ML062560069
| ML062560069 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 09/22/2006 |
| From: | Padovan L NRC/NRR/ADRO/DORL/LPLIII-1 |
| To: | Harden P Nuclear Management Co |
| L. Mark Padovan, LPL3-1 | |
| References | |
| TAC MD1223 | |
| Download: ML062560069 (8) | |
Text
September 22, 2006 Mr. Paul A. Harden Site Vice President Nuclear Management Company, LLC Palisades Nuclear Plant 27780 Blue Star Memorial Highway Covert, MI 49043-9530
SUBJECT:
PALISADES PLANT -
SUMMARY
OF CONFERENCE CALLS REGARDING THE 2006 STEAM GENERATOR TUBE INSPECTIONS (TAC NO. MD1223)
Dear Mr. Harden:
On March 14, April 17, and April 18, 2006, the Nuclear Regulatory Commission (NRC) staff participated in conference calls with Palisades representatives regarding their 2006 steam generator tube inspection activities.
In support of the call on March 14, 2006, the licensee provided the proposed Palisades steam inspection scope for the 2006 refueling outage. The licensee provided additional information concerning the scope of its exams in the tubesheet region by letter dated March 20, 2006. In support of the April 17, 2006, follow-up conference call, the licensee provided information about the scope of the eddy current inspections performed, the status of the proposed inspections, and the number and type of indications identified.
Another call was conducted on April 18, 2006, with Palisades staff to discuss its decision to in-situ pressure-test a tube in SG-A. In support of this call, the licensee provided a description of the indication in question. Subsequently, the licensee informed NRC staff that the tube that was in-situ pressure-tested passed the test with no leakage. Based on the information provided, the staff did not identify any technical issues that warranted follow-up action at the time. Please contact me at (301) 415-1423 if you have questions.
Sincerely,
/RA/
L. Mark Padovan, Project Manager Plant Licensing Branch III-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-255
Enclosure:
As stated cc w/encl: See next page
Mr. Paul A. Harden September 22, 2006 Site Vice President Nuclear Management Company, LLC Palisades Nuclear Plant 27780 Blue Star Memorial Highway Covert, MI 49043-9530
SUBJECT:
PALISADES PLANT -
SUMMARY
OF CONFERENCE CALLS REGARDING THE 2006 STEAM GENERATOR TUBE INSPECTIONS (TAC NO. MD1223)
Dear Mr. Harden:
On March 14, April 17, and April 18, 2006, the Nuclear Regulatory Commission (NRC) staff participated in conference calls with Palisades representatives regarding their 2006 steam generator tube inspection activities.
In support of the call on March 14, 2006, the licensee provided the proposed Palisades steam inspection scope for the 2006 refueling outage. The licensee provided additional information concerning the scope of its exams in the tubesheet region by letter dated March 20, 2006. In support of the April 17, 2006, follow-up conference call, the licensee provided information about the scope of the eddy current inspections performed, the status of the proposed inspections, and the number and type of indications identified Another call was conducted on April 18, 2006, with Palisades staff to discuss its decision to in-situ pressure-test a tube in SG-A. In support of this call the licensee provided a description of the indication in question. Subsequently, the licensee informed NRC staff that the tube that was in-situ pressure-tested passed the test with no leakage. Based on the information provided, the staff did not identify any technical issues that warranted follow-up action at the time. Please contact me at (301) 415-1423 if you have questions.
Sincerely,
/RA/
L. Mark Padovan, Project Manager Plant Licensing Branch III-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-255
Enclosure:
As stated cc w/encl: See next page DISTRIBUTION:
PUBLIC RidsNrrPMMPadovan RidsNrrLATHarris RidsNrrDorlLpl3-1 RidsAcrsAcnwMailCenter CLipa, Rgn-III LPL3-1 R/F MYoder TBloomer RidsDorlDpr RidsOgcRp RidsRgn3MailCenter ADAMS Accession Number: ML062560069 OFFICE NRR/LPL3-1 NRR/LPL3-1/PM NRR/LPL3-1/LA NRR/LPL3-1/BC(A)
NAME DWright LPadovan THarris MMurphy DATE 09/21/06 09/24/06 09/19/06 09/22/06 OFFICIAL RECORD COPY
Palisades Plant cc:
Robert A. Fenech, Senior Vice President Nuclear, Fossil, and Hydro Operations Michigan Department of Attorney General Consumers Energy Company Special Litigation Division 1945 Parnall Rd. 525 West Ottawa St.
