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8/11/2014 - Overexposure of radiographyworker over the annual limit

This is taken from the IAEA News Channel (Nuclear & Radiological Events)

Exposure of radiography worker over the annual limit

[08 September 2014, Norway, Inspecta, Randaberg / Stavanger, posted October 2014, INES = 2(Final)]

Worker, wearing warning device (not dosimeter) was in a bunker with an unsecured source (Ir-192 - 555MBq).

Dose received approx. 32mSv.


The incident log for the above event can be read at the following link: IAEA News Channel.

Ionactive Comment

What strikes me about this entry is the lack of information - almost not worth publishing to the IAEA Events database. The point of featuring this on my blog is I wonder if this lack of information indicates a certain safety attitude in Norway regarding Industrial Radiography. I hope not.

8/11/2014 - Theft of Radioactive Sources

This is taken from the IAEA News Channel (Nuclear & Radiological Events)

Theft of Radioactive Sources

[14 February 2014, Peru, Ventanilla, Callao / SPI GAMMA, posted March 2014, INES = 3(provisonal)]


The incident log for the above event can be read at the following link: IAEA News Channel.

Ionactive Comment

Sadly have not had much time to update the blog page. This is due mostly to the amount of work that Ionactive is currently undertaking.

12/5/2014 - Exposure to workers ( 0.5 Gy)

This is taken from the IAEA News Channel (Nuclear & Radiological Events)

Exposure to workers

 

[14 February 2014, Peru, Ventanilla, Callao / SPI GAMMA, posted March 2014, INES = 3(provisonal)]

On the morning of 14 February 2014, a radiography company was performing non-destructive testing by industrial radiography with a 1,22 GBq Ir-192 source to several pipe joints in a chemical plant. The operations were performed by three operators (A, B and C) in a platform at nearly 12 meters height over the floor. In order to reduce the level of radiation in the area a tungsten collimator was fixed at the tip of guide tube.

For all the operations the gamma projector was lifted with a rope up to platform and the operator A climbed by a ladder taking the guide tube with the collimator fixed putting it inside the left pocket of his work vest. At the platform the operator A connected the guide tube then fixed the films to the joints and then coming down and operator B made the exposure. Operator C marked the films for being fixed in the tests.

The operators wore personnel alarm detectors, OSL dosimeters and also one portable radiation monitor. In one of these operations the radioactive source became detached and did not return to its safe position. The operators were not aware of this situation because the high noise from engines and machines in the work zone did not allow hearing their personnel alarm detectors but also because the portable radiation monitor was not used for monitoring the operations.

According the reenactment of accident the unaware exposure happened in the last three joint tests. After the test of last three joints they became hearing the alarm detector while walking away from the noise environment. At the discovery of situation they performed a monitoring to the gamma projector and guide tube discovering that the source was not inside the projector but in the tip of guide tube. The operators left the gamma projector and guide tube on the floor and then proceeding to recover the Ir-192 source which was safely placed inside the gamma projector in some 5 minutes using tongs and portable shielding. The operators notified the event to company manager which took them to a clinic for medical assessment.

The operator was in contact with the radioactive source around 30 minutes, having proved that the left hip was the most exposed area. The operator did not show any early symptoms at whole level although after 12 hours began to be noticed redness in the left hip. Currently the redness is disappearing. The doses received by the operator A were estimated less than 0,5 Gy to whole-body and the localized dose to its left hip was appraised in 16 Gy as average. Doses to operators B and C were 15,85 mSv and 17 mSv. Preliminary investigations indicate that the main cause was the non-compliance of protection procedures, for instance, the regular monitoring was not performed. Currently the investigations are under way to determine other contributors to the event. The regulatory body issued an order to the radiography company for stopping operations until causes are well determined.


The incident log for the above event can be read at the following link: IAEA News Channel.

Ionactive Comment

Sadly have not had much time to update the blog page. This is due mostly to the amount of work that Ionactive is currently undertaking.

The doses likely to have been received in the above case are large by all occupational standards for those working with ionising radiation. It just goes to show that even when real time active monitoring is worn - it is only useful if you can actually hear the alarm going off! Many other radiography incidents reporting in this blog have resulted in exposures where active dosimetry was not being worn. In this case it was worn- but might as well not have been.

The report states that the local dose of 16 Gy to the hip has produced reddening - clearly evidence of deterministic effects (which are considered intolerable in occupational radiation exposure).

12/12/2013 - Overxposure of an industrial radiographer

This is taken from the IAEA News Channel (Nuclear & Radiological Events)

Overexposure of an Industrial Radiographer.

 

[14 September 2013, Germany, Lingen Refinery, posted 18 November 2013, INES = 3(Final)]

On September 14, 2013, a person was exposed to high radiation in a refinery in Lower Saxony. This person is an employee of a company for non-destructive material testing based in Rhineland-Palatinate, which operates nationwide.

The evaluation of the employee's official dosimeter showed a radiation exposure of about four times the statutory annual dose limit for occupationally exposed persons. The affected employee had a whole body exposure of 75 mSv (statutory annual dose limit for occupationally exposed workers is 20 mSv).

In addition on the left hand considerable skin redness and burns have occurred. These are signs of exceeding threshold limit for hand and skin at least for a factor 10. According to estimates a skin dose of 10 - 30 Sv (statutory limit 0.5 Sv) is probably.

