HNP-97-095, Provides Addl Info Concerning Mod Testing & Completed Failure Modes & Effects Analysis Re EDG Protection Circuitry
| ML18012A755 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 04/29/1997 |
| From: | Robinson W CAROLINA POWER & LIGHT CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| HNP-97-095, HNP-97-95, NUDOCS 9705060250 | |
| Download: ML18012A755 (18) | |
Text
CATEGORY REGULATZ INEORMATION DISTRIBUTION ZSTEM (RZDS)
EPCCESSION NBR:9705060250 DOC.DATE: 97/04/29 NOTARIZED: YES
'FACE'L:50-400 Shearon Harris Nuclear Power Plant, Unit 1, Carolina AUTH.NAME AUTHOR AFFILIATION ROBINSON,W.R.
Carolina Power 6 Light Co.
RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)
SUBJECT:
Provides addi info concerning mod testing
& completed failure modes s effects analysis re EDG protection circuitry.
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Carolina Power 8 Light Company PO Box 165 New Hill NC 27562 lAPR 2 9 William R. Robinson Vice President Harris Nuclear Plant SERIAL: HNP-97-095 10 CFR 50.59(c) 10 CFR 50.90 United States Nuclear Regulatory Commission ATTENTION: Document Control Desk Washington, DC 20555 SHEARON HARRIS NUCLEARPOWER PLANT DOCKETNO. 50-400/LICENSE NO. NPF-63 ADDITIONALINFORMATIONCONCERNING EMERGENCY DIESEL GENERATOR PROTECTION DURING TESTING
Dear Sir or Madam:
By letter dated April 18, 1997, Carolina Power &Light Company (CP&L) requested NRC review ofa proposed modification related to Emergency Diesel Generator (EDG) Protection During Testing for the Harris Nuclear Plant (HNP). In addition, a meeting with the NRC staff was held on April7, 1997, to discuss the proposed modification to the EDG protection circuitry and formally notify the NRC staffofthe unreviewed safety question. In response to NRC staff questions during review ofthe proposed change, CP&L provides the followingadditional information concerning modification testing and the completed Failure Modes and Effects Analysis (Enclosure 1).
Initial acceptance testing for the installed modification was previously discussed in the April 18, 1997 letter; however, the followingadditional description is provided. Acceptance testing on the "A"train willconsist ofverifying that the loss ofoffsite power (LOOP) logic, Breakers 101 AND 102 OPEN or Breaker 101 OPEN ANDeither main generator lockout, willresult in CR1/1748 contact closure.
Once the modification is installed, CR1/1748 relay (which willhave been previously demonstrated to function as designed) willbe actuated to verify that the installed circuitry functions as designed up to and including trip signals to the Emergency Diesel Generator (EDG) output Breaker 106 and the non-safety bus to Engineered Safety Feature (ESF) bus tie Breaker 105. Similar acceptance testing ofthe "B"train willverify design functions for the corresponding "B"train circuitry.
QDI
(
'F705060250 9704Pq ~,,,
) II3IllIIIIIIIIIIIIIIIIIIIIIIIIIIIII The followingis a description ofintegrated testing to be performed in the future. An integrated test ofthe LOOP logic willbe performed every other refueling outage on each train. This test willinclude simulating a loss ofoffsite power to verify the circuitry functions as designed up to and including trip signals to the EDG output breaker and the non-safety bus to ESF bus tie breaker.
State Road1134 NewHill NC Tel 919362-2502 Fax 919362-2095
Document Control Desk HNP-97-095 / Page 2 As described in the enclosed Failure Modes and Effects Analysis, ifthe EDG protection circuitry added by the proposed modification does not function as designed, operator actions are available as a backup.
Operating Procedure OP-155, "Diesel Generator Emergency Power System" willbe revised to describe the required backup operator actions. In addition, operator training for these backup operator actions willbe conducted.
The followingprecaution (or similar wording) will be added to OP-155:
"Ifa loss ofoffsite power (LOOP) occurs while an EDG is paralleled to the grid, breakers 105 (125) and 106 (126) should automatically trip open, which willleave the diesel running unloaded.
