ML19256G277

Forwards 30-day Response to IE Bulletin 79-02,Revision 2, Pipe Support Base Plate Designs Using Concrete Expansion Anchor Bolts. Pipe Support Design Calculations & Drawings Reviewed.Completion of Work Scheduled for 800401 & 0701

ML19256G277
Person / Time
Site:	Davis Besse
Issue date:	12/10/1979
From:	Crouse R TOLEDO EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
IEB-79-02, IEB-79-2, NUDOCS 7912280643
Download: ML19256G277 (9)

Text

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bb TOLEDO EDISON Docket No. 50-346 License No. NPF-3 Serial No. 1-108 December 7, 1979 Mr. James G. Keppler Regional Director, Region III Office of Inspection and Enforcement United States Nuclear Regulatory Co mineinn 799 Roosevelt Road Glen Ellyn, Illinois 60137

Dear Mr. Reppler:

IE Bulletin No. 79-02, Revision No. 2, dated November 8, 1979, requested that we provide additional information concerning our inspection of pipe support base plate designs using concrete expansion anchor bolts within 30 days of the issuance of the Revision. Attached is our response to IE Bulletin No. 79-02, Revision No. 2 for the Davis-Besse Nuclear Power Station Unit 1.

Yours very truly, ff n=1' R. P. Crousa Vice President Nuclear RPC:CLM db b/8 cc:

United States Nuclear Regulatory Commission Office of Inspection and Enforcement Division of Reactor Operations Inspection Washington, D.C. 20555 DEC 101973 1650 278 THE TOLEDO EOISON COMPANY EDISON PLAZA 300 MAOISON AVENUE TOLEDO, OHIO 43652 7912280 L

Docket No.59-346 License No. NPF-3 Serial No. 1-108 December 7, 1979 A REPORT ON PIPE SUPPORT BASE PLATE DESIGNS USING CONCRETE EXPANSION ANCHOR BOLTS Response to NRC IE Bulletin 79-02, Revision 2 Davis-Besse Nuclear Power Station Unit 1 All licensees for nuclear power plants were required to evaluate additional design practices and installation procedures used for concrete expansion anchors and pipe support base plates in accordance with NRC IE Bulletin 79-02, Revision 2, dated November 8, 1979. In compliance with the requirements of

hat revision, those pipe supports which were defined and evaluated in the original response, (Serial No. 1-78) dated July 6, 1979, were reexamined by means of the following programs:

(a) An inspection of all concrete block (masonry) walls was made to determine the extent to which piping systems were supported from these walls using concrete expansion anchors.

(b) A review of the design calculations for any pipe support identified under (a) above to ensure compliance with the factor of safety requirenents set forth in the Bulletin.

(c) A review of the design calculations for any pipe support previously accepted with a factor of safety of 3 for faulted conditions to ensure compliance with the factor of safety requirements set furth in the Bulletin.

(d) A review of the pipe support design drawings to ensure that structural shapes, attached with concrete expansion anchors, were included in the scope of the original response to the Bulletin.

This report is to be considered in conjunction with :he original response.

Response to action items 2 and 4, and the conclusion section supersede the previous submittal. In addition, response to Revision 2 items of the Bulletin are included in this report. The revised portions are indicated by revision bars in the right hand margin. All terms, names, and organizations and references previously defined remain unchanged.

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II. Conclusions (in previous response - July 6, 1979)

As of the date of this report the engineering evaluation and flexibility analysis for IE Bulletin 79-02 has not been completed. This effort is being carried out concurrently with that required for IE Bulletin 79-14 because the information obtained during the IE Bulletin 79-14 valkdown inspection could affect the anchor bolt loads used.

During the early construction phase of Davis-Besce Unit 1, the inherent difficulties associated with concrete expansion anchors were recognized and efforts were taken to improve construction techniques and to ensure and document proper installation.

Therefore, the defective bolts encountered during the inspection /

testing program were ninimal.

Based upon the results of the inspection / testing program implemented on the statistical sample of concrete anchor bolts, it can be concluded that, there exists a greater than 95% confidence level of there having been installed not more than 5% defective anchor bolts.