According to the current state of knowledge, there was a defect in the used gamma radiography device (Ir-192, 740 GBq). There was an offence against basic safety rules during fixing the defect. Furthermore, there were significant delays in reporting the incident to the relevant authorities and the medical care of the employee.


The incident log for the above event can be read at the following link: IAEA News Channel.

Ionactive Comment

Yet another industrial radiography accident. This time in Germany.

1/5/2013 - Overexposure of a worker (I-131)

This is taken from the IAEA News Channel (Nuclear & Radiological Events)

Overexposure of a worker (I-131)

 

[28 February 2013, Finland, MAP Medical Technologies Oy, posted 08 April 2013, INES = 2(Final)]

A laboratory worker was contaminated with I-131 in a radiopharmaceutical company on February 28 2013. The worker was wearing two pairs of gloves and, when changing gloves, had noticed a break in the right inner glove, but not any obvious break in the outer latex glove.

Only 3-4 hours later, routine monitoring revealed heavy contamination of the dorsal part of the right hand. Immediate actions to decontaminate the hand were undertaken on site. On the next day, besides persisting heavy contami-nation of the hand, activity was also found in the thyroid gland, and the Finnish Radiation and Nuclear Safety Authority (STUK) was notified. Stable iodine had not been administered.

Based on original measurements on site and later follow-up at STUK, including surface contamination measurements and whole body counting, the original activity of the hand was estimated at 11 MBq and the equivalent skin dose at 25 Sv, affecting an area of about 10 cm2. The estimated equivalent dose to the thyroid was 430 mGy and the estimated effective dose 22 mSv.

On her first visit at STUK, the worker was advised to wear a glove and change it frequently in order to protect the surrounding and promote decontamination by sweating and washing. Three days later little activity was left in the hand. 11 days after the incident the skin was dry and slightly desquamating. After 15 days the skin was intact with no desquamation left. No further signs of skin damage have occurred.


The incident log for the above event can be read at the following link: IAEA News Channel.

Ionactive Comment

I think this is quite a shocking case. Just look at the headline figures here: 25 Sv to part of the hand, dose to the thyroid 430 mGy and effective whole body dose estimated at 22mSv. (Personally I think the units used are a little wonky, but I will put that aside).

It is very important to note that this is not a nuclear incident (even though it's reported on the IAEA news event channel). This is very unlikely to hit the media - will be missed by most - but the doses received in this incident ARE NOT common in the nuclear industry (far from it) - under routine or accident situations to workers or members of the public.

According to their website, Map Medical Technologies develop and manufacture radiopharmaceutical for nuclear medicine professionals. There are many similar companies like this located all over the world doing similar work. Looking at the report of this case it makes me wonder how many similar exposures of this type might go undetected. There appears to have been a PPE (double glove) failure, combined with a lack of monitoring so that the hand contamination went unnoticed (for up to four hours). It is not clear if the thyroid contamination is a result of transfer from the hand, or due to direct intake at the workplace (during the initial contamination incident). I am inclined to think that latter - clearly radiological hygiene standards were considerably below expectations.

A lack of radiation  / contamination monitoring (again)

If you look at other incidents I have commented on in this blog, many being very different to this latest one, you will nevertheless see a common theme. Lack of monitoring. I spend considerable time during my training courses - drilling into delegates the fact that monitoring (passive, active, direct and in-direct) are the ‘eyes, ears - indeed all the senses combined' -and the only way to understand the radiological environment surrounding you. Without adequate monitoring you are effectively ‘blind' - and when blind significant radiation exposures can be delivered leading to events of this type.

Is 25 Sv local dose really possible?

I was curious to see if the estimated dose delivered to the hand was realistic (since 25 Sv is a massive localised dose, and 11MBq is a modest activity used in the medical sector). I ran my Varskin 3 code (a dosimetry model for surface / skin contamination). I used a skin density thickness of 7 mg / cm2, a 2-d disk (10 cm2), skin averaging over 10cm2, 11 MBq of I-131 with an exposure time of 4 hours. My results were around 8 Sv (Gy) which is about a 1/3 reported above. I re-ran the code with different geometry and skin thickness and you can approach 25 Sv (Gy) so I presume the dose calculations run for this individual would have been very specific. So the basic findings are that a localised radiation dose of 25 Sv is most certainly possible under the conditions outlined in this incident.

Wearing gloves

I then wanted to explore using gloves. I have no idea what type of gloves were worn so I used neoprene gloves with the following specification: density 1.23 g/cm3 with the thickness of 0.4mm. Assuming these gloves were worn intact with the contamination on the outer surface, then the skin dose over four hours is reduced by about a factor 8. With two pairs of gloves the dose to the skin over the exposure time reduces by a factor of about 50 (so using the original supplied data you might be looking at a hand dose of 0.5 Sv rather than 25) - still considerable, but considerably less.

The results of the calculations show that regular monitoring of the gloves during the work is a key measure to reducing exposures.

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This is the company blog of Ionactive Consulting Limited, a Radiation Protection Adviser consultancy. Visit here often to read our views on radiation protection and related matters. You can contact our director and RPA directly at mark.ramsay@ionactive.co.uk

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