ML20050F933
| ML20050F933 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 04/01/1982 |
| From: | Lentine F, Letine F COMMONWEALTH EDISON CO. |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| 3771N, NUDOCS 8204140041 | |
| Download: ML20050F933 (5) | |
Text
Commonwrith Edison 33 One First National Plaza. Chicago Illinois a
5 Address Reply to: Post Office Box 767 3
Chicago. Illinois 60690 N
0
'W forrect e$
N$
~
e RECEWED Cory-A,,gh[gh
- 9. g 4 m
5 gpg8 190N
~2 apru 1, 1982
~
T M'
!w eigyLT" 3 v( V;y')
'N'( T 9-9 q
is w
'%g / g\\q dQ
\\
O \\U
\\,
m c
11 G.
Eisenhut, Director
\\T Q
t on of Licensing 3 Ypq
\\
\\
\\
U.S.
Nuclea r Regulatory Commission j
Q (Q'N Washington, DC 20555 O q
Subject:
Zion Station Unit 1
\\
'D M
-) (_)
M
\\$
J Steam Generator GD Inspection and Repair
}
k s
NRC Docket No. SD-295 r!
-f G
%g h' 9g
'M".
$[ q References (a):
March 10, 1982, letter from D.
Eisenhut to L. De l Ge o rg e.
M aN (b):
Ma rch 17, 1982, letter from N
F.
Lentine to D.
Eisenhut.
Dear Mr. Eisenhut:
This letter is to document the recovery program planned for the damaged tube ends in the Zion ID steam generator, as presented to members o f your s ta f f on March 25, 1982.
Following receipt o f the NRC's verbal approval at the conclusion of that presentation, we have continued our preparations for the recovery program.
Our current schedule is shown in Table 1.
Commonwealth Edison hereby requests confirmation of the NRC's approval prior to the start o f the actual repair work, presently scheduled for April 8, 1982.
The recovery program is in two phases.
The first phase addresses the following work:
1.
Repair o f damaged tube ends which could result in future tube fragments.
2.
Restoration of tube ends of Row 1 and other tubes requiring plugs to accept tube plugs and the eddy current probe.
The first phase of the program, will be accomplished using manual techniques.
The second phase will consist o f restoring the remaining damaged tube ends using an automated system controlled from outside the steam generator lower plenum.
This system will greatly reduce the radiation exposure o f the personnel involved in the program.
f 8204140041 820401 PDR ADOCK 05000295 gD P
A t
D.
G. disenhut April 1, 1982 Approximately 200 tubes in the peripheral area will not be restored at this time.
They will be -restored at a later date to allow future eddy current examination to be performed completely from the hot leg side.
These 200 tubes are outside the range o f the automated system and will. require manual work with the associated additional radiation exposure.
The repair / restoration process will consist of the following steps:
Repair process:
1.
Machine the tube end to a minimum of (9 tubes) 0.070 inches beyond the tube sheet.
This assures that any potential loose pieces will be removed and the tube-to-tube sheet weld will not be removed.
2.
Expand the tube end to the required diameter using a hard roller.
Restoration process:
1.
Light damaged tube ends - hard (hemaining tubes) roll with final size hard roller.
2.
Medium damaged tube ends - hard roll with several hard rolls of increasing size.
3.
Heavily damaged tube ends - use slide hammer to enlarge opening then hard roll with hard rollers of increasing size.
The initial construction o f the steam generator made use o f
(
an 80 inch-pound ha rdroll to a depth o f 2 1/4" to 21/2" in addition l
to the 1/8" fillet weld at the tube-to-tubesheet juction.
No credit l
was taken for this initial hardroll in the stress analysis report.
l
' All stresses were. considered to be taken by the 1/8" fillet weld.
Tube end damage and weld integrity were evaluated visually by the use o f direct visual observation, video tapes, and indexed, magnified still photographs.
All of these methods indicated no damage to the cladding on the tubesheet, plenum, or divider plate.
E tio tube-to-tubesheet weld damage was observed.
Additionally, the l
observed degree o f tube end deformation would have no e f fect on the flow characteristics or heat transfer capability of the steam generator.
Incependent verification of weld integrity was obtained i
through laboratory testing designed to simulate the observed damage, j
and additional stress calculations to determine changes in the total i
fatigue usage factor.
The laboratory tests simulated both the l
damage observed and the repairs proposed.
Photographic, x-ray, and metalloroical sectioning inspections all revealed no cracking in the
{
lw
D.
