PNP 2011-063, Response to Request for Additional Information - Steam Generator Tube Inspection Report

Response to Request for Additional Information - Steam Generator Tube Inspection Report

ML112700011
Person / Time
Site:	Palisades
Issue date:	09/26/2011
From:	Gustafson O Entergy Nuclear Operations
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
PNP 2011-063
Download: ML112700011 (10)

Text

Entergy Nuclear Operations, Inc.

~..Lt 27780 Covert, Blue Star Memorial Highway Ml 49043 Tel 269 764 2000 Otto W Gustafson Licensing Manager PNP 2011-063 September 26, 2011 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

SUBJECT:

Response to Request for Additional Information Steam Generator Tube Inspection Report Palisades Nuclear Plant Docket 50-255 License No. DPR-20

References:

1. Entergy Nuclear Operations, Inc. letter to NRC dated April 25, 2011, 2010 Steam Generator Tube Inspection Report (ADAMS Accession Number ML11119AO4O)

2. NRC e-mail dated August 1, 2011, Palisades Nuclear Plant SG Tube ISI Report RAIs ME6102 (ADAMS No. ML112170066)

Dear Sir or Madam:

Entergy Nuclear Operations, Inc. (ENO) submitted Reference 1 to the Nuclear Regulatory Commission (NRC) providing the results from steam generator tube inspections conducted during the 2010 refueling outage. ENO received an electronic request for additional information (RAI) from the NRC in Reference 2. ENO and the NRC held a conference call, on August 25, 2011, to clarify the RAI.

Attached is the ENO response to the RAI.

This letter contains no new or revised commitments.

Sincerely, owg/j 1k

(~ 11

Attachment:

1. RAI Response on 2010 Steam Generator Tube Inspection Report cc: Administrator, Region III, USNRC Project Manager, Palisades, USN RC Resident Inspector, Palisades, USNRC

AUACHMENT 1 RAI RESPONSE ON 2010 STEAM GENERATOR TUBE INSPECTION REPORT Request for additional information received by electronic mail August 1, 2011 Nuclear Regulatory Commission (NRC) Request

1. Please clarify the following sentence on page 3: No leakage was predicted for either operating or accident conditions for the 2009 to 2010 operating cycle due to obseived SG [steam generator] tube degradation in the 2010 refueling outage.

Entergy Nuclear Operations, Inc (ENO) Response

1. This sentence should be deleted. A revised page 3 is enclosed. The Palisades Technical Specifications Section 5.5.8b.1. steam generator tube structural integrity performance criterion was satisfied. Technical Specifications Section 5.5.8b.2. steam generator tube integrity accident induced leakage performance criterion was also satisfied. Steam generator leakage did not exceed the 0.3 gallon per minute (gpm) limit. Primary-to-secondary leak rate measured, using condenser off-gas (Xenon-i 33 or Xenon-i 35), was <0.001 gpm for the 2009 to 2010 operating cycle (cycle 21), with a slightly decreasing trend over the cycle.

NRC Request

2. Please confirm the Inspection Period EFPM [Effective Full Power Months] for refueling outage 21 in Table A. It would appear that the correct value is 56.0 EFPM rather than 64.2 EFPM.

ENO Response

2. The correct value is 56.0 EFPM. A revised Table A is enclosed.

NRC Request

3. It appears that two freespan crack-like indications were detected during the 2010 outage (SG A, row 2 column [1121 and SG B row 85, column 44). These indications were presumably associated with dings. Please discuss the size (voltage amplitude) of the dings associated with these indications, If the voltage amplitude of the dings is near 5.0 volts, please discuss the basis for not expanding the rotating probe examinations to include dings whose voltage amplitude is less than or equal to 5.0 volts.

Page 1 of 4

ENO Response

3. In SG A, row2 column 121:

The bobbin coil inspection was not performed, due to the small radius of the tube. As a result, there is not a voltage associated with the indication. An axial stress corrosion crack (SCC) indication was detected in the U-bend region.

Originally, due to the ovality of the tubing, it was dispositioned as having a ding.

Upon further review, a ding-like signal response is not detectable with the +Pt examination. Due to the eddy current characterization of the large horizontal component in the small radius U-bend, a ding could not be identified. Scope expansion included all row three U-bend tubes, which were tested with the +Pt, and no further indications were reported. Therefore, the characterization of this indication is an axial crack in the small radius U-bend.

