ML15239A095
| ML15239A095 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 04/07/1998 |
| From: | Labarge D NRC (Affiliation Not Assigned) |
| To: | NRC (Affiliation Not Assigned) |
| References | |
| TAC-M98454, NUDOCS 9804100352 | |
| Download: ML15239A095 (34) | |
Text
.
April 7, 1998 LICENSEE:
Duke Energy Corporation FACILITY:
Oconee Nuclear Station, Units 1, 2, and 3
SUBJECT:
SUMMARY
OF THE MEETING ON APRIL 1, 1998 - OCONEE HIGH PRESSURE INJECTION SYSTEM RELIABILITY STUDY (TAC NO.
M98454)
On April 1, 1998, personnel from the Office of Nuclear Reactor Regulation and the Office of Analysis and Evaluation of Operational Data met at the NRC headquarters in Rockville, Maryland, with representatives of the Duke Energy Corporation (DEC) staff to discuss a Reliability Study of the Oconee Nuclear Station Units 1, 2, and 3 High Pressure Injection (HPI)
System that was submitted on December 18, 1997. Enclosure 1 is a list of the individuals who attended the meeting and Enclosure 2 is the handout material that was supplied by DEC.
The topics discussed included the HPI problems that prompted DEC to conduct the study; an overview of the HPI system; scope, objectives, methodology, results, and conclusions of the Reliability Study; and the status of actions that have been, and will be taken, as a result of the study recommendations.
The staff has reviewed the Reliability Study and recognize it as a high quality, detailed assessment of the Oconee HPI system that provided qualitative and quantitative insights into the reliability of the HPI system. The study used probabilistic risk analysis to assess the reliability of the HPI system in performing certain mitigation functions. DEC explained during the meeting that the recommendations resulting from the study are being addressed in a continuing program to upgrade the HPI system. The staff plans no formal technical review of the December 18 submittal, but will use it in continuing evaluations associated with the HPI system. In addition, the staff suggests that the submittal be made available to the Babcock and Wilcox"Owners Group. This action completes staff activities related to the Unit 2 HPI injection line welds crack and closes TAC No. M98454.
Original signed by:
David E. LaBarge, Senior Project Manager Project Directorate 11-2 Division of Reactor Projects - I/Il Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, and 50-287
Enclosures:
Distribution:
- 1. Attendance List See next page l
- 2. DEC Handout 001.
00 cc w/encls: See next page a- 0 l: Z9 DOCUMENT NAME: G:\\OCONEE\\MTGO4O1.SUM To receive a copy of this document, indicate in the box:
"C" = Copy without attachment/enclosure "E" = Copy with attachment/enclosure EN E "N" = No copy OFFICE PDII-2 PDII-2/
EMEB PDI L
NAME DLaBQe6n IBery RWessman*
I PedK I
DATE
& /98
/
/98 4 /6 /98 OFFICIAL RECORD COPY
- See previous concurrence
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 April 7, 1998 LICENSEE:
Duke Energy Corporation FACILITY:
Oconee Nuclear Station, Units 1, 2, and 3
SUBJECT:
SUMMARY
OF MEETING ON APRIL 1, 1998 - OCONEE HIGH PRESSURE INJECTION SYSTEM RELIABILITY STUDY (TAC NO.
M98454)
On April 1, 1998, personnel from the Office of Nuclear Reactor Regulation and the Office of Analysis and Evaluation of Operational Data met at the NRC headquarters in Rockville, Maryland, with representatives of the Duke Energy Corporation (DEC) staff to discuss a Reliability Study of the Oconee Nuclear Station Units 1, 2, and 3 High Pressure Injection (HPI)
System that was submitted on December 18, 1997. Enclosure 1 is a list of the individuals who attended the meeting and Enclosure 2 is the handout material that was supplied by DEC.
The topics discussed included the HPI problems that prompted DEC to conduct the study; an overview of the HPI system; scope, objectives, methodology, results, and conclusions of the Reliability Study; and the status of actions that have been, and will be taken, as a result of the study recommendations.
