IR 05000247/2002010

Final ASP Analysis - Indian Point 2 (IR 050002472002010)

ML20112J068
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Site:	Indian Point
Issue date:	05/12/2020
From:	Christopher Hunter NRC/RES/DRA/PRB
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References
IR 2002010
Download: ML20112J068 (14)

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Attachment 1

IR No. 247/02-010 Final Precursor Analysis Accident Sequence Precursor Program --- Office of Nuclear Regulatory Research Indian Point, Unit 2 Moderate degradation of control room west wall could allow smoke and gases to penetrate the control room in the event of a turbine building fire

'DWH July 19,

2002

,5 50-247/02-

0HDQ &'3 [

7.1 x 10-6 April 30, 2003 Condition Summary On July 19, 2002, the NRC completed an inspection of selected areas of the Indian Point Unit 2 facility (Ref. 1). The inspection identified a moderate degradation of the control room west wall fire prior to February 2002, in that there were passages in the wall that could allow smoke and gases to infiltrate into the control room in the event of a turbine building fire and could cause a control room evacuation and use of alternative safe shutdown systems (Ref. 1).

Cause The west wall did not conform to the 3-hour fire barrier design requirement Recovery Opportunity The postulated fire in the turbine building, applicable to the turbine generator lube oil system or the main feedwater pump lube oil system, could generate sufficient smoke to cause infiltration into the control room and its subsequent evacuation after a successful reactor trip/turbine tri The recovery of one train of safe shutdown equipment using the alternate safe shutdown system (ASSS) would prevent core damag Analysis Results

Importance The risk significance of the control room evacuation with the recovery of one train of safe shutdown equipment with the ASSS is determined using the SPAR Rev. 3i model for Indian Point 2 (Ref.2). The analyses was with the transient initiating frequency (IE-TRANS) replaced by the combined smoke frequency of the turbine generator lube oil fires and main feedwater pump lube oil fire This method is similar to that outlined in NUREG/CR-6544, Development of a Methodology for Analyzing Precursors for Earthquake-Induced or Fire-Induced Accident Sequences, Section 3.7 (Re ). For this analysis, the increase in point estimate change in conditional core damage probability ( CDP) is 7.4x10-6 and the mean CDP is 7.1x10- The uncertainty about the mean is:

5% bound, 1.3x10-7 and 95% bound, 2.8x10-5.

The Accident Sequence Precursor (ASP) program acceptance threshold is an importance ( CDP) of 1x10-6.

Dominant sequence (TRANS)

IR No. 247/02-010 The dominant sequence is Transient Sequence 1 The events and important component failures in this sequence include:

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Reactor trips successfully during transient

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No or Insufficient AFW flow

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Failure of main feedwater system during transient

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Successful Bleed portion of feed and bleed

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Adequate flow from HPI system

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Failure of secondary cooling

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No or insufficient flow from HPR system

Results tables

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Table 1 provides the importance values for the dominant sequences.

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Table 2a provides the event tree sequence logic for the dominant sequence.

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Table 2b defines the nomenclature used in Table 2a.

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Table 3 provides the additional cut sets for the dominant sequence.

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Table 4 provides the definitions and probabilities for selected events.

Modeling Assumptions

ASP analysis approach Condition duratio The control room west wall barrier was in a degraded condition since for a period greater than one yea

SPAR model used in the analysis The Revision 3i (interim) of the Indian Point 2 Standardized Plant Analysis Risk (SPAR)

model (Ref. 2) was used for this assessmen For this initiating event analysis, the IE-TRANS frequency is replaced with the smoke frequency (5.6E-3) and all other initiating event frequencies are set to zer External events are not included in this analysis.

Smoke-induced analysis considerations The smoke-induced analysis is based on NUREG/CR-6544 (Ref. 3). For this analysis the control room is assumed to be evacuated after successful reactor trip and one train of safe shutdown equipment is operated using the ASS The IE-TRANS frequency is replaced with the smoke frequency, based on smoke produced from turbine generator lube oil fires, severe smoke events resulting in turbine building evacuation, and smoke produced from main feedwater pump lube oil fire These events were evaluated as severe enough to possibly result in smoke ingestion into the control room and subsequent control room evacuation.

