ML20077D796
| ML20077D796 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 05/31/1991 |
| From: | Wallace E TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9106050180 | |
| Download: ML20077D796 (5) | |
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Tennessee vaney Authonty. Itci Market si cet. Cnattanx9a Tennessee 3no2 MAY 31391 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.
20555 Centlement in the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 SEQUOYAH NUCLEAR PLANT (SQN) - STEEL CONTAINMENT VESSEL RESPONSE SPECTRA -
NRC INSPECTION REPORT NOS. 50-327/90-18 AND 50-328/90-18 The purpose of this letter is to provide information verbally requested by the NRC staff relevant to the subject inspection. The additional information provided in the enclosure addresses SQN's use of-leak-before-break methodology _for developing the basis for the design basis accident spectra for the steel containment vessel (SCV) for use_in the design of attachments to the SCV.
No commitments-are contained in this' submittal.-.Please direct questions concerning this issue to W. C. Ludwig at (615) 843-7460.
.Very truly yours, TENNESSEE VALLEY AUTHORITY W
E. G. Wallace, Manager Nuclear Licensing and Regulatory Affairs Enclosure cut See page-2 l-[
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2 U.S. Nuclear Regulatory Commission MAY 311991 1
1 cc (Enclosure):
Ms.-S, C. Black, Deputy Director Project Directorate 11-4 l
U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike 4
j Rockville, Maryland 20852 Mr. D. E. LaBarge, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike 4
Rockville Maryland 20852 i-NRC Resident' Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379 4
Mr. B. A. Wilson, Project Chief 4
U.S. Nuclear Regulatory Commission Region II j
101 Marietta Street, NW, Suite 2900 Atlanta, Geor6 a 30323 1
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ENCLOSURE DESIGN BASIS FOR STEEL CONTAINMENT VESSEL (SCV) DESIGN BASIS ACCIDENT (DBA)
SPECTRA The following describes the basis for the DBA spectra being utilized for the SCV at Sequoyah Nuclear plant (SQN). These spectra reflect the dynamic response of the SCV to-local pressurizations occurring as a result of postulated high energy pipe breaks within the containment lower compartment.
They are not used in the structural design of the SCV itself,-but rather in the calculation of loads on commodity supports attached to the SCV.
previously, the DBA spectra were calculated using mass and energy releases from double-ended guillotine breaks in the primary loop piping.
These breaks have subsequently been eliminated through application of leak-before-break technology as documented in Reference 1 and approved by NRC in Reference 2.
The revised spectra were generated using double-ended breaks, which represented the largest remaining potential umss and energy releases.
Elimination of the primary loop breaks from consideration was based upon supplemental information published by the NRC staff in Reference 3.
The revised DBA spectra for the SCV were generated as follows.
pipe Break The containment design basis high energy pipe breaks (doublo-ended guillotine) used in this analysis are documented in References 4 and 5.
The specific breaks and break locations were excerpted from Reference 6 and are listed and graphically depicted on the attached sketch. Reference 7 describes the criteria used in performing-the break identification and location process.
The following high aversy lines were considered (see attached figure):
Main Steam Line Main Feedwater Line (enveloped by Main Steam) pressurizer Surge Line (2 breaks analyzed)
Residual Heat Removal Suction Line Accumulator Discharge Lines (4 breaks analyzed)
These lines were determined to represent the' largest remaining mass and energy releases within the lower compartment. Multiple break locations wore individually considered where appropriate and the associated mass and energy releases were assumed to occur in subcompartments that provided the highest pressurization rate for adjacent areas of the shell.
Existing break locations were selected that were physically located in various areas of the lower compartment in order to maximize the calculated response.
Spectra Ceneration In calculating the SCV response to these postulated high energy pipe ruptures, it was necessary first to calculate the local subcompartment pressurization effects of each break.
The containment subcompartment model used is discussed in Chapter 6 of _ the SQN _ Updated Final Safety Analysis Report and shown in Figures 6.2.1-9 through 6.2.1-12.
The umss and energy releases from each individual break were analyzed and pressurization time histories generated for each containment subcompartment by Westinghouse Electric Corporation using the TMD code described in heforence 8.
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The local pressurization time histories for each subcompartment-adjacent to the SCV shell were~ used to calculato local pressure loading time histories.
These were then input to an axisymmetric ANSYS nedal of the-SCV,~and the SCV dynamic response was calculated for each individual break.
The resulting
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response spectra for the SCV were then enveloped for the selected break
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4 locations. In this manner, an overall SCV dynamic response-was determined for i
use in attachment design.
in summary, the-SCV DBA-responses resulting'from enveloping the local effects.
i of dynamic pressurizations from multipleLindividual breaks into a single I
l conservative response will be used for the design-of SCV attachments.
In j
accordance with strictures' contained in, Reference 7. global pressurization and t
temperature effects from previously-postulated double-ended guillotino breaks r
of the primary loop piping are conaldered in.the design of:the SC7.
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References:
1.
Letter, R. Cridley to WRC, " Elimination'of: Primary Loop Pipe 4
j Breaks," dated March 30, 1989
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2.
Letter from Suzanne Black to 011verLD. Kingsicy dated
-July 19, 1989,1 transmitting Safety Evaluation Report for
" Elimination of Postulated-Primary Loop-Pipe; Ruptures"-
3.
Federal' Register, Volume 53, Number 66, page~ 11311, dated April 6.-1988 j
4 4.
WCAP-12122, " Containment Subcompartment Analysis Utilizing Leak-Before-Break Technology for=Sequoyah Units ~l~andL2 " 1989 3
5.
WCAP-12121. " Detailed Computer Results for the1 Containment' Subcompartment'AnalysisLUtilizing Leak-Before-Break Technology for Sequoyah Units 1 and'2," 1989-g
-6.
Report CEB-76-3, " Protection Against Dynamic' Effects-of Pipe Failure Inside' ContainmentL and the Main Steam Valve' Rooms,*'
-Revision 0<
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.7.
SQN'FSAR Section[3.6, " Protection Against EffectsLAssociated' 4
With 'the Postulated Rupture.of Piping," and. Section.6.2,.
" Containment' Systems" I
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WCAP-8077, " Ice Condenser Coatainment Pressure.TransientL Analysis," March.1973 W
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Break i
Location 3:eak Desc:1-tplon 1
P2R Surge Line at.the Pressurl:er-2 P R Surge Line at the Loop 2 Hot Leg 3-RRR Suction Line at the' Loop 4. Hot Lag.
4 Accumulator Discharge Line at the Loop.l' Cold Leg 5
Accumula to: Discharge Line at the Loop 2 Cold-Leg-6 Accumulate: Discharge Line at~ the Loop 3 Cold Leg 7
Accumulate: Disch'arge - Line at the
. Loop 4 Cold. Leg-8
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Main Steam Line at the -Loop '4 ~ SG
- Hain Feedvater Line at~the Loop,4-sc-
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