ML20072F262
| ML20072F262 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 06/21/1983 |
| From: | Kemper J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8306270315 | |
| Download: ML20072F262 (19) | |
Text
'
PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET P.O. BOX 8699 1881 -1981 PHILADELPHIA, PA.19101 j
JOHN S. KEMPER l
V IC E-PR ESID E N T ENGIN1E RING AND EWESE ARCH l
Docket Nos. 50-352 i
l 50-353 Mr. A. Schwencer, Chief Licensing Branch No. 2
(
Division of Licensing U.S. Nuclear Regulatory Commission
Subject:
Limerick Generating Station (LGS)-Units 1 and 2 Open Items from the Structural Engineering (220)
Review of the LGS Final Safety Analysis Report (FSAR)
References:
(1) Meeting between N. Romney, et til. (USNRC) and S. H. Loo, et al. (Bechtel Power Corporation) on June 8, 1983.
(2) Letter from E. J. Bradley (PECO) to A. Schwencer, dated June 9, 1983.
l t
Dear Mr. Schwencer:
This letter represents our formal response to three Structural Engineering review open items which wer.2 discussed and resolved at the reference (1) meeting.
Our responses are as follows:
l 1.
With reference to our previous response to NRC concerns on the l
LCS design response spectra (SEB-DSER #1 in the reference 2 letter), the NRC staff requested that we also address the significance of the Regulatory Guide (R.G.) 1.60 spectra exceeding the LGS design spectra at frequencies of vibration l
of less than 1.0 hertz. This requested information is presented i
in Enclosure 1 in the form of a revised response to SEB-DSER
- 1.
l ol Soi (
8306270315 830621 PDR ADOCK 05000352 E
PDR l
1 L
o Mr.
A.- Schw:ncar, Chief Page 2 JN 211983 2.)
With reference to our previous response to Question 220.5, on the combination of spatial components in seismic analyses, the NRC staff requested that:
a.) we clarify the basis up2n which we have concluded that the absolute summation method (ABS) is sufficiently conservative.
b.)
we expand Table 220.5-1 to show more pertinent information regarding the comparison of typical stresses using the ABS method vs. typical stresses using the square root of the sum of the squares (SRSS) method.
The requested information is presented in Enclosure 2 in the form of a revised response to Question 220.5.
This response will appear in revision 23 (August 1983) to the FSAR.
3.)
In enclosure 3 we present our response to part (a.) of Question 220.22 (on the LGS Design Assessment Report). Part (b.) will be responded to at a later date. The response in enclosure 3 will appear in revision 23 (August 1983) to the FSAR.
With the above responses, the first two subject open items have been closed-out; and part (a) of the third subject open item has been closed-out.
Very truly yours,
?bSCf Enclosures : As stated Copy to: See attached service list.
cc: Judge Lawrence Brenner (w/ enclosure)
Judge Richard F. Cole (w/ enclosure)
Judge Peter A. Morris (w/ enclosure)
Troy B. Conner, Jr., Esq.
(w/ enclosure)
Ann P. Hodgdon (w/ enclosure)
Mr. Frank R. Romano (w/ enclosure)
Mr. Robert L. Anth:ny (w/ enclosure)
Mr. Marvin I. Lewis (w/ enclosure)
Judith A. Dorsey, Esq.
(w/ enclosure)
Charles W. Elliott, Esq.
(w/ enclosure)
Jacqueline I. Ruttenberg (w/ enclosure)
Thomas Y. Au, Esq.
(w/ enclosure)
Mr. Thomas Gerusky (w/ enclosure)
Director, Pennsylvania Emergency Management Agency (w/ enclosure)
Mr. Steven P. Hershey (w/ enclosure)
Donald S. Bronstein, Esq.
(w/ enclosure)
Mr. Joseph H. White, III (w/ enclosure)
David Wersan, Esq.
(w/ enclosure)
Robert J. Sugarman, Esq.