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Initiating Smoke Frequency - The initiating smoke frequency (Fis) was developed from NRC Report RES/OERAB/S02-01 database (Ref. 4) for power operation fire

IR No. 247/02-010 events (1986-1999 with updates through 2001). For Indian Point 2, the smoke frequency (FS) used was 5.6 x 10-3 based on:

Fis =

(No. of Turbine Generator lube oil fires + No. Turbine Building smoke evacuation events + Jeffreys noninformative prior) ÷ No. Turbine Generators x No. of reactor-years of power operation for the period) +

(No. of main feedwater pump lube oil fires ÷ No. Main feedwater pumps x No. of reactor-years of power operation for the period).

Fis =

(5 +1 ) + 2 + Jeffreys Prior = 8 +.5 = 5.6 x 10-3

(1 x 1310) (2.34)(1310)

1529 Note: The number of smoke events in the numerator was maintained and the denominator (component-years) was adjusted/weighted before a Bayesian update was made using a Jeffreys noninformative prior (0.5 smoke events).

Unique system considerations The plant design provides an alternate safe shutdown system to shut the plant down with one train of safe shutdown equipment in the event of control room evacuation.

Modifications to event tree and fault tree models

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The event trees were not modified.

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The fault trees were modified to include/clarify the recovery of one train of safe shutdown equipment, as applicable, using the ASSS (see Figures 1A-1E).

Initiating event probability changes The TRANS initiating event (IE-TRANS) frequency was replaced by the smoke frequency (5.6 x 10-3). All other initiating events frequencies were set to zer Figure 2 shows the event tree for the smoke-induced transient analysis dominant sequence.

Base event probability changes Table 4 provides the basic events that were modified to reflect the event condition being analyze Equipment not controlled from the ASSS is assumed be inoperable and assigned a value of 1.0 in the model.

Initiating event assessment probability changes

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AFW Motor-Driven Pump 23 Fails to Run (AFW-MDP-FR-23). This event was set to 1.0.

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AFW Motor-Driven Pump 23 Fails to Start (AFW-MDP-FS-23). This event was set to IR No. 247/02-010

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Operator Fails to Recover AFWMDP 23 (Fails to Run) (AFW-XHE-XL-MDP23).

This event was set to 1.0.

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Failure of CCW MDP 22 (CCW-MDP-FC-22). This event was set to 1.0.

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Failure of CCW MDP-21 to Run (CCW-MDP-FR-MDP21). This event was set to 1.0.

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Failure of CCW MDP 22 to Run (CCW-MDP-FR-MDP22). This event was set to 1.0.

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Failure of CCW MDP-21 to Start (CCW-MDP-FS-MDP21). This event was set to 1.0.

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Failure of CCW MDP-22 to Start (CCW-MDP-FS-MDP22). This event was set to 1.0.

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Failure of Positive Displacement Pump 22 (CVC-PDP-FC-22). This event was set to 1.0.

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Failure of Positive Displacement Pump 21 to Run (CVC-PDP-FR-21). This event was set to 1.0.

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Failure of Positive Displacement Pump 22 to Run (CVC-PDP-FR-22). This event was set to 1.0.

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Failure of Positive Displacement Pump 22 to Start (CVC-PDP-FS-22). This event was set to 1.0.

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Failure of HPI MDP-22 (HPI-MDP-FC-22). This event was set to 1.0.

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Failure of HPI MDP-23 (HPI-MDP-FC-23). This event was set to 1.0.

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Failure of HPI MDP-22 (HPI-MDP-FC-22). This event was set to 1.0.

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RHR MDP-22 Fails (RHR-MDP-FC-22). This event was set to 1.0.

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RHR MDP-22 Fails to Run (RHR-MDP-FR-22). This event was set to 1.0.

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RHR MDP-22 Fails to Start (RHR-MDP-FS-22). This event was set to 1.0.

