ML17059B054
| ML17059B054 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 02/12/1996 |
| From: | Edison G NRC (Affiliation Not Assigned) |
| To: | Sylvia B NIAGARA MOHAWK POWER CORP. |
| References | |
| GL-88-01, GL-88-1, TAC-M93744, TAC-M94350, NUDOCS 9602150311 | |
| Download: ML17059B054 (8) | |
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UN)TED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 February 12, 1996 5o-Q~
Mr. B. Ralph Sylvia Executive Vice President, Nuclear Niagara Mohawk Power Corporation Nine Mile Point Nuclear Station P.O.
Box 63
- Lycoming, NY 13093
SUBJECT:
HIGH PRESSURE CORE SPRAY (HPCS)
NOZZLE SAFE-END EXTENSION (KC-32)
WELD INSPECTION FREQUENCY, NINE MILE POINT NUCLEAR STATION, UNIT 2 (TAC NOS.
M93744 AND M94350)
Dear Mr. Sylvia:
By letter dated September 22, 1995, you requested NRC staff approval to recategorize the weld (KC-32) joining the High Pressure Core Spray (HPCS) nozzle safe end to the safe end extension.
During the first refueling outage, an indication was identified in this weld using UT inspection techniques.
Niagara Mohawk Power. Corporation (NMPC) applied Mechanical Stress Improvement Process (MSIP) to improve the residual stress distribution in the region of the flaw to eliminate the potential for flaw growth.
After MSIP application, UT inspections were again performed during the first refueling outage, at a
mid-cycle outage during the second fuel cycle, and at the second, third, and fourth refueling outages.
No growth in the flaw was identified.
NMPC has detox>ined that the stabilization of the flaw is due to the application of MSIP which has maintained the flaw in compression.
By letter dated July 8,
Nine Mile Point 2
(NMP2)
Technical Specification 4.0.5.f states that an inservice inspection program for piping identified in Generic Letter (GL) 88-01 shall be performed in accordance with staff positions.
In accordance with GL 88-01, "NRC Position on IGSCC in BWR Austenitic Stainless Steel Piping," weld KC-32 was categorized as an intergranular stress-corrosion cracking (IGSCC) Category "F" weld which requires that all indications be inspected every refueling outage.
Welds that have been treated by stress improvement that are classified as IGSCC Category "F" because they do not meet the applicable Staff positions may be upgraded to Category "E" if no adverse change in crack condition is found after four successive examinations.
Category "E" welds are examined once every other outage.
NMPC has performed four successive examinations which indicate no adverse change in the cracking condition.
One exam was performed at a mid-cycle and three were performed during refueling outages.
All four of the exams indic~te that MSIP has been effective in mitigating any crack growth and the intent of GL 88-01 has been met.
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B. Sylvia In a conference call held on February 1,
- 1996, you addressed the NRC staff's concerns regarding variations in the measured flaw size arid the effectiveness of thc HSIP in arresting deep cracks.
The subject safe..end weld had been UT examined five times during the last three fuel cycles after application of HSIP.
The reported flaw depth varied. from 29X to 41X of wall thickness and its length varied from 8.3X (2.5 inches) to 11.3X (3.4 inches) of the weld circumference.
In the conference call, you stated that the variations in the flaw size were caused by uncertainties in the UT examinations and is bounded by the maximum flaw size (41X in depth and 11.3X in length) measured in the December 1990 refueling outage.
You also stated that NHPC will'erform a weld overlay repair on the subject safe end weld if the flaw depth exceeds 41X of the wall thickness or the flaw length exceeds 11.3X of the weld circumference.
Your commitment for weld overlay repair as stated above is similar to that made in your previous submittal dated July 8, 1993.
Considering the range of the UT results reported in the last five examinations, the NRC staff finds that the NNPC proposed criteria for weld overlay repair of the subject safe end weld are acceptable.
Therefore, the NRC staff grants approval to upgrade the weld (KC-32) joining the nozzle safe end to the safe end extension to Category "E."
Sincerely, Docket No. 50-410 cc:
See next page Gordon E. Edison, Senior Project Manager Project Directorate I-1 Division of Reactor Projects - I/II Office-of"Nuclear Reactor Regulation
i P
II 1
B. Ralph Sylvia Niagara aloha k Pox<<!r Corpo>ation Nine Nile Point Nuclear Station Un!it 2 CC:
hark J. Wetterhahn, Esquire Winston
& Strawn 1400 L Street, NW.
