ONS-2015-015, Revised Reply to a Notice of Violation; EA-14-091

Revised Reply to a Notice of Violation; EA-14-091

ML15055A598
Person / Time
Site:	Oconee
Issue date:	02/19/2015
From:	Batson S Duke Energy Corp
To:	Document Control Desk, NRC/RGN-II
References
EA-14-091, ONS-2015-015
Download: ML15055A598 (6)

Text

DUKE Scott L. Batson Vice President Oconee NuclearStation Duke Energy ONO1VP 17800 Rochester Hwy Seneca, SC 29672 o: 864.873.3274 ONS-2015-015 10 CFR 2.201 f 864.873.4208 Scott.Batson@duke-energy.com February 19, 2015 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Subject:

Duke Energy Carolinas, LLC (Duke Energy)

Oconee Nuclear Station, Unit 1 Docket No. 50-269 Revised Reply to a Notice of Violation; EA-14-091

References:

1. Letter from Victor M. McCree (NRC) to Scott Batson (Duke Energy), Oconee Nuclear Station - Final Significance Determination of White Finding, Notice of Violation and Assessment Follow-up Letter (NRC Inspection Report No.

05000269/2014012),. dated August 12, 2014 (ML14224A629)

2. Letter from Scott Batson (Duke Energy) to NRC, Reply to a Notice of Violation; EA-14-091, dated September 11, 2014 In a letter dated August 12, 2014 (Reference 1), the Nuclear Regulatory Commission (NRC) provided Duke Energy with the final significance determination for a White finding and an associated Notice of Violation, EA-14-091. The Nuclear Regulatory Commission (NRC) letter provides final results of the significance determination of the preliminary Greater than Green finding identified in NRC Inspection Report 05000269/2014011, dated June 26, 2014 (ML14177A333). The report identifies a violation of 10 CFR 50, Appendix B, Criterion XVI, Corrective Action which involves Oconee Nuclear Station's (ONS) failure to identify and correct a significant condition adverse to quality involving a crack in a weld located in the Unit I High Pressure Injection system. In response, Duke Energy provided the reply to the Notice of Violation EA-14-091 on September 11, 2014 (Reference 2), in accordance with 10 CFR 2.201, "Notice of Violation."

This letter provides an amended reply to Notice of Violation EA-14-091 that includes revised causal information and corrective actions resulting from completion of the associated root cause analysis. Due to the nature of the changes, Duke Energy has determined that a revision to the September 11, 2014, reply to the Notice of Violation is warranted. The attachment to this letter provides Duke Energy's revised reply to Notice of Violation EA-14-091. This revised reply supersedes the previous reply to the Notice of Violation provided in Reference 2.

www.duke-energy.com

U.S. Nuclear Regulatory Commission February 19, 2015 Page 2 There are no regulatory commitments contained in this submittal. Any questions regarding the content of this report should be directed to Chris Wasik, Oconee Nuclear Station Regulatory Affairs Manager, at 864-873-5789.

Sincerely, Scott L. Batson Site Vice President Oconee Nuclear Station Attachment

U.S. Nuclear Regulatory Commission February 19, 2015 Page 3 cc w/

Attachment:

Mr. Victor McCree Administrator, Region II U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, GA 30303-1257 Mr. James R. Hall Senior Project Manager (by electronic mail only)

U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation 11555 Rockville Pike Mail Stop 0-8 G9A Rockville, MD 20852-2746 Mr. Jeffrey Whited Project Manager (by electronic mail only)

U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation 11555 Rockville Pike Mail Stop 0-8 BlA Rockville, MD 20852-2746 Mr. Eddy Crowe NRC Senior Resident Inspector Oconee Nuclear Station Ms. Susan E. Jenkins Manager, Infectious and Radioactive Waste Management Division of Waste Management South Carolina Department of Health & Environmental Control 2600 Bull Street Columbia, SC 29201

Oconee Nuclear Station Revised Reply to Notice of Violation EA-14-091 Attachment NRC Violation:

10 CFR Part 50, Appendix B, Criterion XVI, Corrective Action, states, in part, that measures shall be established to assure that conditions adverse to quality, such as failures, malfunctions, deficiencies, deviations, defective material and equipment, and non-conformances are promptly identified and corrected. In the case of significant conditions adverse to quality (SCAQ), the measures shall assure that the cause of the condition is determined and corrective action taken to preclude repetition.

Contrary to the above, prior to November 11, 2013, the licensee failed to establish measures to promptly identify and correct a significant condition adverse to quality involving a circumferential crack in weld 1-RC-201-105 located on the Unit 1 High Pressure Injection (HPI) piping-to-cold leg nozzle safe end interface of the 1B2 reactor coolant pump suction pipe, which resulted in non-isolable pressure boundary leakage while the reactor was in Mode 1. Specifically, in 2004, the licensee implemented procedure, NDE [Non-Destructive Examination] -995, "Ultrasonic Examination of Small Diameter Piping Butt Welds and Base Material for Thermal Fatigue Damage," to perform augmented in-service inspection program ultrasonic examinations which did not provide measures to assure that HPI nozzle component cracking would be identified and corrected. Consequently, in 2012, the licensee performed procedure NDE-995 on weld 1-RC-201-105, and did not identify any reportable indications; even though the > 50%

through wall circumferential crack was present in the weld. The presence of the crack was confirmed after a re-review of a radiographic film obtained during a non-destructive test of the 1B2 thermal sleeve in 2011. On November 11, 2013, the licensee identified the through-wall circumferential crack in weld 1-RC 201-105 after transitioning Unit 1 to Mode 3 to investigate non-isolable pressure boundary leakage.

