ML20247E045
| ML20247E045 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 03/23/1989 |
| From: | Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 89-175, NUDOCS 8903310281 | |
| Download: ML20247E045 (39) | |
Text
=
- F~
q o.
1
/
s VIRGINIA ELECTRIC AND POWER COMPANY HICIIMOND,VIHOINIA 202 61
- @,U^",',5"'["'
March 23,-1989 Nues. sam
' United States Nuclear Regulatory Commission Serial No.89-175 Attention:
Document Control Desk PES /JST Washington, D.C.
20555 Docket Nos.
50-338 50-339 License Nos. NPF-4 NPF-7
{
Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 REQUEST FOR ADDITIONAL INFORMATION StilLEMtRI 0F CLASS 1 STRUCTURES This letter is in response to questions posed by the NRC in a meeting between representatives of the NRC and the Virginia Electric and Power Company held at North Anna Power Station on February 22, 1989. This meeting was held 20, 1988 (Serial No.87-746)ge Request which was submitted to the to discuss a Technical Specification Chan concerning the differential NRC on March settlement between Points 117 and 113R and the resulting pipe stress in the Service Water Lines (SWL). The February 3,1989 survey.of Settlement Monitoring Points 117 and 113R, which indicated that 100 percent of the allowable differential settlement between these points as defined in Technical Specification 3/4.7.12 had occurred, was also discussed.
A brief synopsis of the history of the Settlement Monitoring Program for Class I structures at North Anna Power Station is presented in Attachment 1.
Responses to individual questions posed by the NRC are presented-in Attachment 2.
Plots of settlement for selected monitoring points discussed in Attachments 1 and 2 are included in Attachment 3.
In summary, the information presented in Attachments 1, 2, and 3 confirms that:
- 1) The Unit 2 Main Steam Valve House and other rock founded structures are stable and not rising as the previous survey data had indicated.
- 2) The Service Building is continuing to settle at a very slow rate, as are other soil founded structures throughout the site.
- 3) A more accurate measurement of the movement between Settlement Monitor-ing Points 117 and 113R indicates that only 67% of the Technical Specification allowable limit has occurred.
- 4) The original pipe stress analysis is conservative and, therefore, increasing the allowable differential settlement from 0.030 ft. to i
0.047 ft. is justified.
/;ool I
I 101-JST-2716S-1 I
I 8903310281 890323 5
PDR ADOCK 05000338 P
PLC m
~
,{
- r 4
If you have any questions or require additional.information, please contact -
us.
Very truly yours, lf W. R. Cartwright Attachments cc: U.S.. Nuclear Regulatory Commission Region II Suite 2900 i
101 Marietta St., N.W.
Atlanta, Georgia 30323 l
Mr. J. L. Caldwell NRC Senior Resident Inspector North Anna Power Station 101-JST-2716S-2
,m._
_y..
e
I 6
4' ATTACHMENT 1 101-JST-27165-1
,c
('
p; n.
L.'
.g-BRIEF SYNOPSIS OF SETTLEMENT MONITORING OF-CLASS I STRUCTURES-Construction survey monitoring was performed along the C-Line of the Turbine Building as early as.1972.
Column Line 1 of the_ Turbine Building,-
which is' rock' founded, was used as a bench mark by construction surveyors to establish'and monitor elevations of.other points on buildings in the plant -
area.
No formalized surveying procedures or standards.of accuracy were required or used for these early' construction surveys.
In 1975, Virginia Power contracted an independent' surveying firm to-perform..
formal settlement monitoring of Class I structures in compliance with the Technical-Specifications and other commitments.
Reference monuments A and B were established as benchmarks from which to determine the initial elevations of settlement monitoring points on Class I plant structures.
These monuments, which are soil founded, are located in the area of the Service Water Reservoir, more than 1000 feet from the plant and some 60 feet above plant grade, which results in long runs and numerous turns.
This is significant because the allowable closure error increases with the length of run. -In addition, the distribution of the actual closure erro'r to each monitoring point is based on the number of turns.
I The Technical Specifications. indicate that surveys to establish elevations of the settlement monitoring points are to be performed to Second Order Class II accuracy in accordance with the U.S. Department of Commerce, National Ocean-dc and Atmospheric Administration Standards.
101-JST-27165-2 I
[
S During the initial survey conducted in May 1976, which was used to estab-l lish the elevation of most of the monitoring points on Class I structures including Points 113 and 117, and during subsequent surveys, many points were 1
obstructed or blocked requiring they be surveyed using nonstandard techniques, for example, the use of a folding Engineer's Rule instead of a standard survey-ing rod, offsetting the actual point, not plumbing the rod,' modifying sight distances, etc.
Consequently, the survey accuracy was compromised to some degree when the points were obstructed.
During the period from May 1976 to the end of May 1979, continued survey difficulties and inaccuracies were also experienced due to damaged or destroyed points and conflicting base value dates in the Technical Specifications. After a meeting with the NRC held on December 5, 1978 to discuss these concerns (Docket No. 50-338), the entire monitoring program was reviewed and several steps were taken to improve the program.
