ML20235X824

Bodega Bay Atomic Park,Comments on Amend 8

ML20235X824
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Site:	05000000, Bodega Bay
Issue date:	08/20/1964
From:	Williamson R HOLMES & NARVER, INC.
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References
FOIA-87-462 NUDOCS 8710200126
Download: ML20235X824 (6)

Text

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R. A.- Williams'on -

L 8/20/64 Bodega Bay Atomic Park e

Comments on Amendmen't 8 The following comments are offered regarding this amendment.

1. Provisions for Relative Displacement -

The applicant proposes to provide the flexibility needed in. vital-t

" umbilical" features to withstand a three foot relative displace-ment between the reactor building and adjacent structures. This q

proposal appears to be entirely feasible in the case of inherently.

flexible elements such as cable, and conduit and low pressure piping of small diameter. If the item does not require lateral support to resist effects of earthquake vibrations, the measures needed in these cases are not elaborate, and consist largely of providing slack or free length and avoiding any detrimental con-st raints.

To preclude degradation of reliability, structurally significant plastic strains should not be permitted in vital umbilical features.

1 Such a requirement calls for more special measures to increase inherent flexibility as, for example, flexible joints in pipe.

'Ihe steam line from reactor to turbine is an example of this situ-ation, although the steam line, perhaps, cannot be considered as -

vital as other features, because of the presence of check valves to FoIA-57-4a-8710200126 871014 PDR FOIA K

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. q minimize the consequences of rupture. In the case of the steam line, flexibility is insufficient to tolerate a three foot displacement without development of plastic strains, based on the. configuration l

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'shown in the PHSR. Therefore, if reliability comparable to that of '

Class 1 items is required, the contemplated design would require modification to incorporate greater flexibility. ' Bellows joints in this line may afford a m eans of absorbing a three foot displacement -

and withstanding the effect of earthquake vibrations at the same time without overstress.

There are certain limitations in the use of such joints, particularly~.

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with regard to the combination of pressure, diameter and movement capability. The 1100 psi pressure of this installation, 20 inch pipe.

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diameter, and a rotationr.1 motion capability of about 3 to 4 con-l l

stitute requirements beyond the limits of standard off-the-shelf l

components, and call for special design. While there is considerable

reason to believe that a bellows joint can be designed for these con-ditions, it has not been possible to poriitively verify that this is so.

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l The applicant states that the steam line, (presumably as shown in I

the PHSR, of carbon steel material, and without intermediate joints) l will absorb a three foot displacement without failure, but recognizes that the stresses are greater than the yield stress, Pre sumably, also the computed values approach the ultimate tensile strength of l

the material. (It is to be noted that computed values of, stress above '

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'a yield are fictitous and do not accurately indicate structural b.chavior). The applicant's computation evidently implies the complete absence of earthquake bracing between the extreme ends of the pipe. Otherwise, the restraining forces imposed on-

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.the pipe by the bracing would lead to a computed strese greater than ultimate for carbon steel.

The applicant's concept apparently visualizes yielding of pipe and-supports. A building structure of. ductile material can tolerate strains at least several times the strain at yield. In most piping systems, too, a single self-limiting cycle of yielding due to thermal effects is an accepted possibility at initial startup of the system.

On the other hand, the behavior of building structures under ex-ternal loads causing strains far above yield has been studied ex-tensively; in the case of piping, no such body of knowledge exists.

Furthermore, the biaxial stress condition in piping reduces duc-tibility to some extent. It is quite possible' that the version of the steam line as contemplated by the applicant in Amendment 8 could survive the displacement and earthquake effects in an overtrained condition without actual rupture. However, the probability that this:

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is so is not beyond a reasonable doubt and is too low to be acceptable-I if the integrity of this line is considered as being absolutely vital,

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. An important related problem is the integrity of the valve located just outside the containment. ; Protection' from high mcments,

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g thrusts, and shears may not le capable of achievement solely by using " adequate anchors and bracing beyond the double isolation valves", but may require, in addition, more flexibility in the pipe-than now exists.

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In principle, the relative displacement problem might be avoided t

by anchoring the turbine building to the reactor structure, but this-creates a number of other problems. Among thesc 'are the transfer of forces at the junction and provisions for differential settlement and sliding of the turbine building.

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2. Reactor Containment Structure l

The reactor substructure -(cylindrical reinforced concrete enclosure) l-is extremely massive, with exterior walls at least five feet thick, and has numerous floors and radial walls. Gravity, operating and seismic loads, and additional loads due to displacement do not l

cause severe stresses in this structure. Therefore, if reinforced l-with sufficient reinforcing steel to insure ductile behavior in resisting the imposed loads, there is a high degree of assurance that this s' ruc-t ture would remain undamaged under the simultaneous effects of earth-quake vibrations and displacement, up'to the point where the displace-ment brings the wall of the pit into contact with the structure. Beyond this point, there is the possibility that the containment wall would be breached locally at locations of point or line contact.

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3. Equipment Within Containment Structure It is possible to design the emergency diesel generator, station battery, and associated controls to resist the vibrations trans-mitted by the structure. Equipment of this nature has been designed to survive shock and vibration environments in ships and submarines much more severe than the earthquake effect considered here.

Where integrity in dependent upon functioning of umbilical features, the design of such features should meet the requirements stated in Section 1.

4. Remote Power Sources It is questionable whether transmission of power from remote sourcee can be considered as reliable as on-site power, particularly with regard to the 220 Kv lines crossing the San Andreas fault. De-struction of towers in the fault zone is a possibility if located on the rupture plane, and is very likely more credible than faulting at the site itself. Rupture of lines or tower failure due to the large hori-zontal displacements known to occur on the San Andreas fault could conceivably happen in the case of short spans.

Co11aspe of transmi,ssion towers due to earthquake induced landslides must also be considered at every tower along any portion of the line-where the terrain is susceptible to s uch slippage. Existing towers,

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and substations' located within 35 miles or'so of the San-Andreas t

o fault may be ' subjected to ground motion seven: enough'to cause,

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.tI major damage and loss of function, if not properly designed for.

this contingency.

In spite of previous earthquake damage to California power faci y

11 ties, California power companies.as of 1952 had not applied anti-seismic' measures to existing installations throughout the entire system. Because of this, substations and'other electrical

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equipment suffered severe damage in the Kern County carthquake I

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of 1952. If the Ignacio substation referred to in the PHSR (page III-25, Section K-2) is existing, it may be no more. seismic resis-1 tant than the damaged substations' mentioned above.- Needless to l

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say, dependability of the emergency power supply is reduced to the i

extent that reliance is placed on such features.

Reliability of the 12 Kv line is subject to the considerations just discussed in connection with the 200 Ky line. Here the credible fault displacement is much less, althbugh the spans may also be sh orter.

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DRAFT OF i

REPORT j

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i AEC REGULATORY STAFF j

l SEISMIC EFFECTS ON BODEGA BAY REACTOR l

l BY j

N. M. NEWMARK i

22 AUGUST 19%

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INTRODUCTION j

1 1

This report concerns the ability of the reactor proposed by the l

1 Pacific Gas and Electric Company to resist an earthquake opposite Bodega Head having the maximum effects described by the U. S. Geological Survey and the U. S. Coast and Oeodetic Survey.

