Health and Safety Executive INDUSTRIAL RADIOGRAPHY ACCIDENT IN THE UK David Orr H M Specialist Inspector of Health and Safety (Radiation) Health and Safety Executive

Health and Safety Executive Industrial radiography accidents/incidents in UK: Approx 10 per annum but very rare that doses received > dose limit Vast majority relate to detached gamma source Last 2 major accidents (doses > dose limit) happened in radiography enclosures. Main failings: Poor risk assessment Poor contingency plans; not properly rehearsed Too much reliance on RPA

Health and Safety Executive Accident with Yb-169 radioactive source: Radiographers didn’t understand nature of source Yb-169 used (rare in UK) instead of more usual Ir-192 Dose rate from Yb-169 source much lower: 740 GBq Ir m 85 GBq Yb m Energy of Yb-169 gamma much lower and much more easily shielded 10 th value thickness 12 mm lead for Ir mm lead for Yb-169

Health and Safety Executive Radiographers didn’t understand source design/construction: Special form source (capsule only) Source capsule “screwed and glued” in position Source capsule not welded to holder to allow for low gamma energy Very different to normal Ir-192 “pigtail”

Health and Safety Executive Radiographers didn’t understand design of source:

Health and Safety Executive Work was being carried out in enclosure/clean room on large metal component Enclosure safety features – Shielding OK Automatic wind-out interlocked to access door Fail to safety warning lights Gamma alarm inside enclosure but had to be switched on separately to other systems Due to low energy of source gamma alarm could not detect detached/lost source inside component

Health and Safety Executive

Health and Safety Executive

Health and Safety Executive

Health and Safety Executive Access for guide tube was difficult: Required use of bends tighter than manufacturer’s recommendations Some examinations required use of manual wind-out as automatic wind-out unable to deploy source. Many of safety features not operational with manual wind-out Bespoke guide tube designed with open ended snout to facilitate better images and prevent “contamination” of component

Health and Safety Executive

Health and Safety Executive Techops 880 container being used: One of standard source containers in UK Good safety features Radiographers were unaware that dose rate on outside of container was the same whether or not source was present

Health and Safety Executive Techops 880 container used

Health and Safety Executive What happened ? Radiography being carried out with manual wind-out Gamma alarm was not switched on Unknown to radiographers, source glue had broken Torsional forces applied to source capsule when driven around steep bend causing source capsule to unscrew

Health and Safety Executive Last radiograph of the day - source fell out of open ended guide tube into component. Presence of lost source not detected by gamma alarm Radiographer retracted source – positive indication on source container that source was “home” Monitoring of source container “indicated” that source was present

Health and Safety Executive Radiographer left for evening and component wheeled from enclosure to clean room Welders arrived and carried out next welds At end of shift spotted “source” inside component – looked like small screw Source removed and passed amongst welders

Health and Safety Executive Radiographers returned for next shift - EPDs alarmed on approaching source (set to alarm at 100 μSv/h) Alarms ignored – assumed battery was low Radiographers handled source Finally radiation monitor switched on and presence of source identified Source recovery plan put in place

Health and Safety Executive Consequences: Several welders and radiographer received hand doses above dose limit but no deterministic effects observed Whole body doses increased but below dose limit Dose consequences could have been much much worse IN served for inadequate risk assessment Nature of source Suitability of warning/safety devices Use of bespoke equipment Company to be prosecuted in Crown Court