ML20032D795
| ML20032D795 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 08/31/1981 |
| From: | BECHTEL GROUP, INC. |
| To: | |
| Shared Package | |
| ML20032D791 | List: |
| References | |
| IEB-79-02, IEB-79-2, NUDOCS 8111170492 | |
| Download: ML20032D795 (14) | |
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9 FLORIDA POWER & 1.IGHT COMPAM TURKEY POINT UNITS 3 & 4 FINAL REPORT ON PIPE SUPPORT BASE PLATE DESIGNS USING CONCRETE EXPANSION ANCHOR BOLTS (In Response to NRC IE Bulletin 79-02, March 8, 1979, NRC IE Bulletin 79-02 (Revision 1), June 21,1979, and-NRC IE Bulletin 79-02 (Revision 2), November 8,1979)
Bechtel Power Corporation Gaithersburg, Maryland August 1981 8111170492 811016 PDR ADOCK 05000250 P
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TABLE OF CONTENTS SECTION Page I.
INTRODUCTION 1
II.
RESPONSE TO ACTION ITEMS 2
III.
SUMMARY
OF REMAINING INSPECTIONS 10 ATTACHMENT Exhibit I Turkey Point Units 3 5 4 - Syste=s Covered
- 5 FLORIDA POWER & LIGHT COMPANY TURKEY POINT UNITS 3 & 4 FINAL REPORT ON
-PIPE SUPPORT BASE PLATE DESIGNS
'1 SING CONCRETE EXPANSION ANCHOR BOLTS (In Response to NRC IE Bulletiu 79-02, March 8,
- 1979, NRC IE Bulletin 79-02 (Revision 1), June 21, 1979 and NRC IE Bulletin 79-02 (Revision 2), November 8,1979)
I.
INTRODUCTION This report is a final response to NRC I.E.Bulletin 79-02 (including Revisions 1 & 2) for Turkey Point Units 3 and 4.
The information pertaining to Unit 4 supplements tne final-report previously submitted to the NRC on July 9, 1979, under transmittal by Florida Power and Light letter L-79-186.
I.E.Bulletin 79-02 required all licensees and permit holders for nuclear power plants to review the design and installation procedures for concrete expansion anchors used in pipe support-base plates in systems defined as Seismic Category I by NRC Regulatory Guide 1.29, " Seismic Design Classification", Revis-ion 1, August 1973, or by the applicable SAR. Exhibit I pro-vides the list of systems covered by this response to this Bulletin.
Since the submittal of the final report for Unit 4, additional supports with expansion anchors have been identified as requiring further evaluation in response to NRC Audit Reports 50/250/80-18 and 50/251/80-18. Furthermore, inspections have been performed in response to this Bulletin on Turkey Point Unit 3 including the supports identified by the NRC Audit Reports noted above.
Inspection and evaluation of these remaining cupports will be conducted in conjunction with the in-progress work.under I.E.
A summary of these supports is provided in Sec-tion III of this report.
Section II of this report provides responses to action items as presented in Revision 2 of I.E. Bulle tin 79-02.
These responses -
were previously provided in the initial report submitted unde r this Bulletin.
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RESPONSE TO BULLETIN ACTION ITEMS l
Bulletin Action Item No. 1.
Verify that pipe support base plate flexibility v-tecounted for in the calculation of anchor bolt loads.
sa lieu of supporting analysis justifying the assumption of rigidi ty, the base plates should be con-sidered flexible if the unstiffened distence between the
-me=ber welded b *he plate and the edge of the base plate is greater than txe the thickness of the plate.
It is recognized that this criterion is conservative. Less conservative acceptance criteria must be justified and the justification submitted as part of the response to the Bulletin.
If the_ base plate is determined to be flexible, then recalculate the bolt loads using an appropriate analysis.
If possible, this is to be done prior to testing of anchor bolts. These calculated bolt loads are referred to hereaf ter as the bolt design loads.
t A description of the analytical model used to verify that pipe support base plate flexibility is accounted for in the calculation i
of anchor bolt loads is to be submitted with your response to the Eolle tin.
It has been noted that the schedule for analytical work on base plate flexibility for some facilities extends beyond the Bulletin reporting time fra=e of July 6, -1979.
For those facilities for which an anchor bolt testing prqg ram is required (i.e., sufficient QC documentation does not exist), the anchor bolt testing program should not be delayed.
