ML19257D390

Responds to IE Bulletin 79-02,Revision 2, Pipe Support Base Plate Designs Using Concrete Expansion Anchor Bolts. All Expansion Anchor Bolts Conform to Acceptable Safety Factors

ML19257D390
Person / Time
Site:	Limerick
Issue date:	01/07/1980
From:	Boyer V PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
IEB-79-02, IEB-79-2, NUDOCS 8002040271
Download: ML19257D390 (5)

Text

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PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET PHILA DELF HI A. PA.19101 g

(215) cal-4 500 VICE-PRESIDENT ,

g g; a .,b Mr. Boyce H. Grier, Director, Region I E United States Nuclear Regulatory Commission 631 Park Avenue King of Prussia, Pa. 19h06

Subject:

NRC Region I Letter dated November 8,1979 RE: IE Bulletin No. 79-02 Revision No. 2 Limerick Generating Station - Units 1 and 2 Docket Nos. $0-352 and 50-333 File: GOVT 1-1(IEBulletin79-02)

Dear Mr. Grier:

Philadelphia Electric Company has reviewed IE Bulletin No. 79-02, Revision 2, submitted with the subject letter received on November 8, 1979 Our responses to the action to be taken by construction pemit holders are listed below:

2. Verify that the concrete expansion anchor bolts have the following mini::ra factor of safety between the bolt design load and the bolt ultimate capacity detemined 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. Fcur - 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 mini n factor of safety of four for wedge type anchor bolts and five for shell type anchors cannot be shown then justification must be provided. The Bulletin factors of safety were intended for the m!u: mum support load including the SSE. The NRC has not yet been provided adequate justification that lower factors of safety are acceptable on a long-tem basis. Lower factors of safety are allowed on an interim basis by the provisions of Supplement No. 1 to IE Bulletin No. 79-02. The use of reduced factors of safety in the factored load approach of ACI 349-76 has not yet been accepted by the NRC.

1863 195 Q soo2ou 2 91

Mr. Boyce H. Grier, Director, Region I Page 2 Resuonse In our response of July 6, 1979, it was stated that under extreme environmental loads factors of safety of three or two are considered acceptable. Any such cases have since been revised to factors of safety of four or five. All expansion anchor bolts now confom to factors of safety of four for wedge and sleeve type bolts and five for shell type bolta.

14 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 selectandtestoneanchorboltineachbaseplate(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 perfo m its intended function.

The preferred test method to demonstrate the 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 tor's.e 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 qualification tests.

Bolt test values of one-fourth (wedge type) or one-fifth (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.

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Mr. Boyce H. Grier, Director, Region I Page 3 The purpose of Bulletin No. 79-02 and this revision is to assure the operability of each seismic Category I piping system. In all cases an evaluation to ceafim system operability must be perfomed. If a base plate or anchor bolt failure rate is identified at one unit of a multi. unit site which threatens operability of safety related piping systems of that unit, continued operation of the remaining units at that ef.te must be i= mediately evaluated and reported to the NRC. The evaluation must consider the generic applicability of the identified ' S ures.

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

Thoes options may be selected on a system by system basia.

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. Those licensees that have not verified anchor bolt preload are not required to go back and establish preload. However, additional infomation should be submitted which demonstrates the effects of preload on the anchor bolt ultimate capacity under dynanic load.ag. If it can be established that a tension load on any of the bolts dees 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 perfomed to at least the original cr' culated 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 completion 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 testing purposes it must be verified that leveling nuts were not used. If leveling nuts were used, then they must be backed off auch that they are not in contact with the base plate before applying tension or torque testing.

Bulletin No. 79-02 requires verification by inspection that bolts are properly installed and are of the specified size and type.

Parameters which should be included are embedment depth, neead en63 dement, 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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Mr. Boyce H. Grier, Director, Region I Page h If piping systems 2 1/2-inch in diameter or less were computer analyzed, then they must be treated the same as the larger piping.

If a chart analysis =ethod 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 inspection.

The parameters inspected should include those descrit ed in the preceding paragraph. If small diameter piping is not inspected, then justification of system operability must be provided.

Restonse Preloading of anchor bolts is not required as stated and explained in our reply of July 6, 1979 5 Detemine the extent that expansion anchor bolts were used in concreteblock(masonry)vallstoattachpipingsupportsin Seismic Category 1 systems (or safety related syctems as defined by Revision 1 of IE Bulletin No. 79-02). If expansion anchor bolts were used in concrete block walls:

a. Provide a list of the sys' ems involved, with the number of supports, type of anchor bolt, line size, and whether these supports are accessible during nomal plant operation.

b. Describe in detail any design consideration used to account for this type of installation.

c. Provide a detailed evaluation of the capability of the supports, including the anchor bolts, and block wall to meet the design loads. The evaluation must describe how the allow-able loads on anchor bolts in concrete block walls were detemined and also what analytical method was used to detemine the integrity of the blocs walls under the imposed loads. Also describe the acceptance criteria, including the numerical values, used to perfom this evaluation. Review the deficiencies identified in the Infomation Notice on the pipe supports and walls at Trojan to detemine 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 plana and schedule for any further action.

Resoonse No Seismic Category I large pipe is or will be supported from concrete block walls with expansion bolts.

Small pipe may be attached to concrete block walls with expansion bolts under the design criteria stated in para 6raphs 5b. and 5c.

a. A list of systems, number of supports, etc. cannot be furnished because all piping systems designs ha've not been completed, g

Mr. Boyce H. Grier, Director, Region I Page 5

b. & c. The design criteria pemits the use of Phillips sleeve type anchors only in concrete block walls.

The capability of these expansion anchors in block walls was based on a test program perfomed at the Limerick job site. The allowable design load is based on a factor of safety of five to the lowest value of failure load in shear or tension as detemined by the test program.

In all cases a minimum of 6 samples per size was used.

The Anal 3 -tical Method used for block wall design is the working stress method of the Unifom Building Code-1970.

Additional design details are as follows:

. Walls are designed for seismic inertia loads nomal to wall.

. OBE allowable stress increase - 1.25

. SSE allowable stress increase - 1.33

. Seismic loads are computed as per enveloping floor response stectra for 6% damping

. Natural frequencies are computed using uncracked section.

. Relative floor deflections were considered.

. Typical design height is 15' .

. Typical design thickness is 18".

. Majority of the walls are non-shear, non-bearing walls. Shear walls are for one story structure within the building.

. Loads imposed by Category I small pipe were not included in the block wall design. However, if small pipes are to be supported from block walls, those walls will be evaluated to detemine their capability.

. In plane and out of plane loads were not considered concurrently.

d. Phillips sleeve type expansion anchor bolts in concrete block walls were p of-tested after installation and will be tested in future installations to twice the allowable design loads. The testing frequency is one in five bolts with a minimum of one test for ecch plate or structural support.

6. Detemine the extent that pipe supports with expansion anchor bolts used structural steel shapes instead of base plates.

The systems 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 perfomed for the Bulletin. If these supports cannot be verified to have been included in the Bulletin actions:h} }h9

Mr. Boyce H. Grier, Director, Region I Pa6e 6

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 nomal plant operation.

b. Provide a detailed evaluation of the adequacy of the anchor bolt desi6 n 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.

Response All pipe supports whether they consisted of plates or structurals fastened by expansion bolts were included in the original analysis. Sincerely, Copy to: U. S. Nuclear Regulatory Cccmission Office of Inspection and Enforcement Division of Reactor Operations Inspection Washington, D. C. 20553 1863 200}}