ML18032A340
| ML18032A340 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 05/29/1987 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| GL-87-05, GL-87-5, TAC-R00161, TAC-R00162, TAC-R00163, TAC-R161, TAC-R162, TAC-R163, NUDOCS 8706080069 | |
| Download: ML18032A340 (9) | |
Text
Ot y REGULATORY I RMATION DISTRIBUTION BYB I (RIDB)
ACCESBIQN NBR: 8706080069 DOC. DATE: 87/05/29 NOTARIZED:
NO DOCKET FACIL: 50-259 Browns Ferry Nuclear Pouer Btationi Unit 1>
Tennessee 05000259 50-260 Browns Ferry Nuclear Power Stationi Unit 2>
Tennessee 05000260 50-296 Browns Ferry Nuclear Power Stations Unit 3>
Tennessee 05000296 AUTH. NAME AUTHOR AFFILIATION QRIDLEY> R.
Tennessee Valley Authority RECIP. NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)
BUBJECT:
Responds to Generic Ltr 87-05 request for addi info re measures to mitigate Sc/or identi fg potential degradation of.
Mark I drgwells. Util plans to perform ultrasonic thickness measurements.
Extension of due date coor dinated on 870513.
DISTRIBUTION CODE:
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4 TENNESSEE VALLEYAUTHORITY CHATTANOOGA. TENNESSEE 37401 5N 157B Lookout Place Ml 29 1987 U.S. Nuclear Regulatory Commission ATTN:
Document Control Desk Washington, D.C.
20555 Gentlemen:
Docket Nos.
50-259 50-260 50-296 In the Matter of
)
Tennessee Valley Authority
)
I i BROWNS FERRY NUCLEAR PLANT (BFN) REQUEST FOR ADDITIONAL INFORMATION MEASURES TO MITIGATE AND/OR IDENTIFY POTENTIAL DEGRADATION OF MARK I DRYWELLS (GENERIC LETTER 87-05)
As requested by Generic Letter 87-05 from R.
M. Bernero to All Licensees of Operating Reactors dated March 12, 1987, we are submitting the enclosed information.
The generic letter requested information regarding our intended actions to determine if Mark I drywell shells have degraded by the corrosion mechanism described in the generic letter and our plans to minimize this potential problem.
Current BFN plans are to perform ultrasonic thickness measurements on each of its drywells to ensure their structural integrity and to continue periodic visual inspections to identify the potential for a corrosive situation.
Please note that a short extension to the established due date was coordinated on May 13, 1987. If you have any questions or need further information, please telephone J. L. Turner, BFN Site Licensing, (205) 729-2853.
Very truly yours, TENNESSEE VALLEY AUTHORITY
- f. R. Gridley, Director uclear Safety and Licensing Enclosure cc:
See page 2
8706080069 870529 PDR
- DOCK 05000259 P
PDR o90 An Equal Opportunity Employer
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U.S. Nuclear Regulatory Commission cc (Enclosure)
Mr. G.
G. Zech, Assistant Director Regional Inspections Division of TVA Projects Office of Special Projects U.S. Nuclear Regulatory Commission Region II 101 Marietta St.,
NW, Suite 2900 Atlanta, Georgia 30323 MN R9 1987 Mr. J. A. Zwolinski, Assistant Director for Projects Division of TVA Projects Office of Special Projects U.S. Nuclear Regulatory Commission 4350 East West Highway EWW 322
- Bethesda, Maryland 20814 Browns Ferry Resident Inspector Browns Ferry Nuclear Plant P.O.
Box 311
- Athens, Alabama 35611
I
ENCLOSURE
RESPONSE
TO REQUEST FOR ADDITIONAL INFORMATION DATED MARCH 12, 1987 GENERIC LETTER 87-05 BROMNS FERRY NUCLEAR PLANT (BFN)
RE VEST NO.
1 Provide a discussion of your current program and any future plans for determining if the drain lines that. were provided at your facility for removing any leakage that may result from refueling or from spillage of water:
into the gap between the drywell and the surrounding concrete or from the sand cushion itself are unplugged and functioning=-as designed.
RESPONSE
The only drains that prevent water accumulation in the sand cushion are the sand cushion drains themselves.
The sand cushion drains are sand-filled and have a screen to keep the sand in the drain while passing water.
The design precludes functional testing of the drains.
However, the design of the BFN drains is such that they would not become plugged to the extent they could not perform their function.
In order for the drains to become plugged, debxis would have to pass through the sand cushion or travel vertically up the drain from the floor, both of which are not feasible.
There are only two elbows in the sand cushion drain and neither form traps for stagnation to occur.
Therefore, a functional test of the drains is not warranted.
RE VEST NO.
2 Provide a discussion of preventive maintenance and inspection activities that are currently performed or are planned to minimize the possibility of leakage from the refueling cavity past the various seals and gaskets that might be present.
RESPONSE
Preventative maintenance on the various seals and gaskets that prevent..leakage into the gap between the drywell and surrounding concrete is impracti:cal at BFN.
The most efficient method of determining whether the seals and gaskets are performing their function is to observe the drains from the gap.
Therefore, the current BFN preventative maintenance and inspection activities pertaining to this area consists of observation of the appropriate drains.
There are only two ways for water to drain from the gap.
One way is through the sand cushion drains.
The second way is thxough the vent sleeve drains.
A vent sleeve is a steel sleeve which contains a dxywell to torus vent.
Although the vent sleeve drain is not used to prevent, water from entering the sand cushion, water can run along the outside of the vent into the vent sleeve area.
Both these drains terminate in the basement of the reactor building and drain into the reactor building floor drain sump and are included in our inleakage inspection pxogram. If drainage is observed, action can be taken to identify and stop the leak.
Drainage has recently been observed from both the sand cushion drains and vent sleeve drains of unit 1.
The ultrasonic tests described below will determine if any damage to the dxywell has occurred.
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RE VEST NO.
3 Confirm the information listed in table 1 is correct with regard to your facility.
RESPONSE
The information pertaining to BFN which is contained in Table 1 of Generic Letter 87-05 is correct.
The gap between the drywell and surrounding concrete contains polyurethane foam.
In the lower regions of the drywell, the gap is filled with fiberglass'instead of polyurethane:;foam.~
The fiberglass extends down to the top of the sand cushion.
Polyethylene covers the top of the sand transition zone but does not prevent water from entering.
I RE UEST OF MARK I OWNERS WHOSE DESIGNS ARE SUCH THAT THE SAND CUSION IS OPEN TO GAP BETWEEN THE DRYWELL AND SURROUNDING CONCRETE Provide any plans for performing ultrasonic thicknessmeasurements of the drywell shell plates adjacent to the sand cushion or any other proposed actions to ascertain if plate degradation has occurred.
Since the degradation that has occurred at Oyster Creek is localized, sufficient details should be included to show that the sampling basis for ultrasonic thickness measurements is. adequate in terms of size and test location.
RESPONSE
Ultrasonic thickness measurements are scheduled in the near future for each unit.
Our current plans are to examine our drywells"in six areas, each six inches circumferentially by. four inches vertically.
Three of the six areas are located directly above the sand cushion drains and the remaining three areas are located at a mid-distance between two drains.
Refer to the attached drawing for location of the six areas.
These six areas will be immediately above the concrete floor of the drywell which correspond to the top portion -of the sand cushion.
Each area will be divided into a grid of. one-inch squares~
and each square is to,be tested.
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