Home > NRC Library > Document Collections > Generic Communications > Bulletins > 1979 > BL-79-02 (Revision 2)
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.
Page Last Reviewed/Updated Friday, May 22, 2015