ML112660497

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Transmittal of Accident Sequence Precursor Analysis for Calvert Cliffs Nuclear Power Plant, Unit No. 2
ML112660497
Person / Time
Site: Calvert Cliffs 
Issue date: 09/28/2011
From: Pickett D
Plant Licensing Branch 1
To: George Gellrich
Calvert Cliffs
Pickett D, NRR/DORL/LPL1-1, 415-1364
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555*0001 September 28, 2011 Mr. George H. Gellrich, Vice President Calvert Cliffs Nuclear Power Plant, LLC Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657-4702

SUBJECT:

TRANSMITTAL OF ACCIDENT SEQUENCE PRECURSOR ANALYSIS FOR CALVERT CLIFFS NUCLEAR POWER PLANT, UNIT NO.2

Dear Mr. Gellrich:

The enclosure provides the final result of the Accident Sequence Precursor (ASP) analysis of an event which occurred at Calvert Cliffs Nuclear Power Plant, Unit No.2 as documented in licensee event report 318/10-001-01 and inspection report 50-318/10-06. The event occurred on February 18, 2010, when the reactor scrammed following a loss of power to all 4 reactor coolant pumps. Loss of power to the Unit 2 non-safety related buses resulted in loss of the normal reactor coolant system heat removal path. In addition, emergency diesel generator 2B automatically started but tripped 15 seconds later. The ASP analysis calculated a conditional core damage probability (CCDP) of 2 x 10"5.

The Nuclear Regulatory Commission (NRC) established the ASP Program in 1979 in response to the Risk Assessment Review Group Report (see NUREG/CR-0400, dated September 1978).

The ASP Program systematically evaluates U.S. nuclear power plant operating experience to identify, document, and rank the operating events most likely to lead to inadequate core cooling and severe core damage (precursors).

As described in the NRC Regulatory Issue Summary (RIS) 2006-24, "Revised Review and Transmittal Process for Accident Sequence Precursor Analyses," the Office of Nuclear Regulatory Research implemented several process changes to the ASP Program. In accordance with the RIS, this event has a CCDP less than or equal to 1x 10-4 ; therefore, a formal licensee review was not requested.

For more information about the ASP Program, see the annual ASP Program status report at bttp://www.nrc.gov/read ing-rm/doc-collections/com mission/secys/20 1 0/secy201 0-0125/2010 0125scy.pdf.

G. Gellrich

- 2 The enclosure containing the final analysis report is provided for your information.

Please contact me at 301-415-1364 if you have any questions.

Sincerely, Douglas V. Pickett, Senior Project Manager Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-318

Enclosure:

Final Precursor Analysis cc w/encl: Distribution via Listserv

Final Precursor Anal~sis

£Wit*mu'iWiiig,iYiUki'U'?i,'iik*i.iF"'**'i.tai*jl~l!Atm'i;i§Cf51(*';'i;i41¥'kg; Reactor Trip Due to a Partial Loss Offsite Power with a Calvert Cliffs, Unit 2 Subsequent Loss of Condenser Heat Sink and the Failure of an Emergency Diesel Generator.

Event Date: 02/18/2010 LER: 318/10-001-01 CCDP= 2x 1 0-5 I

IR:

50-318/10-06 EVENT

SUMMARY

Brief Event Description. On February 18, 2010, at 0824, ground over-current relay 2RY251 G/B-22-2 failed to actuate as designed, permitting the Unit 1 ground over-current condition to reach the associated 500kV/13kV transformer [P-13000-2J. Ground O/C protection for the P 13000-2 transformer actuated which deenergized the 500kV "Red Bus" offsite power supply, the Bus 22, and all four Unit 2 reactor coolant pumps (RCPs). The Unit 2 reactor automatically tripped from full reactor power in response to the associated reactor protection system trip on reactor coolant system (RCS) low flow. The P-13000-2 isolation also deenergized the 13 kV Bus 21, which deenergized the Unit 2 Safety Bus 24, and several Unit 2 non-safety 4 kV buses.

Emergency Diesel Generator (EDG) 2B started, but tripped 15 seconds later due to a low lube oil pressure Signal and Bus 24 remained deenergized.

At 0848, Unit 2 operators exited Emergency Operating Procedure (EOP)-O, Reactor Trip and entered EOP-2, Loss of Flow and Loss of Off site Power. At 0857, operators reenergized the Bus 24 via the alternate feeder breaker. At 0900, Unit 2 operators restored RCS letdown and maintained appropriate pressurizer level control. At 1117, Unit 2 operators started the motor driven Auxiliary Feedwater (AFW) Pump 23 and secured the turbine-driven AFW pump. At 1118, Unit 2 operators exited the EOPs and returned to normal operating procedures. At 1713, Unit 2 operators started RCPs 21 Band 22A to restore forced RCS circulation.

