Propagation simulations of radionuclides emitted by the nuclear accident in Fukushima, Japan
Prior last updated: 29/04/2011
After the accession of the Federal Republic of Nuclear Test Ban Treaty in 1996, the Federal Institute for Geosciences and Natural Resources (BGR) has been with the operation of the national data center (NDC) in charge. In this function, the BGR evaluates, among other things, in cooperation with the Federal Office for Radiation Protection (BfS) from the data of the single global network for the measurement of radionuclides to detect possible clandestine nuclear weapons tests. This network of stations for measurements of radioisotopes, together with seismic, hydroacoustic and infrasound stations part of the International Monitoring System (IMS) of the Comprehensive Nuclear Test Ban Organization (CTBTO) in Vienna. Combined BGR for finding the location of clandestine nuclear tests backward calculations for the transport of radioactive materials in the atmosphere with waveform methods such as seismology. This expertise BGR now also benefits the assessment of the consequences of the nuclear accident in Japan: The transportation bill in a forward simulation is used to predict the global spread of radioactive substances and their arrival at the IMS stations. Worldwide, 63 of these stations in operation, the German station is operated by BfS on the Schauinsland mountain near Freiburg. Overall, the BGR has obtained from measurements and by calculations that released by the reactor accident in Fukushima radioactive cloud Europe has reached extremely diluted. The measurements at each station and calculations show that the cloud already on March 16, California has already achieved a very diluted and has been replicated over Iceland and Scandinavia the way to Europe. On Sunday, March 20, the station has proven to Iceland first, but extremely low concentrations. Meanwhile radionuclides from Fukushima were also at the stations Stockholm, Spitsbergen, in the Azores and in Europe at Schauinsland detected.
Simulation of the dispersion of particles in the atmosphere:
The following animation shows the atmospheric dispersion modeling the location of the Fukushima nuclear power plant until 28 March 12 UTC for a constant release of 1 / hour of cesium-137 over a period of 240 hours from the 12th-22nd September 2011, 3 per UTC. A constant emission was assumed because of the current over the time course of the release and the source strength no exact knowledge. Therefore, the information on the specific relative concentrations are to be used only for qualitative statements. However, they give an impression of the propagation of particles in the troposphere under the prevailing meteorological conditions in the northern hemisphere primarily in eastern direction. Furthermore, they provide guidance regarding the arrival times of radio-isotopes to the IMS stations. The results were compared with the model HYSPLIT, the NOAA ( National Oceanic and Atmospheric Administration , achieved) is made freely available. The meteorological data comes from NCEP ( National Center for Environmental Prediction ) with a horizontal resolution of 0.5 °. In addition to the analysis of data that have found application deadline is March 24, and forecast data from the GFS (were Global Forecast System ) as of March 28, with the bill. The dispersion modeling was carried out at 45 altitude levels in the troposphere and is shown averaged for the heights between 0 and 0.5 km and 2.0 and 5.0 hours by car you. This corresponds to a slower transport near the earth's surface or faster - unaffected by soil friction - in the middle Troposphäre.Es it should be noted at this point that the vertical transport in the model is given not necessarily correct. It's on a date not clear to what extent particles were emitted. On the other factors at the measuring stations as the local temperature stratification and topography are crucial in determining whether vertical mixing between higher layers, which takes place on the long-range transport, and ground-level air is possible.
0 to 0.5 miles:
Animated representation of the spread of the particle cloud from Fukushima made in the northern hemisphere, averaged over height interval 0 km to 0.5 km away. The locations of the IMS radionuclide are shown in red. Source: BGR 2,0 - 5,0 miles:
Animated representation of the spread of the particle cloud from Fukushima made in the northern hemisphere, averaged over height interval of 2.0 km to 5.0 km. The locations of the IMS radionuclide are shown in red Source: BGR Detectability of the IMS stations:
The following figure shows the simulated relative concentrations and their arrival times at the stations of the IMS for radioisotopes from 12 to 28 March. The comparison with the measured data shows that the arrivals are made well in most cases. The differences can possibly be explained by a variation of the release height. It is reasonable to assume that particles and fission gases were hurled into higher layers in the explosions. Since Sunday, 20 March, the station measures to Iceland smallest traces of iodine 131st Since the 24th / 25th March also measures operated by the Federal Office for Radiation Protection radionuclide station at Schauinsland in Freiburg im Breisgau low activity concentrations of iodine and tellurium and the noble gas isotope Xe. 133 It is not assumed that the concentrations in Europe are still westentlich change in the next few days.
