ML19326B272
| ML19326B272 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 08/10/1976 |
| From: | FLORIDA POWER CORP. |
| To: | |
| Shared Package | |
| ML19326B271 | List: |
| References | |
| NUDOCS 8003160099 | |
| Download: ML19326B272 (25) | |
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g SUPPLEMENT 1 NRC COMMENTS TO THE CRYSTAL RIVER #.3 REACTOR BUILDING DOFE DELAMINATION REPORT DATED JUNE 11, 1976
- DOCKET NO. 50-302 GENERAL
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- 1. For easy reference, provide a list of tables and figures in the Table of Contents.
Answer: The caterial suggested has been incorporated into the Table of Contents.
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'S-1 Supplement 1 10-76
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SECTION 1.2
- 1. The staff considers the establishment of the causes of the dome d'elamination to be important in assessing the adequacy of the repair program and in providing assurance that another crack will not occur again during the life of the structure. The potential contributing factors should, therefore, be identified indicating the magnitude of radial tensile stresses created in
. the concrete.
Answer: The material has been incorporated into the report in Section 1.2.
- 2. The use of radial anchors will enhance the capability of the dome to resist t radial tension. However, they will not eliminate tension in concrete, and therefore small cracks may still exist. Provide an analysis to indicate that such cracks will not jeopardize the required structural integrity of the dome to resist all combinations of loadings for which it is designed.
Answer: These cracks exist primarily in regions where membrane behavior , dominates, i.e., negligible shear stress across the cracks. Despite the presence of the cracks, the membrane compression capacity of the concrete is adequate. Under LOCA or SIT, there is radial compression across the cracks. It is of interest to note that under 15% detensioning (admittedly a nominal stress change) deflections were less than predicted. If the cracks were contributing any significant effect to the response, larger rather than smaller deflections would be expected.
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In addition to the above considerations, secondary cracks will be epoxy grouted and the radial reinforcing will cross virtually all these cracks.
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S-2 Supplement 1 8-10-76 _ _ _ _ _ . _
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SECTION 2.3 AND TABLE 2-2
- 1. Clarify the definition of tensile capacity of concrete. Explain how
- principal tension is related to shear and diagonal tension as indicated is Section 2.3.1, and what is the difference between the shear discussed in this section and that in the next section (2.3.2). Answer: The material in sections 2.3.1 and 2.3.2 have been rearranged in the report, section 2.3.1 title is " Flexural and Membrane Tensile Stresses" and section 2.3.2 is entitled " Shear".
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- 2. Provide and describe with examples of actual des'ign, the conditions under I which each of the criteria (a) and (b) in Section 2.3.1 is applied.
Answer: The material requested now appears in section 2.3.2. Attachment #1 is
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a design example.
- 3. Since the stress / strain distribution is tri-axial, the limits of 3 /f -and e 6 vf[ may not be directly applicable to this problem and their use should be justified.
Answer: The state of stress in the dome may be regarded as being biaxial since the stress in the radial direction is very small in comparison with the membrane stresses. The interactions for tension-tension and tension-compression are not significant at least until the compression exceeds about 60% of the compressive strength of the concrete (Kupfer, Hilsdorf and Rusch, ACI Journal Aug. 1969) (Ref. 8 of the Report). Thus the limits of 3 /{[ and 6 /[[ are justified.
- 4. If 0.85fd as extreme compression in ultimate strength design is used, it may not be directly applicable for the same reason as in the above comment and should be justified.
Answer: Although criteria indicate that under factored load concrete stresses
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would be allowed to reach 0.85ff they do not. The actual stresses are much lower and do not appear critical since the dominant stress is bi-axial compression the strength should be higher.
- 5. The shear strength of concrete is influenced by stresses orthogonal to the axis of the element; therefore, this effect should be considered.
Answer: Hoop tension stresses should have little or no effect on radial shear strength, since sufficient bonded hoop rebar has been providad to preclude hoop tensile " Failure".
