ML20063G446
| ML20063G446 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, 05000000 |
| Issue date: | 08/26/1982 |
| From: | Tramm T COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 4860N, NUDOCS 8209010007 | |
| Download: ML20063G446 (3) | |
Text
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N Commonwealth Cdison C ) one First Nitional Pitea. Chicago lihnois O~
Address Reply to: Post Office Box 76/
Chicago lilinois 60690 Augus t 26, 1982 Mr. Harold R. Denton, Director Of fice of Nuclear Reactor Regulation U.S.
tOclear Regulatory Commission Washington, DC 20555
Subject:
Byron Station Units 1 and 2 Braidwood Station Units 1 and 2 Containment Stresses NRC Docke t No s. 50-454, 50-455, 50-456, and 50-457-Re fe'rence (a):
April 26, 1982, letter from T. R.
Trama to H. R.
Dento n.
Dear Mr. Denton:
This is to provide additional information regarding the structural adequacy of the Byron /Braidwood containment buildings during inadvertent actuation o f containment spray.
NRC review o f this information should close Confirmatory Issue 17 of the Byron SER.
Attachment A contains a revised description of a refined structural analysis of a portion of the containment building under a 3.5 psi negative pressure.
Documentation of this analysis was provided previously in reference (a).
This information will be included in the FSAR at the earliest opportunity.
Please address further questions regarding this matter to this office.
i One signed original and fif teen copies o f this letter are provided for your use.
Very truly yours, i
ffh'usw l
T. R.
Tramm
[
Nuclea r Licensing Adminis trator 90l 1m l
Enclosure 4860N 8209010007 820826 PDR ADOCK 05000454 m
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REVT jION 1 -
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$ ADDITIONAL IMPORMATION REQUESTED ON RESPONSE TO !!CR QU1STIOb 22.10 o
As a result of the submittal of calculations to the NRC demonstrat-ing the a'dequacy of the containment structure for 3.5 psi negative pressure, a question! arose with regard to the stress level in con-crete at the basemat wall, junction.
It was agreed in a meeting held on January 28, 1982 with the Nuclear Regulatory Commission, Commonucalth Edison Company and Sargent and Lundy, that although the stress level in the concrete was high at this location th'e-stresses would reduce if refinements, such as cracking of the con-crete, were considere'd..
A refined analysis for dead load and prostressing using the finite element program DYNAX has been performed.
The codel used in the DYNAX analysis included the basemat and the soil where the model
,used previously, conservatively considered the containment wall fixed at the basematc A plot of radial displacement due to dead load plus prestress is attached and shows an inward rotation of the wall at the junction.
This deformation which results from the ficxibility of the basemat reduces the meridional moment due to dead load plus prestress 12.4%. 'A reinforced concrete section analysis was then performed for the controlling load combination IV, severe environmental, load case 6, specified in FSAR Table 3.8-3 using the computer program TEMCO.
TEMCO computes the effects of thermal and mechanical loads on a reinforced concrete section considering crackin~g for thermal gradient.
This analysis considered 3.5 psi negative pressure and OBE based on the NRC wide band input of RG 1.60.
N The peak compressive stress from TEMCO is 3.47 ksi, less than the allowable of 4.16 ksi considering the as built concrete strength of 6935 pr,i and within 5% of'the allowable considering minimum specified concrete strength. Furthermore, this peak occurs at only one azimuth and stresses are within allowables considering minimum specified concrete strength elsewhere for the OBE case l
and everywhere for the normal operating case.
The service conditions of the ASME Code Section III Division 2 are intended to insure the long term serviceability of the con-tainment structure both in terms of deflections and cracking.
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The high calculated compressive stress in the concrete under the transient OBE load combined with the short term negative pressure load will have no effect on serviceability as lor 5 term deformation will remain unchanged.
In fact reinforcing te:
2 stress and corresponding expected crack widths in this case u>.w small.
This high local concrete compression will have no impact on the strength and safety of the structure for pressure and earthquake loading where capacity is controlled by the post-tensioning tendons and the reinforcing steel present.
The con-tainment in therefore considered adequate for the 3.5 psi nega-
'tive pressure postulated in FSAR Q22.10.
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INITIAL ROTATION FROM l
BASEMAT FLEXIBILITY
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1 RADIAL DISPLACEMENT x 10'4 FT.
RADIAL DISPLACEMENT OF CONTA!NMENT WALL DUE TO DEAD LOAD PLUS PRESTRESS l
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