ML13331B223
| ML13331B223 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 10/31/1989 |
| From: | Ray H Southern California Edison Co |
| To: | |
| Shared Package | |
| ML13331B222 | List: |
| References | |
| NUDOCS 8911090079 | |
| Download: ML13331B223 (15) | |
Text
BEFORE THE UNITED STATES NUCLEAR REGULATORY COMMISSION Application of SOUTHERN CALIFORNIA EDISON COMPANY and SAN DIEGO GAS & ELECTRIC COMPANY DOCKET NO. 50-206 for a Class 104(b) License to Acquire, Possess, and Use a Utilization Facility as Amendment No. 173 Part of Unit No. 1 of the San Onofre Nuclear Generating Station SOUTHERN CALIFORNIA EDISON COMPANY and SAN DIEGO GAS & ELECTRIC COMPANY, pursuant to 10 CFR 50.90, hereby submit Amendment Application No. 173.
This amendment consists of Proposed Change No. 212 to Provisional Operating License No. DPR-13. Proposed Change No. 212 revises Operating License Condition 3.E.
Proposed Change No. 212 is a request to revise License Condition 3.E, Steam Generator Inspections, to allow a one time 4 month extension of the steam generator inservice inspection interval.
This extension would allow the inspection of the steam generators to occur during the Cycle 11 refueling and thermal shield repair outage beginning on June 30, 1990.
In the event of conflict, the information in Amendment Application No. 173 supersedes the information previously submitted.
8911090079 8910:31 FR ADOCK 05000206 P
-2 Based on the significant hazards analysis provided in the Description and Significant Hazards Consideration Analysis of Proposed Change No. 212, it is concluded that (1) the proposed change does not involve a significant hazards consideration as defined in 10 CFR 50.92, and (2) there is reasonable assurance that the health and safety of the public will not be endangered by the proposed change.
Subscribed on this 31st day of October
, 1989.
Respectfully submitted, SOUTHERN CALIFORNIA EDISON COMPANY B.Harol B. Ray Vice President Subscribed and sworn to before me this 31st day of October OFFICIAL SEAL LINDA L. RULON Notary Public-California
,MORANGE COUNTY My Comm. Exp. Mar. 4, 1992 Notary Public in and for the County of La! -Artgel-e.T, State of California Orange Charles R. Kocher James A. Beoletto Attorneys for Southern California Edison Company By:
Jam' A. Beoletto
UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of SOUTHERN CALIFORNIA
)
EDISON COMPANY and SAN DIEGO GAS &
)
Docket No. 50-206 ELECTRIC COMPANY (San Onofre Nuclear
)
Generating Station, Unit No. 1)
)
CERTIFICATE OF SERVICE I hereby certify that a copy of Amendment Application No. 173 was served on the following by deposit in the United States Mail, postage prepaid, on the 1st day of November
, 1989.
Benjamin H. Vogler, Esq.
Staff Counsel U.S. Nuclear Regulatory Commission Washington, D.C.
20555 David R. Pigott, Esq.
Samuel B. Casey, Esq.
Orrick, Herrington & Sutcliffe 600 Montgomery Street San Francisco, California 94111 L. G. Hinkleman Bechtel Power Corporation P.O. Box 60860, Terminal Annex Los Angeles, California 90060 Michael L. Mellor, Esq.
Thelen, Marrin, Johnson & Bridges Two Embarcadero Center San Francisco, California 94111 Huey Johnson Secretary for Resources State of California 1416 Ninth Street Sacramento, California 95814 Janice E. Kerr, General Counsel California Public Utilities Commission 5066 State Building San Francisco, California 94102
-2 C. J. Craig Manager U.S. Nuclear Projects I ESSD Westinghouse Electric Corporation Post Office Box 355 Pittsburgh, Pennsylvania 15230 A. I. Gaede 23222 Cheswald Drive Laguna Niguel, California 92677 Frederick E. John, Executive Director California Public Utilities Commission 5050 State Building San Francisco, California 94102 Docketing and Service Section Office of the Secretary U.S. Nuclear Regulatory Commission Washington, D.C.
20555 mes A. Beoletto\\
DESCRIPTION AND SIGNIFICANT HAZARDS CONSIDERATION ANALYSIS OF PROPOSED CHANGE NO. 212 TO PROVISIONAL OPERATING LICENSE NO. DPR-13 This is a request to revise the Provisional Operating License to allow a one time extension of the steam generator inspection interval.
