ML083010562
| ML083010562 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 11/06/2008 |
| From: | Thomas Wengert Plant Licensing Branch III |
| To: | Wadley M Northern States Power Co |
| Wengert, Thomas NRR/DORL 415-4037 | |
| References | |
| TAC MD9465 | |
| Download: ML083010562 (4) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 November 6, 2008 Mr. Michael D. Wadley Site Vice President Prairie Island Nuclear Generating Plant Northern States Power - Minnesota 1717 Wakonade Drive East Welch, MN 55089
SUBJECT:
PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNIT 2 -
SUMMARY
OF CONFERENCE TELEPHONE CALL REGARDING THE 2008 STEAM GENERATOR TUBE INSPECTIONS (TAC NO. MD9465)
Dear Mr. Wadley:
On October 1,2008, the U.S. Nuclear Regulatory Commission (NRC) staff participated in a conference call with Prairie Island Nuclear Generating Plant, Unit NO.2 representatives regarding the ongoing steam generator (SG) tube inspection activities conducted during their 2008 outage. The NRC follows the results of the industry's SG inspections in order to maintain an awareness of the condition of the SGs and the types of tube degradation mechanisms that are active.
The enclosed documentation of the phone call is provided to Northern States Power Co.
Minnesota (NSPM) for information. The slides provided by NSPM in support of this discussion (Agencywide Documents Access and Management System (ADAMS) Accession No. ML082890872) are available to the public.
Based on the information provided during the conference call, the NRC staff did not identify any issues that warranted additional follow-up action at this time. If there are any questions, please contact me at 301-415-4037.
Sincerely, Ie",,_<~~f-Thomas J. Wengert, Senio~-Project Manager Plant Licensing Branch 111-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-306
Enclosure:
Conference Call Summary cc: Distribution via ListServ
SUMMARY
OF CONFERENCE CALL WITH PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNIT 2 REGARDING THE 2008 STEAM GENERATOR TUBE INSPECTION RESULTS DOCKET NO. 50-306 On October 1, 2008, U.S. Nuclear Regulatory Commission (NRC) staff participated in a conference call with Prairie Island Nuclear Generating Plant (PINGP), Unit 2 representatives regarding the 2008 steam generator (SG) tube inspection activities.
Prior to the conference call, the licensee provided several slides to facilitate the discussion. These slides are located in the NRC's Agencywide Documents Access and Management System (ADAMS) under Accession No. ML082890872.
The two SGs at PINGP Unit 2 are Westinghouse model 51 SGs. Each SG contains 3,388 mill-annealed Alloy 600 tubes. Each tube has a nominal outside diameter of 0.875 inches and a nominal wall thickness of 0.050 inches. The tubes were roll-expanded into the tubesheet at both ends for approximately 2.75 inches (i.e., they are expanded for only a fraction of the tubesheet thickness and are considered partial depth hard-rolled tubes). The tubes are supported by a number of carbon steel tube support plates. The original anti-vibration bars were removed and replaced. The tubes installed in rows 1 and 2 were subjected to an in-situ thermal stress relief in May 2000. To repair defects, many tubes have been roll-expanded into the tubesheet region above the original factory roll expansions. The hot-leg temperature at PINGP Unit 2 has been approximately 590 degrees Fahrenheit since commencement of initial operation.
Additional clarifying information or information not included in the slides provided by the licensee is summarized below.
- The primary to secondary leakage in SG 22 was trending up at the end of the outage. The licensee attributed this trend to the dilution of the primary system.
- In the Table titled "Inspection Plan":
>- The "Hot Leg Tubesheet" was to be inspected from the tube end to 3 inches above the top of the tubesheet and in the sludge pile zone (center region of the steam generator) from the tube end to 6 inches above the top of the tubesheet.
~ The "Baseline New Re-Rolls" were to be inspected with Bobbin and Rotating coils.
~ The "Plug Visual" was to be conducted in order to ensure that all the plugs (hot and cold leg) were present. The inspection was to be recorded with a narrative on DVD row by row and reviewed by Quality Control.