On February 19, 2010, at 1205, operators verified two offsite power supplies were available, with the 13 kV Bus 21 energized from an alternate offsite source. On February 20,2010, at 2231, repairs on EDG 2B were completed and the diesel generator was declared operable. On February 19, 2010, at 1205, operators verified two offsite power supplies were available. At 0538 on February 21, 2010, the 500kV "Red Bus" was restored at 0550. Unit 2 achieved cold shutdown at 0500 on February 22, 2010. Additional details are provided in References 1 and 2.

Key Event Details. The following event details are significant to the modeling of this event analysis:

  • Loss of power to the Unit 2 non-safety related buses resulted in loss of the normal RCS heat removal path (Le., main feedwater pumps, circulating water pumps, and condenser). Operators used the turbine driven auxiliary feedwater pump and atmospheric steam dump valves for decay heat removal.

EDG 2B started, but tripped 15 seconds later due to a low lube oil pressure signal (due to a failed relay) and Bus 24 remained deenergized for approximately 33 minutes by 1

LER 318/10-001-01 aligning power from Alternate Feeder Breaker 152-2414. EDG 2B was repaired and declared operable on February 20th at 2231.

ANALYSIS RESULTS Change in Core Damage Probability. The calculated conditional core damage probability (CCDP) for this event is 1.8x10>s.

The Accident Sequence Precursor (ASP) Program acceptance threshold is a CCDP of 1x1 0>6 or the CCDP equivalent of an uncomplicated reactor trip with a non-recoverable loss of secondary plant systems (e.g., feedwater and condensate), whichever is greater. This CCDP equivalent for Calvert Cliffs, Unit 2 is 1.5x1O>s.

Dominant Sequence. The dominant accident sequence for is Loss of Condenser Heat Sink (LOCHS) Sequence 14 which contributes 81 % of the total internal events CCDP. Additional sequences that contribute greater than 1 % of the total internal events CCDP are provided in Appendix A.

The dominant sequence is shown graphically in Figures B-1 in Appendix B. The events and important component failures in LOCHS Sequence 14 are:

  • Once-through cooling (OTC) fails.

SAPHIRE 8 Report. The SAPHIRE 8 Worksheets (Appendix A) provide the following:

Summary of conditional event changes, including base and change case probabilities/freq uencies.

Event tree dominant results Dominant sequences (including CCDPs).

Sequence logic for all dominant sequences.

Referenced fault trees (including definitions).

Cutset report for each dominant sequence.

Referenced events (including definitions and probabilities for key basic events)

MODELING ASSUMPTIONS Analysis Type. The Revision 8.15 of the Calvert Cliffs, Unit 2 SPAR model (dated July 2010) was used for the analysis of this initiating event.

Analysis Rules. The ASP program uses Significance Determination Process results for degraded conditions when available. However, the ASP Program performs independent initiating event analysis when an initiator occurs.

Fault Tree Modifications. The following fault tree modifications were necessary to perform this event analysis:

2

LER 318/10-001-01

  • A new 'AND' gate and 'OR' were added to fault tree ACP-BUS-24 (4kV Bus 24 fails).

The new 'AND' gate ACP-BUS24-ALL (Offsite power to Bus 24 fails) was added below gate ACP-BUS24-1 (Loss ofpower to 4160kV Bus 24). The 'OR' gate ACP-BUS-24-3 (Loss of offsite power to 4kV Bus 24) [and its associated events] was moved under this new 'AND' gate. In addition, a new 'OR' gate ACP-BUS24-AL T (Alternate power to Bus 24 is unavailable) was added under gate ACP-BUS24-ALL. A new basic event ACP XHE-BUS24-RECOVERY (Operators fail to recover offsite power to Bus 24) was added to account for potential recovery of offsite power to Safety Bus 24. Along with this new basic event, a transfer gate ACP-13kVBUS-11 (13kV Service Bus 11 fails) was also added. See Figure B-2 in Appendix B for the modified fault tree.

  • A new flag event was added to the fault tree LOSC (Loss of RCP seal cooling). The current logic was moved under a new 'OR' gate LOSC5 and the new flag event FLAG LOSC (Flag Event-Loss of seal cooling) was inserted under the top event LOSC (RCP seal integrity maintained). See Figure B-3 in Appendix B for the modified fault tree.