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Failure of SWS MDP 21 to Run (SWS-MDP-FR-21). This event was set to 1.0.

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Failure of SWS MDP 22 to Run (SWS-MDP-FR-22). This event was set to 1.0.

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Failure of SWS MDP 25 to Run (SWS-MDP-FR-25). This event was set to 1.0.

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Failure of SWS MDP 26 to Run (SWS-MDP-FR-26). This event was set to 1.0.

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Failure of SWS MDP 21 to Run (SWS-MDP-FR-MDP21). This event was set to 1.0.

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Failure of SWS MDP 22 to Run (SWS-MDP-FR-MDP22). This event was set to 1.0.

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Failure of SWS MDP 25 to Run (SWS-MDP-FR-MDP25). This event was set to 1.0.

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Failure of SWS MDP 26 to Run (SWS-MDP-FR-MDP26). This event was set to 1.0.

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Failure of SWS MDP 21 to Start (SWS-MDP-FS-21). This event was set to 1.0.

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Failure of SWS MDP 22 to Start (SWS-MDP-FS-22). This event was set to 1.0.

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Failure of SWS MDP 25 to Start (SWS-MDP-FS-25). This event was set to 1.0.

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Failure of SWS MDP 26 to Start (SWS-MDP-FS-26). This event was set to 1.0.

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Failure to Align Alternate Safe Shutdown Power Supplies (SSS-XHE-XE-Align).

This event was set to 1.0E-002.

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Transient Initiating Event (IE-TRANS). This initiating event was set to 5.6E-003.

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All other initiating events were set to zero.

Model update No updates were made to the SPAR model, except clarification of fault trees for the alignment of the alternate safe shutdown system (see Figures 1A-1E).

IR No. 247/02-010 References 1.

EA-02-162, Indian Point Unit 2 - NRC Supplemental/Problem Identification and Resolution Inspection Report No. 50-247/02-010n Number, dated August 28, 2002.

2.

J. K. Knudsen and R. F. Buell, Standardized Plant Analysis Risk Model for Indian Point Unit 2, Revision 3i, Idaho National Engineering and Environmental Laboratory, May 2002.

3.

R.W.Budnitz, et al., Development of a Methodology for Analyzing Precursors to Earthquake-Induced and Fire-Induced Accident Precursors, NUREG/CR-6544, U.S.

Nuclear Regulatory Commission, Washington, DC, April 1998.

4.

J.R. Houghton and D. M. Rasmuson, NRC Report RES/OERAB/S02-01, Fire Events Update of U.S. Operating Experience, 1986-1999, U.S. Nuclear Regulatory Commission, Washington, DC, January 200 IR No. 247/02-010

Table Conditional Probability Associated with Highest Probability Sequence (Point Estimate)

Event Tree Sequence Conditional Core Damage probability (CCDP)

TRANS

6.7E-06 TOTAL All Sequences 7.4E-06 Table 2 Event tree sequence logic for dominant sequence Event Tree Name Sequence no.

Logic (/ denotes success; see Table 2b. for top event names TRANS

/RT, AFW, MFW-T, /BLEED, /HPI, SGCOOL, HPR Table 2 Definitions of sequence logic elements listed in Table 2a.

AFW No or insufficient AFW flow BLEED Failure of Bleed portion of Feed and Bleed cooling SGCOOL Failure of secondary cooling HPI No or insufficient flow from HPI system HPR No or insufficient HPR flow RHR No or insufficient flow from RHR system RT Reactor fails to trip during transient Table 3 Conditional cut sets for dominant sequence (Point Estimate)

Event tree: TRANS Sequence 19 CCDP Percent Contribution Minimum cut sets1 1.6E-006 23.5 PCS-XHE-XO-SEC SSS-XHE-XE-ALIGN AFW-MDP-FR-23 AFW-XHE-XL-MDPFR23 AFW-TDP-FR-22 SWS-MDP-FR-21 SWS-MDP-FR-22 1.6E-006 23.5 PCS-XHE-XO-SEC SSS-XHE-XE-ALIGN AFW-MDP-FR-22 AFW-XHE-XL-MDPFR23 AFW-TDP-FR-22 CCW-MDP-FR-MDP21 CCW-MDP-FC-MDP22 6.7E-006 Total2 NOTES:

1.

