ML20039E908
| ML20039E908 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 11/10/1981 |
| From: | Sargent C COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML20039E909 | List: |
| References | |
| NUDOCS 8201110607 | |
| Download: ML20039E908 (9) | |
Text
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Commonwealth Edison one First National Plaia, Chicago llanors 7 Address Reply to: Post Office Box 767 ppy;ICIPAL STAFF Chicago llhnois 60690 j'yR
'ly M IS!
I November 10, 1981 f
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p y yt
-h va?' ? T Mr. James G.
Keppler, Director d
E&TI %M Directorate of Inspection and oEP s Pih Enforcement - Region III U.S.
Nuclear Regulatoly Commission p-m f,,,, m, _,, up~
~ ~ " 3 t; 7 N f h 799 Roosevelt Road h
177N.D. _
H "1 Glen Ellyn, IL 60137
~
T 7 ~I P %u*lRCf g5 T' JJt rir
Subject:
LaSalle County Station Unit 1 NRC Open Item No. 50-373/81-28-26 V,
f Reactor Containment Liner De formation,s
'.*s NRC Docket No. 50-373 g,.,
j Dea r Mr. Keppler:
The purpose of this transmittal is to provide a report on the Reactor Containment Liner Deformations as requested by Region III personnel in a meeting at LaSalle County Station on October 8, 1981.
The report substantiates the mechanisms which caused the localized deformations in the containment liner; concludes that plant design criteria was not exceeded; shows the leak tight inte-grity of the liner is not adversely affected by the presence of localized deformations; and proves that voids in the concrete are not present behind the liner.
We request you transmit this report to NRR if necessary to resolve this issue.
Accordingly, one (1) copy of the report and nine (9) copies of the necessary drawings are enclosed.
If there are any questions in this regard, please contact this office.
Very truly yours,
( k, /
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Ip7 C.
E.
Sa rgent 3
Nuclea r Licensing Administrator Enclosures a
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NRC Resident Inspector - LSCS 460DN sid:
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Introduction
)
This report was prepared to respond to Nuclear Regulatory Commission (NRC) concerns about the presence of deformations (i.e., bulges) in the Unit #1 Reactor Containment Drywell Liner, NRC Open Item No. 50-373-81-28-26. The NRC Region III Inspector identified nine areas of localized deformations on the Containment Liner projecting)approximately 1/2" to 3/4" inward towards the Reactor Pressure Vessel (RPV centerline. When the deGrmations were tapped with a hammer a hollow sound was heard. Based on the sound heard during tapping, the NRC was concerned with the following questions:
1.
What caust.d the localized deformations in the liner and did they exceed plant design criteria?
2.
Did the hollow sounds indicate the presence of voids in the concrete which may affect the integrity of the liner and which may ultimately be detrimental to the safety of the plant?
This report substantiates (1) tite mechanisms which caused the localized deformations; (2) that plant design criteria was not exceeded; (3) the leak tight integrity of the line" is not adversely affected by the presence of localized deformations; and (4) that voids in the concrete are not present behind the liner.
Design Criteria Details of liner analysis and acceptance criteria are outlined in FSAR Subsections 3.8.1.4.5 and 3.8.1.5.2 respectively. Strains in the liner due to self-limiting loads such as dead load, post-tensioning, creep, shrinkage, and temperature are limited to the values specified in Article CC-3720 of ASME B&PV Code,Section III, Division 2.
Displacements in the liner anchors are limited to values specified in Article CC-3730 of the ASME Code.
Function of the Liner 1
The primary function of the liner is to provide a leak tight containment boundary limiting any radioactive gas escaping into the environment. Also, the liner serves as a form plate for the containment wall concrete pour. Liner strains are induced by dead loads, post-tensioning, creep and shrinkage of concrete. Additional compressive strains are induced in the liner under thermal loading conditions which may cause separation of liner from concrete and which may cause the liner to buckle. Bond between the liner and concrete is not a design requirement and a separation of liner from concrete is acceptable.
The only design criteria for the liner is the strain limitations as stated in 5 FSAR. Buckling of liner panels is a design condition and it is demonstrated by analysis (FSAR 3.8.1.4.5) that after buckling the liner is capable of providing l
effective leak tightness and remains fully functional.
L-
)
F Reactor Containment Liner Construction The reactor containment liner was constructed as a free standing shell utilizing a big-piece construction concept with the penetration assemblies and embedment plates field welded into the shell after setting of the shell sections. The basic liner membrane is 1/4" stainless steel plates (utilized in the Suppression Pool) and 1/4" carbon steel plates (utilized in the Drywell).