The staff has reviewed the Reliability Study and recognize it as a high quality, detailed assessment of the Oconee HPI system that provided qualitative and quantitative insights into the reliability of the HPI system. The study used probabilistic risk analysis to assess the reliability of the HPI system in performing certain mitigation functions. DEC explained during the meeting that the recommendations resulting from the study are being addressed in a continuing program to upgrade the HPI system. The staff plans no formal technical review of the December 18 submittal, but will use it in continuing evaluations associated with the HPI system. In addition, the staff suggests that the submittal be made available to the Babcock and Wilcox Owners Group. This action completes staff activities related to the Unit 2 HPI injection line weld crack and closes TAC No. M98454.
David E. LaBarge, Senior Project Manager Project Directorate 11-2 Division of Reactor Projects - I/Il Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, and 50-287
Enclosures:
- 1. Attendance List O 2.
DEC Handout cc w/encls: See next page
Oconee Nuclear Station cc:
Mr. Paul R. Newton Mr. J. E. Burchfield Legal Department (PBO5E)
Compliance Manager Duke Energy Corporation Duke Energy Corporation 422 South Church Street Oconee Nuclear Site Charlotte, North Carolina 28242 P. 0. Box 1439 Seneca, South Carolina 29679 J. Michael McGarry, Ill, Esquire Winston and Strawn Ms. Karen E. Long 1400 L Street, NW.
Assistant Attorney General Washington, DC 20005 North Carolina Department of Justice Mr. Robert B. Borsum P. 0. Box 629 Framatome Technologies Raleigh, North Carolina 27602 Suite 525 1700 Rockville Pike L. A. Keller Rockville, Maryland 20852-1631 Manager - Nuclear Regulatory Licensing Manager, LIS Duke Energy Corporation NUS Corporation 526 South Church Street 2650 McCormick Drive, 3rd Floor Charlotte, North Carolina 28242-0001 Clearwater, Florida 34619-1035 Mr. Richard M. Fry, Director Senior Resident Inspector Division of Radiation Protection U. S. Nuclear Regulatory North Carolina Department of Commission Environment, Health, and 7812B Rochester Highway Natural Resources Seneca, South Carolina 29672 3825 Barrett Drive Raleigh, North Carolina 27609-7721 Regional Administrator, Region II U. S. Nuclear Regulatory Commission Mr. William R. McCollum Atlanta Federal Center Vice President, Oconee Site 61 Forsyth Street, S.W., Suite 23T85 Duke Energy Corporation Atlanta, Georgia 30303 P. 0. Box 1439 Seneca, South Carolina 29679 Max Batavia, Chief Bureau of Radiological Health South Carolina Department of Health and Environmental Control 2600 Bull Street Columbia, South Carolina 29201 County Supervisor of Oconee County Walhalla, South Carolina 29621
Meeting Summary Dated April
, 1998 Hard Copy with all encs.
'Docket File PUBLIC PD 11-2 Rdg.
D. LaBarge E-Mail w/Encl. 1 only SCollins/FMiraglia BBoger JZwolinski HBerkow LBerry TMartin (e-mail to SLM3)
DMarksberry CJackson BErliot DO'Neal AEI-Bassioni MHartzman SWeerakkody DRasmuson RWessman MTschiltz, EDO LPlisco, RII COgle, RII
ATTENDANCE RECORD
Purpose:
Meeting To Discuss Oconee HPI Reliability Study Date:
4/1/98 NAME (PLEASE PRINT)
AFFILIATION Ed Burchfield Duke Energy/Oconee Nuclear Site William McIntyre Duke Energy/Oconee Nuclear Site Bill Foster Duke Energy/Oconee Nuclear Site Steve Nader Duke Energy/Oconee Nuclear Site P. M. Abraham Duke Energy/General Office - PRA Robert Boyer Duke Energy/General Office - PRA Don Marksberry NRC/AEOD/RRAB Dave LaBarge NRC/NRR/PD 11-2 Christopher Jackson NRC/NRR/SRXB Barry Elliot NRC/NRR/EMCB Dan O'Neal NRC/NRR/SPSB Adel El-Bassioni NRC/NRR/SPSB Mark Hartzman NRC/NRR/EMEB Sunil Weerakkody NRC/AEOD/RRAB Dale Rasmuson NRC/AEOD/RRAB Richard Wessman NRC/NRRIEMEB
Oconee Nuclear Station High Pressure Injection (HPI) Reliability Study Duke - NRC Meeting April 1, 1998
Agenda i
Introduction and Background M. K. Nazar for the HPI Reliability Study 2
Overview of the HPI system S. L. Nader 3
Overview of the HPI Reliability Study P. M. Abraham
- Scope
- Objectives
- Methodology
- Results and Conclusions 4
Oconee Actions on Recommendations M. K. Nazar from the Study 5
Summary P. M. Abraham 2
Introduction and Background for the HPI Reliability Study
+ On May 3, 1997, Unit 3 was in cooldown when the 3A and 3B HPI pumps were rendered inoperable due to operation without an adequate suction source from the LDST. The LDST level instruments had erroneously indicated an adequate level when the tank was actually nearly empty.
