ML20084F023
| ML20084F023 | |
| Person / Time | |
|---|---|
| Site: | Hope Creek  |
| Issue date: | 04/24/1984 |
| From: | Mittl R Public Service Enterprise Group |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8405030087 | |
| Download: ML20084F023 (22) | |
Text
O PS G Company Pubhc Service Elecinc and Gas 80 Park Plaza, Newark, NJ 07101/ 201430 8217 MAILING ADDRESS / P.O. Box 570, Newark, NJ 07101 Robert L. Mitti General Manager Nuclear Assurance and Regulation April 24, 1984 Director of Nuclear Reactor Regulation U.S.
Nuclear Regulatory Commission 7920 Norfolk Avenue Bethesda, MD 20814 Attention:
Mr. Albert Schwencer, Chief Licensing Branch 2 Division of Licensing Gentlemen:
NRC REVIEW OF STRUCTURAL /GEOTECHNICAL TOPICS HOPE CREEK GENERATING STATION DOCKET NO. 50-354 Pursuant to the agreements reached at the meetings held on January 10, 11, and 12, 1984,.to review HCGS structural /
geotechnical topics with the NRC, attached -is one-(1) set of
-responses to those items denoted as-Category:III-target.
date.
A listing of the attached Category _III target date items, broken down by date of meeting, is as follows:
Meeting of January 10', 1984:
' Items A.5, A.8, and.A.13
-Meeting of_ January 11, 1984:
Items _A.4, A.5,'A.14, and.A.16 Meeting.of January 12, 1984:
Item A.4
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iThe Energy People 954912 (4M) 7-83 '
Director of Nuclear Reactor Regulation 2
4/24/84
'In addition, please note that four (4) advanced sets of these. responses were transmitted to D. Wagner via Federal Express on April 23, 1984.
'Should you have any questions-in this regard, do not hesi-tate to contact us..
Very truly yours,
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Attachment:
Resolution of NRC Comments on Structural /Geotechnical Topics C J D. H. Wagner'(w/ attach.-)
USNRC-Licensing Project Manager Mr.
W..H.
Bateman USNRC Senior ResidentfInspector-A.
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en 13 840 2 62 6 60 Response to NRC Audit Mee ting Date:
Ja nua ry 10, 1984 Question No.:
A.5 QUESTION:
Verify that soil shear moduli variation of + 50 per-cent is at least one standard deviation based on soil test data.
RESPONSE
Dynamic properties of the soils used in the analyses are based on both geophysical survey and laboratory testing (FSAR Section 2.5.4.2.4).
The laboratory data from strain controlled cyclic triaxial tests and resonant column tests for Vincentown, Hornerstown and basal sand deposits are plotted (Shear strain versus K2) ae shown on Figure 1.
The factor K2 is the coefficient in the Seed and Idriss equation for shear moc"los at low shear strains:
G(PSF) = 1000 x K X(Tm}
2
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where a is the Mean Confining Stress m
to these data is shown by the solid A mean curve line in Figure 1.
Standard deviation was computed separately for strain controlled cyclic triaxial test data and resonant column test data.. Limits for one standard deviation are shown by dotted lines.
Figure ~1 also shows the design curve used in dynamic analyses and the range of soil shear moduli-variation of + 50 percent.
The seismic induced ef fective shear strains are typically in the range of 10-3 to 10-4 in/in.
Comparison of the curves indicates that.the soil shear moduli variation of + 50 percent envelopes the standard deviation curves at seismic induced strain levels.
The soil shear moduli variation of + 50 percent, therefore, includes the variation in Taboratory data in the area ofuinterest.
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APR 13 '840 2 6 2 C 6 C Response to NRC Audit Meeting Dat e :
Ja nua ry 10, 1984 Question No.:
A.8 QUESTION:
Lab test shear modulus values for Vincentown dif fer from values used in the analysis.
Investigate-the impact of the use of lab test values on soil structure interaction.
RESPONSE
The design curve (FSAR Fig. 2.5-41) recommended - for the Vincentown sands for use in the soil structure interaction analysis was derived from laboratory tests which included resonant column tests and dynamic strain-controlled cyclic triaxial tests and field geophysical surveys.
For many soils, especially the variably cemented Vincentown sands, the major short-coming of all laboratory tests for dete rmining the chcar modulus lies in the fact that undisturbed samples are difficult to obtain and test.
In general, the greater the degree of sample disturbance, the lower.the shear modulus.
