Dr. Tsubokura's Radiation Lecture Vol.61
Author: Masaharu Tsubokura
Editors: Akihiko Ozaki M.D., Yuki Senoo
121. Tritium’s Radiation Level is Very Low
A radioactive substance called “tritium” often appears in articles covering the issues of contaminated water released from the nuclear plant. Tritium is not only an artificial substance that was released from the accident this time but also one naturally generated in our environment.
As previous articles have explained, the health effects of radiation are determined by the extent of the exposure dose, not by whether their source is a natural or artificial radioactive substance.
Tritium emits a very low level of radiation (beta rays), and its energy level is so small that plastic wraps can block it. Therefore, the level of internal exposure caused after ingesting 1 becquerel of tritium is known to be much lower than that caused by other radioactive substances, such as cesium and potassium (about 1/1000 of cesium).
Even when our body ingests tritium, it gradually discharges the substance to the effect that its level will be halved in tens of days. Tritium will also not get concentrated in vivo.
In short, after the Fukushima Daiichi nuclear power plant accident, most radiation exposure was caused by cesium. Therefore, similarly to strontium and plutonium, tritium is not a radioactive substance considered to have a significant health effect on our bodies.
122. The Energy Level of Tritium Is Significantly Small
A radioactive substance called “tritium” often appears in articles covering the issues of contaminated water released from the nuclear plant. Tritium is not only an artificial substance released from the nuclear power plant accident but also one naturally generated in our environment.
Under careful planning and since before the Fukushima accident, tritium has been released from nuclear power plants and fuel cycle facilities around the world to surrounding waters and rivers. According to data from the 2000s, nuclear power plants in the United Kingdom and Japan released 2000 trillion becquerels and 400 trillion becquerels of tritium each year, respectively.
You may be surprised by how enormous these numbers are. However, the amount of tritium released in the environment was determined under environmental regulation guidelines considering safety.
The reason why such an enormous amount of tritium could safely be released is that the energy level of radiation emitted from tritium is very low, and its effect on the human body (exposure dose) is very small compared to that of other radioactive substances. A total internal exposure dose of tritium will reach 1 millisievert only after one ingests tens of millions of becquerels of the substance. Thus, the limit of tritium that can be released to the environment at a sufficiently safe level is many orders of magnitude higher.
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The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, on 7th and 14th May 2017 was reproduced for MRIC Global under the author's permission.