ML031690302
| ML031690302 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 06/16/2003 |
| From: | Nuclear Management Co |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| Download: ML031690302 (36) | |
Text
1 Point Beach Nuclear Plant June 6, 2003 Regulatory Conference Concerning Auxiliary Feedwater Orifice Issue
2 Agenda Mano Nazar Closing Remarks Mark Reddemann Significance Determination Fred Cayia Root Cause Analyses Fred Cayia Overview Mano Nazar Purpose/Objective
3 Purpose
Provide Overview of Auxiliary Feedwater System Orifice Issue
Discuss Root Cause Evaluation of the AFW Orifice Issue
Present Methodology and Conclusion of the NMC/Point Beach Significance Determination Process for AFW Orifice Issue
4 Objective
Present New Information and Considerations Concerning Issue Significance
Provide NMCs Position on the Characterization of the Apparent Violation of 10 CFR 50, Appendix B, Criterion III Design Control
5 Overview
Overview Auxiliary Feedwater System L
O 1 -1 9 L
O 2 -5 7 L
O 2 -5 6 L
O L
O E L E C T R IC A U X IL IA R Y F E E D P U M P S T E A M D R IV E N A U X IL IA R Y F E E D P U M P E L E C T R IC A U X IL IA R Y F E E D P U M P S T E A M D R IV E N A U X IL IA R Y F E E D P U M P M O V 4 0 1 6 M O V 4 0 0 9 2 M O V 4 0 0 6 2
M O V 4 0 0 0 2 M O V 4 0 0 1 M O V 4 0 2 3 M O V 4 0 2 2 1 M O V 4 0 0 6 2 M O V 2 0 1 9 2 M O V 2 0 2 0 1 M O V 2 0 1 9 1 M O V 2 0 2 0 2 M S 2 0 8 2 1 M S 2 0 8 2 C V 4 0 1 9 C V 4 0 1 2 M O V 4 0 2 1 U N IT 2 C O N T A IN M E N T U N IT 1 C O N T A IN M E N T 1 M O V 4 0 0 1 S e is m ic C la s s 1
4 5,0 0 0 G A L LO N C S T A N K 4 5,0 0 0 G A L LO N C S T A N K M
S E R V IC E W A T E R M
M M
M M
M M
M M
M S E R V IC E W A T E R M
M M
M M
1 M O V 4 0 0 0 M
M O V 4 0 2 0 1 P 2 9 P 3 8 B 2 P 29 P 3 8 A M A IN S T E A M M A IN S T E A M S E R V IC E W A T E R M A IN S T E A M M A IN S T E A M M A IN F E E D W A T E R M A IN F E E D W A T E R M A IN F E E D W A T E R M A IN F E E D W A T E R S T E A M G E N E R A T O R 1
B S T E A M G E N E R A T O R 1
A S T E A M G E N E R A T O R 2
A S T E A M G E N E R A T O R 2
B S E R V IC E W A T E R L
O F O F O D C -
A D C -
B D C -
A D C -
B 1 -1 0 7 1 -4 4 1 -1 0 4 1 -1 0 8 F C C S T 1 R O -4 0 0 3 F C C S T R O -40 1 5 F C C S T R O -4 0 08 F C C S T 2 R O -4 0 0 3 2 A O V -4 0 0 2 1 A O V -4 0 0 2 1 -1 1 1 1 -1 0 1 1 1 3 A O V -4 0 1 4 1 -1 8 1 -3 1 1 -1 0 6 1 -1 0 2 1 -1 0 0 1 0 9 A O V -4 0 0 7 1 1 2 2 -1 1 1 2 -1 0 8 2 -1 0 6 2 -1 0 3 L
O 2 -3 2 N O T E : A ll la b e le d va lve s a re A F -S yste m va lve s, e xce p t as n o te d R e fe re nce M -2 1 7 S h. 1 & 2 2 -1 0 1 2 -1 0 7 2 -1 0 5 L
O 2 -4 5 2 -1 0 0 1 1 0 D C -B T H R O T T LE D D C -A T H R O T T LE D D C -A T H R O T T LE D D C -B T H R O T T LE D D C -
B D C -
A 2 -6 4 L O 3 9 L O 5 2 L O 1 -2 6 L O M
S e is m ic C la s s 1
F O R IN F O R M A T IO N O N L Y F ire W a te r C o n n (4 to ta l)
7 Overview Timeline of AFW System Improvements March 1979 March 1979 TMI TMI Accident Accident Feb. 1981 Feb. 1981 GL 81-14 issued GL 81-14 issued (AFW seismic (AFW seismic qualifications) qualifications)
May 1982 May 1982 NRC SER, NRC SER, NUREG-0737 NUREG-0737 Item II.E.1.2, Item II.E.1.2, NRC accepts NRC accepts safety grade safety grade status of AFW status of AFW auto initiation auto initiation 1985 1985 Added low suction Added low suction pressure trip pressure trip (TMI response-(TMI response-seismic/ tornado) seismic/ tornado)