Response to Bulletin Action Item No.1. All Seismic Category I pipe anchor and support base plates using expansion anchor / bolts were reanalyzed to account for plate flexibility, bolt stiffness,. shear-tension interaction, minimum edge distance, and proper bolt spacing.. Depend-ing on the complexity of the individual base plate configuration, one of the following methods of analysis was used to determine the bolt forces:
a.
A quasi-analytical method, developed by Bechtel, was used for base plates with eight bolts or less. An analytical formula-tion has been developed for the base plates which treats the plates as a beam on multiple spring supports subjected to moments and forces in three orthog onal directions. Based on aanlytical considerations as well as the results of a number of representative finite element analyses of base plates (using the "ANSYS" Code), certain empirical f actors were intro-duced in the simplified beam model to account for (a) the effect of concrete foundation and (b) the two-way action of load transfer in a plate.
These factors provided a way to account for effects of variable parameters such as plate di '
mensions, attachment sizes, bolt spacings, and stif fnesses on the distribution of external loads to the bolts.
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The results of a number of case studies indicated excellent correlation between the results of the present formulation and those by the finite element me thoo (using the ANSYS Code).
The quasi-analytical method generally predicts bolt loads l
laq;er than the finite e.'.ement method.
Althoqgh the effect of pla te flexibility has been considered explicitly in the quasi-an tytical formulation described above, the impact of prying action on the anchor bolts was determined not to be critical for the following reasons:
1)
Where the anchorage system capacity is g overned by the concrete shear cone, the prying action would result in an application of an external compressive, load in the cone and would not therefore affect the anchorag e capacity.
2)
Where the bolt pull out determines the anchorage capacity, the additional load carried by the bolt due to the prying action will be self-limiting since the l
bolt stif# ness decreases with increasing load. At higher loa.:s the bolt extension will be such that the corners of the base plate will lifr off and the prying action will be relieved. This phenomenon has been found to occur when the bolt stiffness in the Finite Element Analysis was varied from a high to a low value, to correspond typically to the initial stiffness and that beyond the allowable design load.
A computer prqg ram for the analytical technique described above has been implemented - for determining the bolt loads for routine applications. The program requires plate dimen-sions, number of bolts, bolt size, bolt spaciqg, bolt stiff-nes's, the applied forces, and the allowable bolt shear and tension loads as inputs. The allowable loads for a given bolt are determined based on the concrete edge distance, bolt spacing, embedment leng th, shear cone overlapping, manu-facturer's ulti= ate capacity, and a design safety factor. The i
program computes the bolt forces and calculates a shear-tensii n l
interaction value based on the allowable loads.
i The shear-tension interaction in the anchor bolts has been accounted for by the conservatively assuming that the total applied shear is carried by the bolts in accordance with the following interaction formula (7-)2 - ( 7-) 2 T
S
=1.0 A
A Where T and S are the calculated tensile and shear forces and I and S are the respective allowable values.
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For special cases where the design of the support did not L.
- _ad itself to the foregoin; method, one of 'che following standard engineering analytical techniques with conserva-tive assumpcions was employed in the analysia
1)
Conventional rigid plate analysis was performed to determine actual bolt tension load. An amplifica-tian factor of 1.5 was applied to accourt for base plate flexibility with the exception of two bolt and four bolt symmetrical at:schments under pure tension. This amplification factor is considered conse rvative based on the AISC Manual of Steel Con-struction, Part 4 (Connections in Tension) and the results of case studies performed by the finite ele =ent method to verify the quasi-analytical method.
2)
Conventional rigid plate analysis was performed with the exception that a conservative moment arm equal to the distance between the centerline of bolt and the outer-=ost face of the welded attachment was used.
Bulletin Action Item No. 2.
Verify that the concrete expansion anchor bolts have the following cini=um factor of safety be tween the bolt design load and the bolt J timate capacity determined from static load tests (e.g. anchor bolt manufacturer's) which simulate the actual conditions of installation (i.e., type of concrete and its streng th properties):
a.
Four - For wedge and sleave type anchor bolts, b.
Five - For shell type anchor bolts.
The bolt ulti= ate capacity should account for the effects of shear-tension interaction, minimum edge distance and proper bolt spacing.
If the mini =um factor of saf ety of four for wedge type anchor bolts and five for shell type anchors cannot be shown, then justi fication must be provided.
The Fulletin factors of safety were intended for the maximum support lcsu including the SSE.
The NRC has not yet been provided adequate justification that lower factors of safety are acceptable on a long tern basis. Lower factors of safety are allowed on an interia basis by the provisions of Supplement No. 1 to IE Bulletin No. 79-02.