Jackson, MI 49201 Sixth Floor, G. Mennen Williams Building Lansing, MI 48913 Arunas T. Udrys, Esquire Consumers Energy Company Michael B. Sellman 1 Energy Plaza President and Chief Executive Officer Jackson, MI 49201 Nuclear Management Company, LLC 700 First Street Regional Administrator, Region III Hudson, MI 54016 U.S. Nuclear Regulatory Commission Suite 210 Jonathan Rogoff, Esquire 2443 Warrenville Road Vice President, Counsel & Secretary Lisle, IL 60532-4351 Nuclear Management Company, LLC 700 First Street Supervisor Hudson, WI 54016 Covert Township P. O. Box 35 Douglas E. Cooper Covert, MI 49043 Senior Vice President - Group Operations Palisades Nuclear Plant Office of the Governor Nuclear Management Company, LLC P. O. Box 30013 27780 Blue Star Memorial Highway Lansing, MI 48909 Covert, MI 49043 U.S. Nuclear Regulatory Commission Stephen T. Wawro, Director Resident Inspector's Office of Nuclear Assets Palisades Plant Consumers Energy Company 27782 Blue Star Memorial Highway Palisades Nuclear Plant Covert, MI 49043 27780 Blue Star Memorial Highway Covert, MI 49043 Michigan Department of Environmental Quality Waste and Hazardous Materials Division Laurie A. Lahti, Manager Hazardous Waste and Radiological Regulatory Affairs Protection Section Nuclear Management Company, LLC Nuclear Facilities Unit Palisades Nuclear Plant Constitution Hall, Lower-Level North 27780 Blue Star Memorial Highway 525 West Allegan Street Covert, MI 49043 P.O. Box 30241 Lansing, MI 48909-7741
CONFERENCE CALL
SUMMARY
2006 STEAM GENERATOR TUBE INSPECTIONS PALISADES DOCKET NO. 50-285 On March 14, April 17, and April 18, 2006, the Nuclear Regulatory Commission (NRC) staff participated in conference calls with Palisades representatives regarding their 2006 steam generator (SG) tube inspection activities. A summary of the information provided during the calls is provided below.
Palisades has two Combustion Engineering Model 2530 replacement SGs. There are 8,219 mill annealed Alloy 600 tubes in each SG. The tubes have an outside diameter of 3/4-inch and a wall thickness of 0.042-inch. The tubes are supported at various locations by stainless steel eggcrate lattice type tube supports, diagonal straps and vertical straps. The SG tubes were expanded through the full depth of the tubesheet using an explosive process.
In support of the March 14, 2006, conference call, the licensee provided the following information regarding the planned scope of their 2006 SG tube inspections:
Proposed Palisades Steam Inspection Scope 2006 Refueling Outage 100 percent full length bobbin coil exam (except Row 1 and 2 U-bends) 100 percent +Point' exam with extent from 3 inches above TTS [top of tubesheet] to 11.6 inches below TTS in both SGs in accordance with WCAP-1608-P [16208-P].
100 percent Rows 1, 2, and 3 small radius U-bend +Pt [+Point'] exam in both SGs using mid-range coil 100 percent +Point' exam of freespan dings >5V between tubesheet hot (TSH) and tubesheet cold (TSC) in both SGs 100 percent +Point' exam of dents >5V at structures between TSH and TSC in both SGs 100 percent +Point' exam of #5V dents at eggcrates in both SGs 25 percent +Point' exam of historic %TW [through wall] calls at diagonal bars and vertical straps in both SGs Special Interest +Point' exam including Confirmation of bobbin I-code signals including all DSI [distorted support indication] signals at eggcrates
+Point' exam testing of wear scars reported as >40 percent TW by bobbin ENCLOSURE
+Point' exam testing of newly reported signals at structures (vertical straps, diagonal bars, and eggcrates) to confirm degradation mechanism mode
+Point' examination through the square bend region of tubes surrounding R99 C140 in SG-B
+Point' exam boxing of confirmed foreign object wear signals at all elevations
+Point' exam of the outer three peripheral tubes at the cold-leg TTS for detection of possible loose parts or wear signals The licensee provided additional information concerning the scope of their exams in the tubesheet region by letter dated March 20, 2006 (ADAMS Accession No. ML060800610).