(w/ enclosure)
Martha W. Bush, Esq.
(w/ enclosure)
Spence W. Perry, Esq.
(w/ enclosure)
Atomic Safety and Licensing Appeal Board (w/ enclosure)
Atomic Safety and Licensing Board Panel (w/ enclosure)
Docket and Service Section (w/ enclosure)
SEB-DSER #(1)
. Response Spectra Frequencies (3.7.1) f In 'the design of plant structures, systems and components, an operating basis earthquake (OBE) of.075g horizontal and a safe shutdown earthquake (SSE) of 0.15g horizontal were used. The values for the vertical component of the Design Response Spectra
.i are 2/3 of the horizontal values described above. The response I
spectra are based on data developed from records of previous earthquake activity and represent an envelope of motion expected at i
a sound rock site from a nearby earthquake.
Comparison between the LGS Design Response Spectra and R.G.
1.60, i.
" Design Response Spectra for Seismic Design of Nuclear Power Plants",
indicated that for frequencies between 1 hz and 5 hz, R.G.
1.60 exceeds the LGS Design Spectra.
The applicant should discuss the significance of these exceedences on structures, piping, equipment and systems essential for the safe shutdown of the plant. The staff considers this to be a confirmatory item.
Response (revised):
The LGS design response spectra (Figure 3.7-1), in conjunction with the damping values shown in Tables 3.7-1 and 3.7-2, form the design basis for LGS seismic analysis.
For the seismic analyses of Category 1 structures (e.g. containment structure, reactor & control enclosure, _
diesel generator building, and the spray pond pump house) which 4
contain safety related piping, equipment, and systems, damping values equal to 2% and 5% of. critical are used for OBE and SSE, respectively.
In accordance with R.G.
1.61, damping values equal to 4% and 7% of critical are acceptable for these reinforced concrete structures.
Fbr comparison, the horizontal LGS design spectra are plotted with the R.G. 1.60 horizontal spectra in Figures SER-1-1 and SER-1-2.
These plots show that both the OBE and SSE horizontal LGS design spectra envelop the R.G.1.60 spectra for frequencies greater than 4
1.0 hertz.
For frequencies less than 1.0 hertz, the R.G. 1.60 spectra exceed the LGS design spectra. However, these exceedences i
have no structural significance on safety related structures and components since all LGS seismic Category 1 structures have a
,f fundamental frequency of vibration greater than 1.0 hertz.
The Vertical LGS design spectra are equal to two-thirds of the horizontal, per FSAR Section 3.7.1.1.
For comparison, the vertical LGS ' design spectra are plotted with the R.G.
1.60 vertical spectra in Figures SER-1-3 and SER.-1-4.
These plots show that the R.G.
1.60 vertical spectra are generally higher than the LGS design spectra.
1 4
r e
-+ - r
-en-.=
-v-r
-..,--t--ec.
,--e-r wn-w.,w,yn
,3, r------,--e--
--3 m v-wy,wc
--,w,-,-.mww.eww-...-%pr %
we,.,
vww.w. s,.,a
f-,
SEB-DSER f(1) (Cont. 'd)
In the WASH-1255 Report-(Reference 1) Newmark has shown, based upon 14 strong seismic motion records, that the ratio of vertical to the horizontal ground acceleration is two-thirds on the average.
Although only 3 of 14 earthquakes considered were on rock, the ratio of the vertical to the' horizontal acceleration is less in rock than in alluvium. Later, in the NUREG/CR-0098 Report (Reference 2)~Newmark recommended that the vertical design motion be taken as two-thirds of the horizontal across the entire frequency range.
In addition, from the research based on the analysis of 30 vertical recordings made on "hard" or rock sites, the authors Rizzo, Shaw, t
and Snyder report (Reference 3) that the ratio of two-thirds between the vertical and horizontal accelerations is conservative. Their study included sites located in the eastern United States, such as
' Blue Mountain Lake and New York.
