ML19317E253

Adequacy of Structural Criteria for Oconee Nuclear Station Units 1,2 & 3.

ML19317E253
Person / Time
Site:	Oconee
Issue date:	06/30/1967
From:	Hall W, Newmark N NATHAN M. NEWMARK CONSULTING ENGINEERING SERVICES
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ML19317E246	List: ML19317E245 ML19317E253
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NUDOCS 7912170498
Download: ML19317E253 (10)

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..j N A T 11 A N M. NEWMARK 1114 Civil Engineering Building Consulting Engineering Services Urbana, Illinois 61801 Report to AEC Regulatory Staff ADEQUACY OF THE STRUCTURAL CRITERIA FOR THE OCONEE NUCLEAR STATION UNITS 1, 2, AND 3 DUKE POWER COMPANY (Dockets 50-269, 50-270, and 50-287) by l

N. M. Newmark and W. J. Itall June 1967 l

' 1 21bI t 7912170

<;i ADEQUACY OF Tile STRUCTURAL CRITERIA FOR THE OCONEE NUCLEAR STATION UNITS 1, 2, AND 3 by N. M. Newmark and W. J. Hall INTRODUCTION This report concerns the adequacy of the containment structures, compenents, and dans for the three units of 2452 MWt each (874 MWe, net) for which application for a construction permit and operating license has been made to the U. S. Atomic i

Energy Commission (Dockets No. 50-269, 50-270, and 50-287) by the Duke Power Company. The facility is to be located on the shore of future Lake Keowee in Oconee County, South Carolina, 8 miles NE of Seneca, South Carolina.

The report is concerned specifically with the evaluation of the design cri-teria that determine the ability of the containment system to withstand a design earthquake acting simultaneously with other applicable loads forming the basis of the containment design. The facility also is to be designed to withstand a maximum carthquake simultaneously with other applicable loads to the extent of The seismic design criteria for insuring safe shutdown as well as containment.

Class I equipment and piping are also reviewed herein, along with a review of the analyses of the dams which are required for impounding the required cooling water supplies. This report is based on information and criteria set forth in the Preliminary Safety Analysis Report (PSAR) and Supplements thereto as listed at the end of this report. We have participated in discussions with the AEC regulatory staff, in which many of the design criteria were discussed in detail.

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DESCRIPTION OF Tile FACILITY Oconee Nuclear Station Units 1, 2, and 3 are described in the PSAR as pressurized water reactors for which the nucicar steam system and fuel cores are to be supplied by the Babcock and Wilcox Company, each designed for a power output of 874 MWe (net). The reactor coolant system for each unit consists of two closed reactor coolant loops connected in parallel to the reactor vessel, The reactor each providtd with reactor coolant pumps and a steam generator.

vessel will have an inside diameter of about 14 ft-3'in., a height of about 41 ft-9 in., and is designed for an internal pressure of 2500 psig, a temperature of 650 F, and is made of SA-302 Grade B steel clad with Type 304 austenitic stain-less steel.

Each of the reactor units is contained in a fully reinforced concrete structure in the shape of a cylinder with a shallow domed roof and a flat foun-dation slab. The cylindrical portion is prestressed by a post-tensioning system consisting of horizontal and vertical tendons. The dome has a three-way post-tensioning system. The flat foundation slab is conventionally reinforced with high-strength reinforcing steel, and the entire structure is lined with a 1/4 in, welded steel plate. The cylindrical part of each of the containment structures is approximately 116 f t inside diameter, has an inside height of 206 f t, vertical wall thickness of 3 ft-9 in., and a dome thickness of about 3 ft-3 in. The foun-dation slab is about 8-1/2 f t thick.

The PSAR on page 5-1 of Vol. I indicates that the design will in many respects be similar to that for the Florida Power and Light Ccmpany's Turkey Point Plant, Consumer Power Company's Palisades Plant, and Wisconsin-Michigan Power Company's Point Beach Plant. Although no stated details are given, we assume, then, that the cylindrical wall is to be provided with a system of hoop tendons which are I

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placed in a 3-120 system using six buttresses as anchorages ci;h the tendons staggered so that half of the tendons at each buttress terminut- at that buttress.

