05000341/LER-2008-004, Relay Locking Straps Not Fully Engaged
| ML081570347 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 05/30/2008 |
| From: | Plona J Detroit Edison, DTE Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NRC-08-0044 LER 08-004-00 | |
| Download: ML081570347 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) 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)(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)(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 |
| 3412008004R00 - NRC Website | |
text
,-P Joseph H. Plona Site Vice President 6400 N. Dixie Highway, Newport, MI 48166 Tel: 734.586.5910 Fax: 734.586.4172 DTE Energy-10 CFR 50.73 May 30, 2008 NRC-08-0044 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington D C 20555
Reference:
Fermi 2 NRC Docket No. 50-341 NRC License No. NPF-43
Subject:
Submittal of Licensee Event Report No. 2008-004, "Relay Locking Straps Not Fully Engaged" Pursuant to 10 CFR 50.73(a)(2)(i)(B) and 50.73(a)(2)(vii), Detroit Edison is hereby submitting the enclosed Licensee Event Report (LER), No. 2008-004. This LER documents an April 9, 2008 discovery that relay locking straps were discovered not fully engaged.
No new commitments are made in this letter.
Should you have any questions or require additional information, please contact Mr.
Ronald W. Gaston of my staff at (734) 586-5197.
Sincerely, cc:
NRC Project Manager NRC Resident Office Reactor Projects Chief, Branch 4, Region MII Regional Administrator, Region IH Supervisor, Electric Operators, Michigan Public Service Commission
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: No. 3150-0104 Expires 8/31/2010 (9-2007)
, the NRC may (See reverse for required number of not conduct or sponsor, and a person is not required to respond to, the digits/characters for each block) information collection.
- 3. PAGE Fermi 2 05000341 1 OF 4
- 4. TITLE Relay Locking Straps Not Fully Engaged
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FACILITY NAME DOCKET NUMBER NUMBER NO 05000 04 09 2008 2008 004 00 05 30 2008 FACILITY NAME DOCKET NUMBER 05000
- 9. OPERATING MODE
- 11. THIS REPORT SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) 1 020.2201 (b) 0 20.2203(a)(3)(i) 0 50.73(a)(2)(i)(C)
[] 50.73(a)(2)(vii) 0 20.2201(d) 0 20.2203(a)(3)(ii) 0 50.73(a)(2)(ii)(A) 0 50.73(a)(2)(viii)(A) 0 20.2203(a)(1) 0 20.2203(a)(4) 0 50.73(a)(2)(ii)(B) 0 50.73(a)(2)(viii)(B)
]0 20.2203(a)(2)(i) 0 50.36(c)(1 )(i)(A) 0 50.73(a)(2)(iii) 0 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL 0
20.2203(a)(2)(ii) 0 50.36(c)(1 )(ii)(A) 0 50.73(a)(2)(iv)(A) 0 50.73(a)(2)(x) 0 20.2203(a)(2)(iii) 050.36(c)(2) 0 50.73(a)(2)(v)(A) 073.71 (a)(4) 100%
0 20.2203(a)(2)(iv) 0 50.46(a)(3)(ii) 0 50.73(a)(2)(v)(B) 073.71 (a)(5) 0 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A) 0 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 (If more space is required, use additional copies of NRC Form 366A)
Initial Plant Conditions
Mode 1
Reactor Power 100 percent Description of the Event On April 9, 2008, during a walkdown in preparation for planned maintenance to replace an Agastat relay [RLY] in the H2 1-P081 Testability Cabinet [CAB], an Instrument Technician noted that the relay locking straps for relays B3 1-K201B and B31-K203B were not fully engaged. The locking strap is required to provide restraint to the relays under seismic conditions. This condition was verified by a Component Engineer and the relay locking straps were then fully engaged. Relay locking straps for all relays in the H2 1-P081 Testability Cabinet were verified to be fully engaged.
On April 16, 2008, System Engineering and Operations performed a walkdown to visually inspect all accessible relays in all Testability Cabinets (H2 1-P080, H2 1-P081, H21-P082, H21-P083, H21-P084, H21-P085, H21-P086, and H21-P087). The walkdown identified four relays with the locking straps not fully engaged, relays B3 1-K203B (the other side of this relay was identified to be not fully engaged on April 9, 2008), B21-K209G, B21-K203B, and E51-K201C. All relays were Agastat relays with style ECROO02 sockets and ECRO133 locking straps. The relays perform the following functions:
B31-K203B, Trip Channel A, Trip System A, control relay for Reactor Recirculation Pump B [AD]
differential pressure; operates during Low Pressure Coolant Injection (LPCI) Loop Select [BO] to determine which reactor recirculation pumps are running.
B3 1-K201B, Trip Channel B, Trip System A, control relay for reactor recirculation riser differential pressure; operates during LPCI Loop Select to determine if either reactor recirculation loop has a break.
B21-K209G, Trip Channel C, Trip System B, control relay for high drywell pressure for Emergency Core Cooling Systems.
