ML20059H666
| ML20059H666 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 11/01/1993 |
| From: | Pleniewicz R COMMONWEALTH EDISON CO. |
| To: | Jordan E NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| References | |
| NUDOCS 9311100165 | |
| Download: ML20059H666 (9) | |
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1400 Opus Place
.4 Downers Grove, Illinois 60515 November 1,1993 Mr. Edward L. Jordan, Director Office of Analysis and Evaluation of Operational Data U.S. Nuclear Regulatory Commission Washington D.C.
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Subject:
Quad Cities Station Units 1 and 2 IPE Sensitivity Analysis for Quad Cities Station l
NRC Docket Nos. 50-254 and 50-265 Mr. Jordan, During the review of Ouad Cities Station, the NRC Diagnostic Evaluation Team (DET) provided a number of preliminary observations of equipment performance deficiencies in key safety systems. These observations, coupled with Commonwealth Edison (CECO) safety system vulnerability assessments and performance trends at Quad Cities Station, have led CECO to study the overall safety significance of these equipment performance' deficiencies in the key safety systems. The ideal tool for this study was the recently completed final draft of the Quad Cities Station Individual Plant Examination (IPE).
Commonwealth Edison (CECO) has evaluated the overall safety of Quad Cities Station utilizing the 1PE. Although Quad Cities Station has experienced recent equipment
- performance deficiencies, the information gained through this evaluation provides assurance i
that the existing plant condition is not reflective of a significant reduction in the safety j
margins. In addition, CECO believes that this information should be provided to you prior to the scheduled exit meeting of the DET at Quad Cities Station (November 8,1993).
The final draft of the Quad' Cities Station IPE indicates that, given th'e plant reliabil_ity data for Quad Cities Station through 1991, the resultant baseline Core Damage Frequency-l (CDF) is in the top quartile among U.S. BWRs (1.2 E-6),' and well within the safety goals established by the NRC (1.0 E-4). The IPE also demonstrates that no severe accident requiring remedial action exists. Therefore, CECO has concluded that operation of Quad.
Cities Station is well within accepted safety limits, due to the safety margins incorporated in i
the plant design, and the effectiveness of the emergency procedures.
CECO has also performed a sensitivity evaluation to quantitatively estimate the impact
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of recent equipment performance and degradation on the CDF. This evaluation I go 1
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E.L., Jordan 2
November 1,.1993'
. factored in a top level estimate of the 1992 and 1993 performance for the Emergency Diesel Generators (EDG), the High Pressure Coolant injection (HPCI) system,the Reactor Core Isolation Cooling (RCIC) system, and the Residual Heat Removal (RHR) system and i
RHR Service Water system (RHRSW). These systems were selected based upon the risk significance in the IPE and DET interest / observations.
1 The summary of this evaluation is provided in Attachment 1. The top level
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estimates for degraded equipment performance result in a CDF ~of 1.9 E-5, which is only sfiahtiv hiaher than the median baseline CDF value for other BWR IPEs'(1.8 E-5). This.
. l change in CDF, and the relative change in ranking among U.S BWRs, is illustrated in.
l. The evaluation also indicated that the planned installation of the Station a
Blackout EDGs and a SBO procedure enhancement would reduce the baseline CDF by.
approximately 40E However, Commonwealth Edison is not satisfied with equipment performance and degraded equipment at Quad Cities Station.
CECO has implemented; and will continue -
to implement, aggressive actions to restore degraded equipment and resolve long standing -
l equipment issues at Quad Cities Station.
l The Quad Cities Station IPE confirmed the EDGs are the most risk significant system. In the upcoming Unit 1 maintenance outage (November 8,1993), CECO will replace the Unit 1 EDG Cooling Water (EDGCW) pump. This will complete the y
replacement of all EDGCW pumps at Quad Cities Station. Also during the outage, CECO 1
will implement preventive and corrective maintenance activities on the EDGs, HPCI, RCIC, j
and RHR systems. These activities are listed in Attachment 3.
