Volume 72, Issue 4

The monitoring program for measurements in intense operation mode has been revised recently by a working group at the Federal Ministry for Environment, Nature Conservation and Reactor Safety (BMU). The major issues of the revision are reported in this contribution. Measurements in intense operation must be appropriate for fast assessment of the radiological situation, for estimating the dose to the population and for decisions on countermeasures to minimize the dose. In order to meet these requirements the structure of the measurement program in intense operation mode was divided into three phases when different exposition paths are relevant: before and during dispersion of radioactive material, immediately after dispersion of radioactive material has ended and a late phase when contamination values have decreased in different environmental media. For each of these phases a special measurement program was defined that is tailored to achieve the above mentioned objectives. Minimum detectable activity concentrations were introduced similar to the measurement program in routine operation mode. They follow the intervention levels in the catalogue of countermeasures and maximum permitted values given by the European Union (EU) for food and animal feed. The minimum detectable activity concentrations were defined such that the detection of 1/10 of the intervention levels for countermeasures is ensured.

Based on results of the numerical weather forecast models; the DWD (Deutscher Wetterdienst, German Meteorological Service) is immediately able to calculate dispersion forecasts in the case of an emergency with an emission of radioactive inventory. This information is essential for the management of further countermeasures. There are legal agreements between the federal states of Germany and the Federal Government regulating the mutual aid. For the emergency preparedness system RODOS (Real Time Online Decision Support) the results of the numerical weather forecasts are provided and complemented by medium-range dispersion forecasts. In the framework of the German computer network IMIS (Integrated Measurement and Information System for the Surveillance of Radioactivity in the Environment) the results of trajectory calculations are presented graphically within 10 minutes, those from the LPDM (Lagrangian Particle Dispersion Model) forecasts within 30 minutes. In case of a nuclear emergency, global distribution of information via the WMO (World Meteorological Organization) communication system GTS is part of international agreements between IAEA (International Atomic Energy Agency) and WMO, thus giving the DWD a key role. The commitments of the DWD in managing nuclear emergencies in the framework of national and international agreements are presented, as well as internal emergency arrangements.

The DSSNET network was established in October 2000 with the overall objective to create an effective and accepted framework for better communication and understanding between the community of institutions involved in operational off-site emergency management and the many and diverse Research and Technological Development (RTD) institutes further developing methods and tools in this area, in particular decision support systems (DSS), for making well informed and consistent judgements with respect to practical improvements of emergency response in Europe. 37 institutions from 21 countries of East and West Europe have been members of the network with about half of them responsible for operational emergency management. To stimulate the communication and feedback between the operational and the RTD community, problem-oriented emergency exercises were performed, which covered the various time phases of an accident and which extended from the near range to farther distances with frontier crossing transport of radionuclides. This paper concentrates on the five emergency exercises conducted in the frame of the project.

The 5-year multi-national project EURANOS, funded by the European Commission and 23 European Member States, started in April 2004. Integrating 17 national emergency management organisations with 33 research institutes, it brings together best practice, knowledge and technology to enhance the preparedness for Europe's response to any radiation emergency and long-term contamination. Key objectives of the project are to collate information on the likely effectiveness and consequences of a wide range of countermeasures, to provide guidance to emergency management organisations and decision makers on the establishment of an appropriate response strategy and to further enhance advanced decision support systems, in particular, RODOS (Real-time On-line Decision Support), through feedback from their operational use. The research activities focused on emergency actions and countermeasures, the enhancement of decision support systems for operational application and the development of strategies for the sustainable rehabilitation of contaminated territories. The demonstration activities exercise the developed methods and tools in the actual operational environment.

Communication and exchange of accident information and monitoring data during nuclear emergencies is of crucial importance for a coherent crisis management, especially in cross border regions. In Germany and the Netherlands the need for a reliable information and data exchange for cross border emergency management was recognized and resulted in a Memorandum of Understanding between our countries. A (sub) working group of the Niederländisch-Deutsche Kommission für grenznahe kerntechnische Einrichtungen (NDKK) was formed by NLWKN, BfS and RIVM. The working group reviewed the technical requirements and operational aspects of a coherent data and information exchange between national and federal emergency centers and the state authorities. The data exchange comprises various messages, documents, measurement data and prognostic results from model calculations from the technical decision support centers of NLWKN, BfS and RIVM. Integrated accident information is available on the emergency management websites ELAN (D) and CalWeb (NL). Via regular data exchange programs and exercises special attention is given to ensure long term sustainability of the technical infrastructure and operational data exchange procedures.

According to the Austrian Radiation Protection Act, decision support systems have to be implemented and operated in Austria. Recommendations on early counter measures in case of a radiological emergency are based on the results of these decision support systems and on measurements of the environmental monitoring. The following article gives an overview on the different decision support systems operated in Austria and first experiences gained through their application in international exercises and projects.

