Reducing Risks from Sources in Industrial Uses

 

Lessons to be learned

The following are but a few of the accidents that have occurred in the last 20 years, where lapses in good practice, human error, or lack of knowledge have resulted in serious injuries and deaths. A review of the root causes of these accidents reveals a worrying similarity.

Fatalities in Morocco

In 1984, a serious accident resulting in eight deaths occurred in Morocco when an iridium radiography source became disconnected from the drive cable and was not returned to the shielded container. The disconnected source eventually dropped to the ground where it was picked up by a passerby and taken home. The tiny source was too small to have warning markings, although the exposure device itself was marked with the international radiation symbol (trefoil). Over several months, several family members and relatives were exposed and died; the clinical diagnosis was “lung haemorrhage”. Only after the last family member died was radiation suspected as the cause.

Investigation determined that this accident might have been averted had a radiation survey been performed after the radiography to confirm that the source had properly returned to the fully shielded position.

Contamination in Spain

In May of 1998, an unnoticed caesium-137 source was melted in an electric furnace of Acerinox, a stainless steel factory located in Los Barrios, Spain. As a consequence, the vapours were caught in a filter system resulting in contamination of the 270 tonnes of dust already collected. The dust was removed and sent to two factories for processing as a part of their routine maintenance. One factory received 150 tonnes that they then used in a marsh stabilization process, increasing the mass of the contaminated material to 500 tonnes and contaminating the marsh. The first warning of the event was in early June from a gate monitor that alarmed on an empty truck returning from delivering the dust. Several days later elevated levels of caesium-137 were also detected in Southern France and Northern Italy.

The radiological consequences of this event were minimal, with six people having slight levels of caesium-137 contamination. However, the economic, political and social consequences were major. The estimated total costs for clean up, waste storage, and interruption of business at the affected companies exceeded $25 million US dollars..

The root causes of this accident were the loss of control over the caesium source and the fact that the steel factory did not detect the lost source in the load of scrap metal when it was received.

Serious Injury in Peru

In February 1999, a section of pipe was being repaired at the Yanango hydroelectric power plant in Peru. While the repairs were being completed, a gamma radiography device was left unsupervised and locked with the drive cable, but not the guide tube, connected inside the pipe. At some time during the day, the iridium source became detached from the device. A welder picked up the unshielded source, put it in the back pocket of his pants, and later returned home.

By the time the source was discovered to be missing, some nine hours had elapsed and both the welder and his wife were exposed to radiation. The most serious injury was to the welder from direct contact with the source, which resulted in the amputation of one leg and lengthy hospitalization.

Investigation determined the root causes to be inadequate supervision of the source at the work site and lack of training by the person responsible for the radiography. The welder was unaware of radiation hazards. The design of the source device was also found to permit the lock to be removed with an ordinary screwdriver, hence the source could be easily removed. How the source in this instance came to be detached from the device was never conclusively determined.


 

 


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