05000388/LER-2012-003, Regarding Unit 2, Automatic Reactor Scram While Performing Turbine Control Value Surveillance Testing

Regarding Unit 2, Automatic Reactor Scram While Performing Turbine Control Value Surveillance Testing

ML13046A080
Person / Time
Site:	Susquehanna
Issue date:	02/14/2013
From:	Helsel J Susquehanna
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
PLA-6974 LER 12-003-00
Download: ML13046A080 (5)

LER-2012-003, Regarding Unit 2, Automatic Reactor Scram While Performing Turbine Control Value Surveillance Testing

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 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)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(iii) 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)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(x)
LER closed by
IR 05000387/2013011 (18 November 2013) IR 05000387/2014008 (12 September 2014)
3882012003R00 - NRC Website

text

Jeffrey M. Helsel Nuclear Plant Manager U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 PPL Susquehanna, LLC 769 Salem Boulevard Berwick, PA 18603 Tel. 570.542.3510 Fax 570.542.1504 jmhelsel@ pplweb.com SUSQUEHANNA STEAM ELECTRIC STATION LICENSEE EVENT REPORT 50-388/2012-003-00 UNIT 2 LICENSE NO. NPF-22 PLA-6974 Docket No 50-388 Attached is Licensee Event Report (LER) 50-388/2012-003-00. On December 16, 2012, at approximately 0156 hours0.00181 days <br />0.0433 hours <br />2.579365e-4 weeks <br />5.9358e-5 months <br />, the Susquehanna Steam Electric Station (SSES) Unit 2 reactor automatically scrammed during the performance of quarterly Unit 2 main turbine control valve testing. This event was determined to be reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) for an event that resulted in the automatic actuation of the Reactor Protection System, Reactor Core Isolation Cooling and the High Pressure Coolant Injection system.

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

No commitments were identified in this submittal.

Attachment: LER 50-388/2012-003-00 Copy:

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

NRC FORM 366 (10-2010)

U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 LICENSEE EVENT REPORT (LER)

1. FACILITY NAME (See reverse for required number of digits/characters for each block)

Susquehanna Steam Electric Station Unit 2

4. TITLE

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

2. DOCKET NUMBER 05000388

3. PAGE 1 OF 4 Unit 2 Automatic Reactor Scram While Performing Turbine Control Valve Surveillance Testing

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH FACILITY NAME DOCKET NUMBER 05000 NUMBER NO.

DAY YEAR FACILITY NAME DOCKET NUMBER 12 16 2012 2012 - 003 -

00 02 14 2013 05000

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) 1 D 20.2201 (b)

D 20.2201 (d)

D 20.2203(a)(1)

D 20.2203(a)(2)(i) 1-1-0-. P_O_W_E_R-LE_V_E_L---40 20.2203(a)(2)(ii) 98o/o D 20.2203(a)(2)(iii)

D 20.2203(a)(2)(iv)

D 20.2203(a)(2)(v)

D 20.2203(a)(2)(vi)

D 20.2203(a)(3)(i)

D 20.2203(a)(3)(ii)

D 20.2203(a)(4)

D 50.36(c)(1 )(i)(A)

D 50.36(c)(1 )(ii)(A)

D 50.36(c)(2)

D 50.46(a)(3)(ii)

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

D 50.73(a)(2)(i)(B)

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

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

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

D 50.73(a)(2)(iii)

~ 50.73(a)(2)(iv)(A)

D 50.73(a)(2)(v)(A)

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

D 50.73(a)(2)(v)(C)

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

D 50.73(a)(2)(vii)

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

D 50.73(a)(2)(viii)(B)

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

D 50.73(a)(2)(x)

D 73.71 (a)(4)

D 73.71 (a)(5) 0 OTHER Specify in Abstract below or in NRC Form 366A

12. LICENSEE CONTACT FOR THIS LER Facility Name Brenda W. O'Rourke, Senior Engineer-Nuclear Regulatory Affairs

CAUSE

MANU-SYSTEM COMPONENT FACTURER REPORTABLE TO EPIX

14. SUPPLEMENTAL REPORT EXPECTED

~YES (If yes, complete 15. EXPECTED SUBMISSION DATE)

CAUSE

0 NO ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)

Telephone Number (Include Area Code)

