A.l.54).
Specifically, coatings used inside the San Onofre 2 and 3 containments meet the guidance of ANSI N101.2 and Regulatory Guide 1.54, except as discussed above. Adequate assurance that the applicable requirements for the procurement, application, inspection, and maintenance of Service Level I coatings are implemented is provided by procedures and programmatic controls, approved under the Southern California Edison Quality Assurance Program. Southern California
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f ENCLOSURE Edison is reviewing the guidance provided in EPRI TR-109937 " Guideline on Nuclear Safety-Related Coatings" and has formed a multi discipline group to review the existing coating programs for San Onofre 2 and 3 and to inaintain and enhance the coating programs using EPRI l
TR-109937 as a guide.
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Service Level I coatings used for new applications or repair / replacement activities are a.
procured from a coating supplier (s) with a quality assurance program meeting the applicable requirements of 10 CFR Part 50, Appendix B. The applicable technical and quality l
requirements that the coating supplier is to meet are specified by Southern California Edison in procurement documents. Acceptance activities are conducted in accordance with procedures that are consistent with ANSI N45.2 guidance (e.g., receipt inspection, soure surveillance, etc.). These technical and quality requirements, combined with appropriate acceptance activities, provide adequate assurance that the coatings received meet the specifications.
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The test reports of Service Level I coatings used inside containment have been reviewed in response to this Generic Letter and have been found to meet the applicable specifications contained in the standards and regulatory commitments referenced above. Southern California Edison purchases new Service Level I coatings from 10 CFR Part 50, Appendix B qualified suppliers who provide the required certificates of conformance for Southern 1
California Edison's review. The certificates of conformance for Service Level I coatings are I
reviewed for acceptance before material use.
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The surface phparation, application and surveillance during installation of Service Level I
'l coatings used for new applications or repair / replacement activities inside containment meet the applicable portions of the standards and regulatory commitments referenced above.
Documentation of completion of these activities is performed consistent with the applicable guidance and/or requirements.
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San Onofre Units 2 and 3 conducts condition assesments of Service Level I coatings inside i
containment. As degraded or nonconforming coatings are identified, they are evaluated and repair or replacement is scheduled, as necessary, using the San Onofre Units 2 and 3 Action Request (AR) Program. An example of a degraded or nonconforming condition was the prestaged, seismically-restrained scaffolding stored inside the San Onofre containments to provide eflicient outage support. Nonconforming scaffolding coating was identified, an AR was written, and an operability assessment was performed and found Unit 3 acceptable "as is." Since Unit 2 was shut down, a temporary enclosure for the Unit 2 scaffolding was erected to satain the unqualified l
coating. To be conservative, uncoated scaffolding has been installed i T it 3 and all of the n
l noncomforming scaffolding in Unit 2 is planned to be replaced by un;ca e scaffolding during the Unit 2, Cycle 10 refueling outage. A second example is a selfidentified c adition that replacement parts and components intended for installation inside contain* <ent may be procured, i
and, therefore, installed without assurance that coatings used in their ma.ufacture be Design Basis Accident (DBA) qualified in accordance with the standards listed m UFSAR Section j
6.1.2.1. An AR was written to review the procurement of replacement parts and components intended for installation inside containment and is currently being evaluated.
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ENCLOSURE Th'e condition assessments, and the resulting repair / replacement activ; ties, assure that the amount of Service Level I coatings which may be susceptible to detachment from the substrate during a Loss ofCoolant Accident (LOCA) event is minimized. As previously noted, Southern California Edison is evaluating the guidance contained in the EPRI coatings guideline.
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Item (2)
Information demonstrating compliance with item (i) or item (ii):
(i) Forplants with licensing-basis requirementsfor tracking the amount of unquahfied coatings inside the containment andfor assessing the impact ofpotential coating debris 9
on the operation ofsafety-relatedSSCs during apostulated design basis LOCA the following information shall be provided to demonstrate compliance:
(a) The date andfindings of the last assessment ofcoatings, and the planned date of the next assessment ofcoatings.