The anchorage to the concrete consists of vertically placed angles welded 15" c-c horizontally. Additionally horizontally placed angles and flat plate are provided to resist wet concrete forces.
The 1/4" plate and anchorage system was field welded into ring sections approximately 30 feet high in the prefabri-cation yard and set by using a large capacity stiffleg derrick. The penetration assemblies were shop welded into thicker (>l/4") plates and along with individual thickened ( >l/4") embedment plates were field welded into cut-outs made in the 1/4" shell plate. Attempts were made to minimize the deformations in the 1/4" plate during insert welding by grouping the individual penetration assemblies and thickened embedment plates into larger thickened plates. Attached Sargent & Lundy Engineers Drawings S-332 and S-333 show the individual penetration assemblies and embedment plates superimposed on the larger plates for the Unit #1 Drywell.
Due to the large number of cut-outs and inserts welded into the 1/4" shell, localized deformations of the 1/4" shell occurred.
These deformations were aggrevated by the late addition of other insert plates which could not be planned into the larger thickened plates.
The deformations were deemed acceptable within contract construction tolerances and required no remedial work. A survey conducted after liner erection found all deformations to be 1" or less.
Reactor Containment Concrete Construction The reactor containment concrete placing operations were completed as 1iner sections were completed.
The liner served as the inside concrete formwork. Outside concrete forms were tied to the liner by rods welded to horizontally welded angles and flat plate.
External concrete form bracing was not used during placing o pera tio ns.
Each pour was approximately 10 feet high.
Concrete placing was limited to 1 to 2 feet per hour to minimize wet concrete lateral pressure on the formwork and liner.
The concrete was placed according to specifications and approved procedures utilizing trained personnel.
Training classes in the usage of concrete vibrators were held and documented in order to preclude inappropriate concrete placing practices.
Containment Liner Integrity and Sargent & Lundy Engineers drawings S-332 and S-333 record and map the location and approximate sizing of deformations found during an inspection of the containment liner surface. No deformations spanned across the liner vertical anchorage system. Some deformations did not exhibit hollow sounds.
Additionally, other areas of non-deformed liner exhibited hollow sounds indicating liner separation from concrete.
e
(,
_C_ontainment Liner Integrity ( Cont'd)
Separation of liner from concrete surface can_ occur due >> compressive strains induced by post-tensioning, creep, and shrinkage of concrete. Local deformations of containment liners is not an uncommon phenomenon and is in fact anticipated.
Deformations may occur during construction, due to welding of stiffeners and embedment plates to the liner. While pouring, the concrete will fill the space up to the liner whether it is flat or deformed. Once a deforma-tion is present, liner separation from concrete is more likely to occur at the deformations than on the flat surface, since at the deformation the restraint stresses will initiate the movement of the liner in the direction of the deformation causing separation.from concrete. The liner was surveyed after erection and all local deforma ; ions were found to be within construction tolerance of1".
The localized deformations do not exceed plant design criteria.
Reactor Containment Concrete Integrity The hollow sound was not due to any void or concrete honeycomb and is established by the following:
a.
Due care was exercised while pouring and consolidating concrete per Sargent & Lundy specifications and approved procedures.
In areas of heavy reinforcing steel congestion pre-pour plans were made and implemented to preclude concrete consolidation problems.
b.
A survey of the outside face (50% of the concrete surface area) of the containment wall showed that the concrete quality was excellent and no voids were detected. Therefore, it could be deduced that the concrete at the liner would also be of the same quality. Additionally, the inside Drywell cone form surface had a horizontal component which would contribute towards easier concrete consolidation over two vertical surfaces such as the suppression pool.
During recent suppression pool modifications, installation of anchor plates required the removal of about 15%
of the liner and the concrete behind the removed liner was found to be of excellent quality and void free.
Two-hundred seventy-two cores made into the concretet for these plate anchor bolts showed no concrete voids. Thus a total of 65% of the concrete surface inspected was without voids. Based on a statistical approach it could be judged with confidence that the remaining 35% of the concrete surface is also void free, c.
The containment passed both SIT and ILRT tests.
If there was any void behind the defonnations other than a mere separation from the concrete the liner would have yielded under the 52 psig test pressure and molded into the void when the SIT was performed. No evidence of such distress or even a hairline crack on the liner protective coating was detected. Also it was observed that these deformations do not extend beyond the liner anchors. This confirms that the anchorage is sound and is not subject to any pull out and that the liner anchorage system remains functional.
I i
I O
y
- Reactor Containment Concrete Integrity (Co nt'd) d.
