ML20062B961

Forwards 780628 Memo to R Mattson Re Info on Failures of safety-related Pipe Supports at Millstone 1 & Design Deficiencies on Similar Equipment at Shoreham.Aslb Notified of Pipe Support Base Plate Design

ML20062B961
Person / Time
Site:	Millstone, Shoreham, Trojan
Issue date:	09/28/1978
From:	Stello V Office of Nuclear Reactor Regulation
To:	Grossman M NRC OFFICE OF THE EXECUTIVE LEGAL DIRECTOR (OELD)
Shared Package
ML18004B972	List: ML18004B971 ML20062B959 ML20062B961
References
TASK-AS, TASK-BN-78-21 BN--78-21, TAC-07551, TAC-7551, NUDOCS 7811020332
Download: ML20062B961 (2)

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MEMORANDUM FOR: Milton ~J. Grossman, Hearing Division Director'and Chief Counsel, OELD

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FROM:

Victor Stello, Jr., Director

! l Division of Operati,ng Reactors, NRR 3

SUBJECT:

BOARD. NOTIFICATION - PIPE SUPPORT BASE PLATE DESIGN j

The attached memorandum to R.oger Mattson', dated June 28, 1978, j

presents information concerning failures of safety-related pipe f

supports at Millstone 1 and design deficiencies on similar equip-

-l ment at Shor'eham Unit 1.

As indicated in the attachment, two 1

factors appeared to contribute to failure of anchor-bolt connec-tions of pipe supports. These are, 1) the design assumption j

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that base plates perform structurally as rigid load-bearing

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members when they may be flexible members, and 2) incorrect anchor bolt torqui.ng.

Recent audits of Architectural Engineering firms and assessments of the actions taken at Millstone, as noted.in the attachment, provided the following, general information:

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During the'last few years, the'A/Es have changed their design and installation procedures for' concrete embedded pipe supports.

2.

Past and current des.ign and installation procedures vary amo.ng the A/Es.

3 In the past many of the pipe support designs have been con-tiacted, and were done with methods not known by the principal A/Es.

We have concluded that the'more detailed information required must be obtained from each operati,ng facility. We are prepari,ng a generic

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i MEMORANDUM FOR: Milton J. Grossman, Hearing Division Director and Chief Counsel, OELD FROM:

Victor Stello, Jr., Director Division of Operati.ng Reactors, llRR

SUBJECT:

BOARD NOTIFICATION - PIPE SUPPORT BASE PLATE DESIGN The attached memorandum to Roger Mattson' dated June 28, 1978, presents information concerning failtres of safety-related pipe supports at Millstone 1 ar.d design deficiencies on similar equip-ment at Shor'eham Unit 1.

As indicated in the attachment, two factors appeared to contribute to failure of anchor-bolt connec-tions of pipe supports.

Theseare,1) the design assumption that base plates perform structurally as rigid load-bearing members when they may be flexible memb.rs, and 2) incorrect anchor bolt torquing.

Recent audits of Architectural Engineering firms and assessments of the actions taken at Millstone, as noted in the attachment, provided the following, general information:

.l.

During the last few years, the' A/Es have changed their design and installation procedures for concrete embedded pipe sup' ports.

2.

Past and current des.ign and installation' procedures vary amo.ng the A/Es.

.3 In the past many of the pipe support designs have been con-tracted, and were done with methods not known by the principal A/Es.

We have concluded that the'more detailed information required must be obtained'from each operati,ng facility. We are preparing a generic

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Mi,1 ton J. Grossman 2-letter to each operating facility requesting detailed design, installation, and testing information of concrete-embedded anchor-bolted pipe supports of safety-related equipment.

We recommend that this information be provided to the following Boards:

1.

Monticello (FTL) 2.

Indian Point 1,2,3 (Seismic Des.ign)

He will provide a...sssessment of this issue upon completion of our ; valuations.