Model results of the simulated temporal concentration profile at the IMS radionuclide. On the X-axis, the days of the month of March are ready Source: BGR The following stations have been actually able to prove radionuclides. The outside of Japan measured with extremely sensitive systems of IMS activity concentrations are very small and are partially in the area of the detection threshold. The simulated time of arrival can not be accurately evaluated mostly because the IMS radionuclide particles measured in a three-day rhythm: Plants absorb for 24 hours air through a filter, then the sample sounds 24 hours from order to reduce the background by short-lived isotopes and a further 24 hours in a gamma spectrometer identified and counted the energy of the decay. The results are thus present always only two to three days after the measurement. Within this accuracy, however, the modeled arrival times were usually bestätigt.Berücksichtigt here are detections up to 25.3.2011.
| Station | Position | First detection [day / month (UTC)] |
|---|---|---|
| RUP60 | 53.1 ° N / 158.8 ° E | 14/03 |
| JPP38 | 36.3 ° N / 139.1 ° E | 15/03 |
| USP70 | 38.7 ° N / 121.4 ° W | 16/03 |
| USP71 | 55.2 ° N / 160.5 ° W | 18/03 |
| USP74 | 37.2 ° N / 99.8 ° W | 18/03 |
| CAP14 | 49.3 ° N / 132.2 ° W | 18/03 |
| CAP17 | 47.6 ° N / 52.7 ° W | 19/03 |
| USP75 | 38.0 ° N / 78.4 ° W | 19/03 |
| USP79 | 21.5 ° N / 158 ° W | 19/03 |
| USP72 | 28.3 ° N / 80.6 ° W | 20/03 |
| USP76 | 64.7 ° N / 147.1 ° W | 20/03 |
| ISP34 | 64.1 ° N / 21.9 ° W | 20/03 |
| USP77 | 19.3 ° N / 166.6 ° E | 20/03 |
| USP80 | 13.6 ° N / 145.0 ° E | 21/03 |
| USP78 | 28.2 ° N / 177.4 ° W | 21/03 |
| CAP15 | 74.7 ° N / 94.9 ° W | 21/03 |
| RUP58 | 44.2 ° N / 132.0 ° E | 22/03 |
| SEP63 | 59.2 ° N / 17.6 ° E | 22/03 |
| CAP16 | 62.5 ° N / 114.5 ° W | 22/03 |
| PHP52 | 14.6 ° N / 121.4 ° E | 22/03 |
| RUP61 | 56.7 ° N / 37.3 ° E | 22/03 |
| RUP54 | 58.6 ° N / 49.4 ° E | 22/03 |
| PTP53 | 37.8 ° N / 25.8 ° W | 23/03 |
| FRP28 | 16.3 ° N / 61.5 ° W | 23/03 |
| NOP49 | 78.2 ° N / 15.4 ° E | 23/03 |
| DEP33 | 47.9 ° N / 7.9 ° E | 24/03 |
| PAP50 | 8.9 ° N / 79.6 ° W | 23/03 |
| JPP37 | 26.5 ° N / 127.9 ° E | 24/03 |
| KWP40 | 29.3 ° N / 47.9 ° E | 25/03 |
| MRP43 | 18.1 ° N / 15.9 ° W | 25/03 |
| KIP39 | 2.0 ° N / 177.4 ° W | 26/03 |
| RUP59 | 53.9 ° N / 84.8 ° E | 26/03 |
| MNP45 | 45.5 ° N / 107.0 ° E | 26/03 |
| FRP31 | 5.2 ° N / 52.7 ° W | 29/03 |
| MYP42 | 4.5 ° N / 101.4 ° E | 30/03 |
| PGP51 | 3.0 ° S / 150.0 ° E | 30/03 |
| CMP13 | 3.5 ° N / 10.1 ° E | 02/04 |
| FJP26 | 18.0 ° S / 177.5 ° E | 05/04 |
Since the end of March, all of the IMS radionuclide in operation after the northern hemisphere traces of radionuclides from Fukushima. Something a Millibecquerel per cubic meter of air (mBq / m, the maximum of the activity concentration was due to the German radionuclide RN33 on Schauinsland on 06.April for iodine-131 3 ) and cesium-137 at less than 0.1 mBq / m 3 . However, it sparks contribution to the dose rate is negligible compared to the natural environment radioactivity. Detailed information on the results of the trace analysis of air samples, the Federal Office for Radiation Protection www.bfs.de published.
Furthermore, it appears since the end of March at the Fukushima nuclear power plant can no longer be larger release of radioisotopes to have come into the atmosphere, so that the concentrations point to the northern hemisphere a downward trend. Since the position of the spread has not changed qualitatively and the question has been answered in the arrival times of the IMS stations, therefore no further simulations were created by BGR.
An interesting from a scientific perspective aspect is the exchange across the equator between northern and southern hemispheres; from the experience of previous above-ground nuclear weapons tests from the 50s and 60s of the last century, a period of about four weeks is expected. So while mixing over the northern hemisphere is largely done first fine traces have been measured since the beginning of April in each radionuclide in the southern hemisphere. Detections reported by the Fiji Islands, Papua New Guinea, Australia (Darwin) and Brazil (Rio de Janeiro). This remains to be seen which way have taken the radioactive substances in order to overcome the barrier acting as active Intertropical Convergence Zone in the equatorial region.
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