Industrial radiography accidents/incidents in UK:

1. INDUSTRIAL RADIOGRAPHY ACCIDENT IN THE UKDavid OrrH M Specialist Inspector of Health and Safety (Radiation) Health and Safety Executive

2. 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

3. 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-192 - 2100 μSv/h @ 1m • 85 GBq Yb-169 - 90 μSv/h @ 1m • Energy of Yb-169 gamma much lower and much more easily shielded • 10th value thickness • 12 mm lead for Ir-192 • 2 mm lead for Yb-169

4. 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”

5. Radiographers didn’t understand design of source:

6. 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

10. 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

12. 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

13. Techops 880 container used

14. 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

15. 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

16. 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

17. 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

18. 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