III. Response to Action Items (in previous response - July 6, 1979)

2. " Verify that the concrete expansion anchor bolts have the following minimum factorc of safety between the bolt design load and the bolt ultimate capacity determined from static load tests (i.e. 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"

Response

Based on the various manuf acturer's recommendations for both wedge and shell type expansion anchors, a factor of safety of four was used in the initial design of pipe supports and anchor bolts.

In the current design review the existing pipe support installations are beirg evaluated for the following factors of safety:

a. four - Wedge-type anchor bolts

b. five - Shell-type anchor bolts These values apply to both Service Load Conditions (i.e., thermal loads, deadweight loads, and Operating Basis Earthquake loads) and Faulted Load Conditions (i.e.,

loads caused by accident conditions (LOCA), Safe Shutdown Earthquake loads, extreme environmental loads, or loads encountered only during testing).

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Factor of safety is the ratio between bolt ultimate capacity, as stated by the manufacturer, and design load. At this time, calculation of design loads for all of the 10,499 anchor bolts is in progress with final factors of safety pending outcome of the piping system stress analyses necessitated by IE Bulletin 79-14.

Schedule for completion of this work effort is addressed under action item 7.

4. " Verify from existing Q. C. documentation that design requirements have been met for each anchor bolt in the following areas:

a. Cyclic loads have been considered (e.g. anchor bolts preload is equal to or greater than bolt design load). In the case of the shell type, assure that is 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 subitems (a) and (b) above. If the test fails all other bolts on the 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".

Respense

Background

During the construction period of 1972 to 1973 at Davis-Besse Unit 1 it was noted that inconsistent results were obtained while installing the wedge-type expansion anchors. A testing program was therefore initiated to develop proper installation techniques and correlat between torque values and bolt preload for the concrete type and strength used. Upon completion of this testing program the installation methods were revised to include lubrication of threads, new torque values, use of multiple washers, etc. Thisinformationwasisguedasanattachmenttothe piping and pipe support installation specification and necessitated The re-installation con-of all wedge-type expansion anchors installed prior to October 1974.

tractors were required to expand the scope of their Quality Control surveillance of anchor bolt installations to include torque verification, bolt size and length verification and proper washer orientation (where applicable). Bechtel Power Corporation Quality Contral also included these items in their surveillance programs to ensure t. hat the contractors were properly monitoring their installations.

In April 1977 an inspection progrsm was conducted by NRC Region III inspectors to verify the installed lengths of several pre-selected concrete anchors. Sevecteen pipe supports were checked by ultrasonic e tamination (a total of 93 anchor bolts); all of which satisfactorily met design length requirements.

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In response to Bulletin 79-02, all of the available Quality control documentation was obtained for the systems listed in Attachment 1. These records consisted of field inspection reports, installation acceptance checklists and torque certificates (available for approximately 60% of the wedge-type anchors).

This documentation established sufficient confidence that the contractors adhered to the installation / verification program requirements. After evaluating the available documentation, it was decided that the operability of ecch system could be assured by proving the validity of the original field program through a statistical sampling plan of randomly selected anchor bolts.

Statistical Sampling Plan Initially, an attribute sampling plan of hypothesis testing was selected based upon the hypergeometric distribution. This plan would develop a 95% confi that no more than 2% defective anchor bolts exist in the total population.gence Af ter initiation of the field inspection program, it was decided that although the hypothesis testing approach is common in nuclear materials quality control, it did not lend itself readily to the evaluation of installed anchor bolts (i.e., established values were not available for the probability of rejecting an acceptable bolt (p), the acceptance quality level (AQL) or the rejection quality level (RQL), all of which would be required to properly evaluate the statistical inference of the test results). The method of parameter estimation was therefore substituted i'or hypothesis testing and subsequently has been found consistent with the sampling plan proposed in Revision 1 of Bulletin 79-02.

By this method an upper confidence limit on the number of defects (D) in the total population (N) is constructed, based upon the hypergeometric distribution:

D h (x;n, D, N) = (x)1 (N-D)

\n-x/ for x = 0,1,2...,x,

("J (written in binomial coefficient notation) where: x, = number of obi,erved defects in the sample n = sample size (1-0() 100 = confidence level The acceptance criteria is a 95% confgdence leval that there are 5% or fewer defective anchor bolts in the total population.

