ML20053D846
| ML20053D846 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 05/26/1982 |
| From: | Jackie Cook CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, 117504, TAC-48349, NUDOCS 8206070379 | |
| Download: ML20053D846 (5) | |
Text
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O Consumers Power James W Cook Company m, ~,u,n,- now,a ne.,,,,
and Construction General Offices; 1945 West Parnall Road, Jackson, MI 49201 e (517) 78&O453 82-06 #1 May 26, 1982 Mr J G Keppler, Regional Administrator US Iluelear Regulatory Commission Region III 799 Roosevelt Road Glen Ellyn. IL 60137 MIDLAI!D PROJECT -
DOCKET Iios 50-329 AliD 50-330 DESIGII 0F IIITERITAL AUXILIARY FEEDWATER llEADER III S&W STEAM GEIiERATOR FILE:
0.h.9.62 SERIAL:
1750h This letter provides an interin 50 55(e) report concerning the B&W steam generator auxiliary feedwater header. This item was declared "potentially reportable" in a telephone conversation with R C Knop of your staff on May 26, 1982. The decision to make this item ' potentially reportable" was based on the damage recently experienced by other utilities (Davis-Besse, Rancho Seco and Oconee #3), which have steam generatt.- internal auxiliary feedwater header of a similar design to Midland. Consumers Power C mpany is presently working closely with both B&W and other utilities, having similar designed steam generators, to address the problem and develcp a long-term solution.
The following provides a description of the internal header which exists on the Midland Project.
- shows a longitudinal view of the Once Through Steam Generator (OfSG) and indicates the position of the internal AFW header. Attachment 2 shows a longitudinal view of the internal AFW header at the single AFW nozzle t
position.
As indicated in these attachments, the internal /M header is mounted on top of the upper shroud between the 15th Tube Support Plate and the Upper Tube Sheet. The interr.al AFW r: - header is constructed of 3/8 inch plate metal with a 13 inch by 5 inch rectangular cross-section. There is a single AFW nostle injecting into the header to fill the header with water.
The water ficws into the steam generator tube bundle through sixty 1 inch diameter holes located near the tcp of the header and equally spaced around it.
The P.eader rests on the top of the shroud and is attached to it by eight pairs of brackets which are equally spaced around the header.
Each bracket (or Tab) measures 1 inches vide x 2 3/8 inches long x 3/8 inch l
thick and is velded to the header.
A 2 11/16 inches long x 3/h inch diameter l
8206070379 020526 PDR ADOCK 05000 yg S
rE 2M4
e Serial 17501 82-06 H1 2
dowel pin is welded to the inner bracket and slip-fit through the shroud and the outer bracket to hold the header in place while allowing for differential thermal movement between the header and the shroud.
The damage that has been experienced at the operating plants consist of deformations of the header, bent brackets, missing devel pins, and apparent contact between the header components and the tubes. We understand the operating plants are providing more details to the NBC on the damage experienced at their Units.
The cause of the damage is being investigated.
However, the apparent cause of the deformation of the internal auxiliary feedvater header is its inability to withstand the large thermal and pressure forces genevated when cold auxiliary feedwater is injected into the header. During normal operation, the header would be filled with super-heated steam as the header sits in the upper super heat region of the OTSG.
When cold auxiliary feedwater (
80 F) is injected into the rectangular header, very large local pressure differencea can occur with large steam-water contact areas which cannot be locally compensated for quickly enough through the 1 inch diameter flow holes. Except for the extra strength veld areas, the 3/8 inch plate walls are not reinforced end are apparently inadequate for the loads generated under these condi+. ions.
In addition to the possibly large pressure drop areas, the header itsel ' experiences very high thermal differences when the cold AFW enters the header and begins to fill from the bottom up and flows around the header from the single nozzle. While the exact failure process is not totally known, the above forces are believed to be the dominant factors.
The most probable modification that will be implemented at Midland is the installation of an external ring header similar to those presently being installed at the above referenced operating plants.
Another option related to AFK system operation as a means of preventing damage to the existing intact Midland design is also being investigated.
We anticipate that further information regarding corrective action will be available by July. Required plant modifications are expected to be complete by Cetober 1982.
Another report, either interim or final, will be sent on or before July 30,
- 1982,
. m d-DTP/lr j
Attachments (2)
/
CC:
Document Centrol Desk, NRC Wochington, DC RJCook, "RC Resident Inspector, Midland Site
9 Serial 17504 82-06 #1 3
s CC: CBechhoefer, ASLB Panel RSDecker, ASLB Panel FPCowan, ASLB Panel JHarbour, ASLB Paael AS&L Appeal Panel MMCherry, Esq MSinclair BStamiric CRStep:' ens, USNRC WDPator, Esq, USNRC FJKell y,' Attorney General SHFreenan, Asst Attorney General WHMarshall GJMerritt, Esq, THK&J Great Lakes QA Managers
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Serial 17504 177FA ONCE-THROUGH 82-06 #1 STEAM GENERATOR (OTSG)
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