ML20052C030
| ML20052C030 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, 05000000 |
| Issue date: | 04/26/1982 |
| From: | Tramm T COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 3987N, NUDOCS 8205040284 | |
| Download: ML20052C030 (4) | |
Text
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Commonwealth Edison ons First N:.tional PPrt Chic;go. Ilknois
' Addr:ss R: ply to: Post Offica Box 767 Chicago, Illinois 60690 April 26, 1982 Mr. Harold R.
Denton, Director d3 9
Of fice of Nuclear Reactor Regulation U.S.
Nuclear Regulatory Commission I
gg Washington, DC 20555 9*
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Subject:
Byron Station Units 1 and 2 Braidwood Station Units 1 & 2 6
s' M
Containment Stresses DN" 4 % g' f9 NRC Docket Nos. 50-454, 50-455 50-456 and 50-457
Dear Mr. Denton:
This is to provide additional information regarding the structural adequacy of the Byron and Braidwood containment buildings during inadvertent actuation of containment spray.
The review of this information should clos e Confirmatory Issue 17 o f the Byron Sa fety Evaluation Report.
Attachment A contains the results o f a refined structural analysis of a portion of the contalment building under a 3.5 psi negative pressure.
This is the analysis that was agreed upon with representatives of the NRC on January 28, 1982.
The analysis is consistent with our seismic reassessment because it used Regulatory Guide 1.60 seismic input and allowables based upon actual concrete strength.
The results of this analysis will be summarized in the FSAR at the earliest opportunity.
Please address further questions to this o f fice.
One signed original and fif teen copies o f this letter are provided for your review.
Very truly yours, ff? VA6"~
T. R.
Tramm Nuclear License Adminstrator QDDI 1m 5
/ I 3987N 8 2 o s o 4 o agt'ia
b 4 ~
ATTACHMENT A r
y ADDITIONAL'INFORMATION'RE0lP,STED ON RESPONSE TO UCR OUESTION 22.10 As'a result of'the submittal of calculations to the NRC' demonstrating the adequacy of the containment structure for 3.5 psi negative pressure,
- a. question arose with regard to the stress level in concrete at tne
-basemat wall junction.
It'was agreed in a meeting held on January 28, 1982 with the Nuclear Regulatory Commision, Commonwealth Edison Company.and Sargent and Lundy, that although the stress level in the concrete.was-high at this location the stresses would reduce if refinements in the analysis were considered.
A refined analysis for dead load and prestress load using the finite element program DYNAX has been performed.
The model used in the DYNAX analysis included finite elements to represent the behavior-of the basemat and the soil whereas the model used previously conservatively considered the containment wall fixed at the basemat.
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 flexibility of the basemat reduces the meridional moment due to dead load plus prestress by 12.41.
Seismic, thermal, soil, pressure and ground water loads were obtained
.from analyses performed using the fixed base model.
A reinforced concrete section analysis was then performed for the controlling load case number six, specified in FSAR Table 3.8-2, using the.
computer program:TEMCO.
TEMCO computes the affects of thermal and mechanical loads on a reinforced-concrete section considering cracking for thermal gradient.
This analysis considered 3.5' psi-Page 1 of 3 A
w
negative pressure and OBE based on the NRC RG 1.60 wide band input.
1The peak compressive stress from TEMCO is-3.47.ksi which is less than the allowable of'4.16 ksi considerin'g the as-built concrete strength o5 6935 psi and within 5% of the allowable considering the concrete strength specified for the design.; Furthermore, this peak occurs at only one azimuth and stresses are.within allowables elsewhere considering the specified design _ concrete strength for the OBE case and everywhere for the normal operating case.
The service combinations and allowables of the ASME Code Section III Division 2 are intended to insure the long term serviceability of the containment structure both in terms'of deflections and cracking.
The high calcul'ated 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 long term deformation will remain unchanged.
This high local concrete compression will have no impact on the strength and safety of the structure for pressure and carthquake loading wht_e capacity is controlled by the posttensioning tendons and the reinforcing-steel present.
The
- l containment is therefore considered adequate'for the 3.5 psi negative
, pressure postulated in NRC Question 22.10.
Page 2 of~3
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FEET ABOVE ELEV.'(F T.)
BASEMAT A
A 50 EL. 424'-0" 4,0 _
EL. 414'- O" n
EL. 4 0 4'-O" 30 _-
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EL. 394'-O "
20 __
10 EL. 384'-0" I
ROTATION FROIA l
BASEtAAT FLEXIBILITY ~
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\\T ' EL. 374'-O" i
i 1
300 200 10 0 O
-4 RADIAL DISPLACEMENT x 10 FT.
RADIAL DISPLACEMENT OF CONTAINMENT WALL DUE TO DEAD LOAD PLUS PRESTRESS -..
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