Referetce is made in this report to 1

Amendment No. 8 of the Pacific Gas and Electric Company concerning this reactor. Consideration has been given to the danger to public h,ealth and safety in the event of the earthquake occurring, accompanied by movements I

on faults under the reactor containment structure.

The general description of the maximum possible earthquake inm1ves a j

pattern of ground motions similar to that recorded by the Coast and Geodetic Survey in the El Centro Earthquake of May 18,19h0, but with 4

approximately twice the intensity, corresponding te a maximum acceleration of two. thirds gravity, a maximum velocity of 2 5 ft/sec., and a maximum ground displacement of 3 9 t, but vi.h occasional and intermittent

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pulses of acceleration up 141.0 times the acceleration o gravity.

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2 to 1.0g vill be similar to that of the El Centro Ea quake. With the additional accelerations, the high frnquency part of the spectrum vill bs increased somewhat.

In addition, the structures are considered to be subjected to simultaneous ground displacements ranging up to 3 feet, along faults extending under the containment structure or other parts of the plant, yith motions in either horizontal or vertical directions along the fault. It is assumed also that after-shocks of intensity equal to the El Centro quake might be suffered before remedial action could he taken.

Under these conditions, and with the design con:siderations described in Amendmnt No. 8, it is my conclusion, after study of the matter, that the structural integrity and leak tightness of the containment building can be maintained under the conditions described, and with the provisions made by the applicant, as described in Amendment No. 8 and in previous amendments and applications. However, certain precautions that must be considered in the design are outlined more fully herein. There axe also questicos expressed concerning the behavior of the structure in the event of somewhat higher input motions and fault motions.

Similarly, the ability to shut down the reactor and maintain it in the shut-down condition vould not be impaired, provided that the intensities of motion and the magnitudes of fault slip do not exceed those described.

Again, certain precautions.are required as described more fully below.

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l She primary system, being contained in the massive reactor containment structure, vould remain intact up to fault movements not exceeding 3 feet, and under earthquake motions as described above, provided that the piping system carrying the main steam lines from the d2-vell to the turbine y

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inlet is made sufficiently flexible to accommodate a relative movement of 3 feet without failure, and at the same time is damped to reduce its dynamic

't response to earthquake oscillations.

Further comment a this matter is made below.

l The supply of power to the facility, from power lines crossing the major fault, might be interrupted, although the probability of such interruption is probably fairly lov.

In the event of such interruption, auxiliary power supplies are required. The descriptive of these auxiliary power provisions seems adequate.

In general, the provisions for meeting the various requirements are based on methods for which some background of experience is available, or l

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l on minor modifications of such methods, which in the light of analysis and study appear to be reasonably adequate.

The earthquake moticos, including acceleration and velocity as well as displacement, appear to be 2 to 3 times more intense than any that have been recorded in the United States, and probably about twice as intense i

as those experienced anywhere else in the world in recent years for which we hsve fairly good records. Nevertheless, it appears that the design l

I objectives can be accomplished.

t A more detailed discussion of the various points described in Amendment No. 8 is contained in the following material. In addition, consideration is given to several points not specifically discussed in 1

the amendment.

l ISOLATION 07 SHOCK _"" _""~~~~~ BY MEANS OF SAND LAYER In the study of this problem I have had the benefit of a review of the current state of knowledge of this aspect of the problem made by l

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Mrs R. A. Williamsob of Holmes and Narver.

7he statements made herein

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i reflect in general his etudies, as interpreted b) me, and the final con-clusions are based on my views as well as his..

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- She properties of sand under static loading have been studied for many I

years and are well understood. The frictional resistance in natural beds of sand has been measured and compared with behavior of such beds under various conditions. Within recent years dynamic tests of the behavior e

of sand have been made by Dr. R. V. Whitman of MIT, Dr. H. B. Seed of the University of California at Berkeley, and by others. The results of these tests, and of the engineering experience for many years, indicate that the frictional resistance of sand, as measured by the angle of internal friction, changes very little for velocities of the order of 2 ft/sec., and the change is not greater than about 20% for velocities slightly greater 1

than 3 ft/sec.

The coefficient of friction, as measured by the tangent of the angle of internal friction, corresponds to values ranging from about 0 5 or slightly greater up to about 0 9, and in general there appears to um+

be a ="?+ M_reass in the coefficient of friction for high contact l

pressures or for high loadings.

The constancy of the angle of internal frictice is dependent on the relative density of the sand. If it is in a condition corresponding to a density of the order of 90 to 95% of its maximum possible density, the friction angle does not increase with motion.

For very low relative i

densities, or for loosely packed sand, the friction angle of dry sand i

i vill increase with loading. On the other hand, this increase in friction angle of loosely packed sand is accompanied by a zuduction in volume, and this reduction in volume, under conditicals of saturation, correspon6s to a great increase in Tne pressure carried by the inter-granular water.

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This results in a temporarily decreased effective frictional resistance, and therefore it is quite reasonable to expect that under the conditions of deposition of the sand layer, the frictional resistance vill not effectively be increased over the value correspmding to the density achieved in place-ment, over a long period of time. However, after an earthquake has occurred, the conditions prior to the next earthquake vill itave been slightly changed, t

if the sand is in a very loose condition to begin ' ith. Nevertheless, a v

change in density of the sand would not be expected to occur unless

%m 4. AO =A relatively large/ motions take place.

Consequently, the structure should be 8 :7 r

able to resist very successfully a major earthquake, although there are i

possibilities of it not being able to react with fun effectiveness against a second major earthquake of the same intensity.,Since this is a most unrealistic condition, however, it vill not be considered further in this report.

'Ibe skin friction angle between relatively. smooth cmcrete and sand is generally slightly less than the friction angle in the sand itself; hence the resistance to sliding of a properly constructed structure on a sand bed can be made as low as that which corzusponds to a coefficient of friction of the order of 0.6 to 0.8, and it can be expected with some confidence that this coefficient of friction vin not increase with time t

l if the sand is clean and the water inundating it does not contain_

i cemnting compounds.

N-A earthquakes having accelerations less then that zwquired to I

overcome the frictional resistance would not affect the behavior of the sand at all.

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DESIGN OF PIPINC. ETC.. TO ACCOMMODATE RELATIVE K>vsmar AND VIBRATORY EFFECPS The amendment indicates that adequate anchors and. bracing vill be pro-I vided to prevent large relative motions of the piping connecting the dry -

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W dLU2 vell to the seatedemment-ehen. Beyond the anchor at +" :att zt de",

h and extending to the anchor near the turbine generator foundation, the piping will be subject to the differential fault motions ' ranging up to' or l

as much as-three feet, as well as the vibratory motions induced by the earthquake accelerations.

Since the time sequence of the faulting and the oscillat' ion is entirely a random matter, both of the effe'ets must be con-sidered as occurring at any time, even simultaneous'ly.

The precise strains in the pipe due to relative motions or due to l

earthquake vibrations are functions of the length of the pipe runs in the various directions and the method of anchoring. The curvatures in the pipe,

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and hence the maximum strains in it, due to a slow relative motion of the i

ends of a pipe run, are primarily a function of the geometry of the system, and are independent of the thickness of the pipe shell. The diameter of the pipe and the length of the runs in the various ' directions, as well as the conditions at the support, namely whether these are fixed or hinged to provide rotation,- are the primary influences affecting the strains accompanying l

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a given relative motion of the ends of the run. The maximum strain is in i

general of the order of 4 times'the diameter of the pipe times the relative displacement divided by the square of the component of length of the run i

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in the direction perpendicular to the displacement.

strain corresponds to a condition of fixity at the ends of the run.. If Qv r*

the ends are hinged, which is sWJ extreme con'dition that can not be A

obtained except with flexible connections, then the strains are reduced.to i

possibly two thirds as much as those corresponding.to' fixed ends.

