Radioactive material transportation incident rated as level 2 on the INES-scale
On Tuesday 25 July 2017 NTP Radioisotopes (Europe) S.A. received a package containing a used radioactive source. The package originally came from Egypt and was transferred via Zürich to the airport of Zaventem where it remained temporarily stored since 13 July. NTP Radioisotopes (Europe) S.A. is a Belgian company, located in Fleurus, specialised in the production of radioactive industrial sources that can be used for industrial gammagraphy.
During the inspection of the package the dosimeter of one of the workers of NTP detected an abnormally high radiation level in the vicinity of the package. The radiation level exceeded the limits stipulated in the nuclear materials transportation regulation. NTP decided to shield the package, stored it in a safe place and informed the Federal Agency for Nuclear Control (FANC).
In consultation with the FANC and under supervision of NTP's physical control department, the package was then safely opened in a shielded cell. This showed that the radioactive source was not stored in a primary container, intended to shield the radioactive source and to limit radiation outside the package. The FANC then asked NTP to keep the package in the shielded cell until further notice. This enabled the FANC to prepare the further necessary steps to manage this incident.
The following day, FANC inspectors went to the site to assess the facts and measure the radiation level (dose rate) just outside the package. Measurements showed that the radiation level in the vicinity of the package exceeded the threshold of 2 millisievert per hour. Further investigation also revealed that the sender had not properly marked and labelled the package and it was not sealed. Furthermore, the sender prepared the package for transport and sent it without measuring the radiation level.
The FANC undertook analysis in order to define the localisation of the package and of the people during the transport, as well as the dose rates they could have been exposed to. Because one cannot conclusively say where exactly the package was stored in the airplane's cargo space, the FANC based its analysis on the most conservative calculations, taking into account all possible storage positions.
The results showed that the maximum dose a passenger sitting ‘right on top' of the package could have been exposed to, is 6,6 mSv for the plane Cairo-Brussels, and 3,1 mSv for the plane Zürich-Brussels. The dose limit for public exposure is 1mSv per year in the knowledge that one person living in Belgium is exposed, on average, to about 2,8 mSv per year due to natural radiation. For your reference, the average dose of a CT scan of the abdomen is 8 mSv. A single exposure such as the one faced during this incident does not represent a significant increase of the health risk for the people exposed. There is however no risk of radioactive contamination for these people, and they are not radioactive themselves.
The FANC informed the shipment expeditor and the various involved nuclear authorities of the incident and the non-compliance with the nuclear materials transportation regulations. These authorities will now jointly monitor the incident and take the necessary measures in order to prevent this type of incident from reoccurring.
After analysing the incident, it is provisionally rated as a level 2 incident on the INES-scale (International Nuclear Event Scale). The INES scale is a tool for promptly and consistently communicating to the public the severity of events associated with ionizing radiation. Events are rated at seven levels, ranging from 1 (anomaly) to 7 (major accident).
28 Juli 2017