Breaker 106 (126) should then automatically reclose and the sequencer start to load. Ifbreaker 106 (126) fails to open, operator action is required to manually open the breaker.
The LOOP signal to open breakers 105 (125) and 106 (126) is generated by:
Both breakers 101 (121) and 102 (122) open, Breaker 101 (121) open and either main generator lockout tripped Indications that this circuit has actuated properly include proper sequencer operation, or indication that the EDG is running in the emergency mode.
Ifthese conditions occur while the EDG is paralleled to the grid, and breaker 106 (126) fails to open, (i.e., no indication ofproper actuation as described above exists), the breaker must be manually tripped from the Main Control Board (MCB) or, ifcontrol is transferred to the local Generator Control Panel (GCP), from the GCP. Since occurrence ofa LOOP may not be obvious at the GCP, action to trip Breaker 106 (126) from the GCP must be directed from the Main Control Room."
This additional information supplements the April 18, 1997 submittal and does not change the conclusions ofthe previously submitted No Significant Hazards Evaluation or Environmental Considerations discussions.
Document Control Desk HNP-97-095 / Page 3 Please refer any questions regarding this submittal to Ms. D. B. Alexander at (919) 362-3190.
Sincerely, JHE/jhe Enclosure W. R. Robinson W. R. Robinson, having been first duly sworn, did depose and say that the information contained herein is true and correct to the best ofhis information, knowledge and belief; and the sources of his information are employees, contractors, and agents ofCarolina Power &Light Company.
My commission expires:
(p - '7-9E Notary ( eal)
Mr. J. B. Brady, NRC Sr. Resident Inspector Mr. Mel Fry, N.C. DEHNR Mr. L. A. Reyes, NRC Regional Administrator Mr. N. B. Le, NRC Project Manager
Document Control Desk HNP-97-095 / Page 4 bc:
Mr. T. C. Bell Mr. R. K. Buckles (LIS)
Mr. H. Chernoff (RNP)
Mr. B. H. Clark Mr. G. W. Davis Mr. J. W. Donahue Ms. S. F. Flynn Mr. H. W. Habermeyer, Jr.
Mr. W. J. Hindman Mr. R. M. Krich Ms. W. C. Langston (PE&RAS File)
Mr. R. D. Martin Mr. W. S. Orser Mr. G. A. Rolfson Mr. W. K. Russell Mr. R. F. Saunders Mr. D. L. Tibbitts Mr. M. A. Turkal (BNP)
Mr. T. D. Walt Nuclear Records Harris Licensing File File: H-X-0511
ENCLOSURE TO SERIAL: HNP-97-095 ENCLOSURE I SHEARON HARRIS NUCLEARPOWER PLANT NRC DOCKETNO. 50-400/LICENSE NO. NPF-63 EMERGENCY DIESEL GENERATOR PROTECTION DURING TESTING
ESR NO.
9700005 REV NO.
1 PAGE NO.
l(u Failure Modes and Effect Anal sis This Failure Modes and Effects Analysis (FMEA) per EGR-NGGC-0154 examined the credible ways in which components used or affected by the implementation of ESR 97-00005, EDG Protection During Load Test, can fail, the effect of those failures on the Safety Bus and the EDG, and the mitigating functions or actions in place or planned.
The questions examined include:
- 1. Which components are to be analyzed?
2.
What are the critical functions of these components?
3.
What are the component failure modes?
- 4. What mechanisms might produce these modes of failure?
5.
What are the effects of the failures on the Safety Bus and EDG?
6.
Is the failure in the safe or unsafe direction?
7.
What mitigating functions or actions are in place to compensate for the failures?
The key rules and assumptions made for this FMEA are:
~
One EDG is in test and paralleled to offsite power with the other EDG operable and in standby (excluding Modes 5 and 6 where only one EDG is required to be operable).
~
EDGs A and B are not paralleled to offsite power concurrently.
~
Cascading failures resulting from the effects of a single failure are considered as a single failure.
~
The effects of failures with and without offsite power available are addressed.
~
Critical operator error upon a loss of offsite power and failure of the LOOP detection relay logic is considered as a failure mode.
~
Non-1E circuit failures are assumed to occur in addition to a single failure of Safety Related equipment.