In SG B, row 85 column 44:

One free span ding crack was reported. This tube contained numerous dings greater than 5.0 volts in the 06H to 07H span. An axial outside diameter stress corrosion crack (ODSCC) indication was reported at an elevation coincident with a 3.14 volt ding. Review of the bobbin data indicates that a reportable bobbin signal (0.82 volt, 152 degrees phase angle) which meets the Palisades guidelines flowchart and the EPRI examination technique specification sheet, ETSS No. 24013.1, was present at this location but not reported. A review of the less than 5.0 volt dings was performed to ensure no other indications meeting the guidelines were present. No additional indications were detected in this review.

The bobbin voltage amplitude of the ding was not near the 5.0 volt limit for detection, therefore no further ÷Pt inspection was required.

NRC Request

4. Please discuss the nature of the single volumetric indications listed in Table 4A.

Are these wear indications attributed to loose parts?

ENO Response

4. As described below, two tubes in each steam generator had single volumetric indications (SVI), which are attributed to loose parts. These four tubes were stabilized and plugged. A third tube in SG B was preventatively plugged because it is next to a loose part.

Two tubes in SG A, row 129 column 62, and row 131 column 62, had wear associated with a possible loose part (PLP) reported approximately two inches above the hot leg top of tube sheet. Since the loose part could not be removed, the two tubes were reported as SVI, stabilized, and plugged.

Page 2 of 4

Two tubes, in SG B, row 110 column 35, and row 111 column 36, had wear associated with a PLP reported approximately 1.5 inches above the cold leg top of tubesheet. Since the loose part could not be removed, the two tubes were reported as SVI, stabilized, and plugged.

A third tube in SG B, row 109 column 36, identified in Table 6 as SVI had no volumetric indication, but was identified as next to a loose part, and was preventatively stabilized and plugged.

NRC Request

5. In Table 4A, there are some depths that are greater than 100-percent through-wall. Please clarify.

ENO Response

5. The column in Table 4A labeled +Pt Depth Voltage was labeled incorrectly and does not indicate percent through-wall. The values in this column represent the circumferential extent around the tube (in degrees) and are only valid for the circumferential indications reported. The column titled Length Axial (Ax) inch represents the length of the axial indications (in inches) and are not relevant to the circumferential indications. The Westinghouse ANSER software automatically includes both the circumferential and axial measurements regardless of the flaw orientation. Only the number relevant to the particular indication is used to assist in the tube integrity evaluation by engineering. Both columns, +Pt Depth Voltage, and Length Axial (Ax), should not have been included in the report and have been removed in the revised Table 4A that is enclosed. There are no greater than 100% through wall indications in the Palisades steam generator inspection database.

NRC Request

6. Please discuss whether any secondaiy side inspections other than foreign object search and retrieval were performed. If secondary side inspections were performed, please summarize the results.

ENO Response

6. There were no secondary side inspections completed in the 2010 refueling outage other than the foreign object search and retrieval.

Page 3 of 4

NRC Request

7. In Table 3, there is reference to wear from tube-to-tube contact. This wear appears to be ilmited to the square bend region. Was any such wear obseived during this inspection? If so, please discuss the extent of the degradation (number and size).

ENO Response

7. Table 3 is the technique table for the various damage mechanisms. Tube-to tube wear was not observed in the 2010 refueling outage.

The tube-to-tube wear discussed in Table 3 was observed in the 2007 refueling outage. A tube in SG A, row 136 column 77, was identified with apparent tube to tube wear. The adjacent tube was already plugged for a wear indication.

Therefore, the tube, in row 136 column 77, was preventatively stabilized and plugged.

Page 4 of 4

ENCLOSURE ERRATA Information Replacement Information for the Steam Generator Inepeotlon Report for the Refueling Outage Report Page 3, Report Table A, and Report Table 4A Changes to the Information submItted In the 2010 Steam Generator Tube Inspection ReportsubmlttedonAprll25,2011,arelndlcatedbyvertlcal Unesinthe rlghthand column.

