ML20198G568
| ML20198G568 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 12/21/1998 |
| From: | Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 50-338-98-05, 50-338-98-5, 50-339-98-05, 50-339-98-5, 98-686, NUDOCS 9812290108 | |
| Download: ML20198G568 (13) | |
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Vincisir Ei2:cTHIc ANI) POWI:H CmtmNY NCli%10ND, VIRGINI A 23261 5
December 21, 1998 U. S. Nuclear Regulatory Commission Serial No.98-686 Attention: Document Control Desk NAPS /JHL R7 I
Washington, D. C. 20555 Docket Nos.
50-338 50-339 License Nos.
NPF-4 i
NPF-7 i
Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 INSPECTION REPORT NOS. 50-338/98-05 AND 50-339/98-05 REPLY TO A NOTICE OF VIOLATION We have reviewed your letter of November 5,1998, which referred to the inspection conducted at North Anna Power Station from July 13,1998 through July 31,1998, and the associated Notices of Violation that were reported in Inspection Report Nos. 50-338/98-05 and 50-339/98-05. On December 10,1998, a meeting was held between Virginia Electric and Power Company (Virginia Power) and NRC representatives to discuss the issues associated with Notice of Violation A. This meeting resulted in a better understanding of the issue.
It was agreed that the response to Notice of Violation A would be provided by Decernber 21,1998. Accordingly, our response to Notice of Violation A is provided in Attachment 1.
Responses to Violations B and C were not required in the referenced reports. The characterization of the issues and associated corrective actions for Violations B and C are accurately described in the Inspection Report.
i Your letter transmitting the Inspection Report expressed concem with inaccurate as-built drawings for safety related piping systems. Specifically, you were concemed that the violation appeared to contradict the August 1,1979 response to IE Bulletin 79-14, Seismic Analysis for As-Built Safety-Related Piping Systems. We are aware that minor discrepancies exist between design documentation and installed pipe support structural details. These discrepancies do not reduce our confidence that the as-built configuration of the safety-related piping conforms to the design criteria. Our response to the pipe support drawing discrepancies and the basis for our confidence in design and analyses of as-built safety related piping systems is included in the Response to Notice of Violation contained in Attachment 1. You also expressed concem with the length of time that was necessary to determine operability of the Unit 1 Auxiliary 9812290108 981221 I
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1 Feedwater (AFW) piping system after a multiple pipe support hanger was discovered to be missing, Attachment 2 to this letter discusses this concem.
i' If you have any further questions, please contact us.
t Ve truly yours,
/ ~ J b e-James P. O'Hanlon Senior Vice President - Nuclear Attachments Commitments made by this letter
- 1. The guidance provided in ASME Code Case N-430 and EPRI Report NP-5380 Volume 1, Visual Weld Acceptance Criteria for Structural Welding at Nuclear Power Plants, will be used for the pipe support weld size visual inspections. At least 58 accessible safety related pipe supports will be inspected in accordance with Volume 2 of EPRI Report NP-5380, Sampling Plan for Visual Reinspection of Welds. The i
report provides guidance for developing a statistically valid sample plan.
Discrepancies that are identified during these inspections will be documented and evaluations will be performed as described in the EPRI Report. These inspections will be completed by March 1,1999.
- 2. Support drawings will be revised in accordance with administrative procedure VPAP-0302, Station Drawing Annotation and Revision, as appropriate, to incorporate discrepancies identified in the violation and during the additional pipe support inspections described above.
cc:
U. S. Nuclear Regulatory Commission Region ll Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303 Mr. M. J. Morgan NRC Senior Resident inspector North Anna Power Station
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i ATTACHMENT 1
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REPLY TO NOTICE OF VIOLATION INSPECTION REPORT NOS. 50-338/98-05 AND 50-339/98-05 I
NRC COMMENT i
During an NRC inspection conducted at your North Anna facility, on July 13 through 31, i
1998, violations of NRC requirements were identified. In accordance with the " General l
Statement of Policy and Procedures for NRC Enfo. cement Actions," NUREG 1600, the violation, which requires response, is listed below:
i A.
10 CFR 50, Appendix B, Criterion V requires that activities affecting quality shall be prescribed by documented instructions, procedures, or drawings, of a type appropriate to the circumstances and shall be accomplished in accordance with these instructions, procedures, or drawings. The requirements for construction l
of safety related pipe supports were specified in the applicable Stone and l
Webster drawings, which showed required weld sizes and support configuration.
i Contrary to the above, as of July 12, 1998, AFW pipe supports were not constructed in accordance with details shown on the design drawings as specified below:
- 1. Drawing (Sketch) number MFSK-4289A-3 required 1/4" fillet welds on connections between steel members (angles or angles and wide flanges) for i
the upper box frames and Detail T box frame for pipe support SHP R-187.
