United States Nuclear Regulatory Commission - Protecting People and the Environment

Bulletin 79-02: (Revision 2), Pipe Support Base Plate Designs Using Concrete Expansion Anchor Bolts

                                                            SSINS No.: 6820 
                                                            Accession No.:

                                UNITED STATES
                           WASHINGTON, D.C. 20555 

                              November 8, 1979 

                                                  IE Bulletin No. 79-02  
                                                  (Revision 2) 


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

     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

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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