The tots.1 population of concrete expansion anchor bolts to be investigated was defined as all expansion anchor bolts located on pipe supports for Q-listed piping systems which are 2 1/2" and larger. It was not considered necessary to include those piping systemc which are 2" and smaller since most of the supports are located and designed in accordance with the conservative chart analysis method; magnitude of the stress values is generally quite low for the minimum standard size components; and the installation / verification programs were the same as those 1650 282

in effect for 2 1/2" and and larger systems. The sample size was selected as 4% of the population while the actual number tested was approximately 4.5%. Randomness of the sample was guaranteed through preselection of each pipe support and anchor bolt with no prior knowledge of location, accessibility, installation contractor or other weighting factor that might invalidate the l test. The sample was evenly distributed among the 57 system isometric drawings which reflect the piping systems investigated, with no more than one anchor bolt to be tested per base plate.

Inspection / Testing Program The inspection / testing program6 included the following series of dimensional and pullout checks on each subject anchor bolt to determine its ability to function as designed:

a. Torque-tension check -- each anchor bolt was loaded to a value equal to the maximum design preload for that size and then checked for movement to determine its pullout capacity Base plates were shimmed and leveling nuts removed as necessary, to ensure accurate loading of shell-type inserts.

The acceptance criteria for bolt displacement when developing preload was two or less full revolutions of the nut (vedge-type); 1/16" or less insert movement (shell-type),

b. Embedment length check -- each wedge-type anchor bolt was nondestructively examined by Ultrasonic Testing to determine its overall length from which the embedment length was calculated. These lengths were then compared to the design drawing or the manufacturer's recommended value,

c. Thread engagement check -- each bolt was dimensionally chicked for necessary thread engagement to develop full capacity of the bolt,

d. Shoulder to cone check -- for each shell-type anchor bolt the dimensions taken in b. above were interpreted to determine if the cone was fully inserted.

e. Anchor bolt check -- the diameter, type, manufacturer, and overall length of each anchor bolt was identified and checked for compliance with the design drawing.

Although each anchor bolt tested was left in a preloaded condition, the torque-tension check was not intended to prove the as-found preload equal to, or greater than, the design load for the following reasons: (1) Pipe supports are subject to both static and short duration cyclic loads caused by a seismic event. This type of loading does not induce fatigue and the amount of bolt preload present will not greatly affect the performance of the anchorage.

(2) If the initial torqua on the bolt accomplishes setting of the wedge, the ultimate capacity of the bolt is not affected by the amount of preload present in the bolt at the time of cyclic loading. (3) For vibratory loads during plant operation, expansion anchors have been shown to successfully withstand a long term fatigue environment discussed in action item 3. (4) Scit preload is gradually lost over the life of the plant through creep and other similar phenomena.

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k documented on All nonconformances that were noted during the above five h lchec Powers were Toledo Edison Nonconformance Reports (NCR's)t the andfactors forwarded to Bec Corporation for resolution.

nonconforring condition and those anchor bolts which wouldd not " failures".

mee These of safety stated in the response to action item 2 were considere 2 or items were either corrected immediately if the factor of safety fwas safety less, or will be Thecorrected at the of distribution next refueling these outage

" failures" wasfor factors such that othe operability greater than 2. In addition, an anchor bolt " failure" of no one system would have been impaired. designed and ld fail only conetitates the inability of an anchor bolt to function as or that the piping system would not operate.

system identifica-All the original documentation for the testing program including: test results, date of tion, location, method of test, type of anchor bolt,lity Control Inspector are test, and signatures of reviewing engineer and Qua maintained by Toledo Edison.

Sampling Plan Results Totals:

10499 Population (N) 469 Sample size (n) 15 Defective bolts (x)

Statistical Inference:

C(=0.016044 + 0.00987 + 0.00565 + 0.00299 + 0.00145

+ 0.00064 + 0.00026 = .0369 (1-00 100= 96.31 There is a 96.3% confidence in finding 5% or fewer defects

Conclusion:

block 5.

" Determine the extent that expansion anchor bolts were used in (orconcrete safety (masonry) walls to attach piping supports in Seismic 02). If expansion Category I systems related systems as defined by Revision 1 of IE Bulletin No. 79-anchor bolts were used in concrete block walls:

a.

Provide a list of the systems involved, with the number ible of supports, type of anchor bolt, line size, and whether these supports are access during normal plant operation.

his type b.

Describe in detail any design consideration used to account for t of installation. l ding c.

