ML20031B134
| ML20031B134 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 09/18/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20031B133 | List: |
| References | |
| NUDOCS 8109300215 | |
| Download: ML20031B134 (9) | |
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Dw l Round One Questions and Positions, GES
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South Texas Project Docket flo. 50-498 i
l 241.1 The measured settlecent data given in Appendi,x 2.5.C c.f the South (2.5.C.4)
RSP Texas Project FSAR is provided only uo to June 1979.
Provide time vs. settlement plots of up-to-date settlement data obtained for all category I structures where settlements are being monitored.
Tabulate values of the ceasured caximum differential settlements and show comoarisons of the ceasured data with anticioated settlements assumed in the analysis of these structures and their appurtenances, and evaluate the imoact of any differences between the ceasured and anticipated settlecents on the design and construction of these structures and appurtenances.
Staff re::uires that the settlement of safety related structures and appurtenances be monitored for a period of at least five years af ter the issuance of the operating license and the impact of observed settlement, if any, on the design limits of category I structures be evaluated periodically.
(6 months, 2 years and 5 years after OL issuance).
241.2 The data used for evaluating the perfor ance of foundations of (2.5.C) category I structures given in "FSAR Appendix 2.5.C - Geotechnical Monitoring" has been updated only up to June 1979.
Please update this instrumentation information and evaluate its impact on the expected performance and stabi?ity of foundations of. all category I facility structures. Also indicate, using tabular form, how much
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l settlament of the structures has occurred since the conn'ections between s.uctures and safety-related utilities were made.
Evaluate the effect of the cast and anticicate future settlement of structures on safety related utilities and cc.inections.
241.3 In Section 3.8.5
" Foundations and Concrete Supports", you indicate (3.8.5.1) that a cathodic protection system is olanned for corrosion protection of the embedded foundation reinforcing steel and liner plate.
Provide l
details of this cathodic protection plan for staff review.
Include a discussion of the procedures for inscection for corrosion and design measures to minimize the potential for corrosion.
241.4 For Category I structures other than the containment, you indicate that (3.8.5.5) a factor of safety of 1.1 has been used for checking the overturning and sliding of the structures against service and r.onservice loads.
Verify that, for the load combinations given in Section II.3 of NRC Standard Review Plan Section 3.8. 5 - Foundations, you meet the acceptance criteria for minicum factors of safety against sliding and overturning given in Section II.5 of this SP.P for all category I structures. Verify that, for determining the overturning moment due to seismic loads, the three components of the earthquake were combined in accordance with methods given in Standard Review Plan 3.7.2.
Describe and present your analyses to show that the soil bearing and shear strength margins are conservative under these load ccabinations.
241.5 In Section 2.5.5 of the South Texas Project Safety Evaluation (2.5.6)
RSp Report dated August 1975, it is stated that the staff will recuire periodic monitoring of leakage from the emergency cooling pend to assure that an adequate supply of water will be available for emergency conditions. He require that you make a commitment in the FSAR to comply with this staff position. Also, provide the following inforr.ation:
(i) assumptions, analytical model, permeability voiues of the soils and the method of analysis used for estimating the magnitude and rate of potential seepage loss through the pond.
(ii) the extent, location and classification of all pervious sand or silt lenses encountered along the perimeter and bottom of the pond during the pond excavation.
(iii) the procedure and results of any field permeability tests perfcrmed to evaluate the magnitude and rate of seepage loss through the pond.
(iv) details of the procedure to be used for periodic r.onitoring of the leakage from the emergency cooling pond and your proposed technical specification for plant operation.
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241.6 You have not provided sufficient information for staff review regarding Category I buried piping and electrical duct banks.
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provide the following information using Regulatory Guide 1.70 Standard Format and Content of Safety Analysis Reports in FSAR l
Sections 1.7, 3.5, 3.6, 3.7.3 and 3.8.4.
t (i) two cooies of large-scale drawings (approximately 22 in x 34 in) showing category I piping and duct bank locations and routing, conn:: tion details at structures, bends, anchors, essent * >l appurtenances, and typical cross-sections showing the details of bedding and cover material used in construction.
Details may be shown on separate drawings.
(ii) barrier design features and procedures used to resist the missile hazard to buried pipes and conduits.
