ML20043C741

Forwards Structural Evaluation of Indications in Reactor Top Head at Ja Fitzpatrick Power Station, Based on Evaluation Analyses for Flaw Indications Identified During Routine Inservice Insps

ML20043C741
Person / Time
Site:	FitzPatrick
Issue date:	05/25/1990
From:	Brons J POWER AUTHORITY OF THE STATE OF NEW YORK (NEW YORK
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20043C742	List: ML20043C741 ML20043C745
References
JPN-90-040, JPN-90-40, NUDOCS 9006060125
Download: ML20043C741 (4)

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.May 25, 1990  ;

U.S. Nuclear Regulatory Commisaloil

• 0~040 Attn: Document Control Desk Mall Stop PI 137-Washington, D.C. 20553 I Subject' James A. FitzPatrick Nuclear Power Plant Docket No.50 333 Reactor Pressure Vessel Head Flaw Indication Inspections and Evaluation Analyses

Reference:

1. NYPA letter, W. Fernandez to J. P. Durr dated May 15,1903 (JAFP 90 0416).

Transmits preliminary data on reactor pressure vessel head inspections.

Dear Sir:

Gection XI, IWB 3125 of the 1980 Edition of the ASME Boiler and Pressure Vessel Code requires that the Authority submit evaluation analyses for flaw indications Identified during i routine Inservice inspections to the NRC. The Authority has completed analyses of a reactor  !

vossel head flaw identified during the 1990 refueling outage, i Attached are two repods which summarizes the Authority's findings. Attachment 1 describes the Authority's reactor vessel head inspections. Attachment 2 is an evaluation analysis of the .

head flaw Indications. A third report detailing the Authority's position on how metallic inclusions I (segregates) affected the exam will be submitted at a later date. -

Preliminary data on this flaw was transmitted to the NRC with Reference 1. Authority engineers met with the NRC staff on May 17,1990 to discuss the details of these vessel head indications. :D Should you or your staff have any questions regarding this matter, please contact Mr. J. B. Ellmers of my staff.

Very truly yours, n .Brons ,

ecutive Vice President

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475 Allendale Road i King of Prussia, PA 19400 Office of the Resident inspector U.S. Nuclear Regulatory Commission j' P.O. Box 136 Lycoming, NY 13093 David E. LaBarge  !

Project Directorate 11  !

Division of Reactor Projects 1/11 ,

U. S. Nuclear Regulatory Commission l Mall Stop 14 B2 Washington, D. C. 20555 3

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. f Attachment 1 to JPN 90040 New York Power Authority JAMES A. FITZPATRICK NUCLEAR POWER PLANT REACTOR VESSEL HEAD FLAW INSPECTIONS L

l l Introduction i As part of the Authority's routine ISI (in Service inspection) program for FitzPatrick, selected ,

reactor pressure vessel (RPV) head welds were inspected during the 1990 refueling outage.

Inspectors used UT (uttrasonic testing) techniques to detect and size flaws in weld metal.

l' UT inspections of one of the RPV welds (weld number VC TH-12) showed several recordable 1 indications. The largest indication was observed along approximately five inches of the

, circumferential weld between the upper dome plate (dollar plate) and the vertical dome segments, s Preliminary information was transmitted to the NRC with Reference 1. These indications were the subject of NRC Information Notice No. 90 32 (Reference 2) and General Electric Co. RICSIL 051 4 l (Reference 3).  ;

Additional exams were performed in accordance with the requirements of IWB 2430 as a result of

these findings. Visual exams were performed on the inside surface of the RPV head. No 7

rejectable indications were recorded.

Other inspections beyond those required by the code were conducted on weld VC-TH 12 to i

clarify the nature and extent of the flaws. These supplemental exams included RT, PT, and MT

' from beneath the head. UT exams were performed from both the outside and inside of the head.

Construction radiographs and those taken during the 1990 refueling outage were enhanced using computer aided techniques to better quantify the weld characteristic.

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' Ultrasonic Inspections Some of the UT exams used in sizing these flaws were hampered by the existence of numerous small reflectors about midwall of the plate. These reflectors are believed to be metallic inclusions (also known as plate segregates), possibly manganese sulfides. These inclusions are part of the steelmaking process and are considered acceptable by the manufacturing specification for ASME SA 533 Grade B steel. They were also observed during preservice UT inspections.

l When performing sizing exams with refracted longitudinal wave transducers, shear and longitudinal sound waves are generated. The UT inspectors initially confused the segregate response from shear waves with a flaw response from longitudinal waves. The shear waves reflected off the segregates generating a response near the center of the plate on the time display.

This yielded the anticipated flaw response from the longitudinal waves and as a result, inspectors exaggerated the flaw depth to be 2 inches. The length of the flaw was similarly overestimated.

Flaw Evaluation Two flaws were rejectable under the guidelines of Regulatory Guide 1.150 (Reference 4). These flaws were conservatively estimated to be 0.5 inch deep by 5 inches long, and 0.55 inch deep by

. 2.3 Inches long. For the purposes of the fracture mechanics evaluation, the flaws were assumed l to be open to the vessel interior (i.e. cracks) although inspection data indicates the contrary. The assumption that a crack exists is conservative since it presupposes growth and incroased stress lovels. Further details on the fracture mechanics evaluation are include in Attachment 2.

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- Attachment 1 to JPN 90-040 The conclusion that these indications are the result of segregates has been experimentally-confirmed during tests performed by General Electric on similar plate material similar. A report describing this test and other evidence to support this conclusion will be submitted to the NRC at a later date.

Future Examinations in accordance with IWB-2420, the RPV head flaws will be reexamined using UT techniques from  !

the outside of the head during the 1991 refueling and future outages.Section XI of the ASME requires that any significant flaw growth be reported to the NRC. j i

Conclusion 3 Based upon the Authority's inspections, and manufacturing records for the RPV head, it was i determined that the flaws are subsurface and due to original welding imperfections. Since the  ;

flaws are not connected to the surface, they were not characterized as cracks.  !

Based upon the results of evaluations performed in accordance with the FitzPatrick Technical Specifications, the FitzPatrick ISI Program, and ASME Section XI, continued operation with the existing reactor vessel head flaw indications do not constitute a safety concern.

References

1. NYPA letter, W. Fernandez to J. P. Durr dated May 15,1990 (JAFP 90-0416). Transmits - <

preliminary data on reactor pressure vessel head inspections.

2. NRC Information Notice No. 90 29, " Cracking of Cladding and its Heat affected Zone in the Base Metal of a Reactor Vessel Head," dated April 30,1990.

3. General Electric Co. RISCIL No. 051, " Reactor Pressure Vessel Head unear Indications," ,

dated May 3,1990.

4. NRC Regulatory Guide 1.150, " Ultrasonic Testing of Reactor Vessel Welds During Preservice and Inservice Examinations," Revision 1. February 1983.

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