The as-built weld sizes were measured as 1/8" or 3/16" at numerous j
locations on these members.
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- 2. Drawing (Sketch) number 7054 required 1/4" fillet welds on connections i
between steel angle members for the three box members for the 3 inch l
diameter pipes on pipe support numbers SHP-R-188 and 189. The as-built j
welds were determined to be 1/8" at several locations at the top of the box frames.
- 3. Drawing (sketch) number 2-4233 required 1/4" fillet welds on connections l
between bill of materials (BOM) items 4 and 5 on pipe support 2SHP-R-34.
l The vertical weld at top, left connection measured 3/16".
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- 4. Drawing number 12050 ZFSK-2536A-2 required 5/16" fillet welds at connections of 4x4 tube steel posts to surface mounted plates attached to the tunnel ceiling on support 2SHP-R-15. The welds on the right side of left post and front and left sides of the right post measured 1/4".
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- 5. Drawing number 11715-PSSK-102FA.3 required 1/4" fillet welds at the connection of BOM item 1 (6" wide, ange) to base plate on pipe support 1-WAPD-h-19B. The weld on the top web at right connection measured 3/16".
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- 6. Drawing number 11715-PSSK-102FD.1 required 1/4" fillet welds at the connection of BOM items 2 (6" wide flanges) to the baseplate on pipe support 1-WAPD-R-22. The welds on the bottom and sides of the top wide flange
. measured 3/16". The drawing also specified no gap (a zero inch gap) at the bottom of the 6" diameter pipe. A gap existed.
- 7. Drawing number 11715-PSSK-102FD.4 required 1/4" fillet welds between BOM item 5 (stiffener plates) and the baseplate on pipe support 1-WAPD-A-i
- 18. The welds measured 3/16".
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- 8. Drawing number 11715-PSSK-102FD.3 required 1/4" fillet welds for i
connection of BOM items 8 (steel angles) to BOM item 1 (wide flanges) per Section 1-1 and for connection of BOM item 9 (stiffener plate) to BOM item 6 j
(baseplate) on pipe support 1-WAPD-R-24. The welds measured 3/16" at riaht side of BOM item 9 and on right and left sides of BOM item 8.
l This is a Severity Level IV violation (Supplement 1).
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REPLY TO NOTICE OF VIOLATION 1.
REASON 50R THE VIOLATION The reason for the violation was failure to construct Auxiliary Feedwater (AFW) pipe supports in accordance with details shown on design drawings.
The process used to install, inspect, and document pipe supports is discussed below.
Pipe supports were to be installed in accordance with the latest approved specifications, weld procedure, pipe support drawings, hanger sketches, Engineering & Design Coordination Reports (E&DCRs), and Field Engineer instructions. Drawings used for support installation and inspection were Grinnell sketches and Stone & Webster Engineering Corporation AP / FP, MFSK, and ZFSK drawings. These support drawings and E&DCRs provided the as-built design configuration for pipe supports. There was no single governing drawing that provided the entire as-built design configuration of pipe supports.
Field Quality Control Procedure OC-11.4, inspection of Pipe Hangers, established the control program for installation, inspection, and documentation for pipe supports. Field Quality Control was required to visually inspect pipe support and support installation (including weld inspection) for 100% of Safety Related systems (designated 01,02,03), and systems designated with "S" (Seismic). Acceptability was documented on a OC " Pipe Hanger and Support Checklist."
The checklist documents whether the visual inspection was satisfactory. The OC inspectors had access to applicable E&DCRs that provided the basis for accepting some pipe support discrepancies. The size and type of welds to be constructed was in accordance with approved drawings and procedure W-200, " General Welding Procedure for Structural Steel Assemblies."
W-200 required that the welder and welding foreman verify the welds met applicable requirements. OC was responsible for verifying the size, length, and quality of welds.
The NRC inspection identified three potentially significant weld size discrepancies where weld sizes were noted to be 1/8" undersized. Materials Engineering performed visual examination of pipe supports SHP-R-188 and 189 by removing some weld material and etching the end of the weld.
This inspection confirmed the' for the examples identified where it was not possible to weld on both sides 01 a member, the attemate weld details provided in an E&DCR were used (refer to item 1 of the violation for pipe support SHP-R-187).
