NRC 2008-0045, Spring 2008 Unit 2 (U2R29), Steam Generator Tube Inspection Report
| ML082590073 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 09/16/2008 |
| From: | Meyer L Florida Power & Light Energy Point Beach |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NRC 2008-0045 | |
| Download: ML082590073 (6) | |
Text
September 16,2008 FPL Energy Point Beach, LLC, 6610 Nuclear Road, Two Rivers, WI 54241
- FPL Energy Point Beach Nuclear Plant NRC 2008-0045 TS 5.6.8 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington DC 20555 Point Beach Nuclear Plant, Unit 2 Docket No. 50-301 Renewed License No. DPR-27 Spring 2008 Unit 2 (U2R29)
Steam Generator Tube lnspection Report Pursuant to the requirements of Point Beach Nuclear Plant (PBNP)
Technical Specification (TS) 5.6.8, "Steam Generator Tube lnspection Report,"
FPL Energy Point Beach, LLC, is submitting the 180-day Steam Generator Tube lnspection report. The enclosure to this letter provides the results of the spring 2008, Unit 2 (U2R29) steam generator (SG) tube in-service inspections.
This letter contains no new commitments.
Very truly yours, FPL Energy Point Beach, LLC
- -77 Larry Meyer Site Vice President Enclosure cc:
Administrator, Region Ill, USNRC Project Manager, Point Beach Nuclear Plant, USNRC Resident Inspector, Point Beach Nuclear Plant, USNRC PSCW
ENCLOSURE I FPL ENERGY POINT BEACH, LLC POINT BEACH NUCLEAR PLANT, UNlT 2 SPRING 2008 UNlT 2 (U2R29)
STEAM GENERATOR TUBE INSPECTION REPORT The Point Beach Nuclear Plant (PBNP) steam generator (SG) tube inspection program for the spring 2008, Unit 2 refueling outage 29 (U2R29) was conducted in accordance with the requirements of PBNP Technical Specification (TS) 5.5.8. PBNP Unit 2 entered MODE 4 on May 05, 2008, following this in-service inspection. PBNP determined that U2R29 is within the first sequential in-service inspection period of 144 effective full power months (EFPM) following the first inservice inspection. lnspections conducted during U2R29 meet the TS requirements for the second half of the period and marks the final inspection of the 144 EFPM period.
PBNP Unit 2 SGs are Westinghouse Model Delta-47 replacement SGs with 3499, 0.875-inch outer diameter, 0.050-inch wall, lnconel Alloy 690 thermally-treated tubes. The tubes are on a 1.0687-inch triangular pitch and were hydraulically expanded the full depth of the tubesheet.
The tubes are supported by seven (7) stainless steel tube support plates with trifoil holes and three (3) sets of stainless steel anti-vibration bar (AVB) assemblies. A stainless steel flow distribution baffle with nonafoil shaped tube holes is located between the top of tubesheet and first support plate (lowest). The original PBNP Unit 2 SGs were replaced during refueling outage 22, and the replacement SGs were operating by 1997. The replacement SGs have accumulated approximately 9.03 effective full power years of operation.
The U2R29 SG tube inspections were conducted on both 'A' and 'B' SGs and consisted of the following:
- a. Scope of Inspections Tube end to tube end bobbin coil inspections were performed on 100% of the accessible (not plugged) tubes in PBNP Unit 2 SG 'A' and SG 'B' during U2R29. Rotating probe techniques (i.e., +pointTM) were used to further disposition certain indications reported with the bobbin coil, and to inspect locations where the bobbin coil is not qualified for use. The purpose of the inspection was to identify existing or potential forms of SG degradation as detailed in Section (c). The summary for each SG is as follows Bobbin coil inspections:
o Full length tube end to tube end - 3499 tubes (100%)
+pointTM rotating coil inspections:
o Hot leg top of tubesheet +I-3 inches - 100% of peripheral tubes o Hot leg top of tubesheet +I-3 inches - 20% of center area tubes o Cold leg top of tubesheet +I-3 inches - 100% of peripheral tubes o Row 1 and 2 U-bends - - 20% tubes Page 1 of 5
Bobbin coil inspections:
o Full length tube end to tube end - 3495 tubes (1 00%)
+pointTM rotating coil inspections:
o Hot leg top of tubesheet +/- 3 inches - 100% of peripheral tubes o Hot leg top of tubesheet +I-3 inches - 20% of center area tubes o Cold leg top of tubesheet +/- 3 inches - 100% of peripheral tubes o Row 1 and 2 U-bends - -20% tubes
- b. Active Degradation Mechanisms Found During the U2R29 SG eddy current test (ECT) inspection, no crack-like indications were reported and no tubes required plugging. No active degradation mechanisms were found.
Wear degradation described in Tables 1 and 2 under Section (d) is not active based on industry guidance.
