ML19253A397

LER 79-026/01X-1 on 790228:pipe Supports Failed,Resulting in Falling of Condensate Piping.Caused by Generic Problem in Concrete Fasteners Due to Improper Installation

ML19253A397
Person / Time
Site:	Hatch
Issue date:	08/10/1979
From:	GEORGIA POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19253A396	List: ML19253A394 ML19253A397
References
LER-79-026-01X, LER-79-26-1X, NUDOCS 7908240440
Download: ML19253A397 (3)

Text

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OATE EVENT oesCa: PTic's ANo PACSABLE CONSEQUENCES h o#2 l During conduct of the MSIV Closure test as part of the Startuo Test Program, various I _

O 3  ; piping supports ' failed resulting in a section of condensate-feedwater piping falling. ;

o 4 I Non-destructive testing was performed and revealed that the stresses incurred by the I ois I pipino section were below the code allowables. Subsequent testing of the cor.creie l

o is I fasteners associated with pioina succorts ir, safety systems revealed a ceneric orob- l oI7 l 1em with t he concrete fasteners. I o14 l l 7 4 9 do S Y S T ! *.I CAUSE CAUSE CfvP VALys CCOE CCCE SUSCODE CO*.?PONENT CODE SYSCOOE SU8OOOE o!3 i z z i@ 18 l@ I C l@ IS 10 l P l 0 l R l T l@ l X I@ l_Z_J @ ,

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i ii [ revealed that thecause of the failure of the supoorts was due -to the concrete fasten- I i i lers. The inspection revealed that the failure of the concrete fasteners was directly 1

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D 7@D Wf flARRATIVE REPORT LgR 4870-26 During conduct of the MSIV Closure Test from 100% power, Februarv 14, 1079, piping sucoort exoanston anchors failed in the HtI P- 2 Turbine /Contaol Butiding Main Steam Pipe Chase area, -

which caused a section of the reactor feedwater system pi. ping to fall through a distance of aoproximately twelve to fifteen inches, coming to rest intact on the elevation 147'0" (MSL) floor slab. An inspection of the piping, damaged supports and failed anchors was condveted by olant peasonnel, as well as by -

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engineers ~ ~ '

for Bechtel Power Corporation; Gaithersburg, Maryland, and ITT Phillips Drill Division.

The inspection revealed that the cause of expansion anchor e failure was directly a t t r i.b u t a b l e to improper expansion anchor installation, in that the anchors were installed in oversize holes and the degree of exoansion did not result in adequate holding / load caoacity. The MSIV closure test, although the test results in a hydraulic transtent for the reacto" feedwater system, is not viewed as a majo" contributing factor to the failure of the concrete expanston anchors.

As a result of the otoing section f a l l.i n g , a stress analysis was performed to determine the stress levels exoerienced by the reactor feedwater pioing. The analysis revealed that the most highly stressed point in the " unsupported" reactor feedwater piping resultant from the fallen piping is at the 18 x 24 inch ptpe reducer fitting (see Figure 1, Isometric 2N21-100, Revision P). The stresses at this point in the piping system although higher than other stresses, were not in excess of the code allowable stresses.

Subsequent to the stress analysis, an ultrasonic examination of piping welds was performed at both ends of the 18 x 24 inch piping reducer fitting. The ultrasonic examination revealed no recordable indications. Records of this ultrasonic examination are available for review at the plant site.

Expansion anchor testing at HNP-2, as described in Item 4 of USNRC IE Bulletin No. 79-02, was initiated on or about the week of Feb"uary 10, lc70 The exoanston anchoa testing program was conducted in accordance with written procedures HNP-2-11004 and HNP-2-11009, P"ocedure H N P 110 0 3 , " Surveillance Procedure for Identifying Anchors Used for Hangens in Safety Systems,"

provided instauctions for the identification, location,_ and number of concrete expansion anchoas to be subjected to testing. Soecifically, only those piping systems required to function and/or succort other. systems necessaay to function to mitigate the consequences of the desistn basis accidents discussed in Chacter 15 of the HNP-2 FSAR were subjected to supoort anchoa testing and insoection.

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Procedure HNP-?-11005, " Inspection and Testing Procedure for Concrete Expansion Anchors", provides a detailed procedure for the testing and acceotance of concaete expansion anchors.

Concrete expanston anchors emoloyed in HNP-2 were generally of two types, self-drilling exoanston anchors and wedge style stud anchors. Testing of the self-det111ng expansion anchors -

entailed the follouir tvities:

1. Removal of the threaded ra . .a * (either a hex head bolt, or stud and nut) -

2. Visual examination or the anchor, to verify that the anchor " sleeve" is installed such that when the threaded fastener is torqued, the " sleeve" will not be in contact '

with the support base plate,

3. Insttu measuaement of the distance from the outer suarace of the base plate to the outermost (shoulder) portion of the " sleeve:, and a l. s o the outermost (tool oortion of the exoanston device or cone, 4 Insitu measurement of the base plate thickness, and determination of fastener diameter, length and thread engagement, and

5. Reinstallation of the thaeaded fastener and torque appiteation.

Testing of the wedge style stud anchors was a simpler process, consisting of length (determined by Ultra Sonic Testing),

diamete", minimum torque, and thread engagement vertftcationi.

In addition to the test performance, an engineering team was employed to review all data, compaae reoorted data with -

acceptance criteria and support drawings, and ultimately accept or ceject the installation tested.

Failure rates expeaienced were such that the testing program included the total anchor pooulation, in iteu of a statistical samole, and ultimately, (in the interest of economics and safety) a management decision was made to simply remove and replace the self-dailling anchors with the more easily installed and tested wedge style stud anchors.

Following aeactoa staatuo, as part of the Startup Test Program, a Turbtne '"ato Test at 1005 power and a repeat of the MSIV Closure Test at 100, power were oerformed. A subsequent v i s u a l. insoection was cerformed on the pioing suoports associated with the condensate feedwater pioing that fell previousiv and no problems weae identified.

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