- The event raised a larger question about the reliability of HPI system functions.
- As a result of this event, Duke committed to various corrective actions, one of which was to perform a detailed reliability study of the HPI system.
3
Schedule
+ Decision on study May 1997
+ Duke letter to the NRC on the June 4, 1997 scope, objectives and schedule
+ Performed HPI study June - Dec. 1997
+ Draft report issued Nov. 1997
+ Oconee site management briefing Nov. 12, 1997
+ Final report issued Dec. 1997
+ NRC submittal Dec. 18, 1997
+ NRC briefing April 1, 1998 4
HPI Reliability Study Overview of the HPI system 5
HPI System Diagram Normal Injection Flow To Aux. Pzr.
From LPI Cooler 3A Spray
-3HPIMLOO4 13HP-120 3HP-90 3HP-259 3H 3HP2 1
ESB I
RB ORIFICE 3LP-4 3 P-5 3HP1 1 3H -487 3 P 27 Cold Leg 3A2 ES-2 3HP-1186 00I-126 3HP-102 3HP-111i AB 3LP-568 Borated Water Storage Fo P
olr3 Tank 3LP-286 T Au From LPI Colr1ASpa LOST 3
P-107Min3HP-120n 3 LP-15 P-1 3HP-99 E -1,3H-1 19 T
3LP-Sea ReunRP E][Hp0 3HP-25 Coolers3HP-1 18 Seal 3HP-3H72 ES3A ES-1IC 3 H P -100 ~~Min.
Fl t
ne C
l e
B Ton Sealn Re u 3HP-1158 3
P 5
P_
P 8
~
3H
-21 8ORFC 33 ~ ~ ~ ~ ~ A P-RB33P 43P 4 H -8 ORIFICE P-8 7 3 27 5 3C P
I Cold Leg 3A2 L-5 3HP4863H512 33HP-41 StorageM F
o w L I Ce r3 3L3HP-117 Mi
.FLw unO
Overview of the IPI system
+ The system performs both normal operating functions (including unit start-up and shutdown) and accident mitigation functions.
+ The HPI System consists of:
- a common suction header
- three motor-driven, high pressure centrifugal pumps
- one discharge path for normal operation
- two discharge paths for accident mitigation
+ The LDST is the primary suction source for normal operation.
The BWST is the suction source for accident mitigation.
+ During normal operation, one HPI pump (either the A or B pump) takes suction on the LDST and provides:
- RCS make-up
- RCS purification and chemical control, and
- RCP seal injection
Overview of the HPI system
+
The A and B HPI pumps are equipped with an auto start feature which will start the pumps on low RCP seal injection flow.
- During accident mitigation, the HPI system:
- automatically initiates on an ES signal
- takes suction from the BWST
- is not isolated from the LDST
- injects into the RCS cold legs through four injection nozzles.
+ The HPI system may be cross-connected. If a there is inadequate flow in an HPI injection header, discharge cross-connect valve HP-409 or HP-410 is opened to assure two flow paths and two pumps.
