ML20076G295
| ML20076G295 | |
| Person / Time | |
|---|---|
| Site: | Washington Public Power Supply System |
| Issue date: | 06/10/1983 |
| From: | Bouchey G WASHINGTON PUBLIC POWER SUPPLY SYSTEM |
| To: | Adensam E Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8306140612 | |
| Download: ML20076G295 (4) | |
Text
s Washington Public Power Supply System P.O. Box 968 3000 GeorgeWashingtonWay Richland, Washington 99352 (509)372-5000 Docket No. 50-460 June 10, 1983 Director of Nuclear Reactor Regulation Attention: Elinor G. Adensam, Chief Licensing Branch No. 4 Division of Licensing U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Subject:
NUCLEAR PROJECT N0. 1 ASME SECTION III, DIVISION 2 ADDENDA ARTICLES AND CODE CASES APPROVAL
Reference:
Supply System letter, G.D. Bouchey to Elinor G. Adensam, NRC same subject, dated June 6, 1983.
The referenced letter requested NRC approval of ASME Section III, Division 2, code cases and later code addenda articles as they relate to the design and construction of the WNP-1 Containment.
On June 8, 1983 we met with Messers Thadani, Chan and Rinaldi of the Staff to discuss the use of the code cases and later code addenda articles for the WNP-1 Project.
The attachment to this letter provides
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additional information requested by the Staff at this meeting relative to our request for approval of the use of Subarticle CC-3422.1, Winter 1977 Addenda, and Subarticle CC-3432.1, Summer 1979 Addenda.
In order to support the Supply System's efforts to N-Stamp the Containment, we would appreciate your formal reply by June 17, 1983.
G.D. Bouchey, Manager Nuclear Safety & Regulatory Programs (340)
GDB/AGH/cmh Attachment cc: MC Thadani, NRC MD-ll6 SP Chan, NRC MD-P 1022 ORM 847 I
8306140612 830610 0
PDR ADOCK 05000460 hth A
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I Docket No. 50-460 ATTACHMENT ASME Section III, Division 2, Winter 1977 Addenda-Subarticle CC-3422.1 Subarticle CC-3422.1 of the referenced Code (ASME Section III, Division 2 - 1975 Edition, including Winter 1976 Addenda), permits reinforcing bar yielding when the effects of thermal gradients through the concrete sections are considered; however, no upper limit for the maximum permissible strains in reinforcing bars under thennal loads were established.
Subarticle CC-3422.1.(1)(d) of the 1977 Winter Addenda of the Code prescribes 2 b as the maximum permissible y
net calculated tensile strains in reinforcing bars under loading conditions which inicude accident temperature, as thermal loads are secondary forces and self-relieving in nature.
The provision of CC-3422.1.(1)(b) of the Winter 1977 Addenda which allows strain in the tension diagonal rebars subjected to primary loads to exceed 0.9 was not applied to the WNP-1 Containment design.
The 2 [ limit for reinforcing bars under accident temperature conditions was applied only to reinforcing bars in flexure and in direct tension, and was not permitted in radial or peripheral shear reinforcing bars. This controlled yielding of reinforcing bars assures ductile behaviour of the Containment structure.
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In summary, CC-3422.1 of the Winter 1977 Addenda was used only to establish 2 has the upper strain limit for the previously identified reinforcing bars under accident temperature conditions, and to utilize the clarifications of the Code contained in CC-3422.1.(C)(1).
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1 ASME Section III, Division 2, Summer 1979 Addenda - Subarticle CC-3432.1 Subarticle CC-3432.1 of the reference Code (ASME Section III, Division 2 -
1 1975 Edition, including Winter 1976 Addenda) permits reinforcing bar stresses to be increased by one-third during the structural integrity test (test pressure = 1.15x maximum design pressure). This amounts to 40 KSI (30KSI +
1/3 x 30 KSI) for the 60 KSI reinforcing steel used in WNP-1. The Summer 1979 Addenda of the Code permits a one-half increase in allowable reinforcing bar stresses when the temporary pressure loads during the test condition are combined with other loads in the load combination.
This amounts to 45 KSI (30 KSI + 1/2 x 30 KSI).
The test pressure load condition is a temporary loading condition meant specifically for evaluating the adequacy of the structure with respect to quality of construction and materials and also for providing correlation with theoretically predicted response of the structure.
The actual reinforcing bar stresses during the test will be considerably lower than the stresses calculated for the test pressure load condition, due primarily to'the presence of the Containment liner. The Containment liner is anchored to the 1
concrete of the shell and dome.
Under internal containment pressure, the liner is always " expanded" into the shell and is' constrained such as to undergo l
compatible deformations. The liner, hence, is load sharing with the shell and represents a significant area of steel at a cross-section.
However, per the rules i
of the ASME Code, the liner cannot be considered as a strength element, for analysis l
whereas, in reality, it resists a significant portion of the pressure loads.
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l In the WNP-1 Containment design the liner has not been considered as a strength element. The additional 5 KSI stress increase permitted by Summer 1979 Addenda, as compared to the 1975 Code Edition, permits theoretical stresses in the rebars based on analysis to a maximum of 45 KSI, which is less than 60 KSI, the yield strength of the bar. The actual stresses measured in the reinforcing bars during the WNP-1 structural integrity pressure test was 25 KSI, compared to the 45 KSI acceptable value, due to the contribution of the liner, the actual inplace concrete strength being much higher than the assumed design strength and the actual thermal gradient through the concrete section being smaller than the design gradient.
Our reason for requesting the use of 45 KSI vs 40 KSI acceptable rebar stress values is to provide greater flexibility in the differential temperature between the outside and inside surfaces of the containment, during the pressure test.
This would permit the conductance of future pressure test during greater variation in weather (temperature).
In summary, the analysis for a given thermal gradient through the concrete section during test pressure conditions, not considering the liner as a st'rength element, may show reinforcing bar stress levels of 45 KSI, but in actuality, the rebar stresses would be lower due to the presence of the liner, and the inplace concrete strength being greater than the design strength.
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