ML023020010

Summary of Conference Call with Duke Energy 2002 Steam Generator Results

ML023020010
Person / Time
Site:	Oconee
Issue date:	10/29/2002
From:	Olshan L NRC/NRR/DLPM/LPD2
To:	Mccollum W Duke Energy Corp
Olshan L N, NRR/DLPM, 415-1419
References
TAC MB4458
Download: ML023020010 (5)

Text

October 29, 2002 Mr. William R. McCollum, Jr.

Vice President, Oconee Site Duke Energy Corporation 7800 Rochester Highway Seneca, SC 29672

SUMMARY

OF CONFERENCE CALL WITH DUKE ENERGY COMPANY REGARDING THE 2002 STEAM GENERATOR INSPECTION RESULTS AT OCONEE NUCLEAR STATION, UNIT 1 (TAC NO. MB4458)

Dear Mr. McCollum:

On March 14, 19, and 25, and April 5, 17, and 22, 2002, your staff and our staff participated in conference calls regarding the steam generator inspection activities at Oconee Nuclear Station, Unit 1. Enclosure 1 is a brief summary of the calls, and Enclosures 2 and 3 contain material your staff sent us in preparation for the calls.

Based on the information discussed during the calls, we did not identify any issues requiring further discussion.

Sincerely,

/RA/

Leonard N. Olshan, Project Manager, Section 1 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-269

Enclosures:

1. Summary of Calls with Duke Energy Company Regarding 2002 Steam Generator Results at Oconee Nuclear Station, Unit 1

2. ONS 1EOC-20 Steam Generator Inspection Plans

3. ONS-1B Sever of Tube 78-124 cc w/encls: See next page

October 29, 2002 Mr. William R. McCollum, Jr.

Vice President, Oconee Site Duke Energy Corporation 7800 Rochester Highway Seneca, SC 29672

SUMMARY

OF CONFERENCE CALL WITH DUKE ENERGY COMPANY REGARDING THE 2002 STEAM GENERATOR INSPECTION RESULTS AT OCONEE NUCLEAR STATION, UNIT 1 (TAC NO. MB4458)

Dear Mr. McCollum:

On March 14, 19, and 25, and April 5, 17, and 22, 2002, your staff and our staff participated in conference calls regarding the steam generator inspection activities at Oconee Nuclear Station, Unit 1. Enclosure 1 is a brief summary of the calls, and Enclosures 2 and 3 contain material your staff sent us in preparation for the calls.

Based on the information discussed during the calls, we did not identify any issues requiring further discussion.

Sincerely,

/RA/

Leonard N. Olshan, Project Manager, Section 1 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-269

Enclosures:

1. Summary of Calls with Duke Energy Company Regarding 2002 Steam Generator Results at Oconee Nuclear Station, Unit 1

2. ONS 1EOC-20 Steam Generator Inspection Plans

3. ONS-1B Sever of Tube 78-124 cc w/encls: See next page Distribution:

PUBLIC HBerkow MLesser PDII-1 R/F JNakoski SRosenberg LOlshan CHawes RHaag, RII OGC MKotzalas ACRS/ACNW BFu JZwolinski/LMarsh KKarwoski ADAMS ACCESSION No: ML023020010 OFFICE PDII-1/PM PDII-1/LA PDII-1/SC NAME LOlshan CHawes JNakoski DATE 10/25/02 10/24/02 10/25/02 OFFICIAL RECORD COPY

SUMMARY

OF CONFERENCE CALLS WITH DUKE ENERGY COMPANY REGARDING 2002 STEAM GENERATOR INSPECTION RESULTS AT OCONEE NUCLEAR STATION, UNIT 1 The NRC staff participated in conference calls with Duke Energy Company (the licensee) on March 14, 19, and 25, and April 5, 17, and 22, 2002, to discuss the steam generator (SG) inspection results from the 20th refueling outage at Oconee Nuclear Station, Unit 1 (Oconee 1).

During the calls prior to and on April 17, 2002, the NRC staff and the licensee discussed the licensees actions in response to NRC Information Notice 2002-02 (IN 2002-02), Recent Experience with Plugged Steam Generator Tubes (ADAMS Accession Number ML013480327). As discussed in the information notice, certain plugged tubes may be susceptible to severance as a result of tube vibration and other factors (e.g., tube swelling).

The scope of the licensees inspection is included in the materials provided by the licensee in support of these calls.

On April 22, 2002, the NRC and the licensee discussed the steam generator tube inspection scope, the eddy current data analysis results, tube plugging and repair plans, and in-situ pressure testing. At the time of the call, the licensee had already completed the inspection.

Details of the inspection results are contained in the attached inspection summary that the licensee provided in support of this call. Additional clarifying information provided during the call is provided below.

