05000387/LER-2013-001, Regarding Diesel Generator B to Bus 2B Synchronizing Selector Switch Failure

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Regarding Diesel Generator B to Bus 2B Synchronizing Selector Switch Failure
ML13190A104
Person / Time
Site: Susquehanna  Talen Energy icon.png
Issue date: 07/08/2013
From: Franke J
Susquehanna
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
PLA-7041 LER 13-001-00
Download: ML13190A104 (6)
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LER-2013-001, Regarding Diesel Generator B to Bus 2B Synchronizing Selector Switch Failure
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
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)(B), Unanalyzed Condition
10 CFR 50.73(a)(2)(iii)
10 CFR 50.73(a)(2)(ix)(A)
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)(B), Loss of Safety Function - Remove Residual Heat
10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown
10 CFR 50.73(a)(2)(v), Loss of Safety Function
3872013001R00 - NRC Website
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text

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I Jon A. Franke Site Vice President PPL Susquehanna, LLC 769 Salem Boulevard Berwick, PA 18603 Tel. 570.542.2904 Fax 570.542.1504 jfranke@pplweb.com I

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U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 SUSQUEHANNA STEAM ELECTRIC STATION (SSES)

LICENSEE EVENT REPORT 50-387/2013-001-00 LICENSE NOS NPF-14 and NPF-22 PLA-7041 Docket Nos. 50-387 and 50-388 Attached is Licensee Event Report (LER) 50-387/2013-001-00. This LER is submitted to report a condition in which the SSES Diesel Generator (DIG) 'B' to 4.16 kV bus '2B' synchronizing selector switch failed. This resulted in a condition that is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as any operation or condition which was prohibited by the SSES Technical Specifications (TS).

There were no actual consequences to the health and safety of the public as a result of this event.

There are no regulatory commitments associated with this LER.

Attachment: LER 50-387/2013-001-00 Copy:

NRC Region I Mr. P. W. Finney, NRC Sr. Resident Inspector Mr. J. A. Whited, NRC Project Manager Mr. L. J. Winker, PA DEP/BRP TM

NRC FORM 366 U.S. NUCLEAR REGULATORY APPROVED BY OMB: NO. 3150-0104 EXPIRES:1 0/31/2013 (10-2010)

COMMISSION

, the NRC digits/characters for each block) may not conduct or sponsor, and a person is not required to respond to, the information collection.

3. PAGE Susquehanna Steam Electric Station (SSES) Unit 1 05000387 1 OF 5

~-TITLE: Diesel Generator '8' to Bus '28' Synchronizing Selector Switch Failure

5. EVENT DATE
6. LER NUMBER
7. REPORT DATE
8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.

MONTH DAY YEAR 05000 6~

FACILITY NAME DOCKET NUMBER 05 07 2013 2013

- 001
- 01 ()7 2013 Susquehanna Steam Electric Station Unit 2 05000388
9. OPERATING MODE
11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)

Unit 1 -1 D 20.2201(b)

D 20.2203(a)(3)(i)

D 50.73(a)(2)(i)(C)

D 50.73(a)(2)(vii)

Unit 2-5 D 20.2201 (d)

D 20.2203(a)(3)(ii)

D 50.73(a)(2)(ii)(A)

D 50.73(a)(2)(viii)(A)

D 20.2203(a)(1)

D 20.2203(a)(4)

D 50.73(a)(2)(ii)(B)

D 50. 73(a)(2)(viii)(B)

10. POWER LEVEL D 20.2203(a)(2)(i)

D 50.36(c)(1)(i)(A) 0 50.73(a)(2)(iii)

D 50.73(a)(2)(ix)(A)

Unit 1 -100%

D 20.2203(a)(2)(ii)

D 50.36(c)(1 )(ii)(A) 0 50. 73(a)(2)(iv)(A)

D 50.73(a)(2)(x)

D 20.2203(a)(2)(iii)

D 50.36(c)(2) 0 50.73(a)(2)(v)(A)

D 73.71{a)(4)

Unit 2-0%

D 20.2203(a)(2)(iv)

D 50.46(a)(3)(ii)

D 50.73(a)(2)(v)(B)

D 73.71(a)(5)

D 20.2203(a)(2)(v)

D 50.73(a)(2)(i)(A)

D 50.73(a)(2)(v)(C) 0 OTHER 0 20.2203{a)(2)(vi)

~ 50.73(a)(2)(i)(B) 0 50. 73(a)(2)(v)(D)

Specify in Abstract below or in Sequence of Events The following is a summary of the events related to this reportable condition:

3. PAGE 30F5
  • 5/7/2013 00:40 While performing S0-024-001 B, the synch switch for Unit 2B ESS bus HS-00040B appears to have failed in the synch position. CR 1700407 written to document this failure.
  • 5/7/2013 00:53 Synchronizing Select Switch DG B to Bus 2B is determined to be broken in the closed position, the synchronizing scope will not work for any other busses. Use of any other synchronizing selector switch will cause the fuse to blow.
  • 5/7/2013 00:56 CR 1706404 written to identify that the synchronizing circuit at Susquehanna needs to be reviewed in accordance with NDAP-QA-0524 for Failure Effect Codes and Single Point Vulnerability mitigation.
  • 5/7/2013 15:48 CR 1700812 written to evaluate an engineering change to electrically jumper out the synch switch for breaker 2A20204 (HS-00040B) from the circuit to allow all other synch switches to function.
  • 5/7/2013 PCWO 1700528 written to determinate I remove the defective synchronizing selector switch from control room panel OC653. PCWO 1700647 written to replace synchronizing selector switch HS-00040B on panel OC653.
  • 5/8/2013 18:10 Power supply de-energized for synchronizing selector switch replacement
  • 5/9/2013 13:17 Completed replacement of HS-00040B DG B to Bus 2B Synchronizing Selector Switch on Panel OC653 under WO 170064 7
  • 5/14/2013 03:55 The SSES NRC Senior Resident requested clarification related to compliance with the TS SR 3.8.16 surveillance requirement for the HS-00040B DG B to Bus 2B Synchronizing Selector Switch failure (documented in CR1703293) The TS Bases for SR 3.8.1.16 states: "As required by Regulatory Guide 1.9 (Ref. 3), this Surveillance ensures that the manual synchronization and automatic load transfer from the DG to the offsite source can be made and that the DG can be returned to ready to load status when offsite power is restored. It also ensures that the auto start logic is reset to allow the DG to reload if a subsequent loss of offsite power occurs. The DG is considered to be in ready to load status when the DG is at rated speed and voltage, the DG controls are in isochronous and the output breaker is open.
  • 5/28/2013 16:58 CR 1708912 was written to identify that the condition prohibited by Unit 2 TS 3. 8.2 involved OPDRVs. Specifically, LCO 3.8.2 required action A.2.3 to immediately initiate actions to suspend OPDRVs was not followed on Unit 2. As a result, enforcement discretion criteria item 4 of EGM 11-003, Revision 1 was not met because TS Action requirement for Mode 5 OPDRV activities were not followed as required by criteria item 4 for approximately 75 hours8.680556e-4 days <br />0.0208 hours <br />1.240079e-4 weeks <br />2.85375e-5 months <br />. Because criteria item 4 was not met, enforcement discretion under EGM 11-003 was not applicable to any OPDRV activities that were performed while LCO 3.8.2 required action A.2.3 was not met.

CAUSE OF THE EVENT

The Direct Cause of the event was a failure of the DIG 'B' to bus '28' synchonizing selector switch (HS-000408) which failed in the 'on' position during performance of S0-024-001 B "Monthly Diesel Generator B Operability Test.

The Apparent Cause determined thus far was that Surveillance Procedure S0-024-001 B did not provide guidance that the synchronizing selector switch is required to meet the TS SR 3.8.1.16 surveillance requirements. A Causal Factor was determined to be that the SRO review was limited to the TS surveillance requirements of S0-024-001 B. It was not recognized that operation of the synchronizing selector switch was necessary to meet the SR 3.8.1.16 requirement which is met by performing Engineering Surveillance SE-1(2)24-1(2)07 "LOCA LOOP TESTING" on a two year frequency. Consequently, this SR is not frequently reviewed and exercised. Recent Operability Determination Training did not emphasize that SRO's are expected to be aware of the content of TS and SRs. The full extent of SRs not met on both Units 1 and 2 is currently under evaluation and will be provided as a supplement to this LER.

ANALYSIS/SAFETY SIGNIFICANCE

Actual Consequences:

There were no actual consequences to the health and safety of the public as a result of this event. The broken synchronizing selector switch caused a TS SR to not be met, which resulted in Unit 1 LCO 3.8.1 and Unit 2 LCO 3.8.2 to not be met. At no time were the A, B, C, or D required D/Gs not capable of performing their safety function to automatically start and load to the Emergency Safety Switchgear (ESS) busses.

Additionally, at no time were either of the offsite power sources unable to supply their connected loads or automatically transfer from the preferred to the alternate source or vice versa if necessary. The switch failure only affected restoration of power following a 'loss of offsite power' (LOOP), in which the offsite power source would not be able to re-synchronize to the ESS busses with the loads remaining connected to the D/Gs.

Since the inoperable AC power sources were determined to have maintained their ability to perform their necessary shutdown risk function, the impact to OPDRV activities was determined to be of low shutdown risk significance and an adequate level of safety was provided during the performance of the OPDRV activities described in Unit 2 LER 50-388/2013-001-00 (PLA-7018, dated June 14, 2013).

Potential Consequences:

In the event of a LOOP Ooffsite power could not have been re-synchronized to the running loads on the ESS busses without repair of the broken synchronizing selector switch or its isolation from the circuit.

CORRECTIVE ACTIONS

6. LERNUMBER I

SEQUENTIAL NUMBER

- 001 An immediate corrective action was to replace the failed synchronizing selector switch.

Longer term corrective actions planned thus far:

j REVISION NUMBER

- 00
3. PAGE 50F5
  • Revise the affected surveillance procedures to provide guidance that the synchronizing selector switch is required to meet the surveillance requirements of SR 3.8.1.16.
  • Reclassify all existing synchronizing switches to have the same failure effect and maintenance rule codes, which will establish an equal criticality for all switches.
  • Create a maintenance plan to change out the switches to improve reliability.
  • Evaluate the feasibility of synchronizing circuit design changes.
  • Perform a sampling of surveillances that would lead to a 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> LCO if the surveillance failed, to ensure that there are sufficient directions in procedures to alert Operators when performing the TS review.
  • Submit an IN PO Operating Experience Report for this event.

PREVIOUS SIMILAR EVENTS

No previous similar events in which a single point vulnerability equipment failure resulted in a condition prohibited by TS on both SSES Units were identified.

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