ML20059L039
| ML20059L039 | |
| Person / Time | |
|---|---|
| Site: | University of Illinois |
| Issue date: | 11/09/1993 |
| From: | Holm R ILLINOIS, UNIV. OF, URBANA, IL |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9311160279 | |
| Download: ML20059L039 (3) | |
Text
1 Univ;rsity Gf Illin21s at Urb n:-Champ;ign Nuclear Reactor Laboratory l
DJoartment of Nuclear Engineering / College of Engineering j
214 Nuclear Engineering Laboratory 217-333-7755/0R66 f
103 South Goodwin Avenue 217-333-2906 fax Urbana,IL 61801 e-mail: reactor @ux1.cso.uiuc.edu i
i November 9,1993 Docket No. 50-151 Director I
Office of Nuclear Reactor Regulation Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555 Subiect: Reporting of Abnormal Occurrence per Technical Specification 1.14 (e) "An i
uncontrolled or unanticipated change in reactivity".
Occurrence 3
At 1045 on Monday, November 8,1993 while setting up the reactor for s pulse utilizing the entire length of the Adjustable Transient Rod (ATR) a probleu was -
i dit : overed in an apparent binding of the ATR externally threaded cylinder (see attached
{
diagram) and the piston. With the reactor critical at 15 watts the externally threaded l
cylinder was being driven to the top in order to pulse the rod out of the core when the i
ATR piston appeared to bind and lift the rod off the bottom. This was immediately indicated by a change in the visual rod position indication on screen changing from gray (rod down) to green (rod in some mid-position). The operator immediately stonned movement of the externally threaded cylinder, total movement was approximately 50 divisions (6.36 cents reactivity). The operator then drove all rods i
into the core and notified the Reactor Supervisor of the occurrence.
l Corrective Action The occurrence was reproduced with the reactor shutdown at approximately the same position of the externally threaded cylinder. The cylinder was subsequently cleaned i
and honed slightly with emery cloth and then relubricated. Repeated testing of the cylinder with the reactor shutdown indicated no further problems. All surveillance and j
maintenance procedures were followed in troubleshooting the problem and the I
subsequent return to operation of the Adjustable Transient Rod. The semiannual surveillance on the ATR is scheduled on November 22nd and a detailed inspection will take place at that time.
110000 4 W 9311160279 931109 PDR ADOCK 05000151 i l S
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Comments i
The rod movement was immediately recognized by the reactor operator and acted upon i
accordingly. The amount of reactivity inserted was extremely small (6.36 cents),
ANSI /ANS - 15.1 - 1990 does not recommend reporting of unanticipated reactivity changes of less than one dollar. This change to the facility Technical Specifications is in progress.
I The Adjustable Transient Rod does not perform any safety functions, this is I
accomplished with the three manual rods which were operable at the time.
Normal operation of the ATR is to apply air with the rod on the bottom and utilize it in a banked fashion with the manual rods. When the ATR is used for pulsing it is almost invariably only the lower 50 % that is used since the Fast Transient Rod is used for the majority of the reactivity insertion. The operation that occurred on November 8th is therefore unusual in using the entire length of the ATR for a pulse.
l The mspection of the inside of the externally threaded cylinder seemed to indicate a slight buildup of dried lubricant or perhaps a burr at the point at which the piston stuck.
Due to the highly reflective nature of the polished interior of the cylinder this was difficult to see. Removal of the old lubricant, cleaning the interior with emery cloth j
and relubrication of the cylinder has restored the ATR to its normal operation.
Respectfully, msf Richard L. Holm Reactor Supenisor Attachment cc: B. Jones, Head, Department of Nuclear Engineering D. Hang, Interim Reactor Director Regional Administrator, Region 111, USNRC File
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