ML20247N929
| ML20247N929 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 07/31/1989 |
| From: | Michael Ray TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8908030236 | |
| Download: ML20247N929 (3) | |
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TENNESSEE VALLEY AUTHORITY.
CHATTANOOGA, TENNESSEE 37401 SN 157B Lookout Place JUL 811989
'O.S. Nuclear Regulatory Commission
-ATTN: Document Control Desk Washington, D.C.
20555 Gentlemen:
-in the Matter of.
)
Docket Nos. 50-327
. Tennessee Valley Authority
)-
50-328
'SEQUOYAH NUCLEAR PLANT (SQN) - NRC INSPECTION REPORT NOS. 50-327, 328/88 UNRESOLVED ITEM (URI) 88-12-06 Er. closed is TVA's response to the subject URI that addressed analysis of water hammer caused by rapid feedwater check valve closure..This item was also identified as Observation MEB-3 of Inspection Report 50-327, 328/88-27 for SQN
' Units 1 and.2.
The enclosed response will resolve both of these items.
Please direct questions concerning this issue to B. S. Schofield at (615) 843-6172.
Very truly yours, TENNESSEE VALLEY AUTHORITY Ma g
1 ensing and Regulatory Affairs j
1 Enclosure I
cc (Enclosure).
Ms. S. C. Black, Assistant Director j
for Projects j
.TVA Projects Division i
U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike j
Rockville, Maryland 20852 Mr. B. A. Wilson, Assistant Director 1
for Inspection Programs j
l TVA Projects Division U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road 1
Soddy Daisy, Tennessee 37379 8908030236 890731
{DR ADOCK0500g7 An Equal Opportunity Employer 1
ENCLOSURE URI 88-12-06:
Feedwater (FW) Line Water Hammer Evaluation During the design calculation review, it was identified that TVA had performed an analysis of water hammer that was due to the FW check valve closure event but had not formally issued the report.
TVA subsequently performed an additional analysis that was considered acceptable to the staff for restart.
The staff has not resolved the issue as to the appropriate long-term criteria for this analysis.
Response
TVA and NRC discussed the FW line water hammer issue for SQN in a meeting in Bethesda, Maryland, on January 19, 1988 (reference NRC summary of meeting dated February 4, 1988). The discussion covered TVA's activities to evaluate the FW lines in accordance with Appendix F of the 1986 American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code.Section III.
NRC requested that TVA document the results of thel. review in a submittal.
TVA documented the results of the finite element analysis in a letter to NRC dated February 18, 1988.
The results of the activities performed and completion status of the activities are summarized below.
Tnese activities demonstrate structural integrity of the FW system during and following the check valve closure event 1.
Development of strain-based acceptance criteria usi,ng Appendix F of the 1986 ASME Boiler and Pressure Vessel Code, Section~III.
Status: Complete 2.
Thermohydraulic RELAPS analyses to establish forcing functions for the check valve closure event for all four Unit 2 FW lines.
Status: Complete 3.
Nonlinear piping analysis of the worst-case Unit 2 FW line.
Static equivalent analyses for the remaining three Unit 2 FW lines.
Note: The ANSYS finite element code was used for the nonlinear piping analysis in lieu of the DINASAW code. ANSYS was used in lieu of DINASAW because ANSYS has three-dimensional capabilities, whereas DINASAW can only provide analysis capabilities for planar structures.
Status: Complete 4.
Independent review of nonlinear piping analysis and strain-based acceptance criteria by Teledyne Engineering Services.
Status: Complete 5.
Qualification of steam generator nozzle loads by Westinghouse Electric Corporation.
Status: Complete 6.
Qualification of steel containment vessel penetrations, FW bellows, and FW check valve integrity.
Status: Complete
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Structural analyses to evaluate loading on concrete walls, structural l
steel, and embedded plates.
Status: Complete 8.
Evaluation of pipe attachments and safe failure of pipe supports.
Status: Complete 9.
The Unit 1 FW lines have been qualified on the basis of similarity to corresponding Unit 2 piping. Unit 1. FW loop 3 required the performance of an additional static equivalent analysis to obtain a realistic load distribution for the pipe supports because of a lack of similarity with Unit 2.
Unit I activities also include documentation of the acceptability of Items 5, 6, 7, and 8 of this enclosure.
Status: Complete These activities confirmed the ability of the Unit 1 and Unit 2 FW lines to sustain the effects of the check valve closure event within appropriate liaits.
NRC documented the acceptability of these activities for restart in Inspection Report 88-12 dated June 24, 1988.
During the January meeting, the fRC requested that TVA ensure that the analyses performed for the FW line water hammer analysis are consistent with the load combinations specified in the SQN Final Safety Analysis Report (FSAR). TVA provided a response to this question in the February 18, 1988, letter. TVA stated that the water hammer loads (pipe rupture loads) are not combined with the seismic loads and identified the appropriate FSAR sections.
NRC identified resolution of this question as a postrestart item in Inspection Report 88-12 (unresolved item 88-12-06).
TVA considers the FW line water hammer analyses already performed as an appropriate basis for long-term evaluation of the FW line water hammer event.
These analyses are consistent with the design loading combinations identified in Section 3.9.2.2 and Tables 3.9.2-2, 3.9.2-5, and 3.9.2-6 of the FSAR.
The FW line water hammer event and a safe shutdown earthquake are considered faulted conditions.
The appropriateness of the design loading combinations is supported by the fact that the plant would proceed to cold shutdown following either the FW line rupture (water hammer event) or an earthquake in excess of the operating basis earthquake.
TVA believes that NRC now has sufficient information to consider the long-term criteria for the FW line water hammer analysis resolved and to close unresolved item 88-12-06.
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