(1) Redundant points were established for several of the-monitoring points in t,he event that the primary point was destroyed, temporarily blocked by construction activity, or if construction of a new component made the old point permanently inaccessible.
Protective covers were installed over many of these points to ensure they would not be dam-aged.
(2) A Request to Change the Technical Specifications was initiated to clarify the base dates and elevations for several of the monitoring points.
101-JST-2716S-3
}
v.
~
~
y
. (3
((3)l A; formalized written: survey 'procedur'e.fo' the Settlement Monitoring r
. Program was established for the monitoring of Class I structures to -
- Second~ Or(er, Class II ~ survey accuracy.
t
.(4)
In1 order to improve the accuracy of the. survey by reducing the -length
~
of the runs' and the number of turns required; two.new permanent' rocki-founded reference monuments -J and K were established: close to-the -
structures'at plant grade.
i The locations selected lfor the new monuments were removed from heavily traveled areas'and were ' easily accessible for survey reference. Their place-r ment into solid bedrock minimized. the potential for erratic settlement readings; due to possible fluctuations.in the' elevation'of the soil founded monuments.
In order to establish a base elevation for each of5 the new rock founded monuments, J and K, a First Order survey was conducted.
Six settlement moni-toring points located on rock founded structures, whose previous settlement history had indicated essentially no movement, were selected to establish the base elevations for the new monuments.
' From July 1977 through October 1987, a Yard Rod which is constructed of wood,. graduated to 0.001 of a yard, and consists of one section three meters long was used to read elevations on horizontally mounted points. The monitoring accuracy of the Yard Rod is to 0.003 ft.
After April 1987, a Metric Invar Rod was used since the Yard Rod was no longer available.
The Metric Invar Rod is aluminum, three meters long and has graduations of i cm. The scale is highly resistant to thermal movement due to temperature changes and is l
101-JST-2716S-4
p
~ accurate to 0.002 ft.
The base of this rod is l'15/16" x 3 7/8". The traverse
_used to. survey the elevations-of Point 117 and 113 begins with reference monument J, runs along.the west side of the Unit 2 Containment, through Point:
l 113 and 117 and ties back with temporary benchmark Point 234 or reference monument-J. All points within this traverse except Point 113 are horizontal plates, scribe marks, or turning pins and are read with the Invar Rod or the Yard Rod.
Horizontal projections from walls, such as Points 113, were measured using a Philadelphia Rod due to the size and configuration, of its base. The Philadelphia Rod is constructed of wood and has a netal face graduated to 0.01 ft.
It can be used for short sight distances to an accuracy of 0.005 ft.
Point 113 consists of a 3/8 in. diameter reinforcing rod which projects 5/8 in, from the wall of the Unit 2 MSVH.
Obstructions to Point 113, which pre-cluded the use of the Philadelphia Rod, resulted in the installation of redun-dant Point 113R in November, 1979.
Point 113R consists of a 1 in. diameter I
stainless steel rod which is also embedded in the wall of the Unit 2 MSVH.
It 4
projects 1 1/16 in. from the wall.
101-JST-2716S-5 l
0 4'
ATTACHMENT 2 RESPONSES TO SPECIFIC NRC QUESTIONS 101-JST-27165-1
L 4,
t.
p, K#
0
-QUESTION: Provide the NRC with the' pipe stress analysis, calculation.-
.i 4,
I
RESPONSE
A' copy of the pipe stress analysis calculation, " Settlement. Stresses on Service' Water Lines'24"-WS-426, 428, 434, 436-151-Q3 between
. Service Building and-Main Steam Valve House", Calculation'No.
12050-NP(B)-094-X9, Rev.1, was provided.to ~ the. NRC at the February.
-22, 1989 meeting.:
i i
' l..
/
i.
1 i
-i i
l l
l t
101-JST-2716S-2
_____________________.______.____1
-j
y(
(j.
-QUESTIONF-Discuss the movement of the Service Building and Unit 2 Main Steam
' Valve Housef(MSVH) including other points on the same buildings, and explain the' apparent rise of the Unit'2 MSVH.
RESPONSE
In order to' understand the movementtof the Service Building, a brief description of the foundation conditions is required. This information_has been previously documented in the~following: a.-
Technical Report entitled " Differential Settlement" submitted to NRC 4
on February 20,1981 (Serial No.118), the previously submitted Technical Specification Change Request, dated March.10,'1988 (Serial 4
No.87-746) and Section 3.8 of the UFSAR.
A description of the foundation conditions is provided below.
The western end of the Service Building is underlain by a variable H
thickness of compressible, soil-like, decomposed rock called "saprolite." Figure 1 shows a plan of this area, together with column lines and the locations of other settlement monitoring points on the Service Building and Unit 2 MSVH.
The presence of this compressible material has resulted in settlement of the Service i
Building to the west of the 10 Line.
In general, the settlement has l
been the greatest toward the 17 Line.