Inspection Summary Palisades Technical Specification (TS) 5.6.8, Steam Generator Tube Inspection Reports, requires Entergy Nuclear Operations, Inc. (ENO), to submit a report to the NRC within 180 days after initial entry into mode 4 following a steam generator inspection performed in accordance with Specification 5.5.8, Steam Generator (SG)

Program. The report shall include:

a. The scope of inspections performed on each SG (Table 1),

b. Active degradation mechanisms found (Table 2),

c. Nondestructive examination techniques utilized for each degradation mechanism (Table 3),

d. Location, orientation (if linear), and measured sizes (if available) of service induced indications (Tables 4A, 4B and 4C),

e. Number of tubes plugged during the inspection outage for each active degradation mechanism (Table 5),

f. Total number and percentage of tubes plugged to date (Table 5),

g. The results of condition monitoring, including the results of tube pulls and in-situ testing, (Table 6), and

h. The effective tube plugging percentage for all plugging in each SG (Table 5).

ENO performed an inspection of its two Combustion Engineerin~ (CE) SGs in October 2010 during refueling outage 1 R21. This inspection was the l3~ in-service inspection (ISI) following SG installation in 1990 and the 4th of four scheduled inspections in the third sequential inspection period. The unit initially entered mode 4 following this inspection on October 27, 2010.

The TS section 5.5.8b.i. steam generator tube integrity structural integrity performance criterion was satisfied. The TS section 5.5.8b.2. steam generator tube integrity accident induced leakage performance criterion was satisfied. Leakage did not exceed the 0.3 gallon per minute (gpm) accident induced leakage limit. Primary-to-secondary leak rate measured using condenser off-gas (Xenon-i 33 or Xenon-i 35) was <0.001 gpm for operating cycle 21 with a slightly decreasing trend over the cycle.

All plugs installed in the Palisades SGs post-operation are Westinghouse ribbed mechanical plugs, which are leak-tight for all plant conditions. The Palisades SGs also contain 308 tubes plugged pre-service in SG E-50A, and 309 tubes plugged pre-service in SG E-50B. Of the tubes plugged pre-service, one tube in SG E-50A and four tubes in SG E-50B are plugged using welded plugs, which are leak tight. The remaining tubes plugged pre-service are plugged using CE roll plugs, which are also designed to be leak tight for all plant conditions.

Table A Refueling Outage (RFO) Information since Steam Generator Replacement RFO Year Cycle Cycle Replacement Inspection Sequential Notes No. EFPD EFPM SG Period Inspection Cumulative EFPM Period EFPM 8 1990/ NA NA 0.0 NA NA SG 1991 Replacement 9 1992 298.5 9.8 9.8 0.0 NA jst ISI both SG 10 1993 356.8 11.7 21.5 11.7 First ISI both SG 11 1995 430.5 14.1 35.6 25.9 First ISI both SG 12 1996 407.4 13.4 49.0 39.3 First ISI both SG 13 1998 419.6 13.8 62.8 53.0 First ISI both SG 14 1999 449.3 14.8 77.6 7.8 Second ISI both SG 15 2001 401.3 13.2 90.8 21.0 Second ISI both SG 16 2003 444.3 14.6 105.4 35.6 Second ISI both SG 17 2004 493.1 16.2 121.6 51.8 Second ISI both SG 18 2006 487.9 16.0 137.6 7.8 Third ISI both SG 19 2007 459.3 15.1 152.7 22.9 Third ISI both SG 20 2009 499.8 16.4 169.1 39.3 Third ISI both SG 21 2010 507.7 16.7 185.8 56.0 Third ISI both SG EFPD = effective full power days EFPM = effective full power months