June 1988 June 1988 Point Beach response Point Beach response to IEB 88-04 to IEB 88-04 (review of AFW (review of AFW minimum flow) minimum flow) identifies need for identifies need for greater recirculation greater recirculation flow capability flow capability 1980 1980 1985 1985 1990 1990 1995 1995 1991 1991 Added recirc flow Added recirc flow instruments and instruments and larger recirc lines and larger recirc lines and orifices to increase orifices to increase recirc flow to 70 &
recirc flow to 70 &
100 GPM 100 GPM 1970 1970 Oct 1970 Oct 1970 U1 Licensed U1 Licensed March 1973 March 1973 U2 Licensed U2 Licensed Note: At time of licensing, Note: At time of licensing, AFW was not safety related AFW was not safety related July 1981 July 1981 Added AFW supply Added AFW supply line flow indication line flow indication (TMI response)
(TMI response)
Sept 1986 Sept 1986 Added SR EQ level Added SR EQ level transmitters for CST transmitters for CST (TMI response)
(TMI response)
Nov 1983 Nov 1983 Added AFW Added AFW inoperable alarm inoperable alarm (TMI response)
(TMI response)
Aug 1984 Aug 1984 Added AFW Added AFW discharge discharge MOV controls MOV controls (TMI (TMI response) response)
April 1993 April 1993 Installed air line Installed air line to allow IST to allow IST testing of AFW testing of AFW recirculation recirculation valves valves 2000 2000 Nov 1995 Nov 1995 Added SW flush Added SW flush connection at AFW connection at AFW pump suctions pump suctions July 1997 July 1997 Missile Missile protected protected portions of portions of AFW suction AFW suction piping piping July 1997 July 1997 Added AFW Added AFW discharge valve discharge valve backup nitrogen backup nitrogen supply; installed supply; installed cable separation cable separation modifications modifications Feb 1998 Feb 1998 Upgraded Upgraded AFW low AFW low suction suction pressure trip pressure trip March 1999 March 1999 Modification to Modification to assure control assure control wire separation wire separation for AFW system for AFW system Feb. 2002 Feb. 2002 Added Added backup backup N2/air to N2/air to all AFW all AFW recirc recirc valves valves Sept 2002 Sept 2002 AFW AFW recirculation recirculation designated designated safety safety function function March 2003 March 2003 Proper Proper (larger)
(larger) orifices orifices installed on installed on all AFW all AFW recirc lines recirc lines Jan 2002 Jan 2002 NRC NRC inspection of inspection of Modifications Modifications
/50.59
/50.59
8 Overview Recirculation Line Orifice Discussion:
Orifice Modification Developed in 2000 to Reduce Recirculation Line Cavitation
Recirculation Line Orifices-Modification History May 2002 October 2002 TDAFP Modification Installed December 2001 March 2002 Turbine Driven Auxiliary Feedwater Pump (TDAFP) Modification Issued Unit 2 Unit 1 November 2000 March 2001 MDAFP Modification Installed June 2000 June 2000 Motor Driven AFW Pumps (MDAFP)
Modification issued Pump B Pump A
9 Overview Recirculation Line Orifice
Identified by NMC Following System Testing of the Motor Driven AFW Pump
Orifice Plugging Could Occur When AFW Pumps Were Aligned to Service Water Resulting in Potential Common Mode Failure
Prompt Corrective Actions All Four AFW Pumps Declared Out-of-Service Due to Potential Recirculation Orifice Common Mode Failure Compensatory Actions Established to Direct Operators to Secure AFW Pumps in the Event Minimum Recirculation Flow Cannot be Maintained
==
Description:==
Potential for Fouling of Recirculation Line Coincident with Procedurally-Directed Operator Action to Secure AFW Forward Flow.