The inspection scope included the following:

C 100% of tubes in both SGs by bobbin probes C 100% of sleeved tubes in both SGs by bobbin probes C Lane and wedge areas with two rows around the sleeved tubes with plus point probes C 100% of the upper tube sheet with plus point probes C 100% of re-rolls in the upper tube sheet with plus point probes C 100% of I-600 plugs with plus point probes C 100% of the sleeve upper and lower rolls C 100% of tubes in the kidney region (sludge piles) with plus point probes C Rotating pancake coil (RPC) for areas of special interest, including 100% of bobbin indications and 100% of all dents regardless of size or location Prior to shutdown for the inspection, Oconee 1 was experiencing a 1 to 2 gallons per day primary-to-secondary leak. However, no secondary side pressure tests were conducted during the outage.

During the April 22, 2002, phone call, the licensee discussed the location and size of significant indications detected during the outage inspection that will be included in the 90-day report Enclosure 1

issued after the outage. The licensee discussed two indications detected at dents, one was axial in nature and the other was circumferential. Both indications initiated from the inside diameter of the tube. The licensee stated that the axial indication was considered small. The licensee also discussed indications found in the freespan region. The freespan cracks were axial in nature and initiated from the outside diameter.

Six tubes were in-situ pressure tested during the 20th refueling outage. These tubes contained axial freespan primary water stress corrosion cracking indications located at dents, axial outside diameter stress corrosion cracking/intergranular attack indications, and volumetric indications.

The licensees in-situ pressure-testing criteria used crack length and indication voltage to determine whether an indication fell within a required zone for testing. According to the licensees screening criteria, only some of these indications required testing up to the structural integrity limit of three times the normal operating differential pressure (3P). During these tests, all tubes maintained leakage integrity, and all tubes chosen for testing up to the 3P limit maintained structural integrity. The graphical representation of the in-situ pressure-testing criteria suggests that a flaw with a relatively large crack length but low voltage would not fall in the required zone of testing. The licensee indicated that it historically has in-situ pressure tested selected tubes even though the selection criteria indicated the licensee did not need to test them.

As a result of inspecting plugged tubes in response to the information contained in Information Notice 2002-02, the licensee identified a wear scar on a plugged tube (B77-123). Because this indication was not present when the tube was plugged in 1991, the licensee performed a secondary side visual inspection. This inspection led to the discovery of a circumferentially severed plugged tube (B78-124) next to the affected (B77-123) tube. Tube B78-124 was severed at the secondary face of the lower tube sheet. The licensee performed in-situ pressure tests on the tubes with wear scars and reported that the test results were satisfactory, indicating that the severed tube had not significantly impacted the integrity of its neighboring tubes (all of which were plugged during prior outages).

The licensee removed portions of several of the affected tubes for destructive examination, including the severed tube. The destructive examinations, although inconclusive, indicated that the tube severed as a result of intergranular attack originating from the inside diameter of the tube. There were no obvious indications of fatigue or significant ductile tearing. The severed tube was 1 of 12 tubes instrumented with thermocouples during the first cycle of operation (early 1970s). The tubes in which these thermocouples were installed were plugged at one end while the other end remained open. Following the first cycle of operation, the thermocouples were removed and the tubes were plugged at the open end. The licensee speculated that the instrumentation (thermocouple) installed for the first cycle of operation is one of the causal factors. After the completion of the licensees root cause evaluation, the NRC staff issued an information notice that summarized the finding (Refer to IN 2002-02, Supp. 1.).

At the conclusion of the April 22, 2002, call, the NRC staff requested that the licensee contact the NRC if the licensee identifies anything significantly different from that discussed during the call. The NRC staff also expressed an interest in receiving an update on the licensees metallurgical analysis of the severed plugged tube and on the final root cause determination.

Oconee Nuclear Station cc:

Ms. Lisa F. Vaughn Mr. L. E. Nicholson Legal Department (PBO5E) Compliance Manager Duke Energy Corporation Duke Energy Corporation 422 South Church Street Oconee Nuclear Site Charlotte, North Carolina 28201-1006 7800 Rochester Highway Seneca, South Carolina 29672 Anne W. Cottingham, Esquire Winston and Strawn Ms. Karen E. Long 1400 L Street, NW Assistant Attorney General Washington, DC 20005 North Carolina Department of Justice Manager, LIS P. O. Box 629 NUS Corporation Raleigh, North Carolina 27602 2650 McCormick Drive, 3rd Floor Clearwater, Florida 34619-1035 Mr. C. Jeffrey Thomas Manager - Nuclear Regulatory Senior Resident Inspector Licensing U. S. Nuclear Regulatory Duke Energy Corporation Commission 526 South Church Street 7812B Rochester Highway Charlotte, North Carolina 28201-1006 Seneca, South Carolina 29672 Mr. Richard M. Fry, Director Mr. Henry Porter, Director Division of Radiation Protection Division of Radioactive Waste Management North Carolina Department of Bureau of Land and Waste Management Environment, Health, and Department of Health and Environmental Natural Resources Control 3825 Barrett Drive 2600 Bull Street Raleigh, North Carolina 27609-7721 Columbia, South Carolina 29201-1708 Mr. Peter R. Harden, IV Mr. Michael A. Schoppman VP-Customer Relations and Sales Framatome ANP Westinghouse Electric Company 1911 North Ft. Myer Drive 6000 Fairview Road Suite 705 12th Floor Rosslyn, VA 22209 Charlotte, North Carolina 28210