ML19332F003
| ML19332F003 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 12/04/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19332E999 | List: |
| References | |
| NUDOCS 8912130264 | |
| Download: ML19332F003 (3) | |
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO FACILITY OPERATING LICENSE NPF-43 DETROIT EDISON COMPANY WOLVERINE POWER SUPPLY COOPERATIVE. INCORPORATED FERMI-2 DOCKET NO. 50-341 L
1 ^. 0 L INTRODUCTION p
By letters dated September 12 and 28,1989, the licensee submitted both a control L
system comon power supply and a common sensor failure evaluation report. This report supplements the existing Fermi-2 Updated Final Safety Analysis Report (USFAR) Chapter 15 accident analyses and addresses condition 2.C 8 of the Fermi-2 operating license regarding multiple control system failures. These e
reports were requested because of staff concerns that a failure or malfunction of a power. source, sensor or instrument line (variable or reference leg) comon to two or more control systems may result in multiple control system failures not bounded by the UFSAR Chapter 15 safety analysis.
2.0- DISCUSS 10N l
The analysis and methodology usod by the licensee for the comon power and comon sensor. study utilized the event-consequence logic of the Fermi-2 UFSAR i
Chapter 15 analysis. The logic chain started from a specific source (comon sensor line/ power supply failure) instead of a' system condition (feedwater runout). The licensee identified control systems which could impact critical reactor. parameters (water level, pressure, power / flux) and then identified the sensors, sensor lines. or power supplies that were comon to these systems.
This listing was analyzed to detemine the most conservative failure that could be considered a credible event. The analysis consisted of systematically failing each comon sensor line or power supply and reviewing the postulated failure to ensure that it was bounded by the Chapter 15 analyses. The_ review by the staff utilized the design bases, functional control diagrams, single lines diagrams, P& IDS, NUREG/CR-5112 Generic Issue 101, Boiling Water Reactor Water Level Sensing Line Break and Single Failure," and the Fermi-2 UFSAR in the evaluation of the referenced control system failure analyses. The staff review consisted of reviewing the postulated failures for 27 comon sensor lines and 95 power supply /dist-panel / busses identified by the licensee and confirmed that these events were bounded by Chapter 15 analyses.
3.0 EVALUATION The common sensor failure analysis report identified reactor process sensor lines commonly shared by two or more plant control systems, of which at least 8912130264 891204 PDR ADOCK 05000341 P
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one of'the systems was ncn-safety. The bounding failure for each sensor analped was a complete and instantaneous break or plugged sensor line during normal full power reactor operation.
For this evaluation a broken line to a pressure transducer results in a low pressure indication. A broken line to a differential pressure transducer results in maximum differential pressure if the reference
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leg is broken and minimum differential pressure if the variable leg is broken.
A broken line to a differential pressure transducer utilized as a liquid level sensor results in an indicated high water level if the reference leg is broken and a low level indication if the variable leg is broken.
Plugged lines are considered 100% plugged, causing sensors to be inaccurate under changing pressure conditions. This methodology provided 27 instrument lines ccnon to l
two or more control systems. Of the transient events noted only two scenarios
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were not specifically bounded by Chepter 15 events.
Both were essentially the sarre but involved alternate char.nels of the same level parameter. When the variable leg of instruments LXEN0g1A and C or B and 0 is broken the reactor level will read downscale for these instrun:ents. This downscale reading activatesaLO-LEVEL (L-1,L-2)channelA&Corchannel080tripwhichinitiates i
a HPCI and RCIC start. Chapter 15 of the Fermi-2 UFSAR does not address both HPCI and RCIC starting inadvertently, but does discuss an inadvertant HPCI start, j
Since the flow of RCIC is 10% of HPCI flow and an L-1 trip will initiate MSIV closure causing a reactor scram, the overall failure mode is bounded by Chapter 15 ar.alysis.
The results cf the con.on sensor analysis den'onstrate that the ider.tified failures ere bounded by the event analyses described in the Ferr.1-2 Chapter 15 l'FSAR.
In addition, each postulated sensor line failure was subjected to an additional single failure analysis. These results were evaluated by the staff and found to be acceptable.
It should be noted that for Tabit 1.4 of the concon senscr line failure ar.alysis e. valuation sumary, the results for sensor line 3 are as shown when feedwater control is aligned to A not B for both broken and plugged instrument lines.
The cotton power supply failure analysis report identified control syster power supplies that are shared by two or more plant control systens.
Like the comon sensor /line study the common supply analysis used the same event-consequence
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icgic, but from a specific power source. The conron supply ar.alysis used as a starting point the combined effects of a failure at the lowest bus level, then the next higher bus was postulated to fail and the total failure effects were again analyzed. This process was continued up to the highest bus level identified. As a result of this analysis it was found that all postulated events were bounded by Chapter 15 analyses. However, a discrepancy exists with Fermi-2 Chapters 15 and 10 which state that the bypass system is designed such that a single random failure results in only one steam bypass valve failino to of bus 2PC3(+)y te this[ the comon power supply study revealed that a failure open. Contrar
-17, 2PC3
)-16 or H11P633 would result in a turbine trip and reactor scram without the turbine steam bypass valves opening. The Fermi-2 Chapter 15 addresses this event in Section 15.2.3.1.2.3, turbine trip withcut bypass sensitivity analysis, but Fermi-2 UFSAR Sections 15.2.3.1.2.2, 15.2.3.1.2.3 end 10.4.4 reference only single steam bypass valve failures.
The Fermi-2 l'FSAR may need to be revised to eliminate these discrepancies.
Althcugh new trcnsient events were postulated as a result of the failure cf couen control system power supplies, it was concluded that the net effects are o
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beunded by UFSAR Chapter 15 events.
In addition, after each comon power source failure event was identified an additional single failure evaluation was performed to deterinine if an additional component failure would result-in ovents not previously identified in the Chapter 15 analyses. These additional evaluatiers did not reveal _any events that exceeded the bounds of Chapter 15.
4.0 CONCLUSION
Based on our review we have concluded, with reasonable assurance, that a failure in any of the referenced control systerns is bounded by the analysis presented in Chapter 15 of the Fermi-2 UFSAR. The staff finds the common design configuration of the identified control systern power supplies, sensors and sensor lines _ acceptable and, therefore, considers TAC 59611 and 74835 resolved.
Principal Contributor:
C. Doctt Date: December 4, 1989 l
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