(570) 542-1791 MANU-SYSTEM COMPONENT FACTURER

15. EXPECTED SUBMISSION DATE MONTH 05 REPORTABLE TO EPIX DAY YEAR 31 2013 On December 16, 2012, at approximately 0156 hours0.00181 days <br />0.0433 hours <br />2.579365e-4 weeks <br />5.9358e-5 months <br />, the Susquehanna Steam Electric Station (SSES) Unit 2 reactor automatically scrammed during the performance of quarterly channel functional test of the turbine control valve (CV) fast closure channels of the Reactor Protection System (RPS). Both the High Pressure Cooling Injection (HPCI) and Reactor Core Isolation Cooling (RCIC) systems automatically initiated and injected water into the reactor vessel. At approximately 0210 hours0.00243 days <br />0.0583 hours <br />3.472222e-4 weeks <br />7.9905e-5 months <br /> on December 16, 2012, a second reactor scram signal was received due to reactor water level lowering to+ 13 inches. This LER is being submitted in accordance with 10 CFR 50.73(a)(2)(iv)(A) for an event or condition that resulted in the automatic actuation of the RPS, and the HPCI and RCIC systems.

0156 Hours Scram: The probable direct cause of the unexpected Division 1 scram signal was due to a faulty subcomponent on the #1 Turbine CV. The as-found condition of one of the two 120VAC electrical connections to the #1 CV Fast Acting Solenoid Valve was not crimped properly. The root cause of the scram was SSES failed to incorporate industry best practices with other impacted work groups for half scram reduction. 0210 hours0.00243 days <br />0.0583 hours <br />3.472222e-4 weeks <br />7.9905e-5 months <br /> Scram: The cause of the second scram event is currently under investigation and will be reported in a supplement to this LER.

Completed corrective actions include: replacement of the Unit 1 CV #1 Fast Acting Solenoid Valve and Shutoff Valve and revision of Unit 1 and 2 quarterly turbine valve cycling surveillance procedures to require the use of an RPS test box. Planned corrective actions include: revise OE procedures to ensure condition reports are initiated when there is risk identified in OE that may impact SSES, and inspect all four Unit 1 Fast Acting Solenoid Valves for secure butt splice connections. There were no actual consequences to the health and safety of the public as a result of this event.

NRC FORM 366 (10-2010)

CONDITIONS PRIOR TO THE EVENT Unit 1 - Mode 1, 100 percent Rated Thermal Power Unit 2 - Mode 1, 98 percent Rated Thermal Power

EVENT DESCRIPTION

6. LER NUMBER YEAR I

SEQUENTIAL NUMBER 2012

--003--

I REVISION NUMBER 00

3. PAGE 20F4 On December 16, 2012, at approximately 0156 hours0.00181 days <br />0.0433 hours <br />2.579365e-4 weeks <br />5.9358e-5 months <br />, the Susquehanna Steam Electric Station (SSES)

Unit 2 reactor automatically scrammed during the performance of Technical Specification (TS) surveillance testing of the #2 turbine control valve (CV). The test being performed was the quarterly channel functional test of the turbine CV fast closure channels of the Reactor Protection System (RPS). At 0151 hours0.00175 days <br />0.0419 hours <br />2.496693e-4 weeks <br />5.74555e-5 months <br />, the #4 CV was tested and a Division 2 half-scram signal was received and cleared as expected. At 0153, CV #1 was tested, but the test was aborted due to nail meter glare. At 0153 hours0.00177 days <br />0.0425 hours <br />2.529762e-4 weeks <br />5.82165e-5 months <br />, the CV #1 tested was successfully completed. At 0155 hours0.00179 days <br />0.0431 hours <br />2.562831e-4 weeks <br />5.89775e-5 months <br />, during testing of the #2 CV, a RPS half-scram was received as expected (specifically, the 'B' channel, Division 2 of RPS). Prior to the Division 2 scram signal clearing, an unexpected momentary Division 1 ('A' channel of RPS) scram signal was also received from the CV #1 fast closure signal, resulting in a full RPS reactor scram.

All control rods fully inserted, with two control rods inserting beyond position "00" following reset of the reactor scram. Both reactor recirculation pumps tripped at -38 inches. All containment isolations occurred as expected. Both the High Pressure Cooling Injection (HPCI) and Reactor Core Isolation Cooling (RCIC) systems automatically initiated and injected water into the reactor vessel but were overridden by the control room operators once reactor water level was restored above the HPCI and RCIC initiation setpoints. The scram was reset to aid in preventing reactor vessel thermal stratification.

At approximately 0210 hours0.00243 days <br />0.0583 hours <br />3.472222e-4 weeks <br />7.9905e-5 months <br /> on December 16, 2012, a secondary scram occurred on low reactor water level

(+13 inches). No control rod motion occurred, as all rods were inserted.

There were no safety relief valve actuations or emergency diesel generator starts during the event. Reactor pressure was controlled via turbine bypass valve operation. There were no structures, systems, or components that were inoperable at the start of the event that contributed to this event.