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Victor Stello, Jr., Director i

Division of Operating Reactors Office of Nuclear Reactor Regulation

Enclosure:

June 28, 1978 memo, Stello to Mattson cc w/ enclosure:

O. Vassallo

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V. Stello

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R. Mattson R. Bevan L. 01shan L. Nichols V. Noonan A. Schwencer T. Ippolito J. Fair 9

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55 JUN 2 g hyg $oooo*p o MEl10RAfl0VM FOR: N.J.Mattson, Director ~ Division of Systems Safety FROM: Victor Stello, Jr., Director Division of Operating Reactors

SUBJECT:

OPERATIflG EXPERIEllCE MEMORAflDUM NO. 13 PIPE SUPPORT BASE PLATE PROBLEM 3 PROBLEM Recently during inservice inspections at Millstone Unit 1, structural ) failures of rigid pipe supports for class 2 safety equipment were observed. These inspections, recently implemented at Millstone, e were conducted ih accordance with Section XI of the ASME Code, ~ as endorsed by regulation, 10 CFR 50.55 a(g), in February 1976. / Several base-plate anchor bolts of pipe supports in the Core Spray and the Lo.i Pressure Coolant Injection Systems at Millstone were not properly embedded; and, in some cases the anchor bolts were completely pulled out and no supporting furction was provided. 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 with drilled anchor bolts using rigid plate assumptions has resulted in underestimation of loads on some anchor bolts. Inspection of anchor bolt installations at Shoreham has shown over fifty percent of the bolt installations were deficient. Supports for both piping systems and electrical raceways have been reported as deficient at Shoreham. PRESUMED CAUSE It is currently believed that two interacting factors contribute to the failure of the supports. First, the design assumption that the base plates perform structurally as rigid instead of flexible members may provide low estimates of imposed loads on the supports. Secondly, incorrect anchor bolt embadment may also contribute l to insufficient support. The attached memorandum from V. Noonan to B. Grimes, dated June 2,1978, provides additional infonnation. 78U 02 03 % m,.m.., g,,.,,u.w.,n m.,., ,7. g.,,, n.. m.. g. w.,..,. w. ~ 'I

SAFET.Y. sigil!FI'CA CE f i Depending on equipment layout, improperly designed or installed anchor supports could: ~ 1. result in loss of support function in some cases; and, 2. result in high stressing of piping systems during a seismic event or during a significant flow transient. ~ ' ~ REPAIR ) Millstone with assistance from Teledyne Engineering has completed design modifications and repairs. These changes include increased base plate thickness and larger anchor bol,ts for failed supports. Shoreham in conjunction with Stone and Webster is evaluating both piping and electrical type supports. The review is-scheduled to be completed by December, '978 DDR ACTI0ft ( The Engineering Branch will review the design procedures used on operating plants to determine anchor bolt loads, the techniques used to determine load ratings for anchor bolts, and the installatio' procedures. This review will be done through an A/E vendor inspection audit in conjunction with IE. These A/E audits will be started during early July, 1978 We anticipate that criteria will be developed for design and installation of base plate-anchor bolt assemblies, and those operating plants requiring corrective action will be identified. Additionally EB staff will further assess'the occurrence and corre'ctive actions taken.at Millstone. " ~ P.ECOPF.E!!DAT10f1S We recommend that this problem be addressed on all CP and OL reviews. At this time it. appears that considerations should be given to the analytical methods used to. determine whether or not base plates behave as flexible or rigid members. This in turn may effect the anchor bolt size and embedment to properly cope with loads imposed on the supports. e 9" " * *N '. W.'. ,3~' ,% ~ 1 '.. 5 i, t. w, r; ,,,,.n,, f,,,), ;if, D ',,* ', 1 f ** ,.; e av e

-a -~ It may be appropriate to require that applicants provide for review their: . 1. methods for determining base pla'te thickness and 'anchir bolt leads; 2. criteria for anchor bolt installation; and, criteris for load rating techniques for anchor bolts, including 3 ~1 '; clic, loads. We shall coordinate our meetings, discussions and evaluations of this issue with your staff. Supplemental information will be provided. . : T., , g..,, s- ,:./.c.

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?n Vic' tor Stello, Jr., Director ~ gi Division of Operating Reactors PRINCIPAL DDR PERSONNEL. ~ ' deviewer: J. Fair ~

Enclosure:

Memorandum dated 6/2/78 cc: w/ enclosure E. G. Case S. Hanauer R. S. Boyd H. R. Denton .. F. Schroeder DSS AD's DDR AD's DDR BC's n0R SL's . Fair W. Nichols W. Rutherford ~ J. Sniezek

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