This can be observed in the i
settlement plots for Points 114,115, and 117, located.on the E-Line of the Service Building.
Since May 1976, the initial rate of settlement is greater for Points 114 and 115 than for Point 117, as is the magnitude of recorded settlements to date.
There has been a noticeable decrease in the rate of settlement of all points since
-1982.
The 'present trend indicates that settlement of the Service Building is continuing at a very slow rate.
101-JST-2716S-3 2
m -~
y-G g
'i f 4
'The Unitc2 MSVH is partially.' supported:oniconcrete' backfill bearing-directly:on_ solid bedro'ck' adjacent _to the Unit 2 containment. The-north end of the~ Unit.2'MSVH is' founded on a-layer of:saprolite
'aboveLsolid bedrock'as shown in Figure 2.
A review of the settlement plot for. Point 113 (113R) on the MSVH indicates.a trend i
- of apparent' upward movement of,this. structure since May 1976.
A survey conducted onLMarch 9, 1989 indidated'an' additional upward movement of the Unit '2 MSVH of 0.004-ft. 'since the. February 3,1989
~
i
survey. Both surveys were conducted utilizing a folding' Engineer's-Rule since the Philadelphia Rod was' unavailable at the time.
.In order.to determine.if any' inaccuracies were present'due to the use-of different rods on Point 113R, two additional surveys were conducted'on March 13, 1989 and.on March 16, 1989.
Results of the March 13 and 16, 1989 surveys are provided.in Table 1.
The surveying technique employs a side shot on Point 113R.
Point 113R is not used as a turning point which means that any error.or discrepancy in the measurement of Point 113R is not carried through for the rest of the surveying loop and also could not be detected in the closing error.
The error could only be identified by taking companion shots with a single instrument set up using different rods.
101-JST-2716S-4
l tbna ew 0
7 3
7 0
7 7
7 7
7 7
co 1
6 0
9 6
6 0
9 6
0 9
rl 1
1 1
1 el PA eR c3 n1 e1 3
0 1
9 8
0 2
9' 0
2 9
r 3
2 3
2 1
2 3
2 2
3 2
e-0 0
0 0
0 0
0 0
0 0
0 ff7 0
0 0
0 0
0 0
0 0
0 0
i1 D1
)
7 1
e 9
4 7
5 4
7 5
2 7
5 2
1 ge7 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 nc7 T) an/
NR hi7 0
0 0
0 0
0 0
0 0
0 0
I3 CS O1 P1
('
T2 GN NI D I ON R
DPA 3
0 7
8 6
7 4
6 3
4 6
3 L( -
.1 4
2 3
3 2
2 3
3 2
3 3
I 1
S v1 6
6 6
6 6
6 6
6 6
6 6
UE Y
e BSS E
l 2
2 2
2 2
2 2
2 2
2 2
UT V
Et 7
7 7
7 7
7 7
7 7
7 7
EOI R
P 2
2 2
2 2
2 2
2 2
2 2
CHN U
I U
S VE' RVN T
lELO N
' SAI E
E VT C
e LN A
E ge7 4
4 4
4 2
7 7
7 7
7 7
BEMT R
nc7 2
2 2
2 2
2 2
2 2
2 2
AEAS an/
0 0
0 0
0 0
0 0
0 0
0 TWE F
hi7
' TTR O
CS 0
0 0
0 0
0 0
0 0
0 0
ESE B
W S
- NO T
TI P L
NA U
EMA S
M N
E E2N R
7 1
1 3
8 8
L A
.1 6
6 6
5 5
TT v1 3
3 3
3 3
TI H e
ENT l
1 1
1 1
1 SUR Et 7
7 7
7 7
O P
2 2
2 2
2 LEN AH IT TND d
d d
EN e
o e
o e
o RA l
e R
l R
l R
E u
l u
u F
R u
a R
a R
a F
d R
i i
i I
eR h
h h
D s3
's d
's p
d d
's p
d
's p
U1 r
o r
l o
o r
l o
r l
1 e
R e
e R
R e
e R
e e
d e
e d
e d
e d
on n
r n
a r
r n
a r
n a
R o i
a i
l a
a i
l a
i l
g v
g i
v v
g i
v g
i n
n n
h n
n n
h n
n h
~
E I
E P
I I
E P
I E
P
)
)
)
)
91 92 9
1 9
2 y
9 8
8 8
8 e
8
/p
/p
/
p
/
p ve
/
3 o 3o 6
o 6
o rt 9
1 o 1 o 1
o 1
o ua
/
/L
/L
/
L
/
L SD 3
3(
3(
3
(
3
(
yl l
i
.l All points with the exception of.113R were read using the Invar rod.
Using the same instrument set up the elevation of 113R was obtained using:
g Type Rod Estimated Accuracy (Ft.)
1) the Engineers Rule 0.005
- 2) the Philadelphia rod 0.005
- 3) the Invar rod 0.002 The results of the above mentioned survey were further verified on March 15 and 16, 1989, by conducting test comparisons of the three rods. vhe same Engineers Rule, Philadelphia rod and Invar rod. The resdits of the tests are shown below.