+ The HPI system may be supplied from the LPI system. In this "piggy-back" alignment, MOVs LP 15 and/or LP-16 are opened to supply the HPI suction header from the LPI coolers.
8
HPI Reliability Study Overview of the HPI Reliability Study 9
Methodology
+
This study uses PRA methods (fault trees, reliability data, success criteria, and modeling of appropriate human actions) to assess the reliability of the HPI System.
+
Analysis consists of:
-building a new HPI fault tree model
- integrating the HPI model into the plant PRA model
- solving the HPI system and plant PRA models
- interpreting the significance of the failure modes
- performing uncertainty analysis and sensitivity studies on the reliability results
+
The scope of the HPI model includes all system functions required to mitigate UFSAR Chapter 15 design basis events and probabilistically significant events of interest (i.e., it includes HPI functions modeled in the Oconee Rev. 2 PRA).
An evaluation of the HPI system capability for external events (seismic, fire, tornado, and flooding events) and shutdown PRA is performed for completeness.
10
Project Team Members
+ PRA Group
+ Site Review R. P. Boyer S. L. Nader G. L. Cruzan R. S. Leatherwood L. M. Kanipe D. D. Smith R. W. McAuley W. R. McIntyre M. J. Barrett D. W. Phelps H. D. Brewer
+ GO Manager
+ Site Manager P. M. Abraham J. E. Burchfield
- HPI Study Scope and Obj ectives
+ to obtain quantitative information on the reliability of the system for the accident mitigating functions,
+ to provide information on the risk significance of the various failure modes of concern,
+ to facilitate identification of viable enhancements to the system, and
+ to provide information on the reliability of the system for the normal operating functions.
12
- HPI Reliability Study Process
+ Plant and System Familiarization Information Gathering System Walkdown
+ Failure Modes and Effects Analysis
+ Operating Experience Review
+ Analysis of HPI System Success Criteria Review of Design Basis Accidents Best-Estimate Core T/H Analysis
+ Fault tree analysis
+ Data analysis
+ Integrated plant-level solution
+ Review of results and formulation of conclusions and recommendations
+ Site meeting
+ Draft summary report
+ Peer review
+ Final analysis and summary report
+ Work window: 6/97 - 12/97
+ Distribute final report: 12/97 13
HPI System Model Details Letdown Storage Tank Borated Water Storage Suction Pumping Discharge Tank Segment Segment Segment RCS Cold Legs RB Emergency Sump via Low Pressure Injection system ac powerAJ ac power l ESFAS ac power A-i dc power dc power hu ESFAS ESFAS hmnerr human errors human errors LDST moel A~1thuman errorsAt LPI system model pump cooling Typical for 'A' or 'B' loop
- 2 injection nozzles 2 pumps 1 - 2 discharge paths 14
Examples of Failure Modes Considered Component Failures Component/Train is in Valve fails to open Maintenance 4
Pump fails to run BWST suction train A(B) 4 Pipe failure
=
HPI train A(B)
=o LDST Level String 1(2)
Common Cause Failures LDST Pressure String 1(2)
=
of letdown flow transmitters 4
of LDST level transmitters Failure due to Human Errors of LDST pressure Equipmen-not properly transmitters restored following of BWST suction valves to open
=
Equipment not properly 4
of HPI pumps to run operated
=
of HPI pumps to start 4
of HPI pumps to restart Pre-event Failures following a LOOP Inadequate level in the LDST
=> Inadequate pressure in the Support System Failures LDST 4
ac power 4
dc power Post-event Failures CES signals o Failure of LDST discharge check valve to close z )
Failure of operators to swap HPI suction to RB sump t15
0 Normal Letdown Flowpath 3HP-196 Component 3HP-19M7 3H 3HPISV009 34P 03HP-7 3HP-41 3 HP-13 3H-P 7
Letdown ES-1 3P1 3HP-1 Cooler 3A FHPm F
F 0Letdown Filter 3A RSP 31 1 3 A ES1 3HP-3HP-195 3HP-8 3HP-47 3HP-14 3HP-2 como ndn 3HP.4 FCT Purifction L e t ow n
in e ra i 3 H P -1 1 I
Scon 3HP 3
3HP9 33i f3P1 Coo Belo 3HP-50 Letdown Coolr 3BFrom Seal
-Filter 3B Return Coolers 3HP-189 3HP-78 L~etdown E
Storage TO HPI Tank Pump' Suction 3HP-23 3HP-97 To RC Bleed Hold Up Tank 3HP-79 I16
LD ST Instrumentation HP11VO095 HP11V0370 HP11V0371 HP11VO097 HP11V0371 HP11VVO362 HPIIV0362 HPIPT028THPPT3OI SinTo HPPUOBP1RO2 (A11 HPIP00214 huC HP11VO085 3 P1 V36 L(4-20madc)
I S-E To HPI Pump HP107 HP2zScinHae 170313
Three HPI System Functions
" Mitigate Deterministic, Design Basis Events
" Mitigate PRA sequences
" Provide Normal RC Make-up, RCP Seal Injection, and Aux.
