ML20140F632

Responds to J Zwolinski Note & TVA Investigation Rept Re Snp Pressurizer Drain Down Event of 970324

ML20140F632
Person / Time
Site:	Sequoyah
Issue date:	05/04/1997
From:	Blanch P AFFILIATION NOT ASSIGNED
To:	Zwolinski J NRC (Affiliation Not Assigned)
Shared Package
ML20140F623	List: ML20140F619 ML20140F627 ML20140F632 ML20140F635 ML20140F647
References
NUDOCS 9706130176
Download: ML20140F632 (1)

Text

vw.

To: .

JZ <JAZWOLGrol.com>

Date: 5/4/9711:57am

. $ubj;ct: SEQUOYAH PRESSURIZER DRAINDOWN April 24,1997 John:

I have reviewed your note (enclosed) and attachment from the above event.

From my review, TVA did not identify the root cause of this draindown event. The problem is i

that during normal operation, the condensate pots do not function as designed. They are bound by non-condensable gases which are then absorbed in the reference legs. The

probism was aggravated by the reduction in pressure from 325# to 30# just prior to the event.

1 This caused expansion of the gas and partially volded the reference leg.

l j Your statement;"[t]s not safety-related and has no control or protective functions."is true

! however the failure of this device is likely to result in a event that has severe safety I consequences. Had this event continued, all core cooling could have been lost resulting in l l unknown consequences. Another logical question is why was the RVLIS indication ignored.  ;

) l

, All of this information has been known to the NRC and the licensees since Westinghouse l l issued a notice in Feb.1988 (I think.). This was the subject of many meetings with the staff ,

j and the full Commission. l l

9 l was given assurance by the NRC that all of these problems were resolved long ago and that l l every licensee had corrected the problem.

l l If TVA wants to confirm the root cause to be non-functioning condensate pots it is a simple matter of measuring the pot extemal temperature and assuring it is close to saturation.

i i Both TVA and the NRC need to go back and review the long history of this problem and report i on the true root cause of the false levelindication.

i

As we discussed on the phone, I am more than willing to assist the licensee and the NRC should you need additional technical assessment.

l

! NOTE TO: Paul Blanch FROM: John Zwolinski

SUBJECT:

SEQUOYAH PRESSURIZER DRAINDOWN EVENT OF MARCH 24,1997

'$$ In response to your interest to the subject event, I am sending you the attached TVA 2@ investigation report on the causes of the event. The staff is in the process of reviewing the y report and will make a determination whether any NRC follow-up action is appropriate, either go on a plant specific or generic basis g it may not have been obvious from the NRC moming report referenced in your e-mail to me or March 29 that the instrument involved (cold-calibrated pressurizer level) is not safety-related Od and has no control or protective functions. On the other hand, the three safety-related 8@ (hot calibrated) pressurizer level instruments have a bellows seal configuration that would 58; prevent noncondensable gases from reducing the level in the reference leg as occurred on Era the cold-calibrated instrument on March 24 at Sequoyah. Refer to the schematic diagram following page 22 of the attached report that shows one the cold-calibrated instrument o (1-LT-68-443F) as well as one channel of the hot calibrated levelinstrument (1 LT-68 335) 1 if you have any questions on the attached report or the event, feel free to contact the NRR Project Manager for Sequoyah. He can be reached at (301) 415-2010 or at e-mail address RWH@NRC. gov.

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