ML17056B756

Advises That Util 920303 Proposed Acceptance Criteria for Ultrasonic Insp of HPCS Nozzle Safe End to Safe End Extension Weld Generally Acceptable W/Listed Clarifications & Restrictions

ML17056B756
Person / Time
Site:	Nine Mile Point
Issue date:	03/30/1992
From:	Brinkman D Office of Nuclear Reactor Regulation
To:	Sylvia B NIAGARA MOHAWK POWER CORP.
References
TAC-M82892, NUDOCS 9204030117
Download: ML17056B756 (10)

Text

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Docket No. 50-410 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555

>hrch 30, 1992 Hr.

B. Ralph Sylvia Executive Vice President, Nuclear Niagara Mohawk Power Corporation

-301 Plainfield Road

Syracuse, New York 13211

SUBJECT:

ACCEPTANCE CRITERIA FOR ULTRASONIC INSPECTION OF NINE MILE POINT UNIT 2 HIGH PRESSURE CORE SPRAY NOZZLE SAFE END TO SAFE END EXTENSION WELD (TAC NO. M82892)

By letter dated March 3,

1992, Niagara Mohawk Power Corporation (NMPC) submitted for NRC staff review and approval inspection acceptance criteria and a proposed revision tc +he previcusly-~.~pro4:ed repair proce"...'Ire for the flaw in the weld (KC-32) joining the high pr~ssure core spray (HPCS) nozzle safe end to the safe end extension at Nine bile Point Unit 2 (NHP-2).

The HPCS safe end extension is connected to a 10-inch pipe and is made of SA-508, Class 1 ferritic steel.

The safe end is connected to the reactor nozzle and is made of SB-166 Inconel 600 material.

The weld uses an Inconel 82 Y-type consumable

insert, an Inconel 82 filler root pass with gas tungsten arc welding, and Inconel 182 fill passes with shielded metal arc welding.

NMPC detected the flaw using ultrasonic (UT) examination during the first refueling outage 'in October 1990.

At that time the flaw was determined to be

0. 15-inch in depth and 1.9-inch in length.

NHPC believed that the flaw exhibited the characteristics of intergranular cracking, which could be attributed either to stress corrosion or to hot cracking during fabrication or repair.

Subsequently, NHPC applied the mechanical stress improvement process (MSIP) to improve.the residual stress distribution around the tip of the flaw to contain the flaw growth.

After the MSIP, reinspection indicated that the flaw had increased to 0.35-inches in depth (41X of wall thickness) and 3.4-inches in length (11.3X of circumference).

The flaw growth was attributed to the HSIF which led to an increase in ultrasonic reflectivity of the flaw.

By letter dated'January 11, 1991, the NRC staff authorized NHP-2 to continue to operate, but requested NMPC to reexamine the flaw in the middle (mid-1991) of the second fuel cycle.

Before the mid-cycle inspection, the NRC staff

approved, by letter dated July 16,

1991, NMPC's proposed UT acceptance en(teria which limited the flaw growth to no more than 10X of 11.3X in length or>IIOX of 0.41t in depth.

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Hr. B. Ralph Sylvia brarch 30, 1992 By letter dated September 16,

1991, NHPC submitted the results of the mid-cycle inspection which indicated a decrease in the ultrasonic response of the flaw from 0.4lt to 0.38t in depth and from 11.3X to 11.0X of the weld circumference in length.

In the March 3, 1992, letter, NMPC requested to use the same UT acceptance criteria as above for the upcoming inspection during the second refueling outage which commenced on Harch 4, 1992.

The NRC staff has reviewed NHPC's proposed acceptance criteria and has concluded that these criteria are generally acceptable with the following clarifications and restrictions:

2.

3.

4, NHPC proposed that the flaw growth should not exceed 10X of the depth or length of the original flaw size (i.e.,

10X of 0.4lt or 10X of 11.3X).

Based on NMPC's criteria, the acceptable flaw size would not exceed 0.45lt in depth or 12.43/ in length.

However, to be conservative, the NRC staff believes that the acceptable flaw size should be based on the flaw size recorded during the 1991 mid-cycle inspection, such that the acceptable flaw size would be no greater than 0.42lt in depth or 12.21X in length.

In a teleconference on March 9,

1992, a

NHPC representative (Hr.

R. Abbott) indicated that the safe end extension will be replaced during the third refueling outage in late 1993.

In light of the impending safe end extension replacement, the NRC staff judges that the difference between the two criteria is insignificant.

Therefore, the NRC staff approves the NHPC's proposed criteria;

however, the approval is contingent upon the NHPC's commitment to replace the safe end extension during the third refueling outage.

If the upcoming inspection of the flaw shows zero growth, NMPC proposes to operate NHP-2 for up to 9700 hours0.112 days <br />2.694 hours <br />0.016 weeks <br />0.00369 months <br />.

