ML20235Z693

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Final Rept of Adequacy of Structural Criteria for San Onofre Nuclear Generating Station Units 2 & 3
ML20235Z693
Person / Time
Site: San Onofre  Southern California Edison icon.png
Issue date: 07/06/1972
From: Hall W, Newmark N
NATHAN M. NEWMARK CONSULTING ENGINEERING SERVICES
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ML20235X376 List: ... further results
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FOIA-87-462 NUDOCS 8710210265
Download: ML20235Z693 (9)
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FINAL REPORT TO AEC REGULATORY STAFF ADEQUACY OF THE STRUCTURAL CRITERIA FOR SAN ONOFRE NUCLEAR GENERATING STATION UNITS 2 AND 3 Southern California Edison Company San Diego Gas and Electric Company AEC Docket Nos. 50-361 and 50-362 by N. M. Newmark and W. J. Ha l l 6 July 1972 8710210265 8710i4 b

AD Bh-462 PDR

l ADEQUACY OF THE SD1UCTURAL CRITERIA FOR SAN ONOFRE NUCLEAR GENERATING STATION UNITS 2 AND 3 I

Southern California Edison Company and San Diego Gas and Electric Company by N. M. Newma r k and W. J. Ha l l INTRODUCTION This report is concerned with the adequacy of the containment structures and components for a 2-unit nuclea r power station, San Onof re Units 2 and 3, for which appilcation for a construction permit has been made to the U.S. Atomic Energy Comntssion by the Southern California Ealson Company and the San Diego Gas and Electric Company.

The facility is located on the west coast of Southern California on the Pac!fic Ocean In San Diego County, approximately 62 miles southeast of Los Angeles and approximately 51 miles northwest of San Diego.

This report Is based on Information and criteria set forth in the Preliminary Safety Analysis Report (PSAR) and amendments thereto, as listed at the end of this report. Also, we have participated in discussions with the AEC Regulatory Staff concerning the design of this unit.

The two units will be constructed on the existing San Onof re site and will be located immediately south of San Onof re Unit 1.

DESCRIPTION OF FACILITY The San Onof re Units 2 and 3 will each consist of nuclear steam supply systems (NSSS) with an associated pressurized water reactor t hat will operate at core power levels up to 3390 MWt.

The core and the NSSS design are similar to that of Hutchinson Island Unit 1, and the reactor coolant system 1s quite similar to that for Palisades Unit 1.

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2 The reactor containment structure, which houses the reactor and steam generators, consists of a concrete vertical right cylinder with a flat base and a shallow-domed roof.

The planneJ preliminary dimensions of the containment structure are as follows:

Inside diameter,130 f t; inside height, 185 ft; cylindrical wall thickness, 4 f t; and dome thickness, 3 1/2 f t.

ne cylindrical portion of the containment structure is post-tensioned with horizontal (hoop) and vertical tendons.

The hoop tendons are anchored at 3 buttresses equally spaced around the containment structure.

These tendons extend 240 around the cylinder periphery, bypassing Intermediate buttresses.

The dcme has a 3-way post-tensioning system.

The foundation slab is conventionally reinforced with high-strength reinforcing steel.

The interior of the containment shell is steel-lined with ASTM A-285 carbon steel plate, Personnel and equipment access hatches are provided to permit access to the facility. There are a number of additional penetrations for piping and electrical conduits.

Section 2.9 of the PSAR Indicates that major structures will be founded f

I in the San Mateo foundation.

The applicant Indicates that even the heaviest structure can be supported in this material using spread. footings or mat j

f oundat i ons.

1 SOURCES OF STRESSES IN CONTAINMENT STRUCTURE AND CLASS I CCHPGENTS The containment structure is to be designed for the folicwing loads:

dead load, including hydrostatic pressure; live load; accident containment design pressure of 60 psig; proof test pressure at 115 percent of design pressure; j

external pressure of 2 psi; thermal load arising f rom the maximum temperature

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i gradient through the concrete shell and mat, based on a maximum design temperature in excess of 250 F; wind load varying with the height and corresponding to a 90 miles per hour basic wind 30 f t above grade; and seismic loads, as described next.

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3 The applicant, in Anendment 14, indicates that the design is to be made for a Design Basis Earthquake characterized by a raximum horizontal g:cund acceleration of 0.679 to insure containment and safe shutdown; the plant is also to be designed for an Operating Basis Earthcuake based on a maximum horizontal ground acceleration of 0.33.

These seismic design levels 9

are adequate.

COMMENTS ON ADEQUACY OF DESIGN l

Foundations and Cuts l

The PSAR presentation Indicates that heavy structures will be supported on spread footings or mat foundations, and that for these types 1

of foundations the total and differential settlement will be small. The l

foundation scheme proposed by the applicant is acceptable to us.

The applicant indicates that the highly compacted, dense nature i

of the San Mateo formation makes the chance of 1 Liquefaction of the foundation j

sands during an earthquake unlikely. We concur in this evaluation.

There is an Indication on page 11-17 of Appendix 2B that cuts as de.cp as 70 f t will be required for the construction of Units 2 and 3.

l slope stability analyses have been carried out for earthquake accelerations corresponding to 0.25g and 0.509, and we understand will be made for the higher accelerations now indicated in Anendment 14.

