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UNITED STATES COVtRNMENT Memorandum To
- Files DATn: August 13, 1963 Clifford K. Beck FROM : Acting Director of Regulation SUBJEcr: DISCUSSIONS WITH PG&E ON EARTHQUAKE CRITERIA FOR BODEGA About July 24th Mr. Uhelchel of PG&E sent to me three copies of an informal memorandum containing earthquake criteria and ground motion assumptions which PG&E proposed to use in the structural design of the facility at Bodega. These criteria were sent pursuant to earlier discussions (Chicago meeting) held between '
l representative of PG&E and the Regulatory Staf f.
Mr. Whelchel l
desired to have informal reactions of the Regulatory Staff to the proposed criteria.
After a very brief study the informal documents, which had not j
been submitted as part of the record, were returned to Mr. Whelchel.
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In a telephone conversation between Mr. Whelchel and Dr. Beck j
several places in the informally submitted memo where there appeared j
to be inconsistencies, lack of clarity and incomplete infomation,
l were identified and discussed briefly. During the conversation I
Mr. Whelchel conveyed orally a very complete and explicit account l
l of the criteria which they had intended to submit.
Dr. Beck made notes of the proposed submission and later discussed this j
with the staff, but gave no indication to Mr. Whelchel as to the adequacy and acceptability of the proposed information.
During staff discussions a general belief developed that three j
items relating to the implementation of PG&E's proposed criteria might be necessary in addition to those included in PG&E's submission. These were:
a.
For critical structures where deflection or distortion could lead to impairment of function, even though stresa limits were not reached, extra design attention would be given to prevention of the deflection or distortion.
b.
Por equipment items of key importance to safety, where deterioration through continued service might occur, extra design attention would be required'.
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Memo to Files re Bodega ' 13 August 1963
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e For critical structures where stressing to the yield point alone c.
would cause impairment of function, even though ultimate stress levels were not involved, the extra design attention would be given to provision of mergins of safety up to the yield point, comparable to those which existed for ot).er structures beyond the yield point up to ultimate failure.
On August 5, in a brief telephone conversation between Dr. Beck and Mr. Whelchel, it was agreed that PG&E representatives would come to Bethesda on August 6th for an informal discussion of these criteria.
1 On August 6th Mr. Whelchel and four other representatives of PG&E, Dr. Beck, I
Dr. Mann, Dr. Bryan, Mr. Hadlock, Mr. Newell, Mr. Williamson of Holmes and Narver, and others, discussed the problem of structural criteria relative to earthquake ground motions which might be appropriate for the Bodega Head plant.
After considerable discussion there appeared to be general meetings of the minds of those present on a suitable definition of acceptable criteria to be used for l
structural purposes. Among other items, the following appeaved to be acceptable:
a.
The basic ground motion at Bodega which would be assumed as the basis of design for all critical structures would be an acceleration of 0.33 g together with normal working stresses in the materials of construction. More explicitly, the assumed acceleration would be equivalent to the spectra of Fig.10 app. 5 x 2.7.
This would be roughly equivalent, though not coincidental with 0.44 g at a stress level 1/3 higher than normal working stresses or.66 g at yield points.
j (b. At Chicago there was discussion of another set of criteria,.25 g for normal stress;.33 g for 1/3 over stress;.5 g for yield, end there was con-siderable indication of acceptability of this set; hence, the present consideration of the more recently proposed.33 g at working stress level represents an increase in the safety design margins of the plant.)
The lateral force factor which would be assumed as a basis for design c.
of each structure, item of equipment or system, will vary with the natural period and damping characteristics of that structure, item of equipmsnt or system.
d.
In addition to the basic ground motion criterion stated above, PG&E indicated their intention to make a cotanitment somewhat as follows:
In addition to the basic criterion of designing for structural stresses at the working level to result only from.33 g, the plant will be so designed that no hazardous release of radio-activity will occur, and all components cati be fully exercised to shut down the plant under stress of ground motion up to.66 g; for example, for particular items of equipment of key imp' rtance o
r to safety where deflection or distortion would impair function, the design we'uld also satisfy 0.66 g without deflection or distortion.
cc: Dr. Mann Mr. Lowenstein Dr. Bryan s
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