NRC 2008-0016, Response to Request for Additional Information, Spring 2007 Unit 1 (U1R30), Steam Generator Tube Inspection Report

Response to Request for Additional Information, Spring 2007 Unit 1 (U1R30), Steam Generator Tube Inspection Report

ML080770187
Person / Time
Site:	Point Beach
Issue date:	03/14/2008
From:	Mccarthy J Florida Power & Light Energy Point Beach
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NRC 2008-0016, U1R30
Download: ML080770187 (6)

Text

FPL Energy Point Beach, LLC,6610 Nuclear Road, Two Rivers, WI 54241 FPL Energy Point Beach Nuclear Plailf March 14, 2008 NRC 2008-0016 TS 5.6.8 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Point Beach Nuclear Plant, Unit 1 Docket 50-266 Renewed License No. DPR-24 Response to Request for Additional lnformation Spring 2007 Unit 1 (U1R30)

Steam Generator Tube lnspection Report

Reference:

(1) FPL Energy Point Beach, LLC to NRC Letter Dated October 25, 2007, Spring 2007 Unit 1 (U1R30) Steam Generator Tube lnspection Report, (ML072990108)

(2) NRC to FPL Energy Point Beach, LLC Letter Dated February 12, 2008, Point Beach Nuclear Plant, Unit 1 - Request for Additional lnformation Related to the Steam Generator Tube Inservice lnspection Reports for Refueling Outage 30 (TAC NO. MD7231), (ML080370062)

Via Reference ( I ) FPL Energy Point Beach, LLC submitted the Unit 1 Spring 2007 Steam Generator Tube lnspection Report, documenting the scope and results of the inspection per prescribed technical specification reporting requirements.

On February 7, 2008, a telephone conference was held between NRC and PBNP personnel.

During the conference, the NRC staff and PBNP personnel discussed the spring 2007 Unit 1 steam generator report and additional information requested. It was agreed that the response to the request for additional information would be submitted by FPL Energy Point Beach, LLC by March 14,2008.

The enclosure of this letter provides the FPL Energy Point Beach, LLC response to the request for additional information listed as Reference (2).

The submittal contains no new commitments or revisions to existing commitments.

An FPL Group company

Document Control Desk Page 2 In accordance with 10 CFR 50.91, a copy of this response to a request for additional information is being provided to the designated Wisconsin Official.

Very truly yours, FPL Energy Point Beach, LLC 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 1 FPL ENERGY POINT BEACH, LLC POINT BEACH NUCLEAR PLANT, UNlT 1 SPRING 2007 UNlT 1 (U1 R30)

STEAM GENERATOR TUBE INSPECTION REPORT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION The following information is provided by FPL Energy Point Beach, LLC in response to the NRC staff's request for additional information dated February 12, 2008, regarding the U1R30 steam generator inspection report.

Question 1 At the time the first SG tube inspections were performed in your replacement SGs (presumably during refueling outage 12), how many effective full power months had the SGs operated? In addition, for the last several outages (e.g., since refueling outage 26),

please provide the cumulative effective full power months the SGs operated.

FPL Enerqv Point Beach. LLC Response WE Energies, the former asset owner, conducted the first inservice inspection of the Unit 1 steam generators (SG) during Unit 1 Refueling Outage 12 (U1R12) in April 1985.

The SGs accumulated approximately 11.5 effective full power months (EFPM) during the period between replacement in U1R11 and U1R12.

During the period between U1R26 and U1R30, the Unit 1 SGs accumulated approximately 63.8 EFPM.

Question 2 For the +pointTMexaminations that started slightly above the top of the tubesheet, please discuss the basis for selecting the height from which the exams started/terminated (i.e., why were some tubes examined to 8 inches above the top of the tubesheet while others were only examined to 3 or 6 inches above the top of the tubesheet).

FPL Enerqv Point Beach, LLC Response Using the eddy current test (ECT) results of U1R28, FPL Energy Point Beach coordinated with the ECT vendor to generate sludge height maps on the tubesheets of the Unit 1 SGs. These maps were used while developing the inspection plans for U1R30.

Based on the developed sludge height maps, the highest estimated sludge level for the hot leg of SG B was 4.55 inches above the tubesheet. This estimated sludge height was limited to an area encompassing two columns and seven rows in the tube bundle of the hot leg. Surrounding sludge heights were less than this. The entire area of elevated sludge height encompassed 342 tubes in the hot leg.

The varied heights for +pointTMexaminations stated in Reference 1 incorporated the mapped sludge heights. Tubes planned for inspection which were in the region of the Page 1 of 4

sludge pile incorporated an additional vertical buffer to account for the estimated sludge pile height.

Question 3 It was indicated that all dents and dings at tube supports and in the U-bends were inspected with a +pointTMcoil. Please discuss the reporting threshold for dents and dings at these locations (e.g., 2-volts).

FPL Energy Point Beach, LLC Response During U1R30 FPL Energy Point Beach employed a 2 volt threshold for designating dings and dents. All dings and dents greater than or equal to 2 volts in the U-bends and supports were inspected with a rotating +pointTMcoil. The 2 volt threshold was based on industry experience indicating that dings and dents at these locations may not be reliably discernable from signals such as the supports using the bobbin probe. Dings and dents below this threshold are expected to have no impact on detection probability of stress corrosion mechanisms using bobbin probe techniques. For the bobbin probe, FPL Energy Point Beach utilized the Electric Power Research Institute (EPRI) eddy current examination technique specification sheet (ETSS) 96012.1. This ETSS provides the industry qualification of the bobbin probe examination technique to meet the requirements for detection of axial primary water stress corrosion cracking (PWSCC) at support intersections with dents less than 2 volts.