In addition to the sensitivity evaluation described above,' CECO has evaluated the historical trend of MOV failure rates at Quad Cities Station. The results of that evaluation are described in Attachments 4 and 5. This historical data is plotted as a quarter-by-o quarter comparison of the rolling 18-month failure rate (per component in-service hour).
These plots indicate that historic MOV performance at Quad Cities Station has been'
-i better than the CECO and industry averages. However, this trend changed during the -
fourth quarter of 1992. Nevertheless, the current MOV failure rate at Quad Cities Station is still comparable to the average failure rate for both CECO and the industry. Since the Quad Cities Station IPE utilized average failure rates from Quad Cities data through 1991
-(which are comparable tn the industry average), the conclusions of the IPE sensitivity study are further validated. Nevertheless, CECO has performed sensitivity studies to r
determine the impact of further increases in MOV failure rates above the base IPE values for all MOVs at Quad Cities Station. The results of these sensitivity studies indicate that even for substantial increases in failure rates (10 times the base value), the CDE would only increase by a factor of approximately 6.
Despite the information provided by the evaluation of historical MOV failure rates at Quad Cities Station, CECO is not satisfied with the negative trend in the MOV failure rate. To that end, CECO has performed MOV dP testing on six safety significant valves j
since August 1993 (see Attachment 3), and has scheduled considerable MOV dP testing i
during the Unit 1 and Unit 2 maintenance outages (November and December 1993 - see -
... E.L Jordan 3
November 1,1993
'M ) and the Unit'1 and Unit 2 refueling outages (March 1994 and September 1994). System importance measures, which were derived from the IPE, have been used as an input to the prioritization of this testing.
if you have any questions or comments prior to the DET Exit Meeting,' please contact Rich Pleniewicz at 309-654-2241 extension 3600.
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Rich Pleniewicz -
Site Vice President-Quad Cities Station i
Key Equipment Sensitivity Study; Unavailability Changes and Results BWR iPE Comparison :
Safety System Maintenance :
MOV Failure Rate; Quad Cities vs. Industry t :
MOV Failure Rate; Quad Cities vs. other CECO Nuclear Stations-cc:
T. Murley, Director - Office of Nuclear Reactor Regulation (NRR)
J. Martin, Regional Administrator - Region til' J. Zwolinski, Assistant Director for Region 111 Reactors - NRR J. Dyer, Project Director - NRR
-l A. B. Beach, Diagnostic Evaluation Team Leader - AEOD C. P. Patel, Project Manager - NRR T. E. Taylor, Senior Resident inspector - Quad Cities Office of Nuclear Safety-IDNS P
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i ATTACHMENT 1 Key Equipment Sensitivity Study l
Unavailability Changes and Results t
t Unavailability Estimated to increase Resultant CDF Increased by a Factor of; by a Factor of:
Diesel Generators 2.6 8.9
' I HPCI 4
1.7 RCIC 4
1.4 i
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Total CDF increased by a factor of 15.7 to 1.9 E-05.
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Notes on the above sensitivity runs:
- 1) The goal of the sensitivity study was to estimate the near-term future effects on CDF based on recent past increases in unavailability for these four systems.
- 2) Increases in unavailabilities were estimated by comparing unavailability data for 1992 and the first -
seven months of 1993 with past years data from the Quad Cities July Monthly Performance Report and with the baseline data used in the IPE.
- 3) The factor increases in unavailability used in the sensitMty study are a conservative projection of future unavailability for the following reasons:
l
- The INPO criteria for assigning unavailability was used; therefore, when a failure occurred, the system was considered unavailable from half-way since the last time the system ran successfully.
'l A considerable amount of unavailability in 1992 and 1993 was due to planned maintenance and modification actMty which is not expected to occur again.'