This violation is associated with a White significance determination process finding.

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Oconee Nuclear Station Revised Reply to Notice of Violation EA-14-091 Oconee Nuclear Station (ONS) Response to the Notice of Violation:

(1) the reason for the violation Duke Energy acknowledges this violation. This violation was attributed to an unisolable reactor coolant system leak on the 1B2 HPI line. On November 8, 2013, the ONS Unit 1 control room received indications of potential reactor coolant system (RCS) leakage in the Unit 1 reactor building. On November 10, 2013, following initial indication of RCS leakage in the vicinity of 1HP-1 52, Operations initiated power reduction to 20% full power. On November 11, 2013, a reactor building entry determined RCS pressure boundary leakage from 1 B2 High Pressure Injection (HPI) nozzle or piping. A shutdown to Mode 5 was initiated in accordance with Tech Spec 3.4.13, Operational Leakage.

The leak was from a circumferential crack in the safe end-to-pipe butt weld (1-RC-201-105) located between the 1B2 HPI injection nozzle and valve 1HP-152. The total circumferential extent of the aggregate crack was about 1.2" on the pipe inside diameter and about 0.1" on the outside surface.

An internal investigation was conducted by Duke Energy to evaluate the cause of both the weld failure and Duke Energy's failure to identify the crack before it became through-wall. Mechanical, high-cycle fatigue caused a through-wall crack in the butt weld between the safe end and HPI pipe. The crack in the HPI safe end-to-pipe butt weld developed when the system vibration exceeded material fatigue endurance limits causing the crack initiation from the weld root. Duke Energy's investigation also determined that ownership and oversight of the augmented examination program was inadequate, as was guidance to the examiners for actions to be taken when full weld volume coverage could not be achieved.

(2) the corrective steps that have been taken and the results achieved, Upon identification of the RCS leak, ONS Unit 1 was shut down for initial investigation and the weld repairs. On November 19, 2013, the leaking weld was replaced.

Post-repair Radiographic Testing was completed November 23, 2013. Additional actions include the following:

1. Remaining ONS HPI safe end-to-pipe butt welds for Units 1 and 2 have been re-inspected using diverse techniques, (e.g., PDI-UT-2, which calls for a different UT beam angle to be used than that recommended in previously used procedure NDE-995, Phased Array UT, RT [Radiography Testing], and PT [Penetrant Testing]).

Similar welds on Unit 3 were inspected during Spring 2014 using the revised NDE-995 procedure. No rejectable weld indications requiring repair were identified.

2. Other welds inspected using NDE-995, "Ultrasonic Examination of Small Diameter Piping Butt Welds and Base Material for Thermal Fatigue Damage," were reviewed for those that resulted in limited coverage. These welds were inspected using PDI-UT-2 or by reviewing RT data, with no indications identified.

3. Welds were re-examined using the enhanced NDE-995 procedure in refueling outages since this event. During the thermal fatigue extent of condition examinations, rejectable indications were detected in the extrados of the 1 B2 Cold Page 2 of 3

Oconee Nuclear Station Revised Reply to Notice of Violation EA-14-091 Leg Drain elbow. The 1 B2 drain line elbow and adjacent butt weld developed cracking due to turbulent penetration thermal transient effects. The elbow was replaced.

4. Vibration data was evaluated for the HPI system on all three ONS units. Based on this review, the relatively high vibrations observed for the HPI lines during the Full Flow test appeared to be largest for the "B2" lines on all three units, with the 1 B2 line having the highest reported acceleration values of all 12 HPI Lines. Vibration levels were within acceptable limits, but the frequency of the ISI augmented examination (UT) was increased to every refueling outage (1 R) for Al and B2 HPI safe end-to-pipe butt welds on each unit (six total). These HPI lines have the highest vibration stresses.

5. Procedure NDE-995, "Ultrasonic Examination of Small Diameter Piping Butt Welds and Base Material for Thermal Fatigue Damage," was revised to incorporate the root cause lessons learned regarding application of appropriate probes and technology.

The procedure now includes guidance that weld crowns must be reduced to allow UT probes to traverse without loss of signal, specifies higher angle probes for one-sided examinations, and requires pre/post job briefs and brief content.

6. NDE procedures were revised to provide prescriptive guidance for maximizing examination coverage when performing augmented examinations, including entry into the corrective action program for evaluation by functional owner when limitations or indications of degradation are detected.

7. NDE procedure for Level III oversight of routine NDE examination activities was revised to utilize a "graded approach" relative to the significance of the NDE examination activity and operating experience.

(3) the corrective steps that will be taken, and Duke Energy will separate the Augmented Inspection portion of the ISI program from the ASME Section Xl portion so that the Augmented Inspection portion can function as an independent Engineering Program. This change is being tracked to completion in the corrective action program.

(4) the date when full compliance will be achieved.

Although additional actions as described above are ongoing, full compliance has been achieved. The 1B2 weld was repaired November 19, 2013, and post-repair RT was successfully completed on November 23, 2013. NDE-995 was revised. Comprehensive actions have been taken to prevent recurrence.

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