ML20209C541
| ML20209C541 | |
| Person / Time | |
|---|---|
| Site: | Satsop |
| Issue date: | 11/02/1983 |
| From: | Lear G Office of Nuclear Reactor Regulation |
| To: | Novak T Office of Nuclear Reactor Regulation |
| References | |
| CON-WNP-1466 NUDOCS 8311100175 | |
| Download: ML20209C541 (32) | |
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[SGEBReading Docket No. 50-508 MEMORANDUM FOR: Thomas Novak, Assistant Director for Licensing Division of Licensing ,
THRU: James P. Knight Assistant Director for Components and Structures Engineering Division of Engineering FROM: George Lear, Chief Structural and Geotechnical Engineering Branch Division of Engineering
SUBJECT:
DRAFT SER INPUT - GE0 TECHNICAL ENGINEERING Plant Name: WPPSS Nuclear Project No. 3 Licensing Stage: OL Docket Number: 50-508 Responsible Branch: LB-3, A. Vietti, LPM We have reviewed Sections 2.5.4, 2.5.5 and 2.5.6 of the WPPSS Nuclear Project No. 3 (WNP-3) FSAR through Amendment No. 3 dated April 1,1983 provided by Washington Public Power Supply System (WPPSS) in support of their application for an operating license. Additional geotechnical infomation was reviewed by the staff during our audit of applicant's calculations on September 26 -
30, 1983. On the basis of this review and the Applicant's responses to our previous questions, we have prepared the enclosed draft geotechnical engineering input to the Safety Evaluation Report.
In the enclosed draft, we have identified a number of unresolved open and/or confimatory items.* The applicant should be requested to address these issues and provide additional infomation and/or analysis results to resolve these issues before the final SER is due to DL. These items are sumarized as follows:
(1) In the FSAR Table 2.5-16, the applicant has listed a range of Poisson's ratio values of'0.35 to 0.5 for fresh sandstone, and has used these values in analysis of some of the plant structures. We find this range of values for Poisson's ratio of rock-like fresh sandstone to be too high for the in situ materials.
- We expect that most of these items will be closed by the time the final SER is issued. Detemination as to whether any remaining items are open or confi m *- - U 11 ha mada at the ttme of Final SER issuance.
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l The applicant should either provide further substantiation for using I this range of values or use more realistic values for analysis.
(SERpara 2.5.4.1.3.1 page 5).
(2) For fresh and weathered sandstone materials, the applicant should provide. (a) the steps used in statistical analyses to arrive at the representative compressive strengths and design elastic moduli including assumptions and the results of analyses. (b) the values of (Vo)j and the computed values of (RF) along with the method of deriving vaTues of (Vp)f and (V computed values of desSg)i 6 compressiveused instrengths, these computations, and design elastic and (c) the modult. (SERpara 2.5.4.1.3.2.page8).
(3) The applicant should explain the comparative methods used to arrive at Poisson's ratio for fresh and weathered sandstone using results of laboratory compression tests on. selected core specimens and justify use of the method in selecting design values. (SERpara 2.5.4.1.3.2 page9).
(4) The applicant should justify and provide further bases for the assumptions in arriving at a value of 500 lb/inJ for the modulus of subgrade reaction of fresh sandstone (used in NASTRM analysis of Reactor Auxiliary Building mat). (SERpara 2.5.4.1.3.2.page9).
(5) In view of wide variation exhibited by test results presented in FSAR Appendix 2.50. Table 2.5-15 and 2.5-16. the applicant should justify selection of S000 ft/sec and 3200 ft/sec for shear wave velocities of fresh and weatherad sandstone, respectively and explain his reasons for using the same shear velocity of 3500 ft/sec for the two materials in his analyses. (SERpara 2.5.4.1.3.2.page10).
(6) The applicant should provide further bases for selection of the shear modulus and damping ratio versus strain curves for fresh and weathered sadstones, used in soil-structure interaction analysis. (SERpara 2.5.4.1.3.2.page11).
(7) The applicant has c.ounitted, in response to staff question 241.22 to provide all the forthcoming Category I field density and mo sture content test results on Class Al structural fill as construction progresses. We will review and evaluate this infomation when provided by the applicant. (SERpara2.5.4.2,page15).
(8) The deconelution procedure, through 570 ft of sandstone, used by the applicant in detemining the response of rock to seismic loading is not acceptable to the staff because the input motion would not be substantially al ered by the fim rock. The applicant should illustrate the adequacy of his analysis results by using an alternate approach. (SERpara 2.5.4.3.page17).
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l (9) The applicant should provide the procedure and assumptions used in computing the dynamic bearing capacity for Category I structures and the bases for deriving the rock parameters used in the ar.alyses. This information should be supplemented by the bases for the dynamic loads {
used in the analysis. (SERpara2.5.4.4.page18).
(10) The applicant should amend FSAR 5ection 2.5.4.11.7 and/or Response to Staff Question 241.3 to make the static and dynamic bearing capacity infonnation consistent, for the Reactor Auxiliary Building. (SER para 2.5.4.4.,page18).
(11) The applicant has not provided procedures, assumptions and results of static and dynamic bearing capacity calculations for the following seismic Catagory I structures Dry Cooling Tower Train D Structure.
Two Diesel Oil Starage Tank Enclosure Structures and Category I Drainage Manholes. The Table attached to the appilcant's respense -
to staff question 241.3 should be amended to include inforsution on all seismic Category I structures. (EER para 2.5 4.4. page 17).