On the other hand, field tests, such as geophysical tests, do not suf fer from this sample disturbance limitation and, the re fore,
provide more reliable data at low strains:
1.e.,
10-6, For strain values observed in the soil-structure inter-action analysis results, the effect of the laboratory test data variation was evaluated by varying the design shear modulus curve +50%.
This 50% shear modulus variation envelopes one standard deviation based on soil laboratory test data for strain levels observed l
in the soil-structure interaction analysis results (See response to Question No. A.5, NRC Structural Audit Meeting Date January 10, 1984).
The re fore, the ef fect of the use of laboratory test values on soil-structure i
interaction has been taken into' account in the design basis analysis.
AFR 13 '84 i) 2 6 2 6 6 0 i
Response to tiRC Audit Meeting Date:
Ja nua ry 10, 1984 Question No.:
A.13 QUESTION:
Provide comparison of Bechtel Independent Verification results with The Design Basis Results.
RESPONSE
A response to the above question will be provided in July 1984.
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APR 13 '84 0 2 6 2 ti 6 0 Response to NRC Audit Meeting Date:
Janua ry 11, 1984 Question No.:
A.4 QUESTION:
Current settlement calculations for the service water pipe are based on average soil propertie s.
Provide additional settlement estimates using actual soil properties at various sections along length of service water pipe line.
RESPONSE
SETTLEMENT ESTIMATES Settlements of the service water pipeline were estimated using average soil properties and a typical construction For the load-time history shown on Figure 1, sequence.
the maximum total static settlement of the pipeline is estimated to be approxlmately 3, inches corresponding to a 30 foot thick. Kirkwood clay layer.
The settlements would be less for. a smaller thickness of Kirkwood clay.
Dif ferential settlements would primarily depend on the This variability of the Kirkwood clay layer thickness.
variability however will be negligible within each 20 segment of the pipeline, except near the power block foot area where the pipeline crosses: the main excavation slope.
The maximum dif ferential settlement within a pipe segment is expected to be on the order of 1 inch in that area.
1 SETTLEMENT MEASUREMENTS Settlements of the service water pipeline were measured for the fo rme r Uni t 2. pi pe by. c ompa ring inve rt elevations of the
- pipe segments from the as-built data with those from an optical survey pe rformed in March 1984.
Unit 1 pipes were not readily accessible.
Because of the proximity of the Unit 1 and 2 pipes, actual settlements of _ the Unit'l pipes -should be similar to
.those measured for the Unit 2 pipes.
The alignment of_the
- pipeline and locations. of field measurements of settlements
- are shown on Figure 2.
The measured settlements are' shown :on i
Figure 3.
The measured maximum static settlement and maximum di f ferential _ settlement between the pipe joints _are 2.28 inch and 0.6 inch, res pe ct ively.
It-should be noted that t he' i
location of the measured maximum total: settlement isJin the area of maximum Kirkwood clay thickness along the pipeline.
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Settlements in other_ parts of the pipeline, therefore, are ex-pe cted - to be smal le r.
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AFR 13 '84 0 2 6 2 6 6 0 PREDICTED FUTURE SETTLEMENTS AND CONCLUSIONS Af ter decommissioning of the dewatering system, groundwater a t the HCGS site had been slowly brought back to its original natural level as of December 1983.
This has an unloading ef fect on the soils, resulting in reduction of the effective stresses.
Future movement of the pipeline, if a ny, is ex-pected to be small and in the upward direction.
The measured settlements are, therefore, considered to be representative of the maximum settlements experienced by the pipeline in the respective areas.
Comparison of the measured and estimated settlements indicates that the average soil properties used in
- settlement calculations are appropriate.
The structural integrity and flexibility of the joints of the service water pipes were verified by testing.
The pipe joints have been qualified for 1 inch axial displacement and 1 degree rotation (corresponding to 4 inches of allowable dif ferential settlement along each 20 foot section) based on the test re-sults.
These tolerance values exceed the predicted static plus dynamic dif ferential settlement and provide an adequate margin of safety.
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APR 13 '84 0 2 6 2 6 6 0 Res po nse to NRC Audit Meeting Date:
January 11, 1984 Question No.:
A.5 QUESTION:
The response to FSAR question 241.29 should include information on gantry crane piles (including pile tip elevations ) and cof ferdam configuration adjacent to intake structure.
Provide design summary for Cof ferdam stability during seismic events without cons ide ri ng liquefaction of soils.
RES PONSE :
The Service Water Intake Structure gantry crane sup port consists of six pile supported foundations.
These foundations are independent of the cellular cofferdams.
Each foundation contains ten-14 inch diame'ter by 3/8 inch wall concrete filled pipe piles.
