Jeezus.....Simulation Map of Cesium-137 Deposition Shows High Contamination Levels on West Coast

The IAEA/WHO and UNSCEAR considered areas with exposure greater than 40 kBq/m²; the TORCH report also included areas contaminated with more than 4000 Bq/m² of Cs-137. The TORCH report might be alarming but 4 kBq/m² of Cs-137 only gives an external gamma dose of 56 μSv per year (which is close to nothing, a 1 in 356000 chance of death due to cancer). The internal dose will depend greatly on the diet of the person and the degree to which simple countermeasures such as Prussian blue are used in animal farming. <2>.

To sum these properties up

* The dose rate due to external irradiation from uniform contamination of the ground by 137Cs is 1.6 x 10-12 Sv hr-1 Bq-1 m2.
* The internal dose for ingestion is 1.2 x 10-8 Sv Bq-1
* The internal dose for inhalation is 8.7 x 10-9 Sv Bq-1

Note that 4 kBq/m² is the minimum level which is considered by the TORCH report. The TORCH report does not consider contamination under that threshold, but contamination levels between 4 and 40 kBq/m², which are ignored by the Forum's report. The lower limit for 137Cs which the authors of the TORCH report used is exceptionally low, all soil contains radioactive isotopes which are natural, the most important of these is 40K. For example a randomly chosen soil, From the Trinity test site, has about 1000 Bq kg-1 of radioactivity. <3> which results in a square meter of soil having about 100 KBq in the top 10 cm. It is important to note that radioactivity is present everywhere (and has been since the formation of the earth).

According to the IAEA, one kilogram of soil typically contains the following amounts of the following three natural radioisotopes 370 Bq 40K (typical range 100-700 Bq), 25 Bq 226Ra (typical range 10-50 Bq), 25 Bq 238U (typical range 10-50 Bq) and 25 Bq 232Th (typical range 7-50 Bq).<4>.