However, for the steel angle members for the three box members for the 3" diameter pipes, it appears that a different attemate weld detail may have been used (slot weld with 1/8" fillet reinforcement) for which no E&DCR has been located (refer to item 2 of the violation for pipe supports SHP-R-188 and 189).
These welds have been conservatively evaluated using the smaller fillet weld size and found to meet the design criteria.
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The QC procedure in use during plant construction stated that supports were to be installed in accordance with the " latest approved drawings and sketches, E&DCRs and/or Hanger Engineer's instructions".
It is worth noting that I
Construction, QC, and Engineering worked together during construction activities to ensure a quality product. Weld inspections were performed prior to coating the pipe supports. It is our experience that nuclear grade coatings are thick enough that uneven application and pooling during the drying process can influence visual weld size measurements taken after the coating is applied.
Another concem identified in the letter transmitting the inspection Report was related to the accuracy of the Virginia Power response to IE Bulletin 79-14.
Virginia Power responded to NRC IE Bulletin 79-14, Seismic Analyses for As-Built Safety-Related Piping Systems on August 1,1979. The Virginia Power response.to Bulletin 79-14 provided justification for not re-verifying the as-built configuration to the seismic analysis input information because North Anna Unit L
1 recently completed construction and North Anna Unit 2 was still being L
constructed. The response stated "These plants were constructed under rigid l
quality control and inspection requirements to assure conformance of as-built conditions to design conditions." The response provided a detailed description of the Field Quality Control Program that assured the as-built configuration of l
pipe run geometry and support installation conforms to applicable design criteria 1
and documents.
During the NRC inspection conducted in July 1998, several minor weld discrepancies were Mentified on AFW pipe supports. Attempts were made to retrieve E&DCRs ard donconformance and Disposition (N&D) reports that could provide the basis for acceptance'of the weld discrepancies. Some E&DCRs and N&Ds were found to substantiate the as-built condition. The discrepancies for which E&DCRs could not be located are minor, have been evaluated as being l
acceptable, and meet design criteria.
We are confident that the Virginia Power response to NRC IE Bulletin 79-14, provided in August 1979, is accurate and assures the as-built configuration of safety-related piping systems conforms to the design criteria and documents that were used as input to the seismic piping analysis. In addition, review of our available documentation indicates that no safety or operability concerns have ever been identified at North Anna associated with weld size discrepancies such as those identified in the violation.
2.
CORRECTIVE STEPS WHICH HAVE BEEN TAKEN AND THE RESULTS ACHIEVED Station deviation reports were initiated to document the potential weld discrepancies. An initial operability determination was made at the time of o
i deviation report submittal, it was determined that reduced pipe support weld lL.
l cross-section is not an immediate operability concem because the supports are intac,t and.are capable of performing their design function. Maintenance Rule i
l Functional' Failure Evaluations were performed for the discrepancies.
The l
evaluations determined that no functional failure had occurred because the l
function of the support structures was not lost. The supports identified in the Notice of Violation with weld discrepancies have been conservatively evaluated 1
using the smaller fillet weld size and found to meet the design criteria. The l
evaluation is documented in calculation CE-1441.
A review of specific issues identified during the Safety System Engineering Inspection of the AFW system was performed. The issues involved:
- 1) pipe hangers shown on design documents that were not installed in the
- field,
- 2) minor differences between weld sizes shown on design documents but not reflective of the as-built condition, and
- 3) adequacy of sample size to determine the safety impact of unknown weld size differences.
The first issue is an isolated case that has been linked with the original design and construction practices at North Anna.
Stone & Webster Engineering Corporation (SWEC) was the architect / engineer for North Anna. For certain piping systems, Grinnell was contracted to design pipe supports. The missing supports were located at piping drawing interfaces. That is, the support was shown on the continuation match line between two different pipin0 drawings.
Apparently, miscommunication within Grinnell and between Grinnell and SWEC resulted in no supports being designed for the identified locations. Specification NAS-28 was reviewed to identify the safety-related systems where original construction support design was the responsibility of Grinnell and approximately 125 FP piping drawings were identified. To evaluate the extent of this first issue, these piping drawings were screened to establish the appropriate drawings for review and a sample consisting of 26 applicable MSK drawings were selected for detailed review. The detailed review encompassed over 80 match lines and no further missing supports were identified. Based on the detailed review results, we are confident that this is an isolated event. Engineering analysis is complete for the identified missing pipe supports. The stresses remained within NRC Generic Letter 91-18 allowable values so that AFW remained operable. A modification was recently completed to provide additional margin and to return the welded attachment stresses to within our more restrictive plant design allowable values.
