ML19344A685

LER 79-106/01T-1:on 791112,design of 11 Seismic Hangers Discovered Less Conservative than Required.Caused by Design Errors in Initial Calculations of Stress Deflections.Hangers Modified Prior to Return to Operation

ML19344A685
Person / Time
Site:	Davis Besse
Issue date:	11/23/1979
From:	Batch S, Dieterich K TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19344A679	List: ML19344A678 ML19344A685
References
LER-79-106-01T-01, LER-79-106-1T-1, NUDOCS 8008210447
Download: ML19344A685 (4)

Text

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EVENT DESCRIPTION AND PROSABLE CONSEQUENCES h 1

E l While perfoming calculations for I. E. Bulletin WO2. ITT Grinnell personnel dis-I E I covered the design of 11 seismic hangers was not as conservative as was required On July 25 further 1

@E Iby the design criteria and assumptions used by ITT Grinnell.

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@ s l analysis of bace plate flexibility found that the anchor bolts for pipe supports l i

@@ l 41-HBC-36-H3, 33A-GCB-8-H1, H-17, SR-31, SR-32, and SR-39, and for the common

@ 7 Isupport structure for anchors A-55, A-61, A-79, A-80, and A-83 had a factor of I

@@ l safety of less than 2. This finding is reportable under T.S. 6.9.1.8.i. (NP-32-79-13 l

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4 lTl9 l6I7lh 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS ITITI l The ocetirrance v.rma eni, coa hy a. f on arrnee 1,y TTt r ,4 ,, ,, e t , in the infefn1 c e l e,ii n e i nn el i i l of the stresses and deflections in these hangers. The af f ace.a hangers were modified J i, i2 l prior to the unit returning to operation. The items reported July, 1980, were the re-I g ] suits of a change in the classification of rigid base plates. They will be modified .,,,j i g l prior to startup from this refueling outage and Attachment I will be updated when tha8.j s r a r work is complete.

OTHER STATUS D ht'ShhhRY OtsCOVERY DESCRIPTION

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TOLEDO EDISON COMPANY -

DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-32-79-13 DATE OF EVENT: November 12, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Design of eleven seismic supports was not as conserva-tive as required.

Conditions Prior to Occurrence: The unit was in Mode 5, with Power (MRT) = 0, and Load (Gross MWE) = 0.

4 D*;cription of Occurrence: While performing calculations for IE Bulletin 79-02, ITT Grinnell personnel discovered the design of eleven seismic hangers was not as conser-vative as was required by the design criteria used by ITT Grinnell. Four of the hangers did not meet the NRC criteria for pipe support operability. On five other supports, the slenderness ratio exceeded the design criteria of 200 used by ITT Grinnell. The remaining two supports were analyzed to have a maximum deflection of approximately .5 inches which could result in stresses on the piping in excess of the design criteria of ITT Grinnell. These analyses were performed assuming the worst case design base earthquake loading.

On July 25, 1980, while performing the base plate flexibility analysis, pipe supports 1

41-HBC-36-H3 on service water, 33A-CCB-8-H1 on decay heat, and H-17, SR-31, 3R-32, and SR-39 on main feedwater were analyzed. The results showed that the anchor bolts had a factor of safety less than two.

Also the common support structure (i.e., one support for five anchors) for anchors ,

A-55 high pressure injection, A-61 low pressure injection, A-79, A-80, and A-83 j 1

containment spray was analyzed for base plate flexibility. The results showed that  ;

the anchor bolts had a factor of safety less than two. l 1

Further information on the affected hangers is contained on Attachment 1. Since more l than one part of a redundant system was affected, this incident is being reported in l accordance with Technical Specification 6.9.1.8.1. l l

These design deficiencies were discovered while the unit was in cold shutdown during l a unit outage. , ,

I l

Designation of Apparent Cause of Occurrence: The cause of this occurrence was design errors by ITT Grinnell in the initial calculations of the stresses and deflections in these hangers. These desigt errors were discovered while calculating base plate forces and moments for the analysis required by IE Bulletin 79-02. The errors in the original design were random and not.due to a general deficiency in the original design method.