In support of the April 17, 2006, conference call, the licensee provided information about the scope of the eddy current inspections performed, the status of the inspections, and the number and type of indications identified. This information is attached to this summary. Additional clarifying information and information not included in the document provided is summarized below:
In SG-A, there were 5 wear indications in which the depth of degradation was greater than 40 percent through wall. The maximum depth of these indications was determined to be 43 percent through wall. The maximum growth of these wear indications from the previous inspection was 6 percent. The growth rates for the wear indications were consistent with those from the previous inspection.
In SG-A, one tube was restricted by a foreign object located within the tube.
During initial tests, the restriction was at the fifth hot-leg tube support, however, during a retest, the restriction was near the top of the tubesheet on the hot-leg side of the SG.
The foreign object was identified inside the tube (primary side), and was determined to be approximately 5/8 inches long and metallic. The origin of the object is unknown.
The tube was inspected both above and below the loose part (with a bobbin from the cold-leg tube end to the first hot-leg tube support and with a rotating probe from the hot-leg tube end to near the top of the tubesheet on the hot-leg side of the SG).
No indications were identified in this tube. No damage was observed at the ends of any other tubes (i.e., at the primary face of the tubesheet). The licensee stated that the part was firmly wedged inside the tube and attempts to dislodge it were unsuccessful.
Because the part was firmly wedged in place, and because relative vibration between the tube and the object is expected to be minimal based on its proximity to the tubesheet, the foreign object was left in place. The tube was removed from service by plugging.
The longest axial outer diameter stress corrosion cracking (ODSCC) identified in either SG was 0.27 inches. The maximum eddy current voltage of any axial ODSCC in either SG was approximately 0.3 volts.
The maximum extent of any circumferential ODSCC in either SG was 105 degrees.
The maximum eddy current voltage of any circumferential ODSCC in either SG was 0.52 volts.
In SG-A, one axial ODSCC indication was identified in a 10.5 volt ding. This indication was 0.2 inches in length with a maximum eddy current voltage of 0.74 volts. The licensee indicated that the voltage amplitude of the flaw may have been skewed by the residual influence of the ding. For this reason, the licensee believes the actual crack would have a voltage amplitude less than 0.74 volts.
The maximum length of any freespan ODSCC in either SG was 0.36 inches.
The maximum eddy current voltage of any freespan ODSCC in either SG was approximately 0.2 volts.
The maximum length of any ODSCC at an eggcrate support in either SG was 0.81 inches. The maximum eddy current voltage of any ODSCC at an eggcrate support in either SG was approximately 0.42 volts.
The maximum length of any axial primary water stress corrosion cracking in either SG was 0.31 inches. The maximum eddy current voltage of any axial primary water stress corrosion cracking in either SG was approximately 0.72 volts.
Tube integrity was not challenged by any of the flaws identified.
All dents and dings with voltage amplitude greater than 5 volts were inspected, including dents and dings located at eggcrate supports.
In SG-B, the inspection of the U-bend portion of one row 3 tube resulted in preventive plugging of the tube. An indication measuring approximately 0.1 inches was identified.
The licensee attributed the indication to lift off of the probe. Multiple inspections were performed at different speeds with the same result. Because the licensee was not able to rule out a flaw, the tube was plugged. This location had not been inspected with a rotating probe previously. As a result of this finding, the U-bend regions of all row 4 tubes were inspected with a rotating probe. The licensee believes that the cause of the indication was a burr on the inner diameter of the tube created during the manufacturing process. The licensee indicated that a similar indication was observed in a SG tube being manufactured for a replacement SG. Destructive examination of that tube showed the presence of a burr. The flaw that was identified during manufacturing exhibited similar behavior to the one seen at Palisades during this outage.
In SG-A, the licensee believes that the possible loose part (PLP) signal was caused by a conductive deposit since the tube is located in the middle of the tube bundle in a region where sludge is known to accumulate.
In SG-B, a volumetric indication associated with a PLP measured 0.22 inches with an amplitude of 0.29 volts. The PLP was evident on a total of three tubes. Only one of the tubes had a volumetric wear indication. A review of the data from past eddy current inspections shows that the PLP signal was present during the last two inspections and it has exhibited some minor changes since the last inspection. All three tubes affected by the PLP will be plugged and stabilized. The ability to visually inspect the region is limited due to the triangular pitch of the SG tubes; however, a metallic part could be seen at this location.
Based on off-gas measurements the primary to secondary leakage for the past operating cycle was approximately 1E-5 gallons per minute ( 0.014 gallons per day).
No secondary side pressure tests were performed.
No exceptions were taken to the industry guidelines for eddy current inspection of SG tubes.
