While the Nuclear Installations Inspectorate has several hundred staff, there are just half a dozen specialist radiation inspectors responsible for monitoring the safety of industrial radiographers.
Figures compiled by the National Radiological Protection Board show that in 1991, more than 60 industrial radiographers received doses greater than the investigation level of 15 milliSieverts, set by the Health and Safety Executive. About 10 radiographers were exposed to more than the legal maximum of 50mSv.
In contrast, just seven workers in the nuclear industry received more than 15mSv, and none received more than 30mSv. The figures are even more disproportionate than they seem, for there are fewer than 8,000 registered industrial radiographers on the board's database, but five times as many nuclear industry workers.
In a statement earlier this year, Chris Willby, head of the radiation policy branch of the Health and Safety Excutive, warned that 'although radiation doses to workers in Britain have been falling steadily overall, this has not been reflected in industrial radiography. Inadequate control of industrial radiation sources can lead to substantial exposures to radiographers, and we are aware of several serious incidents.' Remarkably, the HSE statement did not cite Mr Neilson's case among the incidents it listed.
Industrial radiography uses gamma rays or X-rays to reveal flaws in metal objects - usually defects in welded joints. The integrity of such welds is critical to industrial safety, because if flaws are present, high-pressure pipework may break or vessels shatter causing explosions or other damage.
Frequently, however, the welds are in places inacessible to conventional X-ray machines, which are large and heavy and need to be connected to an electricity supply. Instead, industrial radiographers use radioactive sources - small metal rods, like pencils, which have been irradiated in nuclear reactors. These portable rods emit gamma radiation continuously - unlike an X-ray machine, they cannot be switched off. For safe handling they are kept in lead- shielded containers.
A radiographer will surround the region to be radiographed with a lead collar to direct the gamma rays in the required direction and prevent them from spreading. The source is brought up inside its protective container and then wound out by remote control. In principle, its radiation should be confined and the radiographer should receive a mimimal dose.
In practice, however, the difficult conditions under which industrial radiographers work, coupled with the fact that they are not unionised and do notwork for large companies with experienced central health and safety departments, leads to less rigorous behaviour. Some experts fear that the economic structure of the industry encourages a casual attitude to safety. Many radiographers are paid piecework rates - according to how many welds they have X-rayed. As precautions take a lot of time, piecework provides a powerful financial incentive to skimp on safety.
(Graphic omitted)Reuse content