~
Safety Injection signal logic is outside of the scope of this analysis.
~
Station Blackout procedures are outside of the scope of this analysis.
DESIGN SECTIO ESR NO.
9700005 REV NO.
1 PAGE NO.~l FMEA
Conclusion:
In a LOOP scenario (without LOCA) occurring while one EDG is paralleled to offsite power for testing, a single failure of the other train EDG could result in a Station Blackout ifa failure in the LOOP detection relay logic (portions of which are Non-1E) and critical operator error both occur.
Since Non-1E circuitry and operator action are not currently credited for safety bus integrity upon a loss of offsite power event, the analyzed sequence of events and equipment failures does 'not meet the single failure criterion. However, the LOOP detection relay logic is considered to be reliable, willbe subjected to periodic testing, and provides the best method of protection for the EDG and Safety Bus while paralleled to offsite power for testing.
The current design is based upon assumptions (i.e. EDG overload on a LOOP) which have proved to be invalid.
In addition, the EDG willonly be paralleled to offsite power for short periods of time during testing and willnot be paralleled to offsite'ower during expected adverse weather conditions. Ifthe EDG output breaker for the division in test does not automatically trip due to the LOOP detection relay logic upon loss of offsite power, operator action willbe taken to trip the breaker.
The EDG output breaker can be operated from the main control room or, ifcontrol is transferred to the EDG local control panel, from the EDG local control panel.
These compensatory measures provide reasonable assurance that electrical power willbe made available to one of the redundant safety buses in a timely manner following a LOOP coincident with EDG testing in parallel with offsite power, should a single failure of safety related equipment also occur.
DESIGN SECTION FMEATABLE ESR NO.
9700005 REV NO.
PAGE NO.
f 'E No.
Component ID (Train-A)
(See Figure 2)
Loop detection relay-CRI/1748 (See Figure 2)
Loop detection relay-CRI/1748 Function (See Figure I)
Actuates on Bkr 101
& 102 open or 101 open and either Main Generator Lockout (86G IA or 86G IB) tripped.
(See Figure I)
Actuates on Bkr 101
& 102 open or 101 open and either Main Generator Lockout (86G IAor 86G IB) tripped.
Failure Mode Critical relay contact fails to close in response to a LOOP (EDG in test and paralleled to offsite power)
False actuation ofrelay (EDG in test and paralleled to offsite power)
Credible Failure Mechanisms Loss ofnon-I E uninterruptible power to relay coil circuit. Open circuit in relay coil. Failure ofrelay contact to close upon relay actuation.
Short circuit across relay contact.
Short circuit that causes relay coil to actuate.
Effect on Safety Bus and EDG Breaker 105 and / or Breaker 106 do not trip from LOOP relay logic as designed.
This results in the EDG picking up the loads from buses IA-SAand ID also preventing a UV trip ofBkr 104.
Ifsufficient loading exists, overload of the EDG willoccur (51V relay may actuate and trip Bkr 106 ifloading is severe).
Ifsufficient load does not exist to overload the EDG then the EDG would continue to power both buses and automatic actuation ofthe sequencer would not occur.
This failure is in the unsafe direction.
Breaker 105 and 106 trip while EDG in test and paralleled to offsite power.
The load reject on the EDG is within specifications and the engine continues to run. Breaker 105 can not be reclosed if the condition does not clear. Power is momentarily lost to bus IA-SAuntil Bkr 106 automatically recloses and the sequencer actuates.
This failure is in the safe direction.
Mitigating Functions / Actions in Place IfBkr 106 does not automatically trip due to the LOOP relay logic upon loss ofoffsite power, operator action willbe taken to trip Bkr 106. (The breaker can be operated from the main control room or, ifcontrol is transferred to the EDG local control pane~
from the EDG local control panel.)
When Bkr 106 opens, a UV on Bus IA-SAwilltrip Bkr 105 and a UV on Bus ID trips Bkr 104. A Trip for Bkr 105 would also be generated from CRI/1727 when Bkr 104 opens.
Ifthe manual trip ofBkr 106 is accomplished before significant EDG overload occurs then the engine can be expected to remain running and automatic reclosing ofBkr 106 and loading by the sequencer willtake place.
