ML20234F457

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Forwards Preliminary Draft Re Structural Considerations in Connection W/Proposed Bodega Bay Reactor,Per 630528 Telcon W/Hadlock
ML20234F457
Person / Time
Site: 05000000, Bodega Bay
Issue date: 05/29/1963
From: Williamson R
HOLMES & NARVER, INC.
To: Bryan R
US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20234A767 List: ... further results
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FOIA-85-665 NUDOCS 8709230128
Download: ML20234F457 (14)
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. May 29,1963 i 4

Mr. Robert H. Bryan Chief, Research and Power Reactor d Safety Branch Division of Licensing and Regulation U. S. Atomic Energy Commission Washington 25, D. C.

De'ar Mr. Bryan: .

In accordance with my conversation with Mr. Hadlock on May 28, 19 63,~

I am transmitting a copy of a preliminary draft relating to certain -

structural considerations in connection with the proposed Bodega Bay reactor. The material deals with items 3c and 3d of the suggested j outline of work and discusses certain other aspects in addition.

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Unforeseen urgen'cies have unfortunately delayed the completion of the preliminary draft, so that it has not been possible to coordinate this-effort with that of Dr. Newmark prior to this time, as originally in-tended. In a call to Dr. Newmark on May 29, he indicated that he would not be available for such a coordination review before June 12.

However, I am sending to him a copy of this preliminary draft and we plan to discuss 'any coordination problems by phone on June 7. We both feel that these problems will not be difficult to resolve, and can very likely be handled entirely by phone.

It is not intended that this preliminary draft, in whole or in part, be made a matter of public record without appropriate modification. I ho e that the material will meet your needs and I will be glad to cooper-g dalgih - y changes you require.

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A HOLMES & NARVER, INC.

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BODEGA BAY ATOMIC PARK UNIT NUMBER 1- *. * '

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3. Special Considerations in Design of Facility Components l .

3.1 Gene ral '

f This material includes a ' discussion based on References.'1' through 5 and supplementary information obtained during a meeting held at the University of Ulinois on May 17, 1963. 'It utilizes as a guide the suggested outline of work presented at the above meeting.

The comments are intended to serve only as general guide-

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line s. Neither the information nor the time are available to provide a detailed itera-by-item review of specific components ' an effort , -

which should be a part of the designer's responsibility.

Integrity of the entire facility is totally dependent upon the absence of gross differential foundation movement.' Movements of this nature would be associated with slippage of faults located beneath' the site. Such movements could also be identified with structural j weaknesses in the granite base rock, extreme consolidation of the i soils overlyir.g the base rock, or landslides in these soils. It would' )

be impossihm to design an installation to survive such large displace-ments. The entire discussion assumes that such movements do not 'I occur. I j

Scismic resistance depends on response of numerous com- 'l ponents whose structural integrity is generally. ignored when ground-  !

motion is not a factor. Because of this,' many features customarily con-sidered non-structural, including components of mechanical and electrical systems, require special structural attention in design to avoid weak links in the system. For this reason, the discussion' considers these items as well as those usually classified as structural.

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3. 2 Reactor Substructure and Foundations The main foundation problem associated with the design and-construction of the reactor substructure (cylindrical concrete structure housing the reactor) appears to be that of ground water. .This will cause sizeable static lateral pressures on the foundation, which will be essen-tially uniformly distributed under normal conditions. Transient unsym-

. metrical pressures may occur under earthquake conditions, b'ut these [

1 should not cause any serious design problem. . Minimum steel percent- 3 ages needed for ductility requirements are probably adequate for lateral pressures. It should be feasible to provide the necessary seismic resis-  !

tance in the substructure with proper attention to the reinforcing steel details. 1

' Special treatment may be ' required for thermal stresses in the region of the dry well. Internally, the substructure with its compart- I l

mented interior ic highly redundant, and will require the use of overlap- l ping assumptions in design; however, in these areas seismic considera-l 4 l

tions should not be of major importance. l The turbine foundation is situated on soil, whereas the reactor j l

substructure is founded on bedrock. The soil report (Reference 5) con- '

templates the possibility of about one inch differential settlement between the two foundations, most of which would occur during construction. How-ever, in the design of the connecting steam lines and any other non-expend-able components crossing this joint, it is felt that allowances should be made  !

y- 1 for at least several inches of differential settlement}o arrive at maximum  ;

assurance against rupture of these critical elements. There should be no particular problem in, designing the bents and mat foundation supporting the turbine and generator to resist high seismic forces.