In Appendix 5B it is noted that the prestressing will be post-tensioned, and un-honded, with the tendons encased in rigid steel conduit and corrosion protection provided by grease injected into the conduit under pressure. The answer to Question 9.2 of Supplement 1 indicates that the BBRV system of prestressing will be employed.

From Appendix SE and Figure 5-1, it is noted that the welded steel liner will be at least 1/4 in, thick and made up of ASTM A-442 steel with angle-type ahchors. It is noted that the liner plate will be thickened in the vicinity of penetrations.

Appendix SB indicates that ASTM A-432 reinforcing steel will be used in the base slab, and that ASTM A-15 deformed bars will be employed in the cylinder wall, the domed roof, and around the openings to control shrinkage and tensile cracks. It is further noted in Appendix SD that for large 14S an- 18S rein-forcing steel, Cadweld splices will be employed,-and the Errata f41ed with Amendment 3 indicate that the tensile strength of the splices will equal or exceed 125 percent of the minimum yield strength of each grade of reinforcing steel as specified in the appropriate ASTM standard. We recommend that tack welding or other welding not be permitted for the A-432 bars in the foundation slab or elsewhere, to avoid the possiblity of fracture or other difficulties in achieving the required ductility of these reinforcing bars.

The geology is summarized in Appendices 2A and 2E; on page 2-9 of Vol. I of the PSAR it is stated that the structure will be founded on the normal Piedmont granite gneisses.

SOURCES OF STRESSES IN CONTAINMENT STRUCTURE AND TYPE 1 COMPONENTS The containment structure is to be designed for the following loads: dead load of the structure; live loads (including roof loads, pi forces, and reactor service crane loads); accident pressure load associated wit oss-of-coolant acci-dent of 59 psig; test. pressure of 67.9 psig; and external- ternal pressure differential of 3 psig corresponding to a drop of barometric pressure associated with a tornado with wind speeds of 300 mph (Supplement 4) as well as wind loading corresponding to 95 mph at 30 ft height.

On the basis of the information presented on page 5-5 of Vol. I of the PSAR, Appendix 5B, page SB-4, and the answer to Question 8.5 of Supplement 1, and in accord with the USC&GS report (Ref. 3), the design earthquake will be characte-rized by a maximum horizontal ground acceleration of 0.05g and the maximum earth-0.109 quake by a 0/9/g horizontal ground acceleration. The structure is to be founded on firm basement rock.

COMMENTS ON ADEQUACY OF DESIGN Seismic Design -- In connection with the selection of the design earthquake and the naximum earthquake, we agree with the values selected, and concurred in by the USC&GS, namely that of a basic design for a design earthquake of 0.05g and design for a maximum earthquake of 0.10g maximum horizontal ground acceleration.

On page SB-4 of Appendix SB, for the design earthquake of 0.05g, it is indi-cated that the horizontal and vertical acceleration will be taken as equal in' intensity. We find no mention of this fact for the maximum earthquake but assume that the same situation will obtain there, and assuming that this is the case, we concur in this approach.

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The proposed response spectra for various degrees of damping for the maximum earthquake are presented in answer to Question 8.5 of Supplement 1, for the design f

carthquake as part of Appendix 2B, and as modified in both cases by Supplemen j

We find no explanation for the basis of the selection of the ground motions

(" ground motion spectra"), other than for the acceleration values which have al-We have

i ready been agreed upon and which control in the high frequency band.

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compared the revised response spectra (Supplement 4) with those presented in

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report TID-7024 and find them to be substantially in agreement for frequencies if not all, structural elements will above 0.2 cps, the region in which most, fall.

We believe that the applicable parts of the spectra are acceptable ~ for I

l design purposes.