This fault tree change (along with the following event tree post-processing rule) eliminates the potential credit for offsite power recovery to Safety Bus 24 during loss of RCP seal cooling sequences.

if FLAG-LOSC then Oe/eteEvent = ACP-XHE-BUS24-RECOVERY; AddEvent =ACP-XHE-BUS24-RECOVERY1; endif Key Modeling Assumptions. The following modeling assumptions and associated basic event modifications were required for this event analysis:

  • The initiating event was modeled as loss condenser heat sink because the loss of power to the Unit 2 non-safety related buses resulted in loss of the normal RCS heat removal path (Le., main feedwater pumps, circulating water pumps, and condenser)..

The frequency of IE-LOCHS (Initiating Event-Loss of Condenser Heat Sink) was set to 1.0; all other initiating event frequencies were set to zero.

  • Offsite power was lost to Safety Bus 24; the potential for recovery was credited. During the event, operators successfully recovered offsite power to Bus 24 in 33 minutes by closing Alternate Feeder Breaker 152-2414 (power is supplied to Bus 24 from the "Black" Bus through Service Transformer P-130000-1 and 13KV Service Bus 11).

The basic event was set ACP-BAC-LP-500KVR (500 kV Red Bus Fails) to TRUE to model the loss of offsite power to Safety Bus 24.

The basic event ACP-XHE-BUS24-RECOVERY was set to 5.0x10-3. This value was calculated using the SPAR-H Method (Reference 3).

  • This human failure event contains both diagnosis and action activities. Since operators would have enough time to perform the action, the nominal action human error probability of 1 x 1 0-3 was applied.
  • The following performance shaping factors (PSFs) were adjusted. All other PSFs were determined to be Nominal (i.e., x1).

3

LER 318/10~001~01

. Breaker 152-2414 needing to be shut to restore offsite power to 0.1

  • Safety Bus 24, the action portion time for recovery of offsite power to a vital bus is minimal << 5 minutes). Therefore, operators would have approximately 55 minutes to diagnose and go through the procedures. Thus, the diagnosis time available PSF was set to Extra Time i.e., xO.1.

The PSF for diagnosis stress is assigned a value of High Stress (i.e., x2) because the failure to recover the power to the Safety Bus 2

24 could lead directly to core damage during the postulated i sequences.

  • The PSF for diagnosis complexity is assigned a value of Moderately Complex (Le., x2) because operators would have to deal with
  • For the dominant and most time limiting sequence (LOCHS Sequence 14), approximately one hour is available for operators to restore offsite power to Safety Bus 24. With only Alternate Feeder 2

multiple equipment unavailabilities and the concurrent i actions/multiple procedures.

Time Available Stress Complexity Diagnosis HEP 4E-3 Action HEP 1e~

Adjusted Total HEP Ai.W The basic events FLAG-LOSC and ACP-XHE-BUS24-RECOVERY1 (Operators fail to recover offsite power to Bus 24 during LOSC) were set to TRUE because operators wouldn't have enough time to restore offsite power during a loss of RCP seal cooling to prevent seal failure (Le., approximately 13 minutes).

  • The basic event EPS-DGN-FS-2B (Diesel Generator 2B fails to start) was set to TRUE because EDG 2B failed to start.

To ensure that the common cause failure probabilities were calculated within SAPHIRE, the following basic events were modified as following:

  • The basic event EPS-DGN-FR-2B (Diesel Generator 2B fails to run) was set to 1.0.
  • The basic event EPS-DGN-TM-2B (Diesel Generator 2B unavailable due to test and maintenance) was set to TRUE.

All other safety systems responded as designed.

REFERENCES

1. Calvert Cliffs Nuclear Power Plant, Unit 2, ilLER 318/10-001 Reactor Trip Due to Failure of Protective Relay Circuitry," dated May 27,2010.
2. U.S. Nuclear Regulatory Commission, "Calvert Cliffs Nuclear Plant - NRC Special Inspection Report 05000317/2010006 and 05000318/2010006; Preliminary White Finding",

dated June 14, 2010.