The use of reduced factors of safety in the factored load approach of ACI 349-76 has noc yet been accepted by the NRC.
Response to Bulletin Action Item 2. A reanalysis of all expansion bolts for pipe anchors and pipe supports for the systems presented in Exhibit I was performed for Units 3 and 4 using the analytical methods described in the response to Bulletin Action Ites No. 1.
Less than one percent was found not to be in confor=ance with the minimum factors of safety of 4 for wedge type or 5 for self-drilling type, as appropriate, and repaired per response to Bulle tic Action Ites No. 4.
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xs Bulletin Action Item No. 3.
Describe the design requirements if -
applicable for anchor bolta to withstand cyclic loads-(e.g., seismic loads and high cycle operating loads).
Response To Bulletin Action Item.1. The original design of the piping t
systems considered deadwe 4g ht, thermal stresses, seismic loads, and dynamic loads (including steam hammar in the main steam system) in the generation of the static equivalent pipe support. design loads.
To the extent that these loads include cyclic considerations, these effects are included in the design of the hangers, base plates, and anchorages.
The safety f actors used for concrete expansion anchors installed on supports for safety-related piping systems were not increased for loads which are cyclic in nature.
The use of the sa=e safety factor for cyclic and static leads is based on the FFTF Tests *. The test results indicate:
a.
The expansion anchors successfully withstood two million cycles of long-term fatigue loading at a maximum intensity of 0.20 of the static ultimate -capacity.
k' hen the maximum load intensity was increased steadily beyond the aforemen-tioned value and cycled for 2,000 times at each load step, i
the observed failure load was about the same as the static ultimate capacity.
b.
The dynamic load capacity of the expansion anchors, under simulated seismic loading, was about the same as their corresponding static ultimate capacities.
Bulle t; Action Ites No. 4.
Verify from existing QC documentation that design requirements have been met for each anchor bolt in the following areas:
Cyclic loads ha; e been considered (e.g., anchor bolt pre-a.
load is equal to or g reater than bolt design load).
In the case of the shell type, assure that it is not in contact with the back of the support plate prior to preload testing.
b.
Specified design size and type is correctly installed (e.g.,.
proper embed =ent depth).
If sufficient docu=catation does not exist, then initiate a testing prog ram that will assure that minimum design requirements have been
=e t with respect to sub-items a. and b. above. A sampling technique is acceptable.
One acceptable technique is to randomly select and test one anchor bolt in each base plate (i.e., some supports may hat e more than one base plate). The test should provide verification.of sub-items a. and b. above.
- Drilled-In Expansion Bolts 'Inder Static and Alternating Loads, Report BR-5853-C-4, Revision 1, B '..itel Power Corp., October 1976.
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If the test fails, all other bolts on the bass plate should be similarly tested.
In any eve nt, the test program should assure that each Seismic Category I system will perform its intended function.
The preferred test method to demonstrate that bolt preload has been accomplished is using a direct pull (tensile test) equal to or greater than design load.
Recognizing this method may be difficult due to accessibility in some areas an alternative te s t method such as torque testing may be used. If torque testing is used, it must be shown and substantiated that a correlation be-tween torque and tension exists.
If manufacturer's data for the specific bolt used is not available, or is not used, then site specific data must be developed by qualification tests.
Bolt te st values of one-fourth (wedge type) or one-fifth (shell type) of bolt ultimate capacity may be used in lieu of indivi-dually calculated bolt design loads where the test value can be shown to be conservative.
The purpose of the Bulletin is to assure the operability of each seismic Category I piping system.
In all cases an evaluation to confirm system operability =ust be performed.
If a base plate or anchor bolt f ailure rate is identified at one unit of a mult-unit site wnich threatens operability of safety related piping systems of that unit, continued operation of the remaining units at that site must be i= mediately evaluated and reported to the NRC. The evaluation must consider the gereric applicability of the identified failures.
Appendix A describes two sampling methods for testing that can be used. Other sa=pling =ethods may be used but must be justified.
Those options may be selected on a system by system basis.
Justification for omitting certain bcits from sample testing which are in high radiation areas during an outage must be based on other testing or analysis which substantiates operability of the affected system.
Bolts which are found during the testing program not to be preloaded to a load equal to or greater than belt design load, must be properly preloaded or it must be shown that the lack of preloading is not detrimetal to cyclic loading capability. Those licensees that have not verified anchor bolt preload are not required to go back and establish preload. However, additional information should be sub-mitted which demonstrates th2 effects of preload on the anchor bolt l
ultimate capacity under dynamic loading.