Similar type liner deformations and hollow soundings found at Zion Station and reported to the Atomic Energy Commission ( AEC) in 1973 did not have voids in the concrete when exploratory drilling of the liner was conducted. The results of this investigation and subsequent deformation monitoring were sent to' the AEC. The deformation monitoring was later ceased when they exhibited no movement over time.
Recent tests and investigations at Marble Hill Station indicated no concrete voids behind the liner even though hollow sounds were present.
e.
All of the liner inward deformations were limited to the horizonta?
dimension or less between liner anchors.
In many cases the vertical deformation dimension exceeded the 1 to 2 feet concrete pouring rate.
If the liner deformations and hollow sounds were indicative of concrete voids it would seem plausible that the horizontal void dimensions would vary greatly and not be limited to between liner anchorages, as found during the liner inspection.
Additionally, since the concrete was placed in 1 to 2 feet lifts, it seems implausible that a long vertical concrete void would result, especially given the flowability of concrete.
Intuitively,
it is difficult to show how concrete voids resembling the liner deformations could form.
f.
The presence of hollow sounds when the liner is tapped is not an acceptable method for concluding voids exist in the concrete.
As a check other places throughout the plant where metal plate forms the concrete surface were randomly tapped.
Hollow sounds were exhibited even where the metal plate forms the underside of a 4" thick concrete slab.
It was concluded a slight separation of metal from concrete will cause the hollow sound.
Nuclear Regulatory Commission Inspection Activities Certain Unit #1 & #2 Reactor Containment exterior concrete placing activities were inspected and witnessed by various NRC Region III I&E inspectors during their audit activities on the LaSalle County project site. Other various non-Reactor Containment concrete placing activities were also witnessed by these same or additional inspectors.
The activities inspected include (a) pre-pour activities; (b) batch plant activities; (c) concrete placing personnel training activities; (d) concrete placing operations; (e) concrete testing activities; (f) procedure implementations; and (g) documentation of activities and test results. The inspection results indicated concrete placing activities met or exceeded specifi-cation and procedure requirements.
1 i
l l
C J
g Defonmation Surveillance Program After evaluating the liner deformation inspection and mapping results, it has been concluded no further monitoring of the liner deformations is necessary. The mechanisms which created the deformations (i.e., initial welding distortion and prestress forces) are no longer contributing to the deformation of the liner. The survey indicated those deformations with the greatest inward deflection occurred in places where welding distortion would be expected.
Expected deformations even at accident temperature would not impair the function of the containment liner.
Conclusion It is concluded that local. bulges were caused during construction and the measured inward projections are within the tolerance of 1" permitted for local areas. A statistical approach based on the observed good quality concrete surface ensures void free concrete throughout the containment wall. Hollow sounds on some of the flat portions of liner and on the bulges results from separation of liner from concrete surface which is permitted. The liner had withstood the effects of 52 psig test pressure during SIT without showing any distress. The liner has also passed the ILRT demonstrating that its leak tight integrity is not adversely affected and that the liner remains functional.
L-Prepared by:
D. L. Shamblin
c_
Att*chment No. 1 UIIIT #1 REACTOR C0!ITAIMMIT LIIIER PLATE DEF0HATIO!IS ftAP SCHEDULE APPROXIMATE B1mTED(
HO.
APPROXI? TATE LOCnTIOI!
DEFOR?!ATIOII SIZE _
STIFFENING REMARKf' AZIMUTH ELEVATION 1.
330" 812' 3/8" to 1/2" 10" dia.
Yes No hollote sounds 2.
335 810' 3/8" 48" vt 13" H.
Ves 3,
20*
810' 3l8" 24" ex 13"H.
Yes Cuboard 10" dia.
def2cetion 4.
285*
810' 1/4" 20" vx 13" H.
Ves Botit hottoto &
solid sounds 5.
265*
810' 3/8" 48" vx 13" H.
Yes 6.
230" 810' 3/8" 20" vx 13" H.
Yes 7.
90" 807*
1/2" 10" dia.
Yes 8.
35" 813' 3/8" 10" vx 13" H.
Ves Botli holloto &
0" 0 * ""
- 9.
330" 802' 1/4" 60" vx 13" U.
Ves 10.
337" 801' 3/8" 20" vx 13" H.
Yes 11 355*
801' 1/2" to 3/4" 25" vx 13" H.
Ves 12.
55" 801' 1/2" to 3/4" 25" vx 13" U.
Yes 13.
75 805' 1/4" 60" vx 13" H.
Vcs 14.
180*
805' 1/2" 60" ex 13" H.
Ves 20" vx 13" H.
