Radiation Protection Today - Spring 2022 | Page 20


Retired member Simon Morris worked for 40 years in the nuclear industry largely as a Corporate RPA . This article explores inexperience , hastiness , luck , instinct and respect for radioactive source material . It identifies good practice used today .
Source safety on the hoof
An Operational Health Physicist ( OHP ) or RPA may have to deal with a contingency in their career . In most cases this could be due to a radioactive source and in all likelihood , radiography . The first time this happened to me was only a few months after graduating in 1979 with a Health Physics ( HP ) Degree , and I have learnt a lot since then .
First to tell the story the way it happened .
As a practical person I loathed being deskand office-bound . Unusually and with scepticism , I requested to work for a period as an HP Monitor , overseen by a Supervisor who had years of experience . This was invaluable .
One desk-bound afternoon ( following my HP monitor stint ) my Area HP received a call and immediately handed the task over for me to solve . The incident was inside a walled enclosure being part of a production assembly line , an area I had never been in before . Outside the cell you could hear the alarm and all lights were red .
Defeating the cell door interlock , I entered . The cell had its own atmosphere . Adrenaline kicks in with the deafening alarm and flashing lights . Almost central to the room is a tube projection , standing vertically up from the floor with a small silver object on top . This configuration had been locally designed ( my guess ) with the source holder modification preventing its safe return .
Gingerly I approached holding what must have been a post-war MOD large wooden ionisation chamber detector ( 250 x 250 x 250mm ). On its lowest dose rate setting it showed a Full Scale Deflection ( FSD ) which was repeated on the second setting . One step in on a higher setting another FSD . Two steps in , now on its highest setting , it went to FSD and then immediately hard swing back to zero . I recalled a University lecture about saturation and decided to leave immediately .
Another graduate colleague ( instrument engineer ) working in a different department had recently received a unique telescopic radiation instrument . Of course it had not been calibrated or tested anywhere , all the same I thought this would be better than what I had initially used .
Seeking advice from my trusted Supervisor I returned , armed with the telescopic monitor , with the longest ceevee reachers I could find , a source pot ( large hole ) with lid and a scaffold pole , back into that atmospheric cell . The telescopic detector confirmed a very significant dose rate so I kept back . After a few practice swings with the scaffold pole I knocked the source off onto the floor . Using ceevee reachers the source was placed in the lead pot . The alarm was silenced at last . The next task was to get my film badge processed .
What would happen today , hopefully a different story ?
An RPA would have previously documented a radiation risk assessment , to ensure that any locally engineered modification could not impede the manufactured safe source exposure mechanism . Additionally , this would identify possible accidents and all relevant contingency plans . These plans would describe the actions needed to be taken , equipment and training required to enact each plan . Aided by a photograph of the normal exposure situation .
20 Radiation Protection Today www . srp-rpt . uk