Stuck Source with a Kinked Guide Tube
During a field exposure, the crank becomes hard to turn and then the source will not retract. The survey meter at 1 m from the guide tube reads 800 mSv/h; at the crank position 18 m away it reads 2.5 mSv/h. A radiographer is standing 2 m from the guide tube; the assistant is at the crank. The source is 2.2 TBq Ir-192. The guide tube is visibly kinked at the collimator and the drive cable is exposed. The site is a remote pipeline location; the emergency team is 45 minutes away. The radiographer wants to pull the guide tube straight by hand. The client’s workers are 100 m away.
1. State the immediate actions and estimate the dose rates at the two worker positions.
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The radiographer must not touch the guide tube or attempt to straighten it by hand. The first action is to evacuate both workers away from the source along a route that does not pass close to the guide tube, then establish a barrier and keep people out. Using inverse square from the 800 mSv/h at 1 m: at 2 m the dose rate is 800/4 = 200 mSv/h; at 18 m it is 800/324 ≈ 2.5 mSv/h, which matches the survey. A 1-minute stay at 2 m would give about 3.3 mSv; several minutes of manipulation could give a significant dose to the hands and whole body. The assistant at 18 m is in a much lower field but should still move back and secure the crank area. The radiographer should use the survey meter from a distance, note the readings and time, and call the RSO and emergency team. The client’s workers at 100 m should be moved further back or held in place if they are already outside the controlled area, and someone should prevent access to the source.
2. Describe the emergency response and recovery options.
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The emergency plan should be activated: secure the area, post signs and guards, notify the RSO, regulator and client, and request the trained recovery team. No one should try to crank the source back or pull the guide tube straight while the cable is kinked; forcing it can disconnect the source or expose the hands. The recovery team should approach with long-handled tools, additional shielding and personal dosimeters, and should rehearse the recovery before entering. If the source cannot be retracted, the team may need to place a shielded container over the collimator or use remote handling to secure the source. Because the emergency team is 45 minutes away, the on-site priority is to maintain the barrier and prevent access, not to attempt an unauthorised repair. The team should record dose rates, times and actions. If the source remains stuck for an extended period, the RSO should establish a continuous control point and consider a controlled withdrawal, but only with the emergency team and regulator informed.
3. What notifications, dose records and follow-up are required after the event?
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The RSO should notify the regulator under the emergency provision as soon as possible, and the client should be told that the job is stopped and the area is controlled. The radiographer and assistant should submit their dosimeters for processing and provide statements; the electronic dosimeter records and survey readings should be preserved. The RSO should estimate doses from time, distance and shielding, and arrange medical review if a significant dose is indicated. The equipment should be quarantined and inspected: guide tube, drive cable, collimator, crank and exposure device. The investigation should determine why the tube kinked, whether the cable was damaged before the job, and whether the pre-job inspection missed it. Corrective actions should include replacing damaged guide tubes, checking cable freedom before every exposure, training on the stop-work rule for a hard crank, and exercising the emergency plan with a 45-minute response assumption. Records should include the notification, dose assessment, equipment inspection, recovery log, client communication and corrective-action closure.