10 Root Cause Analyses
11 Root Cause Analyses AFW Recirculation Orifice
Root Cause-Orifice Issue (RCE000191)
- Failure to Properly Evaluate the Potential for Orifice Plugging Within the Design Process
Contributing Causes
- Use of Unverified Information and the Omission of Key Design Information in the Safety Evaluation for the Orifice Modification
12 Root Cause Analyses AFW Recirculation Orifice
Corrective Actions-Complete
- Increased Engineering Management Involvement in Approval and Oversight of Modifications
- Implemented Periodic Review of Engineering Products by a Quality Review Team
- Presented Lessons Learned to Engineering Personnel Stressing the Use of the Design Process
- Revised Training Materials to Accurately Reflect AFW Recirculation Line Design Functions
- Orifice Redesigned, Tested and Installed on all Four Pumps in March 2003
13 Missed Opportunity (RCE 01-069)
The Root Cause Problem Statement Focused on Emergency Operating Procedure (EOP) Limitations Related to a Loss of Instrument air event.
The Root Cause Problem Statement should have Focused on the Potential Loss of Recirculation Flow.
The Extent of Condition Evaluation would then have Investigated Conditions in Addition to a Failed Closed AFW AOV recirculation valve.
Examples of Possible Loss of Recirculation Failures would have Included:
Orifice Plugging
Electrical/ Control System Failures
Indication Failures Root Cause Analyses AFW Air Operated Valve Finding
14 Root Cause Analyses Comprehensive AFW Evaluation
Root Cause-Comprehensive AFW Evaluation (RCE000202)
Failure to Consider the Integration of AFW System Design and Accident Progression (RC-1)
Less than Adequate Knowledge of the Safety Significance of the AFW Recirculation Line in Protecting the Pumps (RC-2)
Contributing Causes Lack of Problem and Issue Ownership (CC-1)
- Corrective Action Program Weaknesses Less than Adequate Engineering / Operations Interface (CC-2)
Less than Adequate Management of the Inter-Relationship of Documents (CC-3)
15 Root Cause Analyses Comprehensive AFW Evaluation
Prompt Corrective Actions-Complete Placed Modifications Developed using Old Process on Installation Hold Pending Accident Progression Review Implemented Multi-Discipline Review of Proposed Modifications by Management Team
Interim Corrective Actions-Complete Implemented New Fleet Modification Process Implemented Design Review Board Assigned Issue Managers for Significant Station Issues Conducted Detailed Review of AFW Design and Licensing Bases (RC-2)
Implemented the Corrective Action Program Improvements
16 Root Cause Analyses Comprehensive AFW Evaluation Additional Corrective Actions:
Enhance Understanding of System Design and Accident Progression (RC-1)
- Upgrade Modification Process and EOP/AOP change process
- Develop and conduct training for Engineering and Operations
Resolve Remaining Issues from AFW Design and Licensing Bases (RC-2)
Develop and Conduct Training on AFW Design Bases (RC-2)
Strengthen the Role of Engineering in the Development/Revision of Operations Procedures (CC-2)
Upgrade Electronic Document Management System (CC-3)
Continue Implementation of Corrective Action Program Improvements
17 Significance Determination
18 Significance Determination Historical Timeline 2000 2000 2001 2001 2003 2003 Nov 2001 Nov 2001
issue.
