Question

Answer

What is gamma dose rate (GDR)?

Gamma dose rate is the dose per time unit from gamma radiation. It is given in units of Sievert per hour (Sv/h). The radiation dose measured in a fixed location is the local ambient dose rate and commonly abbreviated by the acronym GDR.

Since the reactor accident in Japan I have been checking regularly the readings from a particular measuring station nearby. For a short time this station was not available on the GDR measurement network map of Germany. What had happened?

Stations are not listed on the map if they provide corrupted readings or if they are out of order. In the station list, however, they are still listed with a corresponding status, e.g. unavailable or out of order. If the measuring station had to be removed for whatever reason, it neither appears on the map nor in the station list. As soon as possible a new location will then be found nearby in order to close the gap in the measurement network again. This can be a different municipality with different name.

The BfS gives the name of the municipality. Can I also get the exact coordinates?

Many stations are on private property, (e.g. schools and kindergardens) some are in restricted areas. The Federal Office for Radiation Protection is authorized to use the property free of charge for measuring the gamma dose rate. In order to protect the owner's privacy the exact location is not given.

At what level is the gamma dose rate in Germany and what part is the contribution from the reactor accidents in Chernobyl and Fukushima?

In Germany, the natural gamma dose rate is between 0.05 micro Sievert per hour (μSv/h) measured at some stations in Schleswig-Holstein and Lower Saxony and up to 0.2 μSv/h in parts of Thuringia, Baden-Württemberg and Bavaria. The mean gamma dose rate in Germany is approximately 0.08 μSv/h. In case of heavy rain the readings may double for a short period of time (see also Information).
The additional gamma dose rate due to the reactor accident in Chernobyl is today approximately 0.001 μSv/h in Germany. Levels between 0.01 and 0.02 μSv/h are still measured in small areas of Bavaria particularly affected by the Chernobyl fallout. An increase of the gamma dose rate due to the accident in Fukushima could not be detected in Germany.

What is the meaning of the treshold value in the time series plots and why do the treshold show large changes at some stations?

The threshold is on average about 0.02 micro Sievert per hour above the average of the dose rate. He will be checked manually at regular intervals. If changes of more than 0.01 micro Sievert per hour occur, the threshold is adjusted. This leads to the jumps in time series. If a measured value exceeds the threshold value, this value is automatically marked with a status of "to be checked". All measured values with the state "to be checked" are inspected on a daily basis from the specialists of the Federal Office for Radiation Protection. Thus, a measurement station that shows conspicuous values can quickly located and the probe that may have a technical problem can be exchanged very fast.

I have purchased a radioactivity measuring device. This device shows other values than those published at http://odlinfo.bfs.de. The manufacturer claims that the measuring device underwent a final check and was calibrated with a Caesium-137 standard. How can the different measurement results be explained?

If comparing ambient dose rate readings, the location, the height above ground and the time of measurement have to be considered. Inhomogeneous concentrations of natural radioactivity in soil or building materials can make the dose rate readings different even at a few meters distance.

Furthermore, the type of calibration needs to be taken into account: It can either refer to the photon-dose equivalent (Hx) or to the ambient dose H*(10). The latter includes a biological evaluation factor and is the stipulated dose unit for environmental radioactivity. Another problem is the natural cosmic radiation. It contributes with about 0.03 micro Sievert per hour at sea level but may be heavily under- or overestimated because dose rate meters are not calibrated for this type of high energy radiation. In general, it should be noted that dose rate meters are calibrated for a large range of values and normal environmental measurements are at the very bottom of this scale where such differences become visible. They become less important or disappear for elevated levels of gamma radiation.

When I look at the measuring station distribution on the map I can see more probes in the western part of Germany than in the eastern part. What is the explanation?

The measurement network is comprised of a basic grid that homogeneously covers Germany. The mean distance between stations is between 30 and 40 kilometres. Within a radius of 100 km around nuclear reactors the network is denser with a mean distance of about 20 km between stations. Additional 12 stations are installed in each sector of the 25 km emergency planning zones. As all German nuclear reactors are located in the "old" federal states, the monitoring density is higher in western part of Germany.

There are some measuring stations, for example the "Kiel Lighthouse", where many failures can be observed in the daily mean values. What is the reason?

At very exposed locations it is possible that the wind causes the probe to vibrate. The sensitive Geiger-Müller tubes in the probes may then be triggered to produce additional impulses which are wrongly interpreted as gamma counts (see text on wind effect in menu item Information). When the data is validated by BfS experts, these values are marked as implausible. They are not reported in the time series. The BfS is reducing this effect to the best possible extent using reinforced standpipes. The "Kiel Lighthouse" site that has been taken as an example, however, is an about 40 meter high aluminium tower which starts to vibrate easily. In this case there is no remedy available. Various other reasons, for example maintenance, reconstruction works at the site, faulty data loggers, malfunctioning probes and regular QA with a radioactive check source, may also explain data gaps.