The reliability of the evaluation of the radiological situation in the pre-release phase of a nuclear accident strongly depends on the quality of the source term estimation. Input data for the decision support system RODOS, such as time, composition, extent, and duration of a possible release of radioactive substances (source term) serve as a basis for the assessment of possible radiological consequences in the vicinity of a plant. With the collaboration of BfS and GRS a source term estimation tool was tested at a reference plant in order to provide data for RODOS.

Any dose rate instrument used to monitor environmental radiation must be characterized with respect to its response to secondary cosmic radiation and terrestrial radiation. This requires calibrations using different photon radiation fields, the measurement of the instruments internal background and the exposure to secondary cosmic radiation. The methods developed within the cooperation between BfS and PTB are explained in detail by an intercomparison of instruments which are part of the German early warning network IMIS and a high-pressure ionization chamber which was used as the reference instrument. The measurements were performed at the PTB facilities for the dosimetry of environmental radiation. It is shown how the ambient dose equivalent rate of the terrestrial radiation is determined and how the sensitivity of an instrument to a radioactive cloud passing by can be investigated.

The fission yield, the transfer factors in the food chain and the dose coefficient are large for the nuclear fission product Sr-90. The surveillance of Sr-90 in the food chain is therefore important in precautionary radiation protection and in assessing the radiation dose to the public especially after a nuclear incident. Prior to analysis, as it is a pure β-emitter, Sr must be separated from the sample by procedures which, for complex organic samples, are lengthy, laborious and dependent on operator skill. Ubiquitous natural radionuclides and short-lived fission products in samples contaminated with fresh fallout may interfere. Here we describe a fast, reproducible and effficient method for extracting Sr from grass, clover, maize, wholemeal rye, baby food, and total diet. The method depends on obtaining an ash free of traces of organic interferences. Sr may be separated from a dilute nitric acid leachate of such ash with a solution of dicyclohexyl-18-crown-6 in chloroform. Interfering radionuclides are removed with a special manganese (IV) oxide (active, precipitated from Merck). Sr is precipitated as carbonate then dispersed in a cocktail for liquid scintillation spectrometry. This allows simultaneous counting of Sr-89 (a short-lived β-emitter in fresh fallout) and Sr-90. The chemical yields of Sr determined with the gamma-emitting Sr-85 tracer are reproducible and greater than 75 % in all cases. The sample ashing requires 18 h and the extraction 4.0 to 4.5 h. Thus, a duplicate analysis may be completed within 2 days of receipt of the sample.

In the context of radioactivity monitoring in German Federal Waterways (BWStr) by the Federal Institute of Hydrology (BfG) according to the Precautionary Radiation Protection Act (StrVG), the prediction of the dispersion of radioactive substances in water is one of the key tasks. The aim is the forecasting of the longitudinal dispersion of concentrations of soluble hazardous substances in flowing water. These predictions are based on the so-called dispersion tests with tritium as a tracer that the BfG has performed since 1980. Characteristic parameters like discharge-dependent flow velocities, dispersion and elimination constants related to emission sources or selected river sections are determined. They will serve as basis for a mathematical model to forecast discharge-dependent flow velocities, expected impact times, concentration maxima, and the duration of critical increases in concentrations. In the following, the results obtained till now from three investigation campaigns on the River Weser and its source rivers Werra and Fulda are described.

In an incident, the operational control staff needs a rapid general view of the radiological situation in the vicinity of the emission source which is suitable for decision support. Because the measuring team cannot provide sufficient measurements immediately, model calculations based on the available information about the course of the accident are additionally required. Such calculations do not only serve to create an overview of the current situation but can also provide prognoses for several hours. For this purpose, a software system for environmental impact forecasting was developed at Research Centre Jülich, which calculates time-integrated doses as well as ambient gamma dose rates and activity values. The latter can be directly compared with values measured during the incident and consequently can be used to assess the model assumptions.

This article gives an overview on the conceptual design of the I nhabited A reas M onitoring M odule IAMM which will be introduced into European decision support systems for nuclear emergencies. It will improve the use of monitoring data of radioactive contamination in urban environments for decision making. IAMM converts the dated gamma dose rate (GDR) measurements from geo-referenced locations into maps of surface contamination with an enhanced spatial resolution. Depending on the availability of the monitoring data, IAMM relies on two modes of operation. If there are only a few measurements, these are taken to improve the maps from a deposition model using data assimilation. If the number of measurements is sufficient to apply spatial interpolation IAMM will rely entirely on monitoring data. Suitable geo-referenced data points will be interpreted by IAMM with respect to their detector environment using the concept of location factors. The endpoints of IAMM can be used directly for decision making or dose calculations with either simple dose models or the more refined EuRopean Model for INhabited areas (ERMIN).

