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Ionising Radiation > ... > Safety of sealed radioactive sources
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Safety of sealed radioactive sources in Germany
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Figure 1: Blood irradiator
(Source: Identification of Sources and Devices - Reference Manual, IAEA Nuclear Security Series, 2007)
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About 100.000 sealed radioactive sources are used in Germany in industry, medicine, research and in agriculture.
Areas of use and legal prerequisites
The most common areas of use for sealed sources in industry lie in the fields of calibration, material testing, product irradiation and sterilisation as well as fill level and density measurement. Sealed sources in medicine are primarily used in radiation therapy and blood irradiation. The most commonly used radionuclides in these sources are cobalt-60, iridium-192, caesium-137, strontium-90 or and americium-241. The applied activities range from some kilobecquerel for testing and calibration sources to several Terabecquerel in radioactive sources for irradiation facilities.
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Figure 2: Gamma radiography projector
(Source: Identification of Sources and Devices - Reference Manual, IAEA Nuclear Security Series, 2007)
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The use of radioactive sources in Germany is, in principle, subject to government supervision (according to the Atomic Energy Act) and requires a licence (according to the Radiation Protection Ordinance). The licence is granted by the respective federal state authority in Germany after examination of legally required prerequisites. The use of sealed sources without any authority control applies only to sources, that contain a level of activity, below the so-called exemption level, or sources which are fixed within equipment built to a type approved design. The exemption levels concur with international (IAEA) and European values (EU Guideline 96/29/EURATOM). The exemption level represents an amount of radioactive material, that - if properly handled - is associated with a small amount of danger only.
Owners' duties and regulatory control
The receipt and transfer of sources is subject to governmental licensing requirement, too. The correct handling during the application of radioactive sources is monitored by an authorised government-appointed radiation protection officer. In addition, the licensee may be at any time, subject to controls by the regulatory authority, which they feel are necessary. Safety-related incidents during the use of sealed sources, such as technical malfunctions of the device, operating error or theft, must be reported immediately to the responsible authority. When transferring a source, it must be guaranteed that the recipient has a valid licence for the use of sealed sources. Furthermore, the recipient must receive a certificate, stating that the source is leak-tight and free from contamination.
The transfer of a radioactive source is subject to the Transport of Hazardous Goods Ordinance and also requires authorisation. The carriage without governmental monitoring is permitted only for levels of activity below the exemption level (see above) and for the so-called exempted packages. The transport packaging of radioactive sources must comply with the provisions of the European Agreement concerning the International Carriage of Dangerous Goods by Road (ADR).
The working life of the applied sources varies greatly, in particular due to the strongly varying half-life of the used radionuclides. If sources are not disposed of directly by the licensee, the equipment together with the source remaining in the device must be returned to the equipment manufacturer after completion of use. The manufacturer checks if the radioactive source is reusable or returns it to the source manufacturer. Disused sources or devices are delivered to Federal state collecting facilities.
No danger so far in Germany from radiation sources which were lost or illegally disposed of
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Figure 3: Radioactive source from a teletherapy unit, found at the accident in Thailand
(Source: The Radiological Accident in Samut Prakarn, IAEA, 2002)
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Despite of the governmental controls for the use of radioactive sources, it cannot be excluded that a sealed source gets lost or that an orphaned source will be found. These incidents must be immediately reported to the regulatory authority. All incidents will be recorded and analysed at a national level. A brief summary about the annual incidents in Germany is published in the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety’s annual report "Environmental Radioactivity and Radiation Exposure".
Between 1991 and 2008 countrywide 489 incidents concerning the loss or discovery of radioactive sources were recorded. These sources were disposed of mostly illegally or ignorantly and were often discovered in junk or waste containers afterwards, because most of the scrap metal or waste companies employ appropriate radiation measurement devices. The level of radioactivity in these lost or found sources is in most cases low (e.g. unwittingly discarded ionising smoke detectors).
Central register allows traceability of high-activity sealed radioactive sources
However, between 1991 and 2008, eleven findings of sealed sources with a high level of activity, that could already pose a great danger, were reported, but did not end up in accidents. Dangers associated with sources of this kind, were seen in an incident in Thailand in the year 2000, in which a cobalt-60 source from a teletherapy device was accidentally taken to a junk yard and unknowingly opened. Significant radiation exposure resulted from this opening, which resulted in several people suffering from radiation sickness or dying. This example emphasises the danger posed by radioactive sources when orphaned as a result of lacking monitoring. So far, no accidents of this kind have occurred in Germany.
Against the background of possible accidents, measures to increase safety when dealing with radioactive sources have been discussed on the level of the International Atomic Energy Agency (IAEA) since the 1990s. Especially in view of the altered level of safety after the attack on September 11, 2001, international regulations have tightened significantly.
In Germany, specific regulations were enacted by law concerning so-called high-activity sealed radioactive sources (HASS) in 2005. Those are sealed sources, which have such high levels of activity that improper handling is associated with extreme danger. In addition to existing regulations, since 2005 delivery and acquisition of a HASS have to be recorded in a central register (HRQ-register) at the Federal Office for Radiation Protection (BfS). The HRQ-register allows traceability of all high-activity sealed radioactive sources in Germany. The new regulations integrated the obligation to take back a HASS by the manufacturer of the source into law, too.
International information system on lost radioactive sources
Because the problem of transfer of radioactive material through global scrap trade is trans-national, the IAEA is operating an information system to transmit data on lost radioactive sources on a global scale. Not least because of this information system, a case was solved in 2003 involving two sealed sources found in scrap metal in Germany. The radioactive sources had been stolen in their original country Nigeria and had reached Europe through different routes. In order to avoid such incidents and to minimise their consequences, the improvement of existing security measures is planned for the future.
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