ML20236J935

Updates Status of Issues Re Plant Design Calculations Review Discussed in SA White to Jg Keppler,Reflecting Info Discussed in 870521 Meeting.Reasons That Certain Issues Remain Open Discussed

ML20236J935
Person / Time
Site:	Sequoyah
Issue date:	07/31/1987
From:	Gridley R TENNESSEE VALLEY AUTHORITY
To:	James Keppler NRC OFFICE OF SPECIAL PROJECTS
References
NUDOCS 8708060339
Download: ML20236J935 (10)

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TENNESSEE VALLEY AUTHORITY CHATTANOOGA, TENNESSEE 374ot 5N 157B Lookout place JUL 311987 Mr. James G. Kcppler, Director Office of Special projects U.S. Nuclear Regulatory Commission 4350 East West Highway EWW 322 Bethesda, Maryland 20814

Dear Mr. Keppler:

In the Matter of ) Docket Nos. 50-327 Tennessee Valley Authority ) 50-328 SEQUOYAH NUCLEAR PLANT (SQN) DESIGN CALCULATIONS REVIEW This letter is to provide an update on the status of those issues regarding the SQN design calculations review discussed in S. A. White's letter to you dated March 13, 1987. This reflects the infonnation discussed in our May 21, 1987 meeting.

The majority of these issues has been resolved and completed; however, some issues remain open. These issues remain open because (1) the initial effort is incomplete and/or (2) the results of the initial erfort identified deficiencies and the review must be expanded. In either case, a description and schedule for completion of the remaining work are provided in the enclosure.

The actions required to resolve these issues are essentially complete. The l remaining open issues are presently being reviewed for potential impact on the SQN schedule for unit 2 restart. I will advise you of any schedule impact as soon as possible.

Very truly yours, TENNESSEE VAL Y AUTHORITY

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R. L. Gridley, Director Nuclear Safet and Licensing Enclosures cc: See page 2 870B060339 DD 870731 Oh ADOCK 05000327 g PDR An Equal Opportunity Employer

'.. . l U.S. Nuclear Regulatory Commission d l

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cc (Enclosures): ]

Mr. G. G. Zech, Assistant Director j for Inspection Programs i Office of Special Projects j U.S. Nuclear Regulatory Commission l Region II 101 Harietta Street, NW, Suite 2900 i Atlanta,. Georgia 30323 Mr. J. A. Zwolinski, Assistant Director for Projects Division of TVA Projects Office of Special Projects j U.S.. Nuclear Regulatory Commission 4350 East West Highway -

EWW 322 Bethesda, Maryland 20814 Sequoyah Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379 l

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ENCLOSURE 1 UPDATE ON TVA STATUS OF ISSUES IDENTIFIED IN MARCH 5, 1987 J. M. TAYLOR LETTER SEQUOYAH CALCULATIONS REVIEW I. GSNERIC ISSUES

l. Notification to Site Management of Analysis Results With Plant Operating Procedures and Surveillance Requirements Impact Electrical Engineering Branch (EEB)

EEB has completed a review of all calculations required for Sequoyah Nuclear Plant (SQN) unit 2 restart to determine if additional unidentified technical specification impact exists. This review has I concluded that no unidentified impact exists in the electrical calculations. This includes the previously cited impact involving the 125-V de vital battery capacity. Regarding this previously cited impact, a further, more detailed loading analysis of the 125-V de battery has been performed; and the results indicate no limitations on the existing technical specifications. However, in the ]

Instrumentation and Controls (I&C) calculations, an additional impact I does exist. This impact involves the instrument accuracies for the auxiliary feedwater system suction pressure and the containment 1 building radiation monitors. In addition, the potential exists for - I impact to the instrument accuracy for the automatic switchover to containment sump circuit. This impact is dependent upon the result of an ongoing small break loss of coolant accident (LOCA) analysis by the Nuclear Engineering Branch (NEB), which may require revision to the setpoint and the instrument accuracy. Except for the containment sump circuit, where the results are not final, this impact does not af fect the actual instrument's setpoint; therefore, no safety impact exists.

I Hechanical Engineering Branch (HEB), Civil Engineering Branch (CEB), I and NEB have reviewed the process of design and modification, which includes the preparation of Engineering Change Notices (ECNs) and the assessment of impact on plant technical specifications. Each branch has verified compliance with existing change control procedures, thus ensuring adequate review of the changes for impact on the technical specifications and notification of site management as required.

2. What Deficiencies Exist in the Preoperating License (Pre-OL)

Calculations?

NEB: A sample review of pre-OL calculations is complete. One deficiency (failure to revise initial design calculations to reflect actual installed system configuration) was identified but was limited to one NEB section. A subsequent review of all pre-OL essential calculations performed in that section is

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complete and has identified only one further deficiency. One analysis (calculation T1-064-3) was deficient because of lack of consistency with more recently issued standards. ~The calculation will be revised postrestart with no hardware modifications required. The NEB calculation review scope has  ;

been expanded to 100-percent review of essential calculations.  !