For the second and third issues, we are aware that minor differences between design documentation and installed pipe support structural details exist. We are confident these differences are minor and do not affect the overall operability of l
the supports.
The supports identified in the Notice of Violation with weld discrepancies have been conservatively evaluated using the smaller fillet weld i
size identified by the NRC and found to meet the design criteria. In order to
l-l further assess the extent and significance of this issue, (A) detailed inspections werg performed for two pipe support structures in the AFW pipe tunnel, (B) previously ' documented detailed support inspection results were reviewed, and (C) additional support weld inspections are planned. The details are provided below.
A. Detailed Inspection in AFW Pipe Tunnel Engineering performed detailed weld inspections of the entire pipe support structures for SHP-R-189 and SHP-R-177. These supports are located in the Unit 1 AFW pipe tunnel. (The NRC inspectors initially inspected the support structure for SHP-R-189).
Weld details on the support structures were representative of the other gang hanger pipe supports in the Unit 1 AFW pipe tunnel. A detailed analysis of the field verified as-built weld joints was performed to confirm structural adequacy. The results of this analysis are documented in l
Engineering Transmittal CEM-98-0041 and Calculation CE-1417. Decal loads, l
which represent a conservative upper bound estimate of the pipe load on the support structure, were used in the analysis. (The decal loads were found to bound calculated pipe support loads for the selected supports). The weld joints have strength significantly higher than that required for carrying the conservatively applied loading. The weld locations analyzed for the support structures show that the ratio of allowable weld loading to conservatively calculated weld loading for the different connections varied between 1.12 and 7.45. (Note that these ratios do not consider the additional margin resulting from the conservative " decal" loads used in the analysis).
B. Previously Documented Support inspection Results We have reviewed NRC Inspection Reports, from 1980 through 1998, dealing with NRC IE Bulletin 79-14. At least 100 supports / restraints were documented in l
NRC Inspection Reports (including the current Inspection Report) as being reviewed in detail by the NRC for various plant systems.
Several minor discrepancies were identified, including some associated with weld detai!s. In all of these inspections, the discrepancies identified have been minor and accepted as-is. Discrepancies were resolved by revising drawings, calculations, or through analysis, as required. No safety or operability concerns have been identified l
associated with discrepant weld details.
The statistical framework provided in ANSI /ASOC Z1.4-1993, Sampling Procedures and Tables for Inspection by Attributes, was used to establish a sample size to evaluate the level of significance of the previous detailed pipe support inspections. A multiple sampling plan was used based on a 95%
probability of acceptance that greater than 99% of the population is acceptable.
A pipe support population of about 10,000 was used (encompassing both units).
The supports inspected encompass various Units 1 and 2 piping systems located inside and outside of containment. Because the supports were selected at different times and for different reasons, it is reasonable to assume that the 4
intent of random sampling has been met.
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i Based on t,he above, an initial pipe support sample size of 100 is required. For the desired level of significance, the Acceptance Number is zero and the Rejection Number is three. In other words, no further inspections would be required as long as there are no supports in the initial sample requiring modification to bring them into acceptable status. (Conversely, if 3 or more supports in the initial sample require modification to bring them to an acceptable level, then additional samples would need to be evaluated to determine acceptance until all supports would need to be inspected). There were no unacceptable pipe support identified in the previously inspected sample population of more than 100. Based on the statistical sampling defined above, we are confident that the as-built condition of our safety-related pipe supports adequately meets or exceeds our design criteria. However, to enhance our confidence level, additional pipe support welds will be inspected using the guidance of ASME Code Case N-430 and EPRI Report NP-5380. Further details conceming these inspections are provided below.
In addition, overall confidence in the quality of safety-related piping support design, construction, and operability i,s supplemented by these current practices:
ASME Section XI visual examination requirements are outlined in Virginia Power Administrative Procedure (VPAP) 1103. VT-3 visual examinations are performed to determine the general mechanical and structural condition of components and their supports.
Inspection details such as missing, detached, and looseried support items and gaps between a pipe and pipe support are included in VT-3 visual examinations. Weld dimensions are not specifically checked during these VT-3 visual examinations; however, significant weld discrepancies such as missing welds would be identified. We have examples where pipe supports that were identified with discrepancies are documented and appropriate actions are taken to resolve. The corrective action may include physical corrective action and/or drawing changes. This periodic inspection process helps provide assurance of the quality of our safety related pipe supports.
