Bulletin 79-02: (Revision 2), Pipe Support Base Plate Designs Using Concrete Expansion Anchor Bolts
SSINS No.: 6820
Accession No.:
7908220136
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
November 8, 1979
IE Bulletin No. 79-02
(Revision 2)
PIPE SUPPORT BASE PLATE DESIGNS USING CONCRETE EXPANSION ANCHOR BOLTS
Description of Circumstances:
Inspection experiences and the review of licensee response have R2
identified several areas where the Bulletin intent has not been R2
adequately addressed by licensees. Revision No. 2 of the Bulletin is R2
intended to clarify the intent of the Bulletin and establish the NRC R2
positions on minimum factors of safety, anchor bolt preload, and the R2
expected date of completion for certain Bulletin actions. R2
Since the issuance of IE Bulletin No. 79-02 on March 8, 1979, IE R1
inspection experience and many inquiries from licensees indicate that R1
additional information and clarification is needed. This revision is R1
intended to serve that purpose. None of the requirements of the original R1
Bulletin have been deleted, and the due date for completion of the R1
requested actions (July 6, 1979) has not been changed. The following R1
text supersedes the text of Bulletin No. 79-02. Changes from the R1
original text are identified by RI and R2 in the margin. The purpose of R1
this revision is to identify acceptable ways of satisfying the Bulletin R1
requirements. R1
While performing inservice inspections during a March-April 1978 refueling
outage at Millstone Unit 1, structural failures of piping supports for safety
equipment were observed by the licensee. Subsequent licensee inspections of
undamaged supports showed a large percentage of the concrete anchor bolts
were not tightened properly.
Deficiency reports, in accordance with 10 CFR 50.55(e), filed by Long Island
Lighting Company on Shoreham Unit 1, indicate that design of base plates
using rigid plate assumptions has resulted in underestimation of loads on
some anchor bolts. Initial investigation indicated that nearly fifty percent
of the base plates could not be assumed to behave as rigid plates. In
addition, licensee inspection of anchor bolt installations at Shoreham has
shown over fifty percent of the bolt installations to be deficient.
Vendor Inspection Audits by NRC at Architect Engineering firms have shown a
wide range of design practices and installation procedures which have been
employed for the use of concrete expansion anchors. The current trends in the
industry are toward more rigorous controls and verification of the
installation of the bolts.
The data available on dynamic testing of the concrete expansion anchors show
fatigue failures can occur at loads substantially below the bolt static
R1 and R2 - Identifies those additions or revisions to IE Bulletin No. 79-02
.
IE Bulletin No. 79-02 November 8, 1979
Revision 2 Page 2 of 7
capacities due to material imperfections or notch type stress risers. The
data also show low cycle dynamic failures at loads below the bolt static
capacities due to joint slippage.
In the review of anchor bolt installation practices, three facilities R2
(Trojan, Duane Arnold, and Zimmer) have been identified which use R2
expansion anchor bolts in concrete block walls to attach Seismic R2
Category I piping supports. Testing results of anchor bolts in concrete R2
block walls performed at FFTF indicate significantly lower ultimate R2
capacities than for those in concrete. An Information Notice will be R2
issued which provides additional details on the deficiencies identified R2
at Trojan. R2
In the review of responses to the Bulletin, we have become aware that R2
licensees may not have included review of piping supports with concrete R2
expansion anchor bolts which did not use base plates. Such supports use R2
structural steel members (angle or channel) attached directly to the R2
concrete by expansion anchor bolts, with the piping attached to the R2
structural steel member. The adequacy of the anchor bolt design and R2
installation should be verified to satisfy the intent of the Bulletin. R2
Action to be Taken by Licensees and Permit Holders:
This Bulletin addresses those pipe support base plates that use concrete R1
expansion anchor bolts in Seismic Category I systems as defined by
Regulatory Guide 1.29, "Seismic Design Classification" Revision 1, dated
August 1973 or as defined in the applicable FSAR. For older plants where R1
Seismic Category I requirements did not exist at the time of licensing R1
it must be shown that piping supports for safety related systems, as R1
defined in the Final Safety Analysis Report, meet design requirements. R1
The revision is not intended to penalize licensees who have already R1
completed some of the Bulletin requirements. In those instances in which R1
a licensee has completed action on a specific item and the Bulletin R1
revision provides more conservative guidance, the licensee should R1
explain the adequacy of the action already performed. It should be R1
reiterated that the purpose of the Bulletin actions are to assure R1
operability of Seismic Category I piping systems in the event of a R1
seismic event.