3. Idaho National Laboratory, "NUREG/CR-6883: The SPAR-H Human Reliability Analysis Method," dated August 2005.

4

LER 318/10-001-01 Appendix A: SAPHIRE 8 Worksheets Summary of Conditional Event Changes Event Description Condo Nominal Value Value ACP-BAC-LP-500KVR 500 kV RED BUS FAILS TRUE 9.600E-6 ACP-XHE-BUS24-RECOVERY OPERATORS FAIL TO RECOVER OFFSITE 5.000E-3 O.OOOE+O POWER TO BUS 24 ACP-XHE-BUS24-RECOVERY1 OPERATORS FAIL TO RECOVER OFFSITE TRUE TRUE POWER TO BUS 24 EPS-DGN-FR-2B DIESEL GENERATOR 2B FAILS TO RUN 1.000E+0 2.118E-2 EPS-DGN-FS-2B DIESEL GENERATOR 2B FAILS TO START TRUE 5.000E-3 EPS-DGN-TM-2B DIESEL GENERATOR 2B UNAVAILABLE DUE TRUE 1.200E-2 TOT&M FLAG-LOSC FLAG EVENT-LOSS OF SEAL COOLING TRUE 1.000E+0 IE-LOCHS LOSS OF CONDENSER HEAT SINK 8

1.000E+0 8.000E-2 EPS-DGN-CF-ALL5FS CCF OF ALL FIVE DIESEL GENERATORS TO 6.232E-4 3.116E-6 START EPS-DGN-CF-2ABOCFS CCF OF DIESEL GENERATOR 2A, 2B AND 3.722E-3 1.861 E-5 SBOTO START EPS-DGN-CF-2ABOCFR CCF OF DIESEL GENERATOR 2A, 2B AND 6.665E-4 1.214E-4 SBOTO RUN EPS-DGN-CF-2ABFR COMMON CAUSE FAILURE OF UNIT 2 DIESEL 2.118E-2 3.282E-4 GENERATORS TO RUN EPS-DGN-CF-2ABFS COMMON CAUSE FAILURE OF UNIT 2 DIESEL 1.150E-2 5.750E-5 GENERATORS TO START EPS-DGN-CF-ALL5FR CCF OF ALL FIVE DIESEL GENERATORS TO O.OOOE+O 2.002E-5 RUN EPS-DGN-CF-1 B2ABFR CCF OF FAIRBANKS MORRIS DIESEL 6.665E-4 1.214E-4 GENERATORS 1 B, 2A & 2B TO RUN EPS-DGN-CF-1 B2ABFS CCF OF FAIRBANKS MORRIS DIESEL 3.722E-3 1.861 E-5 GENERATORS 1B, 2A, & 2B TO START DGS-OOS DGS IN T&M TRUE 4.714E-2

a.

All other initiating frequencies set to zero.

Dominant Sequence Results Only items contributing at least 1.0% to the total CCDP are displayed.

EVENT TREE SEQUENCE CCDP

% CONTRIBUTION DESCRIPTION LOCHS 14 1.454E-5 81.1%

IRPS, SGC, OTC LOCHS 02-9-4 2.105E-6 11.7%

fRPS, fSGC, IPORV, LOSC, RCPT, HPI LOCHS 15-09 5.920E-7 3.3%

RPS,/RCSPRESS, ISGC-A, IBORATION, PORV-A, HPI LOCHS 02-8-4 4.969E-7 2.8%

IRPS, ISGC, fPORV, LOSC, fRCPT, CBO, RSUB, RCPSI04, HPI Total 1.793E-5 100.0%

Referenced Fault Trees Fault Tree Description CBO CONTROLLED BLEEDOFF ISOLATED HPI HIGH PRESSURE INJECTION LOSC RCP SEAL INTEGRITY MAINTAINED OTC ONCE THROUGH COOLING A-1

LER 318/10-001-01 Fault Tree PORV-A RCPSIQ4 RCPT RPS RSUB SGC Description PORVs AND SRVs ARE CLOSED RCP SEALS FROM LOSS OF ALL COOLING REACTOR COOLANT PUMPS TRIPPED REACTOR TRIP REACTOR COOLANT SUBCOOLING MAINTAINED STEAM GENERATOR COOLING (AFW or MFW)

CumetReport-LOCHS14 Only items contributing at least 1% to the total are displayed.

CCDP TOTAL%

1.454E-5 100 1

1.200E-5 82.55 2

1.000E-6 6.88 3

1.768E-7 1.22 4

1.728E-7 1.19 5

1.728E-7 1.19 6

1.728E-7 1.19 Cumet Report - LOCHS 02-9-4 CUTSET Displaying 2753 of 2753 Cutsets.

IE-LOCHS,AFW-XHE-XM-HXNORM,AFW-XHE-XM-UQ IE-LOCHS,AFW-XHE-XM-F33,AFW-XHE-XM-F3WS IE-LOCHS,AFW-PIP-RP-5BCMNPIPE2,MFW-XHE-XM-LF IE-LOCHS,ACP-INV-FC-2Y01A1,AFW-XHE-XM-HX,AFW-XHE-XM-UQ IE-LOCHS,ACP-1NV-FC-2Y02A 1,AFW-XHE-XM-HX,AFW-XHE-XM-UQ IE-LOCHS,ACP-INV-FC-1 Y01A 1,AFW-XHE-XM-HX,AFW-XHE-XM-UQ Only items contributing at least 1% to the total are displayed.

