ML20062D375
| ML20062D375 | |
| Person / Time | |
|---|---|
| Site: | 05000484 |
| Issue date: | 11/08/1978 |
| From: | Lewis S NRC OFFICE OF THE EXECUTIVE LEGAL DIRECTOR (OELD) |
| To: | Anderson G, Kornblith L, Smith I Atomic Safety and Licensing Board Panel |
| References | |
| NUDOCS 7811220157 | |
| Download: ML20062D375 (1) | |
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UNITED STATES 34 7
NUCLEAR REGULATORY COMMISSION
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%,*Ts4 November 8, 1978 Ivan W. Smith, Esq., Chairman Dr. George C. Anderson Atomic Safety and Licensing Board Department of Oceanography U.S. Nuclear Regulatory Commission University of Washington Washington, D. C. 20555 Seattle, Washington 98195f[O W d.. l Mr. Lester Kornblith, Jr.
Qv Atomic Safety and Licensing Board N ",
j,,y U.S. Nuclear Regulatory Connission gp Washington, D. C. 20555 g 7{
In the Matter of M
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AND NORTHERN STATES POWER COMPANY (
D /' [p NORTHERN STATES POWER COMPANY (MINNESOTA)
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(Tyrone Energy Park, Unit 1) bf Docket No. STN 50-484
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Gentlemen:
Enclosed are recent memoranda discussing certain problems experienced in connection with pipe support base plate design. The Nuclear Reactor Regulation Staff has informed us that the problems discussed in Mr. Stello's memorandum dated September 28, 1978, are applicable to the Tyrone facility, and that the Division of Systems Safety is presently reviewing this aspect of piping design analysis on a case-by-case basis under SRP Section 3.9.3 - ASME Codes 1, 2 and 3 Components, Component Supports and Core Support Structures.
If the Board or any of the parties wish additional information, please advise us.
Sincerely,
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Stephen H. Lewis Counsel for NRC Staff
Enclosure:
&mo 9/28/78 Stello to Grossman (w/ancis) cc w/ enclosure:
Tyrone Service List 7811MolS7 3
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WASHWGTON, D. C. 20555 SEP 2g y MEMORANDUM FOR: Milton J. Grossman, Hearing Divi,sion Director an.d Chief Counsel, OELD FRCM:
Victor Stello, Jr,, Director Division of Operati.ng Reactors, URR
SUBJECT:
BOARD NOTIFICATION - PIPE SUPPORT BASE PLATE DESIGN The attached memorandum to Roger Mattson, dated June 23. 1978, precents information concerning failures of safety-related pipe supports at Millstone 1 and design deficiencies on sinilar equip-ment at Shoreham Unit 1.
As indicated in the attachment, two factors appeared ~ to contribute to failure of anchor-bolt connec-tions of pipe supports. Thaseare,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 folicwing 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 S
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Milton J. Grossman.
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.
IndianPoint1,2,3(SeismicDesign)
We will provide an assessment of this issue upon completion of our evaluations.
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Victor Steilo, 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. Olshan L. Nichols V. Noonan A. Schwencer T. Ippolito J. Fair
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MEMORAtiDUM FOR:
R. J. Mattson, Director Division of Systems Safety i
FROM:
Victor Stello, Jr., Director Division of Oper'ating Reactors
SUBJECT:
OPERATIfiG EXPERIE! ICE MEMORANDUM tiO. 13 PIPE SU. PORT 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 were conducted i inspections, recently implemented at Millstone, n accordance with Section XI of the ASME Code, as endorsed by regul'ation, 10 CFR E0.55 a(g), in February 1976.
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, j
Deficiency reports, in accordance with 10 CFR 50.55(e), filed by l
Long Island Lighting Company, on Shoreham Unit 1, indicate that design of base plates with drilled anchor bolts using rigid plate essumptions 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.
Suppcrts 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 embedment may also contribute to insufficient support.
The attached memcrandum frem V. Noonan to B. Grimes, dated
, June 2, 1978, provides additional information.
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2 SAFETY SIGNIFICANCE Depending on equipuent 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 ficw transient.
REPAIR Millstone with assistance frem Teledyne Engineering has ccmoleted 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.
00R ACTION The Engineering Branch will review the design procedures used en 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 corre'ctive actions taken at Millstene.
REC 0"."E3!DATIONS 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 methcds used to.. determine whether er not base plates behave as flexible er rigid members. This in turn may effect the anchor bolt size and embedment to properly ccpe with loads imposed en the supports.
-3 It_may be appropriate to require that applicants provide for review their:
1.
methods fer determining base plate thickness and anchor bolt loads; 2.
criteria for anchor bolt installation; and, 3.
criteria for load rating techniques for anchor bolts, including cyclic loads.
We shall coordinate our meetings, discussions and evaluations of this issue with your staff.
Supplemental information will be provided.
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Vic' tor Stello,'Jr., Director J
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Division of Operating Reactors PRINCIPAL DDR PEP.SONNEL t
Reviewer:
J. Fair
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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 00R AD's DOR BC's DOR SL's J. Fair W. Nichols W. Rutherford J. Sniezek e
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35 gt MEMORANDUM FOR:
B. K. Grimes, Assistant Director for Engineering and Projects, DOR D. G. Eisenhut, Assistant Director for Systems and Projects, DOR FROM:
Acitng Branch Chief, I
Engineering Branch, DDR
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 boltepull-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 assumptions 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, i&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 ano 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 shculd be addressed.
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- 3P Based on the above information, the Engineering Branel recennends that this be considered a generic item for all operati'.g plants, cnd a vendor inspection progran be impicmented with I&E to review the vendor design procedures used for analyzing support base plates utilizing drilled anchor bolts alon'g with the field ins alliation procedures utilized in installing the anchor bolts. Also, the lo'd a
rating techniques used by the anchor bolt manufacturers for cyclic loadings should be reviewed.
The Engineering Branch has talked with I&E and consider the vendor' inspection program to be the nost efficient nathod of ec=picting the necessary review.
The Engineering Branch estic:tes approximately 15 man-weeks will be required to review design procedures used by vendors and A/E fires.
The Engineering Branch will set up a meeting with both AO's to deter =ine the interface between the Engineering Branch and I&E required to implement the review.
The Engineering Eranch 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, 1978.
Risizel_Ei.941Eli
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V. S. Noonan, Acting Branch Chief Engineering Branch Divisten of Operating Reactors cc:
V. Stello, Jr., DDR W. Rutherford, IE U. Potopous, IE R. Hattson, 055 J. P. Knight, DSS R. Bosnak, DSS
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