For the sake of simplicity in the sensitMty study, the increases in maintenance unavailability noted in 1992 and 1993 were also projected to cause proportional increases in fall to start and fall to run rates. For the Diesel Generators, a LER review confirmed the accuracy of this assumption.
- Since only about 1-1/2 years worth of data was examined, the unavailability increases are statistically biased toward the reduced availability of the most recent past.
- i
... - -. =.
ATTACIIMENT 2 Other HWR Comparison OC - Quad Cities Baseline IPE
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OC(M) - Quad Cities with modified unavailabilities for DGs, HPCI, RCIC, RHR l
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Quad Cities Station Safety System Maintenance L
Recently Completed Dynamic VOTES Testing Since August 1993, CECO has completed dynamic VOTES tests at Quad Cities Station on the following six safety system valves:
Unit 1 1001-18A & B (LPCI minimum flow) valves
- Unit 1 1001-34B and Unit 21001-34A & B (containment cooling) valves Unit 1 1301-60 (RCIC minimum flow) valve a
Planned Safety System Maintenance: Unit 1 and Unit 2 Maintenance Outages The Quad Cities Station Maintenance outages scheduled for November 1993 (Unit 1) and December 1993 (Unit 2) have been planned to address key materiel condition items on systems having a high impact upon safety.
Emergency Diesel Generators (EDGs) and AC Power
- Replacement of the Unit 1 Diesel Generator Cooling Water pump (all others were previously replaced).
- Replacement of Unit 1 Reserve Auxiliary Transformer 12.
- Replacement of all 20 engine power packs on Unit 1 and Unit 2 EDGs.
- Installation of field ground indication modification on Unit 2.
- Installation of modification on Unit 2 EDG fuel oil system to a!!ow for flexible hose installation.
l Inspection of current transformers in local diesel generator panels (Unit 1 and Unit 2).
- Installation of new digital tachometer instruments on local diesel panels (Unit 1 and Unit 2).
l
-j High Pressure Coolant injection (HPCI)
Dynamic VOTES tests of the Unit 1 and Unit 2 2301-3 valves (steam supply),
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the Unit 1 and Unit 2 2301-15 (injection) valves, and the Unit 12301-14 valve I
(minimum flow).
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- Refurbishment of Unit 1 motor speed changer (MSC) and motor gear unit (Unit 2 MSC previously inspccted).
- Replacement of motors on Unit 1 2301-36 and Unit 2 2301-35 valves (torus suction).
- Replacement of current Gemac flow and pressure transmitters to Rosemour.t models.
Replacement of obsolete oil pressure switches with new models.
Remount and repair Unit 2 solenoid valve SV-8.
Reactor Core Isolation Cooling (RCIC)
Dynamic VOTES tests of the Unit 1 1301-60 (minimum flow) and 1301-62
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(coo!ing water) valves.
l Upgrade of drain pot level switches (GE SIL 531).
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Upgrade of rupture disk (Unit 2).
Replacement of motors on Unit 1 1301-48 and 1301-49 (pump discharge) valves.
l Replacement of various air-operated valve diaphragms (preventive maintenance).
Inspection of barometric condenser internals.
Dynamic VOTES tests of the Unit 1 1001-16A & B (heat exchanger bypass) valves, Unit 1 and Unit 2 1001-28A & B and 1001-29A & B (LPCI injection) valves; and the Unit 21001-18A & B (minimum flow) valves.
Replacement of motor pinion, worm shaft gears, and motors for Unit 1 1001-34A and Unit 21001-34A & B (containment cooling) valves.
Replacement of gearings on Unit 1 1001-23B and 1001-26B, and Unit 21001-23A & B and 1001-26A & B (drywell spray) valves.
Replacement of obsolete room cooler thermostats with environmentally qualified temperature switches.
Addition of seal-in relays to Unit 1 and Unit 21001-16A & B valves.
t Installation of refurbished motors on the 1D and 2D RHR Service Water pumps.
ATTACHMENT 4 l
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MOV FAILURE RATE s
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