Standard ongoing processes such as engineering walkdowns for Design Change Package preparation, maintenance walkdowns for work orders, and designer walkdowns for Drawing Change Request verification, have resulted in identification of some pipe support discrepancies. We have examples where pipe supports have been identified with differences between the as-built condition and the design drawing.
The differences have been documented, and appropriate actions have been taken to resolve the issue.
l The corrective action typically involves updating design drawings to reflect as-built conditions. This ongoing inspection process helps provide assurance of the quality of our safety related pipe supports.
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l The current OC process includes more inspection points than during original construction and these inspections are all documented. There are additional signoffs during current construction processes to ensure traceability to the welder. Any altemate weld details that are used during construction are not accepted by QC until the details have been incorporated into the design drawing via Installation Problem Reports (IPRs) and / or Field Changes
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l (FCs).
C. Additional Pipe Support Weld Inspections to Be Performed l
Industry guidance is available and endorsed by the NRC for performing visual i
reinspections of structural welds.
This industry guidance was developed j
because minor deviations in structural welding often have no detrimental effect on plant performance and therefore, a standardized criteria was desired that could eliminate corrective actions that did not actually improve plant quality. The guidance is provided in ASM3 Code Case N-430 and EPRI Report NP-5380 Volume 1, Visual Weld Acceptance Criteria for Structural Welding at Nuclear Power Plants. This guidance will be used for the pipe support weld size visual i
inspections.
Volume 2 of EPRI Report NP-5380, Sampling Plan for Visual Reinspection of Welds, provides guidance for developing a statistically valid sample plan.
This guidance will be applied to develop our pipe support inspection sample plan. Discrepancies that are identified will be documented and evaluations will be performed as described in the EPRI Report.
To the best of our knowledge, no pipe support weld discrepancy has been identified that resulted in the support Leing outside of the design criteria. In other words, no physical modifications were required to correct identified weld l
discrepancies. Additionally, the load resisted by a 1/4" weld is only 1.33 times the load resisted by the same length of 3/16" weld. However, a weld can resist at least two times its normal design load capacity without a gross failure.
Assuming a 1/4" weld was loaded to the maximum normal acceptable value, a 3/16" weld at that location would easily resist the maximum design load without a gross failure. Therefore, identification of a slightly undersized weld in a pipe support structural connection will not lead to an immediate operability concem for a piping system. Based on the above discussion, we are confident that quality of l
our safety-related pipe supports is maintained.
3.
CORRECTIVE STEPS WHICH WILL BE TAKEN TO AVOID FURTHER VIOLATIONS Based upon the statistical study of the quality attributes and the dete,
...t perspective discussed above, a high confidence level exists about the omktv af the entire population of safety-related pipe supports. However, additional pipe t
support weld inspections will be performed as described below to provide additional assurance that safety-related pipe supports meet design criteria.
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l The guidance provided in ASME Code Case N-430 and EPRI Report NP-5380 Volume 1,., Visual Weld Acceptance Criteria for Structural Welding at Nuclear l
Power Plants, will be used for the pipe support weld size visual inspections. At least 58 accessible safety related pipe supports will be inspected in accordance with Volume 2 of EPRI Report NP-5380, Sampling Plan for Visual Reinspection of Welds. The report provides guidance for developing a statistically valid sample plan. Discrepancies that are identified during these inspections will be documented and evaluations will be performed as described in the EPRI Report.
Support drawings will be revised in accordance with administrative procedure VPAP-0302, Station Drawing Annotation and Revision, as appropriate, to incorporate discrepancies identified in the violation and during the additional pipe support inspections described above.
4.
THE DATE WHEN FULL COMPLlANCE WILL BE ACHIEVED l
As described above, these welds have been shown to be constructed in l
accordance with the design requirements for safety-related pipe supports during i
the construction of the plant. The additonal pipe support inspections identified above, performed to provide additional assurance that safety-related pipe supports meet design criteria, will be completed by March 1,1999. Based on the inspection results, additional actions may be determined at that time.
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i ATTACHMENT 2 s
The Inspection Report expressed,concem with the length of time to determine operability of the Unit 1 Auxiliary Feedwater (AFW) piping system after a multiple pipe 1
support hanger was identified to be missing on June 16,1998. The Inspection Report stated that the final design analysis was not completed until July 29,1998 at which time it was determined that the operability of the AFW system was not affected. We believe that the NRC concem identified in the inspection Report does not accurately reflect all the facts involved. A detailed discussion on the AFW piping / _ support analysis is provided below which establishes that our responses to the deviating conditions were complete and the timeliness was commensurate with the safety significance of this issue.