Items reported July 25, 1980, were the result of a change in the design criteria as to what constitutes a rigid base plate. The base plates for these supports were 1 originally analyzed as rigid base plates and under the new criteria are now considered flexible.

LER #79-106 ,

1 TOLEDO EDISON COMPANY DAVIS-3 ESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-32-79-13 PAGE 2 Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel. These supports are not required for normal system performance but are required only to protect the systems from a worst case condition of maximum earthquake loading.

The affected systems have been re-analyzed taking into account the non-conservative support designs. These analyses show that all affected safety systems would have performed their safety function if a design basis accident had occurred.

Corrective Action: All affected hanger modifications were completed by 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br /> on November 15, 1979, prior to the unit returning to operation. Details on the work performed, the applicable facility change request (identical to work order number), and the location of hanger is contained in Attachment 1.

The design of all Q-listed supports attached to concrete on 2h" and larger piping (over 1000 supports) have been reviewed during work performed while responding to IE Bulletin 79-02. Supports on piping smaller than 2h" were not designed by ITT Grinnell.

The following items reported July 25, 1980, will be modified by the following FCRs:

41-H3C-36-H23 by FCR 80-093 supplement 14 4

33A-GCB-8-H1 by FCR 80-088 supplement 12 1

4 1 SR-32 & SR39 by FCR 80-125 supplement 2 H-17 & SR31 by FCR 80-125 supplement 3 '

A-55, A-61, A-79, by FCR 80-089 supplement 9 j A-80, A-83 l These discrepancies will be corrected prior to startup from the current refueling I outage. Attachment I will be updated when that work is complete.  !

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Failure Data: There has been one previously reported similar occurrence, see Licensee Event Report NP-32-79-08.

I LER #79-106 1

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ATTACHMENT 1 ,

LICEWSEE EVENT REPORT NP-32-79-13 .*

- s FCR/W.O. HANGER NO. LOCATION CONTROLLING ITEM WORK PERFORED - 79-379 41-HBC44-HS Service Water Supply to Emer- SF < 2 1/4" x 5" cover bar welded to.

gency Core Cooling Room. Cooler channel 1-3 .79-380 33A-HCB2-H44 Borated Water Storage Tank SF < 2 3" x 3" x 3/8" angle iron added Supply to Emergency Core.

Cooling System 1 79-381- 34-GCBS-H17. Containment Spray Pump 1-1 Deflection n,.5** Added 2-1/2" pipe and 3/4" x .

discharge x 7" Cusset plates79-381 34-HCC38-H19 Containment Spray Pump 1-1 Deflection .5" Added 2-1/2" pipe and 3/4" x 5" Recirculation Test Line x 7" Cusset plates79-387 34-EBD19-H79 Main Steam (upstream of Slenderness ratio > 200 1/2" x 4-1/2" stiffener bar MS-107A) added to I-beam, replaced kickers with W4 x 13 I-beam 79-388 6C-EBD14-H(3 Auxiliary Feed Pump 1-2 Slenderness ratio > 200 Replaced kicker with 4" x 4" x 4

Discharge 3/8" structural tubing 79-389 31-CCB21-H22 Letdown Delay Coil SF < 2 1/2" x 5" cover bar added 79-390 33A-CCB4-H5 High Pressure Injection Slenderness ratio > 200 3/8" x 3-1/2" bar added to 1-2 Suction flanges79-391 34-6CBS-H2 Containment Spray Pump 1-2 Slenderness ratio > 200 3/8" x 4-1/2" stiffener plate Discharge added to' kicker 79-392 36-RBC39-H8 Component Cooling Water Slenderness ratio Jr 200 -

3/8" x 4-1/2" stiffener plate Supply to Letdown Coolers added to kicker 79-393 41-HBC36-H26 Service Water Outlet of SF < 2 1/4" x 2-3/4" stiffener plate component Cooling Water added, W6 x 15 beam added Heat Exchanger 1-3 3

G cEa it'79- 106

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