ML20140F627
| ML20140F627 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/29/1997 |
| From: | Blanch P AFFILIATION NOT ASSIGNED |
| To: | Zwolinski J NRC (Affiliation Not Assigned) |
| Shared Package | |
| ML20140F623 | List: |
| References | |
| NUDOCS 9706130172 | |
| Download: ML20140F627 (1) | |
Text
_
. ; From:
PAUL BLANCH <PMBLANCH@ix.netcom.com>
To:
WND2.WNP3(jaz)
Date:
3/29/97 4:56am 1
Subject:
SEQUOYAH 1 RCS PARTIAL DRAIN DOWN
]
3/29/97 John A. Zwolinski, Deputy Director Division of Reactor Projects-1/11 Office of Nuclear Reactor Regulation Washington DC 20555-0001 1
John:
l received the following last week.
SEQUOYAH 1 RCS PARTIAL DRAIN DOWN. On 3/23/97,in preparation for = reactor vessel disassembly, operators started to reduce the RCS = inventory from 56 % to 25 % Pressurizer level by procedure using the = cold calibrated instrument. After a half hour, operators noticed the = cold calibrated Pressurizer levelindication had stopped decreasing = and was steady at about 34 %. The hot calibrated Pressurizer level = indications were 0 %, but were not required to be monitored by = procedure. The operators observed Reactor Vessel Level Indication at =
92 %, and stopped the drain evolution upon realizing the level = discrepancy and initiated filling. It was determined the RCS level = bad drained to approximately 3 feet above the top of the Reactor =
Vessel flange. This represents about 4000 gallons drained below the = intended amount.
Shutdown cooling was not affected during the event. =
The licensee identified the reference leg for cold calibrated =
Pressurizer level instrument was not filled and is investigating the = root cause. [NRC Headquarters Report]
This appears to be the same problem I identified in 1989 at Millstone =
Unit 3. Westinghouse also identified this problem in February of =
1988. Bill Russell determined this not to be a problem in 1992. This = appears to be related to inoperable cold condensate pots. The full =
Commission refused to require any plants to conduct an operability = determination.
I suspect that the licensee and the NRC will find that the condensate = pot was cold and no make-up was being supplied to keep the reference = leg full. As a result of minor leakage, the reference leg slowly lost = level. This was not detected as the cold calibrated pressurizer level
= is not used during normal operation. This is the same problem = identified on Millstone Unit 3 when 2 out of 3 reference legs lost = level.
At one time OlG was investigating this as it related to the BWR=B9s = but we mutually agreed to cease the effort because the outcome was = likely to be similar to the Rosemount investigation. I was given = assurance by the NRC Staff that this issue was properly closed out
= for both BWR=B9s and PWR=B9s.
If you need any help in identifying the root cause of this problem, = give me a call.
Sincerely, 9706130172 970611 PDR ADOCK 05000327 P