ML20079H092

Part 21 Rept Re Failure of Roll Pin Mfg by Cardinal Industrial Products,Corp & Used on DG Damper Actuator Due to Phosphorus Segregation Caused by Improper Tempering Heat Treatment.Inlet & Outlet Dampers on DGs Opened

ML20079H092
Person / Time
Site:	Fort Calhoun
Issue date:	08/27/1991
From:	Gates W OMAHA PUBLIC POWER DISTRICT
To:	Martin R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20079H094	List: ML20079H092 ML20079H130
References
REF-PT21-91 LIC-282R, NUDOCS 9110100136
Download: ML20079H092 (3)

Text

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Omaha Public Power District 444 South 16th Street Mall Omana Nebraska 68102-2247 August 27, 1991 402/636-2000 LIC-91-232R Mr. Robert D. Martin Regional Administrator U. S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011

Reference:

Docket No. 50-285 bear Mr. Martin:

SUBJECT:

10 CFR Part 21 Report Concerning the Failure of a Roll Pin Omaha Public Power District (OPPD) has investigated the failure of a roll pin tsed on the diesel generator damper actuator and determined the failure to be reportable pursuant to 10 CFR Part 21. OPPD notified Messrs. J. P. Jaudon and W. M. McNeil of the Region IV office on August 23, 1991, of the attached information. Attached is information required pursuant to 10 CFR Part 21.21(b)(3).

If you have any questions, do not hesitate to contact me or members of my staff.

Sincerely,

&W. G.ZZ. Gates

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Division Manager Nuclear Operations WGG/sel Attachments c: LeBoeuf, Lamb, Leiby & MacRae Dr. T. E. Murley, Director of Reactor Regulation (3)

W. C. Walker, NRC Project Manager R. P. Mullikin, NRC Senior Resident Inspector Document Control Desk 9110100136 910927 PDR ADOCK 05000285 s non es* 07007G *22=c*== r 6/f

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INTRODUCTION On July 11,1991, at - the Fort Calhoun Station (Mit No. 1,. during the i

-performance of the monthly diesel generator surveillance test, diesel

' generator :DG-2 ' was manually shutdown following a high- Jacket water

~ temperature alarm. It was determir.ed that the exhaust damper which allows air flow through the radiator did not opens Investigation revealed that a roll pin (used as aishear pin preventing the damper from open)ing.on On July the damper 18 1991actuator 3 the rollshafti had pin for thefailed,

- redundant diesel generator (DG 1) was removed, and a visib'le crack was discovered,.

In response, the failed pin from DG 2, the pin from DG-1 which contained a visible crack, and a spare pin ~ from the same manufacturing lot number were submitted to a metallurgical laboratory for ena?ysis.

NATURE 0F DEFECT-The metallurgical analysis-indicated that the cheMcal composition of the roll pins conformed to ASTM A682 Grade'1070 steci that had been quenched and tempered - to -produce a- tempered martensitic micro structure. The-hardness of the steel, which ranged-from 48-50 Rockwell C, was appropriate for the desired application.

A -calculation of the shear strength of'the roll pins obtained by utilizing the hardness to strength correlation found that +he pins met the design shear. requirements.

The fracture -surfaces of the failures were found to be intergranular caused by phosphorus segregation at the grain boundaries. Phosphorus also created-banded-areas from which cracking originated. Both the failed-and cracked:- roll pins were found to - have . cracking caused - by the same embrittling mechanism. Since subsurface cracking was found in all three

--of the pins, including the unused p,in, the cause of failure cannot- be attributed to: operating conditions or environments. . It was determined that the failure of the pins was due to phosphorus segregation caused by-an improper tempering heat treatment or manufacture of the steel during.

solidification of the ingot.

The final netallurgical report was received by-0 PPD on August 15, 1991.

The report included discussion on' the above failure mechanism of the pins, the material composition'of the pins, the tats the by the laboratory and the stated cause of failure. pins were subjected to IDENTIFICATION 2F SUPPLIER The roll pins which failed were purchased under 10 CFO Part 21 and Part 50 Appendix B requirements in December 1988 under.0 PPD Purchase Order 5040618 from:

Cardinal Industr'ial Products Corporatien 3873 W.'0quendo Road Las Vegas, Nevada 89118 '

-The pins are specified as:

1/4 x 3 1/2 inch A682-77 Gr. 1070 Spring Pins, Lot 8733602-1 1

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10 PPD verbally notified Cardinal Industrial Products Corporation on August

16, 1991-' informing Mr. D. Hathcock-- Manager Quality Assurance of OPPD's--

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intent ~ to conduct an evaluation. of the . deviation- tot determine if the

failure of these pins could create a substantial safety hazard pursuant to

-10 CFR Part 21.

This evaluation concluded that the deviation'in the roll pins could create

' a- Engineering Analysis Request 91-040,- substantial- safety hazard and

~therefore the failure is being reported pursuant to 10 CFR Part 21. This determination was made on August 22, 1991 after review and evaluation of.

the final . metallurgical report.

l I LOCATION OF COMPONENTS IN USE' An investigation is being conducted into the-location of the remaining roll pins received under this purchase order. To date, no other roll ) ins from this-purchase order have been found to be installed at fort Calioun Station.

' CORRECTIVE ACTIONS TAKEN

As corrective action, both inlet and outlet dampers were ooened on both-diesel ~ generators, and an emergency temporary modification was installed which blocked both exhaust dampers-open..

Cardinal Industrial Products' Corporation was contacted on August 23, 1991 concerning the final ~ determination of OPPD's evaluation. Information concerning the specific metallurgical testing conducted for OPPD has been transmitted to.-Cardinal and five roll pins from the-subject lot have.been provided to__ Cardinal.to conduct additional testing.

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