(12) During the audit on September 26 - 30, 1983, the staff found that, in :
the NASTRAPI computer program input for the soil-structura interaction !
analysis of the Reactor Auxiliary Building (RA9), a value of Poisson's rstio of 0.5385 was used. This is inconsistent with the design ,
parameters shown on Table 2.5-16 cf the FSAR. Mereover, a value of Poisson's ratio greater than 0.5 is not theoretically possible. The '
applicant should provide . justification of this issue and assess the ;
impact on analysis. (SEEpara2.5.4.4.page17).
(13) The appitcant has not acnitored settlement of any seismic Category I ,
structure. The staff does not agree with the applicant that the .
post-construction settlements for rock supported structures need nnt bo ,
considered in design; since the applicant estimated these settlanants to be close to 1/2 inch, we must he assured that a minimum of one-half inch differential settlement has been incorporated in the design of -
piping running between rock supported structuros. The integrity of '
i piping and duct run penetrations should be reassessed for a minimum of one4alf inch differential settlement and the rtsults of these l confirmatory analysis should be provided for staff review. (SERpara 2.5.4.4.page22).
(14) The applicant should provide for staff review, cruiparisons of the distribution of static and dynamic lateral earth pressures on walls for the two methods of analyses (finite-element, and Seed and Whitman).
l (SERpara2.5.4.4.page24).
- Other than the open and confirmatory items indicated above, the staff ffr.ds l
that the applicant's design and construction criteria for WNP-3 for the plant I foundations meet the requirements of Appendix A to 10 CFR 100.
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This review has been perfomed by Dr. Dinesh C. Gupta, Geotechnical Ingineering Section. Structural and Geotechnical Engineering Branch.
George Lear. Chief Structural and Geotechnical Engineering Branch Division of Engineering
Enclosure:
As stated ec: w/o enclosure R. Vollmer J. Knight G. Lear R. Jackson P. Kuo L. Reiter -
w/ enclosure G. Knighton L. Heller A. Vietti
- 0. Rothberg J. Kimball D. Gupta
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Pl. ant Name: Supply System Nuclear Project No. 3 (WNP-3)
Docket Number: 50-508
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Subject:
Draft Safety Evaluation Report, Geotechnical Engineering Prepared by: Dinesh C. Gupta, Structural and Geotechnical Engineering Branch, Division of Engineering, ONRR The following sections summarize the staff's geotechnical engineering review of the WNP-3 plant as described in the Final Safety Analysis Report (FSAR) through Amendment Number 3 dated April 1, 1983. Thet stability of subsurface
- materials (FSAR Section 2.5.4) and the stability ofslopes(FSARSection2.5.5)havebeenevaluatedinaccordancewith the criteria outlined in Appendix A of 10 CFR 100, Regulatory Guide 1.70, Revision 3andtheStandardReviewPlan(NUREG-0800)datedJuly, i 1981. There are no embankments or dams (SRP Section 2.5.6) associated with the plant. -
2.5.4 Stability of Subsurface Materials'and Foundations 2.5.4.1 Site Conditions i
2.5.4.1.1 General Plant Description The WNP-3 plant site is located on a ridge at the northern edge of Willapa Hills, in the southeastern portion of Grays Harbor County in the 4
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State of Washington. The site 1s approximately 16 miles east of Aberdeen and approximately three miles south of the town of Satsop.
Prior to the ' start or % plant construction, the ridge at the plant location was at an elevation of approximately 480 feet above mean sea level. During early construction, the general plant grade was excavated to an elevation of approximately 390 ft.
The common foundation mat for the WNP-3 reactor building and reactor auxiliary building is supported on essentially fresh sandstone at an elevation of approximately 326 ft. All other Seismic Category I structures are founded at plant grade on weathered sandstone. These structures include UHS Dry Cooling Tower Train A and Train B, Dry Cooling Tower Control Building, Condensate and Refueling Water Storage Tank Enclosure, two Diesel Oil Storage Tank Enclosures and Manholes for the gravity drainage system. About 1000 ft northeast of the powerblock there is a cooling tower which is used for normal cooling operations.
It is not a seismic Category I structure. The ultimate heat sink function for kNP-3 plant is performed by two dry cooling towers; no makeup water is required for safety-related cooling of the plant.
There are permanent natural slopes in the north-south direction arid men-made exc4vation slopes in the east-west direction whose failure could affect the safe ,peration of the plant. The natural rock slope south of the power block dips at an average slope of 3 horizontal to 1 vertical (3:1), with a maximum slope of 1-1/2:1. The crest of the natural slope is more than 250 ft from the edge of the powerblock. The man-nade rock slope east of the powerblock is about 180 ft high, rising
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at an average slope of 4-1/2:1, with a maximum slope of 3:1.
the toe of the slope to the east is more than 350 ft from the edge of the dry cooling towers.
2.5.4.1.2 Subsurface Investigations The subsurface investigation program at the site consisted of drilling and trenching, A total of 95 borings were drilled at the site and soil and rock samples were r'ecovered. Most of the borings were drilled with mud and tricone bit. Rcck cores were obtained by using NX double tube coring barrels and diamond bits. Core recovery and rock quality designation (RQD) were recorded. Piezometers were installed in 52 boreholes after completion of the drilling. In addition, 65 trenches of various lengths and depths were excavated. .
The geophysical investigations consisted of seismic refraction surveys and cross-hole shear wave velocity measurements. The geophysical surveys show good spatial correlation with the test boring results.