If it can be established that a tension load on any of the bolts does not exist for all load-ing cases, then no preload or testing of the bolts is required.
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If anchor bolt testing is done prior to comple tion of the analy-tical work on base plate flexibility, the bolt testing must be performed to at least the original calculated bolt load.
For testing purposes, f actors may be used to conservatively estimate the potential increase in the calculated bolt load due to base plate flexibility. Af ter completion of the analytical work on the base plates, the conservatism of these f actors must be verified.
For base plate supports using expansion anchors, but raised from the supporting surf ace with grout placed under the base plate, for testing purposes, it must be verified that leveling nuts were not used.
If leveling nuts were used, then they must be backed off such that they are not in contact with the base plate before apply-ing tension or torque testing.
The Bulletin requires verification by inspection that bolts are properly installed and are of the specified size and type.
Para-meters which should be included are embedment depth, thread engagement, plate bolt hole size, bolt spacing, edge distance to the side of a concrete member and full expansion of the shell for shell type anchor bolts.
If piping systems 2 1/2-inch in dia=e ter or less were computer analyzed, then they must be treated the same as the larger piping.
If a chart analysis me thod was used and this method can be shown to be highly conservative, then the proper installation of the base plate and anchor bolts should be verified by a sampling inspection. The parameters inspected should include those described in the preceding paragraph.
If small diameter piping is not in-spected, then justification of system operability must be provided.
Response to Bulle tin Action Item No. 4.
Design requirements of anchor bolts for cyclic loads have been discussed in the response to Bulletin Action Item No. 3.
A jobsite inspection and testing program provided for verification of expansion bolts for both large bore (greater than 2 inches) and small bore (2 inches or less) pipe anchors and supports for Seismic Category I portions of the Units 3 and 4 systems presented in Exhibit I.
For those supports where it could be established that a tension load on any of the bolts does not exist for all loading cases, then no preload or testing of the bolts was performed. All inspection, testing, evaluating and corrective actions were performed in accord-ance with written procedures. These procedures and records of inspection, testing, and repairs are available at the Turkey Point Jobsite for inspection.
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i The program provided that the following information be verified, recorded, evaluated and corrected, as required:
4 1)
Support plate conforms to design details, plate dimensions, plate thickness, and bolt configuration (number of bolts, spacing, edge distance, bolt hole size).
t 2)
Anchor bolt length, diameter, embedment depth, type.
3)
Anchor bolt projection.
4)
Nut / thread engage =ent.
5)
Pins and washers (on wedge type).
6)
Washers (on self-drilling type).
7)
Gap between plate and self-drill anchor sleeve.
8)
Leveling nuts backed off prior to torquing.
9)
Minimum torque achieved equivalent to preload of o'ne-fourth ultimate tension capacity for wedge anchors and one-fifth ultimate tension capacity for self-drilling anchors.
10)
Full expansion of shell (on self-drilling type).
Hangers / restraints were inspected for oversized b.olt holes when the magnitude of loads, hanger / restraint configuration, and load application produced combined axial tension and shear or shear only.
All other hangers / restraints including small bore pipe hangers have nominal loads which require minimal bolt to plate clamping capacity or surface contact area.
All supports with inaccessible or nonconforming bolts were re-analyzed using one of the analytical methods discussed in the -
response to Bulletin Action Item 1 and repaired in accordance with j
written procedures. When required, self-drilling type anchor bolts were replaced with wedge type anchor bolts.
Bulletin Action Ites No. 5. Determine the extent that expansion anchor bolts were used in concrete block (masonry) walls to attach piping supports in Seismic Category 1 systems (or safety related systems as defined by Revision 1 the Bulletin).
If expansion anchor bolts were used in concrete block walls:
a.
Provide a list of the systems involved, with the number of supports, type of anchor bolt, line size, and whether these supports are accessible during normal plant operation.
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Describe in detail any design consideration used to account for this type of installation.
c.
Provide a detailed evaluation of the capability of the supports, including the anchor bolts, and block wall ~to meet the design loads. The evaluation must describe how the allowable loads on anchor bolts in concrete block walls were determined and also what analytical method was used to determine the integrity of the block walls r.nder the imposed loads. Also describe the acceptance criter.ia, including the numerical values, used to perform this evaluation. Review the deficiencies identified in the Information Notice of the pipe supports and walls at Trojan to determine if a similar' situation exists at your facility with regard to supports
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using anchor bolts in concrete block walls.
d.