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7 Therefore, the higher value vill be used in the estimaws made herein.

Both the horizontal and vertical components of the pipe runs of the 20 inch main steam lines are appzuximately 80 feet. Since the pipe is'20 l

inches in diameter, the corresponding strain is apprezimately 0.003 in/in.

This is about twice the strain at the yield point. Therefore, without flexible connections, the strain in the pipe due to a three foot relative i

motion will exceed the yield point.but only slightly, and by an amount that should not cause any serious problem. To reduce the strains to yield point values would require the introduction of flexibility at possibly two of the joints or elbows in the pipe, or one or more bellows connections at' D#kM the ends of the pipe run. It does not seen

- - to increase the length of the pipe run from 80 ft. to 115 ft., which would be the require-ment to reduce the strain to the yield point value merely by flexibility of the pipeline itself.

The dynamic response of the piping depends on its fundavantal period of vibratice and can be obtained from the shock response spectrum.

Since both the weight of the piping and its stiffness depend on its wall thickness, the deflectim of the piping due to a given acceleration is independent of the wall thickness.

Only the diameter of the pipe and the length of the pipe runs determine the frequency of a pipe not carrying i'(

additional load. For several different configur$tions,of pipe a fairly censistent relationship between maximum %amic strain due to earthquake 1

vibration and maximm strain due to movement of the supports can'be obtained.

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The ratio of the maximum strain due to a spectral displacement, D, for vibration at a given frequency, compared with the strain due to a

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relative static displacement at the ends, 4, is approximately 2 D.

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Hence the earthquake strains which accompany earthquake motions vill-be of

' the same order as the strains for the three foot movement of the ends if; i

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the earthquake displacement is approximately 1.5 ft. Pbr the pipe runs l

considered, Mr. Williamsm estimates a period of vibration of the order i

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of 1 to 2 secs. assuming hinged ends.

My calculations indicate a period of about 0.5 sec. for two fundamental modes, cae primarily vertical and the

- i other primarily-horizontal, when the ends are fixed. These periods are 1

about twice as long, or, one sec., for hinged ends. ' The maximum combined

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i stress when both modes are excited is only slightly greater than the maximum stress for one of the modes. For a period of 0.5 sees., and for-the PG&E spectrum in Figure 1 of Amendment 8. for 0 5% damping, the dis-o

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placement is of the order of 0.25 feet, and for twice this earthquake I

the displacement will be about 0.5 feet.

On this basis, it can be 1

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i estimated that the strains due to the earthquake response are about l

one-third as great as those due to the 3 ft. relative displacement of -

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the supports. Hence, under cabined earthquake and relative displacement due to faulting, the pipe will be overstressed, but not beyond three times

' the yield strain.

y, It should be noted that the respong.e determined above varies directly as the natural period in the range from about 0.h sec. to more than 3.0 l

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sec. In other words, if the period of the pipe can be reduced, its dis-placement vill be decreased in the same proportion. However, reducing the period of the pipe vill require an increase in stiffness in general, I

which would cause difficulties in resisting the relative displacement of the ends.

Conversely, introducing flex 1ble connections will in general-increase the period.of the pipe which will increase the dynamic earthquake strains.

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It appears therefore that scoe further e-iar. ides of the piping design is required before assurance can be given that the piping can sustain both the. earthquake vibrations and the relative fault motions without being' overtrained.

.r It might be pointed out in this regard that the maximum displacement

@W of the pipe, should it become inelastic in an earthquake, would pmbably 9not be different from the maximum displacement were the pipe to remain M

elas tic. Hence the pipe, under the most serious combination of conditions, j

will be strained to about 3 times the elastic ' limit strain at yielding

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$ (under the ccabined effects of the fault motion and earthquake motico).

This is a bit severe, but might be tolerated.

A possible means of reducing the stress involves introduction of damping by, artificial means. If the damping factor is increased from 0 5% to about'205, the dynamic displacements j

'N cut by almost a factor of 3.

Hence, dampers or snubbers attahhed to the j

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pipe in some fashion may be required. These should probably be attached in j

l such a way that they correspond to intemal damping in the pipe rather than absolute damping by connection to the grofad, since the latter will i

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ntroduce additional disturbing forces in the pipe when relative motions l

of the ground or the conte.inment structures take ylace.

All umbilical connections to the reactor containment structure, I

including the main steam lines, should be designed to assure freedom from i

contact with other structures, valls, or earth and rock, by such a distance

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as to provide for the possibility of a three foot fault motion and, in-I addition, the. vibratory motion of the element considered. Also, all vital

_j piping, etc., must be arranged in such a way chat, a three foot fault action occurring elsewhere in the area vill not cause a failure of the vital element.

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The main steam lines and similar important lines should be designed to be locally stiffened by sleeves or doubler pistes, at points where A" Li valves or where anchors are attached, to prevent ovalling or et distortion of the lines that would impair its behavior.

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, 4 SAFETY OF AUXILIARY EQUIIHENT The auxiliary equipment contained within the reactor containment building vill, in general, move as a unit vitbin the containment structure. The fault displacement of 3 ft. for which provision is made does not produce a 'similar displacement within the structure, although it may produce a rotation or tilting of the containment'struc-ture.

However, the equipment described in the ** ant and in the original application can certainly be designed for the slight tipping 1

or tilting and rotation, provided it is not rigidly attached to items which move either a different amount or do not move at all.

1 It ic stated in Amendment 8 that "vbere vital components of the emergency systems are located within the turbine generator founiation of the control building, the inter-connecting piping and cable vill be designed to withstand up to 3 feet of relative displacement between the reactor containment structure and the turbine generator foundation, or control building." The provision of resistance to large relative displacement combined with resistance to oscillations seems capable of t

achievement for relatively small diameter pipes, or for wires, although it is difficult for the 20 inch main steam lines.

SAFETY OF PRIMARY SYSTEM i

j Comments have been made previously regarding the main steam lines l

and the difficulties involved in providing the necessary resistance to l

relative motion and to earthquake vibrations. The statement is made in I

the amendrent that" accelerations experienced by the primary system during l

l such a displacement would be less than the acceleration used in the

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design of the equipment.".It is not clearly stated that the accelerations

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,l experienced by. the primary system 'during the maximum earthquake vould bel less than the acceleration used in the design of.'t'be equipment. Moreover, l

it is not clear, if the relative motion of faulting should exceed. 3 f t.,.

whether there vill not be a greater. maximum acceleration than-that pro-1 l

vided during the earthquake, owing to a possible crashing or battering of the retaining valls outside the gap against the reactor containment.struc-ture. These could induce fairly;1arge, but high frequency, accelerations.

Because of the large mass to be moved, the inertia of this mass, and the 1

l possible weakness of the walls of the reactor containment structure against l

a localized line loading from outside, it is not clear at all that a rela-tive movement of more than 3 feet can be sustained.without producing serious damage to the reactor containment structure or serious accelerations to the primary system within it.

