ML20040F258
| ML20040F258 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 02/05/1982 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Crane P PACIFIC GAS & ELECTRIC CO. |
| References | |
| IEB-79-02, IEB-79-2, NUDOCS 8202090016 | |
| Download: ML20040F258 (5) | |
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i FEB 5 1982.
Docket Nos. 50-275 50-323 e
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P. O. Box 7442 3
9 San Francisco, California 94120
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g Attention: Mr. Philip A. Crane, Jr.
Assistant General Counsel
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Gentlemen:
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Subject:
COMMENTS ON PG&E RESPONSE TO IE BULLETIN 79-02, " PIPE SUPPORT BASE PLATE DESIGN USING CONCRETE EXPANSION ANCHOR BOLTS" Ref:
(a)
IE Bulletin 79-02, " Pipe Support Base Plate Design Using Concrete Expansion Anchor Bolts" of March 8,1979 (b) PG&E letter of December 3,1980, Re: NRC IE Bulletin 79-02, Rev. 2 (c) NRC letter of November 28, 1979, Re: Coctaents on PG&E Response to IE Bulletin 79-02 (d) NRC letter of October 9,1980, Re: HRC Inspection at Diablo Canyon (e) PG&E letter of July 20, 1979, Re:
Diablo Canyon Units 1 and 2 (f) PG&E letter of September 19, 1979, Re:
Diablo Canyon Units 1 and 2 The subject bulletin, reference (a), requested PG&E to perform certain actions to verify accurate design loads and adequate installation of concrete expansion bolts used in seismic Category I pipe supports and to report the results of those actions to the NRC.
Subsequently, Revision 1, Supplement 1, and Revision 2 were issued which provided some details, clarifications, and in the case of Revision 2, new requirements. Refer-ence (b) is the current PG&E response to IE Bulletin 79-02.
Reference (b) also responds to references (c) and (d) which were NRC coments to references (e) and (f), PG&E's initial responses to the bulletin.
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NRC FORM 3181101803 NRCM O240 OFFICIAL RECORD COPY
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. FEB 5 1982
.Your referenced responses to IE Bulletin 79-02 have been reviewed by the NRC Region V staff.. However, before we can complete our evaluation of the actions you have taken in response in the requests contained with IE Bulletin 79-02, it will be necessary for you to provide us with the additional information identified in Attachment I of this letter.
To enable NRC Region V to complete a timely review of your IE Bulletin 79-02 actions, please submit to me the infonnation identified in Attachment I prior to March 12, 1982.
eng.nai cA M 1, t. C(cas f fM R. H. Engelken Regional Administrator-
Attachment:
,As Stated bcc:
DMB/ Document Control Desk (RIDS)
Distributed by RV:
Engelken Resident Inspector (4)
State of CA (Hahn/ Johnson)
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NRC RV Review of PGAE Responses to IE Bulletin 79-02 The specific requirements of IE Bulletin 79-02 and the corresponding PG&E responses are summarized below. Additional information required by NRC Region V to continue its review of PG&E actions taken is identified.
l 1.
Bulletin paragraph 1:
Verify pipe support base plate flexibility was accounted for in the calculation of anchor bolt loads. A description of the analytical model used is to be submitted.
PG&E Response:
Baie plate flexibility has been taken into account in the calculation of bolt loads. Teledyne Engineering per-formed the calculations for 1376 pipe supports for Unit 1.
The analytical model used has been provided. A number of supports in Unit I required modification.
Information Required by NRC Region V:
1)
Notification of completion of modifications for Unit 1.
2)
Notification of completion of analysis and modifications for Unit 2.
2.
Bulletin paragraph 2: Verify minimum anchor bolt factors of safety have been achieved.
PG&E Response: The bulletin safety factors have been verified in the calculations of the anchor bolt loads for Uni?.1. 241 pipe supports required modifications for Unit 1 to achieve the factors of safety.
Information Required by NRC Region V:
Current status of Unit 2 modifications.
