ML103640046

Summary of Conference Call with Palisades Nuclear Plant Regarding the Fall 2010 Steam Generator Inspections

ML103640046
Person / Time
Site:	Palisades
Issue date:	01/05/2011
From:	Mahesh Chawla Plant Licensing Branch III
To:	Entergy Nuclear Operations
chawla M
References
TAC ME4671
Download: ML103640046 (12)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 January 5, 2011 Vice President, Operations Entergy Nuclear Operations, Inc.

Palisades Nuclear Plant 27780 Blue Star Memorial Highway Covert, MI 49043-9530

SUMMARY

OF CONFERENCE CALL WITH PALISADES NUCLEAR PLANT REGARDING THE FALL 2010 STEAM GENERATOR INSPECTIONS (TAC NO. ME4671)

Dear Sir:

On October 15, 2010, the U.S. Nuclear Regulatory Commission (NRC) staff participated in a conference call with representatives of Entergy Nuclear Operations, Inc. (the licensee) regarding the steam generator (SG) inspection activities at Palisades Nuclear Plant. On September 9, 2010, the licensee was provided with the list of questions (Agencywide Documents Access and Management System (ADAMS) Accession No. ML102560350), to discuss the ongoing results of the SG tube inspections prior to completion of the inspections and repairs conducted during the Palisades Nuclear Plant refueling outage. The information provided by the licensee in support of the teleconference is part of the enclosed conference call summary.

Based on the information provided by the licensee, the NRC staff did not identify any issues that warranted immediate follow up action. However, the staff asked to be notified in the event that any unusual conditions were detected during the remainder of the outage. If you have any questions regarding this matter, I may be reached at 301-415-8371.

Sincerely,

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Mahesh Chawla, Project Manager Plant Licensing Branch 111-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-255

Enclosure:

Conference Call Summary cc: Distribution via ListServ

CONFERENCE CALL

SUMMARY

PALISADES NUCLEAR PLANT FALL 2010 (1R21) OUTAGE STEAM GENERATOR INSPECTIONS On October 15, 2010, the staff of the Steam Generator Tube Integrity and Chemical Engineering Branch of the Division of Component Integrity participated in a conference call with Entergy Nuclear Operations, Inc. (the licensee) regarding the ongoing steam generator (SG) inspection activities at Palisades Nuclear Plant.

Palisades Nuclear Plant has two Combustion Engineering Model 2530 replacement SGs. There are 8,219 mill-annealed Alloy 600 tubes in each SG. The tubes have a nominal outside diameter of 0.75 inches and a nominal wall thickness of 0.042 inches. The tubes are supported at various locations by stainless steel eggcrate lattice type tube supports, diagonal straps and vertical straps. The tubes were expanded through the full depth of the tubesheet using an explosive process.

Additional clarifying information or information not included in the document provided by the licensee is summarized below.

The licensee noted that this was the first outage where they applied the criteria from Appendix I of the Electric Power Research Institute (EPRI) Steam Generator Examination Guidelines. The licensee stated that Appendix I oversized the outside diameter stress corrosion cracking (ODSCC) indications by 15-20 percent. The licensee further noted that the three tubes that were identified for in-situ testing would not have required in-situ testing if the criteria from Appendix H of the EPRI SG Examination Guidelines had been used.

At the time of the call, the licensee was evaluating whether they would perform the in situ testing at three times the normal operating differential pressure (3~P) or at a pressure greater than 3~P, due to sizing uncertainties.

After the call, the licensee informed the Nuclear Regulatory Commission of the results of the in-situ testing. The licensee successfully tested the three tubes to pressures above that required by EPRI guidelines (e.g. 3~P = 4475 pounds per square inch (psi>>.

SG B: Tube 75, 96 to 5650 psi no break or leak.

SG A: Tube 9, 150 to 5650 psi no break or leak; Tube 4,59 to 5650 psi no break or leak The staff did not identify any issues that required follow-up action; however, the staff asked to be notified in the event that any unusual conditions were detected during the remainder of the outage.