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3. 3 Piping and Equipment ,
3. 3.1 General Accommodating the seismic stresses in the piping systems of this installation should be simpler than the similar problem of shock loading encountered in the design of the piping systems used in nuclear submarines, which involve transient inputs many times gr ate r. However, more than usual care is mandatory in the design sf those systems of the facility which are critical from a safety view- ,

i point because: (1) minimization of thermal stresses calls for a min-l imum amount of restraint, whereas minimizing of se'ismic stresse.s 1

requires the opposite - leading to a conflict which must be resolve d m  !

i design; (2) the usual static analysis using factors of 0. 20g or less may I result in significant overstress in an earthquake of the anticipated in-tensity.

Brittle materials should be avoided in all elements of the piping system stressed by earthquake motion. This limitation should apply not only to the piping and pressure vessels, but also to supporting elements, all appurtenances, including valves, and to pumps and their connections.

3.3.2 Response The equipment elements, including such components as pumps, motors, valves, and pressure vessels, and their supports, along with the connecting piping constitute a highly elastic structure with low damping. It is not unusual to find that the fundamental period of the system lies in a range which maximizes the response to close-in earthquakes.

This combination of factors can amplify significantly the effect of ground mo tion. For example, the ground motion criterion proposed in the PHSR (Reference 1) with its peak acceleration of 0. 33g, could in some instances, induce stresses which would approximate those caused by a static lateral force of Ig acting on the system.

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. 3-4 3.3.3 Differential Motion 1

In addition to the differential motion which often must {

be expected due to seismically induced oscillations in piping systems connecting pieces of equipment mounted on a rigid common support, l 1

piping connecting equipment mounted on separate foundations may be j l

subjected to the effects of tilt and relative displacement of the founda- 1 tion s. The main steam loop leading from the reactor to the turbine is

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an example of such a case. A

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Each main steam line running from the reactor to the turbine should be specially investigated for this case. The effects of seismically induced oscillation of the loop, plus those due to the estimated differential displacement between the reactor substructure and the turbine foundation shculd not cause overstress when combined with operating stresses. A rough calculation indicates that these loops should be capable of tolerating several inches of differential displace-ment without incurring large stresses. The same type of criterion should be applied to any other line of critical importance which crosses such an tnterface.

3.3.4 Stress Analysis Manual stress analysis of a complex piping system re- ..,

quires the use of simplifying assumptions, but may be entirely adequate if it can be determia. 4 that the results are conservative. However, com- f puter programs originally used for ar,alysis of dynamically loaded piping systems in nuclear submarines, have been applied to evaluate earthquake effects in piping systems of nuclea eeactor facilities. This approach should be considered.

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3. 4 Containment
3. 4.1 General i

Dry containment. in the form of a containment building  ;

1 surrounding the entire installation, as for example, in the EBWR reactor, -!

is usually sufficient to contain the equilibrium pressures resulting from l -

a complete meltdown which might result from the absen.ce of coolant or inability to insert the control rods. The suppression containment system ~

of the Bodega Bay reactor represents a less conservative approach and perhaps reflects a growing confidence in the advance of reactor technology; ,

l as for example, in abandonment of the assumption commonly made in dry f /

containme nt, that release of fise, ion products can occur simultaneously / j with buildup of internal pressure. l q

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The functioning of this system apparently presumes  !

that: (1) sufficient coolant is available; and (2) inability to shut down the reactor is not credible. In addition to a dependence on the integrity of structural components, such as the dry well, the suppression contain- i ment depends on the proper functioning of mechanical devices which include a shutdown system (control rod insertion or poison injection) '

and a spray system.

To avoid deficiencies it is important that a cornplete systems approach be used in the anti-seismic design of the suppression containment in which all components, including those of the shutdown and spray systems, regardless of whether they may be claasified as structural, mechanical, or electrical, s receive the same degree of attention.

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3. 4. 2 . Pressure Vessel There should be no particular problem in bracing the pressure vessel laterally to resist earthquake-induced forces.in such '

- a way that the thermal expansion movements can be accommodated.

While it is probhble that the internal, parts contained in the pressure vessel are not particularly sensitive to the induced forces from the ground motion, including that associated with " sloshing" of the coolant, nevertheless, these parts should be looked at from this standpoint in sufficient detail to verify that this ~ supposition is correct.

