05000414/LER-2007-001

LER-2007-001, Failure to Comply with Action Statement in Technical Specification (TS) 3.3.1 for Loss of a Channel of the Solid State Protection System

Docket Number
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
4142007001R00 - NRC Website

BACKGROUND

This report is required per 10CFR50.73(a)(2)(i)(B). The unit operated in a condition prohibited by the Technical Specifications when the channel [EIIS: CHA] 4 axial flux imbalance input to the OTDT setpoint failed and the required actions were not completed within the completion time limits.

Catawba Nuclear Station (CNS) Unit 2 is a Westinghouse four-loop pressurized water reactor [EIIS: RCT]. Each OTDT channel calculates a reactor trip setpoint based on inputs from primary system pressure, coolant temperature, and axial flux difference. When reactor power exceeds the OTDT trip setpoint on two-out-of-four OTDT channels, a reactor trip signal is generated. The OTDT trip signal provides additional plant protection from departure from nucleate boiling (DNB) conditions.

At the time of this event, Unit 2 was in Mode 1 at 100% rated thermal power. Other than the conditions described herein, there was no inoperable equipment that contributed to the occurrence of this event.

EVENT DESCRIPTION

(Dates and times are approximate) 5/10/07� Unit 2 B-train solid state protection system 0500 (SSPS) [EIIS: JF] 48VDC power supply (PS-2) failed. This power supply is one of two redundant power supplies in the 2B SSPS Logic Bay.

5/10/07 A Complex Activity Plan was developed to replace the failed power supply.

5/10/07 Unit 2 SSPS B Train was placed in "Test" Mode 20:50 5/10/07 While executing the Complex Activity Plan, an 2149 unexpected annunciator 2AD2/F-7, "PSC Cabinet 4 Power Supply Failure", came into and remained in alarm when an arc occurred during the insertion of a fuse on the newly installed power supply.

This window illuminates when either the primary or back-up 7300 power supplies drop below the under-voltage setpoint, a card frame fuse opens, a short-circuit conditions exists on a NAL card, or the loss of power on an individual 7300 circuit card.

Maintenance personnel performed a visual inspection for circuit card failures in 2PCC4 immediately after the alarm and found no apparent cause of the alarm. Also, the control board indications did not show any unusual or failed instrumentation. Maintenance personnel discussed the possible causes of the alarm with Operations and Engineering. Due to the Complex Activity of the power supply replacement in progress, it was decided that the conservative action would be to stop all intrusive troubleshooting on the panels until dayshift.

Since it was concluded that the probable cause of the alarm was an annunciator card failure, an opportunity for further troubleshooting and diagnosis of the problem in a timely manner was missed.

5/11/07 Unit 2 SSPS B Train was returned to Normal.

0004 5/11/07 During follow-up investigation of the channel 4 0840 alarm, a 7300 circuit card for the OTDT setpoint in 2PCC4 was discovered failed. The card provides the axial flux imbalance penalty to the OTDT trip setpoint. Since the actual plant conditions did not require any axial flux setpoint penalty, the card failure did not affect the currently required trip setpoint.

However, for a postulated transient that might create an axial flux penalty, the channel 4 OTDT trip setpoint could have been non­ conservative.

The Technical Specification Required Action statement was immediately entered. The required action is to place the channel in the trip condition within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> or be in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

5/11/07 OTDT channel 4 placed in the trip condition.

1050 The OTDT channel 4 failure likely existed at 2149 on 5/10/7 when the annuciator alarmed. The time duration from the initial alarm until the channel was placed in the trip condition was 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />, 1 minute.

5/11/07 The card was replaced and LCO exited.

1911

CAUSAL FACTORS

The Apparent Cause is Human Error. The error occurred when the technician failed to notice the LED extinguished on the OTDT card C4­ 232 in 2PCC4. This individual failed to identify the failure of the card C4-232 NCH. Individual card light-emitting-diodes (LEDs) provide indication of normal card power supply and this indication was overlooked for one card mounted in a cabinet among approximately 100 similar cards. Each LED is approximately 5/32 of an inch in diameter.