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On June 16,1998, a gang hanger that was intended to provide vertical / lateral restraint for various pipes (AFW, Q3, WCMU, MS) was identified to be missing in the Unit 1 pipe tunnel. It was determined that the original North Anna Unit 1 pipe stress analysts (Stone & Webster Engineering Corporation) intended an additional support be located in the middle of the 15 foot piping span. A deviation report (DR) was submitted on June 16,1998 (DR N-98-1881).' Engineering provided an operability assessment of the i
piping system with the deviation report. This initial assessment was based on:
l pipe routing and location of the pipe supports, low seismic accelerations for the AFW pipe tunnel, e
absence of any concentrated mass in the area, and e
results of recently performed computer analysis of the AFW lines in this area (for l
corrosion concem identified in DR N-98-1677).
Based on these attributes, and with knowledge that the initial design of the AFW tunnel piping was performed by a conservative chart method, the Virginia Power pipe stress analysts were quito confident that the AFW system operability was not adversely impacted by the missing support.
The initial operability assessment was completed v> ell within the 48-hour guidance provided in Supplement 1 to IE Bulletin 79-14, Seiunic Analysis for As Built Safety-Related Piping Systems.
The initial assessment was also performed within the l-guidelines provided by NRC Generic Letter 91-18, Information to Licensees Regarding Two NRC Inspection Manual Sections on Resolution of Degraded and Nonconforming Conditions and Operability.
Generic Letter 91-18 documents that an operability determination should be rnade as soon as possible consistent with the safety l
importance. In most cases, it is expected that a decision can be made immediately. In other cases, it is expected that a decision can be made within approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of discovery of the degraded or nonconforming condition even though complete information may not be available.
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Computer pipe analysis models were prepared and run with acceptable results.
l Additionally, the pupports' loads were reviewed to compare with the decal loads that had been previously used to design the ganged pipe supports in the pipe tunnel. The expectations for having an " analytical engineering evaluation" completed within 30 days as described in Supplement 1 to IE Bulletin 79-14 was met.
Although a formal l
calculation was not filed at that time, Virginia Power met the intent of the NRC guidance documents for operability determination.
A formal calculation of the above evaluation was not filed because it was determined l
that an " anchor-to-anchor" pipe stress analysis should be completed and documented l
for future reference. This decision was made for efficiency and to prevent engineering i
rework in the future. As per Virginia Power policy for pipe stress analysis, the pipe i
stress analyst requested a walkdown of the AFW piping extending to the pipe tunnel /
AFW pump house (AFWPH) interface to verify piping and support configuration.
L During the verification walkdown it was determined that an additional ganged piping l
support (anchor) was missing for several AFW lines at the pipe tunnel / AFWPH interface. This missing anchor is removed from the first identified missing gang hanger by quite a distance and several supports. However, the piping in the vicinity of both l
missing supports was part of the computer models previously analyzed.
The l
identification of the deviating condition and an initial operability assessment was provided via DR N-98-2106 on July 7,1998.
Therefore, the initial operability determination was performed well within the guidance of Supplement 1 to IE Bulletin t
79-14 and Generic Letter 91-18.
Detailed analysis was completed for the missing anchor near the pipe tunnel / AFW pump house interface and the results were documented in Engineering Transmittal CEM-98-0042, Rev. O dated July 30,1998. This Engineering Transmittal documents that the AFW piping and support loads are acceptable; however, two pipe anchors located in the AFW pump house were identified as exceeding normal acceptable stress values (at welded connections to the piping), but remained within the Generic Letter 91-18 acceptable levels. The detaled analysis was completed within 23 days of the l
deviation report identifying the missing anchors at the pipe tunnel / AFW pump house interface. This is within the 30-day guidance provided in Supplement 1 to IE Bulletin 79-14 and within the guidelines provided by Generic Letter 91-18. Modifications were subsequently made during the 1998 North Anna Unit 1 refueling outage to bring the l
support stresses back into normal acceptable requirements.
in summary, there were two separate instances that required operability assessment L
and resolution. An " analytical engineering evaluation" was performed for each of these in a timely manner commensurate with the safety significance of the issue. For the i
sake of efficiency, it was determined that documentation would be easier for future reference with one complete pipe stress calculation package. Accordingly, the detailed operability determinations were completed well within the guidance of Generic Letter 91-18, although formal documentation was not completed until later.
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