3.4.3 D_ry Well and Suppression Chambei-i Stresses from seismic effects on ths dry well and sup- ' L!

pression chamber should not create any serious problems as compared.

to those from thermal effects. If the concrete.is poured directly against the steel shell throughout, the shell becomes essentially a liner and special bracing for earthquake effects may not be needed. At the other j extreme, isolation frorn the concrete would require the use of seismic bracing. Stress conditions at penetrations customarily require special attention, even in the absence of a seismic threat, and seismic considera-tions do not create any new problems at these points.

3.4.4 Control Rod System If the control rod drive mechanism is not external to the I 7.

reactor vessel, the possibility of jamming during a severe earthquake is -

l probably low. However, this system is of such importance that its seismic integrity should be demonstrated by analysis or other means.

s L 3 4.5 Liq 6id Poison Sys tem i All components needed for injection of the poison solution must be designed to remain functional in a severe earthquake. It is noted  !

that this system is manually controlled. Automatic control should also be considered in view of the possibility of operator error.

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3.4.6 Controls In general the electronic gear used for reactor controls is insensitive to accelerations of intensities found in severe earthquakes.

In addition, much of this equipment may be available under military 1

specifications calling for shock and vibration tests. Earthquake damage l A

to such components would probably be caused primarily by falling objects j i

or deficiencies in mounting, etc. All instrumentation associated with f emergency shutdown should be designed to incorporate failsafe features 1

which insure automatic shutdown. i 4

i Adequate anchorage of such components as instrument panels and relay racks, and " shipboard" stowage practices should be ef-fective in preventing damage to the control system and injury to the operator during a severe earthquake.

1 Some of the emergency actions are manually performed.

Since the typical human reaction to a strong earthquake is one of fright, operator error could be the result. Hence, serious consideration should be given to earthquake drills and to the advisability of automatic controls, j particularly controls involving emergency shutdown.

l 3.4.7 Power Sources Remote power sources should not be considered reliable in a severe earthquake. This is particularly true of any circuits crossing {

the San Andreas fault. Malfunctions of transmission and distribution  !

, systems in California have occurred in strong shoeks. l The, emergency sources for use under seismic conditions i

Should be located at the facility. The emergency engine-driven generator, station battery and associated circuitry should incorporate adequate anti-seismic features.  !

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1 3.4.8 Water Sources The toroidal-suppression chamber probably has a higher degree of reliability as a fluid container under seismic conditions i than any other fluid container at the site, Consequently, seismic prob- l 1 ems are minimized if the volume of water in the suppression pool is adequate as the sole source of emergency coolant in a strong earthquake.

However, ii auxiliary emergene.y sources are needed, the auxiliary containers and supports and associated piping require special attention j and should be designed for maximum seismic resistance.

3.' 5 Other Features l

3. 5.1 Spent Fuel Storage Pool Seismically induced increments of water pressure acting on the eide walls of the spent fuel storage pool cause no structural difficul- l l ty. However, percentages of reinforcing in the walls should be sufficient l l

to prevent seepage through cracks. Use of a metal .iiner (which may be desirable for other reasons) would avoid any question regarding cracking of the concrete. If flooding of the interior of the refueling building is to I be avoided, sufficient freeboard should be proviced above the normal water surface to avoid over-topping from the wave action generated by the ground motion. I

3. 5. 2 Refueling Building l l

The junction between the circular rea ctor substructure l l

and the square refueling building requires special meat.:res for support j l

of the projecting corners of the ; efueling building, Homer, seismic '

l considerations should'not materially add to the problem in this area. l g

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It appears feasible to use the roof of the building as 3 an earthquake diaphragm with the walls functioning as shear walls. In this event, there should be no difficulty in attahing the required seismic re s is tance.

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3. 6 . Inspection Mter a Severe Ecrthquake A decision regarding the need to shut down for inspec' ion in-volves complex considerations which precludc pre-establishing firm courses of action. In addition it is obviously impossible to specificalh I

identlfy the most seismically vulnerable components. Consequently, in discussing the subject of inspection only general comments can 'oe offe re d.

