ML18036A553
| ML18036A553 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 03/20/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18036A551 | List: |
| References | |
| REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR NUDOCS 9203260278 | |
| Download: ML18036A553 (8) | |
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+**y4 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 ENCLOSURE SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT UNITS 1
AND 3 DOCKET NOS.
50-259 AND 50-296
- 1. 0 INTRODUCTION The Br owns Ferry Nuclear Plant (BFN), Units 1, 2 and 3, were shut down in 1985.
At that time, the Tennessee Valley Authority (the licensee) committed to keep BFN shut down until the NRC approved restarting the units.
After implementing NRC-approved restart
- programs, BFN Unit 2 started up in Nay 1991.
The licensee has recently submitted several restart programs to the NRC for BFN Units 1 and'.
Programs where the licensee has proposed significant deviations from the BFN Uni,t 2 precedent require staff review and approval.
This evaluation addresses the'roposed program for BFN Units 1
and 3 conduit and conduit supports;
- 2. 0 DISCUSSION AND EVALUATION During the BFN Unit 2 restart program for conduit, the licensee performed engineering evaluations of all BFN Unit 2 and common area conduit systems needed to achieve hot shutdown of BFN Unit 2 in the event of a design basis earthquake.
Because the licensee could not readily distinguish class lE
'onduit from non-class 1E conduit, all conduit and conduit supports in common plant areas and in specific areas of the reactor building, regardless of safety classification, were inspected and evaluated.
Questionable configura-tions were identified as outliers and dispositioned by performing rigorous analysis and/or physical modifications.
When the licensee evaluated the rod-hung systems, every system was identified as an outlier.
Rather than perform rigorous analysis of each rod-hung system, the licensee proposed to rigorously analyze several selected worst-case rod-hung conduit configurations as bounding cases for all BFN Unit 2 and common systems.
These bounding configu-rations included the worst attributes of the existing systems in BFN Unit 2 and common areas (i.e., long spans, large axial spans, mixed rod length, heavily loaded trapeze
- hangers, mixed support conditions such, as braced and.
unbraced trapezes).
The analyses of the bounding confi'gurations demonstrated that the as-built rod-hung systems were adequate.
By letter dated Nay 6, 1991 (Reference 1), the licensee submitted a restart program for conduit and conduit supports at BFN Units 1 and 3.
In its submittal, the licensee committed to perform inspections and engineering evaluations of all conduit in the BFN Unit 1 and 3 drywells and all areas of the reactor building which were not included in the BFN Unit 2 program.
The licensee stated that the inspections and evaluations would focus on physical attributes which resulted in modifications during the BFN Unit 2 program.
At I
92032b0278 920320 PDR ADOCK 05000259I PDR l
a meeting held on September 17, 1991, the licensee clarified its'rogram, and stated that, with the exception of rod-hung conduit systems, all conduit in the scope of the BFN Units 1 and 3 program would be qualified using the BFN Unit 2 implementation precedent.
This was noted in "the meeting summary report dated November 1,
1991.
The staff accepted this approach for qualifying conduit other than rod-hung conduit.
For rod-hung conduit systems in the scope of the BFN Unit 1 and 3 restart program, the licensee stated that it would perform a walk-through to ensure, that there were no missing rods.
The licensee stated that this approach was justified because the only problem identified with BFN Unit 2 rod-hung conduit was a single missing rod.
The staff did not consider this as adequate justification for not evaluating the rod-hung systems. in BFN Units 1 and 3, and -therefore did not accept the licensee's position 'for rod-hung systems.
Following discussions with the licensee regarding the staff's concern, the staff suggested that the licensee demonstrate that the rod-hung conduit systems in BFN Units 1 and 3 are enveloped by the BFN Unit 2. bounding configurations.
In a subsequent letter dated December 12, 1991 (Reference 2), the licensee described an alternative method to evaluate rod-hung conduit systems using a
seismic experience database developed by E(E, Inc.
