ML081710055
| ML081710055 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 06/20/2008 |
| From: | Balwant Singal NRC/NRR/ADRO/DORL/LPLIV |
| To: | Blevins M Luminant Generation Co |
| Singal, Balwant, 415-3016, NRR/DORL/LPL4 | |
| References | |
| TAC MD8067 | |
| Download: ML081710055 (9) | |
Text
June 20, 2008 Mr. M. R. Blevins Executive Vice President
& Chief Nuclear Officer Luminant Generation Company LLC ATTN: Regulatory Affairs P. O. Box 1002 Glen Rose, TX 76043
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION, UNIT 2 -
SUMMARY
OF CONFERENCE CALL REGARDING THE SPRING 2008 STEAM GENERATOR TUBE INSPECTIONS (TAC NO. MD8067)
Dear Mr. Blevins:
On April 7 and April 16, 2008, the U.S. Nuclear Regulatory Commission (NRC) staff participated in conference calls with representatives of Luminant Generation Company LLC (the licensee) regarding the ongoing steam generator (SG) tube inspection activities at Comanche Peak Steam Electric Station, Unit 2. The discussions were based on a brief summary of the scope and results of the SG tube inspections provided by the licensee.
Based on the information provided by the licensee, the NRC staff did not identify any issues that warranted immediate follow-up action. A summary of the conference calls is enclosed.
Information provided by the licensee is also included as an attachment to the enclosure.
If you have any questions regarding this matter, I may be reached at 301-415-3016.
Sincerely,
/RA/
Balwant K. Singal, Senior Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-446
Enclosure:
As stated cc w/encl: See next page
- Memo dated 6/2/2008 OFFICE NRR/LPL4/PM NRR/LPL4/LA NRR/CSGB/BC NRR/LPL4/BC NRR/LPL4/PM NAME BSingal JBurkhardt AHiser (*)
THiltz BSingal DATE 6/20/08 6/19/08 6/2/08 6/20/08 6/20/08
Comanche Peak Steam Electric Station (6/10/2008) cc:
Senior Resident Inspector U.S. Nuclear Regulatory Commission P.O. Box 2159 Glen Rose, TX 76403-2159 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 612 E. Lamar Blvd., Suite 400 Arlington, TX 76011-4125 Mr. Fred W. Madden, Director Regulatory Affairs Luminant Generation Company LLC P.O. Box 1002 Glen Rose, TX 76043 Timothy P. Matthews, Esq.
Morgan Lewis 1111 Pennsylvania Avenue, NW Washington, DC 20004 County Judge P.O. Box 851 Glen Rose, TX 76043 Environmental and Natural Resources Policy Director Office of the Governor P.O. Box 12428 Austin, TX 78711-3189 Mr. Richard A. Ratliff, Chief Bureau of Radiation Control Texas Department of Health 1100 West 49th Street Austin, TX 78756-3189 Mr. Brian Almon Public Utility Commission William B. Travis Building P.O. Box 13326 1701 North Congress Avenue Austin, TX 78701-3326 Ms. Susan M. Jablonski Office of Permitting, Remediation and Registration Texas Commission on Environmental Quality MC-122 P.O. Box 13087 Austin, TX 78711-3087 Anthony P. Jones Chief Boiler Inspector Texas Department of Licensing and Regulation Boiler Division E.O. Thompson State Office Building P.O. Box 12157 Austin, TX 78711
ENCLOSURE
SUMMARY
OF CONFERENCE CALL WITH LUMINANT GENERATION COMPANY LLC REGARDING THE SPRING 2008 STEAM GENERATOR TUBE INSPECTION RESULTS AT COMANCHE PEAK STEAM ELECTRIC STATION, UNIT 2 On April 7, 2008, the staff of the Steam Generator Tube Integrity and Chemical Engineering Branch of the Division of Component Integrity participated in a conference call with representatives of Luminant Generation Company LLC (the licensee) regarding the ongoing steam generator (SG) tube inspection activities at Comanche Peak Steam Electric Station (CPSES), Unit 2. The following summarizes the April 7, 2008, conference call.
CPSES Unit 2 has four Westinghouse Model D5 SGs that each have 4570 thermally treated Alloy 600 tubes. These tubes have an outside diameter of 0.750 inches and a nominal wall thickness of 0.043 inches. The tubes are supported at various locations by stainless steel, broached, tube support plates (TSPs) with quatrefoil-shaped holes and V-shaped chrome-plated Alloy 600 anti-vibration bars (AVBs). The tubes were hydraulically expanded for the full depth of the 21-inch thick tubesheet.
