Band 74, Heft 4

Handling open radioactive substances requires extensive precautionary measures in order to avoid any danger. During the past 100 years many persons were injured or killed due to unintended external irradiation, contamination of the skin or uptake of radioactive substances. With the help of organisational measures with users of sources and with operators of radionuclide laboratories or nuclear installations numerous accidents can be avoided or their consequences can be mitigated. Also the government itself is challenged in order to register and secure radioactive sources and maintaining the national safeguard. Education of personnel handling radioactive substances plays an important role when it comes to precautionary measures. In combination with suitable technical equipment it is possible to obtain a high degree of protection against the hazard from negligent or wilful contamination.

In 2007 the Swiss Federal Commission for NRBC Protection released a disaster management plan for coping with the aftermath of radiological dispersal devices. This paper summarises the basic concept and outlines the relevant bodies and agencies as well as their responsibilities. It also sets out the strategy to monitor radioactive contamination and the measures to prevent public radiation exposure.

In case of a terrorist's threat to release nuclear or radioactive material methods and procedures are needed for fast search and, after detection, identification of the substance. For searching the German Fraunhofer-INT in Euskirchen has a car at its disposal, which is equipped with very sensitive detectors suitable for a first identification of the material. Advanced measurements are performed with portable detectors of high energy resolution or by scanning of buildings or objects with a gamma camera. Initially such material may be stored under water in preparation for an attack. In this case we have a special sensor available for detection and subsequent identification. In case of no suspicious material being detected with all these passive methods, even though a well-founded suspicion exists, active methods will be employed. Therefore neutron interrogation is briefly presented. With all these techniques it is possible to determine the presence of radioactive or fissionable materials, as well as, within certain limits, type and quantity of material. Hence information will be gained on the possible risk potential and, by actions taking radiological aspects into account, recommendations can be given on further actions to be taken.

By routine examinations of a radiation worker, a contamination incident with transuranium nuclides was discovered. Immediate investigations showed a serious degree of the incident. First countermeasures were done to narrow the effects down and to avoid a spread of contamination. A complex decontamination followed for which the radiation protection infrastructure had to be built up.

Incidents and accidents occurring in nuclear facilities, transport accidents or malevolent actions associated with radioactive material may involve a release of airborne radionuclides. For these situations, a realistic assessment of the radiological consequences for the public is of great importance with respect to adequate emergency measures. Within this context, the determination of the spatial distribution of the resulting airborne concentration as well as of the deposition of radionuclides on the ground, vegetation and building surfaces are necessary prerequisites. For such calculations, advanced atmospheric dispersion models are increasingly used. Their characteristics and fields of application are presented.

The mysterious death of the former secret service agent Alexander Litvinenko on 23 November 2006 suddenly attracted the attention of the public to the rather unknown radionuclide 210 Po. In this respect, this paper presents some general background information about this radionuclide as well as some details about its biokinetic behaviour and internal dosimetry. The results are discussed in the context of the Litvinenko case with regard to possible health effects on people from Germany being potentially contaminated. However, no evidence for contamination with 210 Po could be found for any people tested at the GSF-National Research Center for Environment and Health (since 01.01.2008 Helmholtz Zentrum München).

The dead of Alexander Litvinenko in London in the late 2006 was linked with the visit of Dimitri Kovtun. So an investigation was started by the Hamburg Police. As the presence of polonium-210 was uncertain, the action was supported by the Federal Defense against Nuclear Hazards (NGA) of the Federal Office for Radiation Protection (BfS). Radiation measurements in some flats in Hamburg confirmed the suspicion of polonium-210 contaminations. As incorporations by ingestion or inhalation could not generally be excluded, the Coordinating Office on Incorporation Monitoring of the BfS (Leitstelle Inkorporationsüberwachung des BfS) was requested to clarify this issue. The BfS office then coordinated the required bioassay analyses of urine samples carried out at four officially appointed in-vitro laboratories for incorporation monitoring. The group of people to be examined included the members of the family involved living in the contaminated flats, the emergency forces, as well as potentially exposed members of the public. The calculation of the internal dose was based on standard assumptions and also conducted by the BfS. The internal radiation doses proved to be within the range of radiation doses due to natural exposures. Retrospectively it should be stressed that the collaboration and cooperation of all institutions involved in the operation in Hamburg was extremely good despite their differing organisational structures. As a result of the incident in Hamburg various middle and long-term measures have been taken since then by the BfS Coordinating Office on Incorporation Monitoring.

During the Chernobyl accident it became evident that there was no up to date information of the radiological situation in Bavaria as a whole. Therefore an online measuring network was implemented, which provides radioactivity data around the clock from all over Bavaria. It comprises measuring devices for gamma-dose rate, airborne aerosol and iodine activity and precipitation. The data are processed in accessory computers and transferred to the main network computers in Augsburg by means of a subcenter computer at the site of the IfR-station. Alarm levels are low in order to have an early warning against airborne radioactivity. New techniques for remote maintenance of the measuring devices and nuclide identification are being planned and tested.

In the early phase of a nuclear emergency many decisions have to be made by the authorities. So it is of great support when certain measures run automatically. Additional mobile gamma probes are therefore picked up by the local fire brigade at the nuclear power plant without further ado by the authorities. The gamma probes are then positioned at sites which are calculated automatically, taking into account the momentary weather situation. The sites are printed on a map handed over to the firemen. A location of a standby area after having set up the gamma probes is also given on this map.

Off-site nuclear emergency response in Germany is divided into disaster response under the responsibility of the Länder and measures for precautionary radiation protection pursuant to the Precautionary Radiation Protection Act under the lead of federal authorities. Early countermeasures at the regional level require a different management than long-term and comprehensive actions of precautionary radiation protection. As situations may arise in which measures of both approaches overlap with regard to place and time, it is essential to make thorough preparations in order to avoid problems with implementation.

The nuclear reactor remote monitoring system of the state of Baden-Württemberg (Kernreaktor-Fernüberwachung Baden-Württemberg – KFÜ BW) is implemented according to the recently renewed “recommendations for remote monitoring of nuclear power plants”. In Baden-Württemberg, the application area of the system covers both, the surveillance of internal procedures on one hand, and the handling of incidents or accidents on the other. The following paper shows the role of the KFÜ regarding the determination and evaluation of the radiological situation in the range of off-site emergency response. Progress is reported on the measurement conception and the technical possibilities for the investigation of the radiological situation after the end of the deposition of radio nuclides (ground phase).

Kurzfassung Es werden Erfahrungen aus einer Gefahrstoff-Übung, insbesondere aus einer Lage mit radioaktiven Stoffen (Messungen und Probennahmen) geschildert. Hierbei kamen verschiedene Spezialfahrzeuge mit Beladung und der ihrer Besatzung zum Einsatz. Ebenso waren die nach Landeskonzept notwendigen Strahlenschutzfachkräfte eingebunden. Es war die bislang größte Übung in Hessen, die zum Komplex „Gefahrgut“, insbesondere auch im Hinblick auf „Zwischenfall mit radioaktiven Stoffen“ in dieser Art stattfand.