(b) ' The limitfor the amount of unquahfiedprotective coatings allowedin the containment and how this limit is determined. Discuss any conservatism in the method used to determine this amount.
i (c) Ifa commercial-grade dedicationprogram is being usedatyourfacilityfor dedicating commercial-grade coatingsfor Service Level 1 applications inside the containment, discuss how the program adequately quahfies such a coatingfor Service Level 1 service. Identify which standards or other guidance are currently
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being used to dedicate containment coatings atyourfacility; or, Response to item (2)(i):
i This item is not applicable. San Onofre Units 2 and 3 do not have the above licensing-basis requirements.
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(ii) Forplants without the above licensing-basis requirements, information shall be provided to demonstrate compliance with the requirements of10CFR50.16b(5), "Long-term i
cooling" and thefunctional capability of the safety-related CSS as setforth in your
. licensing basis. If a licensee can demonstrate this compliance without quantifying the amount of unquahfied coatings, this is accepichte.
i Response to item (2)(ii):
l The following description and referenced materials describe the licensing basis for San Onofre Units 2 and 3 relative to conformance with 10CFR50.46b(5),"Long-term cooling." Specifically, the following describes San Onofre Units 2 and 3's ability to provide extended decay heat removal, including related assumptions for debris that could block containment emergene sump
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l ENCLOSURE screens., '
The Containment Emergency Sump is a collecting reservoir designed to provide an adequate supply of water, with a minimum amount of particulate matter, to the Containment Spray System
-(CSS) and the Safety Injection System. The safety injection and containment spray pumps initially draw water from the Refueling Water Storage Tank (RWST). When water from the LOCA break
. or containment spray reaches the containment floor, it drains towards the containment sump where it remains until the recirculation mode begins. When the RWST inventory is down to its minimum volume, a rechmation actuation signal (RAS) is generated. The RAS opens the i
l containment sump isolation valves. During the recirculation mode, the safety injection and j
containment spray pumps draw from the emergency sump, i
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- San Onofre Unit? 2.r.d 3 Emergency Core Cooling System (ECCS) pumps, with 24 inch j
containmea sump suction lines, do not contain in-line strainers (
Reference:
UFSAR, Section 6.2, i
Figures 6.2-52, Sheets 1-4). Debris is prevented from entering the sump and intakes by a trash rack and screens with an internal grating around the suction pipe that suppresses the formation of vortexes. The innermost sump intake screen has a mesh sizing of 0.090 inch based on the minimum core channel opening through which the safety injection system must pump. The sizing also ensures that the performance of the containment spray system will not be impaired since the i
spray pumps and nozzles are capable of passing particles of up to 0.25 inch size (Referencei UFSAR, Section 6.2.2.1.2.5).
To meet the guidance of Reguletmy Guide 1.79 and to ensure that this containment sump configuration would fully satisfy any demands put on it by the worst case LOCA, San Onofre contracted with Western Canada Hydraulic Laboratories LTD io complete model studies, which included testing, on the containment sump design. The purpose of the tests was to determine the adequacy of design during a transient. From these tests, Western Canada Hydraulic Laboratories LTD concluded that the containment sump design was adequate and could support a 50 percent i
,l' blockage of the screens (References I and 2).
San Onofre 2 and 3 evaluated the ability of the ECCS and the CSS to meet their licensing bases with the presence ofloose coatings and debris in a post-LOCA environment (Reference 3). The L
evaluation concluded that the low water approach velocities (0.13 feet /second or less)
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approaching the sump following a LOCA would be insufficient to transport paint chips or other i
debris larger than the screen mesh size to the sump and that the sump's curb geometry would preclude paint chips from flipping up onto the screens. The analysis also identified, that the safety function of the emergency sump would be maintained with a blockage ratio significantly
. greater than 50 percent, thus illustrating the sump's available margin.
. San Onofre Units 2 and 3 design is consistent with the recommendation of Regulatory Guide l
(82, Revision 0 except for the differences indicated in UFSAR Table 3A-2 (
Reference:
UFS AR, l
Section.1A 1.82).
Under this commitment, San Onofre Units 2 and 3 has assumed that the i
sumps may experience blockage of up to 50% of the effective sump screen area from debris generated as a result of a LOCA. At the time San Onofre Units 2 and 3 was licensed, no...