Due to the loads typically present on the buses during EDG load testing it is expected that the EDG willnot be severely overloaded duri this event scenario (See Figure 3)
The Bkr 106 trip results in reset ofthe SM/SA EDG in test relay contact and a loss ofpower to bus IA-SAwhich in turn causes automatic reclosure ofBkr 106 aAer 1.5 seconds and automatic actuation ofthe sequencer.
Safety bus loads can be powered from the EDG until the problem is resolved and offsite power restored to bus IA-SA. No actual LOOP exists so the other safety bus is not effected.
DESIGN SECTION FMEA TABLE ESR NO.
9700005 REV NO.
I PAGE NO.~la No.
Component ID (Train-A)
(See Figure 2)
Loop detection relay-CRI/1748 Function (See Figure I)
Actuates on Bkr 101
& 102 open or 101 open and either Main Generator Lockout (86G IA or 86G IB) tripped.
Failure Mode Critical relay contact fails to close in response to a LOOP (EDG in standby)
Credible Failure Mechanisms Loss ofnon-I E uninterruptible power to relay coil circuit. Open circuit in relay coil. Failure ofrelay contact to close upon relay actuation.
Effect on Safety Bus and EDG Breaker 104 trips due to UV on Bus ID, Breaker 105 trips from IA-SAUV and Bkr 104 open logic and Bkr 106 is already open.
Power to bus IA-SA is lost due to loss ofoffsite power and because the EDG is not operating.
Bus IA-SA UV results in auto start ofEDG, auto closure ofBkr 106, and sequencer actuation.
Mitigating Functions / Actions in Place 86UV/SA energizes on LOOP. IA-SA loads are shed. Bkr 106 closes once EDG is ready to load. Sequencer commences with LOOP program loading. Safety bus responds normally to the LOOP.
(See Figure 2)
Loop detection relay-CRI/1748 (See Figure I)
Actuates on Bkr 101
& 102 open or 101 open and either Main Generator Lockout (86G IA or 86G I B) tripped.
False actuation ofrelay (EDG in standby)
Short circuit across relay contact.
Short circuit that causes relay coil to actuate.
This failure is in the safe direction.
Breaker 105 trips and Bkr 106 is already open.
Power to bus IA-SA is lost due to tripping ofBkr 105 and because the EDG is not operating.
Bus IA-SAUV results in auto start ofEDG, auto closure ofBkr 106, and sequencer actuation. Breaker 105 cannot be reclosed ifthe condition does not clear.
86UV/SA energizes on Bkr 105 trip. IA-SA loads are shed. Bkr 106 closes once EDG is ready to load. Sequencer commences with LOOP program loading.
Safety bus loads can be powered from the EDG until the problem is resolved and offsite power restored to bus IA-SA. No actual LOOP exists so the other safety bus is not effected.
This failure is in the safe direction.
DESIGN SECTION FMEA TABLE ESR NO.
9700005 REV NO.
1 PAGE NO.
IBb No.
Component ID (Train-A)
(See Figure 2)
CR2/1727 Function (See Figure 2 &3)
Actuates on closure ofcontact 10-11 of relay CR I/1748.
Trips breaker 105, picks up CR2/1702 to trip Bkr 106 if EDG is in test.
Failure Mode Critical relay contacts fail to close in response to a LOOP (EDG in test and paralleled to offsite power)
Credible Failure Mechanisms Loss ofpower to relay circuit. Open circuit in relay coil.
Failure ofrelay contact to close upon relay actuation.
Failure ofCRI/1748 to actuate.
Effect on Safety Bus and EDG Same as item No. 1 ifboth Bkr 105 and 106 fail to trip.
Bkr 105 and Bkr 106 trip circuits are controlled by two separate sets ofcontacts from CR2/1727. IfBkr 106 tripped and Bkr 105 didn', power would be lost to Bus IA-SAbecause ofthe LOOP and Bkr 106 trip. The EDG would continue to run. The Bkr 106 trip would reset the EDG in test SM/SA relay contact and actuate a UV on bus IA-SA and ID. The UV on bus ID would trip Bkr 104, which inturn trips Bkr 105. Bkr 106 would automatically reclose aAer 1.5 seconds, and the sequencer would actuate.