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S-3 Supplement 1 8-10-76
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ACIDfENT 1 FOR Ah5WER TO QUESTIG . 3(2)
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Supplement 1 8-10-76
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Supplement 1 8-10-76 t a
_ SECTION 2.4
- 1. In the paragraph in the middle of ,Page 2-4, you indicated that for structural integrity test and accident condition b.ad 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
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combination on a stress-strain diagram.
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Answer: See Attachment 2. ~.
- 2. On Page 2-5 under Item b Creep, it is indicated that as a result of concrete creep there is a reduction in concrete stress and an increase in liner stress.
Since the liner is relatively thin and may buckle under prestress, the liner-should not be considered to contribute 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 .e leaktightness integrity. Revise the concrete stresses in the report if they have been reduced. Answer: A reduced modulus of elasticity of concrete nas oeen used in the analysis and thus the effect of creep on concrete and liner stresses has been accounted for. Our analysis indicates that for the load combinations D+F and D+F o+ T the concrete stress is increased if the liner is removed in the analytical model. From the standpoint of concrete stress behavior for the SIT and LOCA load combinations, to remove the liner from the analy,tical model is not conservative. The figures in the report have been modified to provide a comparison of both results at selected points.
- 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.
Answer: Table 2.2 has been modified to reflect liner design criteria.
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S-4 Supplement 1
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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 ring girder and in the dome the EE is 01fferent in all these directions and this effect should be considered in the analysis. The wall acts es in orthotropic element.
- The different parts of the structure have simultaneously different Ej due to different specific creep.
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Answer: The effect of cr.aep has been accounted for by the use of reduced modulus. Although the different parts of the structure have different prestress, the specific creep (creep due to unit psi) should be the
,. same for the same material. Thus the reduced modulus should be about the same for the various parts of the structure. A calculation is attached to demonstrate this (See Attachment 3).
- 5. In Table ~-3 4 add load combination equation for repairs. This equation should include the seismic load term.
Answer: The FSAR and the current ASME Code leci combinations do not include
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earthquake effects in combination with censtruction loads.
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- S-5 Supplement 1 8-10-76 l
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Shtst 1 of 2 ATTAC19fENT 2 FOR ANSWER TO QUESTION 2.4(1) E'tAMPLE of s i7- <csitcou;riou ; 24" DOME StT lbni 4-/7
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Supplement 1
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8-10-76 4
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Sheet 2 of 2
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Supplement 1 8-10-76
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Sheet 1 of 3 ATTACHMENT 3 FOR ANSWER TO QUESTION 2.4(4) - CREEP
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Creep of the concrete under sustained loads D, Fv, F ,Hand Fp has several effects on tendon forces and containment stresses. The most obvious is to d-crease the tendon forces with time. This effect is taken into account in tae prestress loss calculacions. Another effect is to decrease. concrete stresses and to increase liner stresses and strains, which are compressive over cost of the containment structure. The decrease in concrete stress is due to the additive effects of the decrease in tendon force plus the creep straining of the concrete acting with a non-creeping liner, which tends to shed compressive stresses from the concrete to the liner. t This latter effect is taken into account in the analysis through the use of the effectiveYoung'sModulus,Ej,appearingonpage4-3ofthereport. Using this approach, less concrete compression is calculated to be available to resist SIT or LOCA conditions than would be calculated by considering the reduced tendon force alrme. With respect to liner stresses and strains, the structural analyses show that the EE effect 6
"E = 2.7 x 106 @ present and Eh = 1.8 x 106 @ 40 yr versus (E
Ec = 4 x 10 instantaneous) is much greater than that of the reduced tendon force. The net result is liner stresses and strains which have compressive values much greater than those which occur at initial prestress. The liner strains in the report include this.