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 R1
twice the thickness of the plate. It is recognized that this R1
criterion is conservative. Less conservative acceptance criteria R1
must be justified and the justification submitted as part of the R1
response to the Bulletin. If the base plate is determined to be R1
flexible, then recalculations the bolt loads using an appropriate R1
analysis. If possible, this is to be done prior to testing of anchor
bolts. These calculated bolt loads are referred to hereafter as the R1
bolt design loads. A description of the analytical model used to R1
verify that pipe support base plate flexibility is accounted for in R1
the calculation of bolt loads is to be submitted with your response R1
to the Bulletin. R1
.
IE Bulletin No. 79-02 November 8, 1979
Revision 2 Page 3 of 7
It has been noted that the schedule for analytical work on base R1
plate flexibility for some facilities extends beyond the Bulletin R1
reporting time frame of July 6, 1979. For those facilities for R1
which an anchor bolt testing program is required (i.e., sufficient R1
QC documentation does not R exist), the anchor bolt testing program R1
should not be delayed.
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 R1
shear-tension interaction, minimum edge distance and proper bolt R1
spacing.
If the minimum factor of safety of four for wedge type anchor bolts R1
and five for shell type anchors can not be shown then justification R1
must be provided. The Bulletin factors of safety were intended for R1
the maximum support load including the SSE. The NRC has not yet R2
been provided adequate justification that lower factors of safety R2
are acceptable on a long term basis. Lower factors of safety are R2
allowed on an interim basis by the provisions of Supplement No. 1 R2
to IE Bulletin No. 79-02. The use of reduced factors of safety in R2
the factored load approach of ACI 349-76 has not yet been accepted R2
by the NRC. R2
3. Describe the design requirements if applicable for anchor bolts to with-
stand cyclic loads (e. g. seismic loads and high cycle operating loads).
4. Verify from existing QC documentation that design requirements have been
met for each anchor bolt in the following areas:
(a) Cyclic loads have been considered (e.g. anchor bolt preload 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
program that will assure that minimum design requirements have been met
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 have more than
one base plate). The test should provide verification of sub-items (a)
and (b) above. If the test fails, all other bolts on that base plate
should be similarly tested. In any event, the test program should assure
that each Seismic Category I system will perform its intended function.
.
IE Bulletin No. 79-02 November 8 , 1979
Revision 2 Page 4 of 7
The preferred test method to demonstrate the bolt preload has R1
been accomplished is using a direct pull (tensile test) equal to or R1
greater than design load. Recognizing this method may be difficult R1
due to accessibility in some areas an alternative test method such R1
as torque testing may be used. If torque testing is used it must be R1
shown and substantiated that a correlation between torque and R1
tension exists. If manufacturer's data for the specific bolt used R1
is not available, or is not used, then site RI specific data must R1
be developed by qualification tests.
Bolt test values of one-fourth (wedge type) or one-fifth (shell R1
type) of bolt ultimate capacity may be used in lieu of individually R1
calculated bolt design loads where the test value can be shown to R1
be conservative.
The purpose of Bulletin No. 79-02 and this revision is to assure R1
the operability of each seismic Category I piping system. In all R1
cases an evaluation to confirm system operability must be performed.R1
If a base plate or anchor bolt failure rate is identified at one R1
unit of a multi-unit site which threatens operability of safety R1
related piping systems of that unit, continued operation of the R1
remaining units at that site must be immediately evaluated and R1
reported to the NRC. The evaluation must consider the generic R1
applicability of the identified failures.