Spray 18
HPI System Success Criteria (Injection mode)
Design Basis Events Success Criteria Non-LOCA events 1 pump, 1 injection path Random-location small 1 pump, 1 injection path break LOCA events HPI Line Break and RCP 2 pump, 2 injection paths Discharge Break LOCA events PRA Scenarios Success Criteria Non-LOCA events 1 pump, I injection path Random-location small 1 pump, 1 injection path and medium break LOCA events HPI Line Break and RCP 2 pump, 2 injection paths Discharge Break LOCA events Feed and Bleed Cooling 2 pumps, 1 injection path RCP Seal Cooling 1 pump, 4 seal injection paths 19
HPI System Success Criteria (Recirculation mode)
Design Basis and Success Criteria PRA Events All events 1 pump, 1 injection path 20
HPI System Success Criteria (Normal Operation)
Function Success riteria Normal Injection 1 pump, 1 injection path (Make-up)
RCP Seal Injection 1 pump, 4 RCP injection paths Aux. Spray 1 pump, Aux. Spray
_injection path 21
HPI Reliability Study Results Accident Mitigation Failure Description Probability Reliability Chapter 15 non-LOCA accidents 2.8E-4
> 99.9%
Chapter 15 HPI Line Break LOCA -
3.6E-3 99.6%
Injection mode PRA random-location LOCA-9.4E-4 99.9%
Injection mode PRA HPI Line Break LOCA-Injection 2.5E-3 99.7%
mode Feed and Bleed Cooling-Injection 1.2E-3 99.9%
mode Recirculation for Chapter 15 and PRA 1.1E-2 98.9%
accidents RCP Seal Injection for Non-LOCA 4.3E-4 99.9%
accidents 22
HPI Reliability Study Results Normal Operation Over One Year Period
{Aux. Spray on a per demand basis}
Failure Description Probability Reliability W
Normal Injection (Make-up) 5.2E-2 95%
RCP Seal Injection 7.5E-2 93%
Aux. Spray 1.6E-2 98%
23
Top Cut Set Results
+
Chapter 15 HPI Line Break LOCA - Injection mode
+
PRA random-location LOCA-Injection mode
- 1) LDST Press. Root Valve Failure Cause LDST to be at 2.5E-4 High Pressure, Operators Fail to Recognize Pressure Instrument Failure
- 2) Common Cause Failure of LDST Level Transmitters,
- 2. 1E-4 Operators Fail to Recognize Level Instrument Failure
+
PRA HPI Line Break LOCA-Injection mode
- 1) HPI Break Occurs on 'B' Side, 'Al' Path Valve HP-486 4.5E-4 Closes
- 2) HPI Break Occurs on 'B' Side, 'A2' Path Valve HP-487 4.5E-4 Closes
+
Recirculation for Chapter 15 and PRA accidents
- 1) LDST Discharge Check Valve HP-97 Fails To Close, 8.8E-3 Operators Fail to Isolate Diversion Flow From RB Sump to LDST
- 2) Operators Fail to Initiate High Pressure Recirculation 2.2E-3 24
Core Damage Impact Failures attributed to the HPI system sum to 1.6E-5, or 21%
of the CDF of 7.77E-5:
Total CDF = 7.77E-5 (Internal and External Events) 21%
- Failures involving the HPI system
- Failures involving other systems 7 9%
HPI system failures are partioned as shown below:
5%
6%
- Failure ofLDST discharge valve HP-97 7*
Failure ofthe operators to initiate HPR 0 CCF of the LDST instrumentation g other HPI failures 75%
25
Sensitivity Studies Purposes
" Assess the significance of alternate system configurations
" Assess the value of any recommendations
" Assess the impact of key assumptions
" Estimate the possible range on the results, considering the variability of the data 26
Sensitivity Studies Topic I sights HPI pump auto-start
- Relieves operators of the burden of feature starting pump on low RCP seal injection flow
- Does not have an adverse impact on system reliability or risk results Isolation of LDST
- Eliminates failures associated with during RB emergency LDST check valve HP-97, reducing sump recirculation CDF by about 28%