The gamma dose rate continuously increased in March/April 2011. What was the reason for this?

The natural dose rate is composed of the radiation from the ground (terrestrial component) and the radiation from space (cosmic component). If large quantities of snow lie on the ground surrounding a GDR probe, the terrestrial component is shielded and the measured gamma dose rate decreases. With the onset of thawing in spring the dose rate increases and returns to the level of the previous year when the snow cover has disappeared (see also menu item Information). Emergency response, the function of the measurement network deals with the artificial component, possibly released by a nuclear accident.

What do you exactly do when you validate the GDR data? Does the BfS censor the measured data?

The Federal Office for Radiation Protection does not censor data. All data are stored as raw data and reviewed in order to identify technical problems and to assure that no data is published that is compromised by technical faults (see also menu item Information). Implausible data is marked but never deleted or changed.

Can I get access to the GDR map of Germany showing data from past days?

The map is generated on a daily basis and replaces the former day issue. A map archive does not exist.

Is it possible to get current measurements from the BfS, e.g. as CSV-file? Does a data archive exist where I can download historical data from your server?

The BfS compiles GDR values of operative measuring stations on a daily basis. The data is available in ASCII format as "Comma Separated Values" (CSV file) on the odlinfo server and contains 1-hour mean values. To get access to this data, please refer to the BfS using the menu item Contact. It is also possible to download historical gamma dose rate data as daily mean values from every operative station from the download section.

Is it possible to represent the seasonal changes of the GDR in Germany over the time?

An animated gif image generated from the daily mean values of all operational gamma dose rate probes is available here as an example. The animation shows the changes in the gamma dose rate over one year (from 30. July 2010 to 25. July 2011) in Germany. In particular, snow-covered areas decreasing in Winter and increasing in Spring with snow melting can be seen here. Furthermore larger rain events can be recognised, leading to local increases of the GDR. To watch the animation please click here.

The time axis of the 1-hour GDR mean values charts at http://odlinfo.bfs.de is given in UTC. What does that mean?

The data in the GDR measurement network is generally collected on the basis of UTC time (Universal Time Coordinated), in order to make the data exchange with other international organisations easier and to avoid ambiguous time values when switching to and from daylight saving time.

Will radioactive substances from to the accidents in Fukushima, Japan, be detectable in the readings of the German dose rate network?

Single traces of radiators from the reactor in Japan have also been detected in Germany by aerosol samplers of the CTBTO measurement network (Comprehensive Nuclear-Test-Ban Treaty Organization). Only trace-analysis and air-monitoring systems were sensitive enough to measure those small concentrations of radioactive substances that were transported to Europe. They added only an very small fraction to the normal radiation measured in Germany. The activity was of the order of few millibecquerel per cubic meter air (1 Becquerel equals one decay per second). The probes of the GDR measurement network, although being highly sensitive, cannot detect these low values. Therefore, no increase due to the accident in Japan could be reported by the German GDR network.

Are there other networks in Germany and Europe that measure gamma dose rate?

In Germany, the federal states operate nuclear power plant monitoring systems (Kernreaktorfernüberwachung KFÜ) in the surroundings of their nuclear facilities. These networks are paid by the plant operators. The KFÜ data is published elsewhere on web sites operated by the federal states. The data from the BfS stations near the nuclear facilities are exchanged with KFÜ and vice versa.
All European countries operate environmental radioactivity monitoring networks. Article 35 of the EURATOM Treaty provides for continuous monitoring of radioactivity in soil, air and water. Data is reported to the central EU data base (EURDEP, EUropean Radiological Data Exchange Platform) at Ispra, Italy. The BfS operates the data backup server of the EURDEP data base. The data can be publicly accessed through the EURDEP web-site: http://eurdep.jrc.ec.europa.eu

Who is responsible for the monitoring of air and water in terms of radioactivity in Germany?

Responsibility for monitoring radioactivity in the environment is shared between the federal government and the states (Länder). BfS operates a nation wide network of approximately 1.800 fixed stations monitoring ambient dose rate and six vehicles measuring nuclide specific soil contamination. In the North and Baltic Seas, the Federal Maritime and Hydrographic Agency (Bundesamt für Seeschifffahrt und Hydrographie) operates the MARNET measurement network comprised of ten stations. Domestic waterways are monitored by the Federal Institute of Hydrology (Bundesanstalt für Gewässerkunde) with 40 stations. At 48 stations, the German Weather Service (Deutscher Wetterdienst) is monitoring air with on-line filter systems and measuring rain water in radio-chemical laboratories. The laboratories of the federal states monitor continuously food, animal feed, drinking water and soil. All these monitoring networks and laboratories are part of the "Integrated Measurement and Information System for the Monitoring of Environmental Radioactivity" (IMIS). In case of a nuclear accident these systems provide the data for decisions and recommendations to protect man and environment against radioactiviy.