COMPARIS0N CHECK RODS USED ON PT 113R Date Rod Difference (Ft) 3-15-89 Invar - Serial No. 8680 0.000 Invar - Serial No. 8681 0.000 Philadelphia Rod
-0.009 (shorter)
Engineers' Rule
-0.012 (shorter) 3-16-89 Invar - Serial No. 8680 0.000 101-JST-2716S-5
Invar - Serial-No. 8681 0.000 Philadelphia Rod
--0.009 (shorter)
Engineers' Rule'
-0.011(shorter)
The results confirm that there is a discrepancy in these readings for the various rods used.
The discrepancy between the Engineer's Rule or Philadelphia Rod and the Invar Rod resulted in an apparent upward movement of Pt. 113R and in turn the Unit 2 MSVH. We therefore conclude that at least a part of the apparent movement.of the Unit 2 MSVH can be attributed to inaccuracies.in obtaining the elevation of Points 113 or 113R using the shorter rods.
A review of plots of settlement readings for Points 130 and 125 located on the Units 1 and 2 containment, respectively, indicates the same apparent upward movement of these structures.
Plots of these points are provided in Attachment 3.
Both containments are rock founded at elevation 203 and are.shown in Section A-A, Fig-ure 2.5-4 of the UFSAR (Figure 3). The foundations are cut 50 ft. into bedrock.
Plots of Points 130 and 125 also show wide scatter prior to May 1979 and a reduced scatter since 1979.
l l
Consequently, it can be concluded that the apparent " rise" of rock founded structures, including the Unit 2 MSVH, is nothing more than inherent survey inaccuracies.
In addition, it can also be concluded that the most accurate representation of the differ-ential settlement of the Service Water Lines is the total down-101-JST-2716S-6 l
\\'
l ward movement of the ' Service' Building as. represented by Point 1
117.-
The surveying procedure will be revised to ensure that an increased level of surveying accuracy'is maintained.
i 101-JST-2716S-7 i
E m=
l
e
- e i.
e QUESTION: Have attempts been made to predict settlement. and if so, ho'w accurate have they been?-
RESPONSE: Original settlement predictions of main plant structures are contained in Appendix 2H of the'UFSAR.
Original settlement pre-dictions were based on results of consolidation tests performed on undisturbed samples secured from the residual saprolitic soils.
Based on results of soil test borings and consolidation tests
. performed on the.saprolite, it was estimated that the Service Water l
Pump House (SWPH) might experience as much as.012 ft. (1.5 inches).
I of = total settlement. This prediction is contained in the PSAR for Units 1 and,2.
Predictions based on the results of the consolidation tests have tended to underestimate settlement-which
-actually occurred and therefore, later predictions were based on extrapolations of past settlement data and coefficients of secondary compression obtained from consolidation tests.
Most of these-studies and predictions deal with structures around the Service.
Water Reservoir and have been previously submitted to the NRC.
i Included in these submittals are:
1)
" Report on Geotechnical Investigations of Service Water Reservoir," North Anna Power Station Units 1 and 2, Virginia Electric and Power Company, October 1975, Appendix E to UFSAR.
l l
2)
Report on Settlement of the Service Water Pump House, North Anna Units 3 and 4, March 1976, submitted to NRC 3-31-76, Serial No.
957.
101-JST-2716S-8
l dh per
, pg ' J '. ;
s; 1
=
p B
3)
'"Vepco's Test'imony on Service. Water Pump House Settlement,"
served on1 Atomic Safety 2and: Licensing Appeal Board in' response-to-1 Order ALAB-529, April 27,1979.
p f
- Information on settlement of the Service Building,> including ' pre-d dictions'offsettlement, are contained in'UFSAR Section 3.8.5..
An additional. submittal to the NRC, " Differential Settlement,. North-Anna Units 1 & 2, ' dated February.20,.1981--_(Serial No.: 118), dis-cussed the. history of settlement of the Service Building and pre-dicted'that 100% of the allowable differential s'ttlement'b'etween e
i Point 117 'and-Point 113 in Table 3.7-5 of.the Technical Specifi-'
ll 1
cation was expected.to be exceeded within the next two years, which would have been in early 1983. This prediction was based' on'the total downward movement of the Service Building and no movement of the Unit 2 MSVH..Here again, attempts to predict settlement did not match' the actual recorded-settlements of the structure, since the allowable differential settlement was not exceeded in 1983.
101-JST-2716S-9 I
=
. QUESTIONi Is there any correlation between settlement or fluctuations,in -
p
, settlement with rainfall, temperature or seasonal. effects? -
RESPONSE: Attempts were made in late 1975 to explain erratic. settlement data for the' SWPH by correlations with rainfall, temperatures or the.
seasons.
No correlations were found and the effort was abandoned.
It is concluded that there is no correlation between rainfall, temperature, or the seasons other than how they' effect the survey.
s 9
101-JST-27165-10
.j [
. QUESTION: ~ Discuss and.present a plot of settlement of the Service Water Pump House and present plots of this settlement.