-2 STEAM GENERATOR TUBE INSPECTION DISCUSSION DURING PALISADES 2010 (1R21)

OUTAGE

1. Discuss any trends in the amount of primary-to-secondary leakage observed during the recently completed cycle.

Refer to attached Primary to Secondary Leak Rate for Operational Cycle 21 Primary to Secondary Leak Rate graph. Leakage has been minimal all cycle.

2. Discuss whether any secondary side pressure tests were performed during the outage and the associated results.

No secondary side pressure tests were performed in the 2010 refueling outage (1R21).

3. Discuss any exceptions taken to the industry guidelines.

No exceptions were taken to industry guidelines in the 2010 refueling outage (1R21).

4. For each steam generator, provide a description of the inspections performed including the areas examined and the probes used (e.g., dents/dings, sleeves, expansion-transition, U-bends with a 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.

Refer to attached Table 4-2 Palisades REFOUT 21 SG Eddy Current Inspection Scope for a description of inspections performed, expansion criteria, and a description of the probe used for the inspections performed.

5. For each area examined (e.g., tube supports, dent/dings, sleeves, etc), provide a summary of the number of indications identified to-date of each degradation mode (e.g., number of circumferential primary water stress-corrosion cracking indications at the expansion transition). For the most significant indications 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 primary water stress-corrosion cracking at the expansion transition for the first time at this unit).

As of 10/14/2010, (INDICATIONS)

-3 SG Location Tvpe Number Axial A TSH OOSCC 3 Axial A TSH PWSCC 1 Circ A TSH PWSCC 5 Circ A TSH OOSCC 6 A TSH Wear 2 17 Total SG Location Type Number Axial B TSH OOSCC 12 Axial B TSH PWSCC a Circ B TSH PWSCC a Circ B TSH OOSCC a B TSC Wear 2 14 Total SG Location Type Number Axial A Tube Supports OOSCC 30 A Tube Supports Wear 2 32 Total SG Location Type Number Axial B Tube Supports OOSCC 18 B Tube Supports Wear 3 Axial B Freespan OOSCC 1 22 Total Total Indications* 85 Grand Total

• Some tubes have multiple indications Tubesheet and Sludge Pile Most significant axial OOSCC indication is 0.63V from +Pt in 300 kHz channel (69 percent TW using ETSS 128432 method, 55 percent TW using an amplitude regression based on C-E pulled

- 4 tube data). Longest length reported from resolution analysis is 0.80 inch (same indication).

Indication length from profile for this indication is 0.70 inch.

All circumferential ODSCC indications are less than 100 degrees total flaw arc length.

Maximum depth from phase analysis is <50 percent TW.

All PWSCC indications have classified as minor with the largest +Pt amplitude is 1.06V.

Supports Largest P4 (300/100 kHz mix channel) +Pt amplitude is 0.51V. Several indications have total flaw length approaching 2 inches (contact length of eggcrate). Average flaw length is 0.53 inch.

Freespan One tube reported to contain axial ODSCC at a freespan ding. Ding voltage is 2.4 volts, indication was reported by bobbin.

U-Bends One Row 2 tube in SG E-50B is reported to contain axial ODSCC at a ding.

6. Describe repair/plugging plans.

Currently there are 48 potential tubes requiring tube plugging in SG E-50A and 31 potential tubes in SG E-50B.

All stress corrosion cracking (SCC) indications will be plugged. Any circumferential SCC indications near top of tubesheet (TTS) will be stabilized and plugged.

All structure wear greater than or equal to 40 percent TW will be plugged.

7. Describe in-situ pressure test and tube pull plans and results (as applicable and if available).

Based on the available data to date, three tubes will require insitu testing.

SG Tube Number Location Depth Length Voltage SGA R9C150 02H Eggcrate 60% 2.00 0.44 SGA R4C59 01 H Eqqcrate 64% 1.98 0.47 SGB R75C96 Hot Leg Sludge 68% 0.70 0.63 Pile I

8. Discuss the following regarding loose parts:

• What inspections are performed to detect loose parts?

The hot-leg TTS region is inspected with +Pt up to 3 inches above TTS. A similar inspection is performed for the cold-leg TTS region (3 tubes deep along periphery and tube lane. Foreign

-5 object search and retrieval (FOSAR) is performed for the periphery, tube lane annulus, and stay cavity areas.