2.5.4.1.3 Subsurface Materials 2.5.4.1.3.1 Investigation of Subsurface Materials Properties The plant area is underlain by Astoria Formation, a sandstone in various degrees of alteration including residual soil, weathered sandstone, fresh (unweathered) sandstone and tuff. This formation also contains L_
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4 some siltstone strata and several tuff beds. Fresh sandstone is differentiated.from weathered sandstone on the basis of color change.
Fresh sandstone is light to dark gray, and weathered sandstone is yellowish-brown from the oxidation of iron minerals in the sandstone.
Joints in sandstone show two dominant trends; one set ranges in strike from N34*E to N65'E and dips generally from 50'-70* SE and the second set strikes about d43'W and dips nearly vertical. The general spacing of joints within a joint set is approximately 1 to 5 ft and the distance between joint sets is 40 to 100 ft.
During construction all residual soils and most of the tuff were excavated from the plant area, and the plant grade was established at elevatien 390 feet above mean sea level on the exposed weathered sandstone surface. At the locat' ion of WNP-3 site, the weathered sandstone extends to a depth ranging from 40 to 60 ft below final plant grade level and is underlain by fresh sandstone. A 7 to_11 ft thick tuff bed exists in the vicinity of the northern edge of.the plant location at O'to 15 ft below the finished plant grade.' The general subsurface profiles under the plant location are shown on FSAR Figures 2.5-72, 2.5-75 and 2.5-76. '
yThe Reactor Buildings and Reactor Auxiliary Buildings are founded on a common mat over essentially fresh sandstone at Elevation 326. Based on subsurface exploration.rasults (RQD values ranging from 90'to 100% and core recovery of 85 to 100%) the applicant has concluded and the staff
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concurs that there are no zones of alteration or irregular weathering or -
zones of structural weakness below Elevation 326.
The unconfined compression strengths of intact fresh sandstone core samples range from 300 psi to 850 psi. The test values showed tangent modulus values at 50% ultimate strength for this material to range from 5 5 1 x 10 to 2.5 x 10 psi. The strength and compressibility results for fresh sandstone are listed in Table 2.5-16 of the FSAR. We find these test results to be gene' rally inconsistent with the higher values reported in the literature (e.g., Foundation Engineering Handbook by Winterkorn and Fang) for sandstone. However, since these values result in conservative analyses, we find them to be acceptable. The applicant has, also, listed on Table 2.5-16 and used in his analysis of some structures, Poisson's ratio value of 0.35 to 0.50 for fresh sandstone.
We find this value of Poisson's ratio for rock material to be too high.
The applicant should either provide further substantiation of his reasons for using this range of values or use an appropriate value of Poisson's ratio in his analysis.
The permeability of the fresh sandstone was determined by means of in-situ packer tests in two borings. In addition, field falling head and rising head permeability tests were conducted. The test results generally agreed with the in-situ packer test results. The highest
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permeability recorded in fresh sandstone was 7.5 x 10-6 cm/sec. We find this value of permeability for fresh sandstone to be reasonable.
The applicant determined the dynamic properties of the fresh sandstone from laboratory sonic velocity measurements and from field seismic refraction surveys and cross-hole shear-wave velocity measurements. The P-wave velocity vaiues recorded ranged from about'6000 to 8000 ft/sec, and the S-wave velocity values ranged from about 2500 to 4000 ft/sec, These results are shown on Table 2.5-16 of the FSAR. The staff finds these results to be reasonable and acceptable.
The foundations of Category I structures other than the Reactor Building ,
and the Reactor Auxiliary Building are founded at or slightly below grade level (El. 390) and rest on weathered sandstone. The weathered i
sandstone has low to moderate hardness and is found by the applicant not to have any zones of structural weakness at the location of the plant site (as evidenced by core recovery of 85 to 100 percent and.RQD of 90 to 100 percent). .
The results of strength and compressibility tests on weathered sandstone are sununarized in Table 2.5-15 of the FSAR. The unconfined compression strength of test samples are shown to range from 350 to 800 psi and the tangent modulus values at 50% ultimate strength range from 2.5 x 105 to 5
7.0 x 10 psi. We. find these test results to be inconsistent with those reported in the. literature. However, since the values result in conservative analyses, we find them to be acceptable. The field permeability tests indicate that the highest permeability coefficient recorded for weathered sandstone is 7.5 x 10-6 cm/sec which is the i
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same as for the fresh sandstone. We find these permeability test results to be reasonable and acceptable.
The dynamic properties for weathered sandstone were investigated by the applicant through field seismic refraction surveys and cross hole testing. These tests were supplemented by laboratory sonic velocity measurements on representative weathered sandstone samples. The field and laboratory dynamic test results are given in Table 2.5-15 of the FSAR. The results indicate that the P-wave velocity values range from about 5000 to 9000 ft/sec, and the S-wave velocity values for weathered sandstone range from about 2,300 to 4,000 ft/sec. We find these values to be reasonable..
The tuff beds below plant g' rads 'are composed of. coarse to fine grained material and are about 7 to 11 ft thick. Based on strength testing, the applicant determined that the relative hardness and engineering properties of the tuff do not differ significantly from those of the fresh sandstone. The applicant also did not find any evidence of bedding planes between the tuff layers and the sandstone.