See Table 4 for definitions and probabilities for the base events.

2.

Total CDP includes all other cut sets (including those not shown in this table).



IR No. 247/02-010 Table Definitions and probabilities for modified and dominant basic events Event name Description Probability/

Frequency Modified IE-LDC22 LOSS OF DC Bus 22 INITIATING EVENT FREQUENCY 0.00 YES1 IE-LLOCA LARGE LOSS OF COOLANT ACCIDENT INITIATING EVENT 0.00 YES1 IE-LOCCW LOSS OF COMPONENT COOLING WATER INITIATING EVENT 0.00 YES1 IE-LOop LOSS OF OFFSITE POWER INITIATING EVENT 0.00 YES1 IE-LOSWS LOSS OF SERVICE WATER INITIATING EVENT 0.00 YES1 IE-MLOCA MEDIUM LOSS OF COOLANT ACCIDENT INITIATING EVENT 0.00 YES1 IE-RHR-DIS-V RHR DISCHARGE ISLOCA OCCURS WITH REACTOR AT POWER OVER 1 YEAR 0.00 YES1 IE-RHR-SUC-V RHR SUCTION ISLOCA INITIATING EVENT 0.00 YES1 IE-SGTR STEAM GENERATOR TUBE RAPTURE 0.00 YES1 IE-SI-CLDIS-V SI COLD LEG ISLOCA INITIATING EVENT 0.00 YES1 IE-SI-HLDIS-V SI HOT LEG ISLOCA INITIATING EVENT 0.00 YES1 IE-SLOCA SMALL BREAK LOSS OF COOLANT ACCIDENT INITIATING EVENT 0.00 YES1 IE-TRAN INITIATING EVENT-TRANSIENT 5.6E-03 YES1 AFW-MDP-FR-23 AFW MOTOR-DRIVEN PUMP 23 FAILS TO RUN 1.00 YES2 AFW-MDP-FS-23 AFW MOTOR-DRIVEN PUMP 23 FAILS TO START 1.00 YES2 AFW-XHE-XL-MDPFR23 OPERATOR FAILS TO RECOVER MDP23 1.00 YES2 CCW-MDP-FC-MDP22 FAILURE OF CCW MDP22 1.00 YES2 CCW-MDP-FR-MDP21 FAILURE OF CCW MDP-21 TO RUN 1.00 YES2 CCW-MDP-FR-MDP22 FAILURE OF CCW MDP-22 TO RUN 1.00 YES2 CCW-MDP-FS-MDP21 FAILURE OF CCW MDP-21 TO START 1.00 YES2 CCW-MDP-FS-MDP22 FAILURE OF CCW MDP-22 TO START 1.00 YES2 CVC-PDP-FC-22 FAILURE OF POSITIVE DISPLACEMENT PUMP 22 1.00 YES2 CVC-PDP-FR-21 FAILURE OF POSITIVE DISPLACEMENT PUMP 21 TO RUN 1.00 YES8 CVC-PDP-FR-22 FAILURE OF POSITIVE DISPLACEMENT PUMP 22 TO RUN 1.00 YES8 CVC-PDP-FS-22 FAILURE OF POSITIVE DISPLACEMENT PUMP 22 TO START 1.00 YES2 HPI-MDP-FC-22 FAILURE OF HPI MDP-22 1.00 YES2 HPI-MDP-FC-23 FAILURE OF HPI MDP-23 1.00 YES2 RHR-MDP-FC-22 RHR MDP-22 FAILS 1.00 YES2 RHR-MDP-FR-22 RHR MDP-22 FAILS TO RUN 1.00 YES2