EgE developed this database in conjunction with the generic resolution of Unresolved Safety Issue (USI) A-46, "Seismic gualification of Equipment in Operating Plants."
The licensee stated that the BFN Unit 2 worst-case configurations bounded the worst attributes found in the experience database.
The licensee'urther stated that the rod-hung conduit, in BFN Units 1 and 3 had been previously
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evaluated against the experience database and determined to be acceptable, and therefore, no further evaluation of this conduit is necessary.
The use of -the seismic experience'atabase approach was previously proposed by the licensee during the BFN Unit 2 conduit restart pt ogram.
However, the staff did not accept its use
- because, at that time, the experience database approach was being evaluated as part of a separate staff review of the proposed generic
-resolution to USI A-46.
The generic resolution of USI A-46 is still under staff review.
Therefore, the use of the experience database to resolve concerns with conduit at BFN Units 1 and 3 is not acceptable at this time..
By letter dated January 29, 1992 (Reference 3), the licensee submitted a
revised program for qualifying the conduit in BFN Units 1 and 3.
Based
'on this submittal and on a January 6,
1992 telephone conference between the staff and the licensee, it is the staff's understanding that the licensee will inspect and evaluate,all rod-hung conduit systems in the BFN Unit 1 and 3
restart scope.
These inspections and evaluations are intended to determine if all BFN Unit 1 and 3 rod-hung conduit systems are enveloped by the BFN Unit 2 bounding calculations.
The inspections will also confirm that there are no construction deficiencies (missing or improperly installed hardware) in these systems.
Any questionable configurations which are not clearly enveloped by the BFN Unit 2 bounding analyses will be further evaluated.
If necessary, physical modifications will be developed.
All conduit other than rod-hung conduit will be evaluated in accordance with the implementation precedent approved for the BFN Unit 2 program.
The resolution of identified discrepan-cies will be implemented prior to the restart of BFN Units 1 and 3.
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The staff concludes, that the proposed program is essential.ly equivalent to'the program. approved for the BFN Unit 2 restart.
Therefore, the staff finds that the licensee's proposed restart program is an acceptable basis for restart of BFN Units 1 and 3, pending proper implementation.
3.0 CONCLUSION
The staff has reviewed the l,icensee's proposed program to resolve conduit and conduit support issues and has determined that it is essentially equivalent to.
the program approved for the BFN Unit 2 restart.
Therefore, the staff finds that, if properly implemented, this proposed program is acceptable for BFN Units 1 and 3 restart.
It is noted that the licensee is required to resolve USI A-46 for BFN Units 1, 2,
and 3.
The licensee is a member of the Seismic gualification UtilityGroup (SHRUG),
and has previousiy indicated that it will address USI A-46 through'he generic resolution which was developed by the
- SHRUG, and which is currently under staff review.
The-resolution of USI A-46 is a post-restart commitment for BFN Units 1, 2 and 3.
Principal Contributor:
N. HcBrearty Dated:
Yiarch 20, 1992
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REFERENCES 1.
2.
3.
- Letter, E.
G. Wallace, TVA, to NRC, "Br'owns Ferry Nuclear Plant (BFN),
Program For Resolving Conduit and Conduit Supports Issue Prior to the Restart of Units 1 and 3," dated Nay 6, 1991.
- Letter,
Small Bore Piping Program,
- Tubing, And Conduit Support Plans for Units 1
=and 3 Additional Information,"'ated December 12, 1991.
Letter, 0. J. Zeringue, TVA, to NRC, "Browns Ferry Nuclear Plant (BFN)
Action Plan to Disposition Concerns Related to Units 1 and 3 Conduit and Conduit Support - Additional Information," dated January 29, 1992.
DISTRIBUTION Docket-Fi.l e--
NRC PDR Local PDR S. Varga G. Lainas F.
Hebdon B. Wilson C. Patterson N. Sanders D. Williams T. Ross OGC ACRS(10)
BFN Rdg. File L. Reyes 14-E-4 14-H-3 15-B-18 RII
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