RESPONSE: PlotsofpointsmonitoredontheService.WaterPumpHouse(SWPH)-
floor (3M-9), and the expansion, joints (SM-15) for the service water
~'
lines located just north of'the SWPH, exhibit similar curves to l
those for Class I structures in the plant.
Plots of these points i
are provided in Attachment 3.
The scatter and survey inaccuracies
-for the SWPH are less significant due to the magnitude of.
L
.. settlement. -.For. example, a change of 0.010 from the previous j
reading does not stand out when settlement in the range. cf 0.25 feet f
is plotted.
The settlement' history of the SWPH and other facilities around the I
service water reservoir is contained in:
- 1) "Vepco's Testimony on Service Water Pump House Settlement,"
served on Atomic Safety and Licensing Appeal Board in response i
to Order ALAB-529, April 27,1979.
.l
- 2) " Report on Monitoring of Settlement and Groundwater Level at Ser-l l
vice Water Reservoir, North Anna Power Station,. Units 1 and 2,"
Virginia Electric and Power Company, February 1983.
i l
i 101-JST-2716S-11
e'
?y
-QUESTION: The_NRC staff suggested the use of strain gauges on pipe as an' alternate method to' verify strain on.the pipe. : Virginia Power considered that it will be difficult, if not impossible to get an accurate verification of strain by use of strain gauges. The staff requested that Virginia Power consider other alternatives to verify-strain determined from analysis.-
i RESPONSE: The service' water pipe in question is buried 13 ft. below grade. A successful. application of strain gauges cannot-be made to verify the strain in the pipe accurately for the following reasons.
The predicted location of the highest pipe stress due to the limiting settlement value is within the portion of pipe encased in concrete and therefore, application of strain gauges in the vicinity.
of that location would not be possible.
The nominal stress caused by the limiting settlement, on the non-encased sections of the pipe is extremely small.
The only significant stress in the non-encased sections is predicted at elbow locations with the use of a stress intensification factor of 4.27.
Stress intensification factors are used as multipliers on the nominal stress to arrive at an intensified stress.
Stress intensification factors are derived from fatigue tests of components. A measurement using a strain gauge cannot accurately provide intensified stress. Moreove.', any measurement performed on the non-encased portions has to be used in analysis to predict strains on the critical encased sections for the purpose of 101-JST-2716S-12
g 4-
,1, p
- ,'h
-i.
3,;
Xy ' '
, verification. (Therefore the application of strain l gauges in the:
'non-encased portions will not provide any reliabis independent.
. verifications of strain in.the encased portion of the pipe.
e The.insta11ation' of strain gauges.can only. measure the' increase in-strain f, rom the time.the gauges are installed. The incrementa1 differential settlements over"a period of time',l currently. being-
~
+
Y
' determined by the survey. is so small that. the increased strains due
~
to' the increased differential settlemen't may not be-measurable.
At any time.,-the measured strain from the strain gauges installation
~
will reflect the combined effects of,. pressure, deadweight, thermal ~
expansion,1 surcharge,~.and _ other operational loadings.
It.would-not be possible to separate out the strain due to'different loadings and
- assign any-meaningful value to the strain increment due to
' differential. settlement alone.
In~ addition, there is always thel physical limitation of installing strain gauges 13 feet under ground in adverse-environmental conditions and securing them properly to get readings with sen-sitivity comparable to laboratory conditions.
Virginia Power is considering an-alternate method to more accurately.
define the movement of the Service Water Lines (SWL) between the Service Building and the Unit 2 Main Steam Valve House (MSVH).
Present settlement monitoring of Points 117 and 113R does not provide the most direct measurement of the movement of the SWL.
Settlement Monitoring Point 117 is located on the floor slab just 101-JST-27165-13
inside.the Service Building at an approximate elevation of 271.4.
Settlement monitoring points 113 and 113R are located outside on the wall of the Unit 2 MSVH at elevation 272.5.
The SWL are located below grade at elevation 259, some 12 to 13 feet below the settlement monitoring points. As shown on Figure 2, Column E-14 bears directly on the concrete encasement of the SWL.
The SWL enter-the Unit 2 MSVH through a wall penetration above the foundation and are not concrete' encased at their entry point.
The proposed alternate method would consist of establishing two new monitoring points to be used in conjunction with existing Points 117 and 113 (113R).
One new point would be located on the outside wall of the Unit 2 MSVH, directly above the location of the below grade SWL crossing. The second point would be located on the outside wall of the Service Building, directly above the SWL crossing.
The new monitoring points would be added to our Settlement Monitoring Surveillance procedure. The two new monitoring points would then be the principle measure for the differential movement of the SWL between the Service Building and the Unit 2 MSVH.
An initial reading can be taken directly on the new monitoring points that will establish a difference-in elevation between the two points.
Subsequent measurements of the differential movements along the SWL can be made by directly measuring the difference in elevation between the two points and noting the change since the previous reading.