The damping values to be employed are listed in answer to Question 8.4 of We are in agreement with the damping values given therein with Supplement 1.

l to be used the further understanding, however, that the 5 percent damping va ue for the maximum earthquake will be employed in the design in such a way tha '

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there will be a limitation on the deformations of the containment struc its components.

The general dynamic design approach outlined in answer to this d for same question appears acceptable to us both for the containment structure an j

the piping.

j The loading combinations for the containment desi'gn are presented in A ~

SA.

We are in agreement with the load f actor expressions stated there for th

[ In reply to Question 8.1 of Supplement casef of the design and maximum earthqu'ake.

is noted that "the design criteria which will be applied to the 1, however, it h will permit above loading is that the defortt.ation will be limited to values whic 1, This statement provides no _ guide as to what _ the a safe and orderly shutdown." '

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In impaired in any serious manner by such a minor slippage, should i lt d,it occu the dams can withstand the maximum earthquake st pu a e summary, we believe that b I's not great for although the margin of safety against slippage, as noted a ove, As documented in Supplement 4 a natural the maximum hypothetical earthquake.

cooling in the event of unexpected pool of water will be provided for shutdown dam failure. interest General Design Considerations _ - We have reviewed with care and building as presented the design criteria for the prestressed concrete reactor h

in Appendix SC, and the elaboration on the development for handling f Supplement 2. We are in at yield loads as given in answer to Question 8.7 o l concrete tension and agreement with the provisions there for handling principa In the event that further data the new recommendations for handling radial shear.

ages, we trust become available on this matter prior to completion of the design i

if this appears warranted that such information can be incorporated into the des gn, fly in Penetrat_lons_ -- The design of the penetrations is described brie Question 8 @

Section 5 of Vol. I of the PSAR, and elaboration is given in answer to On the basis of the discussions presented therein, we concu of Supplement 2.

i the approach that is described for this particular des gn. ram Surveillance _ -- We find some information on the planned surveillan ible surveillance in Section 5, and recommend strongly that a reasonable and sens the life of the structure.

program be maintained throughout f ths i

Piping and Other Type 1 Components -- We find discussion of the 1 which refers to Append piping presanted in answer to Question 8.1 of Supplement ification on 5A as appropriate for the class of piping involved, with further ampl i 8.4. We are in gener the dynamic design provision as given in answer to Quest on L

_g-agreement with the approach proposed therein, but are still not sure exactly how the piping analysis will be carried out in the sense that is implied in the last paragraph on page 8.4-3 (4-1-67), which states that the stresses from the horizontal and vertical components acting simultaneously will be combined with the stresses due to weight, thermal and mechanical loads, and internal pressure, e

and in turn these stresses will determine the required yield strength of the limitations This does not completely answer the question of what piping systems.

will be placed on t.he piping in terms of behavior under the maximum earthquake, We recommend, for the particularly in terms of limitations on deformation.

specific materials used, that the deformations be limited to reasonable values Particular which will preclude any difficulties with fatigue or fracture.

attention should be given to the piping at those places where it penetrates the containment, or to that piping which is required for safe shutdown in this regard.

The same provisions apply to piping that will run from intake structures to the plant and which will be required for safe shutdown in the event of an earthquake or an accident.

Conclusions _ -- On the basis of the information presented, and in accord with the design goal of providing serviceable structures and components with a reserve of strength and ductility and which will provide for containment as well as safe shutdown, we believe that with approapriate attention to the design details as discussed in the body of our report, the design criteria outlined for the contain '

ment structures and Type 1 piping can provide an adequate margin of safety for seismic resistance.

1. " Preliminary Safety Analysis Report--Volumes I and II," Oconce Nuclear Station Units 1, 2, and 3, Duke Power Company, 1966.

2. " Preliminary Safety Analysis Report--Supplements 1, 2, 3, and 4," Oconce Nutlear Station Units 1, 2, and 3, Duke Power Comapny, 1967.

3. " Report on Seismicity of the Oconee Nuclear Station Units 1, 2, and 3,"

U. S. Coast & Geodetic Survey, Rockville, Maryland, June 16, 1967.

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