Prior to the call on April 7, the licensee was provided with discussion points to help facilitate the conference call (refer to Agencywide Document Access and Management System (ADAMS)
Accession No. ML080450262). In support of the phone call, the licensee provided the attached document. A follow-up conference call was held on April 16, 2008, during which the licensee provided additional information.
The following abbreviations were used by the licensee in the attachment:
+Pt
- +Point' AVB
- Anti-vibration Bar BLG
- Bulge ECT
- Eddy Current Testing FOSAR +- Foreign Object Search and Retrieval HL
- Hot-leg HTE
- Hot-leg Tube End MCI
- Multiple Circumferential Indications OXP
- Overexpansion RPC
- Rotating Pancake Coil SAI
- Single Axial Indication SCI
- Single Circumferential Indication TEH
- Tube End Hot-leg TS
- Tube Sheet TTS
- Top of the Tubesheet TW
- Through Wall
At the time of the April 7 call, SG tube inspections were in progress. Additional clarifying information or information not included in the material provided by the licensee is summarized below:
SG tube inspections were approximately 60 - 65 percent complete.
The two axial indications found in SG 1 and 2 ranged from 0.04 - 0.12 inches from the tube end.
The two multiple circumferential indications found in SG 3 were located in two different tubes. One had an arc length of approximately 175 degrees (°) and the other had an arc length of approximately 140°.
The two single circumferential indications found in SG 4 each had an arc length of approximately 80°.
As a result of detecting indications near the tube end, the licensee expanded their inspections to include 100 percent of the tube ends in all four SGs.
The licensee was not planning to inspect the cold-leg tube ends. The licensee indicated that the number of indications detected on the hot leg was small, none of the indications were structurally significant, the indications may not be cracks (e.g., they may be anomalies from manufacturing), and the operating temperature on the cold leg was less than on the hot leg.
The licensee indicated this was the last planned inspection prior to the mid-point of the second sequential period for the CPSES, Unit 2 SGs.
The licensee indicated that the tack expansions at the tube ends were performed by mechanical rolling of the tube ends.
At the time of the call, there was no in-situ pressure testing or tube pulls planned, but the licensee indicated that if an indication was found that met the limits for an in-situ pressure test, then equipment would be mobilized.
Foreign object search and retrieval (FOSAR) was planned for all four SGs. An in-bundle visual inspection was being performed in SG 3. This inspection was to include the top of the tubesheet and near the inspection ports by the top two tube support plates (L and P plates). The purpose of the inspections was to assess fouling and tube support plate conditions. At the time of the call, no significant fouling of the tube support plate holes had been detected, and no structural defects were identified. Sludge lancing of all four SGs was scheduled for this outage.
For loose part detection, the licensee was using a combination of visual and eddy current methods. The visual inspection included FOSAR at the top of the tubesheet and at baffle plate B. At the time of the call, no loose parts had been detected visually; however, several possible loose parts were identified through
the eddy current inspections. Visual inspections of these areas indicated the indications were from scale deposits near the tubes. The licensee indicated that the scale deposits might have migrated near the tubes during a reactor trip approximately 2 weeks prior to the start of the refueling outage. The licensees typical practice is to try to remove any detected loose parts. If the part cannot be removed, the tube is plugged (the surrounding tubes may also be plugged). The eddy current inspections near the top of the tubesheet were biased to the peripheral tubes on the hot leg. On the cold leg, eddy current inspections were performed at baffle plate B.
On April 16, 2008, a follow-up call was held to discuss the licensees basis for not inspecting the tube end on the cold-leg side of the SG. With respect to the inspections at the cold-leg tube end, the NRC staff had the following comment:
If the cold-leg tube end is considered susceptible to cracking, the licensee must ensure they satisfy the prescriptive inspection requirements in their technical specifications for this region. For example, 50 percent of the tubes must be inspected (with probes capable of detecting crack-like indications) by the outage nearest the mid-point and 100 percent of the tubes must be inspected by the endpoint of the sequential period. The 50-percent sample of the tubes can be performed at the first outage after the midpoint of the period. In addition, these inspections can be prorated if it is concluded that the cold-leg tube ends were not susceptible to cracking until after the first inspection in the sequential period (NRC letter dated November 9, 2007 to Mr. Jim Riley of Nuclear Energy Institute, ADAMS Accession No. ML073110083, providing clarifications to the SG tube inspection requirements). In addition, the licensee must be able to demonstrate that they will maintain tube integrity as a result of any flaws that may exist in the tube ends on the cold leg.
Based on the information provided, the staff did not identify any issues that warranted immediate follow-up action.
ATTACHMENT Steam Generator Tube Inspections CPSES, Unit 2 (Spring 2008)
Discussion Points and Information Provided by Luminant Generation Company LLC (1)
Discuss any trends in the amount of primary to secondary leakage observed during the recently completed cycle.