CCDP TOTAL%

CUTSET 2.105E-6 100 Displaying 258 of 258 Cutsets.

4.800E-7 22.8 IE-LOCHS, CCW-HX21 STBY -220P,CCW-XHE-XM-KBI, EP S-XHE-XE DGOC45, R CP-XHE-XM-TRIP,SWS-FLAG-23SB22IS 2

1.798E-7 8.54 IE-LOCHS,CCW-23RUN-2221STBY,CCW-MDP-TM-21,CCW-P23-FACB,EPS XHE-XE-DGOC45,RCP-XHE-XM-TRIP 3

1.798E-7 8.54 IE-LOCHS,CCW-22RUN-2321 STBY,CCW-MDP-TM-21,CCW-P23-FACB,EPS XHE-XE-DGOC45,RCP-XHE-XM-TRIP 4

1.200E-7 5.7 IE-LOCHS, CCW-HX21 STBY -220P,CCW-XHE-XM-KBI,EPS-XHE-XE DGOC45,RCP-XHE-XM-TRI P,SWS-FLAG-22SB231 S 5

8.471E-8 4.02 IE-LOCHS, CCW-HX21 STBY -220P,CCW-XHE-XM-KBI,EPS-DGN-FR DGOC,RCP-XHE-XM-TRIP,SWS-FLAG-23SB22IS 6

8.250E-8 3.92 IE-LOCHS, CCW-HX22STBY -21 OP, CCW-XHE-XM-KBI,RCP-XHE-XM TRIP,SWS-HDR-TM-21 7

8.250E-8 3.92 IE-LOCHS,CCW-HX21STBY-220P,CCW-XHE-XM-KBI,RCP-XHE-XM TRIP,SWS-HDR-TM-22 8

6.988E-8 3.32 IE-LOCHS, CCW-HX22STBY -21 OP, EPS-DGN-FR-DGOC, RCP-XHE-XM TRIP,SWS-FLAG-23SB22IS,SWS-HDR-TM-21 9

6.988E-8 3.32 IE-LOCHS, CCW-HX21 STBY -220P,EPS-DGN-FR-DGOC,RCP-XHE-XM TRIP,SWS-FLAG-23SB22IS,SWS-HDR-TM-21 10 6.000E-8 2.85 IE-LOCHS, CCW-HTX-TM-21,CCW-HX21 STBY -220P,EPS-XHE-XE DGOC45,RCP-XHE-XM-TRIP,SWS-FLAG-23SB22IS 11 4.800E-8 2.28 IE-LOCHS,CCW-HX21 STBY -220P,CCW-XHE-XM-KBI,EPS-DGN-TM DGOC,RCP-XHE-XM-TR I P,SWS-FLAG-23SB22IS 12 3.960E-8 1.88 IE-LOCHS, CCW-HX22STBY -21 OP,EPS-DGN-TM-DGOC, RCP-XHE-XM TRIP,SWS-FLAG-23SB22IS, SWS-HDR-TM-21 13 3.960E-8 1.88 IE-LOCHS,CCW-HX21 STBY-220P, EPS-DGN-TM-DGOC,RCP-XHE-XM TRI P,SWS-FLAG-23SB22IS, SWS-HDR-TM-21 14 3.173E-8 1.51 IE-LOCHS,CCW-23RUN-2221STBY,CCW-MDP-TM-21,CCW-P23-FACB,EPS DGN-FR-DGOC,RCP-XHE-XM-TRIP A-2

LER 318/10*001*01 CCDP TOTAL %

CUTSET 15

3. 173E-S 1.51 IE-LOCHS,CCW-22RUN-2321STBY,CCW-MDP-TM-21,CCW-P23-FACB,EPS DGN-FR-DGOC,RCP-XHE-XM-TRIP 16 2.400E-S 1.14 IE-LOCHS,CCW-HX21 STBY-220P,CCW-XHE-XR-HTX21,EPS-XHE-XE DGOC45,RCP-XHE-XM-TRIP,SWS-FLAG-23SB221 S 17 2.11SE-S 1.01 IE-LOCHS,CCW-HX21 STBY-220P,CCW-XHE-XM-KBI,EPS-DGN-FR DGOC,RCP-XHE-XM-TRIP,SWS-FLAG-22SB23IS Cutset Report - LOCHS 15-09 Only items contributing at least 1 % to the total are displayed.