Washington, DC 20005-3502 Mr. Richard Goldsmith Syracuse University College of Law E. I. White Hall Campus
- Syracuse, NY 12223 Resident Inspector Nine Mile Point Nuclear Station P.O.
Box 126
- Lycoming, NY 13093 Gary D. Wilson, Esquire Niagara Mohawk Power Corporation 300 Erie Boulevard West
- Syracuse, NY 13202 Hs. Denise J. Wolniak Manager Licensing Niagara Mohawk Power Corporation Nine Mile Point Nuclear Station P.O.
Box 63
- Lycoming, NY 13093 Hr. F. William Valentino, President New York State
- Energy, Research, and Development Authority 2 Rockefeller Plaza
- Albany, NY 12223-1253 Supervisor Town of Scriba Route 8, Box 382
- Oswego, NY 13126 Hr. John V. Vinquist, MATS Inc.
P.O.
Box 63
- Lycoming, NY 13093 Regional Administrator, Region I U. S. Buclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Charles Donaldson, Esquire Assistant Attorney General New York Department of Law 120 Broadway New York, NY 10271 Hr. Richard M. Kessel Chair and Executive Director State Consumer Protection Board 99 Washington Avenue
- Albany, NY 12210 Hr. Kim A. Dahlberg Plant Manager, Unit 2 Nine Mile Poil>C Nuclear Station Niagara Mohawk Power Corporation P.O.
Box 63
- Lycoming, NY 13093 Hr. Richard B. Abbott Vice President Nuclear Generation Niagara-Mohawk Power Corporation Nine Nile Po.lnt Nuclear Station P.O.
Box 63
- Lycoming, NY 13093 Hr. Hartin J.
HcCormick, Jr.
Vice'President Nuclear Safety Assessment and Support Niagara Mohawk Power Corporation Nine Nile Point Nuclear Station P.O.
Box 63
- Lycoming, NY 13093
ll
'L
B. Sylvia In a confer ence call held on February 1,
- 1996, you addressed the NRC staff's concerns regarding variations in the measured flaw size and the effectiveness of the MSIP in arresting deep cracks.
The subject safe end weld had been UT examined five times during the last three fuel cycles after application of MSIP.
The reported flaw depth varied from 29X to 41X of wall thickness and its length varied from 8.3X (2.5 inches) to 11.3X (3.4 inches) of the weld circumference.
In the conference call, you stated that the variations in the flaw size were caused by uncertainties in the UT examinations and is bounded by the maximum flaw size (41X in depth and 11.3X in length) measured in the December 1990 refueling outage.
You also stated that NMPC will perform a weld overlay repair on the subject safe end weld if the flaw depth exceeds 41X of the wall thickness or the flaw length exceeds 11.3X of the weld circumference.
Your commitment for weld overlay repair as stated above is similar to that made in your previous submittal dated July 8, 1993.
Considering the range of the UT results reported in the last five examinations, the NRC staff finds that the NMPC proposed criteria for weld overlay repair of the subject safe end weld are acceptable.
Therefore, the NRC staff grants approval to upgrade the weld (KC-32) joining the nozzle.safe end to the safe end extension to Category "E."
Sincerely, Original signed by:
Docket No. 50-410 cc:
See next page DISTRIBUTION:
Docket File PUBLIC PDI-1 R/F S.
Varga J. Zwolinski L. Harsh S. Little G. Edison K. Cotton W.
Koo Gordon E. Edison, Senior Project Manager Project Directorate I-1 Division of Reactor Projects I/II Office of Nuclear Reactor Regulation J. Strosnider OGC ACRS
- RConte, RI D. Terao DOCUMENT NAME:
G:iNMP2iNM294350.LTR
- See previous concurrence To receive a copy of this document, indicate in the box:
"C" = Copy without attachment enclosure "E" = Co y with attachment encl ure "N" = No co y OFFICE LA:PD I-E
- PM:PDI-1 PH:PDI-1
- EHCB D:PDI-1 NAME SLittl DATE 02/ Ig /96 KCotton rsl 01/11/96 GEdison 02/
6 Officia R cord Copy JStrosnider 02/12/96 LHarsh
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