Mitigating Functions / Actions in Place Same as item No. I ifboth Bkr 105 and 106 fail to trip.
IfBkr 106 trips, a normal LOOP response would occur.
IfBkr 105 trips and Bkr 106 doesn', bus IA-SAwould not respond to the LOOP but would remain powered by the EDG. Operator action is required to trip Bkr 106 in order for the sequencer to detect a loss ofoffsite power.
IfBkr 105 tripped and 106 didn', the load from bus ID would be shed from the EDG and it would continue to run supplying power to bus IA-SA,however, the sequencer would not actuate as required in response to the LOOP.
This failure is in the unsafe direction unless Bkr 106 trips as described.
DESIGN SECTION FMEATABLE ESR NO.
9700005 REV NO.
I PAGE NO. ~lc.
No.
Component ID (Train-A)
(See Figure 2)
CR2/1727 (See Figure 2)
CR2/1727 Function (See Figure 2 &3)
Actuates on closure ofcontact 10-11 of relay CR 1/1748.
Trips breaker 105, picks up CR2/1702 to trip Bkr 106 if EDG is in test.
(See Figure 2 &3)
Actuates on closure ofcontact 10-11 of relay CR1/1748.
Trips breaker 105, picks up CR2/1702 to trip Bkr 106 if EDG is in test.
Failure Mode False actuation ofrelay (EDG in test and paralleled to offsite power)
Relay fails to actuate or critical relay contacts fail to close in response to a LOOP(EDG in standby).
Credible Failure Mechanisms Short circuit across relay contact.
Short circuit that causes relay coil to actuate.
Loss ofpower to relay circuit. Open circuit in relay coil.
Failure ofrelay contact to close upon relay actuation.
Failure ofCR1/1748 to actuate.
Effect on Safety Bus and EDG Same as item No. 2 Breaker 105 and 106 trip while EDG in test and paralleled to offsite power. The EDG continues to run. Breaker 105 cannot be reclosed ifthe condition does not clear.
Power is momentarily lost to bus IA-SAuntil Bkr 106 automatically recloses and the sequencer actuates.
This failure is in the safe direction.
Same as item 3.
Breaker 104 trips due to UV on Bus 1D.
Breaker 105 trips from IA-SAUV and Bkr 104 open logic. Bkr 106 is already open. Power to bus 1A-SA is lost due to loss ofoffsite power and because the EDG is not operating.
Bus 1A-SA UV results in auto start ofEDG, auto closure ofBkr 106, and sequencer actuation.
MitigatingFunctions/Actions in Place Same as item No. 2 (See Figure 3)
The Bkr 106 trip results in reset ofthe SM/SA EDG in test relay contact and a loss ofpow~
to bus 1A-SA which in turn causes autom~
reclosure ofBkr 106 aAer 1.5 seconds and automatic actuation ofthe sequencer.
Safety bus loads can be powered from the EDG until the problem is resolved and offsite power restored to bus 1A-SA. No actual LOOP exists so the other safety bus is not effected.
Same as item 3.
86UV/SA energizes on LOOP. 1A-SA loads are shed.
Bkr 106 closes once EDG is ready to load. Sequencer commences with LOOP program loading. Safety bus responds normally to the LOOP.
This failure is in the safe direction.
DESIGN SECTION FMEA TABLE ESR NO.
9700005 REV NO.
I PAGE NO.~)~
Component ID (Train-A)
(See Figure 2)
CR2/1727 Function (See Figure 2 &3)
Actuates on closure ofcontact 10-11 of relay CR I/1748.
Trips breaker 105, picks up CR2/1702 to trip Bkr 106 if EDG is in test.
Failure Mode False actuation ofrelay (EDG in standby)
Credible Failure Mechanisms Short circuit across relay contact.
Short circuit that causes relay coil to actuate.
Effect on Safety Bus and EDG Same as item No. 4 Breaker 105 trips and Bkr 106 is already open.
Power to bus IA-SA is lost due to tripping ofBkr 105 and because the EDG is not operating.