2.5.4.1.3.2 Design Values of Subsurface Materials Fresh and Weathered Sandstone In Section 2.5.4.11 of the WNP-3 FSAR, the applicant has stated that representative values of compressive strengths of the fresh and i
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weathered sandstone cores were based on the statistical method using results of the laboratory compression tests; however, the details of the method are not given. The applicant has also s'tated that he used reduction factors (RF) to arrive at the design compressive strengths for the two materials. Although the procedure to compute the RF value is briefly described, the computed values of (RF) and the corresponding final design values of the compressive strength are not given. In view of the wide variation in the results of the test data shown in Tables 2.5-15 and 2.5-16, the staff requires the applicant to provide, (i) the various steps used in statistical analyses to arrive at the representative compressive strengths along with assumptions and the results of the analyses, (ii) the values of (V );pand the computed values of (RF) along with the method of deriving values of (Vp)f and (Vp )) in these computations, and (iii) the computed values of design compressive strengths.
The applicant stated in the FSAR that a statistical method was used to calculate values of the representative tangent moduli from unconfined ccmpression test results on selected core specimens; however, the details of these analyses are not given. Reduction factors (RF),
similar to those used in computing the design compressive strengths were used to compute the design elastic moduli. Again, the details are not given and the procedures are not justified. The staff requires that the applicant explain in detail the statistical analyses, justify the bases for assumptions and provide the results of analyses. The computed
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valuesofdesignelastik:moduliforfreshandweatheredsandstone materials should also be presented.
In describing the procedure for arriving at the design values for Poisson's ratio, the applicant has stated in the FSAR that the values were " selected based on the comparative method using results of laboratory compression tests on selected core specimens". The staff requires the applicant to provide details of the so called ' comparative method' and to justify'this method's use in selecting design Poisson's ratio values for the frash and weathered sandstone materials. Although the range is given, the applicant should document and justify the values of the design Poisson's ratio used for these materials in the various
. plant designs and analyses.
In response to staff questions 241.10 and 241.23, the applicant stated that a selected value of modulus of subgrade reaction of 500 lb/in3was used in the static analysis (using MSC/NASTRAN computer program) for the Tank Enclosure Structure. In analytically deriving 'the value of this modulus of subgrade reaction the applicant used a shear modulus value of 330 ksi corresponding to strain value of 10-2 in./in. in his dynamic shear modulus versus strain curve. Further, the expression used for modulus determination is indirectly derived from an equation given by Barkan for vibratory loads and for the purpose of machine foundations design. We find that the applicant's use of the subject equation, the assumptions made in utilizing the equation and the resulting value of
- the modulus used in MSC/NASTRAN need further justification.
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The applicant has selected design permeability values of 2 x 10-6 cm/sec and.6 x 10-6 cm/sec for fresh and weathered sandstone materials, respectively. These values are very close to the maximum recorded permeability measurements in the field and laboratory for these materials and, therefore, are reasonable and acceptable values to be used in design and analysis.
Dynamic shear wave velocities of 3,800 ft/sec for the fresh sandstone and 3,200 ft/sec for the weathered sandstone have been selected by the applicant to be used in the design and analysis of the plant. Little or no explanation is given in the FSAR in support of the selection of the values. In view of the wide variation, exhibited by test results, in the values of S-wave velocity data presented in FSAR Appendix 2.5 D, Tables 2.5-15 and 2.5-16, the applicant needs to further justify the use of these values for design.
The applicant performed one strain-controlled cyclic triaxial test to establish the design values and shape of shear modulus versus strain curve for fresh sandstone. To account for end effects and non-uniform strains within the test specimen, the average axial strain was obtained by dividing the measured axial strain by a correction factor of 4.
Values of shear modulus were obtained at four different strain levels.
Damping ratio for fresh sandstone was calculated for one strain level of 3 x 10-2 . Based on the results of measurements and interpretation of the test data, the applicant found that the shape of the shear modulus versus strain curve is different and steeper than the published curves for rock (e.g., Schnabel et al. 1972) and the calculated damping at 3 x
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10-2 strain is also higher than corresponding values in the published curves. We find the applicant has not provided bases for selecting a damping ratio versus strain curve and has not sufficiently justified deviations from the published dynamic properties of fresh sandstone.
Moreover, the applicant's results are based on only one dynamic test on fresh sandstone. Only a few different strain values were used to measure the shear modulus and damping. The correction factors used to divide the measured axial strain have not been properly justified. For these reasons, applican't needs to provide further bases for selecting the shear modulus and damping ratio versus strain curves shown in Figures 2.5.121 and 2.5-122 of the FSAR.
. For the weathered sandstone material, the applicant has' used the same '
dynamic shear modulus versus strain curve as for the fresh sandstone; however, no explanation for this assumption is provided. A curve for weathered sandstone damping ratio versus' strain is not given. The applicant should justify the design curves for dynamic properties of weathered sandstone and provide the bases for assumptions used in deriving the design curves.
Tuff Beds Since the relative hardness and engineering properties of the tuff beds below grade were found by the applicant to be similar to those of the weathered sandstone, the static and dynamic design values for the tuff were selected as identical to those of the weathered sandstone. We find this assumption to be reasonable and acceptable.
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Residual Soils Although all residual soils were excavated from underneath the location of the plant structures, their engineering properties were established by the applicant for use in the evaluation of stability of man-made slopes east of the WNP-3 plant structures.
