Dose Rates in Japan
Monitoring stations in Japan generally report low ambient dose rates with the exception of areas close to the reactor site. The table below provides dose rates (in microsieverts per hour, µSv/h) at various distances from the Fukushima site. In certain cases, the direction of the monitoring location relative to the Fukushima site is provided.
The results are, in many cases, from mobile detectors and therefore may not be consistent from one measurement period to the next in terms of exact location.
Overall, the ambient dose rates in and around Japan are either remaining constant or trending slightly downwards.
| Location | April 15 | April 14 | April 13 | April 12 |
|---|---|---|---|---|
| Fukushima West-gate1 | 29 µSv/h | 29 µSv/h | 32 µSv/h | 36 µSv/h |
| 20 km distance2 Northwest direction | Not reported | Not reported | 33 µSv/h | Not reported |
| 30 km distance2 Northwest direction | Not reported | Not reported | Not reported | 16.0 µSv/h (west-southwest) |
| 30 km distance2 South direction | 1.0 - 1.3 µ Sv/h (west-southwest) | 0.8 - 1.3 µSv/h (west-southwest) | 1.1 µSv/h (west-southwest) | 1.1 µSv/h (west-southwest) |
| 60 km distance2 | 0.2 - 0.5 µSv/h | 0.3 - 0.6 µSv/h | 0.1 – 0.3 µSv/h | 0.1 – 0.3 µSv/h |
| Ibaraki, City of Mito2 120 km distance | 0.139 µSv/h | 0.139 µSv/h | 0.140 µSv/h | 0.142 µSv/h |
| 165 km distance3 | 0.13 µSv/h | 0.14 µSv/h | 0.14 µSv/h | 0.15 µSv/h |
| Port of Toyko4 | 0.1 µSv/h | 0.1 µSv/h | 0.1 µSv/h | 0.1 µSv/h |
| Location | April 11 | April 10 | April 9 | April 8 | April 7 |
|---|---|---|---|---|---|
| Fukushima West-gate1 | 36 µSv/h | 38 µSv/h | 38 µSv/h | 42 µSv/h | 46 µSv/h |
| 20 km distance2 Northwest direction | 53.5 µSv/h | 52 µSv/h | 39.6 µSv/h | 53.5 µSv/h | 58.5 µSv/h |
| 30 km distance2 Northwest direction | Not Available | 24.2 µSv/h | 24.2 µSv/h | Not Reported | 28.3 µSv/h |
| 30 km distance2 South direction | 1.2 µ Sv/h (west-southwest) | 1.6 µSv/h (west-southwest) | 0.8 – 1.3 µSv/h (west-southwest) | 1.3 µSv/h (west-southwest) | 0.5 – 0.9 µSv/h (west-southwest) |
| 60 km distance2 | 0.3 µSv/h | 0.4 µSv/h | 0.1 – 0.2 µSv/h | 0.3 – 0.4 µSv/h | 0.4 – 0.8 µSv/h |
| Ibaraki, City of Mito2 120 km distance | Not Available | 0.148 µSv/h | 0.152 µSv/h | 0.153 µSv/h | 0.157 µSv/h |
| 165 km distance3 | 0.14 µSv/h | 0.14 µSv/h | 0.15 µSv/h | 0.15 µSv/h | 0.17 µSv/h |
| Port of Toyko4 | 0.1 µSv/h | 0.1 µSv/h | 0.1 µSv/h | 0.1 µSv/h | 0.1 µSv/h |
| Location | April 6 | April 5 | April 4 | April 3 | April 2 | April 1 |
|---|---|---|---|---|---|---|
| Fukushima West-gate1 | 52 µSv/h | 52 µSv/h | 55 µSv/h |
59 µSv/h |
59 µSv/h |
71 µSv/h |
