ML20140F632
| 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: |
| 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
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
issued a notice in Feb.1988 (I think.). This was the subject of many meetings with the staff j
and the full Commission.
l 9
l was given assurance by the NRC that all of these problems were resolved long ago and that l
every licensee had corrected the problem.
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 (1-LT-68-443F) as well as one channel of the hot calibrated levelinstrument (1 LT-68 335) o 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.
.