This can be measured with one setup near the points and l=
will not require a survey loep and its associated closure errors and inaccurries.
l 101-JST-2716S-14
p.
(
8^
This proposed alternative will provide additional assurance that any.
actual increase in differential settlement directly affecting the SWL is detected and assessed. The new points, if installed, may be able to be used as redundant points and. monitored in lieu of the existing Technical Specification points.
In conjunction with the-enhanced survey techniques we expect that this alternative will substantially increase our ability to accurately measure' differential movement.
g i
l 4
1 101-JST-2716S-15 I
l
+
+
QUESTION:- Propose a parametric study to verify the. influence of parameters like the soil spring stiffness, node point spacing and anchor,-
stiffness on the' stress induced in the pipe.
RESPONSE: Before proposing a parametric study it~is important to determine the parameters, the basis of the values used, and the other conservatism that exist in the analysis which tend to over predict the level off stress in the pipe.
Soil Spring Constant: The soil spring constant used in the analysis is based on the stiff structural fill under the pipe.
In reality-there is a thick layer of compressible saprolite which exists under the structural fill. This layer, to a large extent, reduces the soil spring constant.
The use of stiffer spring constants lead to more conservative results for this loading condition in the analysis.
Since the entire settlement input is at the anchor point representing the Service Building, the stiffer soil spring constant used in the analysis will predict a conservative stress level in the pipe.
A coefficient of vertical subgrade reaction of 300 tons /cu.ft.-was used for the encased section, and a coefficient of-subgrade reaction of 100 tons /cu.ft. was used for the unencased section of the pipe in the analysis even though a lower value can be justified for use.
Intuitively it can be justified that a lower value of spring constant will produce lower stress in the pipe.
However, an assessment of this effect wil: be the subject of the r
proposed parametric study.
i 101-JST-27165-16
m.
< x Node Point Spacing: The. node point spacing was carefully selected su'ch that the continuum could closely be represented by a number of discrete members and also the continuous soil supports could be represented by a discrete number of soil springs without significantly affecting the structural behavior.
Analytical method applicable for beams on an elastic foundation were used as a basis for selecting node-spacing. The node point spacings used in the analysis are significantly less than that is theoretically required to produce a reasonable result.
Therefore the stress generated in the pipe will not be sensitive to node point spacings closer than those used in the analysis. However, an assessment of this effect will be a subject of the proposed parametric study.
Anchor Stiffness: Transnational stiffness of 10E+8 lbs./in. and rotational stiffness of 10E+10 in.lbs/ rad. were used in the mathematical model for L e purpose of analysis. These values are several orders of magnitude higher than the stiffness of members and therefore produce realistic estimates of stress in the pipe. The values are consistent with the generic anchor stiffness used in the design of other piping systems.
Actual stiffness of the anchor i
points are of the same order of magnitude or lower.
As far as this analysis is concerned, the stiffness and settlement are counter acting 1.e., if stiffness at a point is large the deflection is i
expected to be small, if the displacement at the point is large it should be associated with a smaller value of stiffness.
While performing an analysis for a larger value of settlement to assess stress in the pipe, the use of an anchor stiffness greater than the 101-JST-2716S-17
ry
', y.L jkMp.
-U 1
nx II actual. stiffness tends to be doubly conservative. ' However f an L
assessment'of sensitivity of.thel pipe stress to an arbitrary
~
11ncrease of transnational ' stiffness at the wall will be.the subject-
' of. the' proposed: parametric; study.
Based on the.above' discussions it is clear that realistic:and.
. conservative parameters in terms of anchor; stiffness, sci 11 spring.
s'tiffness,'and node point spacings were used in.the analysis to determine' stress 'due to. settlement in the service water piping >
buried between the Service Building and; Unit 2 Main Steam Valve House.. The magnitude of secondary stress reported in the analysis'
~
represents only a one time accumulation of self limiting strain in
. the pipe and is still within the code allowable.
In addition, becau'se of the highly ductile nature of the pipe material, there.
exists an extremely large margin against a failure being caused by.
the loading of this nature.
g.
1 To study the: sensitivity of some of the parameters discussed above, the following ' parametric study is proposed:
Analysis will be performed to assess effects of increese of soil stiffness by 20% and decrease of soil stiffness by 20% to study.the effects of'the soil stiffness on the stress in pipe.
r.
" Analysis will be performed to assess the effects of'further reduction of node point spacing to 2.5 ft. or less on the stress in pipe.
,101-JST-2716S-18 g
_n_____
7--,
.,=.
,.p r
Analysis will be performed to essess the effect of increasing and decreasing the transnational anchor stiffness at the wall points by two to ten times.
1, 101-JST-2716S-19
lJ I
i, n
i I
s i ;
f eW nb i
i fl E z8 W'
rer r/
v.
