ML20008D772

App 5D to Midland 1 & 2 PSAR, Load Factors & Load Combinations. Includes Revisions 1-36

ML20008D772
Person / Time
Site:	Midland
Issue date:	01/13/1969
From:	CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
References
NUDOCS 8007300665
Download: ML20008D772 (3)

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t APPENDIX SD IfAD FACTORS AND ICAD CCMEI'iATIONS Ihe Icai factors and lead ccnbinations in the dec'.gn criteria represent the consensus of the individual judgnents of a group tf Bechtel engineers and cnsultants who are experienced in both structura'. and nuclear pcVer plant design. Their judgent has been influe'nced by ct.rrent and past practice, i

by the degree of conservativeness inherent in the basic leads, and partic-ularly by the prcbabilities of coincident occurrences in the case of acci-dent, vind, and seismic leads.

i The - following discussions vill explain the justification for the individual factors, particularly as they apply to the reactor building.

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IEAD ICAD i

Dead load in a large structure such as this is easily identified and its effect can be accurately deter =ined at each point in the vessel.

Fcr dead load in ec=bination with accident and seismic or vind leads, a lead facter 3

representing a tolerance of 5 percent was chosen to acccunt for dead lead inaccuracies. ACI 318-63 allows _ a tolerance of plus 25 percent and =inus 10 percent, but the code was written to cover a variety of ccnditions where weights and configurations of =aterials in and on the structure may not be clearly defined and are subject to change during the life of the structure, v

LIVE IDAD-1 The live load that would be present along with accident, seismic, flood and l

vind 1 cads would produce a very small portion of the stress at any point.

Also, it is extre=ely unlikely that the full live load would be present over a large area at the the of an unusual occurrence. For these reasons, a lov load factor is felt' to be justified and live lead will be considered together with dead load at a lead factor 1.05 SEISMIC

- The design earthquake that has been selected is considered to be the strongest

. probable earthquake which could occur during the life of the plant. In addi-tion to the design earthquake, a =axi=um earthquake which defines the =ax1=u=

credible earthquake which could occur at the site is considered ~in design.

Class 1 structures are' designed so that no loss of function would result frc=

the =aximum earthquake. Cotequently, the probability of an earthquake caus-ing the =aximum credible accident is very small. For this reason, the~two events, seis=ic and accident, are considered together, but at =uch lover load facters than thes,e applied to the events separately. The earthquake load-facters of 1.25 and 1.0 are ecnservative for the design and nax1=u= earth-quakes in c0=bination with the factored loss-of-ccolant accident.

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j Inads are detemined from the design tornado vind speed. With the reactor l

buildings designed for this extre=e vind, it is inconceivable that the vind would cause an accident. Therefore, vind loads will not be considered with accident loads. A lead factor of 1.0 vill be applied to the tor. ado load to provide assurance of the structures perfer=ing satisfactorily.

ACCIDE'72 The design pressure and temperature are based on the operation of partial j

safeguards equipment using e=ergency diesel power.

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. Europ aa sure l$ practice has been to use a kad factor of 15 on the design pres-This factor is reasonat' and has been adopted for this design, i

. The probabilities of a max 1=um ar. dent occurring s1=ultaneously with a maximum vind or design earthqw, are very s=all; therefore, a reduced load I

factor of 1.25 is.used for thr; co=bination of events, i

In all cases the design te=perature is defined as that corresponding to the factored pressure. At 1 5 P the te=perature vill be sc=ewhat higher than the te=perature at P.

-It would be unrealistic to apply a corresponding 4

- te=perature factor of 1 5, since this could only occur with a pressure much greater than a pressure of 15 P.

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' (1) Refer to T. C. Waters.and N. T. Barrett, '" Prestressed Concrete Pressure i-Vessels for Nuclear Reactors," J. Brit nucl Soc 2,1963 i

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