• A description of any loose parts detected and their location within the SG Loose parts verified with wear in SGA - HL 129-62 and 131-62 and SGB - CL 110-35 and 111 36TSC PLP E-50A 171 PLP Calls in 144 Tube Locations E-50B 105 PLP Calls in 105 Tube Locations

• If the loose parts were removed from the SG FOSAR is scheduled in SG E-50A for 10/18/2010 and in SG E-50B on 10/17/2010.

• Indications of tube damage associated with the loose parts Currently there are 2 locations that have indication of wear associated with a loose part. Loose parts verified with wear in:

SGA - HL 129-62 and 131-62 and SGB - CL 110-35 and 111-36 TSC

9. Discuss the scope and results of any secondary side inspection and maintenance activities (e.g., in-bundle visual inspections, feedring inspections, sludge lancing, assessment deposit loading, etc).

Visual inspection scheduled both SG E-50A and SG E-50B tubesheet periphery regions and in bundle top of hot and cold-leg tubesheets, FOSAR and sludge lancing the top of cold and hot leg tubesheets.

10. Discuss any unexpected or unusual results.

There are three indications that will need to be in-situ tested.

The need for in-situ pressure testing has been entered into the Entergy Corrective Action Program. CR-PLP-201 0-04929 for SG Band CR-PLP-201 0-05055 for SG A.

11. Provide the schedule for steam generator-related activities during the remainder of the current outage.

Currently bobbin and top of tubesheet +Pt RPC are essentially complete in both SGs. Special interest is in progress and will be completed this weekend in both SGs (this includes dingsldents, u-bend, cold leg top of tubesheet, eggcrate etc.).

SG E-50 A and B FOSAR and sludge lancing will also be started early next week.

Tube plugging will start as early as 10/15 and in-situ testing on 10/16.

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-7 Table 4-2. Summary of SG Tube De ~radation Mechanisms and Inspection Requirements: Palisades 1R21 Degradation Location Probe Type Detection Inspection/Expansion Plan Mechanism Inspection Sample Plan Expansion Plan Existing Degradation Mechanisms Tube Wear Non dented Tube Bobbin 100% vertical straight length Rows 1 thru 3, N/A Support Structures 100% full length Rows 4 and higher, both SGs AxialOOSCC Non dented Tube Bobbin 100% vertical straight length Rows 1 thru 3, N/A Support Structures 100% full length Rows 4 and higher, both SGs Plus Point 100% all OSI or %TW signals at eggcrates, 100% historical wear sites between OBH 100% newly reported bobbin signals between and OBC for confirmation of OOSCC at OBH and OBC inclusive historical wear site not previously RPC tested.

AxialOOSCC Freespan, Freespan Bobbin 100% vertical straight length Rows 1 thru 3, N/A dings~5V 100% full length Rows 4 and higher, both SGs Plus Point 100% all bobbin I-codes N/A AxialOOSCC Freespan dings >5V Plus Point 100% dings >5V in both SGs, all elevations N/A and locations AxialOOSCC Dented eggcrates, Plus Point 100% dented eggcrates, diagonal bars, N/A diagonal bars, vertical straps >2V vertical straps >2V Circumferential HL TIS expansion Plus Point 100% from 3" above to 12.5" below expansion See Note (1).

and Axial transition and sludge transition, both SGs OOSCC pile Axial PWSCC HL TIS expansion Plus Point 100% from 3" above to 12.5" below expansion See Note (1) transition and transition, both SGs expandedtubesheet Axial PWSCC Row 1, 2, and 3U Plus Point 100% Row 1, 2, and 3 U-bends using mid 100% of Row 4 for indication in Row 3.

bends range coil (2) Redefine plan if indications detected in Row 4.

