ML20079R741
| ML20079R741 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 01/31/1994 |
| From: | Fenech R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-91-18, NUDOCS 9402100023 | |
| Download: ML20079R741 (8) | |
Text
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Robert A Fenech vee Furmom. sequoyah Nuctew nant January 31, 1994 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:
In the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 SEQUOYA11 NUCLEAR PLANT (SQN) - GENERIC LETTER (GL) 91 RESOLUTION-OF' PIPING AND PIPE SUPPORT NONCONFORMANCES In accordance with recent Unit 2 restart discussions with the NRC staff, this letter provides SQN's position regarding implementation of the NRC guidance contained in GL 91-18 concerning the schedule for the resolution of piping and pipe support noncomformances (Enclosure 1).
The SQN position addresses the issue of the-timely resolution of nonconformances that do not meet the design basis criteria but do meet the operability criteria for interim use. provides a discussion of the. piping and pipe support noncomformances that. will not be fully corrected on a schedule consistent l
with the'SQN position.
Items 1, 2, 4, and 5 of Enclosure 2 were reviewed ~
by NRC during an inspection on civil issues for Unit 2 restart.
Inspection results were documented in Inspection Report Nos. 50-327, 328/93-49.
The estimated completion schedules identified in Enclosure 2 are tracked.
and controlled by the site corrective action program. No commitments are i
' contained in this submittal.
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t U. S. Nuclear Regulatory Commission Page 2 January 31, 1994 Please direct questions concerning this issue to J. Bajraszewski at (615) 843-7749.
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7 Robert A. Fenech Enclosures cc (Enclosures):
Mr. L. E. LaBarge, Prcject Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, MaryInnd 20852-2739 NRC Resident Inspector Sequoyah Nuclear Plant i
2600 Igou Ferry Road Soddy-Dairy, Tennessee 37379-3624 Regiona1' Administrator U.S. Nuclear Regulatory Conmission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323-0199,
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I ENCLOSURE 1 Issue:
This enclosure addresses the issue of the timely resolution of piping and pipe support nonconformances that do not meet the design basis. criteria but do meet the operability criteria for interim use.
Ecquoy.ah_Huclear E nat_IEQHl_fasitisn:
SQN understands that the timeliness of corrective action is important and '
should be commensurate with the safety significance of the identified issue.
For piping and pipe support nonconformances that have been; evaluated and found to meet the operability criteria for interim use but do not meet:
the desigt. basis critr-ta, the SQN practice is to resolve the condition in the next scheduled refueling outage. Relative to GL 91-18, nonconformances are said to be identified when the condition -has been-evaluated under the operability criteria, i.e.,
the operability criteria for interim use has been applied. However, when such nonconformances are-identified within six months of the start of the next scheduled refueling outage, the modification may be deferred until the following refueling outage. This six-month interval is necessary to efficiently plan resources,. coordinate design changes, implement ALARA (as low as-reasonably achievable) principles, and procure the required materials that have long lead times. SQN considers this-process.to be consistent with the intent of Generic Letter (GL) 91-18 expectntions for the timely correction of piping and pipe support nonconformances. The Unit 2 scope contained in Enclosure 2 is based on a scheduled Unit 2 Cycle 6 refueling stage to start in April 1994.
thia submittal informs NRC of tho'se piping and pipe suppert nonconformances, identified before the six-month interval, that are not fully resolved in the subsequent refueling outage. TVA recognizes that NRC and the nuclear power industry continue to' review and evaluate the expectations described in GL 91-18 through workshops and other-activities. As performance expectations change (e.g., revisione to
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GL 91-18), TV/. will f actor the new information into SQN's scheduling practices.
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ENCLOSURE 2 In accordance with the Sequoyah Nuclear Plant (SQN) position concerning the resolution of piping and pipe support noncomformances, thisLenclosure provides a list of such nonconformances that will not be fully corrected.
on a schedule consistent with that position. However, each.
i nonconformance' listed has been evaluated in accordance~with the uperability criteria for interim use and does not reflect a condition that would render the associated equipment or supports inoperable. These issues will continue to utilize the operability criteria for interim use (Interim operability criteria) upon the return to service of the affected unit. Corrective actions for these nonconformances are being deferred-because of the volume of existing scheduled work (limited resources) and the limited safety significance of the deferred items. The operability criteria vere reviewed by the NRC staff, and the review results are documented in Inspection Report Nos. 50-327, 328/93-49.
