05000287/LER-1982-009, Forwards LER 82-009/01T-0.Detailed Event Analysis Encl

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Forwards LER 82-009/01T-0.Detailed Event Analysis Encl
ML20027B460
Person / Time
Site: Oconee Duke Energy icon.png
Issue date: 09/10/1982
From: Tucker H
DUKE POWER CO.
To: James O'Reilly
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
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ML20027B461 List:
References
NUDOCS 8209210043
Download: ML20027B460 (2)


LER-1982-009, Forwards LER 82-009/01T-0.Detailed Event Analysis Encl
Event date:
Report date:
2871982009R00 - NRC Website

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DUKE POWER GOMPANYW N R0. R EGD L v.o. nox saiso

?9 tNTN.GFG CHAHLO'ITE. N.C. 28242 IIALH. TUCKER TELEPHONE September 10, 1982 32 SEP 17 P I : 5 3a 704) 373-4531 vsea rurssommt Mr. James P. O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303 Re: Oconee Nuclear Station Docket No. 287

Dear Mr. O'Reilly:

Please find attached Reportable Occurrence Report R0-287/82-09. This report is submitted pursuant to Oconee Nuclear Station Technical Specification 6.6.2.1.a(9),

and describes an incident which is considered to be of no significance with respect to its effect on the health and safety of the public. My letter of September 1, 1982 addressed the delay in preparation of this report.

Very truly yours, C&

Hal B. Tucker JCP/php Attachment cc: Document Control Desk Mr. W. T. Orders U. S. Nuclear Regulatory Commission NRC Resident Inspector Washington, D. C. 20555 Oconee Nuclear Station Records Center Mr. Philip C. Wagner Institute of Nuclear Power Operations Office of Nuclear Reactor Regulation 1820 Water Place U. S. Nuclear Regulatory Commission Atlanta, Georgia 30339 Washington, D. C. 20555 O

S (JFFICIAL COPjd fr Aj. >

DUKE POWER COMPANY OCONEE NUCLEAR STATION Report Number: R0-287/82-09 Report Date: September 10, 1982 Occurrence Date: August 4, 1982 Facility: Oconee Unit 3, Seneca, South Carolina Identification of Occurrence: Five Reactor Coolant Pump studs were determined to be degraded in size below acceptable limits.

Conditions Prior to Occurrence: Refueling Shutdown Description of Occurrence: Babcock and Wilcox established the minimum acceptable diameter for Unit 2 and 3 Reactor Coolant Pump (RCP) closure studs to be 3.250 inches. From this a procedure was written to inspect RCP closure studs at each refueling outage. On July 30, 1982, this procedure was followed and microm-eter readings were taken for stud diameter on Unit 3's RCPs 3A1, 3A2, 3B1, and 3B2. The data indicated discrepancies from data taken one year ago, and the accountable engineer asked for new reading on the closure stud diameters. At 1000 on August 4,1982, a seond micrometer reading was taken and it was determined that five studs, two on 3Al and three on 3A2 had been degraded in size below the minimum acceptable diameter.

Apparent Cause of Occurrence: The degraded closure studs were made from ASTM A-193 Grade B7 (AISI 4140) material which is a low alloy carbon steel. Crud, rust, boron, etc. were present in the motor stand opening. The apparent boric acid corrosion wastade had been occurring due to closure gasket leakage.

Analysis of Occurrence:

Because of problems at other operating plants Oconee had initiated a program to inspect RCP closure studs at each refueling outage.

From this. latest refueling inspection, since only two studs (nos. 7 and 8) on 3Al and three studs (nos. 18, 19 and 20) on 3A2 were found degraded and the average stud diameter on each pump was greater than 3.6",

the health and safety of the public were not endangered.

Corrective Action

The five studs were removed and replaced rithin the time frame of August 20 - 31.

The degraded studs were replaced using new studs of ASME SA 540 Grade B23, AISI 4340 which has 1.8% nickel not found in the AISI 4140 stud. This new stud's composition should be more apt to resist boric acid corrosion.

It is the same material used in the new stud installed in 3Al RCP in 1981 and has shown no noticeable sign of degradation in 14 months of use.

Two studs were shipped offsite to be coated with a petroleum based material which meets the requirement for a Class 1 material in the Power Chemistry Meiterial Guide Manual. Because Unit 3 was at cold shutdown at the time of discovery of this incident, no immediate corrective action was required to lessen the conse-quences of the incident or to stabilize the unit.

The closure stud inspection procedure, MP/2&3/A/1310/22, will be reviewed to determine if it needs to be revised to specify at what position on the stud the diameter is to be measured.

PL