G.
Eisenhut April 1, 1982 weld area and no tube wall thinning in excess of the manufacturer's allowable tolerances.
The stress calculations revealed an increase in the total fatigue usage f actor from 0.063 to 0.144.
This is well within the ASME Section III code allowable total fatigue usage f actor o f 1.0.
During the recovery program, an additional 120 inch-pound hardroll to a depth o f 1 1/2" will be perfomed on tubes with damaged ends.
This hardroll is a code acceptable stress carrier, and Westinghouse reseach (WCAP 9960) has indicated that it is capable of taking all o f the required stresses without any structural weld being present.
However, as in the original stress analysis report, no credit is being taken for this hardroll.
All stresses a re considered to be taken by the fillet weld.
Af ter completion of the recovery program, another complete set of high resolution photographs will be taken for use as a final inspection device.
The manually repaired / restored tube ends will be dimensionally checked by a tube gage, and the tube ends restored by the automated process will be dimensionally checked by a plug gage check on the first and last tube ends restored by a specific hard roller.
Commonwealth Edison is currently evaluating the feasibility of performing additional checks to further verify the integrity of the tube-to-tubesheet weld.
Upon completion o f our evaluation, we will discuss this matter further with the NRC.
In our March 25 presentation, we also discussed the 28 bolts from the aluminum cover plate still remaining in the primary sytem.
Our program to search for these bolts is as f ollows:
1.
Inspect "D" hot leg piping, incuding the isolation valve.
This has been completed.
One bolt was found and recovered between the lower plenum and the isolation valve.
No bolts were found in the area of the isolation valve seat.
I 2.
Inspect the reactor upper internals a f ter they l
are placed on the inspection stand.
A T.V. camera will be used for this work, concentrating on the area closest to the "B" and "D" steam generator l
hot leg nozzles.
3.
Inspect the top of the fuel.
Due to dimensional considerations, the bolts will not fall into the fuel.
Therefore, any that have fallen through l
the upper internals should be found on the top of I
the fuel assemblies.
4.
Inspect the tubes of the 10 steam generator oy performing a 100% eddy current examination.
l
- .r
<k v'!
G.
Eisenhut
-4 April 1, 1982
. f'-
3 Should any loose parts remain unaccounted for at the mpletion of this program, a safety evaluation will be made to N
~
maining in the system.
- -,\\,
?
ofirm the acceptability of continued operation with those parts The location of the aluminum in the primary system,
['sulting from the dissolution o f the manway cove r, is being pursued t
the following program:
.}
y,
1.
Samples have been taken from the following locations:
CVCS Hold-up Tanks, Reactor Coolant System, and the outlet of the Reactor Coolant filter.
Essentially no
[
aluminum was found.
2.
Samples will be taken from a CVCS letdown demineralizer that was in service during the last part of the fuel
.~ ~
cycle.
3.
Crud samples will be taken from several fuel assemb-lies from each region of the core.
Following receip t o f the results o f the sample program, an evaluation o f the ef fect o f any contaminants on fuel performance
.- - ~'
will oe made.
Additional information on the investigation and recovery
' ;7 ogram will be made available to the NRC staf f as it becomes avail-
~~
le.
Additional conference calls, meetings, and written submittals l1 11 be scheduled as appropriate.
l
.y.
Please address questions regarding these matters to this u
.[' -
fice.
~
Ve ry truly yours,
,s..
f8 F.
G.
Lentine Nuclea r Licensing Administrator
' [. ' '.. '
x E.
~
71N l...
~
' c,
'4 x
..1
- n.,,.,
j.J~.
s
... ~
f
- *.- M
!!!I o
3 3
92 8
7 2
72 62 7
5 2
4 2
3 2
22 1
2 0
E 2
LU 9
D 1
EH 8
C 1
S l
7 Y
i 1
R r
E p 6 V
A 1
N o
O c
5 1
I E
1 T
R E
A 4
L T
R 1
B S
O A
T 3
T N
A 1
O R
I E
2 Z
N 1
EG 11 M
A 0
E 1
TS 9
8 D
7
?
6 5
4
?
3 2
1 ne s
i y
hWC e
t u
Q n
E s
a e
M e
h t
i l
t
.H s
l e
T l
e e
l a
T u
o p
g t
n t
m u
s C
e a
u o
l n
E H
M A
C P
I 1
2 3
4 5
6 7
l f
1lll