~ The inspections of the dents and dings were to be conducted on the hot and cold legs ENCLOSURE
- 2
- In the Table titled "Analysis Status": In the row titled "Plug Visual" the SG 21 Cold was 80% complete, the SG 22 Hot was 98% complete, and the SG 22 Cold was 97% complete. The licensee stated that, at the time of the teleconference, Quality Control was still performing its review of the plug inspection.
- In the Table titled "SG 21 Analysis Results to Date":
~ The results of the indications below the F* and EF* distance would be included in the 180-day report and the results were acceptable.
~ The volumetric wear at the "Old AVB's" has not changed in size (i.e.,
minor variation as a result of eddy current uncertainty).
~ The "Volumetric Wear at Possible Loose Parts (PLP's) (1998 In Situ Neighbors)" is at the 4th hot leg support plate. The loose part had been removed prior to the 2008 outage. In 1998, 4 tubes were plugged as a result of this loose part. In a subsequent outage prior to 2008, the loose part was removed and two tubes were deplugged. These indications have not changed in size since the part was removed.
~ The "Axial Outer Diameter Stress Corrosion Cracking (ODSCC) at Hot Leg Crevice" with a length of 1.19 inches did not extend outside the tubesheet but was within an inch of the top of the tubesheet. This indication was not in situ pressure tested since the licensee stated that they have detected and successfully pressure-tested more severe ODSCC indications. The licensee stated that this indication was well within condition monitoring limits.
- There were no new mechanisms of degradation.
- The licensee stated that the criterion for assessing noise in the U-bend was consistent with previous inspections. All the U-bend data were checked for excessive noise. The licensee stated that, if the noise had exceeded the criterion, then they would re-inspect the tube and if it still did not meet the criterion, the tube would be plugged. At the time of the call, all tubes satisfied the noise criterion.
The NRC staff did not identify any issues that required follow-up action at this time.
However, the staff asked to be notified in the event that any unusual conditions were detected during the remainder of the outage.
November 6, 2008 Mr. Michael D. Wadley Site Vice President Prairie Island Nuclear Generating Plant Northern States Power - Minnesota 1717 Wakonade Drive East Welch, MN 55089
SUBJECT:
PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNIT 2 -
SUMMARY
OF CONFERENCE TELEPHONE CALL REGARDING THE 2008 STEAM GENERATOR TUBE INSPECTIONS (TAC NO. MD9465)
Dear Mr. Wadley:
On October 1, 2008, the U.S. Nuclear Regulatory Commission (NRC) staff participated in a conference call with Prairie Island Nuclear Generating Plant, Unit NO.2 representatives regarding the ongoing steam generator (SG) tube inspection activities conducted during their 2008 outage. The NRC follows the results of the industry's SG inspections in order to maintain an awareness of the condition of the SGs and the types of tube degradation mechanisms that are active.
The enclosed documentation of the phone call is provided to Northern States Power Co.
Minnesota (NSPI\t1) for information. The slides provided by NSPM in support of this discussion (Agencywide Documents Access and Management System (ADAMS) Accession No. ML082890872) are available to the public.
Based on the information provided during the conference call, the NRC staff did not identify any issues that warranted additional follow-up action at this time. If there are any questions, please contact me at 301-415-4037.
Sincerely, lRAI Thomas J. Wengert, Senior Project Manager Plant Licensing Branch 111-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-306
Enclosure:
Conference Call Summary cc: Distribution via ListServ DISTRIBUTION:
PUBLIC RidsNrrPMPrairielsland Resource KKarwoski, NRR LPL3-1 RIF RidsNrrDorl Resource RidsNrrDciCsgb Resource EWong, NRR RidsNrrDorlLpL3-1 Resource RidsOgcRp Resource TBilik, Rill RidsNrrLATHarris Resource RidsAcrsAcnw_MaiICTR Resource ADAMS Accession No. ML083010562 I es Accession No. ML082890872 Srd *Bsy memo d at e d 10117/08 NRR - 106 II OFFICE LPL3-1/PM a-. LPL3-1/LA DCI/CSGB/BC LPL3-1/BC.
I NAME TWengert :/\ ~ THarris ,) .{!l' AHiser* LJames '::/;.... ~t DATE 10/31/08 ( 101 a',108 10/17/08 -W1l( 108 OFFICIAL RECORD COpy II