In accordance with 10 CFR 50.72(b)(2)(iv)(A) and 10 CFR 50.72(b)(2)(iv)(B), on December 16, 2012, a 4-hour ENS notification (# 48598) was made to the NRC for an event or condition that results in Emergency Core Cooling Systems (ECCS) discharge into the reactor coolant system as a result of a valid signal, and any event or condition that results in the actuation of the RPS when the reactor is critical, respectively. This event was also reportable as an 8-hour notification in accordance with 10 CFR 50.72(b)(3)(iv)(A) for any event or condition that resulted in a valid actuation of the RPS, and the HPCI and RCIC systems.

This LER is being submitted in accordance with 10 CFR 50.73(a)(2)(iv)(A) for an event or condition that resulted in the automatic actuation of the RPS, and the HPCI and RCIC systems. (10-2010)

U.S. NUCLEAR REGULATORY COMMISSION

1. FACILITY NAME LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

2. DOCKET

6. LEA NUMBER YEAR NUMBER Susquehanna Steam Electric Station Unit 2 05000388 I

SEQUENTIAL 2012

--003--

CAUSE OF THE EVENT

Scram #1:

I REVISION NUMBER 00

3. PAGE 30F4 The probable direct cause of the unexpected Division 1 scram signal was due to a faulty subcomponent of the #1 Turbine CV. The as-found condition of one of the two 120VAC electrical connections to the #1 CV Fast Acting Solenoid Valve was not crimped properly. This would have resulted in a higher than normal connection resistance and subsequent less than designed power applied to the solenoid coil. Laboratory tests are expected to confirm this conclusion. PPL expects to have the results of the failure analysis by the end of February 2013.

The root cause of the event was that SSES failed to incorporate industry best practices with other impacted work groups (Operations) for half scram reduction. Specifically, Dresden OE (from 2000) regarding the station's success in reducing the number of half scram by using an RPS test box, and the 2005 Boiling Water Reactor Owners Group (BWROG) scram reduction effort, Recommendation #30 regarding the use of a test box to reduce RPS half-scram signals. An RPS test box allows testing of a scram contactor without actualizing the contactor and creating a half scram. SSES's evaluation of the above OE recommendations did not recognize the OE's applicability to operations surveillance test procedures.

The following two causal factor also contributed to the event:

Causal Factor 1 - Poor maintenance practices related to insulation stripping and connection crimping created resistance leading to less than designed power applied to the solenoid coil.

Causal Factor 2-Failure to incorporate GE SIL 226 (from 1977) recommendations for adequate wait time between testing into the SSES Quarterly Turbine Valve Cycling surveillance procedures.

Scram #2:

The cause of the second scram event is currently under investigation and will be reported in a supplement to this LER.

ANALYSIS I SAFETY SIGNIFICANCE Actual Consequences All control rods inserted and both reactor recirculation pumps tripped at -38 inches. HPCI and RCIC both automatically initiated as expected. No steam relief valves opened. (10-2010)

U.S. NUCLEAR REGULATORY COMMISSION

1. FACILITY NAME LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

2. DOCKET

6. LER NUMBER YEAR Susquehanna Steam Electric Station Unit 2 05000388 I

SEQUENTIAL NUMBER 2012

--003--

Potential Consequences I

REVISION NUMBER 00

3. PAGE 40F4 The Unit 2 risk significance and potential consequences for the initiating event experienced on December 16, 2012 due to an RPS automatic scram non-isolation event was less than 1 E-06 for Core Damage Probability (COP) and 1 E-07 for Large Early Release Probability (LERP) significance thresholds as defined in NRC Inspection Manual Chapter (IMC) 609. These thresholds represent a Green significance level which is of "Very Low Safety Significance."

In summary, there were no actual consequences to the health and safety of the public as a result of the event.

CORRECTIVE ACTIONS

Key Completed Actions Revised the Unit 1 and 2 Quarterly Turbine Valve Cycling surveillance procedures to require the use of an RPS test box when performing Main Turbine Control Valve Testing.

Replaced the Unit 1 CV #1 Fast Acting Solenoid Valve and Shutoff Valve.

Key Planned Corrective Actions Revise OE procedures to ensure condition reports are initiated when there is risk identified in OE that may impact SSES.

During the next Unit 1 outage, inspect all four Fast Acting Solenoid Valves (FASV) for secure butt splice connections.

Revise the Unit 1 and 2 Quarterly Turbine Valve Cycling surveillance procedures to require a 3-minute wait time between tests.

Revise MT-GE-01 0 sections 5.20 and 5.21 to incorporate industry accepted tug test to ensure connection is mechanically secure.

Evaluate additional Surveillance or Preventive Maintenance activities that do or could result in a half scram for use of a RPS Test Box.

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