Response
There has been no indication of primary to secondary leakage associated with SG tube degradation.
(2)
Discuss whether any secondary -side pressure tests were performed during the outage and the associated results.
Response
There has been no secondary side pressure tests performed during this outage.
(3)
Discuss any exceptions taken to the industry guidelines.
Response
No exceptions have been taken to the industry guidelines.
(4)
For each SG, provide a description of the inspections performed including the areas examined and the probes used (e.g., dents/dings, sleeves, expansion-transitions, U-bends with rotating probe), the scope of the inspection (e.g., 100 percent of dents/dings greater than 5 volts and a 20 percent sample between 2 and 5 volts), and the expansion criteria.
Response
Item Area Examined Probe Scope Expansion Criteria 1
Full Length (Note 1, 2)
Bobbin 55%
Note 4 2
Row 1 and 2 U-bends
+ Pt RPC 50%
Note 5 3
TTS +/- 3
+ Pt RPC 50%
Note 5 4
TEH +2 (Note 3)
+ Pt RPC 50%
Note 5 5
OXP/BLG in TS
+ Pt RPC 50%
Note 5 6
Expanded tubes in preheater baffle plate B and D
+ Pt RPC 50%
Note 5 7
Dents >= 2 volts at H3 TSP
+ Pt RPC 100%
N/A 8
Dents/Dings >= 5 volts HL and U-bends
+ Pt RPC 50%
Note 5 Notes:
- 1.
See item 2. Due to the bend radius of the row 1 and 2 tubes a bobbin probe is used for the straight portion of the tube only and the + Pt RPC is used for the U-bend portion.
- 2.
Includes tubes with previous indications (e.g. AVB wear) and tubes with possible elevated residual stress.
- 3.
Same population of tubes as item 3.
- 4.
For wear indication expansion shall be per the Technical specification.
- 5.
Expand to 100% of the affected area in the affected SG.
(5)
For each area examined (e.g., tube supports, dents/dings, sleeves, etc.) provide a summary of the indications identified to-date of each degradation mode (e.g., number of circumferential primary water stress-corrosion cracking (PWSCC) indications at the expansion transition). For the most significant indication in each area, provide an estimate of the severity of the indication (e.g., provide the voltage, depth, and length of the indication). In particular, address whether tube integrity (structural and accident-induced leakage integrity) was maintained during the previous operating cycle.
In addition, discuss whether any location exhibited a degradation mode that had not previously been observed at this location at this unit (e.g., observed circumferential PWSCC at the expansion transition for the first time at this unit).
Response
Area SG 1 SG 2 SG 3 SG 4 TTS No degradation No degradation No degradation No degradation OXP/BLG No degradation No degradation No degradation No degradation Dents/Dings No degradation No degradation No degradation No degradation AVB **
4, 0>40%
5, 0>40%
5, 0>40%
0 HTE ***
1 SAI 1 SAI 2 MCI 2 SCI AVBs (U-bend inspections) are still in progress and these numbers represent new indications.
Not previously observed at CPNPP Unit 2 SAI - Single Axial Indication MCI - Multiple Circumferential Indications SCI - Single Circumferential Indication (6)
Describe repair/plugging plans.
Response
All cracks will be plugged on detection. Wear will be plugged based on the Technical Specification plugging limit of 40% TW.
(7)
Describe in-situ pressure test and tube-pull plans and results (as applicable and if available).
Response
There are no plans to perform in-situ pressure tests or tube pulls. If an indication is found that meets the limits for an in-situ pressure test then the equipment will be mobilized.
(8)
Provide the schedule for SG-related activities during the remainder of the current outage.
Response
ECT will continue through - 4/9/08 FOSAR will begin on 4/5/08 and complete on 4/12/08 In tube bundle video in SG 3 will begin on 4/5/08 and complete on 4/7/08 Sludge Lance will begin on 4/6/08 and complete on 4/11/08
(9)
Discuss the following regarding loose parts:
what inspections are performed to detect loose parts:
Response
FOSAR at TTS and Baffle Plate B
+Pt RPC at the TTS and Baffle Plate B a description of any loose parts detected and their location within the SG
Response
None to date if the loose parts were removed from the SG
Response
None to date will remove any that are retrievable. An Engineering Evaluation will be performed on those that must be left if the affected tubes are not plugged.
indication of tube damage associated with loose parts
Response
None to date the source or nature of the loose parts, if known
Response
Need to review FOSAR tapes.
(10)
Discuss the results of any secondary-side inspections.
Response
No indication of degradation. Tube scale is minimal, no sludge pile, no loose parts identified, no structural defects identified.
(11)
Discuss any unexpected or unusual results.
Response
None to date.