Describe the results of testing of anchor bolts in concrete block walls and your plans and schedule for any further action.
Response to Bulletin Action Item No. 5. A field walkdown of all Turkey Point Unit 3 & 4 concrete block walls has been completed to determine tue extent to which expansion bolts were used to attach piping supports for Seismic Category I systems.
Results of this walkdown verified that no expansion bolts were used to support any Category I system piping off block walls.
Bulletin Action Item No. 6.
Determine the extent that pipe supports with expansion anchor bolts used structural steel shapes instead of base plates. The systems and lines reviewed must be consistent with the criteria defined in Revision 1 of the Bulletin.
If expansion anchor bolts were used as described above, verify that the anchor bolt and structural steel shapes in these supports were included in the actions performed for the Bulletin.
If these supporte cannot be verified to have been included in the Bulletin actions:
a.
Provide a list of the systems involved, with the number of supports, type of anchor bolt, line size, and whether the supports are accessible during normal plant operation.
b.
Provide a detailed evaluation of the adequacy of the anchor bolt design and installation.
The evaluation should address the assumed distribution of loads on the anchor bolts.
The evaluation can be based on tha results of previous anchor bolt testing and/or analysis which substantiates operability of the affected system.
Describe your plans and schedule for any forther action c.
necessary to assure the affected systems meet Technical Specifications operability requirements in the event of an SSE.
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N Re sponse to Bulletin Action Item No. 6.
Structural steel shapes were used to a minor extent instead of base plates for pipe sup-ports with expansion anchor bolts. The anchor bolts and structural steel shapes in these s.:pports were included in the actions performed under Revision 1 of the Bulletin.
For analytical methods used, refer to Part b this report's response to Bulletin Action Item No.
1.
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s III.
SUMMARY
OF REMAINING !..SPECTIONS As noted in the Introduction to this report, some supports with expansion anchors have been identified as requiring further inspection or evaluation as a result of a previous audit con-ducted by the NRC. A summary of these supports is provided below:
1.
A total cf 135 supports on Turkey Point Unit 3 were identified as requiring inspection based on a comparison in the scope of inspections previously perfora d with the scope of Seismic Category I systems defined under I.E.Bulletin 79-14.
A total of 26 supports on Seismic Category I systems shared by Turkey Point Units 3 and 4 were identified as requiring inspection based on a similar comparisor.
in scope.
2.
A total of 234 supports on Turkey Point Unit 4 we re identified as requiring further inspection based on a review of previous inspection documenta-tion for these supports.
The expansion anchors for these remaining supports will be evaluated and reported as an integral part of the in-progress work under I.E.Bulletin 79-14.
This approach is justified based on the fo11 ewing reasons:
1.
The Seismic Category I systems associated with tnese supports have been designed for Safe Shutdown Earth-quake loads equivalent to three times the Operating Basis Earthquake. Current state of the art indicates that loads based upon two times the Operating Basis Earthquake would be conservative.
In addition, the probability of a seismic event is considered remote since the Turkey Point site is located within Zone I on the Seismic Probability Map spccified by ANSI A58.1, 1972.
2.
The occurrence of a seismic event would only require 25 percent of the anchorage capacity of the bolts in the remaining supports.
3.
The I.E.Bulletin 79-14 program currently includes evaluation of all seismic Category I large bore and dynamically analyzed small bore piping supports and associated expansion anchor bolts based upon as-built conditions.
This program provides for inspection, evaluation or repair of the expansion anchors based on final verified loads.
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EXHIBIT 1 TURKEY POINT UNITS 3 AND 4 - SYSTEMS COVERED BY SURVEILLANCE PROGRAM IN RESPONSE TO NRC IE BULLETIN 79-02, MARCH 8, 1979, REVISION 1, JUNE 21, 1979 and REVISION 2, NOVEMBER 8, 1979.
1.
F.eactor Coolant System 2.
Residual Heat Removal / Low Head Safety Injection System 3.
Containment Spray System l
4.
High Head Safety Injection System 5.
Chem; cal and Volume Control System 6.
Post-Accident Contain=ent Vent System 7.
Main Steam System 8.
Auxiliary Feed Water Sys tem 9.
Feedwater System 10.
Component Cooling Water System 11.
Intake Cooling Water System 1
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Diesel Generator Fuel Oil System 13.
Containment Isolation System i
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