Provide a detailed evaluation of the capability dof the The supports, evaluation inc u the anchor bolts, and block wall to meet the design loa s. t must describe block walls werehow the allowable determined and alsoloads what on anchormethod analytical bolts in was con us determine the integrity of the block walls under the imposed loads. I

)

Also describe the acceptance criteria, including the numerical values, used to perform this evaluation. Review the deficiencies identified in the Information Notice on the pipe supports and walls at Trojan to determine if a similar situation exists at your facility with regard to supports using anchor bolts in concrete block walls.

d. Describe the results of testing of anchor bolts in concrete block walls and your plans and schedule for any action."

Response

In November 1979, a walkdown inspection was made of all concrete block walls located in Seismic Category 1 structures to determine the extent to which pipe supports are attached to these walls. The results of this effort revealed only a portion of one support within the scope of this Bulletin revision.

This support, number 36-HBC-27-H45, is located in an accessible area of the Auxiliary Building on the six inch component cooling water return line from the Emergency Diesel Generator. Attachment to the block wall is for a lateral restraint and uses shell-type expansion anchors. The design of the block wall to which this support is attached was checked for its capacity to carry the loads imposed upon it by the support and was found acceptable.

Due to the lack of documented pullout capacities for expansion anchors in concrete block walls, this support was reviewed for structural adequacy without considering the portion attached to the block wall. The results of this analysis confirmed the design capable of carrying the imposed loads while meeting the acceptance criteria for member stresses, pipe centerline deflection, and pullout capacity of the anchor bolts not attached to the blockwall.

6. " Determine the extent that the pipe supports with expansion anchor bolts used structural steel shapes instead of base plates. The system and lines reviewed must be consistent with the criteria of IE Bulletin No. 79-02, Revision 1. If expansion anchor bolts were used as described above, verify that the anchor bolt and structural steel shapes in these supports were included in the actions performed for the Bulletin. If these supports cannot be verified to have been included in the Bulletin actions:

a. Provide a list of the systems involved, with the number of supports, type of anchor bolt, line size, and whether the supports are accessible during normal plant operation.

b. Provide a detailed evaluation of the adequacy of the anchor bolt design and installation. The evaluation should address the assumed distribution of loads on the anchor bolts. The evaluation can be based on the results of previous anchor bolt testing and/or analysis which substantiates operability of the affected system.

c. Describe your plans and schedule for any further action necessary to assure the affected systems meet Technical Specifications operability requirements in the event of an SSE."

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Response

While initially reviewing all Seismic Category I pipe supports in an effort to determine the exact number of anchor bolts within the original scope of the Bulletin, all supports with concrete expansion anchors were included, regardless of base plate type or shape. Therefore, structural steel shapes were considered within the sample population for the field inspection / testing program and are presently being reviewed as part of the base plate flexibility analysis program.

7. "For those licensees that have had no extended outages to perform the testing of the inaccessible anchor bolts, the testing of anchor bolts in accessible areas is expected to be completed by November 15, 1979. The testing of the inaccessible anchor bolts should be completed by the next extended outage.

For those licensees that have completed the anchor bolt testing in inaccessible areas, the testing in accessible areas should continue as rapidly as possible, but no longer than March 1, 1980. The analysis for the Bulletin items covering base plate flexibility and factors of safety should be completed by November 15, 1979. Provide a schedule that details the completion dates for IE Bulletin No. 79-02, Revision 2, items 1, 2 and 4".

Response

On November 21, 1979 a meeting was held in Bethesda, Maryland, with the NRC staff to discuss several questions that had been raised during site audits of our IE Bulletin 79-02 inspection / testing program and the methodology used in our base plate flexibility analysis. At this meeting, general agreement was reached on the acceptability of the approach, as described in our July 6, 1979 submittal, to be taken for analyzing base plate flexibility.

As stated in our report, dated July 6,1979, all responses have been completed except for items 1 and 2. The work effort for these items is currently being pursued but is being impacted by the system stress reanalyses necessitated by IE Bulletin 79-14. Wherever possible those systems having a direct bearing on IE Bulletin 79-02 are being examined first but, due to the extent of this work and limited numbers of stress analysts in the industry, completion is currently scheduled for April 1, 1980 for the supports and anchors in accessible areas and July 1, 1980 for the supports and anchors in the inaccessible areas.

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