ML19224D795
| ML19224D795 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 07/10/1979 |
| From: | Hanecek R COMMONWEALTH EDISON CO. |
| To: | Oconnor P Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7907170055 | |
| Download: ML19224D795 (12) | |
Text
'
@ One First National Plaza. Chicago, lltinois Commonwealth Edison Address Reply to: Post Othce Box 767 Chicago, Illinois 60690 July 10, 1979
?/r. Paul O'Connor SEP Pmject !.!anager United States Nuclear Regulatory Connission
?lashington, D.C.
20555
Dear ?!r. O'Connor:
Attached are the answers to the concerns of Messrs. Segal and Cheng raised at the June 13, 1979 neeting in Chicago. ?ie have also attached the fol-lowing drawings:
Bechtel Drawings Title
- < 091 Reactor Enclosure-Equipnent Incation Plan EL5488-0"14-995 Reactor Enclosure-Equipnent Location Secticn A-A M-996 Reactor Enclosure-Equipnent Incaticn Section 3-B 12E-180 Reactor Enclosure-Equipnent Location Section C-C, D-D If you have any other questions concerning this natter please centact this office.
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I NRC concern regarding the calculation of local stresses in the j
spherical shell at the penetrations in the Sargent & Lundy report 1
(SAD-257) " Stress Report for Primary Containment Penetrations."
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i Resoonse The penetrations covered in this stress report are designed as per Sargent & Lundy Design Specifications K-4014, Attachment C, i
" Design Specification for Primary Containment Penetrations."
The local stresses in the spherical shell at the penetration attachment are calculated based on Welding Research Council Bulletin No. 107, " Local Stresses in Spherical and Cylindrical Shells due a
I to External Loadings," by Nichman, Hopper, and Mershon., The in following steps are used in calculating the local stresses r
i the spherical ~shell:
MI 1.
For the given applied forces and moments at the penetration attachment to the spherical shell, the stresses are calculated as per Table 3 (attached) of the Welding R'esearch Council Bulleting No. 107.
The stresses are calculated at locations A,
B,'C, and D around the hollow attachment to the shell, and are calculated at the outside surface, inside surface, and at the middle surface of the shell.
2.
The original stresses in the spherical shell (due to pressure and termperature) as calculated in the Chicago Bridge ~ E Iron Stress Report are then'added to the stress calculated from-above.
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the maximum allowable stress intensity of 3 Sm at any point across the thickness of the shell (primary plus secondary stress intensity), and the maximum membrane stress intensity of 1.5 Sm at the middle surface, where Sm is the design stress intensity in the shell.
The original ASME Boiler & Pressure vessel Code,Section VIII, 1956 Edition does not have the provision for allowables; therefore, allowables were taken from ASME I
Boiler & Pressure Vessel Code,Section III,1974 Edition.
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i NRC concern regarding the four slabs at elevation 548'-0" in the horizontal seismic model of the containment interior structures in SAD Report 261 " Seismic Analysis of the Reactor and Steam Drum Support Structure Inside the Containment".
Response
The four slabs modeled at elevation 548'-0" represent the four Nuclear Steam Instrumentation rooms and F.
W.
Control rooms at the four corners as shown in the attached Sargent & Lundy Drawing No. M-991 " Reactor Enclosure Equipment Location Plan El.
548'-0"".
Also Sections A-A, B-B, C-C. D-D are attached.
These sections indicate that the four slabs are not connected together as a single rigid slab.
The only connection among these four slabs is through the flexible shear walls as modeled in the horizontal slab-spring seismic model.
The seismic analysis of the containment interior structures presented in t AD Report No. 261 was done using the time history method of a alysis..
The 1940 El Centro earthquake recoras in the N-S, E-W, and vertical directions were modified such that the. response spectra generated from the modified time histories envelop the cite design spectra in the corresponding direction.
The detailed procedure ~for generating the design spectra-compatible time histories is given below.
For small damping, the response is very sensitive to frequencic; close to,the natural frequency of the oscillator, and it is reasonable to a
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assud's that the peak response is largely a function of the fre-t l
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3uency coraponents of the earthquake which are at or near the l
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This suggests that the relc-I
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tively j'agged response spectrum characteristic of an actual earthquake could be smoothed by locally adjusting the Foarier amplitude spectrum of the response time history..
'For a digitized earthquake record tabul'ated at points
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( is an integer, the computationally efficient fast Fourier trand-
, form algcrithm can be used to obtain the Fourier coefficients.
The following steps are involved in modifying an earthquake time history to match a desired spectrum.
l.
Find the ratio of the desired spectrum to the ccmputed spectrum of the earthquake.
r 2.
Compute the diccrete Fourier transform of the carthquake as defined by Equation 1.
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I It is important that the digitizing interval at b,e sufficiently small ishigherthanknyfrequency such that the folding frequency fg components actually present in the earthquake.
If this is not the g
will " fold" themselves into lower case, frequencies higher than ff frequencies.
This phenorenen is known as aliasing.
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Multiply the d v lues. computed in step 2 by.the ratio of the k
red spectrum '.
the computed spect' um at frequencies corras-c
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operationonlytheF$urieramplituddsaremodifiedwhilethe tt lags of the original earthquake are retained.
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ne; steps 1 to 4 using modified earthquake time history (1) in :.a:..
of the original time history.
The iteratica is stopped after a specified number of cycles or when the specified error in speccra match.s satisfied.
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NRC concern regarding modeling of o' tside supporting columns I
in the seismic analysis of the spherical containment'., SAD Report No. '167 " Feasibility Analysis of the Primary l Containment 7essel to Meet NRC Criteria".
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gsponse For axisym.etric loads (like dead load, snow load, LOCA p2. essure,
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flood. etc), the calumns were modeled as a cylinder of appropriate 1
thickness and' height to provide the same vertical and lateral I
stiffness effect as the columns.
But for seismic loads, the effect of columns has been neglected as they are not braced together.and thus were asrumed not con'.ributing towards the lateral stiffness significantly.
The sand around the sphere was modeled by the isotropic axisymmetric solid elements with the following ' properties 2
lbs-sec mass density = 3.7267 ft j
I Poisson's ratio =.35r 6
2 Modulus of Elasticity = 1.0 x 10 lbs/ft e
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