It is stated in their report that the R.G.1.60 spectra envelop both rock and soil sites and, it is shown that the R.G.
1.60 provisions are overly conservative for "hard" or rock sites.
Since all principal Category 1 structures (containment structure, i
reactor & control enclosure l diesel generator building, and the spray pond pump L9use) of the project are founded on competent i
rock, we have concluded, based on the above discussion, that the difference between the LGS design vertical spectra and the K.G.
l.60 vertical spectra has no impact on safety related structures piping, equipment, and systems. The LGS design spectra, used in conjunction with the more conservative damping values, assures safe operation of the plant during a seismic event.
t
References:
i (1)
"A Study of Vertical and Horizontal Earthquake Spectra."
USAEC Contract No. AT(49-5)-2667, WASH-1255.
N. M. Newmark.
j.
Consulting Engineering Services, Urbana, Illinois. April.
1973.
(2) " Development -of Criteria for Seismic Review of Selected Nuclear Power Plants." USNRC Contract No. AT(49-24)-0116,
+
N. M. Newmark Consulting Engineering Services, Urbana, Illinois. May 1978.
.(3) " Vertical Seismic Response Spectra."
P. C. Rizzo, D. E. Shaw, and M. D. Snyder, Journal of Power Division, ASCE, January a
1976.
4 4
i
~
I I
s
- e
- e. %
PERIOD SEC.
9 18 18
.1 g et 8I 'I 8 8 8
8 3
ie3 i s a s e
e s ss: : i s
s g
LEGE8vD TIME MfSTORY RESPONSE SPECTRA
- ... DE58G88 RESPOstSE SPECTRA I:
3 5
.E
\\
k k
[
6 %^% @ b (C
m Yg.i... h b [J.kk.:
h%
)
4r
/
0.015 <'.
=
7-
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)
l
.. i..
.14
,ReOui CY.ePs
\\.
k%N Q
1 l
ktEttMBL.-bW l
LIMERICK GENER ATING STATION UNITS 1 AND 2 FINAL SAFETY ANALYSIS REPORI
(
COMPARISON OF TIME HISTORY RESPONSE SPECTRA AND DESIGN RESPONSE SPECTRA (2% DAMPING)
FIGURE
'N*
.. ~.
e e
6,
.s (k
P.RIOCHEC.
N2 12 01 est sea s s s a s
a e I s s I s s
a ssss s s s s
s i
LEGEND TIME HISTORY RESPO8vSt SPECTRA
- DESIGN RESPolv$E SPECTRA l
i s
i, 5
.t I
-WS'Dt%d3t&hm l
C5'k hhG)
C.
/
RM M
d' ?
A%
~
i sf /
,, g 0 6g.
"I s==e
.. i.
FRE OUENCY. CPS O
\\ \\b k%%QM - SE LIMERICK GENERATING STATION UNITS 1 AND 2 FINAL SAFETY ANALYSl3 REPORT COMPARISON OF TIME HISTORY
[
RESPONSE SPECTRA AND DESIGN RESPONSE SPECTRA (5% DAMPlNG) k-b-FIGURE
.-----.----e a
m
-w w---.,-%-.
-,--,-,w--
-r,e
,,m..
,m-,--3
.w
o,
~
/
.4
(-
1 1
PERMBEC.
2.
- u.,
s I l i i s
I i
65 1 5 1
I s
s aa i a s I
a b
LEGEND T'ME MISTORY REI*0NSE SPECTRA
...... DEllGN RESPONSE SPECTRA I
I E
RCi 1.60 SPEcium l
C4}IX%9MG0 t
/
j
/
l fR W6v f..7..
('
/
/
f
~ '.
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..D.035 q.