DESCRIPTION Technical Specification 4.16, Inservice Inspection of Steam Generator Tubing, Section D.1, requires that inspection of the steam generators be not less than 10 nor more than 24 calendar months after the previous inspection. The purpose of this proposed change is to obtain a one time extension of the inspection interval to 28 calendar months. This proposed change will revise License Condition 3.E, Steam Generator Inspections, to allow the extension of the inspection interval.
This would allow the steam generator inspections to coincide with the Cycle 11 refueling and thermal shield repair outage beginning June 30, 1990.
EXISTING LICENSE CONDITION See Attachment 1 PROPOSED LICENSE CONDITION See Attachment 2 DISCUSSION As a result of the recent issues regarding the thermal shield, SCE has opted to shut down on June 30, 1990, repair the thermal shield and refuel for Cycle
- 11.
The last steam generator inspection was completed March 7, 1988.
Per Technical Specification 4.16.D.1 inspection of the steam generators shall be no more than 24 calendar months after the previous inspection. Therefore, the next scheduled inspection of the steam generators would be no later than March 7, 1990.
In order to forego a shutdown in March 1990 an extension of the steam generator surveillance interval is needed. A one time extension of the inspection interval to 28 calendar months would allow the inspection of the steam generators to occur during the thermal shield repair outage and would avoid a further reduction in the energy generated during Cycle 10.
SUMMARY
It can be shown that a one time 4 month extension of the San Onofre Unit 1 steam generator inservice inspection interval is justified on the basis that:
- 1. Detailed evaluation of the results of the three most recent inspections demonstrates that there are no active degradation
-2 mechanisms affecting the steam generator tubing (and sleeves) and that they will not be degraded beyond the 50% plugging limit (40%
for sleeves) during a 4-month extension in the inspection interval.
- 2. During the proposed extended inspection interval, the unit will have operated for a maximum of 388 EFPD since the last inspection, which is less than a normal fuel cycle.
This is supported in the following analysis.
REGULATORY REQUIREMENTS Technical Specification 4.16 "Inservice Inspection of Steam Generator Tubing" describes the surveillance requirements for the steam generator tubing.
Section D - "Inspection Frequency" states that inservice inspections shall be not less than 10 nor more than 24 calendar months after the previous inspection. The Standard Technical Specifications require a 12 to 24 calendar month inspection interval.
This is based on the guidance provided in Regulatory Guide 1.83, Revision 1, "Inservice Inspection of Pressurized Water Reactor Steam Generator Tubes". The regulatory guide also indicates in Section B.6.c that inspections may be made coincident with refueling outages or any shutdown for plant repair or maintenance.
The objective of the periodic steam generator inservice inspections required by the technical specifications is to monitor the integrity of the steam generator tube primary boundary and provide guidance for corrective action when imperfections are observed. The criteria for corrective action (tube plugging) is in accordance with the guidance of Regulatory Guide 1.121, Bases for Plugging Degraded PWR Steam Generator Tubes, such that tube inspection results are evaluated to ensure tube integrity until the next inspection.
Typically the evaluation of the steam generator tube inspection data and resulting plugging/repair provides assurance of integrity for the nominal length of the next fuel cycle.
SAN ONOFRE UNIT 1 OPERATIONS In response to the intergranular attack (IGA) which caused the major steam generator sleeving outage in 1980-81, significant changes in the operation of San Onofre Unit 1 were implemented to reduce the rate of progression of IGA.
These changes served to reduce the rates of other corrosion mechanisms as well.
Specifically, in 1981 the unit returned to operation on a reduced temperature program which reduced the steam generator inlet (hot leg) temperature by 25F.
Based on the information presented in Reference 1, this temperature reduction is estimated to have lowered corrosion rates by 50 to 70 percent and significantly decreased the probability of tubing failures. As discussed below, inspection results confirm that there has been no progression of IGA in unsleeved tubing since the sleeving outage.
-3 In addition to reducing temperature following the 1980-81 outage, significant improvements in secondary system water chemistry control were implemented. In addition to implementing the Steam Generator Owners Group (EPRI) Water Chemistry Guidelines (to the extent practicable with phosphate steam generator chemistry), the limits on phosphates were tightened to assure the maximum benefit of having phosphate water chemistry control.
