ML20247M631
| ML20247M631 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 05/25/1989 |
| From: | Dick G, Hebdon F Office of Nuclear Reactor Regulation |
| To: | Withers B WOLF CREEK NUCLEAR OPERATING CORP. |
| References | |
| REF-GTECI-A-40, REF-GTECI-A-46, REF-GTECI-SC, TASK-A-40, TASK-A-46, TASK-OR NUDOCS 8906050093 | |
| Download: ML20247M631 (6) | |
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- WASHINGTON, D. C. 20555 May 25, 1989
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I Docket No. 50-482 Mr. Bart D. Withers President and Chief Executive Officer Wolf Creek Nuclear Operating Corporation Post Office Box 411 Burlington, Kansas 66839
Dear Mr. Withers:
SUBJECT:
SEISMIC DESIGN CONSIDERATE 01: FOR CERTAIN SAFETY-RELATED VERTICAL STEEL TANKS (REQUEST FOR INFORMATION)
As a result of activities related to the technical resolution of Unresolved Safety Issue (USI) A-40, " Seismic Design Criteria," a preliminary determicction has been made that a potential safety issue exists with regard to the ability of certain safety-related above-ground vertical liquid storage tanks at your facility to maintain their structural and functional integrity during postulated.
earthquake events. To make a final determination as to the safety significance of this issue, the NRC staff requests the information' identified below. The following is a brief description of the technical basis for the staff concern.
There has been a significant evolution in the seismic design practice for
- tanks.. In the past, the method used for tank analysis (Ref. I of the enclosure)
As a result, some large tanks were did not account for tank flexibility.
designed for significantly lower loads compared to current practice (Ref. 2 cf theenclosure). The Lawrence Livermore National Laboratory (LLNL), an NRC c
contractor, has estimated this difference to a factor of 2 to 2.5.
That is, the past design practice led to tanks being designed for loads that could be a factor of 2 to 2.5 less than current practice. The source of this factor is the amplification of spectra at typical tank frequencies. Coupling the above 1
with' the observation of tank failures at non-nuclear facilities during past eartNguakes(mostrecently},atCoalinga,CaliforniainMay1983,inChilein 1984 and in idexico in 1985 the staff censiders this a potentially significant l
safety issue.
In order to make a final determination on this issue, you are requested to provide within 120 days of receipt of this letter, the information identified below.
1.
.If tank wall flexibility was considered in the seismic design of the Refueling Water Storage Tank and the safety-related Condensate Storage Tank / Auxiliary Feedwater Storage Tank at your faci'aity as outlined in O
O 8906050093 890525
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PDR ADDCK 05000482 P
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May 25, 1989
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Mr Bart D. Withers the enclosure to this letter, provide a summary of the analyses sufficient to show how steps a. through 1. of the enclosure were considered and the results of these analyses.
2.
If tank wall flexibility was not considered as outlined in the enclosure i
to this letter for the above tanks, in view of the new information I
described above, provide the basis for continued confidence in the ability of the tanks to withstand the seismic event specified as a design basis for your facility. One option may be to use the procedures developed by the Seismic Qualification Utility Group (SQUG) under the resolution of USI A-46, " Seismic Qualification of Equipment in Operating Plants," to check the adequacy of the above-mentioned tanks for seismic events.
The reporting and/or recordkceping requirements contained in this letter affect fewer than 10 respondents: therefore, OMB clearance is not required under Pub. L.96-511.
Sincerely, Original signed by George Dick for Frederick J. Hebdon, Director Project Directorate - IV Division of Reactor Projects - III, IV, V and Special Projects Office of Huclear Reactor Regulation
Enclosure:
HRC Staff-Recc mended Method for Seismic Analysis of Above-Ground Tanks CC W/ enclosure:
See next page 7
DLSYRIBUTION
' Docket File NRC PDR Local POR PD4 Reading G. Holahan L. Rubenstein F. Hebdon P. Noonan D, Pickett OGC-Rockville E. Jordan B. Grimes ACRS (10)
PD4 Plant File GBagchi DOCUMENT NAf1E: VST FOR WOLF CREEK PD4/LQ PD4/PM fY D
PNoonanb DPickett:bj b
[ifHebdon 05/J3/89 05/p/89 05/,25/89
Mr. Bart D. Withers
. the enclosure to this letter, provide a suunary of the analyses sufficient to show how steps a. through 1. of the enclosure were considered and the results of these analyses.