Nevertheless,1for,less than' the three

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foot fault motion, questions of this sort can'not be' raised.

POSSIBLE INTERRUPTION TO SUPPLY OF 10WER The vulnerability of the overbead transmission lines has not been l.

established. These lines cross the San Andreas fault, and although they are supported on videly spaced toweru, there is a possibility that one 4

or more of the towers may be displaced by as much as 20 ft. relative to s

l a neighboring tower.

It is possible that the towers can sustain such a-motion without loss of all of the lines.

However, further study of this problem is desirabic if it is necessary.to depend on this source of power.

The' amendment states, however, that if the external sources are unavail--

able the engine generator, located within the reactor containment structure, t

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A further stfpply of power is available in the battery contained within the reactor containment' structure and control building.

l It must' te regarded as possible that the main overbcad transmission line would be severely impaired in its functioning vbere it crosses the

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1 main fault.

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ABILITY OF STRUCTURES AND EQUIPMENTS 'IO RESIST EARTHQUAKE OSCILLATIONS

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l The procedure described for the design of critical and non-critical l

structures, on pages 19-25, appears in general, to be satisfactory, with l

l minor exceptions. On page 21, the second paragraph indicates that "the i

i design of the plant will be checked to assure that all critical structures, equipment and systems will be capable of withstanding earthquake ground 1

motions corresponding to spectrum...(values)...two times as great as shown on Figure 1 without impairment of functions..." This means an earthquake of maximum acceleration of 0.678, but not with acceleration spikes ranging i

I up to 1.0g.

The difference is not important for items having periods of 1

I vibration greater than about 0 5 sec., but it can be substantial for elements l

having shorter periods or higher frequencies, and the discrepancies become l

progressively larger as the frequency becomes higher' or the period becomes e

lower. A clear and unequivocal statement about -this point would be desira-j i

ble.

In general, there is a reserve margin in almost every element beyond ',

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the point at which yielding begins, even in items of equipment, control rods, fuel assemblies, etc. Dr. Housner's study of the reserve capacity of

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structural elements, in Appendix II of Amendment 8, is sound. Nevertheless, j

l for items of equipment which are not designed for yielding at all, but i

j which have to satisfy certain criteria such as' clearance (sr magnitude of j

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displacement, it is essential to con. sider 'the higher spikes of accelera-

.e tion in their design'in order to provide the necessary reserve margin to assure operation of these items under the extreme maximum conditions.

p In this regard, it should be noted that the design spectrum in '

f Figure 1 is not quite as large as the values that correspond to the extreme peaks of the El Centro spectrum. The values in Figure l'are in general those that correspond to the mean of the oscillations for'the rather, jagged peaks in the individual response spectrum curves for various' earthquakes, especially in the high~ frequency region.

An envelope through the spikes l

would generally lie about a factor of 2 above the smoothed spectrum, particularly for the low values of damping, although it vould approach the -

values reported for the higher values of damping.

This is not regarded as i

an important discrepancy, however, as there are indications that the mean of the oscillations in the spectrun is a much more significant value than the magnitude of the spikes.

Calculations that have been made and that Ere reported for equipment mounted on submarines, and for response of buildings to earthquakes, in general indicate that the measured responses are more nearly consistent with the mean of the oscillations of the spectral values rather than with the peaks.

Hence the smoothing of the spectrum is a rational and reasonable procedure.

The accelerations transmitted to the reactor containment structure -

a will not exceed the acceleration that vill cause sliding on the sand layer, l

1 which may be from 2/3g to 0 9g, depending on the characteristics of t' he sand, until first contact is reached with the side of the ~ cavity.

Since this contact will occur after a three foot fault movement, or even less if some sliding occurs on the sand, a design level of 1.0g for proper i

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SUITABILITY OF PROPOSED DAMPING COEFFICIENTS R

The damping coefficients listed on page 23 of -Amendment No. 8 appear in general to be reasonable.

The degree of precision implied in the selec-tion of damping coefficients to two significant figures seems somewhat unwarranted.

However, the values are in general reasonable for the stress levels implied in the design of the individual elements, or for the con-dit' ions which are involved in their behavior.

l The damping for the reinforced concrete reactor containment structure would be considered high for a structure l'

supported directly on the rock, but may be reasonable considering the fact that the structure is supported on a sand bed.

For-4ce-intensitrearthquakuri.

i.Le 1/3g earthquake,Mf such-is-considered. M M c. de-ign L even-fer

_conditionrthe asiipIHg afslt~be'~of-the order-of-balf as much-as-thstansed for the reinforced concrete reactor containment _structwo.However

, wr de maxinwn_ earthquakes considered; theWing-factor used la..not.at alMaon-EFFECTIVENESS OF SAND LAYER IN CLIPPING PEAK ACCIEMRA l

In view of the comments on the behavior of the sand layer, it can be 7

concluded that the sand layer vill act to clip high peaks of horizontal accel-4 i

eration that exceed its frictional capacity to transmit force to the reactor containment structure.

It will not clip vertical acceleration peaks.

DETAILED DYNAMIC ANALYSIS OF EQUIIHENT The method described on pages 23 and 24 for handling the response of equipent within the building appears reasonable, although for sensitive 1

I items near tbc upper part of the building, the approximate method may not be adequate.

A detailed dynamic analysis, such as described near the bottom of page 24, will be desirable for all extremely sensitive and critical items of equipreent.

Tbc method of analysis described can take into account the i

^

74 september 11. 1964 i

tr. Nethcm M. Newmork i

111 Talbot Leberatory 9: base. 1111 mets

Dear Dr. Newmosk:

Enclosed is a suggested revisies of year draft report en the ledesa 1sy roaster. I have taken the liberty of sugaesting a number of minor wording changes as is indiested in the emeleeurs. Sheeld yee have any problems with the propeeed reverding feel free to disrugard the smagested ebenge and we saa discese the pointe et our usettas en septad er 17.

Na addittee to the proposed wording ep. I have ladiested a number of areas ta a separate ansteomre where 1 believe that year. report eeeld be either modified, starified, er empended.-

71aeas treat these suggaettene la the saan meneer'as the proposed '

verdtag changoes

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aseemst es many of,the.sagenstices es is possible by that time. I would them protese to seed your revised draft (still met la final form)

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to the Agas. so that the =*=== may study it la adesses of the ten-l.

mittee meeting seeduled for estober 7,

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I smarrlass rea CMfGES IN WVISES BR1PF REPORT OF N. M. EEWMANC 1.

Page E, sesend fall peregresh = I unterstand the purpose of this paragraph is to ta41eate year canelasiens wit sospect to the ability of to centeiseent ta1141ag to withstand the postulated earthquake effecto, and met to deal with other statuees of the propened fadif ty amates. If this is earrest, this paragresh might be alarified to inesate the it does not deal with the ataqueer of he design of the penetrattens to the esatadament bullung, such i

V as to amin steen line, eines his particular feature would efhet h i

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leekt1N of h centstament buildas. Also, it is ad elear to um W matare of h *eertata prosestions" that are neftruma to la he last seatease I

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Page 2, last paragraph = Mis paragraph as written emels emir win he primary areten. I suggest that it be empended to taalate your esamente se t

all vital unh111enas senaseted to the sweeter sentatammet strusture. In this event, this paragraph Probably eeM to sostata a qualiftsatten esseerains i

the meet to pswries errengemente to provost M*==

or other failure of h umbilicals caused by eenhet et eenesete walls, ree, earth, etc. ageiset m e esaneettene.