Event name Description Probability/

Frequency Modified



IR No. 247/02-010 RHR-MDP-FS-22 RHR MDP-22 FAILS TO START 1.00 YES2 SWS-MDP-FR-21 FAILURE OF SWS MDP-21 TO RUN 1.00 YES2 SWS-MDP-FR-22 FAILURE OF SWS MDP-22 TO RUN 1.00 YES2 SWS-MDP-FR-25 FAILURE OF SWS MDP-25 TO RUN 1.00 YES2 SWS-MDP-FR-26 FAILURE OF SWS MDP-26 TO RUN 1.00 YES2 SWS-MDP-FR-MDP21 FAILURE OF SWS MDP-21 TO RUN 1.00 YES2 SWS-MDP-FR-MDP22 FAILURE OF SWS MDP-22 TO RUN 1.00 YES2 SWS-MDP-FR-MDP25 FAILURE OF SWS MDP-25 TO RUN 1.00 YES2 SWS-MDP-FR-MDP26 FAILURE OF SWS MDP-26 TO RUN 1.00 YES2 SWS-MDP-FS21 FAILURE OF SWS MDP-21 TO START 1.00 YES2 SWS-MDP-FS22 FAILURE OF SWS MDP-22 TO START 1.00 YES2 SWS-MDP-FS25 FAILURE OF SWS MDP-25 TO START 1.00 YES2 SWS-MDP-FS26 FAILURE OF SWS MDP-26 TO START 1.00 YES2 SWS-XHE-XE-ALIGN FAILURE TO ALIGN ALTERNATE SAFE SHUTDOWN SYSTEM 1.0E-02 YES2 AFW-TDP-FR-22 AFW TURBINE DRIVEN PUMP FAILS TO RUN 2.8E-02 NO PCS-XHE-XO-SEC OPERATOR FAILS TO ESTABLISH SECONDARY COOLING 2.0E-01 NO Notes:

1.

The TRANS initiating event frequency was replaced with the smoke frequenc All other initiating event frequencies were set to zero.

2.

Basic events were changed to reflect condition being analyze.

AFW-MDP21 AFW-CKV-CC-DIS21 AFW-CKV-CC-SUC21 AFW-MDP-CF-AB AFW-MDP-TM-21 AFW-MDP21-FR-F AFW-MDP-FR-21 AFW-XHE-XL-MDPFR21 AFW-MDP21-FS-F AFW-MDP-FS-21 AFW-XHE-XL-MDPFS21 AFW-MDP21-PWR SSS-XHE-XE-ALIGN DIV-3A-AC DIV-23-DC DIVISION BUS DC-23 DC POWER FAILS AFW MDP 21 FAILS TO RUN AFW MDP 21 FAILS TO START FAILURE OF POWER TO AFW MDP 21 FAILURE O F AFW MDP-21 DIVISION 3A AC POWER FAILS AFW MDP 21 DISCH CHECK VALVE FAILS TO OPEN OPERATO R FAILS TO RECOVER AFW MDP 21 (FAILS TO RUN)

OPERATOR FAILS TO RECOVER AFW MDP 21 (FAILS TO START)

AFW MOTOR-DRIVEN PUMP 21 FAILS TO START AFW MOTOR-DRIVEN PUMP 21 FAILS TO RUN AFW MDP 21 UNAVAILABLE DUE TO TEST AND MAINTENANCE AFW MDP 21 SUCTION CHECK VALVE FAILS TO OPEN FAILURE TO ALIG N ALTERNATE SAFE SHUTDOWN POWER SUPPLIES COMMON CAUSE FAILURE OF AFW MOTOR DRIVEN PUMPS FIGURE 1A