All crack-like indications will be plugged. All circumferential cracks and all volumetric indications with PLPs will be plugged and stabilized.
At the time of this call no in-situ pressure tests or tube pulls were planned.
On April 18, 2006, another call was conducted with Palisades staff to discuss their decision to in-situ pressure test a tube in SG-A. In support of this call, the licensee provided a description of the indication in question. A summary of this information is provided below:
Bobbin testing identified a direction-setting issue (DSI) at the first eggcrate support on the hot-leg side. The bobbin voltage amplitude on the mixed channel was 0.15 volts.
+Point' inspection of the DSI indication identified a single axial indication.
The indication was determined to be 0.81 inches long with a voltage amplitude of 0.42 volts.
The flaw profile for this indication is atypical since it has a relatively uniform depth for the entire length of the flaw (most crack like indications at this location have shallow depths at the end of the cracks with a short length corresponding to the deepest part of the crack).
The rotating probe signal exhibited somewhat of a ding like response; however, no ding was present in the bobbin data.
A Monte Carlo simulation was performed including burst relation error and material property distribution for Palisades. Based on the as reported amplitude based depth estimates, the predicted burst pressure at 95 percent probability for the flaw was 4600 pounds per square inch (psi). When depth sizing uncertainties were accounted for the simulation resulted in a burst pressure of 3400 psi at 95% probability.
Based on the results of the +Point' inspection, the licensee decided to perform in-situ pressure testing of the indication.
Subsequent to the call on April 18, 2006, the licensee informed NRC staff that the tube that was in-situ pressure tested passed the test with no leakage. Based on the information provided, the staff did not identify any technical issues that warranted follow-up action at this time.
PALISADES NUCLEAR PLANT STEAM GENERATOR STATUS REPORT Steam Generator E-50A April 17, 2006 Scope Description Eddy Current Analyzed Potential Indications Requiring Tube And Complete Plugging 5 wear indications > 40%
1 axial ODSCC at eggcrates 100% bobbin full length 99.9% complete 2 axial ODSCC freespan scope 1 restricted at hot leg top of tubesheet 4 axial ODSCC in sludge pile 5 circumferential ODSCC hot-leg 100% +PointTM top of transition zone tubesheet hot-leg +3/-13.5 100% complete 2 axial PWSCC in hot-leg transition inches zone & tubesheet 1 volumetric with PLP 8% +PointTM top of tubesheet cold-leg +2/-2 100% complete None inches 100% +PointTM rows 1-3 100% complete None u-bend 100% +PointTM freespan
& square bend dings > 5 99.9% complete 1 axial ODSCC in 10.5 volt ding volts 100% +PointTM of >2V and <5V dents at 99.9% complete None eggcrates 25% +PointTM of historic
%TW calls at diagonal bars 99.9% complete None and vertical straps Attachment
100% +PointTM of newly reported signals at 100% complete None structures 100% visual inspection of In progress all tube plug hot and cold None Just finished tubes under legs ROSA base plate Upper bundle flush, sludge Scheduled after SG lancing & FOSAR No data E-50B which is in progress In Steam Generator E-50A eddy current data acquisition is 99.9% complete and analysis is 99.9% complete. A total of 22 tubes require potential tube plugging.
PALISADES NUCLEAR PLANT STEAM GENERATOR STATUS REPORT Steam Generator E-50B April 17, 2006 Scope Description Eddy Current Analyzed Potential Indications Requiring Tube And Complete Plugging 100% bobbin full length 100% complete 1 wear indications > 40%
scope 100% +PointTM top of tubesheet hot leg +3/-13.5 100% complete 3 axial ODSCC in sludge pile inches 1 volumetric with PLP 8% +PointTM top of tubesheet cold-leg +2/-2 100% complete None inches 100% +PointTM rows 1-4 u-100% complete 1 preventative bend 100% +PointTM freespan &
100% complete None square bend dings > 5 volts 100% +PointTM of >2V and 99.9% complete None
<5V dents at eggcrates 25% +PointTM of historic
%TW calls at diagonal bars 99.9% complete None and vertical straps 100% +PointTM of newly reported signals at 100% complete None structures 100% visual inspection of all In progress None tube plug hot and cold legs Just finished tubes under ROSA base plate In progress Upper bundle flush, sludge FOSAR in progress Moving sludge lance lancing & FOSAR No data on sludge weight equipment to SG E-50A
In Steam Generator E-50B eddy current data acquisition is 99.9% compete and analysis is at 99.9% complete. A total of 6 tubes require potential tube plugging.