Three months before the end of the 9700-hour period, NMPC will submit for NRC approval a plan to either continue the operation to the end of the cycle, which is about 12,000

hours, or reinspect and/or repair the flaw.

If the upcoming inspection of the flaw shows some growth but that growth is within the acceptance

criteria, NMPC proposes to operate NHP-2 for up to 6125 hours0.0709 days <br />1.701 hours <br />0.0101 weeks <br />0.00233 months <br /> (9700 hours0.112 days <br />2.694 hours <br />0.016 weeks <br />0.00369 months <br /> 3575 hours).

The 3575-hour reduction came from the period between the middle of the second fuel cycle to the end of that 'cycle.

Three months before the end of the 6125-hour period, NHPC will submit for NRC approval a plan to either continue operation to the end of that cycle, or reinspect and/or repair the flaw.

Should the upcoming inspection show an unacceptable flaw growth, NHPC proposes to implement a repair plan before restart.

The staff finds this proposal acceptable.

I

Hr. B. Ralph Sylvia March 30, 1992 5.

NHPC proposes to submit inspection results within 30 days after restart from the second refueling outage.

The NRC staff finds this proposal unacceptable.

Pursuant to Generic Letter 88-01, "NRC Position on IGSCC in BWR Austenitic Stainless Steel,"

the results of the second refueling outage inspection are to be submitted to the NRC for review and approval prior to resumption of NHP-2 operation.

6.

The above criteria are only applicable for the UT inspection during the second refueling outage.

The NRR staff has not completed its review of the revised repair plan forwarded by NHPC's Harch 3, 1992, letter.

Should NHPC need to repair the flaw as a result of the upcoming inspection, the NRC staff will provide a

supplement to this safety evaluation prior to restart of NHP-2.

If you have any questions regarding this action, please contact me at (301) 504-1409.

Sincerely, cc:

See next page Donald S.

Brinkman, Sentor Project Manager Project Directorate I-l Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation

J, C

Hr. B. Ralph Sylvia Niagara Mohawk Power Corporation Nine Mile Point Nuclear Station Unit No.

2 CC:

Hark J. Wetterhahn, Esquire Winston

& Strawn 1400 L Street, NW.

Washington, DC 20005-3502 Hr. Richard Goldsmith Syracuse University College of Law E. I. White Hall Campus

Syracuse, New York 12223 Resident Inspector Nine Mile Point Nuclear Station P. 0.

Box 126

Lycoming, New York 13093 Gary D. Wilson, Esquire Niagara Mohawk Power Corporation 300 Erie Boulevard West

Syracuse, New York 13202 Hr. David K. Greene Manager Licensing Niagara Mohawk Power Corporation 301 Plainfield Road

Syracuse, New York 13212 Ms.

Donna Ross New York State Energy Office 2 Empire State Plaza 16th Floor

Albany, New York 12223 Supervisor Town of Scriba Route 8, Box 382

Oswego, New York 13126 Regional Administrator, Region I U. S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Charles Donaldson, Esquire Assistant Attorney General New Yor k Department of Law 120 Broadway New York, New York 10271 Hr. Richard H. Kessel Chair and Executive Director State Consumer Protection Board 99 Washington Avenue

Albany, New York 12210 Hr. Hartin J.

HcCormick Jr.

Plant Manager, Unit 2 Nine Mile Point Nuclear Station Niagara Mohawk Power Corporation P. 0.

Box 32

Lycoming, New York 13093 Hr. Joseph F. Firlit Vice President - Nuclear Generation Nine Nile Point Nuclear Station Niagara Mohawk Power Corporation P. 0.

Box 32

Lycoming, New York 13093

Cf I

Mr. B. Ralph Sylvia March 30, 1992 5.

NHPC proposes to submit inspection results within 30 days after restart from the second refueling outage.

The NRC staff finds this proposal unacceptable.

Pursuant to Generic Letter 88-01, "NRC Position on IGSCC in BWR Austenitic Stainless Steel,"

the results of the second refueling outage inspection are to be submitted to the NRC for review and approval prior to resumption of NMP-2 operation.

6.

The above criteria are only applicable for the UT inspection during the second refueling outage.

The NRR staff has not completed its review of the revised repair plan forwarded by NMPC's March 3, 1992, letter.

Should NHPC need to repair the flaw as a result of the upcoming inspection, the NRC staff will provide a

supplement to this safety evaluation prior to restart of NHP-2.

If you have any questions regarding this action, please contact me at (301) 504-1409.

Sincerely, Original Signed By Donald S. Brinkman, Senior Project Manager Project Directorate, I-1 Division of Reactor Projects I/II Office of Nuclear Reactor Regulation cc:

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