CORRECTIVE ACTIONS

Immediate:

1. The failed OTDT channel was placed in the trip condition.

Subsequent:

1 The failed circuit card was replaced. Following card replacement the channel was tested, verified operable, and returned to service at 1911 on 5/11/07.

2. Operations and Maintenance departments have communicated this event to the organizations to be used as Operating Experience (OE) and as lessons learned.

Planned:

1.The annunciator response procedure will be revised to require the issuance of a model work order to troubleshoot the 7300 cabinets, when required.

2.A model work order for troubleshooting the 7300 cabinets will be developed with guidance including steps requiring peer checks for error-likely situations.

There are no NRC commitments contained in this LER.

SAFETY ANALYSIS

The OTDT reactor trip setpoint is designed to protect the reactor from departure from nucleate boiling (DNB) conditions by calculating a trip setpoint based on pressurizer pressure, reactor coolant system temperature, and axial power distribution. When two of the four OTDT channels actuate, a reactor trip signal is generated.

Reactor trips and turbine trips are analyzed In Chapter 15 of the Catawba Nuclear Station Updated Final Safety Analysis Report (UFSAR) and remain the bounding analyses for the out of service OTDT channel.

The OTDT channels are not modeled explicitly in the Probabilistic Risk Analysis (PRA) because of the redundancy of the system. The only function adversely affected during the 'time period of interest was the Unit 2, Channel 4 axial flux input to the OTDT function. With the axial flux input functional unit inoperable, the OTDT function for Channel 4 was degraded. However, at 100% power the axial flux input would be zero and the other inputs to Channel 4 OTDT remained operable and would have responded if called upon.

Thus, the reliability of the OTDT function was degraded, but the remaining OTDT trip logic was operable and if needed would have tripped the reactor, when required. During the 13 hour1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> and 1 minute time period of interest, additional multiple failures would have been required such that an OTDT reactor trip, if required, would not actuate.

Additionally, other reactor trip instrumentation systems, for example overpower delta temperature (OPDT) (which also protects the reactor against DNB conditions), as well as pressurizer high pressure, pressurizer high water level, and steam generator low-low water level, were available, if needed, during the time period of interest to trip the reactor. The failure of two or more reactor trip functions is considered probabilistically insignificant.

The dominant core damage sequences in Catawba PRA, Rev 3a associated with a reactor or turbine trip involve loss of secondary side heat removal and failure of feed and bleed cooling. The dominant large early release frequency sequences for Catawba involve Inter-system Loss of Coolant Accidents (ISLOCA) and seismic initiated sequences not reactor trip initiators.

Equipment to mitigate these and other events were available and functional during the time period of interest. Train A SSPS Was operable and while the Train B SSPS automatic function was not available for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and 15 minutes during the 13 hour1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> 1 minute period of interest individual manual start capability of Train B equipment was not impacted.

Therefore, due to the redundancy of the OTDT system, the availability of other reactor trip instrumentation, the availability of plant equipment needed to mitigate a reactor trip and other transients including important containment safeguards systems (i.e. containment spray [EIIS: BE] and hydrogen mitigation [EIIS: BB]), and the small probability of having an initiating event during the time period the OTDT channel was inoperable, the conditional core damage probability during the 13 hour1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> and 1 minute time period of interest is considered negligible. Similarly, the conditional large early release probability for the 13 hour1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> and 1 minute time period of interest is considered negligible.

This event was of no significance with respect to the health and safety of the public.

ADDITIONAL INFORMATION

Within the last three years, there have not been any previous similar occurrences at Catawba. Therefore, this event was determined to be non-recurring in nature.

Energy Industry Identification System (EIIS) codes are identified in the text as [EIIS: XX]. There are no EPIX reportable equipment failures associated with this report.