Question 4 Please discuss whether the "very small fine wire" observed in SG B was removed from the SG. If not, discuss the basis for acceptance of leaving the wire in the SG.

FPL Energv Point Beach. LLC Response The wire was evaluated and left in the SG. The decision was based on a number of considerations. The size and dimension of the wire was determined to be as stated in Reference 3, approximately 1/64 inch diameter by 112 inch long, for SG A. Supporting analysis concluded a 40% through-wall wear time of 4.6 years or at least two cycles of operation. Furthermore, as assessed through the visual inspection following sludge lancing, the wire appeared embedded in the sludge pile on the tubesheet.

As stated in Reference 1, no wear was observed by ECT and no wear was observed during the secondary side visual inspection. Based on the size, location, the potential to tube damage during retrieval in bundle, concerns for additional dose and the fact the wire remained post sludge lancing, the wire was left in place. Also as stated in Reference 1, similar wires have been seen historically and it is anticipated that planned chemical cleaning of the Unit 1 SGs in 2008 will eliminate the presence of remaining fine wires.

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Question 5 It was indicated that visual inspections were performed at various locations on the secondary side of the SG. Please discuss the scope and results of any other secondary side inspections performed during refueling outage 30 (2007).

FPL Enerqv Point Beach, LLC Response During U1R30 the scope of the secondary side visual inspections included the following:

Steam drum (Upper shell and upper internals including primary and secondary moisture separator assemblies), feed ring and J-nozzles, Sixth (top) support plate quatrefoil inspection, Pre-sludge lance potential loose part (PLP) Identification, and Post-sludge lance cleanliness and foreign object search and retrieval (FOSAR).

Follow up trending for J-nozzles 2 & 3 melt-through and secondary moisture separator perforated plate bulge on E bank, and Follow up trending of sixth (top) support plate quatrefoil inspection.

SG B Inspection Results Tubesheet cleanliness and FOSAR visual inspections included the annulus, no-tube lane and select in bundle columns during U1R30. Adherent scale in SG B continues to be observed similar to that described in Reference 2 for SG A. A very small fine wire was observed in bundle as per response to Question 4 above.

As stated in Reference 1, a PLP identified by the eddy current testing was inspected prior to sludge lancing and was as described, likely to be scale pieces.

An inspection of the top (sixth) support plate was conducted. No anomalies on the lower U-bends or foreign objects on the support plate were observed. Quatrefoils were inspected as well. Conditions were generally similar to those found in SG A during the U1R29 and re-inspection this outage. The degree of blockage within individual foils ranged from zero to 100%. The overall aggregate may be slightly less than in SG A, which is estimated at 40% blockage. As mentioned in Reference 4, blockage of this type can have impact on tube integrity. Chemical cleaning is scheduled for the fall of 2008.

This cleaning is expected to eliminate or minimize this blockage.

A visual inspection of the steam drum and upper internals was conducted. Flow impingement patterns were seen on the feedwater ring, on the outside of some primary moisture separator riser barrels as well as under and around several J-nozzles. Erosion of the feedwater ring and riser barrel areas was not discernible by touch.

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One perforated plate on the secondary moisture assembly is bowed. The bow observed in the perforated plate of the secondary moisture assembly in SG B is consistent with that observed for SG A during U1R29, as described in Reference 3. In addition, there was noted melt-through on the interior of some J-nozzles where the J-nozzle is welded to the feed ring. This was also observed with the J-nozzles in SG A during U1R29 as reported in Reference 2.

SG A Inspection Results SG A was inspected to reevaluate melt-through in the J-nozzles and bowing of the perforated plate of the secondary moisture assembly as previously reported in References 2 and 3. No change was noted, validating the FPL Energy Point Beach's previous conclusion that these areas are from initial construction and are not service related defects.

A follow-up inspection of quatrefoil blockage on the top support plate observed during U1R29 was conducted. The conditions appear to have not changed from observations during outage U1R29. The degree of blockage within individual foils ranged from zero to 100%. The overall aggregate is estimated at 40% blockage. As mentioned in Reference 4, blockage of this type can have impact on tube integrity. Chemical cleaning is scheduled for the fall of 2008. This cleaning is expected to eliminate or minimize this blockage.

References

1. FPL Energy Point Beach, LLC to NRC Letter, "Spring 2007 Unit 1 (U1R30) Steam Generator Tube lnspection Report," dated October 25, 2007, (ML072990108)

2. Letter from Nuclear Management Company, LLC letter to NRC, "Fall 2005 Unit 1 (U1R29) Steam Generator Tube lnspection Report," dated February 21, 2006, (ML060600189)

3. Letter from Nuclear Management Company, LLC letter to NRC, "Response to Request for Additional lnformation Fall 2005 Unit 1 (U1 R29) Steam Generator Tube lnspection Report," dated July 14, 2006, (ML061980407)

4. NRC lnformation Notice 2007-37, "Buildup of Deposits in Steam Generator," dated November, 23,2007, (ML072910750)

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