Appendix A describes two sampling methods for testing that can be R1
used. Other sampling methods may be used but must be justified. R1
Those options may be selected on a system by system basis. R1
Justification for omitting certain bolts from sample testing which R1
are in high radiation areas during an outage must be based on R1
other testing or analysis which substantiates operability of the R1
affected system. R1
Bolts which are found during the testing program not to be R1
preloaded to a load equal to or greater than bolt design load must R1
be properly preloaded or it must be shown that the lack of R1
preloading is not detrimental to cyclic loading capability. Those R2
licensees that have not verified anchor bolt preload are not R2
required to go back and establish preload. However, additional R2
information should be submitted which demonstrates the effects of R2
preload on the anchor Colt ultimate capacity under dynamic loading. R2
If it can be established that a tension load on any of the bolts R1
does not exist for all loading cases then no preload or testing of R1
the bolts is required. R1
If anchor bolt testing is done prior to completion of the R1
analytical work on base plate flexibility, the bolt testing must be R1
performed to at least the original calculated bolt load. For R1
testing purposes factors may be used to conservatively estimate the R1
potential increase in the calculated bolt load due to base plate R1
flexibility. After completion of the analytical work on the base R1
plates the conservatism of these factors must be verified. R1
.
IE Bulletin No. 79-02 November 8, 1979
Revision 2 Page 5 of 7
For base plate supports using expansion anchors, but raised from R1
the supporting surface with grout placed under the base plate, for R1
testing purposes it must be verified that leveling nuts were not R1
used. If leveling nuts were used, then they must be backed off such R1
that they are not in contact with the base plate before applying R1
tension or torque testing. R1
Bulletin No. 79-02 requires verification by inspection that bolts R1
are properly installed and are of the specified size and type. R1
Parameters which should be included are embedment depth, thread R1
engagement, plate bolt hole size, bolt spacing, edge distance to R1
the side of a concrete member and full expansion of the shell for R1
shell type anchor bolts. R1
If piping systems 2 1/2-inch in diameter or less were computer R1
analyzed then they must be treated the same as the larger piping. R1
If a chart analysis method was used and this method can be shown R1
to be highly conservative, then the proper installation of the base R1
plate and anchor bolts should be verified by a sampling inspection.R1
The parameters inspected should include those described in the R1
preceding paragraph. If small diameter piping is not inspected, R1
then justification of system operability must be provided. R1
5. Determine the extent that expansion anchor bolts were used in R2
concrete block (masonry) walls to attach piping supports in Seismic R2
Category 1 systems (or safety related systems as defined by R2
Revision 1 of IE Bulletin No. 79-02). If expansion anchor bolts R2
were used in concrete block walls:
a. Provide a list of the systems involved, with the number of R2
supports, type of anchor bolt, line size, and whether these R2
supports are accessible during normal plant operation. R2
b. Describe in detail any design consideration used to account R2
for this type of installation. R2
c. Provide a detailed evaluation of the capability of the R2
supports, including the anchor bolts, and block wall to meet R2
the design loads. The evaluation must describe how the R2
allowable loads on anchor bolts in concrete block walls were R2
determined and also what analytical method was used to R2
determine the integrity of the block walls under the R2
imposed loads. Also describe the acceptance criteria, R2
including the numerical values, used to perform this R2
evaluation. Review the deficiencies identified in the R2
Information Notice on the pipe supports and walls at Trojan R2
to determine if a similar situation exists at your facility R2
with regard to supports using anchor bolts in concrete block R2
walls. R2
d. Describe the results of testing of anchor bolts in concrete R2
block walls and your plans and schedule for any further action.R2
6. Determine the extent that pipe supports with expansion anchor bolts R2
used structural steel shapes instead of base plates. The systems R2
and lines R2
.