 IR No. 247/02-010 SENSITIVE - NOT FOR PUBLIC DISCLOSURE IR No. 247/02-010

C CW C CW-1 CCW-HTX CCW -MDP-CF-FRALL CCW-TN K-FC-SURGE CCW-MDP21 CC W-MDP-FR-MD P21 D IV-5A-AC CCW-MDP21-1 CCW -MDP21-3 CCW-MDP21-2 LOSP LOSP-5A CCW -MDP-C F-FSALL C CW-MDP-FS-MDP21 CCW-CKV-CC-MDP21 CCW-CKV-CF-MDPS DIV-21-DC CCW-MD P22 CCW -MDP-FC-MDP22 DI V-2A-AC CCW-MD P-CF-FSALL CCW -CKV-CF-MDPS DIV-22-DC CCW-MD P-TM-MDP22 C CW-XHE-XR-MDP22 C CW-MDP23 CC W-MDP-FC-MDP23 DIV-6A-AC CCW -MDP-CF-FSALL C CW-CKV-CF-MDPS DIV-24-DC CCW-MDP-TM-MD P23 CCW-XHE-XR-MDP23 CCW -HE CCW -MDP23-PWR SSS-XH E-XE-ALI GN FAILURE OF CCW TO PROVIDE COOLING FAILURE OF CCW HEAT EXCHANGERS FAILURE OF CCW MDPs CCF OF ALL CCW MDPs TO RUN FAILURE OF CCW S URGE TANK LOSS OF OFFS ITE POWER HOUSE EVENT LOSS OF DIV 5A OFFSITE POW ER FLAG FA ILURE OF CCW MDP-21 FAILURE OF CCW MDP -21 TO RUN DIVISION 5A A C POW ER FAILS FAILURE OF CCW MDP-21 DURING LOOP CCW MDP-21 FAILURES TO START CCW MDP-21 LOOP FLA GS CCF OF ALL CCW MDPs TO START FAILURE OF CCW MDP -21 TO START FAILURE OF CCW MDP-21 DISCHARGE CHECK VALV E CCF OF CCW MDPs DISCHARGE CHECK VALVE S DIVIS ION BUS DC-21 DC POWE R FAILS FAILURE OF CCW MDP -22 FAILURE OF CCW MDP-22 DIVISION 2A A C POWER FAILS CCF OF ALL CCW MDPs TO START CCF OF CCW MDPs DISCHARGE CHECK VALVES DIVISION BUS DC-22 DC P OW ER F AILS CCW MDP-22 UNA VAILABLE DUE TO T & M OPERATOR FAILS TO RESTORE CCW MDP-22 AFTE R T & M FAILURE OF CCW MDP -23 FAILURE OF CCW MDP -23 DIVISION 6A AC POW ER FAILS CCF OF ALL CCW MDPs TO START CCF OF CCW MDPs DISCHARGE CHECK VALVES DIV ISION BUS DC-24 DC POWER FAILS CCW MDP-23 UNA VAILABLE DUE TO T & M OPERATOR FA ILS TO RESTORE CCW MDP-23 A FTER T & M CCW HOUS E EVENT FAILURE OF POWE R TO CCW MDP 23 FAILURE TO ALIGN ALTERNATE SAFE SHUTDOW N POW ER SUPPLIES FIGURE 1B 1 IR No. 247/02-010 SENSITIVE - NOT FOR PUBLIC DISCLOSURE IR No. 247/02-010

RCP-CVC RC P-CVC -2 CVC -PDP-CF-FRALL CVC-PD P-FR-21 DIV-5A-AC R CP-CVC-21 CVC-XHE-XM-BCKCW C CW R CP-CVC-3 C VC-CKV-CF-2223 CVC-PDP-CF-FRALL C VC-PD P-CF-FS223 CVC-PDP-FC -22 DIV-3A-AC RCP-CVC-22 C VC-XH E-XM-BCKCW CCW RCP-CVC-4 C VC-CKV-CF-2223 CVC-PDP-CF-FRALL CVC-PDP-CF-FS223 CVC-PDP-FC-23 RCP-CVC-23 CVC-XHE-XM-BCKCW CCW RCP-CVC-5 SSS-XHE-XE-ALIGN DIV-6A-AC FAILURE OF CVC PUMP 23 SEAL COOLING FAILURE OF CVC PUMP S EAL COOLING FAILURE OF CHARGING PUMP 23 FAILURE OF CHARGING PUMP 22 FAILURE OF CHARGING PUMP 21 FAILURE OF CHARGING PUMPS TO PROVIDE RCP COOLING FAILURE OF CCW TO PROVIDE COOLING FAILURE OF CCW TO PROVIDE COOLING FAILURE OF CCW TO P ROVIDE COOLING FAILURE OF P DP 22 LUBE OIL COOLING DIV ISION 5A AC POWER FAILS DIV ISION 6A A C POWE R FAILS FA ILURE OF POWER TO CHA RGING P UMP

