ML20235B138
| ML20235B138 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Cooper |
| Issue date: | 12/17/1975 |
| From: | Maccary R Office of Nuclear Reactor Regulation |
| To: | Goller K Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20234C970 | List:
|
| References | |
| FOIA-87-40 NUDOCS 8707080646 | |
| Download: ML20235B138 (10) | |
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gg DEC i 7 G7'S Distribution:
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SEB-Rdg h
K. R. Goller, Assistant Director d
for Operating Reactors g
Division of Reactor Licensing MARK I'CONTdINENT EVALUATION - FIRST ROUND REVIEW g
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DOCUMENTS REVIEWED:
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1.
Mark I Containment' Evaluation Short Tem Program - Final. Report,.
m Volumes I-V, September,1975.
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2.
Mark I Containment Evaluation Short Tem Program - Final Report, y
Addendum to Volume IV, November,1975.
N p;;
3.
Mark I Containment Evaluation Long Tem Program for Cooper W
Nuclear Station, September 29, 1975.
WN Technical Assistance Requesti tio.: TAR 1989 9
Responsible Branch: Operating Reactors Branch # 3 (ORB-3) h"Ti contact: Walter A. Paulson (Ext. 27872)
Technical Review Branches: Containment Systems Branch M
Structural Engineering-Branch 1
Mechanical Engineering Branch h
Target Conpletion Date: December 16, 1975-A Review By: Structural Engineering Branch d
Review Status: First Round Review Complete ed The Structural Engineering Branch (SEB) has conducted a review of the Mark I Containment Evaluation Report and we find that additional
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information is required before we can complete our review. The
.9 additional information requested, which concerns structural aspects.
[i is contained in the enclosure.
.c Qu6stion Al refers to SEB questions previously transmitted to you
-j on August 27, 1975 and subseqantly transmitted to each applicant.
e.
hh Questions regarding Addendum 1 to Volume IV hcVe not been previously 6
discussed with the applicants. Iefomation regarding the adequacy M
. of the torus and its supports has not been provided to date, for NRC 8.2 staff riview.
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The specific long tem program reviewed was that of Nebraska Public Power District regarding Cooper Nuclear Station. We assume that
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@S this program'is identica,l to that of the other utilities.. If not, yj:
provide copies of their long term prograns to SEB.
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ip R. R. Maccary, Assistant Director
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for Engineering F,j Division of-Technical Review.
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Enclosure:
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&[ji ll MARK I-CONTAINMENT EVALUATION j
SHORT TERM PROG 8AtL,. FINAL REPORT 4
LONG TEfutPROGRAM-ACTIVITY SCHEDULE 6.f',
STRUCTURAL-ENGINEERING BRANCH-W REQUEST FOR INFORMATION d
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.A.
GENERAL COMMENT
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1.
Several generic. structural engineering questions which were asked
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previously regarding the " Mark I containment Status Report" (N;I dated July 31, 1975 remain unanswered in this short term final I
evaluation report.
Possibly, some of these concerns.could be h
addressed in the long term program.
If so, justification should
[.
be provided which would support the conclusion that the Mark I safety margins would not be significantly reduced by delaying g,
consideration of such -items.
These unanswered questions are de-y tailed in the following paragraphs of the above referenced struc-tu
.tural evaluation:
J; M
item 7., torus supports; item 8., acceptable strain limits; w
?;3 item 10., the effect upon structures when combining. insignificant" k
loads with significant locds; item 11., the capability of vent y
$.,j headers to resist fallback loads; and, item 15.. vent pipe bellows i
d-assembly.
2.
Throughout this report the yield strength of various members has
]q been exceeded. Yet, no justification for such exceedance has
~
been provided. Provide the bases for concluding that exceeding yield strength is acceptable. Discuss " acceptable strain limits",
@y and provide expected strains and resulting deformations for all ej members that are expected to yield. Discuss the potential for g
loss of function and/or leakage in light of possible stress Q
reversals, cracking and/or buckling and the margin of safety Fa against loss of function.
M M
3.
