ML19094A280

Letter Regarding Review of Final Safety Analysis Report

ML19094A280
Person / Time
Site:	Surry
Issue date:	06/11/1970
From:	Newmark N Nathan M. Newmark Consulting Engineering Services
To:	Case E US Atomic Energy Commission (AEC)
References
Download: ML19094A280 (5)

Text

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N A T H A N M. N E W M A R K CONSULTING ENGINEERING SERVICES 1114 CIVIL ENGINEERING BUILDING URBANA, ILLINOIS 61801 Mr. Edson G. Case, Director Division of Reactor Standards U. S. Atomic Energy Commission Washington, D.C.

20545 Re:

Contract No. AT(49-5)-2667 11 June 1970 Surry Power Station Units 1 and 2 Virginia Electric and Power Company AEC Dockets No. 50-280 and 50-281

Dear Mr. Case:

Dr. W. J. Hall and I have reviewed the Final Safety Analysis Report for the Surry Power Station.

On the basis of our review we call attention below to certain items for which additional information is needed before we can complete our report.

It is possible that we may have additional questions following our inspection of the facility later this year.

1.

With reference to foundation conditions for the plant, the applicant is requested to provide a table, or figure, or both, which summarizes the types of foundation under each of the principal reactor structures.

(At the present time, from the figures in Sections 2 and 15 of the FSAR, it is difficult to ascertain in all cases the nature of the foundations for each of the plant structures.)

2.

Section 2.4.6 of the FSAR indicates that pile test data reports have been prepared.

We should like to examine these reports.

(We have previously requested through DRS that these be made available to us for review.)

1828

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3.

Table No. 2.4-5, Displacements Under Earthquake, 1 ists the expected displacement values (presumably horizontal) for the main facility structures under seismic excitation.

The applicant is requested to provide the basis for the numbers in this table, including a brief description of the manner in which the values were computed.

4.

Review of the underlying foundation media indicates a wide variety of materials including lenses of sands, silts, clay, etc.

In arriving at the foundation designs, was the consideration of a slight amount of tilt for some of the structures considered?

In the event that some slight degree of tilt occurs in one or more of the structures, is the design such that piping or other items connecting buildings will permit such movements?

5.

Figure 2.4-11, Ground Motion due to Earthquake, provides plots of relative vertical displacement V and horizontal displacement n in inches versus the distance in feet between centroids of areas of concern.

The presentation requires further explanation or example of the method of calculation.

It is not clear why Vis only 1/3 n whereas in the text it is stated to be 2/3 as great, and both ends move vertically as well as horizontally.

6.

A discussion of isolation design is given in Section 5.2.2 of the FSAR.

The valving apparently plays an important role in the isolation design described.

What seismic considerations were included in procurement or design of these valves?

Can seismic activity affect the operation of any of these valves which are critical for isolation?

7.

In Section 15.2.4, Seismic Design, it is stated that under the Design Basis Earthquake, .*. the allowable stresses do not exceed 90 percent of the certified minimum yield strength for structural steel, the capacity reduction factor, given in Section 15.5. 1.2, times the certified minimum

3 yield strength for reinforcing steel, and a capacity reduction factor times the specified strength for concrete.

Allowable soil bearing values are increased by one-half. With reference to the concrete stress, it appears that the margin of safety inherent in the:use of this value, in contrast to that for steel, may not be consistent.

Are there cases in which this concrete strength was the control] ing factor and if so under what conditions and for what items and locations was this the case?

8.

The dynamic analysis is described generally in Section 15.5. 1.4.

In order to assess the nature of the results obtained by using this analytic procedure, it would be helpful to have a tabulation of stress values in the containment structure for those stresses arising from earthquake loading, from dead load, from 1 ive loads and other sources; in this manner it should be possible to gain better information as to the relative magnitude of the stresses arising from the seismic excitation.

On page 15.5. 1.4-3 it is stated "this analysis demonstrated that the damping factors used for design and the resulting seismic response characteristics are conservative." The basis for this statement is not clear; elaboration is requested.

9.

On page 15.5. 1.8-2 the statement is made that for the Design Basis Earthquake the number of expected tremors is expected to be not more than 8 to 10 cycles and for the Operational Basis Earthquake not more than 4 to 5 cycles.

What is the basis for selection of these numbers?

More importantly, where in terms of plant design or safety were these numbers found to be of significance?

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10.

The design of piping for the nuclear steam supply system is described generally in Appendix B.

With regard to the approach described the applicant is requested to provide additional information on the method of seismic analysis used.

A comparison of some typical stress values arising from the various applicable loadings would aid in evaluating the margin of safety.

Also, how were the seismic loadings handled when yielding in the system occurred?

11.

With respect to piping that may be laid outside the plant between buildings or over distances in the ground, the applicant is requested to describe the methods that were employed to insure that the piping will survive the earthquake ground motions, and particularly at those locations where it enters or leaves buildings or joins up with other piping.

12.

Little information was found in the FSAR with regard to the design of the reactor internals for seismic loadings.

The applicant is requested to indicate how this analysis was carried out, and moreover whether horizontal and vertical excitation was considered in such design.

13.

With regard to design of critical items in the plant, as for example equipment, piping, etc., the manner in which the vertical earthquake excitation was handled should be described by the applicant.

In particular it is of interest to know whether a pseudo static coefficient was employed; if so, how it was determined; or whether a rigorous dynamic analysis was used.

It is important to learn whether the method used accounted for amplification of the type that would be expected for flexible systems.

14.

With regard to procurement and evaluation of critical items of control, instrumentation, valves, equipment, etc., the applicant is requested

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5 to provide information as to the types of criteria that were employed.

It would be helpful to have some examples to aid in the interpretation or the evaluation of the ability of such items to withstand earthquake excitation.

15.

The modal dynamic analysis for liquefaction described in the table at the bottom of p. 2.4.5-6 indicates a velocity of either 6. 1 or 8;3 in/sec., but does not indicate what acceleration of the surface was implied in or consistent with the calculations.

We should like to have this information, together with pertinent reference material.

Our recommendation for the PSAR was for a ground velocity of 9 in/sec. and acceleration of 0. 15g for the DBE, and we see no reason to reduce these levels now.

Respectfully submitted,

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N. M. Newmark bj p CC :

W. J. Ha 11