Further elaboration on the excavated slopes for Units 2 and 3 is l

presented in Section 2.9 beginning on page 2.9-9 (Amendment 6) and indicates that the slopes are considered critical or noncritical, depending upon whether l

slippage can cause any structural or equipment damage at the plant. The discussion given indicates that vertical earthquake effects have been considered

4 in a preliminary fashion along with the horizonta: sf fects, and that it is estimated that the amount of slippage can be handled by the terraces and other provisions incorporated in the site design. There is every reason to believe that, with careful analysis, the possibility of slope failures can be calculated adequately to insure the safety of the plant and critical items of equipment.

l On the basis that comprehensive analysis will be carried out for the appropriate l

levels of earthquake excitation finally agreed upon for the plant design, and that the design criteria will incorporate conservative safety factors against silp, we concur in the general approach adopted for the design of the cut slopes.

1 The discussion on page 1.8-38 of the PSAR indicates that the containment structure foundation will be located approximately 20 f t below the adj acent finished grade.

The method selected for handling this soil-structure l

in eraction is not presented but it is indicated that the details of the j

i procedure will be based upon the reference material given in Section B1 of Apoendix B, and will be submitted af ter a more detailed design.

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On page 1.8-49 at the bottom of the page, there is a statement indicating that approximate analysis of containment structures for local loading originating f rom the earthquake excitation will be made.

It is indicated that previous work on similar containments indicates that there is disagreement l

l concerning the actual local effects on the portion of the structure below grade l

anong experts, and that the designers plan to consult with the seismologists and seismic consultants on the details.

We interpret these various statements to mean that further infonnation will be forthcoming as to the criteria to be employed in design to account for possible soil-structure interaction at the seismic levels now used.

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6 in Section B.2.3.1.1.1 and 8.2.3.1.1.2 in Appendix B of the PSAR,

" gravity coefficients" are presented.

The manner in which these vertical seismic coef ficients are presented suggests that the design for vertical excitation may involve the use of constant acceleration coefficients.

However, in the material filed with Amendment 4, and particularly that given in Section B.2.3.1.2.1 for structures (Type A) and in Section B.2.3.1.2.2 for structures (Type B), the discussion indicates that the vertical excitation will be treated in the same manner as the horizontal excitation with regard to amplified response.

On the assumption that this is the approac' employed in the analysis, we concur.

l D ampi ng The structural damping to be employed in the design is discussed in several places in the PSAR and in Amendment 14.

The values used are listed in Tables B.2-1.

The damping values, including soils damping, are limited to an overall proportional modal damping value of 10 percent for the DBE. We concur in the damping values indicated and in the limi tation to a naximum of 10 percent.

Methods of Dynanic Analysis The presentation on page 1.8-49 indicates that the general analytical model for the analysis of the containment structure for earthquake motion has not been completed (See page 1.8-163) but that it will meet the detailed requi rements of Appendix 8.

The information presented in Appendix B and updated l

j through Amendment 4, and particularly that in section B.2, Indicates that the l

structures will evidently be categorized into two types (A and 8) and that they will be analyzed by generally available computer codr such as SMis and STARDYNE.

The general description given suggests that the approach will be satisf actory, al though few detail s are gi4n.

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In Amendment 14'It is stated on page 1.8-121aa that the response 1

spectra corresponding to tim,e-histories 'used -in the analysis will not be available until about August 1972, but are expected to envelope the smoothed response spectra employed as the criteria for design.

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Seismic Analysis of Equipment and Piping The approach to be followed in the seismic analysis of equipment.is described on page 8.2-13.

It is indicated that the systems will be analyzed' by the response spectrum technique.

The description Indicates that simplified j

analytical models will be employed as re' quired.

It is also indicated that special. attention will be given to the flexibility or rigidity characteristics of pipe networks and that local restraints and hydraulic snubbers will be placed as required.

The analysis of ' reactor internals is described on page 8.3-11 and the general aoproach given is acceptable.-

Further details on the design approach for the reactor vessel, steam generators, and reactor coolant piping-pump assembly are contained in presentation in Section 8.3 beginning on page 8.3-8.

The approach given for this portion of i

the equipment and piping appears satisfactory.

It is not clear that this. covers 1

all of the Class I piping in the plant.

Other information concerning piping analysis and design is presented on page 1.8-35.

The details on the piping analysis are satisfactory in concept.

For.certain Class i systems end equipment, where analytical models and normal mode tneory may not be applicable, the applicant indicates that testing may be employed to help insure functional integrity.. This approach appears satisfactory.

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8 Cranes The discussion on page 1.8-48 Indicates that cranes in critical areas of the nuclear facility will be designed to insure that they are adequately tied down and cannot be dislodged f rom the rails during seismic excitation.

,j This approach is satisf actory.

Class I Eautpment In Class II Structures The design approach to be followed for Class I equipment items which are located in Class II structures is discussed on page 1.8-37.

The applicant indicates that special attention will be directed to insure a conservative design approach f or those portions of the structures, and moreover that the response of Class I conponents located thereon will be examined in detail also.

j This approach appears satisfactory.

j Penetrations and t.iner Plates f

The general design approach for the penetrations and liner plates as outlined in Sectico 5 appears satisfactory insofar as the details given are concerned. We expect that the final comprehensive seismic design document referred to on page 1.8-163 of Amendment 14 will include consideration of the seismic aspects of the design of these details.

These Items should be reviewed when the document is available.

General Deston Stress Bases The conbined load expressions applicable to design are presented in Section B.3 and appear generally acceptable.

We understand from our discussion with the applicant and AEC

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representatives in Urbana on 8 June 1972 that the design stress criteria are -

l generally such as to limit stresses to less than yleid values. We concur in this criterion.

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