ML19242B357

Responds to IE Bulletins 79-02 & 02,Revision 1.Most Plates Determined to Be Flexible as Defined by NRC 2:1 Ratio Criteria & Were Reanalyzed,Using Method Where Plate Flexibility,Anchor Preload & shear-tension Considered

ML19242B357
Person / Time
Site:	Perry
Issue date:	07/06/1979
From:	Davidson D CLEVELAND ELECTRIC ILLUMINATING CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
NUDOCS 7908080260
Download: ML19242B357 (17)

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• 43 LLECTF!C kJ ILLUMINATING BLDG.e PUBLIC SQUARE e CLEVELAND. OHIO 44101 e TELEPHONE (216) 623-1350 e MAIL ADDRESS. P. O. BOX 5000 w S+n  :? B- .> " .\ n o ,

Dalwyn R. Davidson vtCE PRE SIDE NT -

SYSTE M ENGINE E RtNG AND CONSTRUCTION July 6, 1979 Mr. James G. Keppler, Director Region III Office of Inspection and Enforce: ent U. S. Nuclear Regulatory Co mission .

799 Roosevelt Road Glen Ellyn, Illinois 60137 Re: Perry Nuclear Power Plant IE Bulletin Nos. 79-02, 79-02 Rev. 1 Dear Mr. Keppler-In accordance with your request, the enclosed attachments have been provided in response to IE Bulletins 79-02 and 79-02 Rev. 1.

Attachment 1 was prepared by our Architect / Engineer, Gilbert Associates, Inc., at our request to address the technical items of the Bulletins.

Attachment 2 is our response to Item 4 of the Bulletin regarding QC documentation.

If you have any questions regarding our response, please let me know.

Very truly yours,

'G 1- k ' 'r// fr Dal R. Davidson Vice esident System Engineering and Construction DRD/c=w Enclosures cc: bT. Victor Stello Office of Inspection and Enforcement U. S. Nuclear Regulatory Cor=ission Washington, D. C. 20555, ,

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July 2, 1979 ATTACFJGU 1 PERRY NUCLEAR POWER PLANT UNIT 1 & 2 NRC IE BULLETIN 79-02 (REV. 1)

1.0 INTRODUCTION

A detailed review was performed in response to the United States Nuclear Regulatory Commission (NRC) request, IE Bulletin.No. 72-02 (Rev. 1) " Pipe Support Base Plate Design Using Concrete Expansion Anchor Bolts", dated June 21, 1979 for Perry Nuclear Power Plant Unit 1&2, Docket Nos. 50-440 and 50-441. The review was performed on a representative sample of safety-related supports (Seismic Category I). Possible effects of base plate flexibility on base plate anchors were considered. This report presents the methods and results of the review.

2.0

SUMMARY

AND CONCLUSIONS 2.1 Summarv of Design Review

1. Most plates were determined to be flexible as defined by the NRC 2:1 ratio criteria. Therefore, plates were reanalyzed using a method in which the effects of plate flexibility, anchor preload and shear-tension interaction were considered. The results of the reanalysis generally confirmed the adequacy of the original design.

2. A representative sample consisting of 10 Perry designs and 96 similar designs were investigated. These Perry specific and similar designs are anchored with Hilti " Kwik-Bolts". The ca ?l1

analytical investigations indicate that approximately 5%

of the Perry designs may have a factor of safety less than 4.0 if plate flexibility is considered. These kinds of situations will be resolved as described in Section 3.6.

3. All Seismic Category I supports are potentially subject to a relatively low number of seismic loading cycles which can be accommodated by the design. Operational loads which could, during the lifetime of the plant, undergo a large number of load cycles are identified during startup testing, and modifi-cations to the pipe sup, rt system are made as required to assure that such loads are eliminated.

2.2 Summary of QC Documentation OR of In-Place Inspection Content to be provided by CEI.

2.3 Conclusion The resultu of the investigation for the effects of plate flexibility on pipe support base plate anchors indicate that, for most plates anchored to concrete surfaces with Hilti " Kwik Bolts", prying forces did not exist. Prying forces were found to be present in approximately 5% of the cases. In those cases the prying was responsible for an average increase in the bolt tension of less than 30%.

3.0 Review Results In consideration of the requested action, all base plates for large bore (2 " and larger) Safety Category I pipes are being reanalyzed.

There are approximately 500., base plates in the two units which fit this category.

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Small bore (2" and smaller diameter) pipe was designed using a seismic support spacing criteria. The :riteria was developed based on a conservative I pipe stress and a multi-span model for each pipe size and schedule. The model analysis provides pipe spans and support loads. This approach has been verified by sample computer analyses to be conservative relative to applicable code requirements.

A series of typical support designs were generated and load rated by analytical techniques. The supports were analyzed for structu-ral adequacy for all members, welds and the expansion anchor bolts.

In generating the load rating, the most conservative geometr; com-bination of the maximum distance from the pipe to the structure was used in conjunction with the smallest allowed spacing between expan-sion anchor bolts. This resulted in the worst load case.