- A third effect of concrete creep is to produce creep induced stresses which result only when the E{ is not uniform over the containment structure. If EE is uniform, the stresses at any time are equal to those at initial prestress less tendon losses, in the case where the liner is not part of the model. l The E[ values used in the structural analyses correspond to specific creep values, se, which were calculated based on the 1) average age of the dome concrete at application of the dome prestress (average) and 2) the duration of this prestress to "present" and to "40 yrs". The resulting EE values were applied to the entire structure in the analyses for D + F. It I
- was recognized that a different E{ is associated with vertical (Fy), hoop (FH), and dome (FD ) prestress loading conditions. This is so only because j the concrete age at application of each prestress load is different and the l duration of each type is different. However, EE values were based on the dome concrete age and dome prestress since it is that part of the containment structure which is most effected by the delamination. Also, it was felt that these EE values would be an average for the wall since, chronologically, F D was applied between Fy and F H. Nevertheless, a more accurate determination of the ersao effects due to the separate application and duration of the prestress is disc.ased.below.
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As pointed out previously the determination of El depends on 1) age of concrete at loading and 2) duration of load. El is independent of the level of stress in the concrete, which is reflected in sc (u in/in pcr 1 psi of stress), j
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Supplement 1 8-10-76 l __ __ _ , _ _ _
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Sheet 2 of 3 ATTACE1E :T 3 FOR ANSWER TO QUESTION 2.4(4) - CREEP (Cont'd) Therefore, creep induced stress under eithery F , F , rF will be reflected H 3 only in differences in E' for the various elements in the containment for each of these prestress loads. The total results would be obtained from the sum of the analyses shown below. Fy \ u ' y
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y Adv Adv Adv w w N_ L N' A Argv
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Awv =
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FH Awv = age of wall at time Fy is applied. Argy = age of ring girder at time Fy is applied. Adv = age of dome at time Fy is applied. Similar for AwH, ArgH, AdH and AwD, ArgD, add.
, Dv = duration of Fy from time of application to "present" or "40 yr" times, similar for D an D H D Knowing the values of A and D permit calculation of E' for the three elements.
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l l Supplement 1
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Shtet 3 of 3 ATTACIDIENT 3 FOR ANSWER TO QUESTION 2.4(4) - CREEP (Cont'd) -l Values for E' were obtained based on average pour dates for the wall, ring girder, and Eome and average stressing dates for the three tendon systems. This is presented below. Wall Ring Girder Dome Average Pour Dates: 6-19-72 9-1-73 5-15-74
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Vertical Hoop Dome Average Stressing Dates: 11-15-74 2-15-75 12-1-74
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"40 yr" Time E' (psi) x 100 E' (psi) x 10
' P/S Aw Arg Ad a Ring D Ring System (da) (da) (da) (do? '.
._ Gir. Dome (yrs) Wall Cir. Dome Vertical 880 425 180 545 3.13 2.89 2.63 41.5 2.08 1.96 1.75 Hoop 970 515 270 455 3.17 3.03 2.36 41.2 2.13 2.04 1.89 Dome 880 455 210 515 3.13 3.03 2.70* 41.4 2.08 2.04 1.80*
- used in structural analysis of containment.
The differences between E' values for the wall, ring girder, and dome under a specific prestress conditEen is not enough to produce stresses significantly different from those reported.
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i i Supplement 1
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SECTION 3.1
- 1. Discuss, the , reliability 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.
Answer: The direct tensile test was designed to identify the tensile capacity of the concrete in the structure in relation to its compressive strength. It was not intended to define the property of the concrete in a state of triaxial stresses, since the actual state of stress at points of stress concentration in the delaminated dome cannot be accurately defined. . ~ The effect of the tensile stress in combination with two orthogonal compressions is discussed in Section 3.3.3 of the report. No further
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S-6 Supplement 1 8-10-76
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SECTION 3.3
- 1. In the list of factors which may have contributed to the /.laaination problem, add: creep and stress concentrations (at tendons) inherent in this type of structure.
Answer: Creep in the membrane direction would not increase the radial stress.
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The effect of stress concentrations is discussed in sectica 3.3.2.
- 2. In Section 3.3.2 it is indicated that by using SAP IV computer program r.nd 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 el'ements, such as reinforcing steel, and tendon conduits, Answer: There is no element representing reinforcing steel or tendon conduit. The effect of reinforcing steel is calculated as transformed concrete area and represented by effective Young's Modulus. Modeling of the tendon conduit is described in Section 3.3.2. (2) the manner in which the prestressing force is applied, indicating if the prestreesing force component tangent to the dome curvature is considered. Answer: Prestressing force is applied on three middle layers of the model in both the radial and the tangential directionc of the dome.
