ML20206H278
| ML20206H278 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 05/05/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20206H276 | List: |
| References | |
| NUDOCS 9905110131 | |
| Download: ML20206H278 (5) | |
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WASHING TON. D. C. 20555
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. SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.176TO FACILITY OPERATING LICENSE NO. DPR FLORIDA POWER CORPORATION CRYSTAL RIVER UNIT 3 DOCKET NO. 50-302
1.0 INTRODUCTION
By [[letter::3F0199-04, LAR 243,Rev 0 to License DPR-72,requesting one-time Rev of ITS to Extend Insp Interval for OTSG Tubes to Coincide with Planned Operating Cycle.Rev 0 to Calculation M-99-0017 & Rev 0 to Calculation AES-C-3543-1 Encl|letter dated January 27,1999]], Florida Power Corporation (the licensee) submitted for U. S.
Nuclear Regulatory Commission (NRC) staff review a request for an amendment to the Crystal River Unit 3 Improved Technical Specifications (ITS). The requested change would revise ITS 5.6.2.10 to allow a one-time (cycle 11) extension of the specified steam generator tube inspection interval.
In Spring 1996, Crystal River completed Cycle 10 operation, and the licensee performed routine inspection of steam generator tubes during refueling outage 10R. The licensee started Cycle 11 on May 15,1996. After brief operation, the unit was shut down on September 2, 1996, to repair equipment and resolve design margin issues. On August 1,1997, while the unit was still shut down, the licensee completed a baseline inspection of all steam generator tubes using a bobbin coil probe. The upper tubesheet rolljoints were inspected using a rotating pancake coil and a + point coil. The licensee resumed Cycle 11 on February 5,1998 and has operated the unit continuously since that time. The licensee plans to complete Cycle 11 on or about October 1,1999, and to inspect steam generator tubes during the subsequent refueling outage.
The Crystal River ITS requires that steam generator tube inspection be performed at intervals of not more than 24 calendar months after the last inspection. On the basis of the August 1, 1997, inspection and ITS required intervals, the next tube inspection must be performed on or before August 1,1999. If the next scheduled inspection is performed in August 1999, the licensee would shut down Crystal River Unit 3 approximately 2 calendar months before the completion of Cycle 11 and a refueling outage currently scheduled for October 1999. The licensee, therefore, proposed this one-time extension of about 2 calendar months to permit it to perform the required inspection after the completion of Cycle 11 during the refueling outagl it should be noted that the unit will have operated only 21.6 months between the August 1, 1997, inspection and the scheduled October 1999 refueling outage.
2.0 EVALUATION The staff focused its evaluation on the licensee's assessment of structural and leakage integrity of the steam generator tubes, the primary-to-secondary leakage limits, and steam 9905110131 990505 PDR ADOCK 05000302 P
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generator wet lay-up practices to ascertain that the tubes are acceptable for continued operation during the extended inspection interval, an extension of approximately 2 ca'endar j
months, until the end of Cycle 11.
- Steam generator tube integrity is demonstrated by condition monitoring and operational assessments. NRC Regulatory Guide (RG) 1.121 recommends certain analytical and experimentaljustifications for tube integrity. RG 1.121 recommends that the tubes maintain a I
minimum safety margin of 3 against rupture under normal operating conditions (i.e., the tubes will not burst under differential pressure equal to 3. times that of normal operating differential
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pressure). In addition, RG 1.121 recommends a safety margin consistent with Section 111 of j
American Society of Mechanical Engineers Code against failure under postulated accidents throughout the operating cycle. In addition, steam generator tube degradation is managed-through a combination of several approaches to provide defense-in-depth. These approaches include inservice inspections, technical specification limits on primary-to-secondary leakage, control of secondary water chemistry, leakage monitoring, and operator actions.
