ML050250225

Revision of the Core Shroud Support Weld H9 Inspection Plan for Refueling Outage (RFO)-18

ML050250225
Person / Time
Site:	Nine Mile Point
Issue date:	01/14/2005
From:	Spina J Constellation Energy Group
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NMP1L 1916
Download: ML050250225 (5)

Text

Constellation Energy P.O. Box 63 Nine Mile Point Nuclear Station Lycoming, New York 13093 January 14, 2005 NMP1L 1916 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001

SUBJECT:

Nine Mile Point Unit 1

__DocketNo:50- 2 200--

License No. DPR-63 Revision of the Core Shroud Support Weld H9 Inspection Plan for Refueling Outage (RFO)-18 Gentlemen:

By letter dated August 2, 2001, Niagara Mohawk Power Corporation (NMPC), the former licensee, submitted the results of the H9 weld inspection and associated flaw evaluation and the priposed reinspection plan fodrthe'Weld toihe'Nilcleai Regulatory Comnmissior(NRC)'f6r review. 'The flaw evaluatio n and pr6possd reinspection plan were accepted by the NRC in its letteriand 'safety evaluation (SE) daied October 31, 2001.

For the H9 weld, the reinspection plan included a volumetric inspection during Refueling Outage (RFO)-17 using ultrasonic testing (UT) methods. Subsequently, in a letter dated December 13, 2002, Nine Mile Point Nuclear Station, LLC (NMPNS), requested NRC approval of an extension allowing the H9 weld reinspection to be completed during RFO-18 instead of RFO-17. The NRC staff reviewed NMPNS's extension request and, by letter and SE dated March 20, 2003, approved the extension.

-The purpose of this letter-is .to request.NRC approval .of a proposed .change-to the H91 weld recirculation NI nozzle locations to be UT inspected during RFO-18. Nine Mile Point Unit I (NMPI) has five recirculation NI (suction) nozzles. The reinspection plan proposed by NMPC in the August 2, 2001 letter, and subsequently approved by the NRC, identified the NI nozzles to be inspected as NIA, NIC, and N1E based on sampling of indications for inspection. However, a recent revision to the planned RFO-18 American Society of Mechanical Engineers (ASME)Section XI recirculation NI nozzle inspections resulted in the loss of accessibility to the NIA inspection location. NMPNS is, therefore, requesting approval of the NID inspection location as an acceptable replacement for the previously approved N1A location. Inspection of the NID nozzle location in lieu of the NIA location represents an improvement' a's compared to the previously approved sampling. Accordingly, the proposed : .

scope for

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th"e'19 weld Reispection remains

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- - - Ao Page 2 NMP1L 1916 adequate to verify that the attachment weld indications are contained in the attachment weld and the flaw evaluations are valid. Attachment 1 to this letter provides the necessary background and justification for the proposed change to the NI nozzle inspection location. NMPNS requests NRC approval of the proposed change by March 1,2005 to support outage planning for RFO-18.

Sincerely, Je ~A.Spina Vice President Nine Mile Point JAS/CDMIjm Attachment cc: Mr. S. J. Collins, NRC Regional Administrator, Region I Mr. G. K. Hunegs, NRC Senior Resident Inspector Mr. P. S. Tam, Senior Project Manager, NRR (2 copies)

ATTACHMENT 1 NINE MILE POINT UNIT 1 (NMPI)

ENGINEERING BASIS FOR REVISION OF THE CORE SHROUD SUPPORT WELD H9 INSPECTION PLAN FOR REFUELING OUTAGE (RFO)-18

Background

By letter dated August 2, 2001 (Reference 1), Niagara Mohawk Power Corporation (NMPC), the former licensee, submitted the results of the H9 weld inspection and associated flaw evaluation and the reinspection plan for the weld to the Nuclear Regulatory Commission (NRC) for review. For the H9 weld, the reinspection plan included a sample volumetric inspection during RFO-17 using ultrasonic testing (UT)

- Methods. Spifically;-t e-reinspection-plan for the-H9 weld committed to a UT -

inspection of the reactor pressure vessel (RPV) H9 weld attachment location from the vessel outside diameter (OD) at recirculation suction nozzles NIA, NIC, and NIE.

NMPI .has five recirculation NI (suction) nozzles (NIA - NIE). By letter and enclosed safety evaluation (SE) dated October 31, 2001 (Reference 2), the NRC accepted the flaw evaluation and proposed reinspection plan for the H9 weld. Subsequently, in a letter dated December 13, 2002 (Reference 3), Nine Mile Point Nuclear Station, LLC (NMPNS), requested a deferral of the RPV H9 weld OD UT inspection from RFO-17 to RFO-18. The locations to be inspected remained unchanged. The basis for this deferral was the recognized benefit in terms of radiological dose reduction that would be gained by postponing the H9 weld reinspection until after decontamination of the recirculation piping, which is planned for RFO-18. By letter dated March 20, 2003 (Reference 4), the NRC concurred with the deferral of the H9 weld reinspection from RFO-17 to RFO-18.,

In the Reference 1 letter, the original H9 weld reinspection plan scope for RFO-17 identified three recirculation Ni nozzles for inspection. The NMP1 RPV OD clearances restrict the locations of the H9 weld inspection to regions near the recirculation Ni nozzles. During RFO-17, nozzles NIA, NIC, and NIE were scheduled for American Society of Mechanical Engineers (ASME)Section XI nozzle to vessel weld inspection.