- c. Nondestructive Examination Techniques Utilized for Each Degradation Mechanism Existing Degradation Examination Technique
% Sample (SG 'A' and 'B')
Mechanism AVB Wear Bobbin 100%
Tube Support Plate Wear Bobbin Potential Degradation Examination Technique
% Sample (SG 'A' and 'B')
Mechanism 100% bobbin; 100% periphery Mechanical/Loose Part
(+pointTM) tube sheet hot leg and Wear Bobbin; +pointTM; visual Cold leg; complimented with visual inspection Supplemental Inspection Examination Technique
% Sample (SG 'A' and 'B')
and Evaluation ODSCC U-bend PWSCC U-bends 20% Row 1 /Row 2 20% Row 1 /Row 2 Page 2 of 5
Inspection Examination Technique and Evaluation
% Sample (SG 'A' and 'B')
ODSCC Tubesheet Transition Zone PWSCC Tubesheet Transition Zone
+pointTM 20% H/L TTS (+/- 3")
+pointTM 20% H/L TTS (+/- 3")
Diagnostic and Special Interest Inspection and Examination Technique
% Sample (SG 'A' and 'B')
Evaluation Cold Leg Sludge 100% bobbin; Pile Pitting and Freespan Bobbin; +pointTM
+pointTM all detected from Volumetric bobbin ODSCC at Tube support plates Ding (Freespan)
DingIDent (U-bend and supports)
Bobbin; +pointTM Bobbin; +pointTM Bobbin; +pointTM ODSCC Outside diameter stress corrosion cracking PWSCC Primary water stress corrosion cracking HIL hot-leg CIL cold-leg TSP tube support plate 100% bobbin;
+pointTM all detected from bobbin 100% Bobbin 100% +pointTM ( >5V freespan) 100% Bobbin 100% +pointTM (all at AVBs, TSPs & U-bends)
Transition zone refers to the area near the top of tubesheet (TTS) inspected over a range of at least +3" to -3".
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- d. Location, Orientation (If Linear), and Measured Sizes (If Available) of Service Induced Indications AVB Wear AVB wear had not previously been reported in the Unit 2 replacement SGs prior to U2R29.
During U2R29 there were seven (7) indications, in five (5) tubes, in SG 'A' with indications of wear at the AVBs. Table 1 summarizes the AVB wear indications. All seven (7) AVB wear indications were sized with the bobbin coil and confirmed as wear by the rotating +pointTM coil. Depth profiles obtained by +PointTM revealed that the indications at Row 84, Column 45 (AVB 5); and Row 78, Column 59 (AVB 4), were two-sided. Therefore, the bobbin depth indicated represents the sum of the wear on both sides of the tube. None of these indications were required to be repaired per engineering disposition and all remain in service.
There were no tubes in SG 'B' with indications of wear at the AVBs.
Table 1 - Anti-Vibration Bar Wear, % Through-Wall, SG 'A' Tube Wear at Broached Tube Support Wear at tube supports had not been reported in the Unit 2 replacement SGs prior to U2R29.
During the U2R29 inspection, tube wear was detected by bobbin probe at one location in SG 'A' on the hot leg side of the sixth support plate (06H). As shown on Table 2, the +pointTM inspection determined that there were actually two indications present at the 06H location (at two separate broached land contacts). These indications were measured individually at 7% through wall (TW) and 4% TW.
Table 2 -Wear at Broached Tube Support Plate, % Through-Wall, SG 'A' Page 4 of 5 Row 12 12 Column 53 53 Support 06H 06H
%lw, 7%
4%
ECT Indications from Possible Loose Parts Possible Loose Part (PLP) signals were reported during ECT at six (6) locations in SG 'B' (see Table 3 below). Such indications may indicate the presence of a metallic object and were investigated with +pointTM. Visual inspections were also employed in an attempt to observe and retrieve all PLP reported from ECT. No object was observed in the area around columns 40-41. In the area of Columns 49-50, a sludge-like object was retrieved and crumbled when removed. The area around Row 81 Column 42, on the cold leg of the first support plate (01 C) was not accessible to inspect visually. No degradation was observed in conjunction with these indications.
Table 3 - PLP Indication Summary, SG 'B' No PLPs were identified in SG 'A'. A piece of stainless flexitallic gasket material was removed from SG 'A' during visual foreign object search and retrieval (FOSAR) activities on the hot leg at approximately Row 50 Column 38. The object was approximately 1.5 inches long by 0.25 inches wide. No degradation was present in the area and no secondary side wear was visible.
- e. Number of Tubes Plugged During the Inspection Outage for Each Active Degradation Mechanism No SG tubes required plugging as a result of this inspection.
- f. Total Number and Percentage of Tubes Plugged To Date The total number and percentage of tube plugged to date for SG 'A' is 013499 (0%). The total number and percentage of tube plugged to date for SG 'B' is 413499 (0.1 1%).
- g. The Results of Condition Monitoring, Including the Results of Tube Pulls and lnsitu Testing Condition Monitoring was completed. SG 'A' and 'B' did not exceed any performance criteria during the last operating cycles (since U2R26). Tube pulls and in situ testing were neither required nor conducted.
- h. The Effective Tube Plugging Percentage for All Plugging in Each SG No tube repair methods are approved for PBNP Unit 2. Therefore, the effective plugging levels are as stated per Section (f) above.
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