The results of this conservative approach indicate that about 15% of the supports on any of the small bore piping runs could fail and the piping stresses would remain within code allowables. There-fore, detailed analyses and inspection of these expansion anchor bolts is considered unnecessary.

3.1 NRC Item 1 - Question Verify that pipe support base plate flexibility was acounted for in the calculation of anchor bolt loads. In lieu of supporting ana'." sis justifying the assumption of rigidity, the base plates should se considered flexible if the unstiffere ' distance between the sember

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welded to the plate and the edge cf the base plate is arco:.ar than twice the thickness of the plate. It is recognized that this cri-terion is conscrvative. Less conservative acceptance criteria must I

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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 seating of anchor bolts. These calculated bolt loads are referred to here-after as the bolt design loads. A description of the analytical model used to verify that pipe support base place flexibility 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 documentation does not exist), the anchor bolt testing program should not be delayed.

Response

Base plates were considered rigid in the original design. For re-examination of the base plates considering plate flexibility, pro-cedures were developed for the analysis of the plates and anchorages for moment and axial load applied to the plate surf aces. (Figures 1, 2, 3, and 4)

Wedge anchors were installed in accordance with manufacturer's recom-mendations. Bolts were to:qued to the degree necessary to ensure a preload equal to or greater than the allowable working load on the bolt. A field test program was conducted to establish for each bolt size the torque value required to ensure the required level of bolt tension.

The magnitude of the residual preload directly influences the plate rotation at the anchor, and full fixity against anchor rotation is obtained when:

e (Ti-V) (L) = V g

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Where T1

= Anchor residual preload V = Plate shear L = Effective edge distance of the plate from the tensile anchors e = Distance from the edge of the attachment to the tensile anchors With full fixity against anchor rotation, the plate deflection transverse to the surface of the plate at the face of the attachment is the same as support settlement of a member fixed at both ends.

As long as preload exceeds plate shear, some resistance to anchor rota-tion exists. When Ti < V, there is free rotation of the plate at the anchor, and the plate deflects as a cantilever.

Preloaded wedge anchors have a memory of their maximum load and will not experience inelastic displacements until a load larger than the installation preload occurs. At loadings less than the installation preload, the anchors will function essentially elastically even though the actual loading exceeds the residual preload on the anchor. If the actua! load is less than the residual preload, the bolt is ersentially prestressed, and the stress remains approximately constant under this load. The performance of a preloaded wedge anchor is the same under dynamic as under static loadings; that is, the anchor will not exper-ience inelastic displacements (in addition to that which occurs during installation) until the anchor is subjected to a load greater than the installation preload.

Based on the plate and anchor response as described above, procedures were developed to determine tensile forces in the anchors, as shown in Figures 1, 2, 3 and 4.

Shear and tension effects were combined cC\

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, directly to evaluate the f actor of safety of the anchors, with the shear force ing distributed equally to all anchors in the connec-tion. The method of combining these effects is described in Section 3.2.

3.2 NRC Item 2 - Question

" Verify that the concrete expansion anchor bolts have the following minimum f actor of saf ety 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

The concrete expansion anchor bolts used at Perry are the "Kwih Bolts" as manufactured by Hilti, Inc. This is a wedge type anchor required to have a minimum factor of safety of four (4) in accordance with aforementioned NRC Item 2a. The results of the re-analysis are summarized in attached Table 1.

The factor of safety against failure (F.S.) is conservatively deter-mined using the following shear-tension interaction equation:

(F.S.) (To) (F.S.) (So) _

, (Ta) (Sa)

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Where: F.S. = factor of safety against failure To =

Tension force induced into an anchor (considering plate flexibility)

Ta =

ultimate tension capacity of an anchor

• So =

Shear force induced into an anchor

=

Sa ultimate shear capacity of an anchor *,_

• From manufacturer's static load tests Expansion bolt placement in the structure is governed by the follow-ing criteria:

a. A minimum spacing between adjacent bolts of 10d, where d is the diameter of the bolt hole.

b. A nominal edge distance of 3 inches (+2 inches) between the bolt centerline and the edge of the base plate.

c. A minimum edge distance between the bolt centerline and the edge of a concrete member equal to 171/2d.

3.3 NRC ltem 3 - Question

" Describe the design requirements, if applicable, for anchor bolts to withstand cyclic loads (e.g. seismic loads and high cycle operat-ing loads)."

Response

Pipe support reactions are generated as an output of a dynamic analy-sis and are utilized for the design of the individual pipe supports.

Therefore, a dynamic amplification factor was not theoretically required. However, to provide for the effects of hardware and erec-tion tolerances, the OBE seismic part sf the reaction is multiplied by a factor of 2 to produce's design load. This factor provides additional design margin on the dynamic part of the loads.

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The governing load combination including the 2.0 factor is:

< Allowable Deadweight + Thermal +Seismic (2.0) OBE +Mechanical Occasional - Anchor Loads Bolt Load In order to ensure cyclic load carrying capability, wedge type anchors are installed by applying a torque of sufficient magnitude

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to set the wedges at a bolt preload equal to or greater than the maximum allowable working load.