| 20 km distance2 Northwest direction | 52.5 µSv/h | 50.9 µSv/h | 51.5 µSv/h | 65.2 µSv/h | 59.2 µSv/h | 60.5 µSv/h |
| 30 km distance2 Northwest direction | 28.3 µSv/h | 29.1 µSv/h | 27.4 µSv/h | 35.2 µSv/h | 36.8 µSv/h (Identified as 25 km) | 34.5 µSv/h (west-northwest) |
| 30 km distance2 South direction | 1.0 – 1.3 µSv/h (west-southwest) | 1.1 µSv/h (west-southwest) | 1.0 µSv/h (west-southwest) | 1.0 - 1.2 µSv/h (west-southwest) | 1.1 µSv/h (west-southwest) |
1.0 µSv/h (west-southwest) |
| 60 km distance2 | 0.6 µSv/h | 0.4 µSv/h | 0.6 µSv/h | 0.6 µSv/h | 0.6 µSv/h | 0.3 µSv/h |
| Ibaraki, City of Mito2 120 km distance | 0.161 µSv/h | 0.167 µSv/h | 0.171 µSv/h | 0.176 µSv/h | 0.183 µSv/h | 0.19 µSv/h |
| 165 km distance3 | 0.16 µSv/h | Not available | 0.17 µSv/h | Not available | Not available | 0.19 µSv/h |
| Port of Toyko4 | 0.1 µSv/h | 0.1 µSv/h | 0.1 µSv/h | 0.1 µSv/h | Not available | 0.1 µSv/h |
| Location | March 31 |
March 30 |
March 29 |
March 28 |
March 27 |
March 26 |
|---|---|---|---|---|---|---|
| Fukushima West-gate1 | 71 µSv/h |
79 µSv/h |
117 µSv/h |
140 µSv/h |
35 µSv/h |
147 µSv/h |
| 20 km distance2 Northwest direction | 55 µSv/h 1900h | 59 µSv/h | 74 µSv/h | 77 µSv/h | 9 µSv/h | 12 µSv/h |
| 30 km distance2 Northwest direction | 31µSv/h (west-northwest) 1900h | 32 µSv/h (west-northwest) | 43 µSv/h | 41 µSv/h | 45 µSv/h | 46 µSv/h |
| 30 km distance2 South direction | 1 µSv/h (west-southwest) | 1 µSv/h (west-southwest) | 1 µSv/h | 1 µSv/h | 2 µSv/h | 2 µSv/h |
| 60 km distance2 | 1 µSv/h | 1 µSv/h | 2 µSv/h | 3 µSv/h | 3 µSv/h | 3 µSv/h |
| Ibaraki, City of Mito2 120 km distance | 0.2 µSv/h | 0.2 µSv/h | 0.2 µSv/h | 0.2 µSv/h | 0.2 µSv/h | 0.2 µSv/h |
| 165 km distance3 | 0.2 µSv/h | 0.2 µSv/h | 0.2 µSv/h | 0.2 µSv/h | 0.2 µSv/h | 0.2 µSv/h |
| Port of Toyko4 | 0.1 µSv/h | 0.1 µSv/h | 0.1 µSv/h | 0.1 µSv/h | 0.1 µSv/h | 0.1 µSv/h |
1. Japanese Atomic Industrial Forum (internal news updates. JAIF values are consistent with NISA data). Please note that the West-gate location was selected as this was the most commonly reported station, using 16:00 data.
2. http://www.mext.go.jp/english/
3. http://www.aist.go.jp/aist_e/taisaku/en/measurement/index.html
4. http://www.mlit.go.jp/kowan/kowan_fr1_000041.html
As of March 31, the Nuclear and Industrial Safety Agency (NISA) reported that 21 workers at the Fukushima prefecture had received doses exceeding 100 mSv. No worker has received a dose above Japan’s guidance value of 250 mSv for restricting the exposure of emergency workers. (Source: IAEA Incident and Emergency Centre, April 4, 2011).
For detailed readings of environmental radioactivity level in Japan, please visit Japan’s Ministry of Education, Culture, Sports, Science and Technology (MEXT).