ML20148F105

Forwards Memos Re Recent Problems in Pipe Support Base Plate design.(ANO:7811020332,7811020336, & 7811020343.)

ML20148F105
Person / Time
Site:	Monticello
Issue date:	10/24/1978
From:	Lewis S NRC OFFICE OF THE EXECUTIVE LEGAL DIRECTOR (OELD)
To:	Cole R, Jordan W, Lazo R AFFILIATION NOT ASSIGNED, NRC ATOMIC SAFETY & LICENSING APPEAL PANEL (ASLAP)
References
NUDOCS 7811070284
Download: ML20148F105 (1)

Text

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• • • ++ October 24 1978 N . PUBLIC DOCUMENT ROOM Robert M. Lazo, Esq., Chairman Dr. Walter H. Jordan Atomic Safety and Licensing Board 881 West Outer Drive Q U.S. Nuclear Regulatory Commission Oak Ridge, TN 37830 Washington, D. C. 20555 Dr. Richard F. Cole #

Atomic Safety and Licensing Board U.S. Nuclear Regulatory Commission 'b Washington, D. C. 20555 In the Matter of h4 Y .A NORTHERN STATES POWER COMPANY (Monticello Nuclear Generating Plant, Unit 1) h,[g [ ' ~

3 Docket No. 50-263

% 6 co a Gentlemen:

Enclosed'are recent memoranda discussing certain problems experienced in connection with pipe support base plate design. The Staff is in the process of obtaining additional detailed information from each operating facility concerning the characteristics of the design for each specific facility. . If the Board or any of the parties wish additional information, please advise us.

Sincerely,

'A .

Steph H. Lewis Counsel for NRC Staff

Enclosures:

As Stated cc w'/

Enclosures:

Monticello Service List y-^

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,,,. SEP 2g y MEMORANDUM FOR: Milton'J. Grossman, Hearing Division Director an.d C.hief Counsel, OELD FROM: Victor Stello, Jr. , Director Division af Operati.ng Reactors, NRR I

SUBJECT:

BOARD NOTIFICATION - PIPE SUPPORT BASE PLATE DESIGN The attached memorandum to Roger Mattson, dated June 28, 1978, presents information concerning failures of safety-related pipe supports at Millstone 1 and 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. These are,1) the design assumption that base plates perform structurally as rigid load-bearing members when they may be flexible members, 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:

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

2. Past-and current design and installation procedures vary among 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 operating facility, We are preparing a generic A-g ca,7  !)ll}$

Milton J. Grossman .

e 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 Design)

We will provide an assessment of this issue upon completion of our evaluations.

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Victor Stel'lo, Jr., Director -

Division of Operating Reactors Office of Nuclear Reactor Regulation

Enclosure:

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

D. Vassallo V. Stello -

R. Mattson R. Bevan' L. 01shan L. Nichols V. Noonan A. Schwencer T. Ippolito J. Fair -

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JUN 2 g 197g -

MEMORAfiOUM FOR: R. J. Mattson, Director .

Division of Systems Safety FROM: Victor Stello, J.r., Director Division of Operating Reactors

SUBJECT:

OPERATIfiG EXPERIENCE MEMORAf;DUM NO. 13 PIPE SUPPORT BASE PLATE PROBLEM 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, were conducted in accordance with Section XI of the ASME Code, as endorsed by regul'ation, 10 CFR 50.55 a(g), in February 1975.

Several base-plate anchor bolts of pipe supports in the Core Spray and the Low Pressure Coolant Injection Systems at Millstone were not properly embedded; and, in some cases the anchor bolts were completely pulled out and no supporting function was provided.

Deficiency reports, in accordance with 10 CFR 50.55(e), filed by Long Island Lighting Company, on Shorehan Unit 1, indicate that design of base clates with drilled anchor bolts using rigid plate assumptions has resulted in underestimation of loads on some ancher 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 leads on the supports.

Secondly, incorrect anchor bolt embedment may also contribute to insufficient support.

The attached memerandum from V. Noonan to B. Grimes, dated June 2, 1978, provides additional information.