. The dominant tube degradation mechanisms in Crystal River steam generators "A" and "B" are (1) volumetric " pit-like" intergranular attack (IGA) in the first span of the tubes above the lower tubesheet, (2) outside diameter stress corrosion cracking (ODSCC) and/or IGA in the upper bundle free span region, (3) primary water stress corrosion cracking (PWSCC) at the roll transition region in the upper tubesheet, and (4) upper tubesheet tube end anomalies. These degradation mechanisms have been addressed in several previously-submitted assessments, which the staff has reviewed. The January 27,1999, submittal contains an update of the assessments and they are discussed below.
- The licensee has detected volumetric IGA in the first span of the steam generator tubes since 1990. _in a May 18,1998, submittal, the licensee provided an operational assessment of the volumetric IGA that used a safety factor of 1.4 for accident conditions and a safety factor of 3.0 fo'r normal operation. The largest indication retumed to service was determined to satisfy the 3 times differential pressure criterion at the end of Cycle 11 based on projected flaw growth rates
. and consideration of inspection measutoment uncertainty. The licensee projected a zero
-leakage rate for normal and accident conditions at the end of Cycle 11. The licensee also performed in situ pressure tests of the bounding IGA indications in 1996, and destructive tests on removed tubes in 1992 and 1994. The tests showed that the bounding indications satisfied the 3 times differential pressure criterion. In a letter to the licensee dated Nowember 17,1998, the staff concluded that the limiting volumetric IGA flaw is projected to remain within safety margins consistent with Regu!atory Guide 1.121.
~_ The licensee detected two free span axial ODSCC/lGA indications in a tube in the "A" steam generator during the 1997 inspection. The tube was plugged. Similar axial ODSCC/lGA indications have been found in other Babcock & Wilcox (B&W) steam generators. B&W plant owners have performed laboratory examinations on more than 12 tube sections and over 20 in situ pressure tests of tubes containing free span axialIGA indications. The examinations and in situ tests showed that the tubes did not burst or leak at three times normal operating differential pressure. The licensee's operational assessment showed that the limiting ODSCC/lGA flaw depth at the end of Cycle 11 will satisfy the 3 times differential pressure criterion; The assessments'showed that leak rates through these indications are projected to m
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- be minimal at the end of Cycle 11 (i.e., less than 1 gallon per minute (gpm]) and will not exceed radiological dose limits.-
' The licensee detected axial PWSCC indications in the roll transition region of the tubes in the upper tubesheet during the 1997 inspection. The affected tubes were plugged, in the May 18, 1998, submittal, the licensee's operational assessment of the PWSCC indications showed that the tube leakage rate would be below the allowable limit of 1 gpm under accident conditions, The NRC staff believes that the likelihood of tube rupture as a result of PWSCC indications in the roll transition region of the upper tubesheet is minimal because of the restraint imposed on the tubes by the tubesheet.
The licensee detected tube end anomalies, which are indications at the seal welds at the end of steam generator tubes. By a letter dated June 18,1998, the licensee submitted an -
amendment request to allow steam generator tubes having tube end anomalies to remain in 1
service for a limited time. The licensee demonstrated that the tube end anomalies will have a minimum impact on the primary-to-secondary leak rate under postulated steam line break conditions. The tubesheet provides constraint that will preclude tube rupture initiated from any tube end anomalies, in a letter dated July 30,1998, the staff issued amendment No.169 to allow the tube end anomalies to remain in service for the remainder of Cycle 11.
1 Crystal River ITS limits the primary-to-secondary leakage for normal operation to 150 gallons per day per steam generator. This is a restrictive leakage limit and is consistent with the recommended leakage limit in NRC Generic Letter 95-05. The primary-to-secondary leakage is monitored by gamma detectors located in the condenser vacuum pump exhaust with i
indicators in the control room. The leakage limit and monitoring system will ensure that the operator has sufficient time to take appropriate actions should leakage occur.
During the extended shutdown, the licensee placed the steam generators in wet lay-up to minimize steam generator tube corrosion. The licensee followed, and in some areas exceeded, the wet lay-up program specified in Electric Power Research Institute (EPRI)
Report, "PWR Secondary Water Chemistry Guidelines," TR-102134, Revision 4, November 1996. The EPRI guidelines on water chemistry and associated monitoring system were established to reduce steam generator tube corrosion.
