L-79-186, Forwards Final Rept Responding to IE Bulletins 79-02 & 02,Revision 1,re Pipe Support Base Plate Designs Using Concrete Expansion Anchor Bolts.Table Encl W/Results of Insp & Testing,Nonconformances & Deficiencies
| ML19276G945 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 07/09/1979 |
| From: | Robert E. Uhrig FLORIDA POWER & LIGHT CO. |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| L-79-186, NUDOCS 7908310032 | |
| Download: ML19276G945 (15) | |
Text
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P. O. BOX 013100, MlAMI, F L 33101 FLORIDA POWER & LIGHT COVPANY July 9, 1979 Mr. James P. O'Reilly, Director, Region II L-79-186 Office of Inspection and Enforcement b
U. S. Nuclear Regulatory Commission v
101 Marietta Street, Suite 3100
[;
Atlanta, Georgia 30303 c
Dear Mr. O'Reilly:
c Re:
RII:JP0 50-250, 50-251 o
IE Bulletin 79-02 In accordance with I.E. Bulletin No. 79-02, dated March 8,1979 and Revision 1 dated June 21, 1979, find enclosed our final report for Turkey Point Unit 4 on pipe support base plate designs using concrete expansion anchor bolts.
As required by I.E.Bulletin 79-02 (Revision 1), we have evaluawu use results of the Unit 4 test and inspection program considering the gen-eric applicability to Turkey Point Unit No. 3.
It is concluded that continued operation of Turkey Point Unit 3 until the next scheduled unit outage does not constitute a safety problem for the following reasons :
a) The Seismic Category I Systems under consideration have been designed for SSE 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 Turkey Point Plant site is located within Zone 1 on the Seismic Probability Map specified by ANSI A58.1,1972.
b) The pass / fail criteria used during the Unit 4 test program conser-vatively assumes nonconfonnance based upon a factor of safety of five.
It should be noted however that for factored loadings, a factor of safety of three could have been used pursuant to the provisions of Section B.7.2 of the Proposed Addition to Code Re-quirements for Nuclear Safety Related Concrete Structures ( ACI 349-76),
August 1978.
c) The majority of the assumed nonconformances on Unit 4 were on small bore piping.
A chart method analysis was used for the original design of small bore pipe supports.
Evaluation of the chart method indicated that at least twice the support span could have been used, thereby negat':ng the necessity of every other support to maintain the safe ope ability of the system.
Evaluation also indicates that actual seismic loads en small bore piping beyond the first pipe anchor are relatively low.
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RII:JP0 50-250, 50-251 IE Bulletin 79-02 Page 2 In spite of the ultra conservative analysis, very strict pass / fail cri-teria were used during the Unit 4 test program, thereby exaggerating the significance of the results.
The acceptance criteria were based on the assumption that all supports were required. The acceptance criteria also conservatively required a determination of nonconformance if full cr~ engagement of the shell arrthor (100% of ultimate strength) did not exist in the as-found con-dition.
With relatively small loads on these supports less than full cone engagement would have been acceptable.
Since the safety systems are conservatively designed for low probability events (the occurrence of which would only then require the 25% ultimate capacity of an anchorage), we concur with the NRC position stated in IE Bulletin 79-02 that it is not necessary to shutdown a plant for purposes of performing the required inspections.
The advantage of per-forming tests on the accessible Unit 3 supports while the plant is operating is not considered significant when evaluated against the possible undue risk involved in disassembly of loaded supports during operation and the short time between now and the next scheduled refueling, when testing will be performed.
The Unit No. 3 base plate flexibility analysis is currantiv in progress.
Based upon the above evaluations and conclusions, a program similar to that used for Unit No. 4 will be used for Unit No. 3 with inspection and testing uheduled during the next outage for Unit No. 3.
Ver
- yours,
- q j{
f f 4ue obert E. Uhrig Vice President Advanced System & Technology REU/ MAS / mal Attachment cc:
Robert Lowenstein, Esquire
.?O.3 236
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FLORIDA POJER 6 LIGHT COMPANY TURKEY POD T UNIT No. 4 REPORT O';
PIPE SUPPORT EASE PIATE DESIGNS USH;G CONCRETE EXPA';SION ARCHOR BOLTS (In Response to NRC IE Bulletin 79-02, March 8, 1979 and NRC IE Bulletin 79-02 (Revision 1), June 21,1979) 2035 237 Bechtel Power Corporation Caithersburg, Maryland l
3-Ae oc W
t TABLE OF CONTEt,TS SECTION Page I.