CCDP TOTAL %

CUTSET Total 5.920E-7 100 Displaying S of S Cutsets.

1 1.200E-7 20.27 IE-LOCHS,PPR-SRV-OO-2RV200LlQ,RPS-VCF-FO-MECH 2

1.200E-7 20.27 IE-LOCHS,PPR-SRV-OO-2RV201 UQ.RPS-VCF-FO-MECH 3

1.200E-7 20.27 IE-LOCHS,PPR-SRV-OO-2ERV404LIQ,RPS-VCF-FO-MECH 4

1.200E-7 20.27 IE-LOCHS.PPR-SRV-OO-2ERV402L1Q,RPS-VCF-FO-MECH 5

2.S00E-S 4.73 IE-LOCHS,PPR-SRV-OO-2RV200LIQ,RPS-VCF-FO-ELEC,RPS-XHE-XM SCRAM 6

2.S00E-S 4.73 IE-LOCHS.PPR-SRV-OO-2RV201 LlQ,RPS-VCF-FO-ELEC,RPS-XHE-XM SCRAM 7

2.S00E-S 4.73 IE-LOCHS,PPR-SRV-OO-2ERV404L1Q.RPS-VCF-FO-ELEC,RPS-XHE-XM SCRAM S

2.S00E-S 4.73 IE-LOCHS.PPR-SRV-OO-2ERV402LIQ,RPS-VCF-FO-ELEC,RPS-XHE-XM SCRAM Cutset Report - LOCHS 02*8-4 Only items contributing at least 1 % to the total are displayed.

CCDP TOTAL%

CUTSET 4.969E-7 100 Displaying 56 of 56 Cutsets.

1.219E-7 24.54 IE-LOCHS, CCW-HX21 STBY-220P,CCW-XHE-XM-KBI.EPS-XHE-XE DGOC45,RCS-MDP-LK-SEALS04,SWS-FLAG-23SB22IS 2

4.567E-S 9.19 IE-LOCHS,CCW-23RUN-2221STBY,CCW-MDP-TM-21,CCW-P23-FACB.EPS XHE-XE-DGOC45,RCS-MDP-LK-SEALS04 3

4.567E-S 9.19 IE-LOCHS, CCW-22RUN-2321 STBY,CCW-MDP-TM-21.CCW-P23-FACB,EPS XHE-XE-DGOC45,RCS-MDP-LK-SEALS04 4

3.04SE-S 6.13 IE-LOCHS,CCW-HX21STBY-220P,CCW-XHE-XM-KBI,EPS-XHE-XE DGOC45,RCS-MDP-LK-SEALS04,SWS-FLAG-22SB23IS 5

2.152E-S 4.33 IE-LOCHS, CCW-HX21 STBY -220P,CCW-XHE-XM-KBI, EPS-DGN-FR DGOC,RCS-MDP-LK-SEALS04,SWS-FLAG-23SB22IS 6

2.096E-S 4.22 IE-LOCHS,CCW-HX22STBY-21 OP,CCW-XHE-XM-KBI,RCS-MDP-LK SEALS04,SWS-HDR-TM-21 7

2.096E-S 4.22 IE-LOCHS, CCW-HX21 STBY -220P,CCW-XHE-XM-KBI, RCS-MDP-LK SEALS04, SWS-H DR-TM-22 S

1.775E-S 3.57 IE-LOCHS, CCW-HX22STBY -21 OP,EPS-DGN-FR-DGOC,RCS-MDP-LK SEALS04,SWS-FLAG-23SB22IS,SWS-HDR-TM-21 9

1.775E-S 3.57 IE-LOCHS,CCW-HX21 STBY-220P,EPS-DGN-FR-DGOC, RCS-MDP-LK SEALS04,SWS-FLAG-23SB22IS,SWS-HDR-TM-21 10 1.524E-S 3.07 IE-LOCHS,CCW-HTX-TM-21,CCW-HX21 STBY-220P,EPS-XHE-XE DGOC45,RCS-MDP-LK-SEALS04,SWS-FLAG-23SB22IS 11 1.219E-S 2.45 I E-LOCHS,CCW-HX21 STBY -220P,CCW-XHE-XM-KBI, EP S-DGN-TM DGOC,RCS-MDP-LK-SEALS04,SWS-FLAG-23SB22IS 12 1.006E-S 2.02 IE-LOCHS, CCW-HX22STBY -21 OP,EPS-DGN-TM-DGOC,RCS-MDP-LK SEALS04, SWS-FLAG-23SB22IS,SWS-HDR-TM-21 A-3