This event did not involve a Safety System Functional Failure.

There were no releases of radioactive materials, radiation exposures, or personnel injuries associated with this event.

UFSAR Revision? (Y/N) 1111 (Required to satisfy RG 1.70, 10 CFR 50.34 (b) or 10 CFR 50.71(e)?) Submittal Lead Name A. p, lef Phone 3 7 2— Content Development (Attach additional information as needed) Contributor-Name/Site Scope/extent of Contribution or Portion Contributed Individual Review (Attach additional information as needed) Reviewer Name/Site - Signature Portions or Subjects Reviewed and Nature of Review Date 4 — Carl/A fe5&-E Po R_c_ a...e.ve.,.., C......, s".75.- A4 oz6ked 'PIP eDi--034108 --- Cf 14 5 fr: c tIA,W L,Ele�(2crr i 1%A,, Checker (Attach additional information as needed) :Checker Name/Site Signature, Validation of Entire Document Date . .

Manager Approval (Attach additional information as needed) Manager/Group Signature Specific Portions or Subjects Approved Date.

Regulatory Review Reviewer , Name

• Signature ' Nature of Review Date ..,. . 10/0/04._ Submittal Lead he ...14.esk, e-Hrlad b Devote* r 'A/0-7 RGC Function Manager i

• l

• 1/10/0-)if D 14'4+ g OAP— SA Manager Tr.k.kkm■L.100,4mon1.4-10-..../A-- ENTIRE -3 It Oes.anCt.zr 1110101 Site Vice President Legal Dept. Review Name Signature Nature of Review Date This completed form must be presented with the original submittal for signature. The form may be filled in with reference to emailed information in place of actual signatures and required information so long as the emailed information is maintained with the copy of this form that is sent to Master file and ELL

VERIFY HARD COPY AGAINST WEB SITE IMMEDIATELY PRIOR TO EACH USE

Problem Investigation Process Catawba Nuclear Station FIRSerial No:�ActiOn Category:�"LER No:,� Other Report: - C-07-03408 4 Problem Identification �Discovered Time/Date: 16:32 07/05/2007�Occurred Time/Date:

Unit(s) Affected:

Unit�Mode�%Power Unit Status Remarks 2 N/A 100�n/a System(s) Affected:

N/A� Not Applicable to Any System Affected Equipment (No Equipment Affected) Location of Problem:

Bldg:� Column Line:� Elev:

Location Remarks:

Method Used to Discover Problem:

Brief Problem Description:

PORC Meeting on 7/5/07 - Failure to Comply with Action Statement in TS 3.3.1 for loss of a Channel of Solid State Protection System Detail Problem Description:

A PORC meeting was held on 7/5/07 concerning the Failure to Comply with Action Statement in TS 3.3.1 for loss of a Channel of Solid State Protection System. The following corrective actions were identified during meeting:

All corrective actions from the PORC are to be resolved by RCG 1. LER Section 5, Event Date - correct date from 10th to I I th.

2. LER Section 13 - Decide if reportable to EPIX. If it revise paragraph on last page of the document.

3. LER Section 16 LER, Abstract section - Revise the second sentence for clarity of meaning.

4. LER Section 16, Event Description section - Add statement that SSPS B Train was placed in test and include the time. Also add a statement that SSPS B Train was returned to normal conditions.

5. LER Section 16, Event Description section, 2149 timeframe - add information describing why the annunciator alarm was not diagnosed correctly.

6. LER Section 16, Event Description section, 2149 timeframe - Revise the 3rd paragraph to include Operations interfacing with Maintenance and Engineering.

7. LER Section 16, Causal Factors section - Remove the word critical in the second sentence, and the words acting alone in the third sentence.

