Dr. Tsubokura's Radiation Lecture Vol.36

Author: Masaharu Tsubokura

Editors: Akihiko Ozaki M.D., Yuki Senoo

71. Alpha ray has low penetrating power

Unstable radioactive substances discharge unnecessary protons, neutrons, electrons, and energy as radiation to stabilize themselves. Radon and radium discharge a set of 2 protons and 2 neutrons called “alpha rays.”

Cesium and potassium emit either 1 electron or a unit of energy, which are called a “beta ray” and a “gamma ray,” respectively.

An alpha ray consists of 4 particles, whereas a beta ray consists of only 1 electron. This makes alpha particles heavier and larger than beta particles.

Because of this feature, alpha particles travel for only a few centimeters in the air, and they cannot even penetrate a piece of paper.

Therefore, regarding the radiation exposure effect from radon in the air, we need to be concerned about internal radiation exposure caused by inhalation and do not have to worry about external radiation exposure.

This is because clothing and skin can cut off the alpha rays emitted from radon before they reach our bodies.

72. Pay attention to gamma rays in daily life

Unstable radioactive substances discharge unnecessary protons, neutrons, electrons, and energy as radiation to stabilize themselves. Cesium and potassium emit either 1 electron or a unit of energy, which are called a “beta ray” and a “gamma ray,” respectively.

Beta particles can travel for several meters in the air because they are much smaller and lighter compared to alpha particles. However, they also cannot penetrate through human skin and reach the inside of the body. On the other hand, gamma rays can travel for several hundred meters, and it requires a lead wall that is a couple of centimeters thick to shield them completely.

Therefore, we only need to consider how to protect ourselves from gamma rays and do not need to worry about the influence of external exposure to alpha rays and beta rays in our daily lives.

In general, air radiation dosimeters are calibrated to measure gamma rays, and a particular measuring device is necessary to measure alpha and beta radiation sources.

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The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, on May 15th and 22th 2016 was reproduced for MRIC Global under the author's permission.

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