Based on interpretation of laboratory test results of seventeen ~
unconsolidated-undrained triaxial tests, six consolidated-undrained triaxial tests and three unconfined compression tests, the applicant established three sets of strength parameters for the residual soils:
maximumstrengthparametersofc=1000 psf,y=40',minimumstrength parameters of c = 750 psf, jf = 26 and average strength parameters of -
c=1000 psf,JI=30*. The applicant used all three sets in slope stability evaluation. Weconsiderthedesignc.andgvaluesfor residual soils used by the applicant in analyses to be reasonable and the approach of using an apprcpriate variation of soil properties in the -
slope stability analyses to be acceptable.
2.5.4.1.4 Groundwater Conditions The pre-construction groundwater conditions at the site were determined using borehole piezometer readings taken from April 1973 to September 1974 during the subsurface exploration. At that time, the groundwater
- levels in the WNP-3 powerblock area ranged from El 385 ft to El 411 ft.
During construction, the plant level was excavated to an elevation of 390 ft and the bottom of the common mat foundation was excavated to an
- 13 approximate elevation of 326 ft. For this situation the temporary
- groundwater flows from relatively impermeabTe sandstone (permeability coefficient of approximately 2 x 10-6 cm/sec) were handled with a drainage system within the common mat excavation. Groundwater collected was drained from the excavation through a gravity ficw to the slope south of the plant location. The groundwater conditions were monitored from October 1977 to December 1979 using piezometers around the WNP-3 excavation; the recorded levels during this period ranged from El 330 ft to 390 ft as shown on ISAR Figure 3.4.1-5.
The plant, has a permanently lowered watertable level to an elevation below the foundation mat level (below 326 ft) along the exterior faces of the category structures by means of a gravity drainage system. The drainage system is not Category 'I, as the walls.and the mat of the Reactor Auxiliary Building are designed to withstand full hydrostatic loads (water table at El 365) that may be caused by a complete blockage of the dr'ainage system.
The staff's evaluation of groundwater is presented in Section 2.4 of this SER.
2.5.4.2 Excavation and Backfill All residual soil was excavated from the plant area. The excavation into rock for the powerblock area extended cbout 64 ft below the final grade level (390 ft above mean sea level). It penetrated the overlying weathered sandstone for a depth of about 60 ft and exposed the fresh
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sandstone surface at elevation 326 ft. Vertical cuts were made in sands. tone fonnations. The vertical rock sides were cleaned by air jetting and protected against weathering by shortereting over welded wire fabric. The bottom of excavation was covered by concrete mud mat.
The Category I structures other than the powerblock structures are located slightly below plant grade on weathered sandstone. All cuts for these structures were vertical. No backfill was required beneath or around seismic Category I structures since they were placed directly against fresh or weathered sandstone.
Class Al Structural Fill, consisting of a well graded sand and gravel having a maximum size of 6 inches and a maximum of 15 percent passing the number 200 sieve, was used t'o backfill beneath, around and above .
seismic Category I buried pipe. When used as a bedding material for the pipes, backfill with the maximum particle size of 3/4 inch was used.
In the FSAR Section 2.5.4.2.6, the applicant has stated that the Class Al structural fill was compacted to a specification of at least 95 percent of the maximum modified Proctor density (ASTM 1557-78). The in-place density tests were performed in each lift. The results indicated that less than 10 percent of 't he tested densities fell below 90 percent of the specified density. The staff finds these as-placed densities of the Class Al structural fill beneath, around and above seismic Category I buried piping to be reasonable and acceptable.
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In response to the staff question 241.22, the applicant has stated that -
- there are other areas (including areas under and adjacent to Diesel Generator Fuel Oil Storage and Transfer System, and Class IE Duct Lines from Reactor Auxiliary Building to Dry Cooling Tower and Refueling Water Storage Tank Area) where placement of Class I structural fill has not been completed. The applicant has comitted to provide for staff review the results of all Category I field density and moisture content tests performed under and adjacent to safety related structures as construction progresses'. We find this comitment to be acceptable. The staff will review and evaluate the information when provided by the applicant.
. The applicant used soil-cement (concrete sand mixed with 10 percent Type II Portland cement and 10.4% 2% moisture) conipacted to a specification of 95 percent Standard Proctor Density (ASTM D558-57) as a backfill in the construction access ramps adjacent to the Reactor Auxiliary Building. In these areas the in-place density test results showed almost 100% compliance with the specified compaction requirement. We find these results to be acceptable.
2.5.4.3 Response of Rock to Seismic Loading In Sections 2.5.2 and 2.5.4.7 of the WNP-3 FSAR, the applicant has stated that since the shear wave velocities in the underlying sandstone at the plant site is greater than 3000 ft/sec, there will be no amplification or modification of the input acceleration time histories at the plant site and the design earthquake would be defined by Regulatory Guide 1.60 response spectra anchored to the maximum design
, i ground acceleration (0.32 9 ) at the site. We concur with the applicant's -
l assessment, given in FSAR Section 2.5.4.7,that the response of rock to seismic loading would not result in a modification of the input motion and find it acceptable. However, in Sections 3.7 of the same FSAR, the applicant stated that he used a deconvolution analysis through 570 ft of rock column which resulted in a substantial modification of the design motion and resulted in base slab response spectra lower than R.G.1.60 spectra in frequency range of interest. Thus, the information presented in the Section 3.7 of the FSAR is inconsistent with the information presented in Section 2.5.4.7. The procedure given in FSAR Section 3.7 for evaluating response of rock to seismic loading is not acceptable to the staff because input motion would not be substantially altered within the firm rock surrounding structures.
