05000364/LER-2012-001, Regarding TDAFW Pump Orifice Plate Thickness Results in Condition Prohibited by Technical Specifications
| ML12312A425 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 11/07/2012 |
| From: | Lynch T Southern Co, Southern Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NL-12-2091 LER 12-001-00 | |
| Download: ML12312A425 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(8) 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(8) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(8) 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3642012001R00 - NRC Website | |
text
Thomas A. lynch Southern Nuclear Vice President
- Farley Operating Company, Inc.
Farl ey Nucloar Plant Post Office Drawer 470 Ashford. Alabarna 36312 Tel 334.814.4511 Fax 3:J4.f) l !J.4728 November 7, 2012 SOUTHE COMPANY Docket Nos.: 50-364 NL-12-2091 U. S. Nuclear Regulatory Commission ATIN: Document Control Desk Washington, D. C. 20555-0001 Joseph M. Farley Nuclear Plant - Unit 2 Licensee Event Report 2012-001-00 TDAFW Orifice Plate Thickness Results in Condition Prohibited by Technical Specifications Ladies and Gentlemen:
In accordance with the requirements of 10CFR50.73 (a)(2)(i)(8), 1 OCFR50. 73 (a)(2)(ii)(8) and 10CFR50.73(a)(2)(v)(D) Southern Nuclear Operating Company hereby submits the enclosed Licensee Event Report. This letter contains no NRC commitments. If you have any questions, please contact Doug McKinney at (205) 992-5982.
Sincerely, T. A. Lynch Vice President - Farley TAULBHllac Enclosure: Unit 2 Licensee Event Report 2012-001-00
U. S. Nuclear Regulatory Commission NL-12-2091 Page 2 cc: Southern Nuclear Operating Company Mr. S. E. Kuczynski, Chairman, President &CEO Mr. D. G. Bost, Executive Vice President &Chief Nuclear Officer Mr. B. L. Ivey, Vice President - Regulatory Affairs Mr. B. J. Adams, Vice President - Fleet Operations Mr. M. A. Ajluni, Nuclear Licensing Director RTYPE: CFA04.054 U. S. Nuclear Regulatory Commission Mr. V. M. McCree, Regional Administrator Mr. A. E. Martin, NRR Project Manager - Farley Mr. E. L. Crowe, Senior Resident Inspector - Farley
Joseph M. Farley Nuclear Plant - Unit 2 Licensee Event Report 2012-01-00 TDAFW Orifice Plate Thickness Results in Condition Prohibited by Technical Specifications Enclosure Unit 2 Licensee Event Report 2012-001-00
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31 /2013 (10-2010) the NRC may not conduct or sponsor. and a person is not required to respond to. the information collection.
- 13. PAGE Joseph M. Farley Nuclear Plant, Unit 2 05000364 1 OF 4
- 4. TITLE TDAFW Pump Orifice Plate Thickness Results in Condition Prohibited by Technical Specifications
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL NUMBER REV NO.
MONTH DAY YEAR FACILITY NAME DOCKET NUMBER FACILITY NAME DOCKET NUMBER 09 12 2012 2012 - 001 - 00 11 07 2012
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check al/ that apply) o 20.2201 (b) o 20.2203(a)(3)(i)
D 50.73(a)(2)(i)(C) o 50.73(a)(2)(vii) 1 o 20.2201 (d) o 20.2203(a)(3)(ii)
D 50.73(a)(2)(ii)(A) o 50.73(a)(2)(viii)(A) o 20.2203(a)(1) o 20.2203(a)(4)
~ 50.73(a)(2)(ii)(8) o 50.73(a)(2)(viii)(B) o 20.2203(a)(2)(i) o 50.36(c)(1 )(i)(A)
D 50.73(a)(2)(iii) o 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL IJ 20.2203(a)(2)(ii) o 50.36(c)(1 )(ii)(A)
D 50.73(a)(2)(iv)(A) o 50.73(a)(2)(x) o 20.2203(a)(2)(iii) o 50.36(c)(2)
D 50.73(a)(2)(v)(A)
D 73.71(a)(4) o 20.2203(a)(2)(iv) o 50.46(a)(3)(ii)
D 50.73(a)(2)(v)(8)
D 73.71 (a)(5) 100 o 20.2203(a)(2)(v) o 50.73(a)(2)(i)(A)
D 50.73(a)(2)(v)(C)
D OTHER D 20.2203(a)(2)(vi)
~ 50.73(a)(2)(i)(B)
~ 50.73(a)(2)(v)(O)
Specify in Abstract below or in Since the 1/8 inch orifice plates have been in place for the life of the plant, this represents a condition prohibited by Technical Specifications and is reportable under 10CFR50.73(a)(2)(i)(B).
