It is well known an atomic bomb was dropped in Hiroshima in 1945. However, many people who are living in another countries have no idea how Hiroshima recovered since the day of the tragedy. Please just enter the keyword “Hiroshima safe” on the internet search. You will be surprised to see in this 2016 people still search the information with keywords such as “how long before hiroshima is safe” “how long did it take for hiroshima to be safe” “why isn’t hiroshima radioactive” “how long was hiroshima uninhabitable” “why isn’t hiroshima still radioactive” “hiroshima safe to visit” “hiroshima and nagasaki today life” “hiroshima radiation effects” etc.
Furthermore, Japan attracted more world’s interest by a nuclear accident occurred in 2011. The accident occurred at Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Station related from the Great East Japan Earthquake on 11th March 2011, which led to the release of radioactive materials such as lodine or caesium to release into the atmosphere and the sea.
Is Japan safe? Is all over Japan radioactive?
First of all, it would be a good idea to learn about radiation briefly. How much do you know about radiation?
Radiation is energy. Radiation exists in the world always and always even before the birth of human beings. There are two kind of radiation. One is radiation from the natural world, the universe, the earth, the atmosphere and food. It is referred to as natural radiation since radiation of a substance that exists naturally. The other is artificially-made radiation generated for medical X-ray and CT scan, biology use, building inspections, or nuclear power plants. Without your realizing, you are exposed to radiation and appreciate it in your daily life. Everyone takes low dose radiation every day.
Radiation is a sort of light. It is the generic name of α (alpha) radiation, β (beta) radiation and γ (gamma) radiation that is released by the decay of radioactive nuclides. Broadly, it refers to all of the electromagnetic wave and particle beam including electromagnetic waves such as X-ray, neutron radiation and cosmic rays that are released by the reaction of nuclei or elementary particles.
The capability to release the radiation is called radioactivity. The radioactivity is that the nature of spontaneously radiation is emitted from the substance. There are two units to measure radiation. One is called “becquerel” defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The other is called “sievert” that is a unit of radiation absorption.
Natural radiation has various radiation dose depending on its location and altitude. In addition, an amount that one person receives the natural radiation in one year is approximately 2.4 mSv (millisievert) in the world average. We will absorb 0.39 mSv from the space, 0.48 mSv from the earth, 0.29 mSv from food and 1.26 mSv from Radon in the atmosphere.
The type and nature of artificial radiation is the same as natural radiation. The impact on human bodies will not be different from the natural radiation. Artificial radiation dose received by medical treatments is 0.05mSv from chest X-ray, 0.6 mSv from chest X-ray, and 6.9 mSv from CT scan. The average radiation dose a Japanese receive in one year is 1.5 mSv natural radiation. It will be 3.75 mSv when it includes medical care. The average of the world is 3.13 mSv. The main reason the average value of Japanese is slightly higher than the world average is radiation dose from medical care such as X-ray is high 2.25 mSv compared to 0.61 mSv of the world average. NRA, Japan Nuclear Regulation Authority announces “Reading of environmental radioactivity level by prefecture” on their website every day.
It is understandable you still might be worries as radiation is invisible and you can see the effect only after long term. Many Japanese got interested in learning how to measure radiation with simple detectors in 2011. Do you know you can use radioactivity detector to measure air dose rate? Are you interested in finding how to measure radioactivity air dose rate correctly?
Radioactivity air dose rate is measured in order to know the external exposure amount of the specific location. Therefore, β radiation that will not contribute to external exposure would not be measured. Radioactivity air dose rate should be measured in the position of 1m(3.28ft) from the surface of the earth. The measured values will not be the same numerical value for a variety of reasons. Therefore, it would be better to measure as many times as possible to record the average value. Even using a simple type of detector, it will becomes a trusted data by using the same equipment continuously under the same conditions to record the day-to-day change.
Additionally, it will be statistically very significant information when the measurement is carried out in as many point as possible. When it is measured near the ground surface, it cannot be correctly converted to the external radiation exposure if β radiation is also me asured. Even if there is a fixed amount of radiation substances, the amount radiation emitted within a certain time is not a constant. For the generation of radiation is natural phenomena, it is not possible to measure without any real value (true value) accurately. It is called uncertainty that those which show a true value within the extent of the variation from the measured values. In the nature, there is radiation coming from the space or natural radiation emanating from the ground or walls. When measuring a certain location, the measured values always reflect these effects. This is called background. In addition, noise from detectors or system will also greatly affect the error of the measured value. In order to minimize these effects, as it is stated above measuring several times and recording the average value is recommended.
Although it is recommended not to go closely Fukushima Nuclear Plants, radiation dose of the other areas in Japan is low, which the value of 1.5 mSv natural radiation can prove. This values is lower than the average value of the world. In order to verify, I myself measured radiation dose in front of Hiroshima Atomic Bomb Dome recently. I measured three times in total. The average value of the three measurements was 0.75 mSv.
How would you feel now? Are you still worried about radiation? Radiation is nothing to be afraid of if you have the correct knowledge. Japan is a safe country, and Hiroshima is a safe city.
If you have any questions or comments, feel free to contact me.