In response to staff questions 241.9 and 241.24, the applicant informed the staff that the depth of rock for deconvolution was based on the results of a sensitivity stu.dy in which the depth of rock column was gradually increased to determine the lower boundary of the analytical model until no difference in response of the building could be detected.
However, the analytical parameters and the results of this study have not been provided to the staff for review. During an audit of the applicant's calculations on September 26 to September 30, 1983, the staff was verbally informed by the applicant's A/E (Ebasco) that the calculations and results pertaining to the said sensitivity study were not saved by the applicant's A/E.
BasedonareviewoftheinforEationprovidedintheFSARSections 2.5.2, 2.5.4.7 and 3.7, the applicant's response to our Q's and our audit findings, we conclude that the procedure used by the applicant in determining the response of the rock using deconvolution through 570 ft rock column is not acceptable. An assessment of the results of its application to structural seismic design and analyses is presented in Section 3.7 of this SER.
During the audit on Sep'tember 26 - 30, 1983, the staff found that, in the NASTRAN computer program input for the soil-structure interaction analysis of the Reactor Auxiliary Building (RAB), a value of Poisson's ratio of 0.5385 was used. This is inconsistent with the design parameters shown on Table 2.5-16 of the FSAR. Moreover, a value of Poisson's ratio greater than 0.5 is not theoretically possible. The applicant should provide justification of this issue and assess the impact on analysis.
2.5.4.4 Foundation Stability ,
The Category I structures on a comon mat (Reactor Building and Reactor Auxiliary Building / Fuel Handling Building) are supported on firm, fresh sandstone at a depth of 64 ft below finished plant grade (El 390 ft).
The foundations for other Category I Structures (Refueling Water Storage and Condensate Storage Tank Enclosure Structure, Dry Cooling Tower Train A Structure and Control Building, Dry Cooling Tower Train B Structure, and Two Diesel Oil storage Tank Enclosures) rest on weathered sandstone slightly below El 390. The Category I buried pipelines are located on
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Class Al structural fill overlying either sandstone or soil-cement .
underlain by sandstone.
t Bearing Capacity In FSAR Section 2.5.4.10.1, the applicant has stated that Tertaghi's bearing capacity formula (Modified for rock) was used to compute the ;
ultimate bearing cipacities for the Category I foundation mat. We find this state-of-the-art procedure to be acceptable for static bearing capacity calculations. However, the applicant has not provided any [
information about the procedure and assumptions for dynamic bearing ,
capacity calculations. The staff requires this information along with the bases for arriving at the dynamic loads used in these analyses. ;
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For the Reactor Auxiliary Building mat foundation static bearing capacity calculations, the applicant neglected the effect of cohesion and used a rupture angle of 20'. We find these rock properties assumptions to be reasonable and acceptable. In view of the foundatica being supported on firm fresh sandstone 64 ft below grade, sufficient '
l margin of safety against bearing capacity failure exists. However, we find that applicant's calculation results given in the FSAR Section 2.5.4.11.7 are inconsistent with those given in response to staff Question 241.3; the minimum factor of safety in the FSAR is stated to be 34, whereas it is stated to be 6.3 in response to Question 241.3. The applicant needs to appropriately amend his submittals to make them consistent and correct. The applicant should also provide for staff
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review, adequata information on the methods, assumptions and results of .
dynamic bearing capacity calculations.
, The applicant has provided the results of static bearing capacity calculations for the Condensate / Refueling Water Tank foundation and Dry Cooling Tower and Control Building Foundation in response to staff Question 241.3. The values.given for the factors of safety of the two buildings are 20.0 and 23.8, respectively, which we find to be adequate.
However, for these comp'utations, as well as for the dynamic bearing capacity calculations, the applicant has not provided the procedure and the rock properties used in the analysis. We require the applicant to provide the necessary details of the procedures used for static and dynamic bearing capacity calculations and the assumptions made in these analyses for staff review. -
The applicant has not provided any information on the static and dynamic bearing capacity calculation procedures, assumptions and results of analyses for the following seismic Category I structures: Dry Cooling Tower Train B Struct0re, Two Diesel Oil Storage Tank Enclosure Structures and Category I Drainage Manholes. The necessary bearing capacity calculation results for these structures along with the procedures and assumptions should be provided for staff review.
The attached Table 1, provided by the applicant in response to staff question 241.3, shows pertinent details of static and dynamic loads on three seismic Category I structures. The staff requires the applicant 4.--., -- ,
TABLE 1 . .
Category I Foundation Foundation Description of Foundation Allowable Factor of Structure Dimensions Elevations Foundation Base Loading Bearing Safety .
(As-Built) (MSL) and Depth to Capacity -
Fresh Sandstone- Static . Dynamic Static Dynamic Static Dynamic
=
cendensate/ 171'-0 x 66'-0 Top El 390.00 5'- 0 Thick Hat 2.5 6.0 50.0 50.0 20.0 8.3 Refueling on Weathered -
Water Tank Sandstone 40' to Foundation Fresh Sandstone ,
Dry Cooling 85'-0 x 272'-0 Top El 390.00' 4'-0 Thick Hat 2.1 4.6 50.0 50.0 23.8 10.5 Tower & on Weathered Control Bldg. Sandstone 35' to ,
Fresh Sanditone ,
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t Shield Bldg. 298'-0 x 310'-0 Top El 315.00' 9'-0 Thick Mat 13.6 17.7 85.0 85.0 6.3 4.8 Containment, located in Int. Fresh Sandstone Structure, Fuel llandling Bldg. on Common Mat s
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to modify this table to make it consistent with the information provided -
in the FSAR. In addition, the applicant should include information on othei seismic Category I structures to complete this Table, and submit the amended Table for staff review.