Identify the protective structures and bar. iers on plant arrangement and elevation drawings.
(iii) provide R.G.1.70 information about protection of systems or components against dynamic effects associated with postulated rupture of buried piping, if applicable to your plant design, and discuss effects of soil erosion due to buried pipe rupture.
(iv) provide appropriate references used by you as bases for your discussion in FSAR Section 3.7.3.12, regardir.g seismic resca.ase of buried piping, and provide justification for the assumptions made therein.
Provide details of the procedure used, piping sections analyzed and results of axial and
, bending stresses in buried pipes, bends and pip'e penetrations.
Provide your criteria for tolerable stress limits and factors of safety.
Provide s1milar information for category I electrical duct banks.
(v)
Provide the information required by Regulatory Guide 1.70 to be given in Section 3.8.4 of the FSAR for category I buried piping and electr{ cal duct banks.
Include the procedure used to obtain the design loads, the analysis cross-sections, the values of soil parameters used in the analyses, the bases of obtaining the soil properties, the acceptance criteria, the results of analyses, the factors of safety and details of program for testing and inservice inspection of. buried piping and duct banks.
241.7 The value of the coefficient of carth pressure at rest for compacted (2.5.4.10.5.2) backfill around structures used by you for design purposes is not appropriate for these conditions.
Provide a justification for using such a low valve and provide appropriate references.
Describe any e
conservatism involved in your ~ earth pressure cocoutations.
Provide
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plots of earth pressure vs. death used to design subsurface. walls of various category I structures.
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ENCLOSURE 2 STRUCTURAL ENGINEERING BRANCH POSITION ON RESCLUTION OF SOUTH TEXAS SSI ISSUE In the meeting of August 7,1981 on SSI of South Texas Project, after having explained the technical basis for the SEB SSI related position and discussed with the applicant on South Texas SSI issues, the Structural Engineering Branch recannends that Hcuston Lighting and Power Company use the following approach to meet the intent of the SEB SSI position and believes that this will be acceptable:
Use Elastic Half Space Method of Analysis without reducing the inout motion due to embedment of structure in soil.
Apply the Regulatory Guide 1.60 motion properly anchored at the OBE/SSE "g" values in the free field at the foundation level and compare the resulting response spectra with those of Finite Element Method. The applicant should demonstrate that at least the intent of the following position is fully met:
Methods for implementing the soil structure interaction analysis should include both the half space and finite element approaches.
Category I structures, systems and components should be designed to responses obtianed by any one of the following methods:
(a)
Envelop the results of both EHS and FEM; (b)
Results of one method with conservative design considerations of effects from use of the other method; and (c) Combination of (a) and (b) with provisions of adequate conservatism in design.
The above mentioned comparison of floor response spectra needs to be done only for key structures at key levels e.g., 6 key levels of reactor conta' ament building, 4 key levels of auxiliary building etc.
2 The SEB staff mentioned that if the actu l design floor response spectra a
are compared with those obtained by enveloping the spectra resulting from the FEM and EHS methods of analysis, there may not be any appreciable change in the design of structural elements, because HL & P and Brown &
Root have mentioned that enough conservatism is already built in the design by using Finite Element Method.
However, there may be cases where the components and equipments may not meet the seismic criteria based upon the enveloped response spectra.
HL & P may need to look into these cases and study the specific impact of NRC's current position on the cases in order to qualify them for the seismic criteria.
If the floor response spectra obtained by enveloping are higher than those used for actual design, HL & P still has a choice to justify that the additional stresses resulting from the enveloped spectra are acceptable and overall design adequacy is maintained by considering the actual as-built-strength of the structure.
For concrete structures, the as-built-strength will be the average of the comoressive strength, established by tests.
For both reinforcing and structural steel, the as-built yield strength will be the average of the actual tested yield strength, but in no case shall it be greater than 70% of the ultimate strength. The scope and the extent of test program and resulting test data shall be submitted for review and approval by the staff.
Other approaches for demonstrating the seismic design adequacy of Category I structures and systems which meet the intent of this position are alto acceptable if reviewed and accepted by the staff.
For example if enough seismic data for the South Texas site and other sites having similar regional and local seismicity characteristics are available, then the site specific spectra approacn may be a viable option to be considered.
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