NRC-99-0041, Requests Relief from ASME Section XI Requirements to Examine Essentially 100% of Accessible Category B-D Nozzle Welds,Per 10CFR50.55a(g)(5)(iii).Rev 1 to Relief Request RR-A6,encl

Requests Relief from ASME Section XI Requirements to Examine Essentially 100% of Accessible Category B-D Nozzle Welds,Per 10CFR50.55a(g)(5)(iii).Rev 1 to Relief Request RR-A6,encl

ML20206S793
Person / Time
Site:	Fermi
Issue date:	05/14/1999
From:	Gipson D DETROIT EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CON-NRC-99-0041, CON-NRC-99-41 NUDOCS 9905240002
Download: ML20206S793 (11)

Text

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1)ouglas R. Gipson Senior Vice President, Nuclear Generation o

Fermi 2 6400 North Dixie llwy., Newport, Michigan 481f,6

. Tel: 734.586.5201 Fax: 734.686.4172 Detroit Edison May 14,1999 NRC-99-0041 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington D C 20555-0001

References:

1) Fermi 2 NRC Docket No. 50-341 NRC License No. NPF-43

2) NRC Letter to Detroit Edison,

" Safety Evaluation on the First Ten-Year Interval Inservice Inspection Program Plan for Fermi 2",

(TAC No. 59616), dated October 6,1987

Subject:

Revision of Relief Reauest RR-A6 Reactor Vessel Nozzle Welds Requerts for relief from the American Society of Mechanical Engineers (ASME)

Code,Section XI requirements were submitted to the NRC and were approved with the First Ten-Year Interval, Inservice Inspection (ISI) Nondestructive Examination (NDE) Program with Reference 2.

Relief Request RR-A6 documented ultrasonic examination limitations based on interference caused by proximity to instrumentation nozzles. Fermi ISI personnel have identified other examination limitatioas based on reactor vessel design that is applicable to all boiling water reactors. This type of relief has been granted for other Boiling Water Reactors (BWRs), e.g., Clinton Power Station.

The limitations to full ASME Code volumetric coverage are detailed in Enclosure 1, k Relief Request RR-A6, Revision 1. Pursuant to 10 CFR 50.55a(g)(5)(iii) Detroit Edison is requesting relief from ASME Section XI requirements to examine f

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USNRC NRC-99-0041 Page 2 essentially 100% of accessible Category B-D nozzle welds, because within the limits of design and accessibility it is impractical to do so.

Should you have any questions or require additional information, please contact Mr. Norman K. Peterson of my staff at (734) 586-4258.

Sincerely, Enclosure l l

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cc: A. J. Kugler A. Vegel NRC Resident Office Regional Administrator, Region III  !

Supervisor, Electric Operators, )

Michigan Public Service Commission i

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9 ENCLOSURE 1 TO NRC-99-0041 RELIEF REQUEST RR-A-6 REVISION 1 l

n Enclosure I to NRC-99-0041 Page1 RELIEF REQUEST RR-A6 REVISION 1 COMPONENT FUNCTION / DESCRIPTION:

l Pressure Retaining Reactor Pressure Vessel (RPV) Nozzle to Shell Welds (See Table 1) l SYSTEM:

1 Reactor (B11)

ASME CODE CLASS:

Class 1 l ASME SECTION XI REOUIREMENTS:

Subsection IWB, Table IWB 2500-1, Examination Category B-D, Item Nos. B3.90 and B3.100 require volumetric examination of RPV nozzle-to-shell welds and base material regions as shown in figure 2500-7(b).

BASIS FOR RELIEF:

Pursuant to 10 CFR 50.55a(g)(5)(iii) Detroit Edison is requesting relief from ASME Section XI requirements to examine essentially 100% of accessible Category B-D nozzle welds, because within the limits of design and accessibility it is impractical to do so.

Relief Request RR-A6 only documented ultrasonic examination limi:ations based on interference caused by proximity to other nozzles. Other limitations have been identified during the performance of examinations during the first interval.

