ML18036A663
| ML18036A663 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 04/08/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18036A661 | List: |
| References | |
| NUDOCS 9204210015 | |
| Download: ML18036A663 (7) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, O. C. 20555 ENCLOSURE 2
SAFETY V
UATION BY TH OFFIC OF NUCLEAR REACTOR REGULATION ELECTRICAL CABLE SEPARATION ISSUES BROWNS F
RRY NUC EAR PLANT - UNIT NOS.
1 AND 3 DOCK T NOS.
50-259 AND 50-296 Introduction By letter dated Hay 10,
- 1991, the Tennessee Valley Authority (TVA) provided its action plans to resolve electrical cable separation issues for the Browns Ferry Nuclear Plant (BFN) Units 1
and 3.
The NRC staff safety evaluations of these action plans are documented below.
These safety evaluations considered similar issues and action plans previously reviewed by the NRC staff for restart of Browns Ferry Unit 2 restart, prior staff safety evaluations and inspection results for these issues and action plans, and the fact that the specific cable separation design criteria and installation procedures and practices for the three Browns Ferry units were essentially identical.
Back round Informatio TVA identified instances where electrical separation requirements were not met at the Browns Ferry Nuclear plants.
These discrepancies were discovered while implementing design changes and conducting reviews as part of the BFN Unit 2 restart effort.
These discrepancies were documented in Licensee Event Report Number 88-032, dated October 21,
- 1988, and in subsequent Condition Adverse to guality Reports.
The Tennessee Valley Authority submitted to the NRC their cable separation report which described the TVA action plan for evaluating the problem of cable separation and correcting identified discrepancies, for restart of Browns Ferry Unit 2.
TVA's action plan for resolving cable separation discrepancies at Browns Ferry Unit 2 consisted of categorizing discrepancies and identifying populations of cables susceptible to these discrepancies followed by an evaluation using one of three methods.
These methods were:
1)
%~+view of 100 percent of the cable population, 2)
A generic analysis to demonstrate the absence of safety concerns, and 3)
A random sample of the cable population.
The TVA action plan program resulted in 12 categories of cable separation discrepancy evaluations.
The categories of discrepancy evaluations were:
9204210015 920408 PDR ADOCK 05000259 P
3) 4)
5) 6)
7)
A review of field verified cable routing data from TVA cable ampacity and Appendix R programs.
A 100 percent review of V4/V5 cables which originate from safety related power supplies.
(Explanations are provided in the attached Appendix for V4, V5, V3, Vl and V2 cables.)
A random sample of nondivisional V4/V5 cables which originate from nonsafety-related power supplies.
A 100 percent review of V3 nondivisional cables which originate from safety-related power supplies.
A random sample of nondivisional V3 cables which originate from nonsafety-related power supplies.
A generic analysis of typical nondivisional Vl/V2 circuits which originate from both safety-related and nonsafety-related power supplies.
A 100 percent review of cables designated with an "IE" or "IES" suffix.
8) 9)
10) 12)
A 100 percent review of nondivisional V4/V5 cables contained in the project g-list.
A random sample of nondivisional V3 cables contained in the project g-list.
A random sample of nondivisional Vl/V2 cables contained in the project g-list.
A generic analysis of typical divisional Vl/V2 circuits.
A review of divisional and nondivisional cable trays that physi-cally connect.
The results of TVA's discrepancy evaluations of the categories listed above, along with implementation of corrective actions where appropriate, provided reasonable assurance with a high level of confidence that the cables required for Browns Felly Unit 2 operation were routed in accordance with existing separation crf4eria.
Furthermore, based on the staff's safety evaluation and inspections of the TVA cable separation
- program, the staff concluded in NUREG 1232, Volume 3, Supplement 2, dated January 23, 1991, that the TVA program to identify cable separation discrepancies against design requirements, and associated corrective actions to resolve those discrepan-
- cies, were acceptable.
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Browns Ferr
't nd 3 Se aratio Discre ancies to be Resolved in Accor-dance with th rowns Ferr Unit m lementation Precedent For Browns Ferry Units 1 and 3, seven categories of separation discrepancy evaluations are to be resolved in accordance with the Browns Ferry Unit 2 action plan and implementation precedent prior to loading fuel in the respective units.
These seven discrepancy categories are identified in the above background information as Items 2, 3, 4, 5, 6, 7, and 11.
Based on previous staff review, evaluation, and inspection activities, and results of the TVA's action plans as implemented at Browns Ferry Unit 2 for the seven identified separation discrepancies, the staff concludes that the TVA's proposed corrective action plan, when properly implemented, will be ade-quate to satisfactorily resolve these discrepancies for Browns Ferry Units 1
and 3.