- 3. Provide the hand calculation which you made to obtain the radial tension.
Answer: These calculations are included in attachment.
- 4. In Section 3.3.4, transient thermal gradients may generate shear stresses, and should be considered in the analysis. Similar effect exists for - -
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localized thermal gradients. Answer: Since thermal restraint produces normal strain, but no shear strain, the thermal gradient causes shear stress; but only in the areas which are reinforced for shear (Chapter 14 of Reference 11).
- 5. The solution for stress concentrations as snown in Fig. 3-17 & 3-18 is incomplete. It should be noted that compression exists also in the direction parallel to the conduit (c1). This stress generates additional
. stress concentration in the plane (c21 C3 ) orthogonal to the tendon, which should be added to the stresses shown in Fig. 3-18.
l.swer: Assuming this question addresses the ef fect of Poisson's ratio, this effect was considered and is discussed in Section 3.3.2.
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S-7 Supplement 1 j S-10-76 4 i i
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- 6. When the effect of tendon conduits is analyzed, it should be noted that this effect is different when evaluated in the direction parallel to the tendon and orthogonal to the tendon. In the direction parallel to the tendon a 1/4" thick pipe (5"0) approximately replaced the removed concrete.
But in the direction perpendicular to the tendon, the pipe introduces a flexible _ link which modifies the average properties of the concrete section. Answer: Ve have reviewed the effect of the conduit on stresses following a path 9 90 from the stress profile shown in Figure 3-18. The distribution shown in attachment indicates that the effect will not be significant. However, the effect on conduits are conservatively represented by a concrete layer with equivalent Young's modulus calculated by the ratio of net concrete volume to gross concrete volume.
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S-8 Supplement 1 8-10-76
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__ _ ATTACHMEK4' FOR ANSWER TO QUESTION 3.3(3) The radial tension are hand-calculated as follows:
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Top Tendon R y = 1343.9" Middle Tendon R 2
= 1338.4" Bottom Tendon R 3
= 1332.8" Tendon force at 0.7 ultimate = 1633 tendon spacing 30" 1633 x 1000 12.1 12.1 Top Tendon c y =
= 40.5 x = 13.6 psi 30 x 1343.9
- 36 36 Middle Tendon c x x j = 19.9 Psi 2"3 x 33 d" -
2 Bottom Tendon c x j = 40.8 x j = 26.3 psi 3" 0 332 8 The radial tension due to all three layers of tendon are superimposed as follows
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I 1 Supplement 1 8-10-76
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1 l ATTACIDIENT FOR ANSWER TO QUESTION 3.3(6)
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STRESS PROFILE SOo Awsy Faos Fie,3_t s l Supplement 1 8-10-76
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_ SECTION 4.4
- 1. In Sections 4.4.1 and 4.4.2 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 adequate.
Answer: The tendon conduit is not required and has not been considered as contributing to the shear capacity.
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SECTION'5.3 1
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'l.. In~ releasing the prestressing force as a result of tendon datensioning,
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- strain recovery will occur. However, most likely the strain recovery 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 the region
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.of the liner anchors.
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Answer: 'Not applicable under new repair sequence.
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12 . The behavior o the detensioned dome is strongly influenced by the creep of j .the prestressed structure which has taken place after prestressing and up
, to this date. The detensioning of the dome will not return the structure-r to a previously unprestressed state, whatever the sequence of operations.
It is therefore imperative to analyre the detensioned dome for the influence t 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.
Answer: Not applicable under new repair sequence. _ ] .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 demonstrate that these shear stresses, acting simultaneously with normal' stresses, do not endanger the stability of the dome. Special attention should be given to radial shears. 4 ' Answers: Not applicable under new repair sequence. J
- 4. Either justify in detail the use of 24" for the dome thickness in the present analysis, or present'a parametric study for different thicknesses;
- for instance 24";'18"; 1.5".
