ML19326B257
| ML19326B257 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 07/30/1976 |
| From: | Stolz J Office of Nuclear Reactor Regulation |
| To: | Rodgers J FLORIDA POWER CORP. |
| Shared Package | |
| ML19326B243 | List: |
| References | |
| NUDOCS 8003120800 | |
| Download: ML19326B257 (9) | |
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Docket File ELD m30 197 6 NRC PDR IE (3)
Local PDR H. Smith LWR #1 File I. Sihweil R. C. DeYoung F. J. Williams C. Tan R. Shewmaker J; Stolz L. Berratan L. Engle R. Lewis (IAE, Region 2)
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Docket !!o. 50-302 T. Abernathy, TIC Florida Power Corporation ATTH: Mr. J. T. Rodoers Assistant Vice President P. O. Box 14042 St. Petersburg, Florida 33733
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Gentlemen:
This letter is a follow un to a telephone conversati and Mr. L. Engle (fRC) regardinn the flRC staff's review and O)
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evaluation of your interim report, " Reactor Cuilding DonaThe staff's co 11, 1976.
Delamination", Junefor infomation concerning the above report were teleco you on the same day as the July 7,1076 telephone call.
Enclosed you will find the staff's conments and requasts for infomation as telecopied to you at that time.
l In a telephone call on July A,1976 between "r. J. T. Rodgers and Mr. L. Engle, it was agrred that your response to the staff's request for information concernino the interin report should be sent.o the staff no later than August 6,1976.
The many subsequent communications with you concerniner your investications and status of the corrective fix for the concre separ n ton on the reactor building done now indicate you should arend your June ll,1976 report regarding the staff's specific requests for infomation concerning this document.
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JUL 3 0 1'976 Because of the constantly changing status on these r'atters, wo request that you neet with the NRC staff as soon as possible in early August,1976 to update the staff on your investigations, findings, and the present status of your corrective fix concerning the concrete separation in the Crystal River, tinit 3 reactor buildino dome. At that time, we can discuss your plans for a new interim report on this problem.
Please call us if you have any questions concerning these matters.
Sincerely, Original Signed by John F. Stolz John F. Stolz, Chief Licht Water Peactors Franch ?!n.1 Division of Pro. ject fianagement
Enclosure:
Staff Cor:inents and q
Requests for Infomation cc: ftr. S. A. Brandimore Vice President and General Counsel P. O. P.ox 14042 St. Petersburg, Florida 33733
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ENCLOSURE 1 C(NMENTS AND RE0 VESTS FOR INFORMATION REACTOR BUILDING DOME DELAMINATION INTERIM REPORT FLORIDA POWER CORPORATION CRYSTAL RIVER, UNIT 3 DOCKET NO. 50-302 O
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COMMENTS ON CRYSTAL RIVER UNIT NO. 3 iJ REACTOR BUILDING DOME DELAMINATION INTERIM REPORT k, i GENERAL i
1.
For easy reference, provide a list of tables and figures in the l
Table of Contents.
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SECTION 1.2
'pues 1.
The staff considers the establishment of the causes of t!:e dome de-lamination to be important in assessing the adequacy of the repair 4
program and in providing assurance th'at another crack will not occur again during the l'ife of the structure. The potential contributing factors should, therefore, be identified indicating the magntiude of Y
radial tensile stresses created in the concrete.
l 2.
The use of radial anchors will enhance the capability of the dome to 3
resist radial tension. However, they will not eliminate tension in concrete, and therefore small cracks may still exist.
Provide an analysis to indicate tha,t such cracks will, not jeopardize the required m
17 structural integrity of the dome to resist all combinations of loadings g
for which it is designed.
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SECTION 2.3 AND TABLE 2-2 1.
Clarify the definition of tensile capacity of concrete. Explain how T. !
principal tension is related to shear and diagonal tension as indicated
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e in Section 2.3.1,.and what is the difference between the shear discusse
' '. I in this section and that in the next section (2.3.2).
.h 2.
Provide and describe with examples of actual design, the conditions J,
under which each of the criteria (a) and (b) in Section 2.3.1 is appliec i
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3.
Since the stress / strain distribution is tri-axial, the limits of
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3 [ff and 6[ff may not be directly applicable to this problem and their use should be justified.
4.
If 0.85ff as extreme compression in ultimate strength design is
's used, it may not! be directly applicable for the same reason as in the above coment and should be justified.
5.
The shear strength of concrete is influenced by stresses orthogonal to the axis of the element; therefore, this effect should be considered.
SE qION 2.4 1.
In the paragraph in the middle of Page 2-4, you indicated that for structural integri,ty test and accident condition load combinations, stresses for sustained loads cannot be combined with those due to rapidly applied loads internally in the program and are combined externally. Provide an example of actual design to show how the stresses are combined externally and illustrate the combination on a stress-strain diagram.
2.