8. LER Section 16, Corrective Action section, Subsequent - change time for 1914 to 1911.

9. LER Section 16, Corrective Action section, Planned, 1 - Maintenance and Operation will have completed their operating experience communications about the event with their groups prior to the LER being sent to the NRC. Revise wording to reflect this.

10. LER Section 16, Safety Analysis section - Revise the third paragraph to better reflect the state of the OTdT function and what indications were available to Operations.

11. LER Section 16, Safety Analysis section - In the sixth paragraph, verify that the 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and 15 minutes time is correct.

12. Last page of the document, check the numbering of pages.

The PORC members unanimously approved the LER with the condition that all corrective actions are resolved. The revised LER, will be reviewed by the SRG Manager for final approval.

� 07/10/2007 07:05 Page 1� PIP No: C-07-03408 Problem Investigation Process Catawba Nuclear Station Originated By: GTM7337: MODE, GERALD T Team: PAM7334 Group: C-SRG Date: 07/05/2007 Other Units/Components/Systems/Areas Affected(Y,N,U): N Industry Plants Affected(Y,N,U): U

Immediate Corrective Actions:

Immediate Corrective Action Documents / Work Orders:

� �Indiv� Team Group Date � Problem Identified By:�GTM7337�PAM7334 C-SRG�07/05/2007 Problem Entered By: GTM7337 PAM7334 C-SRG 07/05/2007 Screening � Action Category: 4 Root Cause performed? No OEP No:

Other Report Nos:

Event Codes:

013 PORC Y9�Safety Assurance Screening Remarks:

Screened by the Centralized Screening Team on July 9, 2007. No changes were made to the original screening.

Last Updated By: RSP5945: PURSLEY, R STEVE Team: PAM7334 Group: C-SRG Date: 07/09/2007 Originated By: GTM7337: MODE, GERALD T Team: PAM7334 Group: C-SRG Date: 07/05/2007 Assignments:

Responsible Groups(s) for Problem Evaluation: Responsible Group for Present Operability:

�N/A Responsible Group for Report Support Info:�N/A Responsible Group for Repot/ability:�N/A Responsible Group for Overall PIP Approval:�C-MGT Sighatufe�

• I ndly� .Team� Group �Date Screened By: RSP5945� PAM7334� C-SRG�07/09/2007 Present Operability �Responsible Group: Status:

Sys/Comp Operable? (Y,N,C,E,T):

Required Mode:

07/10/2007 07:05� Page 2� PIP No: C-07-03408 Problem Investigation Process Catawba Nuclear Station Comments:

No Current Signatures For This Section Reportability �Responsible Group: Status:

Problem Reportable(Y,N,E):

Reportable Per:

Comments:

No Current Signatures For This Section Investigation Report:

Responsible Group:� Act Date:

Investigator:� Group:

Due Date:

Date Due to VP or Sta. Mgr:

Date Regulatory or Agency Rpt Due:

Date Investigation Report Approved:

NRC Cause Codes:

Report Support Info:

Responsible Group:� Status:

No Current Signatures For This Section Problem Evaluation

Cause:

'Event Desdription Primary�; Causing GroupsCode� Problem Evaluation From:�N/A

Corrective Actions

CA Seq. No: 1

• ReSp croup "�Status� Orig Group�Everit:COde � Prop CAC.:�—Cause COde..

C-RGC� Closed C-SRG� 013 Proposed Corrective Action:

All corrective actions from the PORC are to be resolved by RCG.

I.

� LER Section 5, Event Date - correct date from 10th to 1 lth.

2. LER Section 13 - Decide if reportable to EPIX. If it revise paragraph on last page of the document.

3. LER Section 16 LER, Abstract section - Revise the second sentence for clarity of meaning.

07/10/2007 07:05 � Page 3� PIP No: C-07-03408 Problem Investigation Process Catawba Nuclear Station 4. LER Section 16, Event Description section - Add statement that SSPS B Train was placed in test and include the time. Also add a statement that SSPS B Train was returned to normal conditions.

