XRD Shutter failure

[rod.ice@nnrc.gatech.edu (Rodney Ice)]

        I have recently experienced an X-Ray Diffraction Unit Shutter
failure that resulted in an extremity exposure.  The shutter was a Charles
Supper shutter, approximately ten years old.  The shutter, depending upon
the mounting plate, can be used on a variety of X-Ray Diffraction units.
The shutter failed to close due to lost tension of the spring around the
solenoid piston.  In addition, the "hairline" wire that closes the audible
alarm warning signal was displaced from its original position needed to make
contact.
        A survey of other XRD's on campus located one additional Charles
Supper shutter of approximately the same age.  Evaluation of this second
shutter indicated a loss of spring tension, however not to the degree of the
shutter that caused the incident.  This second shutter also had the audible
alarm "hairline" wire out of alignment but it was still making periodic
contact. The user of the equipment had noted in the user logbook that he was
having problems with the shutter and that it possibly needed cleaning.
        There is a red warning "flag" or "pin" that extends out of the
shutter mechanism that also indicates that the shutter is open.  In both
cases, our users had molded  thin lead sheets around the shutter so that the
pin was not visible.
        I suggest that you check any XRD units that you have that are
operated by aging Charles Supper shutters.  Specifically check the red
"flag" or "pin" for smooth, easy and full tension.  There should not be any
free play in the "flag" or "pin" of the shutter.  Any free play indicates
only partial or no closure of the shutter.  Futhermore, check with users
regarding the audible signal. Is the signal clear and non-varying in
intensity?  
        Although both symptoms (flag and audio) appear to be independent
problems, both are indicative of aging shutters that should be replaced.    
        
Rodney Ice
Nuclear Engineering, Georgia Tech