05000275/LER-2011-005, For Diablo Canyon Power Plant, Unit 1 - Emergency Diesel Generator Actuations Upon Loss of 230 Kv Startup Due to Electric Maintenance Testing Activities
| ML11214A089 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 07/22/2011 |
| From: | Becker J Pacific Gas & Electric Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| DCL-11-083, OL-DPR-80 LER 11-005-00 | |
| Download: ML11214A089 (11) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 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)(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)(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)(i)(B), Prohibited by Technical Specifications |
| 2752011005R00 - NRC Website | |
text
Iim'lI Pacific Gas and Electric Company James R. Becker Site Vice President Diablo Canyon Power Plant Mail Code 104/5/601 P. 0. Box 56 Avila Beach, CA 93424 805.545.3462 Internal: 691.3462 Fax: 805.545.6445 July 22, 2011 PG&E Letter DCL-1 1-083 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 10 CFR 50.73 Docket No. 50-275, OL-DPR-80 Diablo Canyon Unit 1 Licensee Event Report 1-2011-005-00 Emergency Diesel Generator Actuations Upon Loss of 230 kV Startup Due to Electrical Maintenance Testing Activities
Dear Commissioners and Staff:
Pacific Gas and Electric Company submits the enclosed Licensee Event Report (LER) regarding the Diablo Canyon Power Plant Unit 1 emergency diesel generator actuations after 230 kV startup power was lost due to maintenance activities. This LER is submitted in accordance with 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(2)(v)(D).
There are no new or revised regulatory commitments in this report.
These events did not adversely affect the health and safety of the public.
dnpo/50405004/5040501 0 Enclosure cc/enc:
Elmo E. Collins, NRC Region IV Michael S. Peck, NRC Senior Resident Inspector James T. Polickoski, NRR Project Manager Alan B. Wang, NRR Project Manager INPO Diablo Distribution A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway
- Comanche Peak
- Diablo Canyon
- Palo Verde o San Onofre o South Texas Project o WoLfCreek
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)
, the NRC may sfor each block) not conduct or sponsor, and a person is not required to respond to, the digits/characters finformation collection.
- 3. PAGE Diablo Canyon Power Plant Unit 1 05000 275 1 OF
- 4. TITLE Emergency Diesel Generator Actuations Upon Loss of 230 kV Startup Due to Electrical Maintenance Testing Activities
- 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.
I 05000 IFACILITY NAME DOCKET NUMBER 05 26 2011 2011 5
0 07 22 2011 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 1 5 20.2201(b)
[] 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
E] 50.73(a)(2)(vii)
El 20.2201(d) 5 20.2203(a)(3)(ii) 5 50.73(a)(2)(ii)(A) fl 50.73(a)(2)(viii)(A)
E] 20.2203(a)(1)
El 20.2203(a)(4) 5 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
E] 20.2203(a)(2)(i) 5 50.36(c)(1)(i)(A) j] 50.73(a)(2)(iii) 5 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL E] 20.2203(a)(2)(ii)
EJ 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A) 5 50.73(a)(2)(x) 1] 20.2203(a)(2)(iii) 5 50.36(c)(2)
F] 50.73(a)(2)(v)(A)
E] 73.71(a)(4) 100 E] 20.2203(a)(2)(iv) 5 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
E] 73.71(a)(5) 5] 20.2203(a)(2)(v)
[] 50.73(a)(2)(i)(A) 5 50.73(a)(2)(v)(C)
El OTHER
[= 20.2203(a)(2)(vi)
I] 50.73(a)(2)(i)(B)
[
50.73(a)(2)(v)(D)
Specify in Abstract below or in =
I. PLANT CONDITIONS
When the events occurred, Unit 1 was in Mode 1 (Power Operation) at approximately 100 percent power.