- Isolation on ES signal is less optimal since LDST flow allows time to recover potential failure of BWST suction valves Addition of local LDST
- A weekly comparison of local pressure gauges or utilization of and level gauge reading to control room increased calibration indication results in scme improvement frequency in system reliability and reduces CDF by about 2%
HPI pump failure rates
- With trains isolated cannot satisfy single failure criterion to provide two tPI pumps
- Operation with trains isolated would lead to a reduction in system reliability
- Operation with HP-116 open and HP-27 closed has no measurable impact on CDF Auto-swap to BWST on
- Reduces operator burden low LDST level
- Does not have an significant impact on system reliability or risk results Uncertainty Analysis
- 90% confidence interval for design basis LOCA, injection mode:
.2E-3 to 8.3E 3
- 90% confidence interval for design basis LOCA, recirculation mode: 2.OE-3 to 3.3E-2
- 27
Recommendations o
In light of the importance of the HPI system in mitigating design basis events, the system must be systematically monitored and maintained.
When equipment failures occur, the root cause should be fully analyzed, and the implications of the failure fully understood and resolved. This is currently achieved as part of the Maintenance Rule program.
Provide the capability to isolate potential flow diversion through LDST discharge valve HP-97. This could be achieved by improvements in the plant procedures and operator training or by hardware modifications if found viable.
To reduce the common cause failure probability of the LDST level and pressure instrument strings, implement a more focused verification of the instrument strings, instead of the current refueling frequency.
28
Impact of Proposed Recommendations
+ Implementation of the recommendations results in an estimated 17% drop in total CDF:
Total CDF = 6.47E-5 (Internal and External Events) 5%
M Failures involving the HPI system a Failures involving other SystenE 95%
29
HPI Reliability Study Oconee Actions on Recommendations from the Study 30
Oconee Response
+
Participated in the review of the models, data, results and conclusions of the study
+
Increased site management awareness of and sensitivity to the importance of the HPI system in mitigating design basis events and PRA significant scenarios
+
Accepted the recommendations from the study
+
Specific responses Recommendation 1: Appropriately monitor and maintain HPI system.
This recommendation is being addressed by the Maintenance Rule program.
Recommendation 2: Isolate the LDST during RB sump recirculation.
Oconee EOPs have been revised to instruct operators to close HP-23 prior to sump recirculation.
Recommendation 3: Further reduce the LDST CCF potential.
Local LDST level and pressure gauges will be installed. Local indication will be compared with control room indication on a routine basis.
31
HPI Reliability Study Summary 32
Summary
+ A comprehensive study of the Oconee HPI system was performed to provide perspectives on:
4 the reliability of the system in performing its design basis accident mitigation functions 4 the reliability of the system in performing its accident mitigation functions as modeled in the PRA 4 the reliability of the system in performing selected normal functions 4 the risk significance of potential system failure modes.
+ The study verified the capability of the HPI system to accomplish its ECCS functions reliably.
The study identified areas for potential enhancements.
+
The recommended enhancements are being implemented.
33