3.

Page 3, first ft11 perngraph = he meanias of the last sentenes in this paragraph is act elear.

Obviously, it is not meant to state that the

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espeesty of b emaillary power provistene is odotunte, but probably.te imateate the %e design of this equipannt is such that it seald readily withstead the postulated earthgaske effhete, b.

Page 3, seeene fk11 paragraph = his peregraph should be expanded te g

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ekov hat the eseign usthods proposed eypea to be adequate.

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, feet fault mettes postulated fler Bodega Eend. m *hich eestaat pressures" t

me "hi$ lee 41 ass" gives in the last sautenee of this paragraph shem14 be l

lated to the eaa% quake offsete postm2ated at Bodega.

6.

Pass 5, first taeemplete paragraph o If possibis, the "relatively'larse j

metiems' given la the hird from last sentanee should be restated in more qualitati,e terms. I understed the last sostenee to seen hat iske "mest

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unrealistic conditien* referred to is the oemarremes of a seeses earequake with the same nazim== effsets pestalated by the WW and WCW. If this is eerrest, this sostenee esels be rephrased te more elaarly indiente its asesing.

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7.

Pass 5. first tuli:paragrush - m last sentenee states that m l

esefftetent et friettom of the sand will met inerease with ties provided i

i pe' that he send is alman and the water tauseating it does act eastela esasettag eenpeands. It wes14 be helpful if his seatesse eeu14 be es.

pas.e4 to imeleste the specifie eeanattag eengeunes whieb veald be este.

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terieus amt what assign measures, if any, sou14 be providst if the immenting e

water unze detersiasi to eastata sue compeones.

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8.

Pass 5, last paragresk - ~ valae of aseelaraties of " miner" earth.

quakes which would met cm the frietianal resistanee of the seed i

j shes14 be given.

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9.

Pages 3 hrough 5 - Estire sectica se Sheek Isolatie by Means of Same Leror - In esmeral. I understen. this seetles to prories a bests for u

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3 a eenelusion est a bortsastal swund displacenset of 3 feet weald met sesult la movement of the ecutaiammet ene to the preessee of the sand layer. purther, I understand it to provide a best's for samaluetas that a vertical ground displacement of 3 feet would d most result in tipptag of l

the oestafamaat bu1141ag. If this tu the sneeral purport of this meetica, it would appear to be advisable to state thsee canalustoms at the end of 4

the sostian. Is it possible that, if hertsental ground settaa shea14 l

oosar, h esatdement ba11 ding weald underse same rotational meties about i

a vertioel axis? If so, is it act possible that the rotettamal displacement at the surface of the centalament bai141ag would be greater thas %st at the g

axis, and therefers greater than 3 feet? If this is possib3e, it seems appropriate to discuss this fast la this section of the report.

10. page 7, first fall peregraph = Shen 14 the ma1a=1**me strelas in the piping take inte at;eauet the possibIm atstica of the sentaimmant vessel 41senseed in item 9 above? In additi e, the sentoase which indiestes h at stratas exeoedtag the yield point aheald met sense any serises problem should be sophrased to indieste that such strains weald met ease lose of integrity ar Watever la seasideved by you to be a sericas problem.

11. Pass 7, seemd ik11 peregraph. I have had at least two commaats from j

persas We de act understand the seeend sentanee of this paragreek. Please tar to better espleta er alarify why the deftasties of the pistas one to a i

given seeeleration is independent of the vull thiekness.

12. Page 9, first full paragraph = he "further eensideration" of the piping desist which you believe to be required should be identified in aere specifie terms.

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13. Peen 9, seeene meta perusrest. The third sentense indientes that streias of three tiene the elastie limit strata at rio14 tag are " severe but det be

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/ telerated". A mese unequiveeal statement would be desirehle me the eenditime under whie sue strain weale be tetorated eben14 be listed.

Ib. Page 9, last peregraph. If rotation of the easteismont is possible a le 4Leemosee la item 9 above, the leet' eentense of this page eben14 j

a it.1 ear a ate. free acau es. b. **em into so.co.4 la n. does.

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of all unkku 1t..

15. Peen 1be five4 fell paragresk, lest centenes. It'eypeere.that the

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onnetussen in his mestenee le valta only if a bish emamah setoute desim spectrum to used la the essign of structures and egeipment. If this is ee, this tus11tisetten eben14 be e4404 to the lest testesse.

16, Peas Ib, last paragrgh - the last sentenee indientes that easteet of the oestatament ves2f, oceur after a 3 feet fanit movenest, er even less if

'ema slidias eseare en the same". I understand %st yee believe that ene t

to to inertia of the eentelement bui141as, one aboa14 act depend en ne 3

j fast that and alleing dakt seeer. Eceever, it is aM alcer to me bee any elleing ese14 seger m1eas these is seatest with the remeter eenta8====t, l

but the last sentense la his paragraph seems to im41eete that this to peseible. Please alarifr.

17, Pass 15 first fait paragraph - me next te last sentenee tadientee

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met the desping for the eestaissent etneture night be et the ereer of haar as sneak of that proposed in the event of los latensity earthquakes, possibly even Abr a 1/3s earthquake. Eines it amet be eseuset that I

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earthenske aseeleraties leser than the maximum postaisted og eesar, i

i esos this statement seen that yen believe that it is necessary to use a 1*Wer ensping eseffistemt than that proposed fler the master seeth i

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l REVISED DRAFT OF

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REPORT To l

AEC REGULATORY STAFF SEISMIC EFFECTS ON BODEGA BAY REAcr0R BY N. M. NEWMARK i

17 SEPTEMBER 196h i

INTRODUCTION Wis report concerns the ability of the reactor facility proposed by the Pacific Gas and Electric Company to resist an earthquake opposite Bodega Head

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of the intensity postulated by the U. S. Geological Survey and the U. S. Coast and Geodetic Survey, including the faulting or relative displacements.

Refer-ence is made in this report to the application by the Pacific Gas and Electric Company concerning this reactor, particularly Amendment No. 8.

The general description of the postulated earthquake involves a pattern of ground motions similar to that recorded by the Coast and Geodetic Survey in the El Centro Earthquake of May 18,19h0, but with approximately twice the intensity, corresponding to a maximum acceleration of two-thirds gravity, a maximum velocity of 2 5 ft/sec., and a maximum ground displace-ment of 3 feet, and with occasional intermittent pulses of acceleration up to 1.0 times the acceleration of gravity. The response spectrum for the earthquake without the additional acceleration pulses up to 1.0g will be similar to that of the El Centro Earthquake. With the additional accelere-tiens, the high frequency part of the spectrum will be increased somewhat.

Fora-97-ez

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s In addition, the structures are considered to be subjected to simult.aneous shear displacements ranging up to 3 feet, along lines extending

'j under the containment structure or other parts of the plant, with motions in either horizontal or vertical directions along the fault.

It is assumed also

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that after-shocks of intensity equal to the El Centro quake might be suffered before remedial action could be taken.

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Under these conditions, and with the design considerations described in l

l Amendment No. 8 and in previous application amendments, it is my conclusion, after study of the matter, that the structural integrity and leak tightness i

i of the ccatainment building can be maintained under the conditions postulated.

l However, certain precautions must be considered especially in the design of l

umbilicals and of penetrations to the containment building. These are described l

l below.

