ML20045G678

SER Accepting Licensee Proposed Alternative to ASME Code Section XI Requirements Per 10CFR50.55a(a)(3)(i)

ML20045G678
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	07/09/1993
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20045G677	List: ML20045G676 ML20045G678
References
NUDOCS 9307150037
Download: ML20045G678 (4)

Text

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y[pR RIGg.h Enclosure efE a

UNITED STATES NUCLEAR REGULATORY COMMISSION i.

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WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE INSERVICE TESTING PROGRAM RELIEF RE0 VESTS i

CONNECTICUT YANKEE ATOMIC POWER COMPANY HADDAM NECK PLANT DOCKET NUMBER 50-213

1.0 INTRODUCTION

1.1 Purpose To determine whether Connecticut Yankee Atomic Power Company-(the licensee's) proposed alternative to its commitments to the requirements of the ASME Code, 1983 Edition, Summer 1983 Addenda provides an acceptable level of quality and safety.

1.2 Background

During the current Cycle 17 refueling outage, the licensee inspected the elbow to nozzle weld of steam generator No. 4 as part of its inservice inspection program per ASME XI.

Radiography showed indications of cracking.

These results required expanding the sample to include four more pipi nids. The licensee chose to examine only the elbow to nozzle welds of the e.her three steam generators since it believed these welds to be susceptible to the same cracking. The detection of more rejectable indications in two of the other three nozzles required further expanding the sample per ASME Section XI IWC-2430 to include the entire feedwater system.

Licensee's Relief Request The licensee has attributed the cracking to thermal fatigue which occurs at the feedwater nozzle-to-elbow area. The licensee believes that it is not necessary to examine all these welds to determine the adequacy and operability of the feedwater system. However, the edition of the ASME Code the licensee has committed to in its inservice inspection program, the 1983 Edition, Summer 1983 Addenda, does not provide the flexibility to differentiate between susceptible and nonsusceptible weld locations.

The licensee proposes an alternative program under 10 CFR 50.55a(a)(3)(i).

The licensee believes that the proposed alternative provides an acceptable level of quality and safety.

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2.0 EVALUATION OF RELIEF RE0 VEST 1~

Code Requirement ASME Code,Section XI, 1983 Edition, Summer 1983 Addenda, Paragraph IWC-2430 describes the Code requirements.

Code Relief Request The licensee requests relief from expanding the sample to include the entire feedwater system.

Basis for Relief Inservice inspection and testing of American Society of Mechanical Engineers (ASME) Code Class 1, 2, and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable Addenda as required by 10 CFR 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(1).

Paragraph 10 CFR 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if the proposed alternatives would provide an acceptable level of quality and safety.

J Paragraph 10 CFR 50.55a(g)(4)(iv) permits a licensee to meet the requirements set forth in subsequent editions of ASME Section XI referenced in 10 CFR 50.55a(b) subject to the limitations and modifications listed therein and J

subject to Commission approval.

Portions of editions or addenda may be used provided that all related requirements of the respective editions or addenda are met.

Licensee's Proposed Alternative Plan In order to ensure that the pipe / fitting welds in the feedwater system are not susceptible to the type of cracking detected in the feedwater nozzle to elbow welds, the licensee will complete the following additional inspections and evaluations prior to returning the plant to service:

(1)

Expand the inspection scope to include the first two welds beyond the first vertical pipe section in lines supplying steam generators Nos. 2 and 4.

These welds were chosen based on the magnitude of the cracking detected in the steam generators Nos. 2 and 4 nozzles and also to include both the long and the short piping arrangements between the containment penetration and the steam generators. The purpose of these inspections is to verify that global system stratification beyond the first vertical pipe section does not exist.

(2)

Perform a visual examination of the feedwater piping rigid restraints inside containment to confirm the absence of support damage resulting from global system stratification caused by system back flow. The absence of support deformation / damage confirms that the Haddam Neck

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l feedwater system is not subjected to the stratification phenomena l

described in Inspection and Enforcement (I&E)Bulletin 88-11, in I&E Information Notice 91-38 and in Information Notice 84-87.

(3)

Examine the piping welds in the pipe which supplies S/G #4 adjacent to the containment penetration. The absence of unacceptable indications in this weld further confirms that global stratification resulting in high loads at the system fixed ends, does not exist.

(4) The indications detected in the 1993 radiographs were also detected in the 1979 and the 1980 radiographs.

For this reason the licensee has reviewed the remainder of the I&E Bulletin 79-13 inspection results to confirm that no additional questionable indications were detected in any of the areas originally covered by the Bulletin.

(5) The licensee has reviewed the industry history related to steam generator feedwater nozzle cracking to determine if significant cracking resulting from stratification loads has been detected beyond the first vertical piping run. This review did not reveal any instances where cracking related to stratification loads was detected beyond the first horizontal section of piping adjacent to the feedwater nozzle.

(6) The feedwater system has been subjected to the ASME Section XI inservice inspection requirements which included inspection of numerous welds since 1979. A review of these inspection results revealed no unacceptable crack-like indications detected during these inspections.

l (7) The licensee will complete a structural evaluation of the feedwater l

nozzle and the piping to determine the critical flaw size for the system.

This critical flaw size will then be compared to the maximum flaw size which could have been missed during inspection to confirm the absence of structurally significant flaws.

Staff Evaluation The NRC staff evaluated the licensee's alternative as a plant-specific action.

The licensee has demonstrated by an engineering evaluation that the cracking found during the current inspection is typical of the feedwater nozzles only and does not occur at other locations.

In additon, the licensee examined two more welds in the lower elbows of the lines which supply steam generators Nos.

2 and 4 respectively and did not find any cracking. These results support the conclusions of the engineering evaluation.

The staff agrees that the indications are most likely due to fatigue cracking from thermal stratification. The staff also agrees that the cracking is probably limited to the area near the feedwater nozzle.

Cracking caused by l

thermal fatigue is commonly being reported by the industry, and results at Haddam Neck are consistent with those being reported by other licensees.

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.. Previous studies have.shown that cracking from thermal fatigue is not a significant safety issue. The staff agrees that working to the proposed alternate plan should provide an acceptable level of quality and safety.

3.0 CONCLUSION

S The NRC staff concludes that the licensee's proposed alternative is acceptable and authorized under 10 CFR 50.55a(a)(3)(1) and will provide an acceptable level of quality and safety.

Principal Contributor:

M. Banic Date:

July 9, 1993 i

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