2.
If tank wall flexibility was not considered as outlined in the enclosure to this letter for the above tanks, in view of the new information described above, provide the basis for continued confidence in the ability of the tanks to withstand the seismic event specified as a design basis for your facility. One option may be to use the procedures developed by the Seismic Qualification Utility Group (SQUG) under the -
resolution of USI A-46, " Seismic Qualification of Equipment in Operating
' Plants," to check the adequacy of the above-mentioned tanks for seismic events.
The reporting ard/or recordkeeping requirements contained in this letter affect fewer than 30 respondents; therefore, OMB clearance is not required under Pub. L.96-511.
Sincerely, u
rLFrede ck J. Hebd6n, Director Project Directorate - IV Division of Reactor Projects - III, IV, V and Special Projects Office of Nuclear Reactor Regulation
Enclosure:
NRC Staff-Recommended Method for Seismic Analysis of Above-Ground Tanks cc w/ enclosure:
See next page
s
. t-:
Mr.'Bart D. Withers Wolf Creek Generating Station
- Wolf Creek Nuclear Operating Corporation Unit No. I cc:
. Jay Silberg, Esq.
Mr. Gerald Allen Shaw, Pittman, Potts & Trowbridge Public Health Physicist 1800 M Street,~NW Bureau of Air Quality & Radiation Washington, D.C.
20036-Control Division of Environment Chris R. Rogers, P.E.
Kansas Department of Health Manager, Electric Departar.ent and Environment.
Public Service Comission Forbes Field Building 321 P. O. Box 360 Topeka, Kansas 66620 Jefferson City, Missouri 65102 Mr. Gary Boyer, Plant Manager Regional Administrator, Region III Wolf Creek Nuclear Operating Corp.
U.S. Nuclear Regulatory Comission P. O. Box 411 799 Roosevelt Road Burlington, Kansas 66839 Glen Ellyn, Illinois 60137 Regional Administrator, Region IV Senior Resident Inspector / Wolf Creek U.S. _ Nuclear Regulatory Commission c/o U. S. Nuclear Regulatory Commission Office of Executive Director-P. O. Box 311 for Operations Burlington, Kansas 66839 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011-
- Mr. Robert Elliot, Chief Engineer Utilities Division Mr. Otto Maynard, Manager Licensing Kansas Corporation Commission Wolf Creek Nuclear Operating Corp.
4th Floor - State Office Building P. O. Box 411 Topeka, Kansas 66612-1571 Burlington, Kansas 66839 Office of the Governor State of Kansas Topeka, Kansas 66612 Attorney General 1st Floor - The Statehouse Topeka, Kansas 66612 Chairman, Coffey County Commission l
Coffey County Courthouse
,Burlington, Kansas 66839 i
i I
l 1
Enclosure NRC Staff-Recorrended Method for Seismic An'alysis of Above-Ground Tanks Most above-ground fluid-containing vertical tanks do not warrant sophisticated, finite element, fluid-structure interaction analyses for seismic loading.
However, the commonl assumption (Ref.1) y used alternative of analyzing such tanks with rigid wall may be inadequate in some cases. The major problem is i
that direct application of this method is consistent with the assumption that the combined fluid-tank system in the horizontal impulsive mode is sufficiently rigid to justify the assumption of a rigid tank. For the case of the flat-bottomed tanks mounted directly on their bases, or tanks with very stiff skirt supports, the assumption leads to the usage of a spectral acceleration equal to the zero-period base acceleration.