I l

Similarly, the ability to shut down the reactor and maintain it in the shut-down condition would not be impaired, provided that the intensities of motion and the magnitudes of fault slip do not exceed those postulated.

Again, certain precautions are required as described more fully below.

The primary system, being contained in the massive reactor containment structure, would remain intact up to fault movements not exceeding 3 feet, and under earthquake mtions as described above, provided that the piping system carrying the main steem lines from the dry well to the turbine inlet is made sufficiently flexible to accommodate a relative movement of 3 feet without failure, and at the same time is damped to reduce its dynacic l

response to earthquake oscillations. All attachments and umbilicals must be arranged to prevent failure by shearing or crushing due to contact with walls, rock, earth, etc. in the event of major earthquake motions.

Further comment on these matters is made below.

i

. The supply of power to the facility, from power lines cressing the major fault, might be interrupted, although the probability. of such inter-ruption is probably fairly lov.

In the event of. such interruption, auxiliary.

power supplies are required. The sources of auxiliary power described appear to have adequate capability to resist the postulated earthquake. effects.

In general, the provisions for meeting the various requirements are based on methods which in the light of analysis and study appear to be reasonably adequate.

The earthquake motions, including acceleration and velocity as well l

as displacement, appear to be 2 to 3 times more intense than any that have been recorded in the United States, and probably about twice as intense as those experienced anywhere else in the world in the recent years for which l

I ve have fairly good records. Nevertheless. it appears that the design objectives can be accomplished.

A more detailed discussion of the various points described in Amend-ment No. 8 is contained in the following material. In addition, con-i sideratice is given to several points not specifically discussed in the amendment.

EFFECTIVENESS OF SAND LAYER IN SHOCK ISOLATION The sand layer under the. containment building is intended to act in two ways:

(1) to isolate in part the containment structure from the high peaks of acceleration that might be transmitted to it from the ground beneath it; and (2) to permit either horizontal or vertical faulting to take place in' the rock beneath the containment structure without damaging the structure. It will be shown in the following discussico that the effectiveness of the sand layer in reducing the peak accelerations may be questionable', but its effectiveness in reducing the effects of faulting is substantial.

k.

In the study of this problem I have had the benefit of discussion of the current state of knowledge of this aspect of the problem with Mr. R. A.

i Williamson of Holmes and Narver, a consultant to the AEC staff. The state--

l ments made herein reflect in general his views, as interpreted by me, and the final conclusions are based on my views ss well as his.

' Vibratory Effects The properties of sand under static loading here been studied for many years and are well understood. The frictional resistance in natural beds of sand has been measured and compared with behavior of such beds under various conditions. Within recent years dynamic tests of the behavior of sand have been made by Dr. R. V. Whitman of MIT, Dr. H. B. Seed of the University of California at Berkeley, and by others. The results of these tests, and of the engineering experience for many years, indicate that the frictional resistance of sand, as measured by the sngle of internal friction, changes very little for velocities of the order of 2 ft/sec., and the change is not greater than about-20% for velocities slightly greater than 3 ft/sec. The coefficient of friction, as measured by the tangent 'of the angle of internal friction, corresponds to values ranging from about 0.5 or sliahtly greater up to about 0 9, and in general there appears to be no increase in the coefficient of friction for high contact pressures or for high loadings.

The constancy of the angle of internal friction is dependent on the relative density of the sand.

If it is in a conditica corresponding to a density of the order of 90 to 95% of its maximum possible density, the friction angle does not increase with motion.

For very low relative densities, or for loosely packed sand, the friction angle of dry sand will increase with loading.

On the other hand, this increase in friction

I

. j angle of loosely packed sand is accompanied by.a reduction in. volume, and this reduction in volume, under conditions of saturstion, corresponds' to

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a great increase in the pressure carried by the inter granular water.-

This results in a temporarily decreased effective frictional resistance,

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and therefore it is quite reasonable to expect that under tho' emditions of depositim of the sand leOrer, the frictional resistance will not effectively be increased over the value corresponding to the de:sity achieved in place-ment, over a long period of time. However, after at earthquake has occurred, the conditions prior to the next earthquake will have been slightly changed,

)

if the sand is in a very loose condition to begin with. Nevertheless, a change in density of the sand would not be expected to occur unless l

relatively larger motions take place -than those postulated.

~i The skin friction angle between relatively smocth concrete and sand is generally slightly less than the friction angle is the sand itself;.

hence the resistance to sliding of a properly constructed structure on a.

sand bed can be made as low as that which correspcods to a coefficient of friction of the order of 0.6 to 0.8, and it can be azpected with confidence that this coefficient of friction will not increase with time provided 1

that the sand is clean and the water inundating it does not contain cementing compounds.

Earthquakes having accelerations less than that required to overcome the frictimal resistance would not affect the behavior of the sand at all.

It appears from the foregoing that the catainment structure will move with the ground for accelerations less than about 2/34 and possibly even for accelerations as high as 0 9g to 1.0g.

Only the ver,r ' largest peaks of acceleration, grester than the frictional resistance, can be attenuated by the sand layer. Moreover, if the sand layer were to slip at an

8 acceleration of about 2/3g, a ground acceleration of 1.og would involve a slip of the containment structure on the sand. bed of the order of 2-3 inches, q

vhich could reduce the gap provided.for isolation purposes by this same amount.

Faulting Effects

,)

The rock beneath the containment structure may suffqr a postulated fault displacement of magnitude up to 3 feet in either the vertical or horizontal ~ dire ction. Whether or not the sand has become partially cemented, 1

it will be much weaker than either the rock or the concrete and will, there-l 1

fore, not change or influence the fault motion immediately beneath the structure. If the rock faults vertically, the structure vill tip.- The greatest angle of tipping would be that corresponding to a vertical. fault i

occurring at the center of the structure, in which case the angle would j

l l

be approximately equal to the fault displacement divided by the radius of.

the ccatainment building. Such tipping would partially close the gap left between the containment building and the surrounding rock and/or earth.

This must be considered in evaluating the available space in which to accommodate concurrent horizontal fault motions. Both horizontal and vertical motions must be taken into account in considering the integrity of the containment building, other vital structures or any attachments or connections thereto.

When horizontal faulting takes place under the containment structure, there can be a tendency to rotate the containment structure. This rotation.

can result in somewhat larger movements of points on the circumference than the fault motions themselves, 'and must be taken into' account' in evaluating' the effects on both the structure and attachments thereto.

l l

If proper provision is made for the tipping and rotation, and possible l

.7 -

sliding, the containment structure and its associated attachments can be f

designed to resist successfully a major earthquake with maximum effects as postulated. However, if such an earthquake brings the structure nearly,into contact with the sides of the cavity in which it is placed, a second major earthquake may involve the possibility of damage to the structure or the attachments thereto, since the gap providing isolation against fault motions vill have been nearly closed. In other words, the amount of faulting in successive earthquakes cannot involve a greater combined fault motion than three feet in any one direction, and the amount of gap left after faulting must not be so small as to permit battering of the structure or of vital attachments against rock, earth, etc. adjacent to the structure, in after-shocks, or in the remainder of the earthquake following the faulting.

