ML19318C588
| ML19318C588 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, Zion File:ZionSolutions icon.png |
| Issue date: | 06/04/1980 |
| From: | Peoples D COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEB-80-05, IEB-80-5, NUDOCS 8007020050 | |
| Download: ML19318C588 (3) | |
Text
- I
' D. Commonwealth Edison f
/ one First N:tional Plaza, Chicago, Illinois 47 f Addtss R: ply t;: Post Offics Box 767 4 gg Chicago, Illinois 60690 June 4, 1980 Mr. James G. Keppler, Director Directorate of Inspection and Enforcement - Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137
Subject:
Zion Station Units 1 and 2 Byron Station Units 1 and 2 Braidwood Station Units 1 and 2 Response to IE Bulletin No. 80-05 NRC Docket Nos. 50-295, 50-304, 50-454, 50-455, 50-456, and 50-457 Reference (a):
March 10, 1980, letter from J.
G. Keppler to C. Reed transmitting IE Bulletin No. 80-05.
Dear Mr. Keppler:
Reference (a) transmitted IE Bulletin No. 80-05, Vacuum Condition Resulting In Damage to Chemical Volume Control System (CVCS) Holdup Tanks (sometimes called " Clean Waste Receiver Tanks").
This Bulletin required action to be taken by Commonwealth Edison Company with regard to its Zion, Byron and Braidwood Stations.
Attachment A to this letter contains Commonwealth Edison's response to this Bulletin for these stations.
Please address any questions that you might have concerni.ng this matter to this of fice.
Very truly yours,
- i. D. L. Peop1 >s Director of Nuclear Licensing Attachment cc:
Director NRC Office of Inspection and Enforcement JoM2 01980 4318A 8 00702 00M g
e i
NRC Docket Nos. 50-295/304 50-454/455 50-456/457 t
ATTACHMENT A 1
R,esponse to IE Bulletin No. 80-05 Commonwealth Edison Company's response to IE Bulletin No. 80-05 for Zion, Byron and Braidwood Stations follows.
Zion Station The three CVCS hold up tanks are the only tanks that can be valved to contain primary system water.
A positive pressure is maintained on the tanks by the waste gas system via a vent header.
The pressure in the vent header is controlled by the waste gas compressors' suctior, pressure control system.
Initially, the tanks are purged and filled with nitrogen.
The reactor coolant entering the holdup tanks displaces the nitrogen and releases hydrogen and fission gases that mix with the nitrogen.
These gases are pumped from the tanks to the waste gas decay tanks by the waste gas' compressors.
Normally the cover gas is recycled from the gas decay-tanks, but during periods of rapid liquid removal the cover gas is supplemented with nitrogen from the nitrogen supply manifold in the waste gas disposal system.
Partial vacuums have been created three times in the holdup tanks.
The first event (construction deviation report #124) did not result in damage to the tank, however, the last two events (reportable occurrences #50-295/75-118 and #50-304/75-29) did result in tank damage.
After the second tank was damaged the tallowing measures were taken to preclude similar events.
1.
Increase of the waste gas vent header pressure from 2.0 psig to 4.0 psig..
Increasing the pressure provides a greater low end safety margin and allows valve settings to i
be more accurately maintained.
2.
.The addition of an auto-trip of the waste gas compressors on-low vent header pressure.
This prevents the waste gas compressors from drawing the vent header pressure below 2.5 psig, in the event that the compressor recycle valve fails to open properly at 3.0 psig.
4
<.. e
, '3.
The installation of additional alarms and pressure gauges on the radwaste panel, i.e.
- Vent header low pressure alarm
. Waste gas trouble alarm
- Vent header pressure gauge 4.
Relocation of the nitrogen supply valve closer to the holdup tanks.
This enables the valve to more accurately sense the actual pressure in the tanks.
5.
Upgrading of operating procedures.
The three manual gas isolation valves to the holdup tanks are locked open.
Since these measures were taken, there have been no 3dditional partial vacuum events on these tanks at Zion Station.
Byron /Braidwood Stations The CVCS volume control tanks and the Baron Recycle System (BRS) holdup tanks are the only tanks that receive letdown flow.
These tanks operate with a nitrogen cover gas supplied via a header.
High and low pressures in the header are annunciated locally, and followed up by an alarm on the main control board that indicates a problem on the local panel.
Pressure switch alarms are used to indicate a failure of both the nitrogen supply package and the bulk storage supply.
During periods of rapid removal of liquid from the tanks, cover gas is supplied via a make up path.
The control valve associated with this make up path it adequately sized to admit the, cover gas at a f ast enough rate to keep up with the maximum rate of
. liquid removal from the tank.
In addition to cover gas protection, other design p ovisions have been included to prevent vacuum d- ;ge.
They are:
1.
Specification of design miessure parameters consistent with tank operating conditions; and 2.
An external pressure design of 15 psig.
These design and protection features, in conjunction with proper operating procedures, ensure adequate protection against vacuum damage occuring to these tanks.