INTRODUCTION 1
II.
RESPONSE TO ACTION ITEPS 1
ATTACHMEt,'TS Exhibit 1 Turkey Point Unit 4 - Systems covered Table 1 Results of Unit 4 Inspection and Tests
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FLORIDA PO'JER 6 LIGRI COMPANY TURKEY POINT UNIT No. 4 REPORT ON PIPE SUPPORT BASE FLATE DESIGNS USING CONCRETE EXPAUSION ANCHOR BOLTS (In Response to NRC IE Bulletin 79-02, March 8,1979 and NRC IE Bulletin 79-02 (Revision 1), June 21, 1979)
I.
INTRODUCTION This report is in response to NRC IE Bulletin 79-02, March 8, 1979, and NRC IE Bulletin 79-02 (Revision 1), June 21,1979, requiring all licensees and permit holders for nucicar power plants to review the design and installa-tion procedures for concrete expansion anchor bolts used in pipe support base plates in systems defined as Seistic Category I by NRC Regulatory Guide 1.29, "Scismic Design Classification," Revision 1, August 1973, or by the applicable SAR. Exhibit 1 provides the list of systems covered by this response to NRC IE Bulletin 79-02.
In accorlance with the intent of Bulletin 79-02, the following types of supports have been considered in the present review:
a.
Pipe anchors (Seismic Category I Restraints) b.
Pipe supports (Seismic Category I Hangers)
As of the cubmittal date of this report, all testing, inspecting, analysis, and repairs for Unit 4 have been completed.
Section II of this report provides responses to action items as presented in Revision 1 to IE Bulletin 79-02.
II.
RESPONSE TO ACTION ITEMS 1.
Verify that pipe support base plate flexibility was accounted for in the calculation of anchor bolt loads.
In lieu of supporting analysis justifying the assumption of rigidity, the base plates should be considered flexible if the unstiffened distance between the member welded to the plate and the edge of the base plate is greater than twice the thickness of the plate.
It is recognized that this criterion is concervative.
Less conservative acceptance 1
'>035 239
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 re:dculate the bolt loads using an appropriate analysis.
If possible, this is to be done prior to testing of anchor bolts.
These calculated bolt bolt design loads.
loads are referred to hereafter as the A description of the analytical model ud;d to verify that pipe support base pinte ficxibility is accounted for in the calculation of anchor
~
bolt loads is to be submitted with your response to the Bulletin.
It has been noted that the schedule for analytical work on base plate flexibility for some facilities extends beyond the Bulletin reporting time frame of July 6,1979, For those facilities for which an anchor bolt testing program is required (i.e., sufficient QC i
documentation does not exist), the anchor bolt testing program should not be delayed.
i
RESPONSE
All Category I pipe ane5or and support base plates using e.:pansion l
anchor / bolts were rr lyzed to account for plate flexibility, bolt stif fness, she: c-tension interaction, minimum edge distance, and proper bolt spating. Depending on the complexibility of the indi-vidual base plate configuration, one of the following methods of analysis was used to determine the bolt forces:
A quasi-analytical method, developed by Bechtel, was used for a.
base pintes with eight bolts or less. An analytical forcala-
{
tion has been developed for the base plates which treats the plates as a beam on multiple spring supports subjected to mos-ents and forces in three orthogonal directions.
Based on analytical considerations as well as the results of a nu=ber of representative finite elenent analyses of base plates (using the "AUSYS" Code), certain empirical factors were introduced in I
the simplified beam model to account for (a) the effect of con-crete foundation and (b) the two-way action of load transfer in a plate. These factors essentially provided a way for intro-ducing the interaction effect of parametric variable such as plate dimensions, attachment sizes, bolt spacings, and stiff-nesses on the distribution of external loads to the bolts.
The results of a number of case studies indicated excellent correlation between the results of the present formulation and those by the finite clement method (using the ANSYS Code).
The quasi-analytical method generally predicts bolt loads larger than the finite element method.
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Although the effect of plate flexibility has been considered explicitly in the quasi-analytical 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 governed 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 anchorage
~
capacity.
