ML20090B525
| ML20090B525 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 05/24/1982 |
| From: | Ippolito T Office of Nuclear Reactor Regulation |
| To: | Lainas G Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML082380335 | List:
|
| References | |
| FOIA-91-106, RTR-NUREG-0909, RTR-NUREG-909 NUDOCS 8206210019 | |
| Download: ML20090B525 (3) | |
Text
- ___ _____ - ___--___--_-
I j
g t 4 GN HEHORANDUM FOR:
G.C. Lainas Assistant Director for Safety Assesscent Division of Licensing FROM:
Thonas A. Ippolito, Chief Operating Reactors Assessrent Branch Division of Licensing
$UBJECT:
GENERIC REC 0mENDATIONS RESULTING FROM STEAM GENERATOR TUBE RUPTURE EVENT We have revieweu NUREG-0909 with respect to developing recorrendations for improvemnts which would be generic to all PWR's. Our review includes consideration of the responses we have received to date to Mr. Denton's May 3,1982 remorandum and our own recent involverent in the Ginna Restart SER. As a result we feel that we can identify sone of the nost prominent lessons applicable to all PWR's.
-We have a high degree of confidence in our understanding of the initiating event for the SGTR also of the subsequent failure nechanisms.
It is clear from theavidence presented to date that a foreign object of significant size is necessary to initiate the failure nochanisms.
It is likely that the object was left in the generator as a result of generator internals modifications performed in 1975. These objects went undetected untti the post-rupture inspections because of a lack of surveillance of the secondary side of the generator. Mechanical damage appears to be cause of failure of the Ginna tubes with corrosion, wastage ano other of the r. ore usual nochanisms having little or no effect on the subject tubes.
As a consequence, we believe that it is apparent that:
(1) inspection requirenents of the secondary side of the steam generators have not been adequately covered in our previous
/
requirenents and neeo improvenentt
/
n \\'
(2) a loose part nonitoring system on the secondary side of the
/
i f,(f steam generator is needed;
,/
/ -l
/
(3) repair procedures should be reevaluated (plugging, by itself
('y /
y
\\
may r:ot prevent continued tube dogradation and in fact continued failure of tubes can go undetected and might result in conse.quential failures).
{ '\\ ',
- p p
/
' s, t
QQy6.+tDU,']Yi',/
~
i
\\
1 l
e y
l 3
l
s t
G.C. Lainas It stems appropriate that wo should require corrective action in the above areas. Specifically, licensees should t>e required tot (1)
Inspect the secondary side of the steam pnerators in a similar mnner to RG&E's program for Gintia, i.e., the use of fiber optics or miniature tv canora to detect deu 'is or tube damage.
The initial inspection would be concurrent with the next scheduled ECT examination of the tuta.s. The frequency of subsequent inspections of the secondary side weuld be based on the results of the initial inspection.
In addition. these visual inspections should be required at any tirie mdifica-tions or repairs are made to the recondary side of the steam generators 1 (2)
Install as soon as practicable loose parts mnitoring system and a loose parts monitoring prograni considering the guidance contained in Regulatory Guido 1.133 to mnitor the secondary side of steam generators; (3) Reevaluate tube plugging rethods to include considerations for unitoring and limiting the effects of continued tube degradation after plugging. The use of limited leakage plus my be a method of mitigating further tube degradation fgr plugged tubes and should be considered.
We have also considered the need for short terTn requiremnts for irnprovements in water chemistry control, mre frequent ECT inspections, a reduction in primary to secondary allowabic leakaga limits, and Steam Generator Tube Rupture emrgency procedures. We believe that increased frequency of ECT inspections and lower leakage limitu should be left for further consideration as a part of our overall effort in developing generic recormendations which will include consideration of the A-3, A-4 and A-5 programs and valve inrpact considerations. However, improvements in water ctemistry control have been under study by utilities and preliminary industry guidelines have been developed and have been adopted by som plants. We recorrmend that our short tenn act%n include reference to Wese guidelines and improvemnts be undertaken by licensees as quickly as practicable.
With respect to plant etergency procedures, we will require chariges that are compatible with the emergency procedurts now under review. We do not believe that short term requirerents are prudent without a careful evaluation of the existing procedures.
p ghud dgned W "tcus_A 1ppelltry rhinf Operating Reabtors Assess /ent Branch omce>
WIDNLMinf suanue >
one>...cc:...See..ne x.t..page.......
nac ronu ais nomi ancu no OFFiClAL RECORD COPY m ime t
4 i
i.
9.C. Lainas cc:
E. Case R. Vo11mr H. Thorpson R. Tedesco T. Novak T. Spels T. Ippolito P. Norian L. Rubenstein N. Su T. Marsh K. Wichman J. Lyons F. Schroeder W. Minners W. Johnston L. Shao DL BCs
~
LESIGNATED ORIGINAL s
N d.l.u
/(, byy 981't i fi ed Dy __ _
E M -
/
(.
r l
l
- A*
o
.m l
D.......RAB
-D ' '.;2%.........D.(. 4* R A B..B..C...
^
o,,,ci p
..R..M..c..l.3.,.,....f..
. s. h....
.KW......h...m..a..n..
Y l
...T...[. p..o........o.....
l l
g)
... 5../.2..<./. 82...... 5. W". '..'. 8 2.....
.. 5./.M..../.82......
ona>
~~
unc rom m oomo4acu cao OFFICIAL RECORD COPY usmw.m r t
l l
1 --
...., _.. _