ML20149H522
| ML20149H522 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 04/25/1997 |
| From: | Dwyer S AFFILIATION NOT ASSIGNED |
| To: | Shirley Ann Jackson, The Chairman NRC COMMISSION (OCM) |
| References | |
| 2.206, DD-98-06, DD-98-6, NUDOCS 9707250020 | |
| Download: ML20149H522 (1) | |
Text
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From:
stephen dwyer <smd@wdc. net >
To:
WND1.WNP2(Chairman)
Date:
4/25/971:31pm
Subject:
SONGS SG SUPPORTS & SEISMIC RISK Dr. Shirley Jackson, Chairman Re: San Onofre SG Supports Nuclear Regulatory Commission Washington, D.C.
Honorable Chairman, I recently recieved (through the grapevine, not SCE) the 4-17-97 report from San Onofre.
Subject:
DEGRADATION OF STEAM GENERATOR (SG) INTERNAL TUBE SUPPORTS.
j (AKA EGG CRATES)
I am especially concemed about th:s new additional weakness at San Onofre.
I believe that the plant will not be able to withstand completely a major seismic event, and am adding this new concem to my emergency petition.
If the egg crates are somewhat corroded to seriously corroded, *his could seriously compromise the seismic resistance of this vital component.
If the tubes can be shaken even slightly they could come loose and a large number could rupture. Since the corrosion is widespread and cn.%th hot and cold legs, it appears to be serious. This level of corrosion may also be affecting the tubes themselves. Whatever the severity of degradation, any corrosion would seriously weaken the supports and dramatically decrease their seismic resistance to below the DBE.
Considering the wide range of problems in other SGs, serious problems with the SGs at SONGS can be expected. Virtually any problem can make the SGs vunerable to seismic events. Apparently after this degradation was found in i
Unit 3, a " limited inspection" of Unit 2 was done. But, it revealed nothing.
Its hard to imagine that this twin SG was not even affected at all.
If it wasn't degraded, then the reasons should be investigated further to find out why. This would be very valuable information to use to prevent degradtion elsewhere.
But, I have serious doubts that this is the case. A very thorough investigation should be done to find any corrosion similar to Unit 3. There is a very high probability that there is corrosion somewhere.
A further genera l seismic evaluation upgrade should be done for these SGs, and a retrofitting upgrade of the SG supports could be done at this time.
This retrofitting could be with heavier guage steel or stainless steel on both units.
Thank you for looking into this matter.
Sincerely, i
Stephen Dwyer smd@wdc. net CC:
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