2)
Where the bolt pull out determines the anchorage capacity, the additional load carried by the bolt due to the prying action vill be self-limiting since the bolt stif fress decreases with increasing load. At higher loads the bolt extension will be such that the corners of the base plate will lift 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 program for the analytical technique described above has been implemented for determining the bolt loads for routine applications.
The program requires plate dimensions, number of bolts, bolt size, bolt spacing, bolt stiffness, and the allowable bolt shear and tension loads as inputs.the applied forces allowable loads for a given bolt are determined based on theThe concrete edge distance, bolt spacing, embedment length, shear cone overlapping, manufacturer's ultimate capacity, and a design safety factor.
The program computes the bolt forces and calculates a shear-tension interaction value based on the allowable loads.
The shear-tension interaction in the anchor bolts has been accounted for in the following manner:
1)
Where the applied shear force is less than the frictional force developed in the shear plane between the steel and the concrete surface for balancing the icposed loads no additional provisions are required for shear.
2)
Otherwise, the total applied shear is required to be carried by the bolts in accordance with the following in-teraction formula
( -)
+ ( -)
$ 1.0 Where T and S are the calculated te nsile and shear forces and Tg and SA are the respective allowable values.
3 b).h L4)
b.
for special cases where the design of the support did not lend itself to the foregoing method, one of the following standard engineering analytical techniques with conservative-assumptions was employed in the analysis:
1)
Conventional rigid plate analysis was performed to determine actual bolt tension load. An amplification factor of 1.5 was applied to account for prying action due to base plate flexibility. This amplification factor is considered con-servative based on the AISC Hanual of Steel Construction, Part 4 (Connections in Tension) and the results of case studies performed by the finite element 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-most face of the welded attach =ent was used.
2.
Verify that the concrete expansion anchor bolts have the following minimum factor of safety between the bolt design load and the bolt ultimate 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 strength properties):
a.
Four - For wedge and sleeve-type anchor bolts b.
Five - For shell-type anchor bolts The bolt ultimate capacity should account for the effects of shear-tension interaction, minimum edge distance and proper bolt spacing.
If the minimum factor of safety of four for wedge type anchor bolts and five for shell type anchors cannot be shown then justification must be provided.
RESPONSE
A reanalysis of all expansion bolts for pipe anchors and pipe supports for the systems presented in Exhibit 1 was performed for Unit 4 using the analytieni methods described in the response to action item No. 1.
l Less than one percent was found not to be in conformance with the i
minimum factors of safety of 4 for wedge type or 5 for self-drilling i
type, as appropriate, per IE Bulletin 79-02.
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3.
Describe the design requirements if applicable for anchor bolts to j
vithstand cyclic loads (e.g., seismic loads and high cycle operating loads).
i l
7035 242
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RES PONSE:
The original design of the piping systems considered deadwe'ight, thermal stresses, seismic loads, and dynamic loads (including steam hammer in the main steam systes) in the generation of the static :quivalent 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 factors 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 same safety factor for cyclic and static loads is based on the TFIF Tests *.
The test'results indicate:
l The expansion anchors successfully withstood two million a.
cycles of long-term fatigue loading at a maximum intensity of 0.20 of the static ultimate capacity.
When the maximum load intensity was increased steadily beyond the aforementioned value and cycled for 2,000 times at each load step, 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 loadi.,, was about the same as their corresponding static ultimate capacities.
i l
4 Verify from existing QC documentation that design requirements have been met for each anchor bolt in the following areas:
i I
Cyclic loads have been considered (e.g., anchor bolt preload a.
is equal to or greater 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 embedment depth).
If sufficient documentation does not exist, then initiate a testing that vill assure that minimum design requirements have been progra met with respect to sub-items a. and b. above. A sa=pling technique is acceptabic.
One acceptable technique is to randomly select and test one anchor bolt in each base plate (i.e., some supports may have more than one base plate).
The test should provide verification of sub-items a. tnd b. above.
- Drilled-In Expansion Bolts Uader Static and Alternating Loads, Report BR-5853-C-4, Revision 1, Bechtel Power Corp., October 1976.