Model predictions for rapid assessment and prognosis of possible radiological consequences after an accidental release of radionuclides play an important role in nuclear emergency management. Radiological measurements (e. g., dose rate measurements) can be used to improve such model predictions. This paper describes a method for combining model predictions and measurements (data assimilation) in the deposition model of the European radiological decision support system RODOS. The data assimilation approach is based on the Ensemble Kalman Filter, a Monte Carlo variant of the Kalman filter.

In the field of precautionary radiation protection and disaster response, the amount of information and the number of its sources is steadily increasing. Central compilation and instant availability of information for all involved authorities becomes more and more important. In this context the structured presentation of documents on a web server in terms of an “Electronic Situation Display” (ESD) has been established. In Germany, there are several Electronic Situation Display prototypes run by federal and state authorities for various purposes and using different technical approaches. The systems of the federal states focus on workflow management. They provide emergency log books and information on the implementation of countermeasures for disaster response authorities. The Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) tasked the Federal Office for Radiation Protection (BfS) to develop the Federal Electronic Situation Display (ELAN) that is mainly used as an information platform for decision making in case of nuclear emergencies. Documents containing radiological data or results from Decision Support Systems are almost automatically integrated into ELAN. Read and write permissions for users are managed by a concept of specific roles. The federal ESD and the systems of the federal states will be coordinated in order to achieve a better harmonisation. Interfaces for data exchange and data processing must be defined. Authorities of the federal states can use protected areas within the federal ESD where information is kept confidential for internal use before it is distributed to other states and federal authorities. In addition, key information of Electronic Situation Displays from the federal states can automatically be integrated into ELAN. Several task groups of the IAEA are working on the development and realization of a prototype for an information platform harmonising ESDs on an international level.

In case of a severe accident in one of the nuclear power plants in northern Germany consequences may reach across the borders of counties and Länder and several local and regional authorities will have responsibilities for disaster response measures. Consistent assessment of the situation and coordinated action are essential for protection of the population and task personnel as effective as possible. Disaster response managements have to come to a comprehensive assessment of the developing radiological situation at an early stage to be able to initiate appropriate protective measures. The results of a working group from several local and regional authorities from Schleswig-Holstein, Hamburg, Lower Saxony and Mecklenburg-West Pomerania on this topic will be presented here. The working group has compiled sets of data and information which are relevant in decision making for protective measures and has developed a concept for the efficient distribution of data and information to the disaster response managements and other recipients with responsibilities in emergency control.

The management of catastrophes, as natural disasters or man-made disasters, will only be effective and successful if all relevant information is available in time for decision-makers. During previous large-scale disasters it became evident that information needed for the disaster management was only partially available and that there were fundamental deficits in regard to the flow of information between federal states (“Laender”) as well as communication problems between disaster response teams in the effected regions. On this account in summer 2001 the Federal Ministry of the Interior has decided to develop the “German Emergency Preparedness Information System (deNIS)”. The aim of the enhanced version deNIS II plus is to built up a network for the civil and disaster response and to assist as an information and communication system for decision-makers of the Federal Government and the Laender Governments to better co-ordination relief and rescue teams in the event of a natural disaster or technical accident. Correspondingly the primary task of deNIS is to support the decision-making of disaster management authorities.

With its recommendation “Iodine prophylaxis following nuclear accidents” (1996) and its reports of 1997 and 2001 the German Commission on Radiological Protection (SSK) followed the recommendations of the WHO “Guidelines for iodine prophylaxis following nuclear accidents” of 1989. The intervention levels were lowered (50 mSv for children/adolescents (up to the age of 18 years) and pregnant women, 250 mSv for adults), the iodine prophylaxis was restricted to persons up to the age of 45 years and the recommended dosage of stable iodine was changed. Due to the lowered reference levels the radius of 25 km around a nuclear power plant that had been the planning radius for the distribution of iodine tablets so far was extended to 100 km. Based on these recommendations the German authorities began to set up new strategies for the provision and distribution of potassium-iodide tablets (iodine tablets). Since 2004, within the radius of 25 km the iodine tablets are pre-distributed to households and/or stored at several points in the municipality for persons up to the age of 45 years. For the new planning radius of 25 – 100 km iodine tablets are stored in 8 central stocks in Germany for children/adolescents (up to the age of 18 years) and pregnant women. A working group with representatives from federal and Länder authorities has developed a distribution strategy for the distribution out of these central stocks in the event of an accident. It describes a possibility of organising and implementing the distribution of the iodine tablets within the radius of 25 – 100 km in a nationwide standardised way.