Settlement In response to staff question 241.4, the applicant informed us that, since all seismic Category I structures were founded directly on either fresh or weathered sand' stone, settlement or rebound was not considered by the applicant to be a factor in the design of the plant. The applicant did not and does not have any settlement monitoring or the plant foundations. Also, no information has been submitted for staff review on the potential or actual differential settlements between plant foundations and buried piping or duct run penetrations. .
Using Boussinesq equation, the applicant'has computed the value of estimated post-construction total settlement of the Reactor Auxiliary Building mat to be less than half inch. However, allowable settlements are not given in the FSAR. The applicant has also not provided for staff review estimated and allowable settlement values for other seismic Category I structures.
We do not agree with the applicant that construction and post-l construction settlements for rock supported structures need not be considered in the design of structures, piping, and duct run penetrations because the stresses induceo due to differential i
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settlements may be significant. We require the applicant to provide for .
staff review the values of allowable differential settlements that the
' Category I buildings can withstand (in combination with other appropriate loads) and still meet code allowable stresses of the FSAR.
In addition, since the applicant is not monitoring the actual total and differential settlements between various Category I foundations, he should assume a minimum of one-half inch differential settlement to check the design of piping running between rock supported structures.
Piping and duct run penetrations should also be assessed for a minimum of one-half inch differential settlement. The results of these confirmatory analyses should be provided for staff review.
Lateral Pressures The exterior walls of the Category I structures were placed directly .
against the vertically excavated rock face. The applicant computed the static lateral pressures resulting from (a) hydrostatic pressure due to possible failure of the groundwater drainage system around Category I structure (b) long term creep of sandstone causing active lateral pressures on exterior walls, and (c) the effect of the adjacent building surcharge at the ground surface causing lateral pressure on embedded walls. The applicant has stated in the FSAR that the Category I structure walls are designed for full hydrostatic pressure up to an elevation of 365 feet, incorporating a coefficient of active earth pressure of 0.22, corresponding to $ = 40', and using Boussinesq stress distribution to evaluate the effect of surcharge on the embedded exterior walls. We find these computational procedures and assumptions
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staff Question No. 241.17 that total static lateral pressure was .
determined to be 2 kips /ft2 . The applicant has, however, not provided the distribution of static lateral pressure along the depth of the walls. We require that the applicant submit this information for review.
The applicant computed the dynamic lateral pressure based on the effects of rock-structure interaction analysis. The dynamic lateral pressure obtained from this analysis and used in design was 10.27 kips /ft2 ; the distribution of this pressure with depth of wall was not provided by the applicant for review. This information is needed to complete our SER.
As stated earlier in Section 2.5.4.3 of this SER, it is the staff's position that the modification of rock response due to deconvolution is not acceptable. Since the applicant used this procedure to compute seismic lateral earth pressures, the staff requested the applicant (Question 241.18) to re-compute these pressures without using deconvolution and by utilizing the state-of-the-art Seed and Whitman (1976) approach. The applicant has responded to this question (informally received by the staff on September 23,1983). The applicant's computations using the Seed and Whitman approach and incorporating the effect of static lateral pressure, hydrostatic pressure and effect of surcharge load show the total dynamic lateral pressures tc be 4.7 kips /ft2 , This value is less than one-half of the valte used by the applicant in the design. These computation results
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are reasonable and acceptable to the staff. The applicant should, ,
however, provide a compariscn of the dynamic 1ateral pressure ,
distribution along the depe of the seirmic Category I walls using the above mentioned two approacnes (rock-interaction analysis and Seed and Whitman procedure) for staff review.
3 Liquefaction Potential There is no potential for liquefaction of sandstone that supports structures, systems and components. The compacted Class Al backfill placed under, around and over the seismic Category I buried piping is well graded, has a maximum particle size of 6 inches and has been compacted to 95 percent modified Proctor density. The soil cement backfill placed at the location of the construction ramps (at 95%
Standard Proctor density) has unconfined compressive strength of approximately 600 lb/in2 , which is similar to that of the sandstone.
The applicant has not considered the liquefaction potential of Class Al structural fill or the soil cement backfill. We consider this approach to be reasonable, because as a result of the high compaction and compressive strength of these materials they can be considered to be not susceptible to liquefaction.
2.5.4.5 Conclusion Based on the applicant's design criteria and construction reports and on the results of the applicant's site investigations, laboratory and field tests, and analysis, the staff has concluded that the site and plant
. foundations will be adequate to safely support the WPPSS Nuclear Project c
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No. 3 (WNP-3) in accordance with the requirements of Appendix A to 10 .
CFR Part 100, pending satisfactory resolution of the open and confirmatory items identified above.
2.5.5 Stability of Slopes The WNP-3 plant site is surrounded by natural rock slopes gently dipping to the south of the plant and cut rock slopes rising to the east of the ,
site.
The natural rock slope to the south of the plant has an average slope away from the plant of 3 horizontal:1 vertical with a maximum slope of 1.5H:1V. . The crest of the slope is more than 250 ft away from the edge of the powerblock structures. A typical cross-section through the slope is shown on FSAR Figure 2.5-110. The material forming the slope essentially consists of weathered and fresh sandstone. The presence of a thin bed (<t.10 ft) of residual soil near the toe of the slope was neglected by the applicant in the stability analysis of the. natural slopes.