\\ igm -
i y
-ili
- 4X i!
jf f
WE s
p A'
/
T st-
- 7.,,
5' j
e s-
- R' ws-
/
r E'
z/c -sY e
1ly; W'
iI,
t f
t 1
l
}tt(tt 7
., ^g t
.}'
p' cr-i t
t I
g!
p 1
3' E
I 4
, /^
~.
A t x,1].g
/
i.Il g'
- il
[&,e, t r g '7-,,
.f O
_I
,f;,
l 1
AM I
/,
t> -
j
+t-4 A
^
.,~
E j\\
.iS:t ).p 2-r 'l l
t.
/
3'p l ll \\
T_ Jj 4
~-
n' R
/
- 7 u
.T s
{
T 3
g M
~.
,,.,Y' I
1J/4 GN
.g1g r
l t
. ~ _ _ -
,= '
E NU t
lEi i I
i
.g
,l 5
C -
)
1 I
liJ Es W 1.;u_
+
b I
'5 v i
or E i
. g S
Et A:
su d y
/o f
re h I-Do cM O.
'.W g i
,i \\,R!
L ac/
u).
os E' l
3 i
.H_i-7J'5 a.
cW a
2 Y
1 7
a 4
AuA t
/
c
, E csV w
gf,
_o, /
m 7 c
kT i
t j
E s.
t 2 w G
E I
t I
yI R.
, q.
c E,
Sl 1
I t
(it r
- s. p s E,
Sii Lo g
M-ET W r
4 s
i_
A E
3 g
. Et-7J/
M E
i l
G c
t
,; o P
l i-i
~. e g/
I W
. T-7 1rtq1.
7 I
/
c :__
(.
I H
.f I
7 li, a..
.,: +
I
. 2 7
3' E
I 1
u i
l elilL c:
l.
li, a.
G rI V,'
G<
l iiii gt I
S Q,a i
q l.
G,,
i -
i'.
l e
,. T i*
~Ng, i;
' i
.t
'i'
.,ji::
l i!I l
i
,Ii ll[
.H, 1!
l
- t j
.;:. i ',,.
l Fgu
- _L a
C M
n z
s v
t e
el-r m
. 4
' :r w
~
~
~
,r w
s h4m W.:.. M 3, w
% h.=
w
.....A,,
!c m
[.,:,_
r m) -
m
,e f o. :}::-
,k c.
c
- y.. :
g. : 5, t
u v
- o a
{k*.g;.:.-
/.
sH _
r,t ur n
i
/
si rim a.-
[.y ' :
ca
_~
g wW s
i
- )-
a
), --; g-
'sN,
,a a
- . &g. --
w@ y a
2 2
. ; s-n
[
(1 ls a
s E
wW w -
- o
- .m, R
- m
- :n ;r. -
's.
[,
mp eE g
U r
o, 's.
v:
s g
-. ;c4 -
G r
n,
- j IU g
l
.{...:
g
- i s
/
FS 1
..3...
2-
.f."
\\
- 1.,m ;. :
- .m i
R..
t A..
.i -
+
1 T.:.
'/
ec-
. f. :-
w2.j.:
r-r
'n.k
= -M %
a, /
o c7 im.
o s
s2
~..
2 y::.
)s:7 l-..
e t
ns e
y.
u d6 s
wn..
y
, g.
e e-n u
r5
- ^ m :...
o/
.o o
s7
=
s s.
c.
w f1 1
'...@ t s
m.
o s.
)
rh d e Ak e c
.....m
&k n
i m
i :.
e e
~. G..... %
.G S
.g P
-.ew :
s~
s c.
K..
l s
i s
\\
s e
- .:2 e,
I 1
e l' :- -:.
c M
S*
d
- . : : "t. ;
C S
g
! t W.
a.
~
r'm_
- f i [,1m o
o n
o w
m t
g S
o o
y z
r v
)q '
nd o
ll
- ,E ;
d
,,,.~
=
.e x
. w/
L
/
4=_,I.N.,,i
/'
- =
- =
- , =
/
=
=
.P
= --
r
/
(fw.
n.
I i
n
.9
.9
.e u
,.'A
.W 3A
'n.
e ER S.
ta
.l
/"
.s RU
.t
.# g.f.s Wc
.a m
,a g"I1 US a
m.
6 ts G
'.///-
o c
=
C.
I F
/
- . wW F.
$.f..
s f
a
/
-/
'sm/
t s,
'/
m.
s _
E' e
l
.p-a
/
/
/
i v/
t
. = " "."
i-
/
- s
../
s.
x! =./.
se.f
/.
t.
%. e l rf n.
n9
.S "v =,. t l
,,l
.9
- e i.mY.p.. = "
..W j
sm a
t n 7.,. e.
s o
- m. x.
c l,
- t. '
. :=E
?..
f f.. /' /
a *E ?.
a e=rE"e.
T.
ul?
- =. e J
V
- : J" =
.I v,A T. v. f:E
' i m/.
/
.r
'. g',a' /.=
e
_ p=
y, 'a /=
il l
l I
a e
=
s i
/l a
=u
'l [,
/
cm. /
w j
w j
=
m
~
. =
=
,gIyI
,y,
- ,. 4 5-I);.'