DESIGN OF_ PIPING, ETC. TO ACCOMMODATE RELATIVE MOVEMENT AND VIBRATORY EPPECTS The amendment indicates that adequate anchors and bracing vill be pro-vided to prevent large relative motions of the piping connecting the dry well to the vall of the reactor building. Beyond the anchor at the wall, and extending to the anchor near the turbine generator foundation, the piping vill be subject to the differential motions corresponding to fault displacements ranging up to three feet, as well as the vibratory motions induced by the earthquake accelerations. Since the time sequence of the j

assumed faulting and the oscillation is entirely a random matter, both of the effects must be considered as occurring at any time, even simultaneously.

The precise strains in the pipe due.to relative actions or due to earthquake vibrations are functions of the length of the pipe runs in the various directions and the method of anchoring. The curvatures in thi pipe, and hence the maximum strains in it, due to a slow relative motion of the ends of a pipe run, are primarily a function of the geometry of the system,

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and are nearly independent. of the, thickness of. the pipe shell. The. diameter of the pipe and the length of the runs in the various directions, as well as

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the conditions at the support, namely whether these are fixed or hinged to provide rotatice, are the primary influences affecting the strains accompa+

nying a given relative motion of the ends of the run. The -maximum strain is in general of the order of k times the diameter c2 she pipe times the relative displacement divided by the square of the component of length of the run in the direction perpendicular to the displacement.

Bis value of the strain corresponds t,o. a condition of fixity at the endt of the run.

If the ends are hinged, which is an extremely favorable condition.that cannot'be obtained except with flexible connectives, then the strains are reduced to possibly two-thirds as much as those corresponding to fixed ends.. There-fore, the higher value vill be used in the estimates made herein.

Both the horizontal and vertical components of the pipe runs of the 20-inch main steam lines are approximately 80 feet. Since the pipe is 20 inches in diameter, the corresponding strain is approximately 0.003 in'/in.

This is about twice the strain at the yield point. Therefore, without flexible connectims, the strain in the pipe due to the postulated relative motion of slightly more than three feet would exceed the yield point, but only slightly, and by an amount that should not cause failure. To reduce the strains to yield point values vould require the introduction of flexi-bility at possibly two of the joints or elbows in the pipe, or cne or more bellows connections at the ends of the pipe run.

It does not seem necessary to increase the length of the pipe run from 80 feet to 115 feet, which would be the requirement to reduce the strain to the yield point value merely by increasing flexibility of the pipeline itself..

The: dynamic response of the piping depends -on its fundamental. period

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.9-i of vibration' and can be.obtained from the shock response spectrum.: Since both the weight of the piping and its stiffness depend linearly on its vall

. thickness, the deflection of the piping due to a given acceleration..which is proportional to weight divided by stiffness, is independent of the wall thick--

Only the diameter of the pipe and the length of the pipe runs determine ness.

the frequency of a pipe not carrying ~ additional load.

For several different configurations of pipe a fairly consistent relaticeship between maximum -

dynamic strain due to earthquake vibration and maximum strain due to movement l

of the supports can be obtained.

he ratio of the maximum strain due to a spectral displacement, D, for vibratico at a given frequency, compared with the strain due to a relative i

D static displacement at the ends A, is approximately 2 f. Hence, the earthquake strains which ' accompany earthquake moticas will be of the same j

order as the strains for the three foot movement of the ends if the earth-quake displacement is approximately 1.5 feet.

For tu pipe runs considered, 1

Mr. Williamson estimates a period of vibration of the ' order of 1 to 2 secs.

assuming hinged ends. )# calculations indicate a period of about 0.5 sec.

for two fundamental modes, one primarily vertical and the other primarily horiscatal, when the ends are fixed. These periods are about twice as long, or one sec., for hinged ends. Se maximum combined stress when both modes are excited is only slightly greater than the maximua stress for one of the modes.

For a period of 0 5 sec., and for the PG&E spectrum in Figure 1 of Amendment 8, for 0 5% damping, the displacement is of the order of 0.25 L

feet, and for twice this earthquake the displacement vill.be about 0 5 feet.

On this basis, it.can be estimated that the strains due to the earthquake I

respcmse are about one-third as great as those due to the -3 feet relative =

displacement.of the supports. Hence, under combined earthquake and relative.

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, displacement due to faulting, the pipe would be overstressed, but not beyond

three times the -yield strain.

It should be noted that' the dynamic displacement due to the postulated earthquake varies almost directly as the natural period in the range from about 0.h sec. to more than 3.0 secs. In other words, if the period.of the' pipe can be reduced, its displacement vill be decreased in the same pro.

'l portico. However, reducing the period of the pipe vould, in general, require j

an increase in stiffness which would cause difficulties in resisting the relative displacement of the ends.

Conversely, introducing flexible i

connections vill in general increase the period'.of the pipe which will increase.

the dynamic earthquake strains.

The final design of the piping should take the foregoing' considerations into account to insure that the piping can sustain both the earthquake

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vibrations and the relative fault motions without being overtrained.

It might be pointed out in this ' regard that the maximum displacement -

of the pipe,should it become inelastic in en earthquake,'vould probably not be different from the maximum displacement were the pipe to remain

'l elastic. Hence the pipe, under the most serious ceabination of conditions,

will be strained to about 3 times the elastic limit strain at yieldin's for the proposed material (under the combined effects of the fault motion and earthquake motion). Whether this is acceptable. depends on the det ails of 3

the final design. A possible means of reducing the stress. involves introduction of damping by artificial means. If dampers are used, care must be taken to avoid introducing additional disturbing forces. in the pipe when relative moticos of the ground or the containment structure take place.

All umbilical connections to the reactor contain=nt structure,.

including the main steam lines, should be designed to assure freedom from :

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< cmtact with other structures, valls, or earth and rock, by such a distance l

l as to provide.for the possibility of a three foot fault motion under the i

containment building and, in addition, the vibratory motion of the element l

considered. Also, all vital piping and other connectims amst be arranged in such a way that a three foot fault motion occurring elsewhere in the area vill not cause a failure of the vital element. The actual relative dis-placement in piping and other umbilical elements aar exceed three feet because of rotation and/or tipping of the contMnwat structure caused by the fault motion.

The main steam lines and similar irrportant lines should be designed I

to be locally stiffened by sleeves or doubler plates, at points where isolation valves or where anchors are attached, to prevent evalling or distortion of the lines that would impair their behavior.

SAFETY OF AUXILI ARY EQUIPMENT The auxiliary equipment contained within the reactor containment q

building vill, in general, move as a unit within tha containment structure.

The fault displacement of three feet for which provision is made does not i

produce a similar displacement within the structure, although it may produce a rotation or tilting of the containment structure. however, the equipment described in Amendment 8 and elsewhere in the applicatim can certainly be i

desig::ed for the slight tipping or tilting and rotation, provided it is i

not rigidly attached to items which move either a different amount or do not move at all.

It is stated.in Amendment 8 that "where vital ecmponents of the emergency systems are located within the turbine generator foundation of the control building, the inner-connscting piping and cable vill be designed l

to withstand up to three feet of relative displacement between the reactor l

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containment structure and the turbine generator foundation, or contro11 building." The provision of resistance to large relative displacement combined with resistance to oscillations.seems capable of achievement for

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relatively small diameter pipes, or for wires, although it is more: difficult for the 20-inch main steam lines.

l-SAFETY OF PRIMARY SYSTEM

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1 Comments have been made previously in this report regarding the main.