5. LER Section l 6, Event Description section, 2149 timeframe - add information describing why the annunciator alarm was not diagnosed correctly.

6. LER Section 16, Event Description section, 2149 timeframe - Revise the 3rd paragraph to include Operations interfacing with Maintenance and Engineering.

7. LER Section 16, Causal Factors section - Remove the word critical in the second sentence, and the words acting alone in the third sentence.

8. LER Section 16, Corrective Action section, Subsequent - change time for 1914 to 1911.

9. LER Section 16, Corrective Action section, Planned, 1 - Maintenance and Operation will have completed their operating experience communications about the event with their groups prior to the LER being sent to the NRC. Revise wording to reflect this.

10. LER Section 16, Safety Analysis section - Revise the third paragraph to better reflect the state of the OTdT function and what indications were available to Operations.

11. LER Section 16, Safety Analysis section - In the sixth paragraph, verify that the 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and 15 minutes time is correct.

12. Last page of the document, check the numbering of pages.

Originated By: GTM7337: MODE, GERALD T Team: PAM7334 Group: C-SRG Date: 07/05/2007 Signature Type It-0v� , Team , Group - Date Ready For Approval: GTM7337 PAM7334 C-SRG 07/05/2007 Approval Assigned To: PAM7334 PAM7334 C-SRG 07/05/2007 Approved By: GTM7337 PAM7334 C-SRG 07/05/2007 �General:Outage: Mode:

Other Tracking Processes Type� Number Text Actual Corrective Action:

�Priority: N � Actual CAC: A2� Status: Closed Due Date: 07/19/2007 Resolution of PORC CAC's on 7300 Card Failure LER 414/07-001:

1.LER Section 5, Event Date - correct date from 10th to llth.

The event date has been changed to the 11th or May 2007 since the failure to comply with the TS action statement actually occurred on the 11th.

2. LER Section 13 - Decide if reportable to EPIX. If it revise paragraph on last page of the document.

This is not reportable under EPIX, however, the Section 13 information on the form was completed with a "No" answer and this information was repeated on the last page of the document.

3. LER Section 16 LER, Abstract section - Revise the second sentence for clarity of meaning.

The second sentence was revised to state: However, for the plant conditions that existed at that time, the OTdT channel was not recognized as being inoperable using normal control room board indications.

4. LER Section 16, Event Description section - Add statement that SSPS B Train was placed in test and include the time. Also add a statement that SSPS B Train was returned to normal conditions.

The following statements were added to the time line:

5/10/07 20:50� Unit 2 SSPS B Train was placed in "Test" Mode 5/11/07 0004� Unit 2 SSPS B Train was returned to Normal.

07/10/2007 07:05� Page 4� PIP No: C-07-03408 Problem Investigation Process Catawba Nuclear Station These dates and times were obtained from TSAIL.

5. LER Section 16, Event Description section, 2149 timeframe - add information describing why the annunciator alarm was not diagnosed correctly.

The final paragraph is shown below:

Maintenance personnel performed a visual inspection for circuit card failures in 2PCC4 immediately after the alarm and found no apparent cause of the alarm. Also, the control board indications did not show any unusual or failed instrumentation. Maintenance personnel discussed the possible causes of the alarm with Operations and Engineering. Due to the Complex Activity of the power supply replacement in progress, it was decided that the conservative action would be to be to stop all intrusive troubleshooting on the panels until dayshift. Since it was concluded that the probable cause of the alarm was an annunciator card failure, an opportunity for further troubleshooting and diagnosis of the problem in a timely manner was missed.

6. LER Section 16, Event Description section, 2149 timeframe - Revise the 3rd paragraph to include Operations interfacing with Maintenance and Engineering.� ' See the rewritten paragraph above.

7. LER Section 16, Causal Factors section - Remove the word critical in the second sentence, and the words acting alone in the third sentence.