4.......&Y$
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e.1 a
4 e e i.o a
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4 a
a too FREOUENCY CPS b
NNbE@N I
I l
l RN-LIMERICK GENERATING STATKhN UNITS 1 AND 2 FIN AL SAFETY ANALYSl3 REPORT
(
COMPARISON OF TIME HISTORY RESPONSE SPECTRA AND DESIGN RESPONSE SPECTRA (2% DAM
- LNG) riouRE
- (ESA.-M y-
-.%-wre, w
,,,,..,m-v
4 PER MSEC.
18A 1A 6.1 est II I 3 s 5 5
3 g
g5 5 5 5 5 3 3
g g g g 5 5 5 5
I I
5 LEGEND Teest HISTORY RESPONSE SPECTRA DESIGN RESPONSE SPECTRA I
I I
5i I
[.
k-LD\\
l.
/
Gb%dW')
rNL
(
s J >P.%
f
/
%Q
-o.\\5 g..
-0.\\0.
~
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a e e so.o a
a e e too FRf 00ENCY. CPS LGS IkSEGA SnQte.(5%%sVWD i
l kt%Uhl DE l
I Lit 4ERICK GENERATING STATION UNITS 1 AND 2 FINAL SAFETY ANALYSi$ REPORT i
(
COMPARISON OF TIME HISTORY RESPONSE SPECTRA AND DESIGN RESPONSE SPECTRA (5% DAMPING)
($Q-(.k)
FIGURE
- y W
Tq-'c---
e-T M--
y g4q+-c-w-T y
7-myy--w,,.y-.y--w-gr
-y e-+-y-v
,.w.-eew-,-,+w,,-,--me'-N*W e
w-w--u=--wy
=rs ew-
'--+-w
(
OUESTION 220.5 (Section 3.7.2.6)
Section 3.7.2.6 of the LGS FSAR states that for design parposes, the design response value was obtained by adding the response due to the vertical earthquake with the larger value of the response due to one of the horizontal earthquake by the absolute sum method.
Regulatory Guide 1.92, " Combining Modal Responses and Spatial Components in Seismic Response Analysis" states that the design response value is obtained by taking the square root of the sum of the squares of the maximum codirectional responses caused by each of the three components of earthquake motion at a particular point of the structure.
Explain and justify the approach used in the LGS analysis.
RESPONSE (revised ) :
The Limerick structures are designed using an absolute summation technique considering the worst case response of the horizontal excitations in combination with the response of the vertical excitation.
A discussion of the adequacy of the conservatism provided by this two-component absolute summation technique as compared to the Regulatory Guide 1.92 requirement of a three-component SPSS procedure is provided below.
The general conditions for which the absolute summation of two resultants methods is conservative may be demonstrated by concidering the following:
min max R
fR where 0 5 f 5 1 where min max
=
H H
f R
R
=
H H
and max max R
CR 05 C < = where C = R R
=
V H
V H
where:
max R
= Larger of the two seismic co-directional responses due t
H to either of the horizontal earthquake components 220.5-1
F QSFSAR i'
min R
= Sma]Ier seismic co-directional responses due to the H
other orthogonal horizontal earthquake comWnent R
= Seismic co-directional response due to vertical V
earthquake miri max l
f
= ratio of R to R H
H max c
= ratio of R to R V
H therefore SRSS of three components can be expressed as follows:
! max
[ min l'
+
R
+
R (R
H /
(H )
( V)
[ max)2
[ max)2
[Rmax)2 2
(
2
+f
'R
+C R
Y
)
Y
)
Y Y
I 2
2 max 1 +f
+C R
)
(220.5-1) i The absolute sum of two components can be expressed as follows:
l max R
+R l
H V
max max R
+ CR H
H I
2 I max l
l
\\ (1 + C)
}Rg i
220.5-2 i
u s'
LGS FSAR TABLE 220.5-1 REACTOR ENCLOSURE AND CONTROL STRUCTURE -
COMPARISON OF 2-COMPONENT ABS VS,. 3 -COMPO
.~
l 1
' D l COMBINED AXIAL AND BENDING STRESSES ON CDNCRETE WALL SECIION l
j l
DUE 'IO:,_.
