ML20024C386
| ML20024C386 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 07/08/1983 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, TASK-2.K.3.28, TASK-TM NUDOCS 8307120575 | |
| Download: ML20024C386 (3) | |
Text
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. 5-TENNESSEE VALLEY AUTHORITY CH ATTANOOGA. TENNESSEE 37401 400 Chestnut Street Tower II July 8, 1983 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Mr. Denton:
In the Matter of the
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Docket Nos. 50-259 Tennessee Valley Authority
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50-260 50-296 By letter from D. B. Vassallo to H. G. Parris dated May 11, 1983, we received the NRC request for additional information regarding NUREG-0737, Item II.K.3.28, Qualification of ADS Accumulators.
Enclosed is our response for Browns Ferry Nuclear Plant.
Very truly yours, TENNESSEE VALLEY AUTHORITY L. M. Mills, nager Nuclear Licensing Subscribe gdsworqt b ore day of\\.
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Enclosure oc (Enclosure):
U.S. Nuclear Regulatory Commission Region II ATTN: James P. O'Reilly, Regional Administrator 101 Marietta Street, Suite 2900 Atlanta, Georgia 30303 Mr. R. J. Clark Browns Ferry Project Mar.ager U.S. Nuclear. Regulatory Commission 7920 Norfolk Avenue i
Bethesda, Maryland 20814
'I 8307120575 830708 PDR ADOCK 05000259 p
PDR An Equal Opportunity Employer
- o' ENCLOSURE Response to Request for Additional Information on Qualification of ADS Accumulator Systems Browns Ferry Nuclear Plant, Units 1, 2, and 3 In a letter from L. M. Mills to H. R. Denton, NRC, dated December 30, 1981, we discussed the two separate concerns of NUREG-0737, item II.K.3 28, namely, short-term and long-term operability requirements of the ADS valves and~ accumulators.
Tn addition to that discussion, the following is in direct responee to the request for additional information.
1.
Assuming an ambient drywell pressure of 35 psis (i.e., 70 percent of the drywell design pressure) for one hour, analytic and test results indicate that the ADS valves are conservatively capable of two actuations each. For an ambient drywell pressure of 0 psig, test results indicate that the ADS valves are conservatively capable of at least three more actuations each.
These values consider leakage, seismic events, and a harsh environment.
2.
Presuming that both the drywell air and control air systems are completely lost at a maximum assumed accumulator leakage rate,
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sufficient pressure for ADS actuation at an ambient drywell pressure of 35 psig could be maintained for at least 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> using only accumulators. - For normal containment pressures, the capabilities could be maintained for at least six hours.
2 The accumulators meet the FSAR requirement to provide the capability 6
for a ! minimum of five valve operations.
3.
Each of the six relief valves provided for automatic depressurization is equipped with a 1-gallon air accumulator and check valve i
arrangement. These accumulators are provided to ensure that the l
valves can be held open following failure of the air supply to the accumulators, and they are sized to contain sufficient air for a i
minimum of five valve operations. The first and second actuations j
are assumed to occur with drywell pressure at 35 psig and subsequent actuations with the drywell at 0 psig. Accumulators are not required
- for the relief valves not used for automatic depressurization. The 1
relief valves which are a part of the ADS normally receive their j
motive air from the drywell control air system. The air pressure in j
the accumulatora is continuously monitored by a pressure switch which i
annunciates in the control-room on low air pressure (70 psig).
The drywell control air system is also continuously monitored for low j
air pressure by means of a pressure switch located in the system j
downstream of the receivers and which annunciates in the control room.
A manual transfer can also be made to the plant control air system as another backup for control air.
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4.
The accumulator leakage criteria of 10 psi /hr is sufficient to ensure that the ADS valves will have the capability to actuate as described by the FSAR for design basis events with a total loss of normal supply air to the valves.
5.
The ADS accumulators and associated components were procured and installed to seismic category 1 standards; therefore, the leakage is not expected to increase as a result of a seismic event.
4 In addition, the components were procured to withstand design basis conditions in the drywell and therefore no increase in leakage is expected.
6.
Based upon the seismic and environmental procurement requirements for the ADS accumulators and associated components as described in No. 5 above, no increase in leakage is expected for seismic events or a harsh environment.
i 7.
No credit is taken for nonsafety-related equipment and instrumentation in using the allowable leakage criteria.
8.
The ADS accumulator leak test is performed once per operating cycle.
Each accumulator is charged to normal operating pressure (90 psig),
the supply air source is isolated and vented, and the accumulator pressure decay is observed. The allowable leakage criteria is less than 10 psi during the first hour.
9 The ADS accumulator system has an individual pressure instrument associated with each accumulator which initiates a common alarm in the control room on low pressure. Once per operating cycle, the pressure switches are calibrated using a standard pressure source.
Instructions include verification that the alarm functions when the switches are activated.
10.
The ADS accumulator system, associated equipment, and control.
circuitry were procured and installed as seismic category 1 components.
11.
The electrical and aechanical components in the ADS accumulator system, associated equipment, and control circuitry are environ-mentally qualified for conditions associated with normal operation, maintenance, testing, and postulated accidents as analyzed in the FSAR.
. 12..The ADS valves, accumulators, associated equipment, and instrumen-tation are capable of performing their function as described in the FSAR during and following an accident situation while taking no credit a
for nonsafety-related equipment and instrumentation.
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