Typical cross-sections analyzed for stability analyses of cut rock slopes east of the plant are shown on FSAP. figures 2.5-111 and 2.5-112.
The slope generally rises at an average slope of 4.5H:1V with maximum slope of 3:5H:1V. The toe of the slope is more than 350 ft away from the edge of the Category I structures. The slope consists of weathered sandstone and residual soil.
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As evidenced by the results of the tite exploration, the applicant has determined that the sandstone at the plant site is massive, without continuous joints, seems or layers of weaker material. The applicant determined the static strength parameters of the weathered and fresh sandstone on the basis of 13 uniaxial compression tests. Based on these test results, a cohesion of 23 kips /ft 2and an angle of internal friction of 0 were selected for analyses.
We find these rock strength parameters to be reasonable and acceptable.
Shear strength parameters for residual soil to be used in stability l P
analyses of cut slopes were obtained from seventeen unconsolidated-undrained triaxial tests, six consolidated-undrained triaxial tests and three unconfined compression tests. Based on these test results, the applicant selected the following properties for. residual soil:
cohesion, e angle of internal friction, p high 1000 lb/ft 2 40 U
2 0 average 1000 lb/ft 30 -
2 low 750 lb/ft 26 -
We consider the applicant's use of these residual soil properties to be reasonable and acceptable.
Natural Slope The static stability of the natural rock slope has been investigated by the applicant using the Simplified Bishop Method of Slices and the
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Sliding Wedge Method of Analysis. Two different groundwater conditions, viz., (i) normal groundwater level elevation of 320 ft (with drainage system operating) and (ii) groundwater level elevation of 365 feet (with drainage system blocked), are considered. The result of the applicant's analyses indicate that the natural slope has a minimum factor of safety of 5.5 for Slip Circle Method of Analysis and minimum factor of 7.6 for the Sliding Wedge Method of Analysis. Based on these results, the staff concludes that for static design loads, the natural slope south of the plant is stable.
The applicant has made a seismic stability evaluation of the natural slope for SSE condition using Slip Circle and Sliding Wedge analysis approaches. In these analyses, a horizontal seismic coefficient of 0.32 and a vertical seismic coefficient of 0.22 were.used. The applicant's results for these analyses indicate minimum factors of safety of 2.0 for Slip Circle and 2.64 for dynamic Wedge Pethod of Analysis. We consider that the margin of safety is adequate and acceptable.
Cut Slopes The applicant has analyzed the cut rock slopes east of the plant structures using Bishop's Slip Circle Method and the Sliding Wedge Method of analysis for static and dynamic cases. Two cross-sections shown on FSAR figures 2.5-111 and 2.5-112 have been analyzed. For seismic stability analyses, a seismic coefficient corresponding to 0.32 horizontal and 0.22 vertical were used for SSE.
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The following minimum factors of safety were computed by the Applicant from these analyses of cut slopes:
Factor of Safety Method of Analysis Static Case Dynamic Case Slip Circle 3.36 1.45 Wedge Method ' 3.13 1.40 We find these factors of safety for stability of cut rock slopes to be acceptable.
The staff concludes that the natural and man-made slopes around the plant site have been analyzed by the applicant'in an appropriate and reasonable manner,and, based on 'the results of analyses presented by the applicant, the staff concludes these slopes have an adequate margin of safety, and meet the requirements of 10 CFR 100. The natural and cut slopes are, therefore, acceptable.
2.5.6 Embankments and Dams There are no embankments or dams associated with the WNP-3 plant used ,
for plant flood protection or for impounding cooling water required for operation of the plant.
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/ p o .
i, NOV 1 1983 IEORAr:DUti F0P.: Thomas H. Novak, Assistant Director for Licensing, DL -
FROM: James P. Knight, Assistant Director for Components & Structures Engineering, DE
SUBJECT:
DRAFT SAFETY EVALUATION REPORT - GEOLOGY AND SEISM 0 LOGY - WASHINGTON flVCLEAR PLANT PROJECT NO. 3 Plant Name: Washington Nuclear Plant - Project No. 3 Docket Number: 50-508 Licensing Stage: OL Review Responsible Branch: Licensing Branch No. 3 Responsible Project Manager: A. Vietti Enclosed are the geology and seismology sections for the UNP-3 draft SER. This input applies to the SRP sections 2.5.1, 2.5.2 and 2.5.3.
The report was p.repared by Richard Mcitullen, Geologist and Jeff Kimball, Seismologist.
As stated in the attached draft SER, there are a number of open items (staff questions) which fall into two broad categories. First is the possibility of a large or great earthquake on the subduction zone beneath the site. Second is the possibility of unrecognized low angle thrust faults in the site vicinity that could cause large close - in earthouakes or surface faulting at the site. We anticipate that when these significant issues are addressed, that new information may require the reinterpretation of some previous positions of the staff, the USGS, and the applicant.
Except for the above discussed open items, the staff reaffims its ennelusions stated in the SER-CP that the~ applicant has adequately investigated and characterized the seismic and geologic hazards at the site, and with respect to those hazards, the site is acceptable.
OrignalslW B311140111 CF 83110 ADOCK 05000508 James P. Knight, Assistant Director for CF Components & Structures Engineering Division of Engineering
Enclosure:
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