ML20244C574
| ML20244C574 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 06/08/1989 |
| From: | Michael Ray TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8906150028 | |
| Download: ML20244C574 (6) | |
Text
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y TENNESSEE VALLEY AUTHORITY CH ATTANOOGA, TENNESSEE 37401 SN 157B Lookout Place JUN 081989 U.S. Nuclear Regulatory Commission l
ATTN: Document Control Desk Washington, D.C.
20555 Gentlemen:
In the Matter of
)
Docket Nos. 50-327 Tennessee Valley Authority
)
50-328
.SEQUOYAH NUCLEAR PLANT (SQN) UNITS 1 AND 2 - NRC INSPECTION REPORT NOS.
'50-327/88-12 AND 50-328/88 RESPONSE TO UNRESOLVED ITEM (URI) 88-12-10 I
j During the NRC's inspection in Knoxville, Tennessee, the week of I
February 15, 1988,~several miscellaneous issues were reviewed as follow-up j
from previous NRC inspection items. The subject item, entitled " Seismic Analysis of the Steel Containment Vessel," resulted from deficiency D4.2-3 from the SQN Integrated Design Inspection (IDI) 50-327, 328/87-48.
TVA's March 2, 1988, letter to NRC provided additional information on the
)
steel containment vessel vertical response spectra and time step effect that l
was requested during the February 1988 inspection.
The additional information was based on a TVA evaluation of ten piping systems.
This additional information showed that the design basis accident load dominates the total sum of. loads and that the time step effect issue does not change the total pipe.
support loads by any significant amount.
Based on NRC's review of that letter, NRC issued URI 88-12-10, which was transmitted by S. D. Richardson's June 24, 1988, letter to S. A. White.
The enclosure provides TVA's response to URI 88-12-10.
The information provided in this response is supplemental to TVA's response to IDI item D4.2-3 that was transmitted by TVA's March 2, 1988, letter to NRC. TVA is available to further discuss this item at your convenience.
If you have any questions, please telephone B. S. Schofleid at (615) 843-6172.
Very truly yours, TENNESSEE VALLEY AUTHORITY eq k Manager, Nuclear Licensing and Regulatory Affairs L
Enclosure cc: See page 2 8906150028 890608 PDR ADOCK 05000327 I
(
Q PDC An Equal Opportunity Employer
r,.
..f 2-y U.S. Nuclear Regulatory Commission g g gg L
-cc (Enclosure):
Ms..S.-C.' Black, Assistant Director for Projects TVA Projects Division U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 1:
l Mr. B. A. Wilson, Assistant Director for Inspection Programs 1
TVA Projects Division-l --
U.S. Nuclear Regulatory Commission Region II b3 a
a, r a Sequoyah Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379
..3
ENCLOSURE 1 URI 88-12-10'
~
TITLE: SEISMIC ANALYSIS OF THE STEEL CONTAINMENT VESSEL ITEM DESCRIPTION
' TVA's review of steel containment vessel vertical response spectra for the
- time step. issue evaluated'the effects on a sample of piping systems attached to the affected structures including the reactor coolant loop. These samples were considered adequate for restart.
The staff considers that TVA should complete the evaluation of the remaining piping systems as a post-restart item."
RESPONSE
TVA's response to Integrated Design Inspection (IDI) Item D4.2-3 on the steel containment vessel (SCV) vertical respon-se spectra was submitted to NRC on December 29, 1987.
The response stated that, when the spectra were calculated using a smaller time step (0.005 second versus 0.01 second), the vertical spectra had shown increases over a limited frequency range at the vertical fundamental frequency of the SCV.
The response also stated that TVA would address the significance of this issue on the total pipe support load.
In our March 2, 1988, supplemental response to NRC TVA documented the results of the delta-T study on ten piping analyses that were presented to NRC during the February 15-19, 1988, IDI closeout reviews.
This evaluation is documented in Calculation N2-TSTEP-MISC, revision 0 (B25 880226 816).
The ten piping analyses reviewed included seven analyses previously evaluated for SCV vertical spectra changes in Calculation N2-PIR-8652-MISC, revision 1 (B25 871201 801), and three additional analyses chosen based on worst-case attributes in regard to the delta-T time step.
At the time that the concern was initially raised by NRC, it was agreed between TVA and NRC that the ten analyses evaluated for the SCV vertical spectra changes would be reevaluated for the delta-T time step issue.
However, three of these analyses did not have spectra changes, and NRC wanted to review analyses that were included in the interior concrete structure (ICS) and auxiliary building structure (ABS) in addition to the SCV attached piping.
Worst-case attributes (low allowable stress margins, modal frequencies in the region of spectra value increase, high contribution of seismic load and support qua11 fled to interim Criterion CEB-CI-21.89) were utilized in choosing three additional analyses that were-located in the ICS or ABS. One of the analyses evaluated in N2-PIR-8652-MISC, revision 1, was also noted to have several of the above-listed, worst-case attributes.
Table D4.2-3-1 of our March 2, 1988, supplemental response listed these four analyses and the worst-case attributes associated with each.
The_ remaining six analyses evaluated were considered to have worst-case attributes for the SCV vertical spectra change, which included low allowable stress margins, high elevation SCV rigid attachments, etc., as listed in Evaluation Package N2-PIR-8652-MISC, revision 1.
For the purposes of the delta-T time step evaluation, these six analyses were considered representative of the family of SCV attached piping analyses.
~
1,
The results of the ten piping analyses evaluation, as previously submitted by our March 2, 1988, supplemental response, showed that the delta-T time step change resulted in a general decrease in pipe stress for six of the analyses, L
with the remaining four exhibiting a negligible increase in stress. All ten analyses showed a negligible increase in penetration loads, support loads, and valve accelerations.
There was no change in nozzle loads for six of the analyses and a decrease in nozzle load for one analysis.
The nozzle loads for the remaining three analyses exhibited only a slight increase and met criteria requirements. A copy of the summary of the evaluation results, as previously submitted in our March 2, 1988, response, is attached.
This study has clearly demonstrated that the increase in pipe support loads because of the delta-T time step change is insignificant.
TVA has shown that the original design basis is adequate and that no safety issue exists.
Therefore, it is TVA's position that no additional evaluation for delta-T effects on the remaining piping systems is necessary.
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