R-30 Source Accident

The R-30 Source Accident was a nuclear accident that occurred at the Source Inspection Room (SIR) of the Isotope Handling Building (IHB) at the Dalston Laboratory in June 1981, resulting in the deaths of all personnel within the room.

Background

The Source Inspection Room (SIR) was a unique room within the IHB, designed to allow large sources to not only be visually observed but also weighed. There was a hot cell under the SIR where the sources were stored, and a thick, flexible lead membrane separating the hot cell from the safe area of the SIR. Sources would be weighed by lifting them up onto the membrane, which would then deform and contact a lifting plate above, which was in turn connected to a set of weights. The force required to lift the combined system, measured at the bottom stack, would be compensated and used to produce the final weigh figures.

The accident occurred due to an interlock failure within the SIR. Normally, the lifting hydraulics would not be permitted to raise without the lifting plate in contact with the membrane in the room above; however, the interlock system had been manually bypassed as technicians wanted to use the weighing system in creative ways that the system would otherwise not permit.

Accident

A number of employees were present in the room at the time of the accident; one inexperienced supervisor accidentally bumped the Raise Source button, which went unnoticed due to the lack of auditory warnings. The hydraulics began to raise the source that was currently loaded on the weigh system below, a high-activity Cobalt-60 source designated as "R-30". Personnel suddenly noticed the weigh membrane in the centre of the room bulging; the hydraulics, unblocked by the normal stack above, were free to move far further than usual.

A straining sound was heard as the membrane stretched to the breaking point, and then finally broke, exposing the hot source directly to the personnel in the room. Radiation alarms immediately began to sound, but as personnel rushed to evacuate, the emergency exit door, which was not often maintained and opened inwards, became jammed and stuck in position as they attempted to push it the wrong way.