In several instances, laboratory tests of critical elements have h
been conducted. These tests were performed in controlled condi-fj tions, with loading rates and loading cycles not nece 3arily representative of potential loadings, on a specimen which was
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fabricated with new materials and under controlled conditions, s$l Provide the bases for determining.the applicability of such
.Q 6
tests and the degree of confidence in ' predicting the performance fh of field constructed members.
@j-g 4.
According to this report, several components, structural elements k
. or connections would. fail 'if subjected to the "most probable" fd LOCA induced pool swell loads. No short term repairs have been hj proposed to prevent or mitigate such failures. Describe your 4
conce.ptual plans for short term repairs, if it is datarmined p:
l;j that such repairs are necessary.
k 5.
Describe your plan, if any, for in-service surveillance prior g[
ll,:f to long term repairs of critical structural elements determined pl-to be near yield due. to pool swell loads.
p B.
00!HENTS ON VOLUME I eg 1.
Since the S/R valve discharge loads, alone and in conjunction with pg the LOCA or less severe. accidents, will be addressed in the long term program, provide the structural basis for the conclusion Q
arrived _ at in item (f) of page 1-3 of Volume I of the report, p.
inspite of the statement in the last paragraph of page 3-1 that d.,3 such loads have substantial effects.
2.
The Addendum which should address the torus and its supports
%g (sde footnote on page 1-2 of Volume I) has not been received, p
Indicate the expected dates when the NRC staff could be briefed k
on this tcpic and when Addendum 2 would be submitted for NRC
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staff review.
Provide information on the adequacy of the torus
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and its supports in as much detail as that provided for other b_
structures, with particular attention to the combined effects q
g of LOCA-induced loads and seismic loads, and the effectiveness d
of current or proposed tie down assemblies.
y 3.
In item (h) of page 1-3 of Volume I and in Section 6.1.3 of e.g Volume IV, it is indicated that catwalks and platforms with solid Q
floor decking "may potentially fail" due to bulk pool swell loads h3 nd w
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y and may subsequently generate missiles.
Provide the basis for l
concluding that such; missiles will not hinder the function l
of any safety related equipment, electrical lines, instrument
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linas, piping or structures located above the catwalk or else-i where Within the torus.
Describe the missile impact analysis
)'
and provide a semmary of the results for the plate impacting on the torus or a vent pipe.
In view of this potential hazard
{
provide justification why the solid checkered plate platforms l
should not be replaced with grating, where appropriate, as a f
short term safety measure.
Furthermore, it is also indicated that local yielding will occur at the torus / beam connections.
Indicate if this yielding will occur in the torus shell itself i
)
and, if so, provide the expected strain, and deformation and
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discuss the potential effect on lecktight integrity. Also,
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discuss the possibility of torus compressive loads causing i
buckling at these locations, especially when subjected to seismic loads.
4.
I In item (1) of page 1-3 of Volume I and in Section 5.5.3.2 of Volume IV, it is indicated that local yielding of the liner plate (in the concrete suppression chamber) will occur.
Provide the basis for your conclusion that the liner will, nevertheless, re-tain its leaktight integrity. Provide a description of the extent of yielding, i.e.,
the expected strain, the region of yielding, the effect of attachments, etc.
C.
COMMENTS ON VOLUME III 1.
In Section 2.2 of Volume III, the suppression chamber shell wall has been listed as a non-critical structure. Section 4.3.10 of the same volume briefly described the analysis performed to arrive at this conclusion. Provide a summary of the resulting stresses or strains due to combined seismic and pool swell loads in criti-cal areas.
If stresses are above yield, then provide a justi-
' fication thereof with particular attention to buckling and leakage 9
i
fMNilWf _?$2522U22MiBi$lh:d5S%5f$3@dsi??F 'B50 l'Wd fidINEEN-potential at the beam / torus connections that were indicated to i
be critical.
In particularJr_the Brunswick torus liner, des-cribe the yielded region, the spalling and expected damage of j.
concrete anchors for the liner, and the negative pressure resisting capability and post-buckling behavior of the liner when. subjected j
to safety / relief valve discharge loads that may occur in conjun-ction with the LOCA I-D.
COMMENTS ON VOLUME IV 1.
Page 3-9.
Indicate the basis for determination of comparative vent moments, i.e., the loading condition, moment location, l
calculation techniques, etc.
l 2.