1.
FJtCW Tunnel Spectra i
Issue:
The seismic response spectra developed for the Units 1 and 2 essential raw cooling water (ERCW) pipe tunnel are, in some cases, higher than that used to analyze the safety-related piping in the tunnel. This nonconformance is being tracked in the SQN corrective action program as GQP890484PER. This issue was reviewed by the NRC staff, and the review results are documented in Inspection Report ~
Nos. 50-327, 328/93-49.
Evaluation _Hasia:
At the time of the October 19b3 NRC inspection, pipe supports within.
l the scope of the ERCW tunnel spectra issue were evaluated for interim operability. Of the total supports reviewed, one support modification was determined prudent to implement to simplify the review of a significant number of supports within the problem boundary.
This restored the system in the area of interest'to its designed condition and simplified interim ~ operability assessments for the other related supports.
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The remaining pipe support modifications are outside of the containment building and are' expected to be designed such that the modifications can be made during normal plant operation. Of.the nearly 700 pipe supports within the scope'of this-issue, approximately 10 percent of these supports require modification to upgrade the.pi-ing and pipe supports to' full compliance with the l
design basis criteria.
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Continsion:
Units 1 and 2 piping and pipe supports within the scope of this issue have been shown to meet the interim operability criteria. The modifications are scheduled to be implemented before restart from the Cycle 7 refueling outage of each unit.
2.
ERCH Thermal Operating Mode
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The operating mode calculations for the Units 1 and 2 component cooling system plate heat exchangers failed to consider the revised ERCW flow conditions and the Train B shared heat loads from the spent fuel pit heat exchanger. These issues can result in increased maxinnmi or decreased minimum operating temperatures. This results in a change of thermal range from 45-123 degrees Fahrenheit (F) to 37-130 degrees F and impacts nine piping analysis calculations. This nonconformance is being tracked in the SQN corrective action program as SQPER920230.
This issue was reviewed by the NRC staff and the review results are documented in Inspection Report Nos. 50-327, 328/93-49.
EYA1Dat10n_Baaia:
At the time of the NRC inspection, several calculations.had already been analyzed for other design changes and had incorporated the new operating temperature range. No pipe support modifications were identified at the time of the inspection as a result of the change in the ERCW operating temperatures.
The remaining calculations are currently being reanalyzed to include the new operating temperature,s.
The piping and pipe supports in i
L these calculations were discussed during the inspection and were L
shown tn meet the interim operability criteria, l
The piping contained in these calculations is located ~1n the auxiliary building. Pipe support modifications that are identified in the reanalysis are expected to be designed such that they can be implemented during normal power operation.
L Concluaion:
Units 1 and 2 piping and pipe supports within the scope of this issue l:
have been shown to meet the interim operability criteria. A reanalysis of the remaining calculations and identification of any modifications are scheduled to be completed by the end of February.
i 1994. Modifications resulting from these reanalyses are scheduled to l
be implemented before restart from the Cycle 7 refueling outages of
.each unit.
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CCS Therms 1 Operating Mode las.ue :
The thermal operating mode calculations for the Units 1 and 2 component cooling system (CCS) plate heat exchangers failed to consider the increased efficiency of the heat exchangers and their influence on CCS piping temperatures during the winter season. This-resulted in a decrease in the minimum operating temperature from 60 degrees F to 40 degrees F.
This nonconformance is being tracked 4.n the SQN corrective action program as SQPER920343. This issue was not discussed with NRC during their'onsite' inspection.
Evaluation _Easis:
A subsequent review of the Unit 1 CCS piping analysis calculations has identified piping configurations susceptible to this issue that potentially could result in pipe support modifications.
Several such calculations are currently being reanalyzed. No modifications have been identified to date that are required to meet the interim operability criteria limitations; however, some design basis modifications have been identified.