l l SSE Vert lSSE N-S ISSE E-W l
l Excitation l
Excitation j'
Excitatien l
(?_)
(M)
(M) l Elev (A) (KSF)
I N-S (KSF)
I E-W (KSF) l i
l Reactor Enclosure Wall - Southwc I
I I
I I
I l
352 l
12.27 l
23.4 l
10.2 l
333 l
0.92 l
18.6 l
13.4 j
313 l
0.88 l
26.4 l
19.5 l
l 304 l
13.85 l
26.5 l
22.1 l
l 283 l
14.19 l
37.1 l
30.6 l
l 269 l
14.56 l
43.4 l
33.0 l
l 253 l
14.92 l
51.7 1
39.7 l
j 239 l
16.11 l
59.4 45.7 l
l 217 l
16.44 l
71.4 55.2 l
l 201 15.18 l
57.2 55.9 l
l 177 14.35 l
63.1 l
64.2 l
l 1
I I
I Control Structure - Northeast i
I I
352 j
12.27 25.4 l
3.9 l
4 333 l
0.92 l
20.1 l
5.1 l
l l
313 l
'O.88 l
29.1 l
7.5 l
l 283 l
14.19 l
29.8
{
8.5 l
l 304 l
13.85 l
41.8 l
11.7 l
l 269 l
14.56 l
45.6 l
12.6 l
253 J
14.92 l
54.3 l
15.2 l
239 l
16.11 l
61.9 l
17.5 l
l 217 l
16.44 l
74.4 l
21.2 l
201 15.18 74.7 21.4 177 14.35 73.7 24.6 j
a
~
SEISMIC RESPONSE IENT SRSS METHODS AL SEISMIC STRESS (KSF)
IAL AND BENDING STRESS ON CONCPEIE WALL SECf1G4) i I
I D Component SR$
2 Component ABS
% Difference (R. G.
1.92)
(PSAP 2. 7. 2. 6) st Corner I
I 28.3 l
35.7 l
+26%
22.9 l
19.5 l
-15%
32.8 l
27.3 l
-17%
37.2 l
40.4 l
+ 9%
50.1 l
51.3 l
+ 2%
66.9 I
66.6
- l
+ 3%
56.4 l
58.0 l
76.7 l
75.5 l
- 2%
91.7 ll 87.8 l
- 4%
81.4 72.4
-l
-11%
91.2 78.6 l
-14%
I
__=
Cernar l
l I
28.5 l
37.7 l
+ 32%
20.8 l
21.0
-l
+ 1%
30.1 l
30.0 l
33.9 l
43.7 l
+ 29%
45.7 l
56.0 l
+ 23%
e 49.5 l
60.2 l
+ 22%
58.3 l
69.2 l
+ 19%
~
66.3 l
78.0 l
+ 18%
79.1 l
90.8
'l
+ 15%
79.2 89.9 l
+ 14%
79.0 88.1
+ 12%
m
(
f 2 I max l
(220.5-2) 1 1 + 2C + C
\\
]RH Equation 220.5-2 (absolute sum of two components) will be greater than or equal to equation 220.5-1 (three-component SRSS) when 2
f 2
2 1 + 2C + C 2
y1 + f
+C or 2
2 2
1 + 2C + C 2 1+f
+C or 2
2C 2 f C
or min 2
R H
21 (220.5-3)
C 2 1/2 f
where 0 $ f
=
max R
H This relationship is shown in Figure 220.5-1.
The relative conservatism of the two-component absolute and the three-component SRSS summation techniques may be illustrated by considering the ratio of equations 220.5-2 and 220.5-1.
This ratio will be defined as y. Then:
I 2), max H
y = ABS of 220.5-2
=
SRSS of 220.5-1
{
j1+f+C [R 220.5-3
- -,~..~ ~
LGE FSAR 2
y=
1 + 2C + C (220.5-4) 2 2
1+f
+C where min R
H
$1, as before 05f
=
max R
H This relationship is shown in Figure 220.5-2.