In Section 4.7, static load combinations S1, S2 and S3 are speci-fied.
In Section 5.4 it is stated that only S1 issignificant.
l Provide a summary of the results of an analysis indicating the l
most severe com'bination of HR, HT and HV acting concurrently on j.
each leg of a pair of downcomers along with other loads.
l 3.
In Section 4.7, provide the bases for only combining the horizontal f
load of every fifth downcomer in static load combinations S2 I
and S3, 4.
In Section 4, indicate if asymetric vent clearing and pool swell loads were considered in the analysis and, if so, provide the results of a bending analysis of the vent header and of a torsional analysis of the vent pipe for such loads.
5.
In Section 5.5.3, on Page 5-11 you indicated that the yield f
stress, and the minimum specified strain are exceeded and that the f-anchor would fail. On Page 5-14 you stated that the vents are expected to buckle. However, on Page 5-11 you conclude that the l
system will return to the original position by gravity action after the passage of the dynamic load. Provide the basis for such i'
j a conclusion, specifying the capability of the yielded system to resist fallback and other LOCA, seismic and safety / relief valve discharge loads.
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Page 5-14.
Doe to the failbre of the Brunswick header column
- 4..l anchor. ages, the high stresses in the vents at the drywell may h
cause localized dishing of the vent shell. You have also stated i
that the safety function of the assembly will not be impaired.
<>d In support of the hbove statements provide the following infor-e Q
mation:
h (a)
The maximum stress at the intersection of the vent and the drywell, the stress distribution at this location, and a a3 comparison with yield stresses, and (b) The maximum strain and strain distribution in this region, o
l$a (c) A discussion of the possibility of compressive buckling in
- (j the vent pipe due to seismic loads and the bases for your j
conclusion that the leaktight integrity of the vent pipe is
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maintained for the remainder of the LOCA event.
p 9
7.
Section 5.8.
A finite element analysis was performed to determine q
y the dynamic behavior of a sector of the vent header assembly M
when subjected to pool swell impact loads.
The results of this a
4,,
ana?ysis indicata tensile and compressive strains in excess of
[j-ten times the yield strain of the material. Subsequently, this assembly would be called on to resist fallback loads, horizontal q
3 vent clearing loads, etc. Describe your method of analyses which censider the post-buckling behavior of compressive elements.
9 Indicate which elements in Figure 5.8-1 are expected to yield
[
due to pool swell impact and their corresponding percent strain.
Compare these results with the yielded region identified in
.s the experimental lateral load tests. Confirm that the leak ai
- s tight integrity of the vent header assembly will be maintained
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when the post-buckling or post-yield behavior is considered.
p 8.
Section 6.2.2.3.
It is indicated that the downcomer/ vent-header assembly could be subjected to 250 cycles of lateral loads j:I which are random in magnitude and direction. Utilizing Figure p
f 1 of Volume II compare the fatigue consequences of fewer cycles M' 'tf m:
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h.j of a higher magnitude load versus more cycles of a lower magni-y;..
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tude load. Utilizing these_results, demonstrate that a 15 cycle Q
. test of high magnitude reversed loading is sufficient to verify AN the fatigue capability of the assembly, klM'-
9.
Appendix E, Figure B-11.
The lower portion of the Extensometers 79d.
is located in a region of considerable yielding.
Indicate h
possible errors in the strains reported from measurements with ldh these dial indicators, and the impact, if any, upon the results
[3 and conclusions of this test.
5d E.
C0H4ENTS ON ADDENDUM 1 TO VOLUME IV Wi R
1.
Upon failure'of the Brunswick anchor bar, the vent pipe header 4j assembly is expected to yield and the torus liner is expected f.
to rise 1.73 inches.
The bellows assembly must be capable of ef d
withstanding the vent pipe deformations caused by the anchor bar h
failure in conjunction with other loads and still maintain its d
leak tight integrity.
Indicate if this deformation i.s combined with -
f}j the pool swell impact load and wetwell compression. ' Describe h
the time history of these two loads on the bellows assembly.-
h If superposition of these loads is. possible then describe the f
method of analysis for these combined loads, and the long term -
program, if any, for experimental verification that the leak N'y tight integrity of the bellows assembly is maintained when sub-jected to these combined loads.
bA 2.