Because of configuration similarities, the scope of the Unit 2 modifications is expected to be similar to that of Unit 1.
No operability modifications were identified during reanalysis of Unit 1 calcule.tions.
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Conclusion:==
Unit I and common piping and pipe supports within the scope of this issue have been shown to meet the interim operability criteria. No Unit 2 modifications are expected in order to meet the operability criteria limitations. Reanalysis of the corresponding Unit 2 piping-and pipe supports is to follow the Unit 1 effort. Design basis modifications are scheduled to be implemented before' restart from the Cycle 7 refueling outage of each unit. The Unit i schedule for resolution of this issue meets the SQN position and the schedaling guidance intent of GL 91-18.
4.
Seal Water Thermal Operating Mode lasut:
During normal power operation, a loss of seal water, injection will' cause the reactor coolant pump seal leakoff and bypass line fluid temperatures to increase above that in the. piping analysis calculations. Westinghouse Electric Corporation has determined'that the fluid temperature can reach 225 degrees F.
The piping analysis calculations used a maximum temperature of 140 degrees F.
This issuo a
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18 applicable to Units 1 and 2 reactor. coolant pump No.l1 seal bypass
. lines.and the Nos. 1, 2, and 3 seal leakoff lines.
This nonconformance is'being tracked in the SQN correctivefaction program as SQPER920353. This issue was reviewed by the NRC staff and the review results are documented in Inspection Report Nos. 50-327, 328/93-49.
EYaluation Basia s '
At the time of the October 1993 NRC meeting, three calculations'had been evaluated for the increased operating temperature, and-both the affected piping and pipe supports met the interim' operability criteria limitations. Since then,'the Unit 1 calculations have'been evaluated for increased operating temperatures. No Unit 1 modifications are required to meet the interim operability criteria limitations.
A review of the Unit 1 piping analysis completed to date indicates that approximately 7 percent of the supports requires modifications to bring these piping segments into compliance with the design _ basis criteria.
These support modifications will be on piping located inside the containment building. Analysis of the Unit 2 seal water:
lines is to follow the. Unit 1 effort.
Because of configuration similarities, the scope of Unit 2 modifications is expected to be similar to that of Unit 1.
Concluainn:
Unit 1 piping and pipe supports within the scope of this issue have been shown to meet the interim operability-criteria. No Unit 2 modifications are expected in order to meet the interim opersbility.
criteria limitations.- Reanalysis.of the corresponding i' nit 2 piping and pipe supports is to follow the Unit 1 effort. -Design basis modifications are scheduled tp be implemented before restart from the Cycle 7 refueling outage of each unit..The Unit 1 schedule for resolution of this issue meets the SQN position and the scheduling-guidance intent of GL 91-18.
5.
SCV Penetration Anchors lasue:
Several steel containment vessel (SCV) penetrations containing flued-head anchors were not properly modeled in the piping calculations. This nonconformance is being tracked in the SQN corrective action program as SQ930564PER. This issue was reviewed by.
the NRC staff and the review results are documented in Inspection Report Nos. 50-327, 328/93-49.
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j Evaluatinalasia:
At the time of the NRC_ inspection, the piping analysis
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calculation for Unit 2 containment spray had been reanalyzed with the correct flued-head anchor model. Two'votential pipe support-modifications were identified. Since then, the extent of condition review for SQ930564PER has been completed. Six: additional piping analysis calculations'having improperly modeled SCV penetration' anchors were identified.
One calculation is the-Unit 1 containment spray cnalysis, and equivalent modifications are' expected.
The modeling_ error in the remaining calculations is much less significant; therefore, operability modifications are cot expected.
Concluaion:
Evaluations of Unit 2 piping and pipe supports la the scope of this issue and comparisons with corresponding Unit 1 features have shown that the interim operability criteria will be met.. Reanalysis of-i the affected calculations and implementation of modifications, if any, will be scheduled to be completed before restart from the-Cycle 7 refueling outage of each unit. The Unit i schedule for resolution of this issue meets the SQN position and the. scheduling-guidance intent'of GL 91-18.
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