SAN ONOFRE UNIT 1 INSPECTION HISTORY Subsequent to the sleeving outage in 1980-81, the San Onofre Unit 1 steam generators have been inspected on four occasions:
EFPD Tubes Inspected Since Last (Percent of Tubes Date Inspection in Service) 03/82 131 3093 (30%)
04/84 0
1645 (16%)
12/85 280 2336 (22%)
03/88 408 7425 (72%)
Based on these inspections, it has been concluded that none of the degradation mechanisms previously experienced [i.e., wastage (thinning), denting, anti vibration bar (AVB) wear, intergranular attack (IGA) and stress corrosion cracking (SCC)] are active in the unsleeved steam generator tubing. Further, a detailed evaluation of the sleeved tubes in service has concluded that the sleeves continue to meet their original design criteria and are not measurably degrading in service.
Reference 2 documents these conclusions for denting, AVB wear, SCC and sleeve integrity. Reference 3 provides further support for the conclusion that IGA is not progressing. Regarding wastage (in the form of cold leg top of the tubesheet indications), Reference 2 concluded that there was limited growth (progression of degradation) of the indications located in the cold leg at the top of the tubesheet. Subsequently, a supplementary evaluation performed in August 1988, demonstrates that these indications are not growing. Finally, the sleeve evaluation documented in Reference 2 has been supplemented as described in Reference 4 confirming that all sleeves in service meet their original design criteria.
INDUSTRY EXPERIENCE With two notable exceptions, industry experience indicates that steam generator degradation does not occur to a measurable extent during plant shutdown periods. The exceptions include one unit that experienced the addition of a sulfur bearing chemical during a long shutdown period and another unit that did not add a reducing agent to steam generators in wet layup for several years. Both of these units suffered tubing failures due to corrosion occurring during layup.
Layup chemistry in the San Onofre Unit 1 Steam generators is closely controlled and as previously noted, there has been no indication of degradation since the 1980-81 outage.
-4 Industry experience and laboratory research, also indicate that corrosion of steam generator tubing occurs primarily during plant operation. Therefore, time in operation [e.g., effective full power days (EFPD) expended] is a good time parameter for predicting tubing degradation. This concept is important to the assessment of an inspection interval extension for San Onofre Unit 1 because the unit will have expended only 388 EFPD (approximately 13 effective full power months) during the 28 month inspection interval being requested.
STEAM GENERATOR TUBE PLUG DEGRADATION As documented in Reference 5, San Onofre Unit 1 has 231 Westinghouse steam generator tube plugs installed which have been identified as being susceptible to stress corrosion cracking as addressed in NRC Bulletin 89-01. These plugs were installed in December 1985 and March 1988. Under current reduced temperature operating conditions these plugs have been conservatively evaluated to have 1187 EFPD until reaching the minimum ligament for plug top release. Therefore, based on a maximum of 796 EFPD expended between December 1985 and June 30, 1990, it is concluded that these plugs will not fail prior to that date.
BASIS FOR INSPECTION INTERVAL EXTENSION There are two distinct technical bases for the one time extension of the steam generator inspection interval for San Onofre Unit 1. Each of these alone is considered sufficient to justify the requested extension.
- 1. The results of the three most recent inspections have been evaluated to determine if any of the degradation mechanisms (new or previously identified) have progressed (are causing additional degradation).
It has been determined that none of the mechanisms identified have been progressing in the tubes or in the sleeves. Therefore, it can be concluded that none of the tubes (or sleeves) in service will degrade beyond the conservative 50% through-wall degradation plugging limit (40% for sleeves) provided in the technical specifications during a 4-month extension in the inspection interval.
In addition, a very thorough evaluation of the installed leak-limiting sleeves indicates that all inservice sleeves are installed properly and predicts that sleeved tube leakage should be well within the established design criteria.
- 2. Subsequent to the last steam generator inservice inspection in March 1988, the unit will have been in a cold shutdown condition for 12 months, and there will have been a maximum of 388 EFPD expended through the end of the 4-month extension (June 30, 1990).
This is significantly less than that expended during a normal fuel cycle (approximately 458 EFPD).