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ENCLOSURE j
- dis'tinctiori was drawn between the various potential sources for post-LOCA debris.. The -
l emergency core cooling and containment spray systems were intended to function, even with debris from any originating source partially obstructing the screens.- The analysis submitted as I
part of the licensing basis for San Onofre Units 2 and 3 demonstrates that, even with this j'
blockage, the emergency core cooling and containment spray systems will continue to provide sufficient ' ooling flow to fulfill the long-term cooling functions required to conform with'.
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- The NRC accepted this analysis and these systems as meeting the requirements of 10CFR50.46b(5) in NUREG-0712, Safety Evaluation Report (SER) related to the Geration of San Onofre Nuclear Generating Station, Units 2 and 3.
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' SER, Section 612.2 states:
l We have reviewed the design of the containment emergency sump for conformance
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with the guidelines of Regulatory Guide 1,82, " Sumps for Emergency Core Cooling l
and Containment Spray Systems." Table 6.2 of this report presents a comparison of the San Onofre 2 and 3 sump design features with the design criteria of Regulatory j
Guide L821 As can be seen from Table 6.2 the major deviation from the sump design j
l criteria recommended in Regulatory Guide 1.82 is that only one emergency sump is p
provided in each reactor building (as opposed to two eurnps recommended in Regulatory Guide 1.82). _ For the San Onofre 2 anO pu. however, the single sump is divided into two redundant compartments by an 8-inch-tnick concrete structural
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barrier. This barrier precludes damage to both sump intakes from whipping pipes or high velocityjets of water or steam. Based on our review we conclude that the sump ~
design is adequate and will provide a sufficient supply of water, with a minimum amount of particulate matter reaching the containment spray system.
SER, Section 6.3.2 states:
Based on the considerations noted above with respect to housekeeping requirements, the avoidance of materials likely to form small-size debris, the lack of an apparent mechanism for blockage of more than the previously tested value of fifty percent of screen area oflarger debris, and the ability to monitor and control ECCS status, we conclude that the present design of San Onofre 2 and 3 provides reasonable assurance l
that the post-LOCA recirculatiowf reactor coolant will not be impaired by debris, and
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is therefore acceptable.
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~ The licensing basis for San Onofre Units 2 and 3, as accepted in the NRC's SER, provides both
. the regulatory and safety basis for safety systesa performance. Coatings are not treated as a separate debris source in the licensing basis for San Onofre Units 2 and 3. The sump screen blockage assumption does not distinguish among the sources for the LOCA-generated debris. The sump's design basis, as confirmed by the containment sump design testing which j
considered the containment design's screening action, and the procurement, application, and
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1 ENCLOSURE malatenan'oe control programs for qualified coatings inside containment provide reasonable assurance that San Onofre meets the safety function of the ECCS as required in 10CFR50.46b(5).
Accordingly, a separate demonstration of the regulatory and safety basis for safety system l
performance is not required.
Thefollowing information shall be provided:
(a) Ifcommercial-grade coatings are being usedatyourfacilityfor Service Level 1 applications, and such coatings are not dedicated or controlled underyour t
l Appendix B Quality Assurance Program. provide the regulatory and safety basisfor l
not controlling these coatings in accordance with such a program. Additionally, explain why thefacility's licensing basis does not require nch a program.
l Response to Item (2)(ii)(a):
l Southern California Edison does not currently employ commercial grade dedication for Service l
Level I coatings used inside containment at San Onofre Units 2 and 3. Service Level I coatings l
used at San Onofre 2 and 3 for new applications or repair / replacement activities are procured from t. coating supplier (s) with a quality assurance program meeting the applicable requirements of 10 CFR Part 50, Append' : B.
L Reference : 1. SO23-611-1-7, Final Report on Hydraulic Model Studies of Containment Emergency Sump Intakes, Western Canada Hydraulic Laboratories 1979.
- 2. SO23-611-1-2, Hydraulic Model Studies of Containment Emergency Sump
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Recirculation Intakes with Revised Operating Water Levels, Western Canada Hydraulic Laboratories 1990.
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- 3. A-98-NM-002, Rev. O, " Post-LOCA Emergency Sump Operability in Presence of Loose Coatings and Other Debris" I
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