The staff has determined that the structuralintegrity of the steam generator tubes is acceptable for continued operation until the end of Cycle 11 because the tubes at the end of
' Cycle 11 will satisfy the safety margins of Regulatory Guide 1.121. The licensee has
' demonstrated that tube degradation in Crystal River is managed consistent with generally
-accepted industry practices and ITS requirements.' Since there is reasonable assurance that the structuralintegrity of the steam generator tubes will be maintained until the end of
' Cycle 11, it is acceptable to extend the inspection interval by approximately 2 months to coincide with the end of the operating cycle.
Proposed Chance to Imoroved Technical Specifications The licensee proposed to include the following paragraph in ITS 5.6.2.10.3
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. l The above required inservice inspections of OTSG tubes shall be performed at the following frequencies except, a one-time change for Cycle 11 is granted to modify the scheduled inspection frequency from a calendar-based interval to an interval of up to 21.6 months of operating time at a temperature of 500* F or above (measured at the hot leg side). This will allow the OTSG tube inspection to coincide with Refuel Outage 11R[.]
The staff finds that the proposed change is acceptable on the basis of its review of the information submitted by the licensee, as set forth above.
3.0 STATE CONSULTATION
Based upon a letter dated March 8,1991, from Mary E. Clark of the State of Florida, Department of Health and Rehabilitative Services, to Deborah A. Miller, Licensing Assistant, U.S. NRC, the State of Florida does not desire notification of issuance of license amendments.
4.0 ENVIRONMENTAL CONSIDERATION
S The amendment changes requirements with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding (64 FR 11962). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the
-issuance of the amendment.
5.0 CONCLUSION
Besed on its review of the licensee's proposal, the staff has determined that the proposed change to the Crystal River, Unit 3, ITSs will continue to provide adequate assurance that the steam generator tubes will maintain adequate structural and leakage integrity for the remainder of Cycle 11. The licensee has implemented restrictive primary-to secondary leakage limits and has a leakage monitoring system. The licensee has followed EPRI guidelines on wet !ay-up of steam generators during extended shutdown. The proposed changes to ITS 5.6.2.10 are acceptable and they may be incorporated into Crystal River Unit 3 ITSs. The staff concludes that (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: John Tsao, DE/EMCB Date:
May 5, 1999 I
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Mr. John Paul Cowan CRYSTAL RIVER UNIT NO. 3 Florida Power Corporation ec:
~ Mr. R. Alexander Glenn Ms. Sherry L. Bernhoft, Director Corporate Counsel Nuclear Regulatory Affairs (SA2A) l Florida Power Corporation
. Florida Power Corporation MAC-ASA Crystal River Energy Complex P.O. Box 14042 15760 W. Power Line Street l
St. Petersburg, Florida 33733-4042 Crystal River, Florida 34428-6708 Mr. Charles G. Pardee, Director Senior Resident inspector Nuclear Plant Operations (NA2C)
Crystal River Unit 3 Florida Power Corporation U.S. Nuclear Regulatory Commission Crystal River Energy Complex 6745 N. Tallahassee Road 15760 W. Power Line Street -
Crystal River, Florida 34428 Crystal River, Florida 34428-6708 Mr. Gregory H. Halnon I
Mr. Michael A. Schoppman Director, Quality Programs (SA2C)
Framatome Technologies Inc.
Florida Power Corporation 1700 Rockville Pike, Suite 525 -
Crystal River Energy Complex 1
Rockville, Maryland 20852 15760 W. Power Line Street Crystal River, Florida 34428-6708 Mr. William A. Passetti, Chief Department of Health Bureau of Radiation Control l
2020 Capital Circiel, SE, Bin #C21 Tallahassee, Florida 32399-1741 Attorney General Department of Legal Affairs
' The Capitol Tallahassee, Florida 32304 Mr. Joe Myers, Director i
Division of Emergency Preparedness l
Department of Community Affairs 2740 Centerview Drive l
Tallahassee, Florida 32399-2100 Chairman Board of County Commiss:oners Citrus County 110 North Apopka Avenue inverness, Florida 34450-4245 I
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