On Page 2-5. under Item b. Creep, it is indicated that as a result of concrete creep there is a'Veduction in concrete stress and an in-crease in liner stress. Since the liner is relatively thin and may buckle under prestress, the liner should not be considered to con-tribute any strength to the containment vessel.
However, in the design of the steel liner, strain due to creep of concrete should,be considered to check its leaktightness integrity.
Revise the concrete stresses in the report if they have been reduced.
3.
Provide the procedure which you used in the design of the steel liner.
In Table 2-2, you stated that no criteria'on liner strains were used in the original design.
Indicate the criteria you used for the steel liner design.
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4.
Discuss in detail the effects of creep, including the following consideration :
Because of the different level of prestress in the wall in the vertical direction, the wall in the hoop direction, in the ringgirderandinthedometheE;isdifferentinallthese directions and this effect should be considered in the analysis.
The wall acts as an orthotropic element. The different parts of thestructurehavesimultaneouslydifferentEjduetodifferent specific creep.
5.
In Table 2-3 add load combination equation for repairs. This equation 4
should include the, seismic load tenn.
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.SECTION 3.1
\\U 1.
Discuss the re. liability of direct tensile tests performed on cores.
Since in the structure the radial tensile stress occurs simultaneously with two orthogonal compressions or with two orthogonal tensions, a more thorough investigation is required.
l Section 3.3 1.
In the list of. factors which may have contributed to the delamination problem, ad'd: creep and stress concentrations (at tendons) inherent in this type of structure.
2.
In Sect'on 3.3.2 it is indicated that by using SAP IV computer pro-gram an the model shown in Fig. 3-16, the effects of material properties on radial tension stresses are evaluated.
Identify in the model:
(1) the steel elements, such as reinforcing steel, and tendon
- conduits, (2) the manner in which the prestressing force is applied, indi-
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cating if the prestressing force component tangent to the dome curvature is considered.
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3.
Provide the hand calculation which you made to obtain the radial i
tension.
4.
In Section 3.3.4, transient themal gradients may generate shear stresses, and should be considered in the analysis. Similar effect exists for localized themal gradients.
5.
The solution for stress concentrations as shown in Fig. 3-17 & 3-18 is incomplete.
It should be noted that compression exists also in the direction parallel to the conduit (d'y). This stress generates additional stress concentration in the plane (4'I #'3) orthogonal to 2
i the tendon, which should be added to the stresses.shown in Fig. 3-18.
6.
When the effect of tendon conduits is analyzed, it should be noted that this effect 1.s different when evaluated in the direction parallel to the tendon and orthogonal to the tendon.
In the direction parallel to the tendon a k" thick pipe (5"$) approximately replaces the removed O
concrete.
But in the direction perpendicular to the tendon, the pipe introduces a flexible link which modifies the average properties of the ' concrete section.
SECTION 4.4 1.
In Sections 4.4.1 and 4.4[f'you indicated that in order to consider the containment structure serviceable for the two loading conditions the shear capacity of the tendon conduit would have to be considered.
Such consideration may not be possible, unless the bond stress between the conduit and concrete can be justified to be adeouate.
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SECTION 5.3 f
1.
In releasing the prestressing force as a result of tendon detensioning, strain recovery will occur. However, most likely the strain recovery
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in concrete will be resisted by the' steel reinforcing bars and steel liner, because of creep effects, and tension may result in the concrete.
Provide an analysis to show that the resulting cracking in dome concrete will not jeopardize the structural integrity of the dome particularly in V
the region of the liner anchors.
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2.
The behavior of the detensioned dome is strongly influenced by tte creep of the prestressed structure which har. taken place after pre-stressing and up to this date. The detensioning of the dome will
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not return the structure to a previously unprestressed state, what-ever the sequence of operations.
It is therefore imperative to analyze the detensioned dome for the influence of creep. Present such an analysis and demonstrate that the integrity of the detensioned dome will not be impaired. The analysis should include the ring girder and the top of the cylindrical. wall.
3.
The figures 5-11 to 5-14 do not include a study on shears. Provide a detailed analysis of shear stresses in the detensioned dome and demon-strate that these shear stresses, acting simultaneously with normal stresses, do not e'ndanger the stability of the dome.
Special attention should be given to radial shears, f
4.
Either justify in detail the use of 24" for the dome thickness in the I.
5.
pres,ent analysis, or preserit a parametric study for different thick-nesses; for instance 24"; 18"; 15".
Demonstrate that the detensioned dome and the steel liner can take the load applied during 'tfih repair operations.
6.
Present a detailed discussion of the provir. ion made to monitor the behavior of the dome, the ring girder, and the top part of the cylin-drical wall during repair operations.
Indicate:
(a) the acceptance criteria for safety in such operations, and (b) the provisions made to safely stop the repair procedures if the acceptance criteria for safety are not met.
7.
Dascribe in detail the methods, acceptance criteria and methods of L.:pection for the grouting of the cap on the dome, the radial anchors to be installed and the grouting of these anchors. Present p
the planned testing.of these anchors.
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