ML20011A537
| ML20011A537 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 03/06/1978 |
| From: | Sihweil I Office of Nuclear Reactor Regulation |
| To: | Parr O Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20011A456 | List:
|
| References | |
| NUDOCS 8110130531 | |
| Download: ML20011A537 (5) | |
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'N MEMORNADUM FOR:
Olan D. Parr, Chief Light Water Reactors Branch #3 Division of Project Management FROM:
I. Sibweil, Chief Structural Encineering Branch Division of Systems Safety
SUBJECT:
TECHNICAL ASSISTANCE REQUEST, DESIGN CRITERIA FOR SNUPPS PLANTS CONTAINMENT STRUCTURE (TAC No. 4820) (SEB:1165)
As requested in your letter dated Febrtlary 21, 1978, we have prepared the attached comments on the applicant's interpretation of PSAR commitments on design criteria for SNUPPS comtainments. Our position is the same as that stated in the January 23, 1978 meeting with the applicant.
/s4 d< ewe i-I. Sihweil, Chief Structural Enci,eering Branch Division of Syt.. ems Safety
Attachment:
As stated et-R. Mattson D. Yassallo J. Knight g.2c-$tremaker E. Licitra SEB Members
-8110130531 811007 PDR ADOCK 05000403 0
STRUCTURAL ENGINEERING BRANCH COMMENTS ON DESIGN CRITERIA FOR SNUPPS PLANTS CONTAINMENT STRUCTURE f
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In a letter to E. G. Case dated February 13, 1978, the applicant has submitted informaton in support of its contention that the re'nforcing steel cover for the concrete containment may be a minimum of 1-1/3 inches and a maximum of 11-1/2 inches. The basic issue is whether the minumum and maximum reinforcing steel cover specified by the code may oe altered by placement tolerances.
The applicant has presented the following arguments in support of its
- osition
(1) The design and placing drawings conform to the minimum and maximum cover requirements as specified in BC-TOP-5A which is referenced in the SNUPPS PSAR. These are the same re-quirements as specified in CC-3534 and CC-3535 of Division 2 of the ASME B & PY Code.
However, the applicant claims that the tolerances permitted by Section 3.8.1.6.6.1 of the PSAR allow variations in the minimum and maximum values.
(2) A reference to the ACI Commitee 224 Report has been cited that states "the cracking mechanism in two-way action slabs and plates is controlled... only to a small extent by the i
magnitude of the concrete cover". Furthermore, they note that the containment is prestressed which will minimize the potential for any significant crack opening.
(3) They have performed calculations in accordance with Reference 2 as cited in their letter that demonstrates that there will be sufficient bond development with a minimum cover of 1-1/3 inches.
(4) Imposit. ion of more stringent requirements will necessitate revisdon of the reinforcing steel detail drawings, thus forcing redesign of the containment.
The staff has reviewed the applicant's submittal and the referenced documents and has drawn the following conclusions:
(1) The minimum and maxic.am covers specified in BC-TOP-5A are controlling for both design and construction. _The specified cover should be appropriately modified to accommodate the placing tolerances stated in Section 3.8.1.6.6.1.
The staff notes that its position is consistent with a code interpretatior, made by the Working Group on Design of Section III, Division 2, of the ASME B & PY Code. As noted by the applicant, this interpretation was not supported by the SLbgroup on Materials, Construction and Examinaton and therefore has not been resolved within the code committee. However the staff feels that the Working Group on Design should have the jurisdiction on this matter.
2-(2) The applicant's ref erence to ACI Committee Report 224 does not present any conclusive eviderce regarding the absolute minimum cover requirements for corrosion protection. It is also noted that the same report states that for beams and one-way slabs "the thickness of the concrete cover is an important variable, but not the only geometric consideration".
(3) The applicant has not presented the calculations that demonstrate there will be sufficient bond development with a i
cover of 1-1/3 inches. Their conclusion does not appear to be consistent with the conclusion in Reference 2 which states:
" Comparison of current provisions for development length with the proposed design recommendations shows that for minimum cover current previsions are unconservative".
(4) The staff does not believe that its interpretation of the cover requirements will have a significant cost impact on the appplicant.
An increase in the specified cover may necessitate a drawing change, but it should not require a redesign of the containment.
If a change in the depth of a section is a concern, it could be accommodated by a tightening of the placing tolerances, it is noted that the applicant's placing tolerances are greater than those
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specified in both ACI 318-71 and ACI 349-76.
(5) The staff is also concerned that the aplicant's interpretation of cover requirements could result in [ cover as small as 1/2 inch for the mechanical connectors used with #18 bars.
' In conclusion, the staff's position is the same as that stated in the January 23, 1973 meeting with the applicant.
It is summarized as follows:
1.
The staff considers that the commitment of a 2-inch minimum concrete cover for the concrete. containment as made in Section CC-3533.1 of Appendix C to BC-TOP-5 for 46 tnrough #18 reinforcing steel to control design and construction. The value is a minimum meaning the absolute minimum cover to assure corrosion control in the actual constructior shall not be less than 2 inches. The staff expects for Callaway, Unit #1 that by wall lif t e6 611 rtqnforcing in sizes 76 :nrough #18 will meet this requirement.
2.
The staff considers that the commitment of a depth of not more than t/5 to reinforcing steel that is considered face reinforcement as made in Section CC-3534 of Appendix C to BC-TOP-5 to control design i
and construction. The value is a maximum as rounded to the reat whole
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3-inch, neaning the absolute maxinum depth in order to provide surface crack control for the concrete containment. The staff expects for Callaway, Unit #1 that by wall lif t #6 all face reinforcing will meet this raquirement. The staff will consider special cases on this
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reouirement where necesssary wall blockouts may require local variations to the maximum depth to face reinforcing.
3.
The staff considers items 1 and 2 to apply only to the concrete containment as indicated by the applicant's commitments. ACI 318-7.1 provisions as committed to by the applicant will govern requiremetns.
similar to these for the other Category I structures.
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