?h3.b 24
similarly tested.If the test fails, all other bolts on the base plate should b In any event, e
that each Seismic Cetegory I system will perform 'its i tthe test program sh function.
n ended The prefer. ed test method to demonstrate that bolt preload h been accomplished in using a direct pull (tensile test) equ l t as or greater than design load.
a o
meth5d such a, to accessibility in some areasRecognizing this method difficult dus an alternative test used it must b, torque testing may be used.
If torque testing is torque and tens int exists.shown and substantiated that a correlation between bolt used is not available, or is not used, thenIf manufacturer's data for the must be developed
- site specific data
,__liff
-* ' tests.
Bolt test values of one-fourth (wedge type) or one-fif th (sh ll type) of bolt ultimate capacity may be used in lieu of indi id e
be conservative. calculated bolt design loads where the test value can be sho v ually o
The purpose of Bulletin 79-02 and this revision is to assur operability of each seismic Category I piping system.
e the an evaluation to confirm system operability must be performed In all cases of a multi-unit site which threatens operability of saf If units at that site must be ic=ediately evaluated and r the NRC.
of the identified failures.The evaluation must consider the Beneric applicability Appendix A describes two sampling methods for testing that c used.
an be Those options may be selected on a system by system bas Justification for omitting certain bolts from sa=ple testing whi h are in high radiation areas during an outage must be based on other c
testing or analysis which substantiates operability of th system.
e affected Bolts which are found during the testing progres not to be prel to a load equal to or greater than bolt design load must be oaded detrbmental t'o cyclic loading capability.preloaded or it must properly a tension load on any of the bolts does not exist for all loadingIf it can be cases then no preload or testing of the bolts is required If anchor bolt testing is done prior to completion of the analyti work on base plate flexibility, the bolt testing must be performed cal to at leaat the original calculated bolt load in the calculated bolt load due to base plate flexibitity ase of these factors must be verified. completion of the an.alytical work on t After s
?n;S 244
For base plate supports using expansion anchors, but raised from the supporting surface with grout placed under the base plate, for testing purposes it must be verified that 1cveling nuts were not used.
If leveling nuts were tsed, then they must be backed off such that they are not in contact with the base plate before apply-ing tension or torque testing.
Bulletin No. 79-02 requires verification by inspection that bolts are-properly installed and are of the specified size and type.
Parameters which should be included are embedment depth, thre:d 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 diameter or less were computer analyzed then they must be treated the same as the larger piping.
If a chart analysis method 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 sa=pling inspection.
The parameters inspected shculd include those descibed in the preceding paragraph.
If small diameter piping is not inspected, then justification of system operability must be provided.
RESPONSE
Design requirements of anchor bolts for cyclic loads have been discussed in the response to action item 3.
A jobsite inspection and testing progren has been completed which provided for 100 percent verification of all expansion bolts for both large bore and small bore pipe anchors and supports for Seismic Category I portions of the systems presented in Exhibit 1.
A total of 553 large bore (greater than 2 inches) and 653 small bore ( 2 inches or less) pipe anchors / supports were inspected, tested, and evaluated for Unit 4.
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 accordance with written procedures. These procedures and records of inspection, testing, and repairs are availabic at the Turkey Point Jobsiteforgnspection.
The program provided that the following information be verified, recorded, evaluated and corrected, as required:
1)
Support plate conforms to design details, plate
~
dimensions, plate thickness, and bolt configuration (number of bolts, spacing, edge distance, bolt hole
, size).
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2)
Anchor bolt length, diameter, embedment depth, type.
3)
Anchor bolt projection.
4)
Nut / thread engagement.
5)
Pins and washers (on wedge type).
4)
Washers (on self-drilling type).
7)
Gap between plate and self-drill anchor sleeve.
8)
Leveling nute backed off prior to torquing.
9)
Minimum torque achieved equivalent to preload of one-fourth ultimate tension capacity for wedge anchors and one-fifth ultimate tension capacity i
for self-drilling anchors.
I i
10)
Full expansion of shell (on self-drilling type).
All supports with inaccessible or nonconforming bolts were reanalyzed using one of the analytical methods discussed in the response to action item 1 and l
repaired in accordance with written procedures.
When required, self-drilling i
type' anchor bolts were replaced with wedge type anchor bolts.
I, j
A summary of Unit 4 inspection and test findings is given in Table 1 to this report.