Therefore, as discussed previously, if degradation of the steam generator tubing does occur, it will be much less than would be expected for a normal inspection interval.
-5 REFERENCES
- 1. EPRI Report NP-5971, "1987 EPRI Workshop on Secondary-Side Intergranular Corrosion Mechanisms Proceedings," dated September 1988.
- 2. Letter from M. 0. Medford (SCE) to the U. S. Nuclear Regulatory Commission dated March 25, 1988, regarding Steam Generator Inspections.
- 3. Letter from M. 0. Medford (SCE) to the U. S. Nuclear Regulatory Commission dated May 23, 1989, regarding Steam Generator Inspection Report.
- 4. Licensee Event Report (LER) No.88-018 Revision 1 dated July 12, 1989, regarding Structural Integrity of Steam Generator Sleeved Tubes for which Eddy Current Test Data Does Not Support the Presence of a Roll Expansion May Have Been Compromised Due to Limitations with Eddy Current Test Analysis Methodology.
- 5. Letter from F. R. Nandy (SCE) to the U. S. Nuclear Regulatory Commission dated June 19, 1989, regarding NRC Bulletin 89-01, Failure of Westinghouse Steam Generator Tube Mechanical Plugs.
SIGNIFICANT HAZARDS CONSIDERATION ANALYSIS As required by 10 CFR 50.91(a)(1) this analysis is provided to demonstrate that the proposed license amendment to allow a one time exemption from the steam generator inspection interval requirement for San Onofre Unit 1 does not represent a significant hazards consideration. As demonstrated below, in accordance with the three factor test of 10 CFR 50.92(c), implementation of the proposed amendment was analyzed using the following standards and found not to: 1) involve a significant increase in the probability or consequences of an accident previously evaluated; or 2) create the possibility of a new or different kind of accident from any accident previously evaluated; or 3) involve a significant reduction in a margin of safety.
- 1. Will operation of the facility in accordance with this proposed change involve a significant increase in the probability or consequences of an accident previously evaluated?
Response: No Extension of the steam generator inservice inspection interval to 28 calendar months will not impact the probability or consequences of accidents previously evaluated. The extension will allow the unit to operate 4 months beyond the current technical specification inspection interval.
If degradation mechanisms existed, the additional 4 months of operation might potentially impact the tube wall thickness. Under these circumstances the tube wall thickness
-6 could possibly be reduced beyond the 50% through-wall (40% for sleeves) tube plugging limit as identified in the technical specifications to the extent that the potential for tube failure could be increased, thereby increasing the probability and the consequences of an accident. However, it has been determined that the degradation mechanisms which affect the condition of the tubes are not active, and the condition of the tubes following the 28 month inspection interval will be no different than that considered in previous accident analyses.
The results of the last three inspections indicate the steam generator tube walls are not being reduced and remain above the technical specification limits which would require tube plugging.
This is due to the fact that the degradation mechanisms [i.e.,
wastage, (thinning), denting, antivibration bar (AVB) wear, intergranular attack (IGA) and stress corrosion cracking (SCC)]
which would reduce the tube wall thickness are not progressing within the steam generators.
During the proposed 28 month inspection interval, the plant would operate under power conditions for approximately sixteen (16) calendar months. The plant has been in a cold shutdown condition for 12 months. Historically at San Onofre Unit 1, degradation of the steam generator tube wall has occurred during plant operation.
Cold shutdown conditions minimize corrosion and eliminate flow induced effects which can degrade the steam generator tubing.
In addition, the unit has operated with the current reduced temperature program, THOT reduced by 250 F, since 1981.
This operation has limited the unit's power output. The effect of this operation is to reduce the probability of experiencing tubing degradation due to the reduction in corrosion rates associated with lower temperatures. This is demonstrated by inspection results and the fact that there have been no steam generator leaks due to tubing degradation at San Onofre Unit 1 since 1980.
Imperfections have been detected during recent inservice inspections but only due to the use of improved inspection techniques and technologies. Review of past inspection results have shown that these imperfections have not progressed.
The limits for steam generator tube degradation in the technical specifications consider the acceptability of the tubes for operation until the next inspection, nominally after a complete fuel cycle.
Since the Cycle 11 refueling outage is now scheduled to begin on June 30, 1990, the time of operation since the last steam generator inspection will be 388 EFPD. This is well within the nominal 458 EFPD for a fuel cycle.
