ML18025B894

Proposed Tech Spec Changes Adding Diverse Differential Pressure Switches & Installation of More Reliable Float Switches to Initiate Scram on High Level in Scram Discharge Instrument Vol

ML18025B894
Person / Time
Site:	Browns Ferry
Issue date:	11/17/1982
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML18025B893	List: ML18025B892 ML18025B894
References
NUDOCS 8211230316
Download: ML18025B894 (5)

Text

ENCLOSURE 1 PROPOSED TECHNICAL SPECIFICATION REVISION TVA BFNP TS 179 SUPPLEMENT 1 BROWNS FERRY NUCLEAR PLANT UNIT 2 7 8211230316 821117 PDR ADOCK 0500028&'

PDR

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h VV

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LIHITING CONDITIONS FOR OPERATION SURVEILLANCE RFQUIREt'ANTS F 3 !ted cttvttv Contro! C ~ 3 ttcse.t! v~tt Cnsvt tO!

C. If Specificst!ons 3. 3.. snd . D E. Surveillancr requirements are

~ bove csnnot be nlet . sn ozdst ly as specified in 4.3.C and .D, shucdovn shsll be !a!t!sttd snd above.

che reactor shsil be In the shutdown conditLon vfthin 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

F. Scram Dischar e volume (SDV) F. Seeem Illselme~e Volume (gDV)

1. The scram discharge volume I.a. The sctam discharge volume drain and vent valves shall drain and vent valves shall be operable any time that be verified open prior to the reactor protection each startup and monthly system is required to be thereafter. The valves may be closed intermittently operable except as specified foz testing not to exceed in 3.3.F.2. I hour in any 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period during operation.

2. In the event any SDV drain or vent valve becomes b. The scram discharge volume inoperable, reactor operatio drain and vent valves shall may continue provided the be demonstrated operable redundant drain or vent monthly.

valve is operable.

2. When it is determined that

3. If redundant drain or vent . any SDV drain or vent valve is inoperable, the redundant valves become inoperable, the reactor shall be in drain or vent valve shall hot standby within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. be demonstrated operable immediately and weekly thereafter.

3. No additional surveillance required.

126

ENCLOSURE 2 Descri tion and Justification, During the unit 2 reload 4 outage, the scram discharge volumes (SDVs) and scram discharge instrument volumes (SDIVs) are being modified to address

'inadequacies identified by the partial rod insertion event on Browns Ferry Nuclear Plant unit 3 in June 1980. One of the modifications includes adding another valve in series to the existing drain and vent valves on the SDV and SDIV. Another modification includes adding diverse differential pressure (dP) switches and installing more reliable float switches to initiate a scram on a high level in the SDIV.

As des1gned, the drain and vent valves serve two purposes neither of which is a direct safety function. The first purpose, when the valves are in the open position, is to provide a positive means of maintaining the SDV drained to ensure adequate volume to accept water discharged during a scram. The direct safety function of adequate volume is ensured, however, by the redundant and diverse SDIV level instruments described above.

The second purpose, when the valves are in the closed position, is to limit the amount of water discharged to the radioactive waste system following a scram. There is no direct safety funotion associated with this purpose, but two othe> means are designed to alleviate this operational inconvenience. The first is the control rod drive (CRD) seal design which serves as the reactor pressure boundary to limit leakage. The second is the proven ability to reset the scram under most conditions in less than five minutes thereby closing the scram outlet valves and stopping flow to the SDV.

Implementation of the SDV and SDIY modi.fications adding the redundant vent and drain valves provides increased assurance that the second purpose will be fulfilled while decreasing the probability of fulfillment of the -first purpose. Given the high level of confidence of the level switches meeting the first purpose versus the somewhat lower confidence of being able to reset the scram and fulfilling the second purpose, it is prudent to specify and maintain a certain level of operability to meet the second purpose. In the case of the drain and vent valves not serving a direct safety function, one of a redundant pair of valves is fully adequate for continued power operation with increased surveillanoe of the operable valve.

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