-Answer: The response of.the structure to detensioning, and the parametric studies
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of section 3.0 indicate that the structure is responding as a 24" structure. The addition of epoxy grout, radial anchors and new reinforcing on the. cap will assure its continued performance. Also see response to question 1.2.2
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.'5.- Demonstrate that the detensioned dome and the steel liner can take the load applied.during the repair operations.
Answer: ~Not applicable under new repair sequence. '
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- 6. Present a detailed discussion of the provision made to monitor the behavior of the dome, the ring girder, and the top part of the cylindrical wall during repair operations. Indicate:
- a. The acceptance criteria for safety in such operations, and Answer: This information has been added to the report as Section 5.0 Corrective
. Action,
- b. the provisions made to safely stop the repair procedures if the acceptance criteria for safety are non met.
-~ Answer: All activities on the dome will be temporarily suspended and no personnel, except inspectors, will be allowed on the dome after a stop work signal-
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until approval to proceed is obtained from the Engineer and the Owner.
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The acceptance criteria shall be in accordance with the requirements noted for each measurement in Table 1. Work shall stop immediately when readings are outside the limits noted in Table 1 for displacements and liner strains and the Engineer shall be notified. An unsatisfactory set of readings requiring immediate notification of the Engineer during detensioning shall be when one concrete strain or reinforcing bar gage reading exceeds the values specified in Table 1. 4 The top surface of the dome shall be visually inspected for cracks i before commencement of detensioning and any. findings recorded. During detensioning and retensioning operations, the inspection for cracking shall be made on a daily basis as a minimum. Observations shall be reported to the Engineer.
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- 7. Describe in detail the methods, acceptance criteria and methods of I inspection for the grouting of the cap on the dome, the radial anchors to be installed and the grouting of these anchors. Present the planned testing of these anchors.
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Answer: Grouting of cap of dome is no longer part of the repair sequence. The procedure for sizing radial anchors is described in Section 5 of the report.
'A test program is being conducted to choose the best set of anchoring devices among the following; a cone and expansion shell anchor system grouted with cement grout, a thread rod with nut bearing grouted with cement grout, a threaded anchor with nut bearing grouted with epoxy
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grout, and a deformed rod grouted with epoxy grout. m
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S-11 8-10-76
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Three (3) types of anchors manufactured by Williams Form Engineering Company have been selected for testing..
- 1. Williams long cone and long expansion shell (LCS-200).
- 2. Williams standard cone and standard expansion shell (SCS-200).
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- 3. Williams deformed anchor with and without an end nut. In addition a non-deformed anchor with nut bearing assembly will be tested.
Three'(3) different grouts are being tested:
- 1. Master" low 814 cement grout.
- 2. Masterflow 713 cement grout.
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- 3. Sikadur Hi-Mod 370 epoxy.
Following series of tests are conducted to verify the anchor strength.
- 1. A shallow hole, 2" in diameter and 7 inches deep.
- a. To verify that torquing of bolt will not cause damage or rupture to the nearby concrete.
- b. To establish the failure mode of concrete for available minimum depth. ;
- c. To establish the design load capacity of the anchor at the minimum available embedmen; depth.
- 2. A'2" diameter hole 10 inches deep.
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- a. To verify that torquing of bolt will not cause damage or rupture to the nearby concrete.
- b. To establish the failure mode of concrete for this embedment.
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- c. To establish the load capacity of anchor for this embedment.
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- 3. A 31 inch ' deep hole.
- a. To' develop and maintain the design preload in the bolt.
- b. Upper and lower bound torque values requirements to develop
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S-12 Supplement 1 8-10-76
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- c. To verify strength of the anchor with respect to concrete capacity. ,
- 4. A 31 inch deep hole (epoxy grouted test block).
- a. To investigate anchors capacity in epoxy grouted concrete.
. b. To establish the failure mode of concrete.
- c. To compare the anchor capacity with solid concret'e block.