The piles are driven to refusal for a 100 ton pile with tip elevation generally varying between elevation 0 feet to 20 feet.
All piles are protected by a cathodic protection system.
A design summary for cof ferdam stability during an SSE event without considering liquefaction of soil is attached.
The cof ferdam configuration adjacent to the intake structure is shown in the design summary, i
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APR 13 '84 0 2 6 2 6 6 0 HCGS DESIGN
SUMMARY
4/84 CELLULAR COFFERDAM STABILITY ANALYSES I.
Overview Load conbinations, key assumptions, and summary of safety f actors for the cof ferdam stability analyses are presented.
Figures 1 and 2 show the cof ferdam and surrounding area.
II.
Load Combinations The following load combinations are evaluated for the cof ferdam stability analyses to verify that the structural acceptance criteria, as represented by the corresponding minimum factors of safety for each load combination, are satisfied:
Minimum Factors of Safety Load Combination i
Failure Mode D+H+E D + H + Es o
I Sliding 1.5 1.1 Overturning 1.5 1.1 Centerline Shear 1.5 1.1
' Bursting Pressure 4.0 4.0 t
The load'combinatio'n D+H+E controls the~ f actor of safety s
I of the stability calculations.
Figure 3 summarizes all of the loads.
.III.
Key Assumptions f
Key-assumptions for ' the stability-- check during ~ an SSE event.are as -follows:
- a.- Soil layers and properties are b'ased ' on information
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discussed in Section 2.5 of HCGS -FSAR.
b.: ' The horizontal camponent' of-the SSE case is -assumed -
to be 0.2 g and the vertical' component is assumed to be 40 percent of thel peak acceleration in 'the : upward direction Leoncurrent with horizontal peak acceleration.
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(Cont'd) c.
The saturation line inside and landward side of the cof ferdam is assumed to be the same as the mean water level (el. 89' ), therefore, the hydrostatic ef fects cancel each other.
d.
The grouted (or concreted) portion (el. 62' to + 7 7 ' )
of the fill inside the cofferdam is capable of -
withstanding a shear stress of 1.1 jfe' or 70 psi.
IV.
summary of Safety Factors for Stability Checks The factors of safety are shown on Table 1.
All calculated safety f actors for the stability checks exceed the minimum sa fe ty factors specified by Section II.
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APP.13 '84 0 2 6 2 6 6 0 ITosign Summary Page 3 TABLE 1
SUMMARY
OF RESULTS FOR STABILITY CHECKS Controlling Calculated Stability Check Against Load Combination Factor of Safety Sliding D+H+E 1.3
> 1.1 min.
s Ove rturning D+H+E 1.14 > 1.1 min.
s Centerline Shear D+H+E 1.8 4 > 1.1 min.
s Bursting Pressure D+H+E 4.6
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i SHEET PILE WATER FRONT RETAINING STRUCTURE
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2 FIGURE 1
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APR 13 '84 0 2 6 2 6 6 0 Response to NRC Audit Meeting Date:
Ja nua ry 11, 1984 Question No.:
A.14 QUESTION:
Assess and justify that the current soil modeling for the intake structure adequately accounts for:
Soil property variability along the depth Sheet piling Layering of soil including inclined layering
RESPONSE
A response to the above question will be provided in July 1984.
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1 Response to NRC Audit Meeting Date:
Ja nua ry 11, 1984 Question No.:
A.16 QUESTION:
Perform an independent seismic verification analysis (impedance analysis) for the intake structure and i
compare the results with design basis results.
Con-sider the ef fe cts of side bounda ries, embedme nt and the presence of v.tter masses in the analysis.
RESPONSE
A response to the above question will be provided in July 1984.
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APR 13 '84 0 2 6 2 6 6 0 Response to NRC Audit Meeting Date:
Janua ry 12, 1984 Que stion No. :
A.4 QUESTION:
Review the seismic design of all Seismic Category I tanks to dete rmine whether the flexibility of the tank wall _and the water mass within the tank were co ns ide red.
For those tanks where these ef fects have not been considered, assess the impact of including these e f fe ct s.
RESPONSE
All Seismic Category I tanks were reviewed to determine whether the flexibility of the tank wall and the water mass within the tank were considered.
Review has indi-cated that in all tanks, except the diesel fuel oil storage tank, fluid mass and tank wall flexibility are addressed adequately.
In the case of the diesel fuel oil storage tank, an analysis to qualify the tank to in-clude the ef fe ct of fluid mass and tank wall flexibility is in progress.
_