.[ g, -
2 t
g.
5 s
1
'i.
./
ATTACHMENT 3 t
l 101-JST-2716S-1
3,.
t 3e
~,I 4'
7 I-
=
~
d
.2;
{
j
?
+
\\
^
N t
1
.p-l l
4*~
F T-
- c.
N 1
C C
C
^
S 3
2 0
g 0
9 0
0 o
0 0
g O
2 3
4 5
e 7
8 1
D D
D 0
o D
D g
D 0
n D
D I
b~A 5ta4b o
t ii
0 j
i:
9 2
9 1
h SI I
ERS II 9
UT 8
I 9
TN CU 1
U I
k RN TO 8
SI T 8
I A
9 S T
?
1 S S k
A 1.
, f LR i.
7 CE 8
W 9
FO 1
OP k
TA NN 6
I Al 9
A lI E
1 LH T
k T N I
RI s
I s
5 LOO 8
SNP
?
9 1
q h
i 48 9
1 k
1 3
8 9
1 t.
k y-2 89 1
k E
8 1
+
I',
9 1
k f
. }.
0 E
G-8 T
M.
9 A
1 D
i:
?
k 9
7
+
9 1
h 4
87 9
E 1
T i
A t
k C
IDN tl i
7 I
l 79 SR 1
k$
ET k
B N M E I
UM 6
NE 7
V n
IY 9
E O W
1 W
.l
. y-k TD A R x
G A 5
EV 7
NR 9
E U 1
T k
C L
C t
4 3
2 O
0 0
0 0
0 0
0 0
2 4
5 6
8 I
D D
D D
D 0
D D
D D
D 1
5La 5ydhm 1j!l
k d
1 k
w' t
k k
- 4
.1 k
1 F
l i~-
E-j; E:
=
1;
/
j
- q H
tij:
j
}
h E
~
i E
i i:
Ey [
i
- x.
b M
i r
.i
.E
- k c
C K
2 O
C 0
0 0
0 O
O gD 3
S 4
O 2
4 5
6
?
B I
g D
D D
D I
D 0
D 0
D D
gnt A $ 5yhmg au i
7
~
'4' y
f6 a.
iii i
p
- 2 4i 5
m 1
[
i L
p:t
^
5 Y
t 3
d f
1+
5 1
- d E
l9E I
C C
C 4
3 2
O o
0 0
0 O
0 0
o O
0 0
I 2
3 4
S 6
7 8
9 0
D D
D D
D D
D D
D 0
D 0
D I
, bgg 5Whw fL l
k t
u k
.~
d P
~
o t
- r h
2 I.
. u 0
C C'
i C
L C
7 6
S 4
3 2
0 0
0 0
O 0
gO 2
3 4
S 5
1 D
C.
D D
D D
0 ID D
D D
D 0
Qgt j
$ k 4$
i I
.. H x.
1
[
- )
e k
t C
C "C
C S
4 3
2 o
g 0
0 0
0 0
0 0
o O
2 3
4 5
6 7
8 l
D D
D D
g o
D D
D D
D D
D D
I
,b uk Ntu4b t
T s
ij g
l i
t
~
o '
~
i j
d y
4 i
i ji 3i.
l'
-1 E
p
+
i
+,
+:
4
.x s
o l'
M i
n r,
c a
L i
l
.v
~
,a o,
1.
c A, 1.
+
=
i E
e 3
i E
1j i
l v}
i t
1 i
f gO O
0 0
0 0
0 0
g 0
2 4
6 8
0 0
0 0
0 0
2 6
g D
B D
D D
1 J
1 1
1 2
2
,4 2
0 2
4 6
6
,I !TJ '! =t LRk4 m
J 7l ll
llllgllllI ll 0
j4 iN 9
2 L
9 W
1 SI S_
k E
RSR l -
- j~
9 UTO
[
8 T IF N
9 C U T 1
U N
k RNI T OO SI J 8
T I
8 AN 9
STO 1
SSI S k
ALhW
'7 C EP i
8 WX 9
FOE OP-1 k
TA NN15 6
EN M 8
MA S 11 9
E 1
LH T k
I T N RI I
5 LOO 8
SNP 9
1 k
489
,g 1
g k
38 R.
9 1
i k
3 Y
2 8
g!
9 1
k 1
w~
8 9
~
1 k
d 0
E 8
T
. }
! p
. Ii 9
A 1
D 1
k y
9 yI J
7
?
9 1
T:
u o
k
'i9 i
,\\
8 7
, m 9
1 T
k 7
. t 7
s 9
1Li 1
1i
- M k
l!
l!*
I
{!f 6
j!
. 1 l
9 7
i 1
k 57 i
9 1
k O
0 0
0 0
0 g
2 4
6 8
0 0
0 0
0 0
2 0
0 0
2 4
6 0
2 4
6 8
o D
D 0
D 1
1 1
1 1
2 2
2 2
kwf $4$Nbto
~
rU
'.w lll ll i