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steam lines and the difficulties involved in providing the.necessary resistance to relative motion and to earthquake vibrations.. The statement is made in Amendment 8 that "acceleraticos experienced by the primary.

system during such a displacement would be less than the accelerations used in the design of the equipment".

It is not clearly stated that the' accelerations experienced by the primary system during the maximum earth-quake would be less than the. acceleration used in the design of the. equip-ment. Moreover, it is not clear, if the relative motice of faulting should7 exceed three feet, whether there vill not be a greater maximum acceleratico than that provided during the earthquake, owing to a possible crashing.or l

l battering of the retaining valls outside the gap against the reactor l

containment structure. These could induce fairly large, but high l

fnquency, accelerations. Because of the large mass to be moved, the inertia of this mass, and the possible weakness of the valls. of the reactor I

containment structure against a localized line loading from outside, it is not clear at all that a relative movement of more than three feet could 1

be sustained without producing serious damage to the reactor containment-structure or serious accelerations to the primary system within 'it.

Nevertheless, since fault moticms greater than three feet are not considered credible, questieris of this sort need not be considered.

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. POSSIBM INTERRUPTION TO SUPPLY OF POWER The vulnerability of the overhead transmissica lines has not' been v

established. These lines cross the San Andreas fanit, and ~although they j

are supported on videly spaced towers, there is a possibility that _ ane or more of the towers may be displaced by as much as 20 feet relative to a_-

neighboring tower. It _is possible that the towers can sustain such a motion without loss of all of the lines. However, further study of this problem is desirable if it is necessary to depend on this source of power..-

Amendment 8 states, however, that if the external sources are unavailable, the engine generator, located within the reactor containment structure, vill be capable 'of handling the load required to shut down the plant safely.

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A further supply of power is available in the battery contained within the reactor containment structure and control building.

It must be regarded as possible that the main overhead transmission line would be severely impaired in its functioning where it crosses the main fault.

ABILITY OF STRUC'fURES AND EQUIPMENTS TO RESIST EARTHQUAKE OSCILLATIONS The procedure described for the design of critical and non-critical structures, cci pages 19-25 of Amendment 8, appears-in general to be satisfactory, with minor exceptions. On page 21, the second paragraph indicates that "the design of the plant vill be checked to assure that all critical structures, equipment and systems vill be capable of with-standing earthquake ground motions correspeding to spectrum...(values)...

g times as great as shown on Figure 1 vithout impairment of functions..."

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This means an earthquake of maximum acceleration of 0.67g, but not with 1

acceleration spikss ranging up to 1.0g.

The difference -is not important

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for items having periode-of vibration greater than about 0.5 sec., but it 1

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l can be substantial for elements having shorter periods or higher frequencies,

and the discrepancies becoms progressively larger as the frequency becomes

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higher or the period becomes lower. A clear and unequivocal statement about this point would be desirable.

In general, there is a reserve' margin in almost every element beyond a

the point at which yielding begins, even in items of equipment, control j

i rods, fuel assemblies, etc.

Dr. Housner's study'of the reserve capacity of i

structural elements, in Appendix II of Amendment 8, is sound. 'Nevertheless,

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for items of equipment which are not designed for yielding at all, but f

I which have to satisfy certain criteria such as. clearance or magnitude of j

displacement, it is essential to cuisider the higher spikes of acceleration in their design in order to provide the necessary reserve margin to assure l

operation of these items under the extreme maximum conditions.

j In this regard, it should be noted that the design spectrum in Figure 1

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is not quite as large as the values that correspond to the extreme peaks '

i of the El Centro spectrum. The values in Figure 1 are in general those that correspond to the mean of the oscillations for the rather jagged peaks l

I in the individual response spectrum curves for various earthquakes, j

i especially in the high frequency region.

An envelope through the spikes i

vould generally lie about a factor of 2 'above the smoothed spectrum, j

particularly for the 1ow values of damping. This is not regarded as an l;

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l important discrepancy, however, as there are indications that the mean j

of the oscillations in the spectrum is a much more significant value than the magnitude of the spikes.

Calculations and measurements that have been i

made and that are reported for equipment mounted en submarines, and 1

calculations for response of buildings.to earthquakes, in general 4

l indicate that the measured responses are more nearly consistent with the -

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. mean of the ' oscillations of the spectral values rather than with the peaks.

Hence appropriate smoothing of a design spectrum is a rational and l -

reasonable procedure.

e The accelerations transmitted to the' reactor containment structure

. will not exceed the acceleration that will cause sliding an the sand layer, which may be from 2/3g to 0.9g, depending on the characteristics l

- of the sand, until first contact is reached with the side of the cavity.

l Since this contact will occur after a three foot fault movement, or possibly slightly less' if some sliding occurs on the sand, a design level of 1.0g fer proper functioning of equipment should be used.

SUITABILITY OF PROPOSED DAMPING COEFFICIENTS he damping coefficients listed on page 23' of Amendment No. 8 appear 1

in general to be reasonable. The degree of precision implied in the l

selection of desping coefficients to two significant figures seems somewhat' l

unwarranted. However, the values are in general reasonable for the stress levels implied in the design of the individual elements, or for the con-diticms which are involved in their behavior. The damping for the reinforced cocente reactor containment structure would be considered high for a structure supported directly on the rock, but appears to be reasonable considering the fact that the structure is supported on a sand bed.

EFFECTIVENESS OF SAND LAYER IN CLIPPING' PEAK ACCELERATIWS In view of the comments on the behavior ~of the sand layer, it can be concluded that the sand layer will act to clip high peaks of horizontal acceleration that exceed its frictional capacity to transmit force to the reactor containment. structure. It will not clip vertical acceleration peaks.

. DETAILED DYNAMIC ANALYSIS OF EQUIPMl!3T 1

The method. described on pages 23 and 24 for handling the response of equipment within the building appears reasonable, although for sensitive items near the upper part of the building, the approximate method may. not be adequate. A detailed ~ dynamic ianalysis, such as described near the' bottom.

of 'page 24 will be desirable for all extremely sensitive and critical items of equipasnt.

The method cf analysis. described can take. into account the interactim with the reactor containment structure itself. However, the ground accelerations or grouad input moticca considered should. correspond-to the maximum postulated earthquake, and not the 0.33g earthquake for

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which Figure 1 of the amendment is drawn.

1 The. statement en page 3h implies that deuble the seismic loads corresponding to Figure 1 vill be' considered', but this does not take. into

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account the spikes of acceleration ranging up to lg for the higher frequency l

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I components. A further clarification of this point is desirable.

ADDITIONAL COMMENTS 1

The effect of the water in the annulus surrounding the reactor contain-l i

ment structure should not, in general, cause accelerations to be transmitted l

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directly to the structure th.*ough the water because of the fact that the water l

has a free surface. However, it would be desirable to have a study by the

i applicant or this problem to insure that the surging of the water will not

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introduce additional oscillations within the structure. This 'does not seem I

likely and it appears most reascnable to expect that the water catained in

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the annular space vill damp the motion.of the structure. Nevertheless, no f

specific data on this topic are available.

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' l In general, although questims have been raised about the treatment

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in certain aspects of the amendment, it is not believed that any of these questims involve problems that are not possible of solution within the range of currently available engineering knowledge.

It is my emsidered opinion that the structure and its equipment can be designed essentially as proposed to resist the effects of the maximum earthquake postulated.

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