As shown above, the Limerick two-component absolute summation method is conservative when the co-directional response due to the vertical excitation is equal to or greater than one-half the higher of the two horizontal responses (C k 1/2), regardless of l
the relationship between the two horizontal responses.
C i
The minimum possible ratio between the two-component absolute summation method and the three-component SRSS procedure is equal to 0.707.
This would occur only when the response due to the l
vertical excitation is zero (C=0) and the two horizontal responses resulting from the two horizontal excitations are equal (f=1).
However, this case is unlikely to occur, and any other relationship of the various response components would produce a ratio larger than 0.707.
The ratio between the two procedures, as shown in Figure 220.5-2, would be greater than one in most cases.
l To further demonstrate the relationship of the seismic response components on the Limerick structures, an evaluation has been performed for selected critical structura) elements within the structures.
Details of the evaluation are provided in the following paragraphs.
a.
Containment Exterior Shell For the structural design of the containment shell, consideration of two horizontal components is not necessary due to the axisymmetric nature of the shell.
The maximum resulting loads from two horizontal 220.5-4 l -,,
earthquake components would not be coincident and would occur 90 degrees apart on the circumference of the shell.
Furthermore, when the resultant force from one horizontal component is maximum at-a given location, the resultant force from the orthogonal horizontal component would be zero. This relationship corresponds to f=0 in Figures 220.5-1 and 220.5-2.
Therefore, the two-component absolute summation technique would produce a more conservative design, b.
Reactor Enclosure and Control Structure Stress evaluations were performed for critical locaticns in the reactor enclosure and control structure.
The northeast control structure and southwest reactor enclosure corner model locations are selected because of their sensitivity to large orthogonal responses due to out-of-plane seismic motion. The results obtained from the SSE seismic analysis are combined by the two-component absolute summation (ABS) and three-component square root of the sum of the squares (SRSS) methods and are compared in Table 220.5-1.
For 14 out of 20 wall locations evaluated, the seismic stress response comparison shows that the, two-component ABS method is more conservative than the three-component SRSS method.
In general, the two-component ABS method and the three-component SRSS method produce comparable results. Although the differences between the combined stresses from the two methods are small, the values for some locations suggest that the two-component ABS method may not be conservative when the seismic load is considered to act alone.
There are six wall locations where the two-component ABS method is less conservative.
The critical wall location is the southwest corner of the reactor enclosure, at elevation 177 feet, where the differential between ABS stresses and SRSS stresses equals 14 percent.* (See table 220.5-1.)
- However, when the seismic stresses are combined with the stresses due to other design loads, the effect of the differential between -
' AB3 stresses and SRSS stresses is reduced in proportion with the ratio of seismic wall load to total wall load.
In addition, the critical wall (wall line "D" at elevation 177 ft.) is loaded to only 52% of its capacity (based on combined axial and bending stresses due to all design loads as shown in Figure E.1-35 of the LGS Design Assessment Report).
Therefore, when considering the reduced effect of ABS vs. SRSS in conjunction with the caple excess capacity of the wall, the use of the ABS method for calculating seismic stresses provides adequate conservatism when considered in combination with other loads in the design of the reactor enclosure. and control structure.
This location is considered critical not only because of the difference between the ABS and SRSS stresses but also because of the level of the stresses.
220.5-5
g4%
(
4, 1.0 0.9 0.8 0.7 f
0.6 l}
,k 0.5 U
0.4 RESPordSE FROM 2-COMPONENT ABS >3-COMPONENT SRSS 0.3 2
0.2 C = 1/2 f RESPONSE FROM 0.1 3-COMPONENT SRSS >2-COMPONENT ABS l
l 1
I I
I I
i O.1 02 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 f ),tR mm/R ** ")
ib H
a.