II. DESCRIPTION OF PROBLEM A. BACKGROUND The Diablo Canyon Power Plant (DCPP) electrical systems are designed to ensure an adequate supply of electrical power to all essential auxiliary equipment during normal operation and under accident conditions. Nonvital 4.16 kV alternating current (AC) auxiliary buses are energized by either of the offsite power sources. Vital AC buses [EA!IBUI have an additional available source: onsite power delivered by diesel generators. The electrical systems are designed so that failure of any one electrical device will not prevent operation of the minimum required engineered safety feature (ESF) equipment.
General Design Criteria (GDC) 17 states, in part, "An onsite electric power system and an offsite electric power system shall be provided to permit functioning of structures, systems, and components important to safety. The safety function for each system (assuming the other system is not functioning) shall be to provide sufficient capacity and capability to assure that (1) specified acceptable fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded as a result of anticipated operational occurrences and (2) the core is cooled and containment integrity and other vital functions are maintained in the event of postulated accidents."
DCPP offsite power is supplied by two systems that are physically and electrically separated and independent of each other:
a 230 kV system and a 500 kV system. This satisfies requirements established by General Design Criteria (GDC) 17. The 230 kV system provides startup power and is immediately available following a loss-of-coolant accident (LOCA) to assure that core cooling, containment integrity, and other vital safety functions are maintained. To make power available to the vital 4.16 kV buses, the 230 kV system provides power to Startup Transformer (SUT)IEAIIXFMR] 1-1 (230 kV to 12 kV),
energizing the 12 kV bus which then feeds SUT 1-2 (12 kV to 4.16 kV). The 500 kV system provides for transmission of the plant's power output, and is also available as a delayed access source of offsite power after the main generator is disconnected.
To produce onsite power, each unit has three emergency diesel generators (EDGs)[EK]IDGI which supply power to the 4.16 kV vital AC buses when power is unavailable or when a degraded voltage condition exists. After EDGs have started, they will supply power to their respective vital bus if the buses are deenergized. If the vital buses are not deenergized, the EDGs will continue to run in standby mode, ready to provide power if required. The EDGs will also start in standby mode on loss of startup power availability.
B. EVENT DESCRIPTION
At the time of the events, the Unit 2 Sixteenth Refueling Outage (2R16) was ongoing and scheduled 230 kV system testing was being performed on the 230 kV electrical protection equipment. On May 26, 2011, at 0226 PDT, and again on May 27, 2011, at 1212 PDT, while personnel were performing testing on Unit 2 to verify functionality of the 230 kV electrical protection equipment, Unit 1 lost 230 kV startup power.
The isolation of the offsite standby power source, and subsequent loss of power to startup feeder breakers for the 4.16 kV operating buses, caused all Unit I EDGs to start in standby mode. For both events, all Unit 1 EDGs started as designed, and were shutdown and returned to auto with no problems observed.
SUTs 1-1 and 1-2 were returned to service and Unit 1 startup power was declared operable on May 26, 2011, at 1710 PDT for the first event, and on May 27, 2011, at 1337 PDT for the second event.
Startup power on Unit 2 was cleared due to the maintenance activities being performed; therefore, it was unaffected by the events.
On May 26, 2011, at 0957 PDT, and on May 27, 2011, at 1712 PDT, Pacific Gas & Electric (PG&E) made 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> nonemergency reports (Reference NRC Event Notification 46894 and 46900) in accordance with 10 CFR 50.72(b)(3)(iv)(A).
C. STATUS OF INOPERABLE STRUCTURE, SYSTEMS, OR COMPONENTS THAT CONTRIBUTED TO THE EVENT There were no inoperable structures, systems, or components that contributed to the event. All systems functioned as designed.
D. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED
No other systems or secondary functions were affected.
E. METHOD OF DISCOVERY
The event was immediately known to licensed plant operators by alarms and indications received in the control room.
F. OPERATOR ACTIONS
Plant operators performed required surveillances, secured the Unit I EDGs, and proceeded to restore the availability of startup power to Unit 1.