It can be concluded that the steam generator tubes will remain within the criteria for plugging during the 28 month inspection interval.
This is due to the fact that: 1) degradation mechanisms
-7 which would reduce tube wall thickness are not active;
- 2) degradation mechanisms are not likely to occur during cold shutdown periods (the plant has beeen in cold shutdown for 12 of the 28 months); 3) operation on a reduced temperature program has reduced the corrosion rates, and 4) plant operation during the extended interval will be less than the operational time for a normal fuel cycle. This ensures that the wall thickness of the steam generator tubes will not be reduced due to degradation mechanisms during the 4 month extension. It is expected that the condition of the steam generator tubes as a result of the 28 month inspection interval will be no different than that considered in previous accident analyses.
As a result, the probabilities and consequences of an accident are not affected since the steam generator tubes will not have significantly changed during the 4 month extension of the 24 month inspection interval.
Therefore, the operation of San Onofre Unit 1 in accordance with this proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated.
- 2. Will operation of the facility in accordance with this proposed change create the possibility of a new or different kind of accident from any accident previously evaluated?
Response: No Extension of the steam generator inservice inspection interval to 28 calendar months does not create the possibility of a new or different kind of accident. The extension will allow the unit to operate 4 months beyond the current technical specification inspection interval.
It has been shown in the response to Item 1 above, that the degradation mechanisms which affect the condition of the tubes are not active and their condition following the 28 month inspection interval will be no different than that considered in previous accident analyses. Therefore, the operation of San Onofre Unit 1 in accordance with this proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.
- 3. Will operation of the facility in accordance with this proposed change involve a significant reduction in margin of safety?
Response: No Extension of the steam generator inspection interval to 28 months will not affect the margin of safety. It has been shown in the response to Item 1 above that the degradation mechanisms which affect the condition of the tubes are not active and their condition following the 28 month inspection interval will be no different than that considered in previous accident analyses.
Therefore, it can be concluded that degradation of the steam generator tubes beyond a condition which will impact the margin of
-8 safety will not occur, and the operation of the facility in accordance with this proposed change does not involve a significant reduction in margin of safety.
SAFETY AND SIGNIFICANT HAZARDS DETERMINATION Based on the extended outages during the steam generator inspection interval and the results of the previous steam generator inspections, it is concluded that: (1) Proposed Change No. 212 does not constitute a significant hazards consideration as defined by 10 CFR 50.92; and (2) there is reasonable assurance that the health and safety of the public will not be endangered by the proposed change; and (3) this action will not result in a condition which significantly alters the impact of the station on the environment as described in the NRC Environmental Statement. - Existing License Condition - Proposed License Condition JAH2:pcn2l2tx
ATTACHMENT 1 EXISTING LICENSE CONDITION
E. Steam Generator Insoections During the refueling outage scheduled to begin no later than November 30, 1985, Southern California Edison shall perform an 89 inspection of the steam generators.
The inspection program shall be 6/5/85 submitted to the Commission at least 45 days prior to the scheduled shutdown. Commission approval shall be obtained before resuming power operation following this inspection.
F. Deleted 37 10/31/78 G. Physical Protection SCE shall fully implement and maintain in effect all provisions of the Commission-approved physical security, guard training and qualification, and safeguards contingency plans including amendments made pursuant to provisions of the Miscellaneous Amendments and Search Requirements revisions to 10 CFR 73.55 (51 FR 27817 and 27822) and to the authority of 10 CFR 50.90 and 10 CFR 50.54(p).
The plans, which contain Safeguards Information protected under 108 10 CFR 73.21, are entitled:
"San Onofre Nuclear Generating Station, 9/6/88 Units 1, 2, and 3 Physical Security Plan," with revisions submitted through April 22, 1988; "San Onofre Nuclear Generating Station.
Units 1, 2, and 3 Security Force Training and Qualification Plan,"
with revisions submitted through October 22, 1986; and "San Onofre Nuclear Generating Station, Units 1, 2, and 3, Safeguards Contingency Plan," with revisions submitted through December 29, 1987. Changes made in accordance with 10 CFR 73.55 shall be implemented in accordance with the schedule set forth therein.
SAN ONOFRE - UNIT 1 Revised: 12/21/88