Published: Mar 16, 2019
This blog article first appeared on the old Ionactive website site in January 2012. It is not the intention to use every article since Ionactive’s birth in 2002, but there are several blog entries that I think are worthy of a new readership. The following has been through light re-edit.
This is taken from the IAEA News Channel (Nuclear & Radiological Events)
(Please note the spelling and grammar from this report has been preserved as submitted at the time).
Accident in Industrial Radiography
[12 January 2012, Peru, Chilca, Lima, posted 19 January 2012, INES = 3 (provisional)]
A radiographer was taking several radiographic films to a pipes by the night. In order to be sure that the guide tube was correctly the radiographer went to the tube guide an collimator to fix them. This operation was made by 40 times.
Eventually the radiographer touched with his left hand, at least 10 times, the tube guide where the source was unnoticed. Also, two auxiliar staff went to the radiographer position carrying the films to be checked at least by 40 and 20 times. The radioactive source was 3199,5 GBq Ir-192.
The event was detected at the end of job. The radiographer adviced to radioprotection officer who jointly to other operator rescued the radiactive source in safely manner. Operator showed mild symptoms as nausea and womiting and other just nausea, but after all this symptoms are finished. The finger of operator showed a blistering at the fifth day. Based in first calculations, symptoms and dosimeter reading the operator could have received 6 - 7 Gy to whole body and > 50 Gy to finger. The other personnel could have received doses from 1 to 3 Gy.
Currently, the personnel is being admitted to the hospital and citogenetic dosimetry will be performed to adjust the doses.
The incident log for the above event can be read at the following link: IAEA News Channel - Accident in Industrial Radiography.
Note that the report we reference above is provisional and only contains a basic summary of the events. Furthermore, English is a little wonky and so there may still be some interpretation issues that may change the circumstances as currently stated. [2019 - there does not appear to be an update of this incident on the IAEA website].
The description is unclear and it's not obvious how many times the source was actually exposed whilst the workers were near the guide tube (where the source is driven into during exposures). Normally (and correctly!) the source is returned to its storage container after each exposure. In this case, we think the source was left in the guide tube and then the radiographers spent some time and effort positioning the guide tube where they wanted it. The report talks about this operation (near the guide tube) taking place 40 times. We cannot believe that the same mistake (source left out) occurred 40 times - so we conclude that the exposure was continuous whilst this individual and colleagues went back and forth positioning the guide tube and getting ready to take the shot.
No active dosimetry or radiation monitors used?
It is noted that the work took place at night. This is not unusual since open site industrial radiography will normally take place during quiet hours. The report mentions ‘dosimeter' readings so that suggests that at least one individual was wearing some form of dosimetry. However, unless it failed to operate (or be responded to), our reading of the report suggests that this must have been passive (i.e. a film badge or simple TLD). We note that industrial radiography accidents are occurring where ‘real time' (active) dosimetry has not been worn. Real-time dosimetry will give you instant information about the radiation field, the dose rate, the accumulated dose etc. Even the cheapest types can be set to give you an audible alarm. It appears that there was nothing like this present during the incident. Something like the following would have helped.
Notwithstanding lack of dosimetry, where were the real-time active monitors (dose rate monitoring equipment?). Was it available but not being used? Was it switched on but left near the source container and not near the guide tube? We do not know these details from the report - a working monitor near the source would have provided an instant indication that the source was exposed so that prompt action could be taken. The report says the event was ‘detected' at the end of the job - it is not clear if this was by monitoring, but we suspect this might have been visual (i.e. someone noticed the source in the guide).
Supervision / training / awareness of the potential radiation hazard
What about supervision and training? This is likely another case of inadequate supervision with the work being carried out by ‘industrial radiographers' who appear not to have a basic awareness of radiation safety. Furthermore, they appear to have little awareness of the hazard potential of the radioactive source. The report indicates that the source was Ir-192 at an activity of 3199.5 GBq (approx 86 Ci). That is a huge source in terms of radioactivity.
Dose rates from the Ir-192 radioactive source
Expected dose rates at 1m from the source (in air) would be in the region of 361 mSv/h. We have no idea about the working times, however the report indicates that one individual received 6-7 Gy whole body dose. [For purposes of this blog we assume 1Gy = 1Sv]. The positioning of the guide tube would not in our view take hours to perform, and if the report is correct then the individual was back and forth 40 times during this positioning process. [2019 - An alternative interpretation of the report is that 40 radiographic shots were performed, each time the guide tube was repositioned for the next shot with the source exposed. Even with such poor evidence of supervision and training, we find it hard to believe that this would have occurred]. It is likely that the individual was much nearer to the source than 1m for some of the time.
Dose rates at 10cm would be 36Sv/h and at 5 cm 145 Sv/h. These dose rates illustrate clearly that 6-7 Gy (Sv) whole body dose during this accident is quite possible. The report also suggests > 50Gy to the finger and at the time of writing blistering on day 5 after the incident. This is a clear indication of deterministic radiation effects (tissue reactions). This individual also displayed mild nausea and vomiting, whilst the other two (who appear to have had radiation exposures in the region of 1-3 Gy whole body dose) just nausea.
Certainly, for the most exposed individual, these radiation doses are life-threatening. 6-7 Gy whole body dose it at the upper end of what is conventionally said to be survivable (without medical intervention). Even with medical intervention, the outlook for this individual is poor.
Overall, a totally avoidable incident. [2019 - And there is still poor practice in some areas of industrial radiography].