- Procedures Procedures modified to modified to monitor recirc monitor recirc AOV position and AOV position and low instrument air low instrument air header pressure header pressure alarm to ensure alarm to ensure minimum AFW minimum AFW flow flow Sept 2002 Sept 2002 AFW recirc AFW recirc AOV open-AOV open-function function designated designated safety related safety related Nov 2000 Nov 2000 A & B MD AFW A & B MD AFW pump anti-pump anti-cavitation orifice cavitation orifice installed installed Oct 2002 Oct 2002
- Procedures modified Procedures modified to rely on forward to rely on forward flow to ensure min flow to ensure min flow flow Dec 2001 Dec 2001 U2 TD AFW pump U2 TD AFW pump anti-cavitation orifice anti-cavitation orifice modification issued modification issued June 2000 June 2000 A & B MD AFW pumps A & B MD AFW pumps anti-cavitation orifice anti-cavitation orifice modifications issued modifications issued May 2002 May 2002 U2 TD AFW pump U2 TD AFW pump anti-cavitation anti-cavitation orifice installed orifice installed March 2003 March 2003 Replacement Replacement (larger)
(larger) orifices orifices installed on all installed on all AFW recirc AFW recirc lines lines May/June 2002 May/June 2002 Installed safety Installed safety related backup related backup N2/air to all N2/air to all AFW recirc AFW recirc AOVs AOVs 2002 2002 March 2002 March 2002 U1 TD AFW pump U1 TD AFW pump anti-cavitation orifice anti-cavitation orifice modification issued modification issued Key:
Key:
Recirculation Line Orifice Recirculation Line Orifice Recirculation Line AOV Recirculation Line AOV
19 Significance Determination Events Affected by Orifices Dual Unit Events
Loss of Service Water
Loss of Instrument Air (Minor)
Loss of DC Bus D02 Single Unit
Transient (Minor)
Transient without Heat Sink
Steam / Feed Line Break (Minor)
Loss of Component Cooling Water (Minor)
20 Significance Determination NMC Orifice Risk Increase-Unit 1*
2001 2001 2003 2003 Nov 2001 Nov 2001
- Plugging identified Plugging identified
- Procedures Procedures changed changed Dec 2001 Dec 2001 U2 TD AFW pump U2 TD AFW pump orifice mod issued orifice mod issued June 2000 June 2000 A & B MD AFW pumps A & B MD AFW pumps orifice mods issued orifice mods issued May 2002 May 2002 U2 TD AFW pump U2 TD AFW pump orifice installed orifice installed March 2003 March 2003 New orifices New orifices installed on all installed on all AFW recirc AFW recirc lines lines May/June 2002 May/June 2002 Installed AOV Installed AOV backup N2/air backup N2/air 2002 2002 March 2002 March 2002 U1 TD AFW pump U1 TD AFW pump anti-cavitation orifice anti-cavitation orifice modification issued modification issued 2000 2000 Calculated Calculated Base Base Risk Risk Risk due to Risk due to orifice orifice plugging plugging
< 1 year from
< 1 year from identification identification Risk due to orifice Risk due to orifice plugging > 1 year plugging > 1 year from identification from identification Risk due to Risk due to orifice plugging orifice plugging mitigated by mitigated by procedure procedure changes changes
21 Significance Determination NMC Orifice Risk Increase-Unit 2**
2001 2001 2003 2003 Nov 2001 Nov 2001
- Plugging identified Plugging identified
- Procedures Procedures changed changed Dec 2001 Dec 2001 U2 TD AFW pump U2 TD AFW pump orifice mod issued orifice mod issued June 2000 June 2000 A & B MD AFW pumps A & B MD AFW pumps orifice mods issued orifice mods issued May 2002 May 2002 U2 TD AFW pump U2 TD AFW pump orifice installed orifice installed March 2003 March 2003 New orifices New orifices installed on all installed on all AFW recirc AFW recirc lines lines May/June 2002 May/June 2002 Installed AOV Installed AOV backup N2/air backup N2/air 2002 2002 March 2002 March 2002 U1 TD AFW pump U1 TD AFW pump anti-cavitation orifice anti-cavitation orifice modification issued modification issued 2000 2000 Calculated Calculated Base Base Risk Risk Risk due to Risk due to orifice orifice plugging plugging
< 1 year from
< 1 year from identification identification Risk due to orifice Risk due to orifice plugging > 1 year plugging > 1 year from identification from identification Risk due to Risk due to orifice plugging orifice plugging mitigated by mitigated by procedure procedure changes changes
Significance Determination-Event Timelines 5.5 Hrs System Not Available 2.1 Hrs
- Transient without Heat Sink and No Water Treatment Normal CST Makeup Available Not Required Not Required Not Required
- Transients without Heat Sink Not Required 15 Hrs Not Applicable Not Applicable 4.8 Hrs Time to Initiate Feed & Bleed (If Required)
RHR conditions reached on CST inventory at ~2.2 hrs-prior to reaching SG level requiring feed & bleed.