DIVISION 3A AC POWER FAILS CCF OF CVC PUMP 22/23 DISCH CHECK VALVES CCF OF CVC PUMP 22/23 DISCH CHECK VALVES CCF OF POSITIVE DISP LACEME NT PUMPS 22/23 TO START CCF OF POSITIVE DISPLACEMENT PUMP S 22/23 TO START CCF OF P OSITIVE DISPLACEMENT PUMPS TO RUN CCF OF POSITIVE DISPLA CEMENT PUMPS TO RUN CCF OF POSITIVE DIS PLACEMENT PUMPS TO RUN FAILURE OF POSITIVE DISPLACEMENT PUMP 23 FA ILURE TO ALIGN ALTERNATE SAFE SHUTDOWN POW ER SUPPLIE S FAILURE OF POSITIVE DISPLACE MENT PUMP 22 OPERA TOR FAILS TO ALIGN CITY W ATER F OR SEAL COOLING OPERATOR FAILS TO A LIGN CITY WATE R FOR SE AL COOLING OPERATOR FAILS TO ALIGN CITY WA TER FOR SEAL COOLING FA ILURE OF POSITIVE DIS PLACEMENT PUMP 21 FIGURE 1C 1 IR No. 247/02-010

SWS-MDP23 SWS-CKV-CC-SW23 SWS-CKV-CF-ALL SWS-CKV-CF-SWNESS SWS-MDP-CF-FSALL SW S-MDP-FR-23 SWS-MDP-FS-23 SWS-MDP-TM-23 SWS-XHE-XM-MDP SWS-XHE-XR-MDP23 DIV-24-DC SW S-MDP23-PWR SSS-XHE-XE-ALIG N DIV-6A-AC FA ILURE OF SW S MDP-23 DI VISION BUS DC-2 4 DC POW E R FA ILS DI VISION 6A AC POW ER FA ILS FAIL URE OF POW ER TO SW S M DP 23 OPE RATOR FA ILS T O RE STORE S W S MDP 23 A FTE R T & M S W S MDP 23 UNAV AILA BLE DUE T O T & M FA ILURE OF SW S P UMP S 23 DIS CH ARGE CHE C K VA LVE FA ILURE OF SW S MDP 23 TO S TAR T FAILU RE OF S W S MDP 23 TO RUN CC F OF SW S PUM PS TO STA RT C CF OF SW S P UMP S D IS CHARGE C HECK V ALVE S CCF OF S W S PUMPS 21/22 /23 DI SCHA RGE CHE CK VA LVE S FA ILURE TO ALIGN ALT ER NA TE S AF E S HUTDOW N P OW E R S UPP LIES OPE RA TOR FAI LS TO S TART S W S MD PS GIV EN A LOOP FIGURE 1D 1 IR No. 247/02-010 SENSITIVE - NOT FOR PUBLIC DISCLOSURE IR No. 247/02-010