The primary limitation to full ASME Code volumetric covenge is nonle configuration. The nozzle type used in the Fermi 2 reactor is a flanged nozzle as shown in Figure 1. This type cf nozzle provides the best access for inspection of the nozzle types perraitted in the ASME Code as shown in the Figures ofIWB-2500-7. The Code required solume (t/2) extends into the nozzle outside blend radius. The curve of the radius section hinders the ability of transducers to maintain contact with the nozzle and also changes the effective beam angle. This limitation results in a typical maximum composite coverage of all Code required scans (0{ Longitudinal},

- 45, and 60 { Parallel & Transverse} degree) between 60% and 70% depending on nozzle diameter and thickness. The maximum obtainable coverage is achieved by the 60 degree transverse (T) scan. Essentially all of the weld and heat affected zones are covered by this angle beam scan for

Enclosure 1 to NRC-99-0041 Page 2  !

. the entire weld circumference on most nozzles. Typical scan limitations are shown in Figures 2A through 2C The estimated volumetric coverage obtained is reported in Table 1.

Another limitation to full ASME Code volumetric coverage is the vessel taper at the bottom head to lower shell course weld. This geometric condition prevents full coverage of the bottom side of the twojet pump instrumentation nozzles and the two recirculation suction nozzles. Composite coverage for these welds remains above 60%. This limitation also impacts the nozzle inner radius coverage for the two core spray nozzles as reported in Table 1.

The limitation originally described in RR-A6 of this relief request indicated a limitation of 46 degrees or 12.8% of the full circumference for 2 of 6 feedwater nozzles based on automated examination equipment accessibility. The examinations were performed manually and the limitation was less than originally described and accepted (see Figure 3). A part of the scan path was able to be performed for the full circumference. Additionally, Fermi examines these feedwater nozzles as specified in NUREG 0619 to detect cracking in the nozzle inner radius and bore areas where cracks have previously been detected in other BWRs. These exams were fully completed and no service related flaws have been detected.

All nozzle forgings received ultrasonic examination during manufacture and the nozzle to shell welds were subject to radiographic examination during fabrication of the reactor pressure vessel.

All of the nozzle welds requiring volumetric examination by ASME Section XI have been completed during the first ten-year inspection interval and no service related defects have been detected. The nozzle inner radius ultrasonic examination techniques used at Fermi performed scanning from the blend radius; however, since this technique was designed to detect internal surf ace defects no credit has been taken for those exams.

Reactor Vessel Ultrasonic Examination techniques meet the requirements of ASME Section XI; ASME Section V, Article 4; and Regulatory Guide 1.150. Detroit Edison believes that the extent of examinations completed satisfy the intent of the ASME Code and 10 CFR 50.55a(g)(4) within the limits of accessibility for examination inherent to BWR pressure vessel design.

ALTERNATIVES:

Perform examination of the ASME Code volume to the extent practical.

APPLICABLE TIME PERIOD:

Reliefis requested for the first 10-year inspection interval.

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. l Enclosure 1 to NRC-99-0041 Page 3

. I RR-A6 Table 1 LIMITED EXAMINATIONS Category Weld Estimated Limitation Description

/ Item Identification Coverage B-D/B3.90 8-316A, through 69.1 % Nozzle Blend Radius Nozzle Weld 8-316-D B-D/B3.90 4-316A ~60% Nozzle Blend Radius and Nozzle Weld 4-316D Instrumentation Nozzles B-D/B3.90 4-316B, C 64.1 % Nozzle Blend Radius Nozzle Weld E, & F B-D/B3.90 14-316A 68.9 % Nozzle Blend Radius Nozzle Weld 14-316B l B D/B3.90 15-315 68 % Nozzle Blend Radius i Nozzle Weld l B-D/B3.90 13-314A 66.7 % Nozzle Blend Radius j Nozzle Weld through 13-314K B D/B3.90 5-314A 65.6 % Nozzle Blend Radius and Bottom Head Nozzle Weld 5-314B to Shell Taper B-D/B3.90 19-314 A 63.1 % Nozzle Blend Radius and Bottom Head Nozzle Weld 19-314B to Shell Taper B-D/B3.90 2-318 61.4% Nozzle Blend Radius Nozzle Weld B D/B3.90 4-318A 62 % Nozzle Blend Radius Nozzle Weld 4-318B B-D/B3.100 19-314A 80.2 % Bottom Head to Shell Taper Nozzle Weld 19-3148 l

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