As stated in Reference 1, it is the intent to provide for con-tinuous operation through a major earthquake. Hence, should the facility continue to function daring and after a severe earthquake, there  !

might be a reluctance to shut down for inspection. In that case, a l decision to shut down could be based on information such as that obtained j from:  ;

a. Inspection of those features which are accessible du.nng ope ration.
b. Assessment of the carthquake intensity (preferably from j an instrument located at the site).
c. Examination of operating records for any evidences of unsafe conditions.

A manual scram resulting from the earthquake would argue 5 ery strongly for a shutdown inspection, unless it could be demonstrated that the scram .was unjustified. An automatic scram would obviously justify inspection and repair or replacement of the malfunctioning compon mts which were involved, and it might be prudent to make a complete inspection of all other critical c$mponents during the chutdown period.

In an inspection operation, priority should be given to examination of the components which are most important from the standpoint of public

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. safety. These would be distinguished from those components needed -

primarily to insure continuous power output, 'and whose failure would not constitute an off-site hazard.

Conditions at bends, at penetrations of vessels, and at con-nections to equipment., including pumps and val ev s, 'should be inspected..

Such inspection could be visual, radiographic, ultrasonic, dye-penetrant,.

or other type as appears to be dictated by the particular circumstances.

a Inspection of the reactor substructure, refueling building, . and turbine pedestal for evidences of overstress should be made. This ' would include such items as determining the location and extent of cracking and spalling of concrete and searching for evidences of slippage or. yield '

ing at connections, and tilt,' settlement, . or differential movement of fc,undations and soil.

A requirement that the designer of the facility supply a manual dealing with post-earthquake inspection of the facility should be considered.

3. 7 Seismic Instrumentation Serious consideration should be given to the installation'of a strong motion seismograph or other instrument at the site in view of the possibility of an extremely intense earthquake. Instrumental recordings of strong ground motion would seem to be of the'same order of importance as the recordings of wind direction, velocity and temperabre which are to be made as a part of the meteorological program to be carried out at the site.  !

Instrumental data could be useful in determining whether a post- ,

earthquake inspection shutdown should be made. i If feasible, the instrumentation should measure ground motion both in the o'ver-burden and on the base rock, inasmuch as the intensifica-tion of base rock motion is of unusual interest and importance both from a

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a seismological standpoint and from the standpoint of earthquake engineer-ing, particularly in the case of strcug shocks. The presence of bedrock -

clo1e to the surface would afford this opportunity at reduced cosi, Other #

locations worth considering would be inside the reactor substructure, at the lowest levc1 and at ground floor level.

The counsel of authorities on earth-quake engineering and scismology should be scught in deciding on the number and type of instruments and their location.

3. 8 Design Coordination The earthquake problem affects all the engineering disciplines involved in the design of a reactor facility, including not only structural and architectural engineering, but mechanical and electrical as .well.

The structural engineer is familiar ~with earthquake problems as they relate to building structures. Howe ve rc with the possible exception of some piping systems, mechanical and electrical components almost are never considered from a seismic viewpoint by the structural engineer or the mechanical or electrical engineer.

l Reasonable assurance that the gaps between the various engineer-ing disciplines do not lead to deficiencies in seismic resistance might be provided by a special monitoring effort on the part of the designer of the facility. This might involve adding to the design staff one or more engineers knowledgeable in the field of earthquake effects with the sole duties of reviewing all critical elements to insure that seismic resistance has been properly considered.

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REFERENCES 1.

Preliminary Hazards Summary Report, Bodega Bay Atomic Park .

Unit Number 1, submitted by Pacific Gas and Electric Company, De cember 28,1962, (Docket No. 50-205).

2, Amendments 1 and 2 to Docket No. 50-205.

3 Preliminary Soils Investigation and Seismic Survey, Proposed Nuclear Power Plant, Bodega Bay, ' California, for the Pacific Gas and Electric Company, by Robert D. Darragh and John F.

Stickel, Jr. of Darnes and Moore, Consultants in Applied Earth Sciences, December 2, 1960.

4.

Report of . Seismic Survey, Proposed Nuclear Power Plant, Bodega Bay, California, for the Pacific Gas and Electric Company, by John F. Stickel, Jr. and Robert T. Lawson of Dames and Moore, Consultants in Applied Earth Sciences, January 25, 1960.

5.

Foundaticn Investigation, Bodega Bay Atomic Park Unit Number 1, Bodega Bay, California, for the Pacific Gas and Electric Company, by Robert D. Darragh of Dames and Moore, Consultants in Applied Earth Sciences, April 30, 1962.

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