LER 318/10-001-01 CCDP TOTAL %

13 1.006E-B 2.02 14 B.060E-9 1.62 15 8.060E-9 1.62 16 6.096E-9 1.23 17 5.379E-9 1.08 18 5.0BOE-9 1.02 19 5.075E-9 1.02 20 5.075E-9 1.02 Referenced Events Event ACP-INV-FC-1Y01A1 ACP-INV-FC-2Y01 A 1 ACP-INV-FC-2Y02A 1 AFW-PIP-RP-5BCMNPIPE2 AFW-XHE-XM-F33 AFW-XHE-XM-F3WS AFW-XHE-XM-HX AFW-XHE-XM-HXNORM AFW-XHE-XM-UQ CCW-22RUN-2321 STBY CCW-23RUN-2221 STBY CCW-HTX-TM-21 CCW-HX21 STBY-220P CCW-HX22STBY-21 OP CCW-MDP-FS-21 CCW-MDP-TM-21 CCW-P23-FACB CCW-XHE-XM-KBI CCW-XHE-XR-HTX21 EPS-DGN-FR-DGOC EPS-DGN-FS-DGOC EPS-DGN-TM-DGOC EPS-XHE-XE-DGOC45 IE-lOCHS MFW-XHE-XM-lF CUTSET IE-lOCHS, CCW-HX21 STBY -220P,EPS-DGN-TM-DGOC,R CS-MDP-lK SEAlS04,SWS-FlAG-23SB22IS,SWS-HDR-TM-21 IE-lOCHS,CCW-23RUN-2221 STBY,CCW-MDP-TM-21, CCW-P23-FACB,EPS DGN-FR-DGOC,RCS-MDP-lK-SEAlS04 IE-lOCHS,CCW-22RUN-2321 STBY,CCW-MDP-TM-21,CCW-P23-FACB,EPS DGN-FR-DGOC,RCS-MDP-lK-SEAlS04 IE-lOCHS,CCW-HX21 STBY-220P,CCW-XHE-XR-HTX21, EPS-XHE-XE DGOC45,RCS-MDP-lK-SEAlS04,SWS-FLAG-23SB22IS IE-lOCHS,CCW-HX21STBY-220P,CCW-XHE-XM-KBI,EPS-DGN-FR DGOC,RCS-MDP-lK-SEAlS04,SWS-FLAG-22SB23IS IE-lOCHS,CCW-HX21 STBY -220P,CCW-XHE-XM-KBI,EPS-DGN-FS DGOC,RCS-MDP-lK-SEAlS04,SWS-FLAG-23SB22IS IE-lOCHS,CCW-23RUN-2221 STBY,CCW-MDP-FS-21,CCW-P23-FACB,EPS XHE-XE-DGOC45,RCS-MDP-lK-SEAlS04 IE-lOCHS,CCW-22RUN-2321 STBY, CCW-MDP-FS-21, CCW-P23-F ACB, EPS XHE-XE-DGOC45,RCS-MDP-lK-SEAlS04 DESCRIPTION INVERTER 1Y01A-1 FAilS DURING OPERATION INVERTER 2Y01A-1 FAilS DURING OPERATION INVERTER 2Y02A-1 FAilS DURING OPERATION 2PIPECOMMON AFW - COMMON DISCH HDR EARLY PIPE BREAK (PSA)

OPERATIONS ALIGNS lONG TERM AFW ON PUMP CAVITATION WITH INDICATION AVAILABLE OPERATIONS FAilS TO ALIGN lONG TERM AFWWITH All INDICATION AVAILABLE OP FAilS TO CONTROL AFW FLOW - SPAR OP FAilS TO CONTROL AFW FLOW - SPAR OPS ERRONEOUSLY UNDERFlllS S/G DURING lOSS OF FLOW CONTROL CCW MDP-22 RUNNING 23&21 IN STANDBY CCW MDP-23 RUNNING 21&22 IN STANDBY CCW HEAT EXCHANGER 21 IN T & M CCW HTX-21 IN STANDBY CCW HTX-22 IN OPERATION CCW HTX-22IN STANDBY CCW HTX-21 IN OPERATION FAilURE OF CCW MDP-21 TO START CCW MDP-21 UNAVAILABLE DUE TO T & M CCW PUMP 23 ELECTRICAllY ALIGNED TO FACILITY B OPS FAilS TO PLACE STANDBY CCW HX IN SERVICE WIIN 10 MINUTES OF HX FAilURE PRIOR TO TRIP OPERATOR FAilS TO RESTORE CCW HTX-21 AFTER T & M SBO DIESEL GENERATOR DGOC FAilS TO RUN SBO DIESEL GENERATOR DGOC FAilS TO START SBO DIESEL GENERATOR DGOC UNAVAILABLE DUE TO T & M OPERATIONS ALIGN THE OC DG IN 45 MINS lOSS OF CONDENSER HEAT SINK OPER ESTABLISHES MANUAL ADV CTRl AND INIT lOW PRESS FEED USING CONDENSATE WITHIN 45 MIN OF lOSS Probability 1.200E-4 1.200E-4 1.200E-4 4.420E-6 1.000E-3 1.000E-3 1.200E-1 1.000E-3 1.200E-2 3.330E-1 3.330E-1 2.500E-3 5.000E-1 5.000E-1 2.000E-3 1.BOOE-2 5.000E-1 2.000E-2 1.000E-3 2.118E-2 5.000E-3 1.200E-2 1.200E-1 1.000E+0 4.000E-2 A-4