The sentences were revised to read:

The error occurred when the technician failed to notice the LED extinguished on the OTDT card C4-232 in 2PCC4. This individual failed to identify the failure of the card C4-232 NCH.

8. LER Section 16, Corrective Action section, Subsequent - change time for 1914 to 1911.

1911 was verified to be the correct time via TSAIL entry C2-07-01099.

9. .� LER Section 16, Corrective Action section, Planned, 1 - Maintenance and Operation will have completed their operating experience communications about the event with their groups prior to the LER being sent to the NRC. Revise wording to reflect this.

The PLANNED RESPONSE SECTION now reads:

1.� Operations and Maintenance departments have communicated this event to the organizations to be used as Operating Experience (OE) and as lessons learned.

Communications were sent out Monday July 9, 2007 by MNT and OPS.

10. LER Section 16, Safety Analysis section - Revise the third paragraph to better reflect the state of the OTdT function and what indications were available to Operations.

This section was revised to read:

The OTdT channels are not modeled explicitly in the Probabilistic Risk Analysis (PRA) because of the redundancy of the system. The only function adversely affected during the time period of interest was the Unit 2, Channel 4 axial flux input to the OTdT function. With the axial flux input functional unit inoperable, the OTdT function for Channel 4 was degraded. However, at 100% power the axial flux input would be zero and the other inputs to Channel 4 OTdT remained operable and would have responded if called upon.

Thus, the reliability of the OTdT function was degraded, but the remaining OTdT trip logic was operable and if needed would have tripped the 07/10/2007 07:05 � Page 5� PIP No: C-07-03408 Problem Investigation Process Catawba Nuclear Station reactor, when required. During the 13 hour1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> and 1 minute time period of interest, additional multiple failures would have been required such that an OTdT reactor trip, if required, would not actuate.

11.LER Section 16, Safety Analysis section - In the sixth paragraph, verify that the 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and 15 minutes time is correct.

This time was verified correct via TSAIL entry C2-07-1095 which shows SSPS being returned to NORMAL at 00.04 on 5/11/07. The time in question was the time from which SSPS was in TEST and the Card was blow. The card blew when the fuse was installed at 21:49 on 5/10/07.

Subtracting the two times yeilds 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and 15 minutes.

12.Last page of the document, check the numbering of pages.

The pages have been renumbered to reflect the total number of pages.

Originated By: APJ7336: JACKSON, ANTHONY P Team: RDH5775 Group: C-RGC Date: 07/09/2007 Signature:Tyke ...�InOiv�` Team Gioup . Date Due Date: 07/19/2007 Accepted By: RDH5775 RDH5775 C-RGC 07/09/2007 Assigned To: APJ7336 RDH5775 C-RGC 07/09/2007 Ready For Approval: APJ7336 RDH5775 C-RGC 07/09/2007 Approval Assigned To: RDH5775 RDH5775 C-RGC 07/09/2007 Approved By: RDH5775 RDH5775 C-RGC 07/10/2007 Final and Overall PIP Approval Responsible Group: C-MGT� Status: ReadyForApprove lndiv `Group� Date � Assigned To:� C-MGT 07/09/2007 Due Date:

Any Supplemental Concurrence Signatures Above Do Not Affect PIP Closure.

Closure Document Type� Closure Document No Attachments Generic Applicability � Responsible Group: Status:

GO PIP No:

Assessment Remarks:

No Current Signatures For This Section Failure Prevention Investigation No FPI Records for this PIP.

Remarks No Remarks for this PIP.

Maintenance Rule No Maintenance Rule Records for this PIP.

07/10/2007 07:05� Page 6� PIP No: C-07-03408

• Problem Investigation Process Catawba Nuclear Station End of the Document for PIP No:� C-7-3408 The status of this PIP is:� ReadyForApprove This PIP has been open for: 5 days (Note: All Corrective Actions were printed in this report.) �07/10/2007 07:05 Page 7� PIP No: C-07-03408