FVY-87-100, Submits Results of 1987 Outage Core Spray safe-end Weld Overlay Insp Results,Per NRC .Exams Showed Weld Overlays & Underlying Nozzle,Weld & safe-end Matl Free from New or Propagating Defects

Submits Results of 1987 Outage Core Spray safe-end Weld Overlay Insp Results,Per NRC .Exams Showed Weld Overlays & Underlying Nozzle,Weld & safe-end Matl Free from New or Propagating Defects

ML20236C079
Person / Time
Site:	Vermont Yankee
Issue date:	10/20/1987
From:	Capstick R VERMONT YANKEE NUCLEAR POWER CORP.
To:	Office of Nuclear Reactor Regulation
References
FVY-87-100, NUDOCS 8710270005
Download: ML20236C079 (3)

Text

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VERMONT YANKEE NUCLEAR. POWER CORPORATION RD 5, Box 169, Ferry Road, Brattleboro, VT 05301 ,,,Ly yg ENGINEERING OFFICE 1671 WORCESTER ROAD

.~ FRAMINGHAM, M ASS USETTS 01701

. TELEPHONE 61 F8100 October 20, 1987

• FVY 87-100 pj c

- m tQ N T M United States Nucicar Regulatory Commission w -

Washington, DC 20555 >,9 Attention: Office of Nuclear Reactor Regulation cn Mr. V. L. Rooney, Senior Project Manager O Project Directorate I-3 Division of Reactor Projects I/II

References:

(a) License No. DPR-28 (Docket No. 50-271)

(b) Letter, VYNPC to USNRC, FVY 86-36, dated May 5, 1986 (c) Letter, VYNPC to USNRC, FVY 86-49, dated June 2, 1986 (d) Letter, USNRC to VYNPC, NVY 86-113, dated June 16, 1986 (e) Letter, VYNPC to USNRC, FVY 87-07, dated January 12, 1987 (f) Letter, VYNPC to USNRC, FVY 87-50, dated May 7, 1987 (g) Letter, USNRC to VYNPC, NVY 87-81, dated May 28, 1987

Subject:

1987 Outage Core Spray Safe-End Weld Overlay Inspection Results

Dear Sir:

By letter dated May 28, 1987 (Reference (g)], the Nuclear Regulatory Commission (NRC) approved Vermont Yankee's plans to inspect the two overlay repaired core spray safe-ends instead of replacing them during the 1987 refueling outage. That letter also requested Vermont Yankee to provide the results of the inspection no later than three weeks after plant startup following the 1987 refueling outage. In accordance with that request, Vermont Yankee herein provides the 1987 refueling outage liquid penetrant and ultrasonic examination results of the Vermont Yankee Core Spray System safe-end to reactor vessel nozzle weld overlay repair welds. These examinations showed the weld overlays and the underlying nozzle, weld, and safe-end material to be free from new or propagating defects. The examination results are discussed below.

The liquid penetrant examination was conducted prior to ultrasonic examination. The solvent removable red dye technique was used to examine the weld overlay surface, the overlay end tapers, and the safe-end and nozzle base material immediately adjacent to the overlay. Examination parameters were consistent with ASME,Section XI, and Yankee Atomic Electric Company (YAEC)

Procedure YA-PE-2. The examination was conducted by Level III personnel 8710270005 071020 PDR ADOCK 05000271 0 PDR 1 O

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United States Nuclear Regulatory Commission October 20, 1987 Attention: Mr. V. L. Rooney page 2 i

qualified in accordance with:SNT-TC-1A. Independent substantiating l interpretation was conducted by a second Level III. Minor noncelevant l indications were noted between weld beads in the as-welded end tapers. These ;

~ indications initiated the secondary substantiating interpretation and were I determined not relevant to this examination, nor were they located so as to j mask potentially relevant indications.

l Ultrasonic examination to detect possible flaws was conducted using two Level II and one Level III examiner qualified at the EpRI NDE Center to l examine weld overlay repairs. An additional Level III examiner qualified in  ;

accordance with the EPRI NDE Center program for sizing of' planar flaws was '

also on staff to serve as technical reviewer and to aid in measuring indications if found.

Examination techniques'were based upon the EPRI weld overtay inspection methodology with modifications and additions empirically demonstrated on the Vermont Yankee weld overlay mockup. The EPRI overlay ISI methodology relies on detection of crack faces utilizing 600 or 700 refracted longitudinal waves incident at, or nearly perpendicular to, an oriented, propagating crack face. Transducer size selection is a function of long-range overlay roughness. . Transducer focal length is based on empirical calibration demonstration.

The program implemented at Vermont Yankee was significantly more in depth than the EPRI methodology, even though Vermont Yankee has determined the i inspection of Inconel wold overlays to be somewhat less difficult than stainless steel overlays. Enhanced surface preparation requirements at installation allowed Vermont Yankee more latitude in transducer selection.

Transducer size and focal length were selected based upon the parameters believed necessary for proper examination. Each transducer was then demonstrated capable of detecting diffracted signals within its focal range. l particular attention was paid to the WOL-base metal interface. By application i of 700 (with accompanying OD creeping wave), 600, and 450F transducers )

nominally focused at 1.5", 1.7", and 1.9" of metal path, respectively, angle ]

beam scans were conducted looking for both axial and circumferential flaws. i In addition, a 00 (straight beam) interrogation of the entire volume was l made to detect any developing indications as might be experienced at the weld j overlay interface.

Based on the results of these examinations, wherein neither relevant l liquid penetrant indications nor ultrasonic indications were found, Vermont i Yankee concluded that acceptable overlay service had been demonstrated for this fuel cycle and that replacement of the core spray safe-ends during the 1987 outage was not warranted. We are currently updating our weld overlay documentation to incorporate the results of this inspection and the relevance i of the BWR nozzle cracking detected in a foreign reactor. Upon completion of I this effort, we will notify you of our evaluation results and future plans with regard to replacement of the safe-ends. l l

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+b l United States Nuclear Regulatory'Commissio.1 October'20, 1987

. Attention: Mr.1 V. L. Rooney Page 3 i l

We. trust- that this information'is acceptable; however. . Vermont Yankee is j Javailable to meet with'you to:present additional information regarding the 1987 refueling outage inspection methodology and results at your convenience.

Very truly yours, .

VERMONT YANKEE NUCLEAR POWER CORPORATION-J .

R. W. Cap tick Licensing Engineer

-RWC/25.193 l 1

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