Recent evaluation techniques (Ref. 3 end 4) have shown that for typical tank designs the frequency for this fundamental horizontal impulsive mode of the tank shell and contained fluid is generally between 2 and 20 Hz. Within this regime, the spectral acceleration is typically far greater than zero-acceleration. Thus, the assumption of a rigid tank could leed to inadequate design loadings.
The acceptance criteria belcw are based upon the information contained in References 1-4 These references also contain acceptable calculational techniques for the implementation cf these criteria.
a.
A minimum acceptable aralysis should incorporate at least two horizontal modes of combined fluid-tank vibration and at least one vertical mode of fluid vibration. The horizontal response analysis should include at least one impulsive mode in which the response of the tank shell and roof are coupled together with the portion of the fluid contents that moves in unison with the shell. Furthermore, at least the fundamental sloshing (convective)modeofthefluidshouldbeincludedinthe horizontal analysis, b.
The frequency of fundamental horizcntal impulse mode of the tank and the fluid system should be estimated.
It is unacceptable to assume a rigid tank unless the assumption can be justified. The horizontal impulsive-mode spectral acceleration is then determined using this frequency of fundamental horizontal impulsive mode and tank-shell damping. The maximum horizontal spectral acceleration associated with the tank support at the tank-shell damping level may be used instead of determining frequency of fundamental horizontal impulsive mode.
{
c.
Damping values used to determine the spectral acceleration in the impulsive mode should be based upon the values for tank shell material as specified in the current SRP Section 3.7.1.
d.
In determining the spectral acceleration in the horizontal convective mode i
the fluid damping ratio should be 0.5% of critical damping unless a higher value can be substantiated by experimental results.
4 2
e.
The maximum overturning moment M at the base of the tank should be n
obtained by' the modal and' spatial combination methodi; discussed in the SRP Section 3.7.2.11.
The uplift tension resulting from M should be resisted cither by tying the tank to the foundation with a$chor bolts, etc., or by mobilizing enough fluid weight on a thickened base skirt plate. The latter method of resisting N must be shown to be B
conservative f.
The seismically-induced hydrodynamic pressures on the tank shell at any level can be determined by the modal and spatial combination methods in the SRP Section 3.7.2.
The hydrodynamic pressure at any level should be added to the hydrostatic pressure at the level to determine the hoop tension in the tank shell.
g.
Either the tank top head should be located at an elevation higher than the slosh height above the top of the fluid or else should be designed for pressures resulting from fluid sloshing against this head. The method in current design codes for calculating slosh height is not necessarily conservative.
Formulas given in Ref. I can be used to calculate slosh height, h.
The tank foundation (see also SRP Section 3.8.5) should be designed to accommodate the seismic forces imposed by the base of the tank. These forces include the hydrodynamic fluid pressures imposed on the base of the tank as well as the tank shell longitudinal compressive and tensile forces resulting from N
- B i.
In addition to the above, consideration should be given to prevention of buckling of tank walls and roof, failure of connecting piping, and sliding of the tank.
References:
1.
" Nuclear Reactors and Earthquakes," TID-7024, prepared by Lockheed Aircraft Corporation and Holmes & Narver, Inc.,
for the Division of Reactor Development, U.S. Atomic Energy Commission, Washington, D.C., August 1963.
2.
D. W. Coats, " Recommended Revisions to Nuclear Regulatory Commission Seismic Design Criteria," prepared by Lawrence Livermore National Laboratory for the U.S. Nuclear Regulatory Commission, NUREG/CR-1161, May lii?0.
3.
A. S. Veletsos and J. Y. Yang, " Dynamics of Fsxed-Base Liquid-Storage Tanks," U.S.-Japan Seminar for Earthquake Engineering Research with Emphasis on Lifeline Systems, Tokyo, Japan, November,1976.
4.
A. S. Veletos, " Seismic Effects in Flexible Liquid Storage Tanks," Proceedings of Fifth World Conference on Earthquake Engineering, Rome, 1974.
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