ML19224D786

Final RO Rept Re Failure of Experiment Scram Circuit to Function During Surveillance Testing Due to Malfunction of Reset Switch.Caused by Dust on Moving Parts.Switch Cleaned & Immediately Functioned

ML19224D786
Person / Time
Site:	05000128
Issue date:	06/25/1979
From:	Feltz D TEXAS A&M UNIV., COLLEGE STATION, TX
To:
References
NUDOCS 7907170040
Download: ML19224D786 (2)

Text

. .

TEXAS A & .\1 U NIVE RS IT Y NUCLEAR SC!ENCE CENTER -y-~ p.

CCLLEGE STAT!ON TDAS 77343 a

_W J = =-

25 June 1979 Mr. G. L. Madsen Office of Inspection and Enforcement Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76012 Ref: Docket No. 50-128

Subject:

Failure of an Experiment Safety Circuit Reported 6-15-79

Dear Mr. Madsen:

Enclosed is a final report of a reportable occurrence observed during surveillance te sting of scram circuits at the NSCR. This report is submitted in compliance with Section 6.4 and 1.8.c of change No. 11 to the Technical Specifications, Facility License R-83 for the. Juclear Science Center, Texas A&M University.

Respectfully,

?

1 gl L tA.s Eb' /

Donald E. Feltz #

Associate Director cc: R. R. Berg, Chairman Reactor Safety Board Texas A&M University M

356 m 5'/o 79071706 /0, TE'AS ENGAEin!NG EXPEWVE%T STAT!CN PECEARCM AND DEVELCPVENT FCR VAN 1;hD

~ .

A Report of the Failure of an Experiment Scram Circuit Reportable Occurrence on 15 June 197E during surveillance testing of scram circuits, an experiment scram circuit failed to function properly. The circuit is associated with the Beam Port No. 4 neutron radiography cave entry door. This circuit provides a reactor scram upon entry if the reactor is positioned within 18 inches of the beam port target. The reactor was not operating at tha time.

Failure Analysis The failure of ti.e scram circuit was due to a malfunction of the " Experiment Scram R set" switch on the reactor console. Tae switch failed to mechanically switch contacts and dust was observed on the moving parts of the switch.

Conclusions and Corrective Actions The switch was cleaned and immediately functioned properly. Other switches on the reset panel were also cleaned to prevent possible malfunctions. The switch was tested daily for the next 3 days of reactor operation without a failure. This problem is not expected to reoccur due to a recent change in the reactor console instrument cooling system. The present console instrument cooling system produces a positive pressure filtered air flow through the console. This greatly reduces the dust collection within the console when compared to the old system that created a negative pressure within the console, thus drawing in unfiltered air through opea or poorly sealed areas of the console.

In addition to scheduled surveillance, the beam port No. 4 experiment scram circuit will be checked when the reactor is positioned within 18 inches of the beam port target.