C
- RATIO OF THE RESULTANT DUE TO THE VE RTICAL COMPONENT TO THE MAXIMUM RESULTANT DUE TO EITHER OF THE HORIZONTAL COMPONENTS b.
f = RATIO OF THE SMALLER RESULTANT DUE TO EITHER OF THE l
HORIZONTAL COMPONENTS TO THE LARGER RESULTANT I f 41.0)
Lit 4ERICK GENERATING STATION UNITS 1 AND 2 FINAL SAFETY ANALYS18 REPORT
(
COMPARISON OF 3-COMPONENT SRSS TO 2-COMPONENT ABS FIGURE 220.51 l
e- %
I I
I I
I I
I I
i mm f"
. o <f < i.o c-
.o<c<=
1.4 -
man max g
g H
H
' ~
1+C E
1 + 2C+ C y,.,2. c.
,.12.c2 f.1 FOR O <f41.0 1.1 -
2-COMPONENT ABS m
IS CONSE RVATIVE
). 2c. c u - - - - -.:e. w- - - - - - - - - - - - - - - -
2 2 2 1 f +c 0.9 (Eq. 220 54) 0.8 -
0.7 1
2 3
4 5
6 7
8 9
10
- c. "'/Rg" l
l 1
f LIMERICK GENERATING STATION UNITS 1 AND 2 l
DESIGN ASSESSMENT REPORT RELATIVE CONSERTIVISM OF THE TWO-COMPONENT ABSOLUTE AND THREE -COMPONENT SRSS TECHNIQUES FIGURE 220.5-2
220.22 The following concerns are related to'your responses in relation (DAR) to questions 220.17 and 220.19.
a)
In response to question 220.17 you indicated the DAR sections where stress margins for various structures or structural components can be found.
A review of the values provided indicates in some of the cases there is little margin left.
In your response to question 220.20, it is observed that some incorrect pressure values have been'used in the investigation of liner fatigue.
In view of this latter observation provide your assurance that the actual stress does not extend beyond the margin in those cases where there
-is barely any margin.
b)
In response to question 220.19 you indicated that damping values greater than 7%.of critical are used.
In Section 7.1.8.1 it is stated that-in the analysis and design of electrical raceway system, different damping vclues are used for different support systems and different loading conditions.
In addition it is stated that the damping ratios used for the electrical raceway assessment are in accordance with Reference 7.1-12.
Provide the justification for using different damping values for dfferent support systems and for different loading conditions and state clearly what damping values are used for electrical raceway assessment. The use of damping values greater than those specified in Regulatory Guide 1.61 should be justified.
i i
l r
j
)
---.+-.e,-,%
y.
.r-r-
---..--..-,--.-.,v---.-
.-...-w,m,
- - _ _ _. _.. m. - _ _ _. _ _ _ _. _.
l Response To: NRC Question 220.22(a)-DAR All load bearing structures, systems, and components were assessed for the Mark II hydrodynamic loads using dynamic time history analysis methods, as discussed in DAR Section 7.1.
The input pool-structure interface pressure time history traces, used for the above analysis, include appropriate amplitude and frequency modifiers.
\\~
concrete and is non-load bearing, the peak negative SRV pressure is For the assessment of the containment liner plate, which is backed by obtained from the digitized pressure time history used as input for the
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t s
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, dynamic analysid described above. This digitized SRV pressure included a 1.5 pressure multiplier, as discussed in DAR Section 4.1.4.1.
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additional multiplier of 1.5 was inadvertently applied to this digitized s
SRV pressure and resulted in the " incorrect" pressure values originally used for the liner plate assessment.
Since load bearing and non-load bearing itens (structures, systems, and components) were assessed independently of each other, there was no carry-over of the liner-plate assessment error to the other items. In addition, an independent third party review, of the technical bases used for the Mark II hydrodynamic load assessment, has provided assurance of the adequacy of the design assessment presented in the LGS DAR.
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