S WS -ESS EN S WS-HE S WS -MDP-C F-FRA LL S WS -MDP-CF-SW ESS SWS -STR-CF-ALL SWS -STR-CF-SW ESS S WS -ESS -1 S WS -MDP24 S WS-MDP-FR-24 S WS-MDP24-1 S WS-MDP24-2 S WS-CKV -CC-SW24 S WS-CKV -CF-A LL S WS -CKV -CF-S WES S S WS-MDP-CF-FSALL S WS -MD P-FS -24 DIV-21-DC S WS-MDP24-3 LOSP LOSP-5A S WS -MDP24-PW R S SS-X HE-XE-A LIGN D IV-5A-A C S WS -MDP25 S WS -CKV -CC -SW 25 SWS -CKV -CF-A LL S WS -CKV -CF-S WE SS SWS -MDP-CF-FSA LL SWS -MDP-FR-25 SWS -MDP-FS -25 DIV-23-D C DIV-3A -AC S WS -MD P26 S WS -CKV -CC-SW 26 S WS -CKV -CF-S WE SS SWS -CKV -CF-S WE SS S WS -MDP-CF-FSA LL SWS -MDP-FR -26 SWS -MDP-FS-26 SWS -MDP-TM-26 SWS -XH E-XR-MDP26 DIV-24-DC DIV-6A-AC FAILURE OF SW S MDP-2 6 FAILURE OF SWS MDP-25 FAIL URE OF ESSENTIAL SW S MDPs SW S MDP-24 L OOP F LAGS SW S MDP-24 FAILURES TO START FAILURE OF SW S MDP-24 DURING LOOP FAIL URE OF SW S M DP-2 4 FAILURE OF SW S ESSENTIAL HEADER DIVISION BUS DC-21 DC POWER FAILS DIVI SION BUS DC-24 DC POWER FAIL S DIVISION 5 A AC POWER FAILS DIVISION 6 A AC POWER FAILS DIVISION BUS DC-23 DC POWER FAI LS FAILURE OF POW ER TO SW S MDP 24 DIVISION 3 A AC POWER FAI LS OPERATOR FAILS TO RESTORE SW S MDP 26 AFTER T & M SW S MDP 2 3 UNAVAILABLE DUE TO T & M LOSS OF OFFSITE POWER HOUSE EVENT F AIL URE OF SW S PUMPS 26 DISCHARGE CHECK VAL VE FAILURE OF SWS MDP 26 TO ST ART FAILURE O F SWS MDP 2 6 TO RUN FAILURE OF SW S PUMPS 25 DISCHARGE CHECK VALVE FAILURE OF SW S MDP 2 5 TO START FAILURE OF SWS MDP 2 5 TO RUN FAIL URE OF SW S PUMPS 24 DISCHARGE CHECK VAL VE F AILURE OF SW S MDP 2 4 TO START FAI LURE OF SW S MDP 24 TO RUN CCF OF SWS PUMPS T O START CCF OF SWS PUMPS TO START CCF OF SWS PUMPS TO START CCF OF SW S PUMP STRAI NERS CCF OF SWS PUMPS T O RUN CCF OF SWS PUMPS DISCHARGE CHECK VALVES CCF OF SWS PUMPS DISCHARGE CHECK VAL VES LO SS OF DIV 5 A OFFSITE POWER FL AG SW S HOUSE EVENT FAI LURE TO AL IGN ALT ERNATE SAFE SHUTDOW N POW ER SUPPLIES CCF OF SW S PUMPS 24 /25 /2 6 DISCHARGE CHECK VALVES CCF OF SWS PUMPS 2 4/2 5/26 DISCHARGE CHECK VALVES CCF OF SWS PUMPS 2 4/25 /2 6 DISCHARGE CHECK VALVES CCF OF SW S PUMPS 2 4/25 /2 6 DISCHARGE CHECK VALVES CCF OF SWS PUMPS 24 /2 5/2 6 STRAINERS CCF OF SWS PUMPS 24 /2 5/ 26 FIGURE 1E 1 IR No. 247/02-010 SENSITIVE - NOT FOR PUBLIC DISCLOSURE IR No. 247/02-010

HPR HIGH PRESSURE RECIRCULATION RHR RESIDUAL HEAT REMOVAL COOLDOWN RCS COOLDOWN SGCOOL SECONDARY COOLING RECOVERED HPI HIGH PRESSURE INJECTION BLEED BLEED PORTION OF F & B COOLING PORV-RES PORVs CLOSE PORV NO PORVs OPEN MFW -T MAIN FEEDWATER DURING TRANSIENT AFW AUXILIARY FEEDWATER RT REACTOR TRIP IE-TRANS TRANSIENT

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CD 22 T ATWS PORV-1 FIGURE 2 - TRANS SEQUENCE 19 1 IR No. 247/02-010 SENSITIVE - NOT FOR PUBLIC DISCLOSURE IR No. 247/02-010