G. SAFETY SYSTEM RESPONSES All Unit 1 EDGs started as designed with no problems observed.
III. CAUSE OF THE PROBLEM A. IMMEDIATE CAUSE PG&E preliminarily concluded that human performance deficiencies during testing activities associated with the 230 kV electrical protection equipment caused the loss of 230 kV startup power. The event on May 26, 2011, appears to have been caused by personnel attaching test equipment to terminals associated with the incorrect 230 kV protection system circuit (incorrect current transformer). The event on May 27, 2011, was caused by personnel attaching test equipment to terminals associated with a 230 kV protection system relay on the incorrect unit.
B. CAUSE
The cause will be provided in a supplemental report following the completion of a root cause evaluation (RCE).
IV. ASSESSMENT OF SAFETY CONSEQUENCES
At DCPP, the 230 kV startup system is the only offsite power system which is designed to be immediately available to mitigate the consequences of postulated accidents; therefore, this event could have prevented fulfillment of a safety function of the offsite electric power system. However, the Class 1E onsite EDGs remained available and would have provided power following a loss of offsite power.
The voltage on operating 12 kV buses was not affected by the isolation of 230 kV startup power, and the EDGs were not required since all vital buses were energized by Unit 1 auxiliary power (the Unit 1 main generator). As a result, no vital loads were affected by this event.
The increased conditional core damage probability for this event was assessed and found to be less than 4E-07.
This event had no adverse effect on the health and safety of the public.
V. CORRECTIVE ACTIONS
A. IMMEDIATE CORRECTION ACTIONS For the May 26,2011 event, PG&E performed troubleshooting to verify that the circuit was configured per the approved design; no issues were noted. The day and nightshift employees that perform this work were briefed on the event and on the station human performance tools that prevent such occurrences. Shortly after, with direct management oversight, the current circuit loop functional test was re-performed successfully.
For the May 27, 2011 event, PG&E re-performed the pre-job breif, focusing on roles and responsibilities, and installed barriers on all inservice relays that were not part of the testing. Management provided direct oversight, and independent verification was used for all restoration actions of the procedure.
B. CORRECTIVE ACTIONS TO PREVENT RECURRENCE (CAPRs)
CAPRs will be detailed in a supplemental report following the completion of a RCE.
VI. ADDITIONAL INFORMATION
A. FAILED COMPONENTS All components functioned as designed.
B. PREVIOUS SIMILAR EVENTS
A previous event occurred during 2R16 when personnel were modifying a panel that houses 230 kV electrical protection equipment. During modification, there was a similar loss of 230 kV startup power and EDG actuation on Unit 1 (See ML11820377, Licensee Event Report submitted on June 30, 2011). This event is also being reviewed as part of the RCE scope.
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- 11. Deliver this checklist (including RS-1A, if applicable), original of signed submittal &
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NRC 396 forms are retained by Learning Services and the DCPP (Personal information)
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PEER REVIEW CHECKLIST LICENSING SUBMITTAL (To be performed on final draft only.)
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DESCRIPTION
INITIALS*
Cover Letter Correct signatory letterhead (Ref. Xli.1D2)
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j VVI All pages numbered, except first page Date correct and appears on all pages (month, day, and year)
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TS and/or 10 CFR references correct References to other documents correct (e.g., DCLs, FSAR, etc.)
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PG&E Letter DCL-11-083 Subject: Emergency Diesel Generator Actuations Upon Loss of 230 kV Startup Due to Electrical Maintenance Testing Activities File Location:
S:\\RS\\CLERICAL\\DCLS - FINAL\\DCL-1 1-083\\DCL-1 1-083.DOC FSAR Update Review Utilizing the guidance in X13.1D2, does the FSAR Update need to be revised?
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PCD Commitment?
No YES OR NO IF YES, LIST PCD NUMBER (e.g., T35905, etc.)
Duplicate of New NCR Commitment in PCD?
No YES OR NO IF YES, LIST PCD NUMBER, AND CLARIFY TO CLERICAL HOW COMMITMENT TO BE REVISED Old PCD Commitment being changed?
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- Comanche Peak 9 DiabLo Canyon o Palo Verde
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