Table 4A Location and Measured Sizes of Service Induced Indications

+Pt Elevation SG Row Column Volts IND Location A 2 121 0.29 SAl 05H 9.06 A 2 151 0.19 SAl 02H 0.02 A 4 59 0.54 SAl O1H 0.41 A 4 111 0.19 SAl O1H 0.45 A 5 106 0.36 SAl O1H 0.12 A 7 114 0.16 SAl O1H -0.57 A 7 114 0.24 SAl 01H 0.41 A 7 114 0.32 SAl 02H 0.78 A 9 150 0.44 SAl 02H -0.23 A 10 55 0.25 SAl O1H -0.69 A 10 61 0.16 SAl O1H -0.74 A 10 107 0.08 SAl 03H 0.83 A 11 48 0.26 SAl O1H -0.23 A 11 130 0.2 SAl 02H 0.18 A 12 119 0.3 SAl O1H 0.59 A 12 125 0.3 SAl O1H 0.74 A 13 44 0.7 SCI TSH -5.87 A 13 44 0.68 SCI TSH -5.1 A 14 109 0.3 SAl O1H -0.31 A 16 141 0.2 SCI TSH -0.05 A 17 108 0.34 SAl O1H 0.81 A 24 113 0.59 SCI TSH -1.6 A 27 50 0.48 SAl TSH 0.49 A 29 54 0.37 SCI TSH 0 A 29 110 0.19 SAl O1H 0.31 A 32 111 0.22 SAl O1H 0.42 A 36 33 1.06 Sd SH -8.34 A 39 116 0.23 SAl TSH 0.69 A 47 100 0.74 SCI TSH -12.99 A 47 110 0.35 SAl O1H 0.26 A 48 47 2.37 PCT VS4 0.81 A 70 39 0.24 SAl O1H 0.53 A 70 77 0.51 SCI TSH 0.07 A 71 70 0.22 SAl O1H 0.52 A 71 94 0.51 SAl SH 0.36 A 73 82 0.2 SCI TSH -0.01 A 74 77 0.48 SCI TSH -0.06 A 77 100 0.51 SAl TSH 0.38 A 78 93 0.2 SAl TSH 0.55 A 84 91 0.42 SCI TSH 0 A 98 103 0.5 SCI TSH -0.22 A 102 119 2.7 PCT 04H 1.04 A 105 50 0.13 SAl O1H -0.16 A 107 56 0.22 SAl 02H 0.88 A 107 82 0.34 SAl O1H 0.11 A 107 90 0.43 SAl 03H 0.81 A 107 132 0.26 SAl 02H 0.66 A 110 99 0.09 SAl O1H 0.94 A 113 86 0.27 SAl 01 H -0.7 A 117 100 0.19 SAl O1H 0.78 A 129 62 0.32 SVI TSH 2.41

Table 4A Location and Measured Sizes of Service Induced Indications

+Pt Elevation SG Row Column Volts IND Location A 130 111 0.23 SAl 02H 0.14 A 131 62 0.4 SVI TSH 1.99 A 134 85 0.25 SAl 01H 0.67 A 136 73 0.25 SAl 01H -0.83 B 1 106 0.35 SAl 02H 0.97 B 21 116 0.25 SAl O1H 0.35 B 21 116 0.29 SAl O1H 0.63 B 21 138 0.44 SAl O1H 0.55 B 23 16 0.2 SAl O1H 0.44 B 23 52 0.28 SAl O1H 0.27 B 23 60 0.16 SAl VS4 -1 B 24 45 0.44 SAl TSH 0.36 B 24 49 0.34 SAl TSH 0.9 B 24 129 0.45 SAl O1H 0.41 B 27 50 0.37 SAl TSH 0.85 B 28 47 0.42 SAl TSH 0.57 B 28 119 0.19 SAl O1H -0.23 B 30 107 0.21 SAl O1H -0.78 B 30 107 0.38 SAl O1H 1.03 B 30 107 0.43 SAl 02H -0.27 B 30 107 0.47 SAl 02H 0.49 B 31 114 0.25 SAl O1H -0.84 B 34 105 0.15 SAl O1H -0.13 B 38 117 0.26 SAl TSH 0.41 B 39 132 2.56 PCT VS4 1.17 B 56 67 0.34 SAl O1H -0.92 B 56 109 0.33 SAl TSH 0.4 B 72 29 0.32 SAl 03H -0.73 B 73 98 0.2 SAl TSH 0.58 B 73 98 0.25 SAl SH 0.82 B 73 102 0.41 SAl TSH 0.44 B 74 97 0.17 SAl TSH 0.77 B 75 96 0.63 SAl TSH 0.97 B 78 93 0.38 SAl TSH 0.8 B 85 44 0.43 SAl 06H 18.82 B 110 35 0.47 SVI TSC 1.42 B 111 36 0.3 SVI TSC 1.32 B 126 87 3.36 PCT VS4 -0.77 B 130 77 0.71 SAl 08H 0.7 B 133 106 2.76 PCT VS6 -0.03