LER 318/10-001-01 Event PPR-SRV-00-2ERV402LIQ PPR-SRV-00-2ERV404L1Q PPR-SRV-00-2RV200LlQ PPR-SRV-00-2RV201 UQ RCP-XHE-XM-TRIP RCS-MDP-LK-SEALS04 RPS-VCF-FO-ELEC RPS-VCF-FO-MECH RPS-XHE-XM-SCRAM SWS-FLAG-22SB23IS SWS-FLAG-23SB22IS SWS-HDR-TM-21 SWS-HDR-TM-22 DESCRIPTION Probability 2ERV 402 FAILS TO RECLOSE AFTER PASSING LIQUID 1.000E-1 2ERV 2 FAILS TO RECLOSE AFTER PASSING LIQUID 1.000E-1 SRV 2RV-200 FAILS TO RECLOSE AFTER PASSING LIQUID 1.000E-1 SRV RV-201 FAILS TO RECLOSE AFTER PASSING LIQUID 1.000E-1 OPERATIONS FAILS TO TRIP THE RCPS WHEN THE CCW S.000E-4 PUMPS WERE NOT AVAIL FOR RECOVERY - ASA - U2 TRIP NEOP8 RCP SEALS FAIL WIO COOLING AND INJECTION 1.270E-4 ELECTRICAL (UV & ST) RPS FAILURE TO OPEN TRIP CIRCUIT 1.400E-S BREAKERS CONTROL ROD ASSEMBLIES FAIL TO INSERT 1.200E-6 OPS FAILS TO MANUALLY TRIP THE RX WITHIN S MINUTES 2.000E-2 FOLLOWING THE FAILURE OF RPS AND DSS SW PUMP 23 IN-SERVICE W1TH 221N STAND-BY (PSA) 2.000E-1 SW PUMP22 IN-SERVICE WITH 231N STAND-BY (PSA) 8.000E-1 SW HDR 21 IS UNAVAILABLE WHEN UNIT 1 IS AT-POWER 1.650E-2 (PSA)

SW HDR 22 IS UNAVAILABLE WHEN UNIT 2 IS AT-POWER 1.6S0E-2 (PSA)

A-5

LER 318/10-001-01 Appendix B: Key Event Tree and Modified Fault Trees

'--0----0---10 Oi----{)---I ;--

L...-{}---OI---iO}---(O)---iOI---(O)---iOI---iO}---(OI---I Figure B-1. Calvert Cliffs, Unit 2 LOCHS event tree.

Figure B-2. Calvert Cliffs, Unit 2 modified ACP-8US-24 fault tree.

8-1

LER 318/10-001-01 Figure B-3. Calvert Cliffs, Unit 2 modified LOSC fault tree.

8-2

G. Gellrich

- 2 The enclosure containing the final analysis report is provided for your information.

Please contact me at 301-415-1364 if you have any questions.

Sincerely, Ira!

Douglas V. Pickett, Senior Project Manager Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-318

Enclosure:

Final Precursor Analysis cc w/encl: Distribution via Listserv Distribution PUBLIC LPL1-1 rtf RidsNrrDorlLpl1-1 RidsNrrPMCalvertCliffs RidsNrrLASLittie RidsOgcMailCenter RidsAcrsAcnwMailCenter GDeMoss, RES/ORA RidsRegion'l MailCenter GDentel, R1 ADAMS Package: Accession No. ML112660489 Transmittal Letter: Accession No. ML112660497

Enclosure:

Final Precursor Analysis: Accession No. ML112560283 OFFICE LPL 1-1/PM LPL 1-1/LA NAME DPickett SLittie ABaxter for DATE

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