ML18005A933

Requests Addl Info,Within 120 Days,Re Seismic Design Consideration for Certain safety-related Vertical Steel Tanks,Per USI A-40

ML18005A933
Person / Time
Site:	Harris
Issue date:	06/01/1989
From:	Adensam E Office of Nuclear Reactor Regulation
To:	Eury L CAROLINA POWER & LIGHT CO.
References
REF-GTECI-A-40, REF-GTECI-SC, TASK-A-40, TASK-OR TAC-73096, NUDOCS 8906060191
Download: ML18005A933 (8)

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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 June I, l989 Docket No.

50-400 Mr. Lynn W. Eury Executive Vice President Power Supply Carolina Power 5 Light Company Post Office Box 1551

Raleigh, North Carolina 27602

SUBJECT:

SEISMIC DESIGN CONSIDERATION FOR CERTAIN SAFETY-RELATED VERTICAL STEEL TANKS (REQUEST FOR INFORMATION) (TAC 73096)

As a result of activities related to the technical reso'lution of Unresolved Safety Issue (USI) A-40, "Seismic Design Criteria,"

a preliminary determination 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) did not account for tank flexibility.

As a result, some large tanks were designed for significantly lower loads compared to current practice (Ref.

2 of the enclosure).

The Lawrence Livermore National Laboratory (LLNL), an I'IRC 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 with the observation of tank failures at non-nuclear facilities during past earthquakes (most recently at Coalinga, California in May 1983, in Chile in 1984 and in Mexico in 1985], the staff considers this a potentia11y significant 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 flexibilitywas considered in the seismic design of the Refueling Water Storage Tank and the safety-related Condensate Storage Tank/Auxiliary Feedwater Storage Tank at your facility as outlined in 890606019i 8'gI060i PDR ADQCK 05000400 P

PNU OF0/

II

the-enclosure to this letter, provide a

summary of the analyses sufficient to show how steps

a. through i. of the enclosure were considered.

and the results of these analyses.

2.

If tank wall flexibilitywas 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.

Oneoption may be to use the procedures developed by the Seismic qualification Utility Group (SHRUG) 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 recordkeeping requirements contained in this letter affect fewer than 10 respondents; therefore, OHB clearance is not required under Pub.

L.96-511.

Sincerely, iRonnie Lo/.for--;

Elinor G. Adensam, Director Project Directorate II-I Division of Reactor Projects - I/II Office of Nuc 1 l,ar Reactor Regu1 ation

Enclosure:

NRC Staff-Recommended Hethod for Seismic Analysis of Above-Ground Tanks cc w/enclosure:

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D),",', ll I I D.r I D Il I If ~ I "n C V ~ I l,lh.h r '3 II ~ V ~ V V D., h- ~ I" Dl I Mr. L. W. Eury. .Carolina Power 8 Light Company Shearon Harris CC: Mr. R. E. Jones, General Counsel Carolina Power 8 Light Company P. 0. Box 1551 Raleigh, North Carolina 27602 Mr. D. E. Hollar Associate General Counsel Carolina Power 5 Light Company P. 0. Box 1551

Raleigh, North Carolina 27602 Resident Inspector/Harris NPS c/o U.= S. Nuclear Regulatory Commission Route I, Box 315B New Hi 11, North Carolina 27562 Mr. R. A. Watson Vice President Harris Nuclear Plant P. 0.

Box 165 New Hill, North Carolina 27562 Mr. H. A. Cole Special Deputy Attorney General State of North Carolina P. 0. Box 629

Raleigh, North Carolina 27602 Nuclear Energy Pub'lic Information Committee c/o Triangle J Council of Governments P. 0.

Box 12276 Research Triangle Park, NC 27709 Regional Administrator, Region II U.S. Nuclear Regulatory Commission 101 Marietta Street Suite 2900 Atlanta, Georgia 30323 Mr. C. S. Hinnant Plant General Manager Harris Nuclear Plant P. 0. Box 165 New Hill, North Carolina 27562 Mr. Dayne H. Brown, Chief Radiation Protection Section Division of Facility Services N. C. Department of Human Resources 701 Barbour Drive

Raleigh, North Carolina 27603-2008

Enclosure NRC Staff-Recommended Hethod for Seismic Ana sis o 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 commonly used alternative of analyzing such tanks with rigid wall assumption (Ref. I) may be inadequate in some cases. The major problem is that direct application of this method is consistent with the assumption that the combined fluid-tank system in the ho} izontal impulsive mode is sufficiently r igid 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 and 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 lead to inadequate design loadings. The acceptance criteria below are based upon the information contained in References 1-4. These references also contain acceptable calculational techniques for the implementation of these criteria. a. A minimum acceptable analysis 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) mode of the fluid should be included in the horizonta 1 ana lysis. b. The frequency of fundamental horizontal 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 the fluid damping ratio should be 0.5X of critical damping unless a higher value can be substantiated by experimental results. e. The maximum overturning moment H at the base of the tank should be obtained by the modal and spatia( combination methods discussed in the SRP Section 3.7.2.II. The uplift tension resulting from H should be resisted either 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 NB must be shown to be 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. 1 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 MB. i. In addition to the above, consideration should be given to prevention of buckling of tank walls and roof, failure of connecting piping, and s Iiding of the tank.

References:

1.

"Nuclear Reactors and Earthquakes,"

TID-7024, prepared by Lockheed Aircraft Corporation and Holmes 5 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 1980.

3.

A. S. Veletsos and J.

Y. Yang, "Dynamics of Fixed-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.

May 30, 1989 DOCKET NO(S).

5O gOO Nr. Lynn M. Eury Executive Vice President Power Supply Carolina Power 5 Light Company PO Box 1 551 Rg)R/gh North Caro1ina 27602 SHEARON HARRIS PLANT DISTRIBUTION Docket=Fi=l e=

PDI I-1 Rdg File PAnderson

@Hen DBecker The fo1 1 owing documents concerning our review of the subject facility are transmitted for your informati on.

Noti ce of Receipt of Appl ication, dated Draft/Final Environmental Statement, dated Notice of Availability of Draft/Final Environmental Statement, dated Safety Evaluation Report, or Suppl ement No.

dated Environmental Assessment and Finding of No Significant Impact, dated Notice of Consideration of Issuance of Faci 1 ity Operating License or, Amendment to Facility Operating

License, dated Qgi-Weekly Notice; Applications and Amendments to Operating Licenses lnvolvin No'i gnificant Hazards Cons iderati ops, dated 05/17/89

[see page (s) ]

21 299 21322 Exemption, dated Con s tructi on Permit No.

CPPR-

, Amendment No.

dated

+ Facility Operating LicenseNo, A)endment No.

dated Order Extending Cons tructi on Completion Date, dated tr1onthly Operating Report for transmitted by letter dated Annual/Semi-Annual Repor't-

'ransmi tted by letter dated

Enclosures:

As stated Division of Reactor Projects I/II Office of Nuclear Reactor Regulation See next page osslcsII'V'AM~tr'AT Ktr

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