The following report was received from the
Maryland Radioactive Materials Division via email:
This afternoon [3/15/17], our [Johns Hopkins University (JHU)] JL Shepherd Mark I irradiator malfunctioned. This is a manual model. The source is lifted up into position by a knob that lifts a rod attached to the source. When lifting the knob up, the rod became jammed. The rod is stuck in an up position, slightly past halfway. It will not move up or down.
JL Shepherd was called for help. One suggestion was to move the knob slightly from side to side while lifting or lowering. This had no effect. Because this is a manual model not much can be done besides a repair by manufacturer. The technician [at JL Shepherd] said the most likely cause was due to some part (bearing, spring, etc.) falling down into transfer tube causing it to jam.
The irradiator's power supply is controlled by computer and is off now. The door latch on the irradiator is locked. The alarming area radiation monitor on the irradiator door is on and functioning. The key to both the irradiator controller and the door latch have been removed from the irradiator room. The irradiator room is locked and monitored by corporate security and a Remote Monitoring System. The irradiator room is only accessible to approved individuals. Because this unit is a self-shielded irradiator, radiation levels outside the unit are minimal, <0.2 mR/hr) even with the source being partially exposed inside. There is no sample inside the chamber. There is no way to physically open the irradiator door due to an electric interlock. The interlock will not function without power and will not function without the rod in the fully down position. A sign has been put on the irradiator, 'Do Not Use'.
JL Shepherd was scheduled to visit [the JHU] site to calibrate another irradiator in March. On Thursday we [JHU] will find out when we [JHU] can have a technician here to fix the problem.
Source Make: J.L. Shepherd and Associates
Source Model: 6810-G
Source Serial #: 81Cs-S14
NSTS Source ID Number: 6729
Isotope: Cs-137
Activity: 5329 Ci
Activity Date: 02/25/2017
MD Event Report ID No.: 52613