-8 Table 4-2. Summary of SG Tube De Jradation Mechanisms and Inspection Requirements: Palisades 1R21 Degradation Location Probe Type Detection Inspection/Expansion Plan Mechanism Inspection Sample Plan Expansion Plan Tube Wear Dented Vertical Bobbin: 100% vertical straight length Rows 1 thru 3, N/A Straps, Diagonal 0.610" 100% full length Rows 4 and higher, both SGs Bars and Eggcrates , diameter (active mechanism dictates plan)

<5V Dented Vertical Plus Point: 100% >2V dents will be performed as part of N/A Straps, Diagonal 0.610"/0.580" ODSCC inspection plan Bars and Eggcrates, diameter

>5V Tube Wear Square bend region Bobbin 100% vertical straight length Rows 1 thru 3, N/A (freespan) 100% full length Rows 4 and higher, both SGs (active mechanism dictates plan)

Plus Point Highest eggcrate through square bend, tubes N/A surrounding R99 C140 in SGB Tube Wear TIS periphery, tube Bobbin 100% full length bobbin +FOSAR in both SGs Plus Point all surrounding tubes with (loose parts) lane loose part or loose part wear sig nals Plus Point 100% hot-leg TTS region plus 3 tube deep on Plus Point all surrounding tubes with cold leg periphery from 2" above to 2" below loose part or loose part wear sig nals TIS, plus special interest testing of PLP signals from bobbin in freespan, at eggcrates, and vertical straps, diagonal bars Resolution for Classification of Indications Potential MBMs All Bobbin 100% vertical straight length Rows 1 thru 3, N/A 100% full length Rows 4 and higher, both SGs Plus Point Flaw confirmation of bobbin indications with Review specific occurrences of flaw change or no history detection and establish expansion plan based on observed parameters

-9 Table 4-2. Summary of SG Tube De Jradation Mechanisms and Inspection Requirements: Palisades 1R21 Degradation Location Probe Type Detection Inspection/Expansion Plan Mechanism Inspection Sample Plan Expansion Plan To Be Defined Bobbin Signals at Plus Point 25% historical DB and VS wear sites 100% DB and VS wear sites in both SGs Suspected Wear for detection of ODSCC Sites not yet characterized Potential Degradation Mechanisms Circ PWSCC Row 1and 2 U- Plus Point 100% Row 1, 2, and 3 U-bends in both SGs 100% of Row 4 for indication in Row 3.

bends in both SGs using mid-range coil (2) Redefine plan if indications detected in Row 4.

Circ PWSCC HL TIS expansion Plus Point 100% from 3" above to 12.5" below expansion See Note (1).

transition and transition, both SGs expandedtubesheet CircODSCC Dented Vertical Plus Point Controlled by inspection requirements for 100% all dings/dents for confirmation of Strap Locations existing or potential mechanisms, PLUS tube eire ODSCC locations listed in Section 4.5, item 5 Pitting Sludge pile Bobbin Controlled by inspection requirements for N/A existing or potential mechanisms Non-Relevant Degradation Mechanisms Included in the 1R21 Eddy Current Inspection Scope Axial PWSCC Dented support Plus Point Controlled by inspection requirements for 100% all dings/dents for confirmation of structures existinq or potential mechanisms axial PWSCC Axial and Circ Cold-leg expanded Plus Point 3 tubes deep on cold-leg periphery from 2" 100% cold-leg from 2" above to 13 inches PWSCC tube in tubesheet above to 2" below TIS (controlled by loose below TIS part detection program)

AxialODSCC Wear sites Bobbin Controlled by inspection requirements for N/A existinq or potential mechanisms Plus Point 25% historical wear sites between DBH and 100% all wear sites between DBH and DBC DBC for confirmation of combined mode axial ODSCC + wear scar

- 10 (1) 20 percent cold-leg TIS Plus Point expansion at either 1R21 or 1R22 from 3" above to 12.5" below bottom of expansion transition in SG with C-3 condition or if failure of performance criteria at TIS is determined.

(2) Any Row 1 or Row 2 U-bend with mid-range +Pt coil noise exceeding the value specified in Appendix B will be tested with a high frequency +Pt coil probe.

ML103640046 *M emo dated Novem ber 10 20 10 f rom I to R Pascare RT ayior I OFFICE NRR/LPL3-1/PM NRR/LPL3-1/LA NRRlCSGB/BC* NRRlLPL3-1/BC NAME MChawla BTuily RTaylor RPascarel1i DATE 1 lOS 111 1 lOS 111 1 lOS 111 1 105/11