Bus IA-SAUV results in auto start ofEDG, auto closure ofBkr 106, and sequencer actuation. Breaker 105 can not be reclosed ifthe condition does not clear.
Mitigating Functions / Actions in Place Same as item No.4 86UV/SA energizes due to Bkr 105 trip. IA-SA loads are shed.
Bkr 106 closes once EDG is ready to load. Sequencer commences wi LOOP program loading.
Safety bus loads can be powered from the EDG until the problem is resolved and offsite power restored to bus IA-SA. No actual LOOP exists so the other safety bus is not effected.
(See Figure 3)
Slvf/SA (See Figure 3)
SM/SA Permissive for 86UVX, K601 (SIS) or CR2/1727 (LOOP) to trip Bkr IC6 when EDG is in test.
Permissive for 86UVX, K601 (SIS) or CR2/1727 (LOOP) to trip Bkr 106 when EDG in test.
Relay fails to actuate when EDG is placed in test and paralleled to offsite power (EDG in test and paralleled to offsite power)
False actuation ofrelay (EDG in standby)
Loss ofpower to relay circuit. Open circuit in relay coil.
Failure ofrelay contact to close upon relay actuation.
Short circuit across relay contact.
Short circuit that causes relay coil to actuate.
This failure is in the safe direction.
With EDG in test, Bkr 106 would not trip from LOOP, UVor Sl. Bkr 105 trips.
EDG continues to carry safety bus loads, however, the sequencer does not actuate as required.
This failure mode existed prior to the modification under consideration and remains unchanged.
This failure is in the unsafe direction.
Bkr 106 is already open. Ifthe condition fails to clear and the EDG starts on 86UV/SA, LOOP, or Sl Bkr 106 willnot stay closed when automatically closed.
This willprevent one train ofsafety bus power from being available. This failure mode existed prior to the modification under consideration and remains unchanged.
Operator trips Bkr 106 per procedure and 86UV/SA energizes.
IA-SA loads are shed.
Bkr 106 closes once EDG is ready to load.
Sequencer commences with LOOP program loading.
Under present design, Operator could not trip Bkr 106.
Opposite train EDG functions as designed.
This failure is in the unsafe direction.
DESIGN SECTION FMEATABLE ESR NO.
9700005 REV NO.
I PAGE NO.~e No.
Component ID (Train-A)
Bus UPP-I A Function Provides 120VAC power to relay coil for CR I/1748 and CR3/1748 Failure Mode Loss ofpower to Bus UPP-IA Credible Failure Mechanisms Electrical fault on Bus UPP-IA or spurious opening of feeder breaker to bus Effect on Safety Bus and EDG CRI/1748 and CR3/1748 willnot actuate; therefore, opening ofBreaker 101 and 102 or 101 and either main generator lockout willnot be detected.
Breaker 105 and 106 willnot open with the EDG in test and paralleled to grid. Breaker 105 would not trip from 1748 relay whether EDG in test or standby.
Mitigating Functions / Actions in Place Administrative controls are in place to ensure that only one EDG is in test at any given time.
Loss ofpower to the CRI/1748 and CR3/1748 relay affects Breaker 106/126 logic only when EDG in test. (Trip is enabled by SM relay contact). Trip of Breaker 105 frot the 1748 relay is not a credited trip. Credited trip ofBreaker 105 is from the 86UV relay.
This failure is in the unsafe direction.
UPP-IA is fed from a UPS (60 kVAinverter).
Administrative control willbe in place to ensure the inverter is fed from its normal source prior to placing EDG in test.
12 Operator Immediately trip Bkr 106 ifit fails to automatically trip due to the LOOP detection relay logic upon loss ofoffsite power.
Fails to trip Bkr 106 as required by procedure for unforeseen reasons.
Operator Error EDG picks up the loads from buses IA-SA and ID also preventing a UV trip of Bkr 104.
Ifsufficient loading exists, overload of the EDG willoccur (5 1 V relay may actuate and trip Bkr 106 ifloading is severe).
Opposite train EDG functions as designed.
Ifsufficient load does not exist to overload the EDG then the EDG would continue to power both buses and automatic actuation ofthe sequencer would not occur.
This failure is in the unsafe direction.
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