ML20236C571

Safety Evaluation Granting Util 870430 Request for Relief from Inservice Insp Requirements for Outside Diameter Surface Exam of Reactor Vessel nozzle-to-safe-end Butt Welds

ML20236C571
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	07/20/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20236C557	List: ML20236C554 ML20236C571
References
NUDOCS 8707300112
Download: ML20236C571 (4)

Text

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION CONCERNING RELIEF FROM INSERVICE INSPECTION REQUIREMENTS FOR N0ZZLE-TO-SAFE END WELDS CONNECTICUT YANKEE ATOMIC POWER COMPANY HADDAM NECK PLANT DOCKET N0. 50-213 1.0' BACKGROUND Paragraph 10 CFR 50.55a(a)(3) states that proposed alternatives to the require-ments of paragraphs (c), (d), (e), (g), and (h) of this section'or portions thereof may be used when authorized by the Director of-the Office'of Nuclear Reactor Regulation. The applicant must demonstrate that (1) the proposed alternatives .would provide an acceptable level of quality and safety, or (ii). compliance with the specified requirements of this section would result

' in hardship level or unusual of quality difficulties and safety. without Paragraph a compensating) increase in the 10CFR50.55a(g)(6(1)alsoauthorizes the Commission to grant relief from those requirements that are impractical to perform because of the plant's design, geometry, and material of construction of the components ~upon making the necessary findings.

By letter dated April 30, 1987, CYAPC0 (the licensee) determined that certain inservice examination requirements of the'1980 Edition through Winter 1980 Addenda of Section XI of the ASME Code at the Haddam Neck Plant are impracti-cal to perform during the second ten-year inspection interval. Specifically, the licensee requested relief from the outside diameter (OD) surface examina-r tion of the reactor vessel nozzle-to-safe end butt welds. The staff evaluation

. finds the licensee's supporting technical justification to be conditionally  ;

acceptable.

2.0 RELIEF REQUEST AND TECHNICAL JUSTIFICATION A. Code Requirement Item B5.10, Category B-F: Reactor Vessel Nozzle-to-Safe End Butt Welds l

, Table IWB-2500-1 specifies that a volumetric examination of one-

l. third of the volume at the inside diameter'(ID) and a surface examination of the OD is required for all dissimilar metal welds  ;

to the extent defined in Figure IWB-2500-8. '

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B.- . Code' Relief: Request

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• The licensee requested relief from performing the OD surface ~examin-iation on all' reactor. vessel' nozzle-to-safe end butt welds greater-

'than 4' inches-in diameter.-

C. Licensee-Basis for Relief-The Haddam Neck Plant is a four-loop'PWR with eight reactor' vessel '

nozzle-to-safe'end butt welds, under; Examination Category.B-F. 'In 1980 a surface examination was performed on all eight welds. No service-induced indications were reported as: part of this examination.

An. ALARA' review' was completed tha't identified a tot'al radiation- .

exposure of 10.90 man-rem for the 203_ man hours required to perform.

the Code, examination.

Included as'part of this man-rem number was

.a; surface examination of four safe'end to pipe welds located adjacent

.to the nozzle-to-safe'end welds ~. The man-rem totals also include any-

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. preparation work required such as insulation removal / replacement,

' weld cleaning, or. scaffolding erectionn A total of_ twelve,(12) welds

. examined with an average. rate of. exposure of.0.9 man-rem per weld.

In 1987,_six' welds are required to be examined to fulfill.the Code '

requirements. Approximately 5.5 man-rem will be used in examining these. welds.

The ultrasonic examination of the nozzle-to-safe end welds will be performed from the ID surface using the remote imersion method. -

CYAPC0 believes that any failure of the weld wil1~be induced:from

.the'.ID surface'and'that the ultrasonic examination ~of this surface a will'be sufficient-to. detect any indications. InLits' commitment to

' reduce:overall exposure rates, CYAPC0 believes that the ultrasonic examination will assi E in reducing'the exposure rates, without losing the ability.to detect' flaws in the reactor vessel nozzle-to-safe end welds.

As au alternative to the surface examination the licensee proposes the following:

A._ The subject welds will receive a volumetric examination in accordance with ASME Code Section'XI and Regulatory Guide 1.150.

B. The OD surfaces shall be visually examined during the reactor coolant system hydrostatic test,.in accordance with Examination Category B-P, Table IWB-2500-1.

3.0L EVALUATION Pursuant to 10 CFR 50.55a(a)(3) the staff evaluated the existing design, geometry and materials of construction of the reactor vessel nozzle-to-safe i end welds. ~The Code required surface examination is technically feasible  ;

since the licensee performed these examinations in 1980..

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, The required examination method would be effective for the detection of surface-connected flaws, if present. The Code emphasized the examination of dissimilar metal welds and this surface and volumetric examination was established when ASME Code Section XI was first published in 1971.

The extent of the examination contained in the initial 1971 Code document was more than the current requirement for Haddam Neck by requiring a volumetric examination for the entire weld and a surface examination for at least one wall thickness beyond the edge of the weld.

The staff rewgnizes the potential radiation exposure associated with the surface examination. In addition, the licensee proposes to perform an examination of the subject welds based on Regulatory Guide 1.150.

This alternative examination significantly exceeds the requirements of l ASME Code Section XI. The Code contains provision for alternative ex-l amination methods which are demonstrated to be equivalent or superior to the specified method.

The staff has determined that the licensee's proposed alternative of an ID volumetric examination and visual examination during the hydrostatic test is equivalent or superior to the Code requirements and is acceptable provided that the licensee meet the following conditions:

(1) The remote volumetric examination includes the entire weld volume and heat affected zone instead of only the inner one-third of the weld.

(2) The ultrasonic testing instrumentation and procedure are demonstrated to be capable of detecting OD surface-connected defects, in the circumferential orientation, in a laboratory l -- test block. The defects should be cracks and not machined notches.

Considering the time required to obtain an appropriate laboratory test block with artificially induced flaws, the staff finds that this demonstration of detection capability may be performed as a confirmatory issue prior to the next refueling outage. The staff agrees with the licensee that an ID examination of the full weld volume, based on Regulatory Guide 1.150, should detect any significant flaw that could affect the structural integrity of the welds. The staff determined that the additional assurance of weld integrity derived from performing the surface examination of the OD is not l commensurate with the projected high man-rem expenditure.

4.0 CONCLUSION

Pursuant to 10 CFR 50.55a(a)(3) the staff concludes that relief may be granted for the licensee to substitute an ID volumetric examination for the Code required OD surface examination. The bases for this conclusion 1-

'i s- _4 is that the volumetric-examination, subject to the conditions' defined'in.

the staff evaluations will be equivalent or superior to the Code require-ment.

5.0.; ACKNOWLEDGEMENT Principal Contributor: Martin Hum, EMTB, NRR.

c. Dated: JUL 2 01987 l

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