These three nozzle locations were expected to allow coverage of two of the four higher amitude indications and seven of the lower amplitude indications, thus providing an adequate sampling to confirm that the H9 alloy 182 indications are confined to the weld metal. As previously discussed, the NRC concurred with the proposed reinspection plan and also concurred with the deferral of the reinspection to RFO- 18 (References 3 and 4,,

respectively).

Proposed Change and Justification A recent revision to the planned RFO-18 ASME Section XI recirculation NI nozzle inspections has resulted in the loss of accessibility to the NIA inspection location. The proposed change to the reinspection location has been reviewed to verify that the inspection coverage is at least equivalent to that originally considered acceptable. The NID and NIB nozzle locations will be accessible based on current plans for RFO-18.

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As shown in Table 1, the Ni D nozzle location represents an improvement in flaw indication number and length coverage when compared to the NlA location.

Although nozzle location NIB will now be accessible based on the current plans for RFO-18 ASME section XI inspections of the safe-end, an additional dose will be incurred to complete another UT from the vessel OD at the NIB nozzle. Since the proposed scope for RFO-18 is improved as compared the scope previously approved, the additional man-rem that would be incurred to perform NIB nozzle OD inspection is not considered technically justified. The proposed scope remains adequate to verify that the attachment weld indications are contained in the attachment weld and that the flaw evaluation assumptions are valid.

During RFO-17, an opportunity became available to inspect the NIE nozzle location. An inspection was, therefore, performed from the RPV OD and was qualified for detection flaws-in the vessel in both the-circumferential -and -axial orientations-- The-

-and-sizin-of inspection coverage achieved included the regions of the flaws described in Table 1. The inspection did not identify any new flaw indications. The inspection coverage satisfied the purpose of the inspection and the results confirmed that the H9 attachment weld flaws were confined to the weld, with no crack propagation into the RPV low alloy steel. The NIE inspection volume enveloped the region containing indications 31, 32, 33, and 34, as described in Table 1 (Table 2 of Reference 1). The NIE location is considered the best NI nozzle inspection location since it includes indication 34, which is one of the indications that matched the BWRVIP amplitude for BWRVIP mockup indications "h" and "i," and three indications that were evaluated in Reference 1 as likely to be primarily axial oriented flaws similar to the Tsuraga cracking morphology. Note that the NIE nozzle will not be inspected during RFO-18 since it was inspected during RFO-17.

Table 1 H9 Vessel OD Coverage Estimates Recirculation Access Locations and Flaw Indication No. Flaw Indication Suction Nozzle Coverage Estimate (Location) Length (NMPI has 5 Ni nozzles) (1.85 inches per degree) (degrees / inches)

NIA (Not accessible in 420 (_ +/- 10 degrees) #3 (55.65°) 1.120 / 2.07" RFQ-18)

-NI B -------- -^ 140.(

1S 10 degrees) -Fi9g(117.99°) - 0.56°. / 04" - -

NIC (Inspection planned 1860 (_ +/- 10 degrees) #16 (177.610) 0.700/ 1.29" for RFO-18) #17 (192.030)* 4.060 i7.5 1"

1. 18 (196.230) 0.840 1.55"

1. 19 (197.630) 4.340/ 8.02" NID (Inspection planned 2580 (- +/- 10 degrees) #26 (248.730) 2.240/ 4.14" for RFO-18) #27 (256.010) 0.560 / 1.04"

1. 28 (256.7 10) 0.420 / 0.78"

1. 29 (257.830) 0.980 / 1.81" NIE (Inspection 3300 achieved #31 (324.590) 3.360 / 6.21 "

performed in RFO-17) (_ 45" length with NIE #32 (328.230) 0.420 / 0.78" centerline at 20" #33 (331.870) 0.840 / 1.55"

. (_ +/- 120)) #34 (336.49°)* 2.520 / 4.66"

• Indications that match the BWRVIP amplitude for BWRVIP mockup indications h and i.

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Conclusion A recent revision to the planned RFO-18 ASME Section XI recirculation Ni nozzle inspections resulted in the loss of accessibility to the NIA inspection location. NMPNS is, therefore, requesting approval of the NID inspection location as an acceptable replacement for the previously approved NlA location. As shown in Table 1, inspection of the NID nozzle location in lieu of the NIA location represents an improvement as compared to the previously approved sampling coverage. Accordingly, the proposed scope for the H9 weld reinspection remains adequate to verify that the attachment weld indications are contained in the attachment weld and the flaw evaluations are valid, while minimizing radiological dose to plant personnel.

References

1) NMPC letter to NRC dated August 2, 2001 (NMP1L 1603), "Inspection Results for Core Shroud Support Welds H8 and H9"

2) NRCletter to NMPC dated October 31, 2001, "Nine Mile Point Nuclear Station, Unit No. 1 - Inspection Results for Core Shroud Support Welds H8 and H9 (TAC No.

MB2528)"

3) NMPNS letter to NRC dated December 13, 2002 (NMPlL 1702), "Inspection of Core Shroud Support Weld H9 - TAC No. MB6893"

4) NRC letter to NMPNS dated March 20, 2003, "Nine Mile Point Nuclear Station, Unit No. I - Inspection of Core Shroud Support Weld H9 (TAC No. MB6893)"

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