E51-K201C, Trip Channel C, Trip System A, control relay for Reactor Core Isolation Cooling (RCIC)
[BN] exhaust pressure high turbine trip.
B21-K203B, Trip Channel B, Trip System A, control relay for RCIC Level 8 trip.
All relays were restored to their original configuration by fully engaging their relay locking straps.
Work orders were subsequently generated to inspect those relays that were not accessible without entry into the Testability Cabinets. All Testability Cabinet relay locking straps were verified to be fully engaged. Relays located outside the Testability Cabinets were verified to have their locking straps fully engaged.
1U.S. NUCLEAR REGULATORY COMMISSION (9-2007)
LICENSEE EVENT REPORT (LER)
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL REVISION Fermi 2 05000341 NUMBER NUMBER 3 OF 4 2008 004 30
Significant Safety Consequences and Implications
Operations and Engineering reviewed the relay functions for the five affected relays and determined with the exception of B2 1 -K203B, control relay for RCIC Level 8 trip, all other relay design functions would be met by redundant relays, should the relays fail to function due to the lack of a properly engaged locking strap during a seismic event. In the case of the control relay for the level 8 trip an automatic level 8 trip would not occur if the relay failed to operate as a result of the relay locking strap not being fully engaged. The operator retained the ability to manually trip the RCIC system in response to a rising water level.
All relays with the exception of the E5 1-K201C, control relay for RCIC exhaust pressure high turbine trip are explicitly modeled in the Fermi 2 Probabilistic Safety Analysis (PSA) model. Relay E51-K201CI does not impact,an'accident sequence and was not included in the PSA model. Since the exposure time for the condition is assumed to be longer than one year, the results of the analysis are expressed as frequency rather than probability. A conservative assumption was made to fail the four remaining individual relays resulting in a calculated value for the change in Core Damage Frequency of 1.0 E-7/year. This is wellbelow the threshold of 1.0 E-6/year required in Regulatory Guide (RG) 1. 174, "An Approach for using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis." The calculated value for the change in Large Early Release Frequency (LERF) is 3.0E-9/year, which is well below the threshold of 1.0 E-7/year required in Regulatory Guide (RG) 1.174. This demonstrates that the safety significance of this condition is very low.
This event is being reported under 50.73(a)(2)(i)(B), as a condition which was prohibited by the Technical Specifications (TS) for:
B21-K209G, control relay for high drywell pressure, required placing the channel in a tripped condition within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> per TS 3.3.6.1, Condition A.
B21-K203B, control relay for RCIC Level 8 trip, required restoring the channel to an operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> per TS 3.3.5.2, Condition C.
This event is also reportable under 50.73(a)(2)(vii), as a common cause inoperability of independent trains or channels since a single cause or condition caused at least one independent train or channel to become inoperable in multiple systems. The independent trains and channels are:
B3 1-K203B, Trip Channel A, Trip System A, control relay for Reactor Recirculation Pump B differential pressure; operates during Low Pressure Coolant Injection (LPCI) Loop Select to determine which reactor recirculation pumps are running.
B3 1-K201B, Trip Channel B, Trip System A, control relay for reactor recirculation riser differential pressure; operates during LPCI Loop Select to determine if either reactor recirculation loop has a break.
B21-K209G, Trip Channel C, Trip System B, control relay for high drywell pressure Emergency Core Cooling Systems.
B21-K203B, Trip Channel B, Trip System A, control relay for RCIC Level 8 trip I
NRIC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (9-2007)
LICENSEE EVENT REPORT (LER)
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL REVISION Fermi 2 05000341 NUMBER NUMBER -4 OF 4 2008 004 00
Cause of the Event
Less than adequate work practices led to the relay locking straps no t being fully engaged into their bases. Contributing causes: 1) work package instructions not providing an adequate level of detail; 2) training material not covering the locking straps resulting in varying levels of skill and experience, and
- 3) the layout of the testability cabinets makes it difficult to visually verify a locking strap is fully engaged.
This condition applies to a total of 398 Agastat relays requiring seismic qualification. There were 217 relays located in the Testability Cabinets. All 398 of these relays were verified to have their locking straps fully engaged.
Corrective Actions
Relay locking straps were fully engaged and verified. Action. was taken to review the event and lessons learned with Instrument Technicians.
Training will be provided to instrument technicians and licensed operators on recognition of relay locking straps less than fully engaged. Preventative maintenance events for Agastat relay replacement will be modified to include specific steps and verifications for reinstalling relay locking straps.
This licensee-identified condition has been documented in the Fermi 2 Corrective Action Program. A root cause evaluation has been performed to address the event and develop pertinent corrective actions.
Additional evaluation and corrective actions are being performed in accordance with. the corrective actio n program. Actions will be determined, tracked and implemented commensurate with their safety significance and in accordance with the program guidelines.
Additional Information
A. Failed Components: None.
B. Previous LERs on Similar Problems: None 1