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The most suitable anchor type will be established af ter testing is complete. Final anchor configuration and design basis for the anchor will be submitted
# .as an addenda to the report.
- 8. Provide a commitment that sufficient strain instrumentation will be
~ installed at the top and bot tom of the dome to assure that during retensioning of tendons the upper portion of the dome (above the crack) will be participating in developing compressive stress at the same rate as the lower portion. ,
Answer: The instrumentation is described in Section 5.0. The gages which exist in the cap will be replaced with strain gages on embedded reinforcing bars and the radial anchors. Observation of this instrumentation during the retensioning and SlT should assure that' the structure is responding as designed.
- 9. Indicate in more. detail the planned method of waterproofing of the repaired dome and its pre :ection against detrimental environmental conditions.
Answer: A detailed description will be provided later.
- 10. Describe the acceptance ' testing of the repaired dome and the inservice monitoring of the structure. i
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- Answer: Acceptance of the repaired dome will be based on satisfactory completion )
of the SIT. Af ter the SIT the currently accepted inservice inspection requirements will be performed. ;
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- 11. Investigate the influence of possible cracking in the h*oop direction on the dome tendon conduits.
Answer: Not appl'icable under new repair sequence.
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TABLE 1 FOR ANSWER TO QUESTION 5.3(6b) PREDICTED STRAINS AND DISPLACEMENTS 15% PRESTRESS Gage Type of Predicted No. Measurement Measurement Range
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E22 Liner Rad. Displace. 0.017 in 20.004 in E23 Liner Rad. Displace. 0.017 in !O.004 in E24 Liner Rad. Displace. 0.017 in 20.004 in E25 Liner Rad. Displace. 0.008 in 10.002 in E26 _ Liner Rad. Displace. 0.008 in 20.002 in E27 Liner Rad. Displace. 0.008 in !O.002 in E28AV Liner Vert. Displace. 0.041 in !0.01 in E28BV Liner Vert. Displace. 0.016 in !0.004 in E29AV Liner Vert. Displace. 0.041 in 10.01 in
-E29BV Liner Vert. Displace. 0.016 in 20.004 in E30AV . Liner Vert. Displace. 0.041 in 20.01 in E30BV Liner Vert. Displace. 0.016 in !0.004 in Apex Vert. Displace. 0.129 in 20.032 in 15' Radius Vert. Displace. 0.129 in 10.032 in 30' Radius Vert. Displace. 0.120 in 10.03 in 45' Radius Vert. Displace. 0.069 in :0.017 in Rll8M Liner Merid. Strain 65 p in/in : 33 p in/in Rll8D Liner Diag. Strain - -
Ril8H Liner Hoop Strain 33 u in/in ! 16 u in/in R119M Liner Merid. Strain 65 u in/in : 32 u in/in R119D Liner Diag. Strain - - R119H Liner Hoop Strain 67 u in/in ! 33 u in/in R120M Liner Merid. Strain 65 p'in/in 33 u in/in
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R120D Liner Diag. Strain - R120H Liner Hoop Strain 33 p in/in 16 u in/in R121M Liner Merid. Strain . 65 p in/in : 32 u in/in
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R121D Liner Diag. Strain - R121H Liner Hoop Strain 67 u in/in : 33 p in/in
. R122M Liner Merid. Strain 73 u in/in 37 u in/in ,
R122D Liner Diag. Strain - l R122H Liner Hoop Strain 74 u in/in : 37 u in/in R123M Liner Merid. Strain 65 u in/in : 33 u in/in
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R123D Liner Diag. Strain - R123H Liner Hoop Strain 33 u in/in : 16 u in/in 1
.R124M Liner Merid. Strain 73 u in/in ! 37 p in/in l R124D Liner Diag. Strain - - l R124H Liner Hoop Strain 74 u in/in t 37 p in/in l
R125M Liner Merid. Strain 65 u in/in : 33 u in/in
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R125D Liner Diag. Strain - R125H Liner Hoop Strain 33 u in/in : 16 u in/in n
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Supp'lement 1 8-10-76}}