ML20215B821
| ML20215B821 | |
| Person / Time | |
|---|---|
| Site: | 05000294 |
| Issue date: | 06/09/1987 |
| From: | Wilkinson B MICHIGAN STATE UNIV., EAST LANSING, MI |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8706170467 | |
| Download: ML20215B821 (2) | |
Text
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IMICHIGAN, STATE UNIVERSITY - 2 y
COLLEGE of ENGINEEllING . EAST LANSING *1tlCHIGAh a 4ss241326 -
' DW1510N of ENGINEERING RESEABCH i
June 9, 1987 u
.U.Ss Nuclear Regulatory Commission ATTN: Document Control Desk &
Washington, D.C. 20555 ;:
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Subj ect: ~ bocket 50-294, ' License R-114.
Failure of Pulse Rod connector to )
3_ controlLrod extension 4
Centlemen:
Upon the occasion of initial startup of the MSU Trigt. reactor for'the. day June 2,'1987, it was noted that the shim and regulating rod positions for the 10 watt check were considerably-higher than wouldibe expected. The reactor was immediately shut down and an investigation initiated to determine the cause. .It was noted,that the poison section of the pulse rod' had'become disconnected from'its' extension-rod. The cont'r'o1 rod drive.was 1 fisconnected from the extension rod and.the examination of the bottom end of the extension showed that.the. aluminum top end fitting of the control rod-
' poison sectionL(which screws into the extension rod) had fractured. The c , poison.section.was extracted from'the core and examined. lNo damage to the L poison'section other than the fracture of the aluminum end fitting was
. observed., The integrity of the Boron Carbide. poison was apparently- .
unaffected. A temporary cable was affixed to the poiscu section to allow it '
to be reinserted into the core such that the reactor could be secured while
-a' solution to the problem was developed.
.Upon examination of the blueprints of-.the poison section, it was concluded.
that at .least 1-1/4 inch of aluminum remained between the fracture point and the Boron' Carbide. region. A proposed stainless steel insert was' designed-which would screw into the extension rod and into a tapped hole machined ,
into this aluminum sector. A safety analysis of this proposed procedure was prepared and, on June 3,1987, approved by the Reactor Safety Committee. It was concluded that the proposed modification would pose no additional safety hazard to the reactor and, in fact, that it.had the potential of being even safer than the original design. The Safety Committee authorized the modification of the control rod system. ,
The stainless steel insert was fabricated on 6/4/87 and the control rod ,
affixed to its extension rod. Drive pins were inserted in b'th o threaded l joints to assure that the joints would not unscrew. The control rod was re-
' installed in the reactor and rod drop times and rod worth measurements made to assure that the operation of the pulse rod was not affected by the F modification.- The reactor was returned to normal operation on 6/9/87.
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This report is being submitted pursuant to the requirements'of Section 1.9.
- c. and d. of license R-114,. Technical Speciffcations. It..is our opinion that, since the control rod remained fully in'serted in the core as a result of-the failure, there were no circumstances which could have' caused damage l to the reactor, release of radioactivity.or injury to any parties. _
Sincerely, l
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Bruce W. Wilkinson Reactor. Supervisor 1- ,
l I cc: United States Nuclear Regulatory Commission' Office-of Inspection and Enforcement Region 3 799 Roosevelt Rd. '
i Glen Ellyn, IL 60137 MSU Reactor Safety Committee.
R. Wilkinson, Vice President for Finance and Operations s, ,.,
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