Section 3.1.
The reduced scale test was performed on a 36"
&y diameter bellows. A buckling analysis of this assembly has not Efj been discussed.
Discuss the applicability of the reduced scale v)g bellows water impact tests to predict the hydrodynamic response Q
of the actual full size assemblies in the local and overall g
buckling modes.
y l#-
3.
Figure 3.1-1.
In order to physically test a partial assembly,
.ij the boundary conditions of that partial assembly should approxi-mate the shears, moments, deflections and rotations at the corres-J afj 3$g 3
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h ponding section in the actual structure.
Provide a comparison
'g of the actual anticipated anLexperimental boundary conditions and Gj discuss their effects on the results and conclusions giving y
particular attention to the ovaling mode of the vent pipe at
]
these sections and deformations in the torus during pool swell impact.
h F.
COMMENTS ON VOLUME V N
p 1.
On Page 13 it is stated that consideration of various effects
.1 such as assembly tolerances, distortions of the structures, etc.
p-a..
could reduce the maximum. pressure in the actual structure to u
ki close to 50% of that being used in the analysis. Provide a isy description of the computations and a sumary of the results k
which lead to suct a conclusion.
h 2.
On Page 17, it is stated that the conservatism in load defin-I./
-ition and in analytical modeling are such that no yielding will f
I l$
occur in the Browns Ferry support columns, and that failure of J
the column anchorage in the Brunswick plant will be eliminated.
j Identify and justify the areas of conservatism in the analytical models and provide a description of the analyses and a sumary
[
of the results which support these conclusions.
a Q
G.
C0lHENTS ON THE LONG TERM PROGRAM ACTIVITY SCHEDULE dg 1.
With regard to the in-plant tests for S/R valve discharges dis-f, cussed in items (1), (2) and (3) of the long-term program, g
indicate if such tests are planned for concrete suppression chambers.
.d I'f not, provide justification to show that tests conducted on 1
6.y steel suppression chambers are representative and results a
.g therefore are applicable to concrete charr.bers, particularly 9
since the respor.se of a liner plate is expected to be quite 3;
different from that of a steel torus.
y.
U 2.
In item (3) of the program, your objective is to obtain torus 4
ht shell strain measurements to demonstrate structural adequacy.
d 1
This is acceptable for ascertaining structural adequacy for the s.
b.
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direct and imediate effects of the R/V discharge loads but not cj,
for potential fatigue failure Describe the tests and/or analysis u
j proposed to ascertain-the fatigue life adequacy for the torus vo and for any other structural member that may be so affected.
A d
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3.
The schedule proposed for establishing the acceptance criteria A,]
for ascertaining structural adequacy is not acceptable to the
[i staff.
It is felt that activities for this objective should o,
Y begin as soon as possible.
Provide your plans for ASME Code a-conimittee involvement for this purpose.
Describe specifically d
those items that this committee would be requested to study, i.e. load combinations, allowable stresses, variances from x
f.,1
. existing codes, strain limits, etc.
4.
It appears as though the long-term program was developed prior yj to completion of the short term program. Critical structures 1.$
or elements sited in the short term program are not the subject g
of further long-term testing.
Provide a description of your j
specific long-term plans to test critical structural elements 4,
Si sited in the Short Term Program final report.
<n
,qq 5.
Generic analysis of groups of similar plants may be used to
..ag predict their overall structural response. However, the struc-i tural response, particularly the local response, is affected by
- l plant-unique features and construction or field modifications.
Q Describe the long term plan to account for such plant-unique
]
items.
i
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6.
Describe your plans for increased in-service surveillance during t' e long term program for structural elements found to be' critical J
y h
i
.during the short term program.
My 7.
The hardware tests for potential structural fixes are scheduled
[j to start in the 4th quarter of 1975, prior to establishment of M
structural acceptance criteria in the 2nd quarter of 1976. This A
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is unacceptable to the NRC staff. Structural acceptance cri-i 3
teria must be established prior to designing and testing struc-l Ej tural fixes intended to satisfy these criteria.
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