This condition is additionally reportable as an unanalyzed condition that degraded plant safety under 1 OCFR50. 73(a)(2)(ii)(8) and as a condition that could have prevented the fulfillment of a safety function under 1 OCFR50. 73(a)(2)(v)(D).
The Unit 2 TDAFW orifice plates will be replaced during the spring 2013 Unit 2 refueling outage and will be inspected or tested as deemed appropriate. As determined by the results of the inspections/testing, this LER will be supplemented or retracted accordingly.
Cause of Event
The inadequate orifice plate thickness is considered a latent construction issue. Two design changes were issued during original plant construction that required installation of adequately sized flow orifices. For undetermined reasons, the replacement of the 1/8 inch thick orifice plates as required by the design changes did not occur. Therefore, the direct cause of the event was the failure to correctly implement these two design changes during plant construction.
Research of plant construction documentation was unable to identify reasons for the failure to implement the design changes.
Safety Assessment
An Engineering analysis of design basis events with an assumed failure of the installed 1/8 inch thick TDAFW flow orifice plates has determined that during a main steam line break or a main feed water line break event with successful injection from both MDAFW pumps, there would be adequate AFW flow to the intact steam generators. It can be noted however that under these conditions, the TDAFW Pump would operate in a run-out condition, and if one of the two MDAFW Pumps were out of service or failed during either of these two events, then minimum required flow would not be achieved. This analysis of potential impact on TDAFW pump flow does not consider the ability of the control room operator to modulate TDAFW pump speed and TDAFW flow control valve position to avoid or mitigate runout if necessary. 1\\10 other design basis accidents were impacted by the non-conforming Unit 2 TDAFW orifice plates.
Additionally, SNC Risk Informed Engineering (RIE) conducted a risk evaluation of the impact at Farley Unit 2 of secondary side break (Le. main steam line break and main feedwater line break) events. The evaluation assumed failure of the TDAFW pump due to run-out for these events. It was further assumed that successful mitigation required injection flow from 2 of 2 MDAFW pumps. The current Farley Unit 2 average risk model (Revision 9, Version 2) that considers only hazards from internal events and internal flooding was used. Based on the results of this risk evaluation, it was concluded that the potential increase in risk resulting from the smaller plate thickness is considered "very small" in accordance with the acceptance guidelines in Regulatory Guide 1.174 for increases in CDF and LERF (i.e., less than 1 E-06 and 1 E-07 per reactor year, respectively).
The non-conformance to design specifications of the Unit 2 TDAFW orifice plates with respect to plate thickness had no actual adverse effect on the safety and health of the public since there has been no occurrence of accident conditions involving a main steam line break or a main feed water line break.
Corrective Action
To restore the Unit 2 TDAFW Pump to operable status Temporary Modification SNC429958 was implemented within the time limit of Technical Specification 3.7.5 condition B to limit the maximum TDAFW orifice through-flow and resultant pressure differential across the orifice plate to an acceptable value.
To restore the Unit 2 TDAFW flow orifices to within design specifications, the orifice plates are scheduled for replacement with plates meeting design thickness criterion during the Unit 2 spring 2013 refueling outage. The Unit 2 MDAFW flow orifice plates (whose non-conformance to design specifications did not make the motor driven sUb-system inoperable) are likewise scheduled for replacement with plates meeting design thickness criterion during the Unit 2 spring 2013 refueling outage.
Industry Operating Experience (OE) on the event has been issued.
Additional Information
No similar events were discovered.