IE Bulletin No. 79-02 November 8, 1979
Revision 2 Page 6 of 7
reviewed must be consistent with the criteria of IE Bulletin No. R2
79-02, Revision 1. If expansion anchor bolts were used as described R2
above, verify that the anchor bolt and structural steel shapes in R2
these supports were included in the actions performed for the R2
Bulletin. If these supports cannot be verified to have been R2
included in the Bulletin actions: R2
a. Provide a list of the systems involved, with the number of R2
supports, type of anchor bolt, line size, and whether the R2
supports are accessible during normal plant operation. R2
b. Provide a detailed evaluation of the adequacy of the anchor R2
bolt design and installation. The evaluation should address R2
the assumed distribution of loads on the anchor bolts. The R2
evaluation can be based on the results of previous anchor R2
bolt testing and/or analysis which substantiates operability R2
of the affected system. R2
c. Describe your plans and schedule for any further action R2
necessary to assure the affected systems meet Technical R2
Specifications operability requirements in the event of an R2
SSE. R2
7. For those licensees that have had no extended outages to perform R2
the testing of the inaccessible anchor bolts, the testing of R2
anchor bolts in accessible areas is expected to be completed by R2
November 15, 1979. The testing of the inaccessible anchor bolts R2
should be completed by the next extended outage. For those R2
licensees that have completed the anchor bolt testing in R2
inaccessible areas, the testing in accessible areas should continue R2
as rapidly as possible, but no longer than March 1, 1980. The R2
analysis for the Bulletin items covering base plate flexibility R2
and factors of safety should be completed by November 15, 1979. R2
Provide a schedule that details the completion dates for IE R2
Bulletin No. 79-02, Revision 2, items 1, 2, and 4. R2
8. Maintain documentation of any sampling inspection of anchor bolts R2
required by item 4 on site and available for NRC inspection. All R2
holders of operating licenses for power reactor facilities are R2
requested to complete items 5, 6, and 7 within 30 days of the date R2
of issuance of Revision No. 2. Also describe any instances not R2
previously reported, in which you did not meet the revised (R2) R2
sections of items 2 and 4 and, if necessary, your plans and R2
schedule for resolution. Report in writing within 30 days of the R2
date of this revision issuance, to the Director of the appropriate R2
Regional Office, completion of your review. For action not yet R2
complete, a final report is to be submitted upon completion of R2
your action. A copy of your report(s) should be sent to the United R2
States Nuclear Regulatory Commission, Office of Inspection and R1
Enforcement, Division of Reactor Operations Inspection, Washington, R1
D.C. 20555. These reporting requirements do not preclude nor R1
substitute for the applicable requirements to report as set forth R1
in the regulations and license. R1
9. All holders of construction permits for power reactor facilities R2
are requested to complete items 5 and 6 for installed pipe supports R2
within 60 days of date of issuance of Revision No. 2. For pipe R2
supports which have not yet R2
.
IE Bulletin No. 79-02 November 8, 1979
Revision 2 Page 7 of 7
been installed, document your action to assure that items 1 through R2
6 will be satisfied. Maintain documentation of these actions on R2
site available for NRC inspection. Report in writing within 60 days R2
of date of issuance of Revision No. 2, to the Director of the R2
appropriate NRC Regional Office, completion of your review and R2
describe any instances not previously reported, in which you did R2
not meet the revised (R2) sections of items 2 and 4 and, if R2
necessary, your plans and schedule for resolution. A copy of your R2
report should be sent to the United States Nuclear Regulatory R2
Commission, Office of Inspection and Enforcement, Division of R2
Reactor Construction Inspection, Washington, D.C. 20555. R2
Approved by GAO (R0072); clearance expires 7/31/80. Approval was given under
a blanket clearance specifically for identified generic problems.
Enclosures: R1
1. Appendix A
2. Recently Issued IE Bulletins
.
APPENDIX A
SAMPLING METHODS
Item 4 of this Bulletin states that for anchor bolt testing purposes a
sampling program is acceptable. Two sampling methods are discussed below, but
other methods may be used if justified.
a. Test one bolt on each plate as originally recommended in Bulletin No.
79-02. If the test fails, all other bolts on that base plate should be
similarly tested. A high failure rate should be the basis for increased
testing.
b. Randomly select and test a statistical sample of the bolts to provide
a 95 percent confidence level that less than 5 percent defective anchors
are installed in any one seismic Category I system. The sampling program
should be done on a system by system basis.
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Page Last Reviewed/Updated Tuesday, March 09, 2021