Browns Ferr Units 1
and 3
Se aration Discre ancies Where Resolu io W l Deviate from the Brow s Ferr Unit 2 Im lementation Precedent The Browns Ferry Units 1 and 3 action plans and resulting implementation for the remaining five separation discrepancy categories deviate from the Browns Ferry Unit 2 precedent.
These categories and deviations are addressed below.
Review of Field Verified Cable Routing Data from the TVA Cable Ampacity and Appendix R Programs The Browns Ferry Unit 2 resolution for this issue consisted of a review of field verified. cable routing data from the ampacity and Appendix R
programs.
This review provided a 95/95 confidence level that the Unit 2 cable schedule drawings were adequate to provide design information used as input for the other separation evaluations.
For Browns Ferry Units 1
and 3, the cable and conduit database is the Consolidated Cable Routing System (CCRS).
Information from the CCRS is to be used to establish a
working database for use during the evaluation process.
This database information is to be validated for divisional separation by analyzing two random samples that are to be confirmed by walkdown and/or signal tracing ta establish conformance with the relevant design criteria.
Random samples to be analyzed are to include safety-related, associated, and non-safety cables.
The acceptance criterion for this validation is a 95/95.,mnfidence level that the cables are routed consistent with the functimfj) design criteria.
This confidence level is the same as was used fot', Srowns Ferry Unit 2.
Following this validation, the CCRS is to be used'o provide input information necessary for the remaining evaluations.
Any corrective actions for Browns Ferry Units 1 and 3 are to be implemented prior to restart of the respective unit.
Based on the action plan as described above and the same 95/95 confid-ence methodology used for Br owns Ferry Unit 2, the staff considers the proposed actions adequate to satisfactorily resolve the cable routing validation issue for Browns Ferry Units 1 and 3 pending proper implementation.
Nondivisional Vl, V2, V3, V4, and V5 Cables Contained in the Prospect Q-List The Browns Ferry Unit 2 Q-list was issued prior to the separation evaluation and identified a number of nondivisional cables as safety related.
Evaluations of the identified cables were performed to determine if they were safety related and, if so, the cables were subsequently routed correctly.
For Browns Ferry Units I and 3, the Q-list will establish a list of equipment and device identifications for safety related and quality related systems.
Then, circuit block diagrams are to be analyzed to identify each cable required in support of the "Q" device functions.
The resultant cable list is to be compared against the cable data base to determine if cables are correctly identified as divisional. If it is determined that a change in divisional status is required, then the respective cables are to be evaluated against the separation criteria and appropriate corrective actions taken.
Necessary corrective actions for Browns Ferry Units I and 3 are to be implemented prior to restart of the respective unit.
We consider the above action plan adequate to satisfactorily resolve the nondivisional cable issue for Browns Ferry Units I and 3 when implemented properly.
Evaluation of Cables Contained in Divisional and Hondivisional Cable Trays that Physically Connect While performing evaluations associated with the adequacy of the cable and conduit database, TVA identified certain Browns Ferry Unit 3 divisional cables routed in nondivisional cable trays.
Further TVA review determined that this problem was associated with the Browns Ferry Unit 3 automatic cable routing program where a node assignment was made at an intersection of a safety and nonsafety cable tray.
A review of Browns Ferry Units I, 2, and 3 was performed to by TVA to identify all of these unique situations and evaluations were performed for all affected cables.
These TVA evaluations found certain dis-crepanc$ es to the separation criteria, and TVA either initiated design-.eqdifications to correct the discrepancies or opened circuit breaker'i.'.to isolate cables not required for Browns Ferry Unit 2 restart.
ApproprAite corrective actions for Browns Ferry Units I and 3 for those cable separation discrepancies resolved by opening circuit breakers are to be implemented prior to restart of the respective unit.
The staff considers the above actions to be adequate, pending further NRC evaluation of TVA's specific corrective actions to address the cable separa-tion discrepancies resolved for Units 1 and 3 that were previously resolved for restart of Unit 2.
Principal Contributor:
F. Ashe Dated. April 8, 1992
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ATTACHMENT TO ENCLOSURE 2
Oefinitions of Vl V2 V3 V4 and V5 Cable Grou s
Group Oefinition Vl Resistance temperature detector and thermocouple cables.
V2 Instrumentation cables.
V3 Electrical control circuit cables.
V4 Low voltage cables (600 volts and less).
V5 Medium voltage (4160 volt) cables.