3.4 NRC Item 4 - Question

" 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 pre-load is equal to or greater than bolt design load) . In the case of the shell type, assure that it is not in con-tact with the back of the support plate prior to preload testing.

b. Specified design size and type is correctly installed (e.g. proper embedment dep th) . "

"If sufficient documentation does not exist, then initiate a testing program that will assure that minimum design requirements have been met with respect to subitems (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 subitems (a) and (b) abnve. 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."

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 test method such as torque testing may be used. If torque testing is used it must be shown and substantiated that a correlation between 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 qualifica-tion tests. ,;

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Bolt test values of one-fourth (wedge type) cr one-fif th (shell type) of bolt ultimate capacity may be used in lieu of individually calculated bolt design loads where the test value can be shown to be conservative.

The purpose of Bulletin 79-02 and this revision is to assure the operability of each seismic Category I piping system. In all cases an evaluation to confirm system operability must be performed. If a base plate or anchor bolt failure rate is identified at one unit of a multi-unit site which threatens operability of safe ~ty related piping systems of that unit, continued operation of the remaining units at that site must be immediately evaluated and reported to the NRC. The evaluation must consider the generic applicability of tha identified failures.

Appendix A describes two sampling methods for testing that can be used. Other sampling methods may be used but must be justified.

Those options may be selected on a system-by-system basis.

Justification for omitting certain bolts 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 bolt design load must be properly preloaded or it must be shown that the lack of preloading is not detrimental to cyclic loading capability. If it can 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 is required.

If anchor bolt testing is done prior to completion of the analytical work on base plate flexibility, the bolt testing must be performed to at least the original calculated bolt load. For testing purposes, factors may be used to conservatively estimate the potential increase in the calculated bolt load due to base plate flexibility. After com-pletion of the analytical work on the base plates, the conservatism of these factors must be verified.

For base plate supports using expansion anchors, but raised from the supporting surface with grout placed under the base plate, for test-ing 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 applying tension or torque testing.

Bulletin No. 79-02 requiressverification by inspection chat bolts are properly installed and are of the specified size and typ'. Parameters 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. ,

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If piping systems 21/2-inch in diameter or less were computer analyzed then they must be treated the same as the largtr 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 sampling inspec-tion. The parameters inspected should include those described in the preceding paragraph. If small diameter piping is not inspected, then justification of system operability must be provide 3.

Response

Content to be provided by CEI.

3.5 NRC Item 5 - Question This question ooes not apply to the Perry Project.

3.6 NRC Item 6 - Question All holders of construction permits for power reactor facilities are requested to complete items 1 through 4 for installed pipe support base plates with concrete anchor bolts within 120 days of date of issuance of the Bulletin. No extension of time to complete notion requested in Bulletin 79-02 is granted by issuance of this revision of the Bulletin. For pipe support base plates which have not yet been installed, document your actions to assure that items 1 through 4 will be satisfied. Maintain documentation of these actions on site and available for NRC inspection. Report in writing within 120 days of date of Bulletin issuance, to the Director of the appropriate NRC Regional Office, completion of your review and describe any discrepan-cies in meeting items 1 through 4 and, if necessary, your plans and schedule for resolution. A copy of your report should be sent to the United States Nuclear Regulatory Commission, Office of Inspection and Enforcement, Division of Reactor Construction Inspection, Washing-ton, D.C. 20555.

Response

Analytical work and appropriate redesign to ensure that all pipe support base plates conform to the requirements of IE Bulletin 79-02 and the ASME Boiler and Pressure Vessel Code,Section III, will be included in the design verification efforts for Seismic Category I supports. Such effarts will be completed prior to placing plant systems into operation.

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TABLE 1 RESULTS OF BASE PLATE ANCHOR REANALYSIS ANCHOR FACTOR OF MARK NO. SIZE O SAFETY 1E12-H356 3/4" 0 5.82 lE12-H382 3/4" 0 10.4 1E12-H561 3/4" 0 11.00 1E12-H568 3/4" 0 7.9 1E51-H048 3/4" 0 8.6 1G41-H251 3/4" 6 23.0 1P45-H358 1/2" 0 3.5*

1P45-H569 3/4" 0 20.0 1P47-H131 1/2" 0 106.0 1P47-H141 1/2" 0 17.7

• To be reanalyzed and/or redesigned to increase factor of safety to 4.0.

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ATTACICEIIT 2 July 6, 1979

4. The current ctatus of the installation of safety-related pipe support bar.e plate anchor bolts is that only twelve have been installed and none have received final torque. The twelve installed bolts have been visually inspected to verify that Oley have been correctly installed and are the specified design size and type.

The Perry I;uclear Power Plant QC program requires 100% first line inspection of all safety-related pipe support base plate anchor bolts. This program will verify that:

a. The bolt preload is equal to or greater than the bolt design load (note: shell type bolts are not used).

b. The bolts have been installed correctly and are of the specified design size and type.

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