Any-further deficiencies will be assessed in accordance with the j SQN restart criteria.

1 EEB: All' essential minimum sets of electrical calculations required to support SQN unit 2 restart have been regenerated. ]

MEB: The original technical adequacy sample review of' calculations is f complete with the following results. J

.MEB's technical adequacy review sample consisted of 77 essential calculations, 59 of which support the design that existed at the time of operating license'(OL) issuance. These calculations involved eight systems:

Number of SYSTEM Calculations Reviewed -

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3 (Feedwater)- 3 30 (Ventilation) 19 31 (Heating and Cooling) 13 67 (Essential Raw Cooling Water) 11 70 (Component. Cooling) 6 72 (Containment Spray) 5 74 (Residual Heat Removal) 1 82 (Diesel Generator) _1 TOTAL 59 Thirteen of the calculations reviewed were unacceptable, all of which involved two types of errors: (1) inaccurate heat loads ,

input data used in determining heating, ventilating, and {

air-conditioning (HVAC) cooling capacity and (2) original )

vendor-supplied data, which was later determined to be

.f inadequate and/or inaccurate by the vendor. All calculations in these two generic problem areas have now been reviewed, and .]

.I those found unacceptable have been revised and corrected.  !

It was recently' decided to expand the technical adequacy review to include 100 percent of the essential mechanical calculations. ,

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I CEB: In addition to the reviews addressed in item 3 below, CEB has reviewed both pre- and post-OL calculations for the following designs:

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1. Civil Structural Features I

2. Conduit Supports  !

3. HVAC Supports

4. Rigorously Analyzed Piping

5. Rigorously Analyzed Pipe Supports

6. Embedded Plates j

7. Miscellaneous Steel Structures 1 Table 1 shows the results of thesi technical adequacy reviews.

In addition, several hundred calculations, which are also shown ]

j in table 1, have been generated post-OL. This regeneration I also provides a review of the pre- and post-CL designs. Since the regeneration was performed by different engineers from the j original designers, the regeneration is considered to be an j independent technical review. Conclusions from this effort are: ]

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1. Only one physical modification has been required to date. 1

2. Further evaluations are necessary and are ongoing. I

3. Some modifications to calculation packages were required.

4. Rigorously analyzed piping and supports are being evaluated under a special program scheduled for completion to the extent practicable by October 31, 1987.

3. Civil Engineering Calculations Review Records The " Civil Engineering Analysis Verification Retort" was issued on April 1, 1987. The report was subsequently revised and reissued on June 1, 1987, under the title of " Civil Engineering Technical Adequacy Report." The report lists past external and internal reviews of calculations and extracts and assembles key results and findings from these past reviews. TVA's assessment of these past reviews indicatee a need for supplemental reviews. The supplemental reviews (discursed in item 2 above) and the past reviews are the' {

basis for ver.i.fying the adequacy of the scope of calculations for the l civil discipline. I

4. Calculations program Integration l The Engineering and Computer Methods Branch (ECB) is developing j computer software and data bases to provide indexing capabilities for tracking essential calculations for TVA's nuclear plants. Initially, the calculations Cross-Reference Information System (CCRIS) will contain a multidiscipline integrated essential calculations log for CEB, EEB, MEB, and NEB. Further, CCRIS will contain cross-references l from these calculations to associated calculations, thus aiding in the identification of calculation predecessors and successors.

Ultimately, CCRIS may be expanded to cross-reference noncalculation ,

documents, e.g. , vendor manuals, Quality Information Releases (QIRs),

and ECNs.

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The initial loading into CCRIS of essential calculations for EEB, MEB, and NEB was completed on June 1, 1987. The verification of the l calculations was completed on June 30, 1987.

The CEB portion of the CCRIS data base contained an entry for each calculation package from the merged data bases for the civil calculations on June 1, 1987. By September 2, 1987, the category / ,

building / system data associated with all existing calculations in CCRIS will be verified using the calculation cover sheets from Records Information Management System (RIMS).

5. Design Baseline and Verification Program (DBVP) and Calculations Integration The design calculations program is an independent program for ensuring the technical adequacy of design analyses within the Division of Nuclear Engineering (DNE). This program's interface with the DBVP is defined by Sequoyah Engineering Project Procedure (SQEP)-12, which requires the evaluation of post-OL modification packages and the identification / review of any associated calculations. Based upon this procedure, each discipline has performed a sample review or has otherwise addressed the technical adequacy of the specific analyses identified by the DBVP.

MEB has completed a technical review of seven (approximately half) of the essential mechanical calculations associated with the DBVP. One calculation was fully adequate. The remaining six calculations were acceptable with minor deficiencies (e.g., minor input data errors, incomplete references, and minor conclusions discrepancies). None of the deficiencies identified in the DBVP-related calculations were significant enough to adversely affect plant safety or operability.