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2 SAFETY SIGNIFICANCE Depending on equipment layout, improperly designed er installed anchor supports could: <

l. result in loss of support function in some cases; and,

2. result in high stressing of piping systens 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 bolts 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, 1978.

DDR ACTION 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 installation 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 corrective actions taken at Millstone.

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REC 0!i".EMD ATIONS , ,

We reccmmend that this problem be addressed on all CP and OL reviews.

At this time it appears that consicerations 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 ancher bolt size and embedment to properly cope with loads imposed en the supports.

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4 It may be appropriate to require that applicants provide for review their:

1.

methods for determining base plate thickness and anchor bolt loads;

2. criteria for anchor bolt installation; and, 3.

criterialoads.

cyclic for load rating techniques for anchor bolts, including We issue shall coordinate with your staff. our meetings, discussions and evaluations of this Supplemental information will be provided.

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.:/ ! - ./ '.. .y)'1 Vic' tor Stello, Jr. , Director -

1 Division of Operating Reactors PRINCIPAL DDR PERSONNEL

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Reviewer: 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 D0R BC's DDR SL's J. Fair W . Nichols .

W. Rutherford -

J. Sniczek

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HEMORANDUM FOR: B. K. Grimes, Assistant Director l

. for Engineering and Projects, DDR 'i D. G. Eisenhut, Assistant Director for Systems and Projects, DOR

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FROM: Acitng Branch Chief, .

Engineering Branch, D0R ,

SUBJECT:

PIPE SUPPORT BASE' PLATE PROBLEM The Engineering Branch, Division of Operating Reactors, has contacted Bechtel, Bergen - Paterson, Gilbert, and Stone & Webster in regard to their past and current design procedures for support base plates utilizing drilled anchor bolts. Bechtel and Stone & Webster indicated that they became aware of base plate flexibility effects

< on anchor boltcpull-out loads within the past couple of years and are now considering this in current designs. Gilbert and Bergen - Paterson indicated they are using rigid plate assuuptions for calculating bolt loads.

Review of the support redesigns at Millstone shows a considerable increase in base plate thickness and anchor bolt sizes over the previous design. The original designs by Bergen - Paterson did

.not meet the current rigidity requirements used by Stone & Webster.

Design deficiency reports by Long Island Lighting Company on Shoreham show that consideration of base plate flexibility has increased the pull-out loads on some bolts, and inspection of the supports has shown that approximately 55 percent of the anchor bolts had incorrect embedment lengths.

Currently, f&E is considering whether Stone & Webster should be investigated for a Part 21 deviation and will be further investigating this matter.

• The Engineering Branch considers the problem at Millstone where several support plates were pulled out to be a' combination of base plate flexibility and anchor bolt design problems. Since the anchor bolts were never tested for cyclic loadings, and the lines at Millston?

experienced flow induced vibrations, the capability of tne anchor bolts to withstand cyclic loadings should be addressed.

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Based on the above information, the Engineering Branel recemmends .

that this be considered a generic item for all operati'.g plants.

• and a vendor inspection program be implemented with I&E to review the vendor design procedures used for analyzing support base plates ,

utilizing drilled anchor bolts alon'g with the field instaillation procedures utilized in installing the anchor bolts. Also, the lo'ad rating techniques used by the anchor bolt manufacturers for cyclic ,

loadings should be reviewed. The Engineering Branch has talked with ILE and consider the vendor' inspection program to be the most efficient nethod of completing the necessary review. The Engineering Branch esticates approximately 15 man-weeks will be required to review. design procedures used by vendors and A/E firms. The Engineerin:: 3 ranch will set up a meeting with both AD's to determine the interfou2 between the Engineering Branch and I&E required to implement the review. -

The Engineering Branch is in the process of preparing a feedback memo to DSS on the base plate problem which is expected to be completed

'by June 9,197B'.

1 geisimp_sj.fAM.bli i V. S. Noonan, Acting Branch Chief Engineering Branch Division of Operating Reactors

-cc : Y. Stello, Jr., DOR W. Rutherford IE U. Potopeus. IE R. liattron, DSS J. P. Knight, DSS R. Bosnak, DSS .

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