Not Required 1.6 Hrs
- Main Steam Line Break (Outside Containment) 12 Hrs 3.3 Hrs
- Main Steam Line Break (Inside Containment) 9.7 Hrs 3 Hrs
- Steam Generator Tube Rupture Three break sizes, with and without safety injection. Only smallest break reaches CST Low-Low Level Not Required 5.1 Hrs (0.5 Break Only)
- Small LOCA Single Unit Events System Not Available 1.6 Hrs
- Loss of Offsite Power, Loss of Instrument Air, Loss of DC Bus D02, Loss of Service Water Dual Unit Events Notes With Water Treatment System Clearwell Time to CST Low-Low Level Events 22
23 Significance Determination Differences for Plugged Orifice
AFW Swap-Over Occurs Hours After Reactor Trip
- Decay Heat Lower
- Charging Successful for Feed and Bleed
- Shutdown Cooling Credited
- Steam Generator Depressurization and Service Water /Fire Water Addition Possible
- Emergency Response Facilities Staffed
- More Time for Troubleshooting and Recovery
24 Significance Determination NRC
Preliminary Evaluation of Risk Increase Based on Phase 2 Analysis
Assumed AFW Failure Probability of 1.0
No Credit for:
Initial Cooling by AFW Charging Feed and Bleed Transition to Shutdown Cooling Service / Fire Water Addition
25
Internal Events Evaluated Probabilistic Risk Assessment MAAP (Modular Accident Analysis Program) used to Demonstrate Success and Determine Timeline of Recovery Actions Human Reliability Analysis for Credited Recovery Actions
Seismic Events Evaluated using Seismic PRA
Fire Event Analysis in Progress Significance Determination NMC
26 Significance Determination NMC Risk Mitigating Factors Incorporated
Water Treatment System
- Makeup to Condensate Storage Tank
- Clearwell Tank Makeup to CST
- Recovery Following Restoration of Off-Site Power
Service/Fire Water through Disabled AFW Pump
Charging for Feed and Bleed
27 Significance Determination NMC Risk Mitigating Factors Incorporated (contd)
Changes to HEPs for Feed and Bleed
Recovery of SI/ RHR Valves Left in Incorrect Position
Operators Starting/Stopping AFW Pumps to Avoid Failure of 2nd and/or 3rd Pump
28 Significance Determination NMC Risk Mitigating Factors Not Incorporated
Available 14,000 Gallons of Water Left in Each CST at Low Low Level
Increase Charging to Maximum While in Loss of Heat Sink Procedure
Likely AFW Pump Survival Time Following Swap-Over to Service Water
- Valve Leakage
- Packing Leakage
Alignment of N2 to Pressurizer PORVs Following Loss of IA
29 Significance Determination Largest Contributors to Risk x
x x
Transient w/o Heat Sink x
x x
x Loss of Offsite Power-Dual and Single Unit x
Loss of SW x
x x
Loss of DC Bus 2 Shutdown Cooling Charging Feed &
Bleed Service /
Fire Water Water Treatment Initiator Largest Contributors Recovery Credited
30 Significance Determination Sensitivity Analysis 5
Start / Stop AFWPs 10 SI / RHR Valve Recovery HEP 19 Charging for Feed and Bleed 48 Feed and Bleed HEP Change 48 Service Water/Fire Water through AFW Pump 91 Water Treatment System Impacts Contribution to CDP Reduction (%)
Factor
31 Significance Determination Results Internal Events
Increase in Internal Events Core Damage Probability
- Unit 1: High White
- Unit 2: Mid Yellow
32 Significance Determination Results External Events-Seismic
Fragility Analysis Performed
Charging, CST, and Service Water Addition Credited Following Safe Shutdown Earthquake
Increase in Seismic Initiated Core Damage Probability
Unit 1: Green
Unit 2: Green
33 Significance Determination Results Increase in Internal Event and Seismic Initiated Core Damage Probability
Unit 1: High White
Unit 2: Mid Yellow
34 Significance Determination Results External Events-Fire
Fire PRA Model Not Developed
Development is in Progress
Method Includes:
- Fire Initiation Frequency
- Detection Probability
- Automatic and Manual Suppression Probability
- Identification of Cables and Determination of Equipment Affected
- Credit for Mitigating Factors
- Consequences of Unsuppressed Fires
Completion Targeted in August
35 Summary
Installation of Inappropriate Orifice Design was Risk Significant
NMC Significance Determination Preliminary Results (Internal and Seismic)
- Unit 1: High White
- Unit 2: Mid Yellow
Final Results, Including Fire, Targeted in August 2003
Further AFW System Modifications
- Electrical Modifications in Progress
- Margin Recover Study
Engineering Excellence Plan
36 Closing Remarks
AFW Orifice Issue Self-Identified and Resolved in Timely Manner.
AFW System Today is more Reliable.
NMC Understands the Importance of the AFW Orifice Issue.
NMC Significance Determination Preliminary Results (Internal and Seismic)
- Unit 1: High White
- Unit 2: Mid Yellow
SDP for Fire Events Remains a Work in Progress.
NMC Concurs with the Characterization of the Apparent Violation of 10 CFR 50 Appendix B.