Further, none required hardware changes. These calculations have been revised to correct the minor deficiencies. The remaining DBVP essential calculations will be reviewed as a result of a recent decision to expand the technical adequacy review to all essential calculations.

NEB performed a review of ten calculations supporting ECNs both within and outside the scope of DBVP: five calculations supporting post-OL design changes within the DBVP scope and five calculations outside the DBVP scope were involved. This review identified one deficiency consisting of failure to maintain the calculation current j with existing plant configuration. This analysis was revised and reissued with no required hardware modifications identified. This action closes this item for NEB.

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-S-II. SPECIFIC ISSUES

1. Main Steam valve Room Floor A reanalysis for the floor slab has been completed and verifies ,

acceptable design stresses. Preparation of calculations for the supplemental review of the remainder of the west steam valve room calculations has been completed. In addition, the review of the environmental drawings has also been completed.

2. Auxiliary Building Shield Walls As a result of the generic review of environmental drawings for other areas of the plant subjected to pressure loadings, internal shield walls in the Auxiliary Building have been identified as requiring j additional calculations. These walls are subjected to pressures in 1 the range of 1.5 psi. TVA expects their structural adequacy to be j verified through these additional calculations.

Results of these evaluations, scheduled for completion by August 31, l 1987, will be reported as follow-up to NRC Observation CEB-ll, documented in Inspection Report Nos. 50-327/87-06 and 50-328/87-06.

TVA responded to this observation in a letter to NRC from R. L. Gridley dated July 2, 1987. Additional communication with URC will occur either in formal correspondence as a response to Inspection Report Nos. 50-327/87-27 and 50-328/87-27 or during an NRC follow-up inspection.

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3. Auxiliary Building Steel Platform Calculations )

I The calculations for the representative sample have been completed.

The calculations indicate that in some cases the design criteria and FSAR commitments were not met; however, an engineering evaluation has been performed that indicates that operability is not affected. The original issue was also identified by NRC as a concern and is documented as Observations CEB-2 through 6 in Inspection Report Nos. 50-327/87-06 and 50-328/87-06. TVA responded to these ,

observations in a letter to NRC from R. L. Gridley dated July 2, l 1987. Additional communication with NRC will occur either in formal correspondence as a response to Inspection Report Nos. 50-327/87-27 and 50-328/87-27 or during an NRC follow-up inspection.

4. Containment Pressure Transmitter Accuracy This item was previously identified as a postrestart issue. TVA is searching for a more accurate transducer. Discussions were held with Angelo Marinos and Jim Watt, of NRC's Office of Special projects, on Jutte 5, 1987, in which agreement was reached on the approach to resolution of the issue of containment isolation.

5. Component Cooling Water System Design Pressure MEB has completed recalculation of the revised system operating I pressure, including consideration of the surge tank relief valve setpoint. The operating pressure remains below the 150-psig design pressure.

6. Emergency Core Cooling System (ECCS) Pump Net Positive Suction Head (NPSH) Calculation TVA is reevaluating this issue as a result of NRC recommendations made during their most recent calculation audit. Appropriate revisions to the calculations are under way in conjunction with the resolution of certain unverified assumptions. This item will be resolved before restart.

7. Analysis Documentation for Buried ERCW Piping Calculations to demonstrate the seismic qualifiestion of buried ERCW piping have been regenerated and documented. The results indicate full compliance with the design criteria.

TABLE 1 CALCULATIONS (a)

Post-OL Independent Feature Regeneration Conclusion Review Comment Civil Structural 66 62 Acceptable 11 3 of 11 cales 4 Being Evaluated req'd revisions.

Conduit Supports 72 56 Acceptable 5 Independent 16 Being Evaluated review expanded.

l HVAC Supports 12 9 Acceptable 4 Independent 3 Being Evaluated review expanded.

Rigorous Piping 0 --

5 100%

Retrievable.

Rigorous Pipe 875 694 Acceptable 201 68 Cales reg'd Support 181-Being Evaluated reexamination.

40 of the cales reviewed with no change in the original conclusion of the cale.

Embedded Plates 75 74 Acceptable 75 All pre-OL 1 Modif. Reg'd design. Add'l embedded plates being reviewed.

Misc. Steel None See comments 54 Adequate per original cales.

100% retrievable.

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Through June 10, 1987 I

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ENCLOSURE 2 LIST OF COMMITMENTS IN TVA LETTER UPDATING TVA MARCH 13, 1987 LETTER ON DESIGN CALCULATIONS REVIEW

1. Revise NEB calculation T1-064-3 to make consistent with more recently l issued standards; this will be accomplished postrestart.

2. Under a special program, evaluate rigorously analyzed piping and supports by October 31, 1987.

3. By September 2, 1987, TVA will verify the category / building / system data associated with all existing calculations in CCRIS by using the calculation cover sheets in RIMS.

4. Complete the evaluations of the internal shield walls in the auxiliary building by August 31, 1987.

5. Before restart, revise NPSH calculations in conjunction with the resolution of certain unverified assumptions.

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