48" vx 13" H.
15.
220" 802' 1/2" 15" ux 10" H.
Yes No hollote sounds 16.
240" 801' 1/2" 10" ux 10" U.
Yes 17.
235" 788' 1/2" 10"Q Yes 10"1 Yes 18.
275' 785' 1/2" 40" vx 13" H.
Ves 19.
290" 783' 1/2" 25" vx 13" H.
Yes 20.
295*
783' 1/4" 20" vx 13" H.
Ves 21.
305" 782' 1/4" 10"(f Ves 22, 343*
785' 1/4" 72" ux 13" H.
Yes 23, 340" 188' 3/8" 8"$
Ves Cubea'id deftcetion 24.
345" 790' 1/2" 10" vx 13" H.
Yes Ho hollote sounds j
10" ex 13" H.
Yes l
25.
20*
783' 1/2" 36" vx 13" H.
Yes 26.
20" 788' 1/4" 10"(l Yes 27.
25" 789' 1/4" 15" vx 13" H.
Yes 28.
68" 783' I/4" 10" vx 8" H.
Yes No hollote scunds 29, 70" 783' 1/2" 15" ex 13" H.
Ves 30, 930 783" 1/2" 48" ex 13" H.
Ves J
r
-?-
+
!iO.
' APPROXIMATE LOCATION DEFOPRATION APPROXI!! ATE BEDTEEN (
SIZE' STIFFENING REMARKS AZI?"UTH ELEVATION 31.
98*
183' 1/2" 48" vx 13" H.
Yes 32, 107" 783' 1/2" 30" vt 13" U.
, Yes No hollow sounds-l 33.
133 787' 3/8" 15" vx 13" H.
Yes 34.
180*
185*
-1/4" 10" b Yes 1/4" 10" (
Yes 35.
123*
780' 1/4" 30" vx 13" U.
Yes 36.
108" 779' 1/2" 8" 0 Yes 37.
185*
180' 1/4"
.30" ux 13" H.
Yes
-38.
190*
180' 1/4" 30" ux 13" H.
Yes
^ 39.
255*
781' 1/4" 8"k Yes.
40.
200*'
738' 1/4" 48" vx 13" H.
'Yes 41.
327*
739' 3/8" 84" yx 13""Ili.
Yes 42.
345*
745' 5/8" 12" vx 13" H..
.Yes l
43.
5*
'745' 1/2" 12" vx 13" H.
Yes l
44.
23 755
5/8" 30" vx 13" H.
Yes 145.
35*
172*
1/2" 15" vt 15" H.
Yes 46, 58*
751' 1/2" 15" vx 13" H.
Yes 47, 130*
755' 1/4" 30" vx 13" H.
Yes 48.
100*
755' 1/4" 15" vt 13" U.
Yes 49.
93*
760' 3/8" 20"'vx 13" H.
Yes
\\
50 46 757' 1/2" 15" vx 13" H.
Yes 51.
55 771' 1/2" 10"k Yes
\\
52.
55 167' 3/8" 20" ux 13" H.
Yes I
53.
120" 773' 3/4" 15" vx 13" H.
Yes 54.
120*
776' 3/4" 15" vx 13" H.
Yes 55.
120*
'770' 1/2" 30" vx 13" U.
Yes 56.
123*
170' 1/2" 20" vt 13" H.'
Yes 57 126 775' 3/4" 20" vx 13" H.
Yes 58.
140*
146' 1/4" 48" vx 13" H.
Yes 59.
145*
145' 1/4" 10" ex 13" H.
Yes 60.
170*
746' 3/8" 36" vx 13" H.
Yes bl.
195*
156' 1/2" 15" vx 13" H.
Yes l
62.
190**
760*
1/2" 6" vx 13" H, Yes 63.
185*
760' 3/4" 18" vt 13" H.
Yes 64, 165*
761*
1/2" 30" vx 1.3" H.
Yes 65.
200*
767' 1/2" 30" vx 13" H.
Yes i
L-
l l*,
APPROXIMATE BETWEEN <
l SIZE STIFFENING RE?4 ARKS f
TIO.
APPROXI!1 ATE LOCATIO!I DEFORMATIO!;
f AZI!!UTH ELEVATIO!!
l 66.
215*
175' 1/2" 40" vx 13" H, yg,$
outw rd deflection 67, 218 775' 1/2" 10" vt 12" ff, yc3 no holica sounds 0
68.
250 763*
1jgn gon yz ygn y, ye,$
0 j
69.
150 756' 1/2" 15" vx 13" y, yes 0
dls-11.5.81 1
1 i