It should be noted that the significance of these findings are l
cxaggerated for the following reasons:
I a)
The Seismic Category I Systems under consideration have been designed for SSE 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 Turkey Point Plant site is located within Zone 1 on the seismic Probability Hap specified by ANSIA 58.1, 1972 b) The pass / fail criteria used during the Unit 4 test program conservatively assume nonconformance based upon a factor of safety of five.
It should be noted however that for factored loadings, a factor of safety of three 1
could have been used pursuant to the provisions of Section B.7.2 of the Proposed Addition to Code Requirements for Nuclear Safety Related Concrete Structures (ACI 349-76), August 1978.
c) The majority of the assumed nonconformances on Unit 4 were on small bore piping.
A chart method analysis was used for the original design of small bore pipe supports.
Evaluation of the chart method indicated that at least twice the support span could have been used, thereby, negating the necessity of every other support to r..aintain the safe operability of
?035 246 l
8
the system.
Evaluation also indicates that actual seismic loads on small bore piping beyond the first pipe anchor are relatively low.
In spite of the ultra conservative analysis, very strict pass / fail criteria were used during the Unit 4 test program, thereby, exaggerat-ing the significance of the results.
The acceptance criteria were based on the assumption that al~1 supports
,ere required.
The acceptance criteria also conservatively required a w
determination of nonconformance if full cone engagement of the shell anchor (100% of ultimate strength) did not exist in the as-found condition.
With relatively small loads on these supports, less than full cone engagement would have been acceptable.
Since the safety systems are conservatively designed for low probability events ( the occurrence of which would only then require the 25% ultimate capacity of an anchorage), we concur with the NRC position stated in IE Bulletin 79-02 that it is not necessary to shutdown a plant for purposes of performing the required inspections.
The advantage of performing tests on the accessible Unit 3 supports while the plant is operating is not considered significant when evaluated against the possible undue risk involved in disassembly of loaded supports during operation and the short time between now and the next scheduled refueling uhen testing will be performed.
I The Unit No. 3 base plate flexibility analysis is currently in progress.
Based upon the above evaluations and conclusions, a program similar to that used for Unit No. 4 will be used for Unit No. 3 with inspection and testing scheduled during the next outage for Unit No.
3.
?035 247 m
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EXHIBIT 1 TURKEY POINT UNIT NO. 4 - SYSTEMS COVERED BY SURVEILIANCE PROGRAM IN RESPONSE TO 1RC IE BULLETIN 79-02, MARCH 8,1979
- AND RL/.SION 1, JUNE 21, 1979 1.
Reactor Coolant Syste:s 2.
Residual Heat Re:noval/ Low Head Safety Injection System 3.
Containment Spray System 4.
High Head Safety Injection Systea 5.
Chemical and Volu:ne Control Syste:a 6.
Post-Accident Containment Vent System I
7.
Main Steam System 8.
Auxiliary Feedwater System 9.
Feedwater System 10.
Component Cooling Water System 11.
Intake Cooling Water Syste:s i
12.
Diesel denerator Fuel Oil System 13.
Containment Isolation System
s' e
TABLE I RESULTS OP UNIT 4 It1SPECTIO!1 A!JD TESTItJG Total of 553 Large Total of 653 Small Bore (greater than 2")
Bore (2" or less)
Pipe Supports / Anchors Pipe Supports / Anchors (1)
(2)
~
No. of Non-No. of No. of Non-No. of conformances Deficiencies conformances Deficiencic:
Shell Expansion for Shell Type 54 6
144 3
Minimum embedment - Wedge Type 4
7 23 5
Inaccessible Bolt (s) 2 0
18 O
Damaged Bolt (s) 2 0
5 1
Missing Bolt (s) 6 3
5 5
Bolt (s) Sheared During Test 9
8 34 4
Torque Not Achieved 24 8
6 2
Shell in Contact with Plate 25 14 32 15 Thread Engagement 8
1 11 6
Damaged Washer /Inc - Wedge 3
11 0
1 Missing Uasher - Shell Type O
O 4
1 Bolt Diameter Not As Specified 2
0 0
0 Itoles in Plate Oversized 1
0 0
0 i
Note (1) - A noncomformance fails the catablished acceptance criteria and must be repaired / replaced.
Note (2) - A deficiency satisfies the functional requirements of the design and may be corrected at a later date.
9035 249 i
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a