3.
Bulletin paragraph 3:
Describe the design requirements for cyclic loads.
PG&E Response: The load combinations used to calculate bolt loads are described.
Information Required by NRC Region V:
None.
4.
-Bulletin paragraph 4: -Verify from existing QC documentation or from a sampling testing program that anchor bolts 'are preloaded and are properly installed.
- PG&E Res7onse:
The preloading of shell type anchor bolts was verfTTed by a field test sample of shell type anchors.
For Hilti Kwik Bolts and other stud type anchors PG&E states that Attachment I -
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Page 1 of 3 r
' the torque values specified in the 1973 Edition of the phillips Red Head Anchoring System Catalog were applied since August of 1977.
For stud type anchor installations prior to August of 1977, acceptance of preload is based on the sampling doae on shell type anchors.
l Discussion:
The bulletin requires some specific QC documentation that anchors are torqued to, at least design load and that proper embedment is achieved after torquing..The PG&E position, in paragraph 3.F. of Attachment I to reference (b), states that Kwik bolts were installed with an " average filter installation torque" prior to August of 1977, when a torque value.was first prescribed at Diablo, and that the " average filter installation torque" for stud type anchors had been determined by testing the shell anchors of that period. The PG&E position does not address the fact that, while shell anchors do not have a tendency to pull out'of their holes, Kwik bolt or stud type anchors do have that tendency.- Experience has shown that craftsmen tend to stop torquing once a stud anchor tended to pull out of its hole. Paragraph 7 of Attachment I to reference (b),
states that starting in 1977 stud type anchors were installed per " Instruction Number 98, Revision 0 dated January 21, 1977, which mandated...embedment depth". As previously pointed out in reference (d), Instruction Number 98 of January 21, 1977 did not mandate embedment depth or torque. These requirements appeared in the July 27, 1977 revision.
In regard to proper installation of Kwik bolt (or stud type) anchors, it does not appear that sufficient verification was provided which assures that embedment depths assumed in analysis were achieved in the field installations.
In reference to shell type anchors (e.g. HD0 or Phillips Red Head Self Drilling) further clarification is required regarding thread engagement adequacy.
Reference (b), Attachment I, paragraph 4c references J. E. Shigley " Mechanical Engineering Design" 3rd Edition, Section 6-8, page 252, as the justification that only three threads of engagement are necessary to achieve full bolt strength. The discussion by Shigley is general in nature and does not address specific material or application.
The inspector's calculations for sample sizes of Phillips Red Head Anchors show that approximately five threads of engagement are required for full bolt strength, but that four threads of l
engagement will provide sufficient bolt stripping strength to provide factors of safety from three to four above the maximum allowable design loads listed in reference (b), Attachment II.
Reference (b), Attachment I, paragraph 7 states that prior to 1977, shell type anchors were "almost exclusively" used.
l Attachment I.
Page 2 of 3
. Information Required by NRC Region V:
(1) For stud type anchors - Verification, from existing QC documenta-tion or from a sampling testing program, that stud type anchors installed prior to August,1977 are preloaded to design load and are properly installed (correct embedment depth, torque, etc.).
'(2) For shell type anchors - a numerical quantification of the term "almost exclusively", and an assessment of the stripping strength factors of safety achieved at Diablo Canyon for shell type anchors.
l 5.-
Bulletin paragraph 5:
Determine the extent that expansion anchors were used in concrete block walls.
PG&E Response: No seismic Category I piping systems are mounted on concrete bicek walls using expansion anchors.
Information Required by NRC Region V:
None 6.
Bulletin paragraph 6:
Determine the extent that pipe supports with expansion anchor bolts used structural steel shapes instead of base plates and verify the steel shapes are included in the bulletin actions.
PG&E Response:
None
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Information Required by NRC Region V: 'PG&E needs to provide a response to IE Bulletin 79-02, Rev.-2, paragraph 6..
Attachment I Page 3 of 3