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Alpha and Beta Radiation Shielding

Alpha and Beta Radiation are both powerful. What are the characteristics? How does the shielding work for each one?

Alpha Radiation Shielding

A thorium rod in the cloud chamber contains alpha particles and electrons (reflected by a magnetic field).

The following characteristics of alpha particles are essential for their protection.

  • Alpha particles are fast nuclei and relatively hefty and have a double positive electrical charge.
  • Alpha particles engage with matter mainly via column forces (ionization and material arousal) between atomic orbital electrons’ positive and negative load.
  • Alpha particles ionize matter strongly and lose their cinematic energy fast. In contrast, all their energy are deposited along their short routes.
  • The stopping power of the Bethe formula is characterized.

For alpha particles and highly charged particles, the power density of most materials is strong. Alpha particles thus have extremely small ranges. 

For instance, the aluminium alloy’s 5 MeV alpha particle lengths are only about 0.002 cm or in the air around 3.5 cm. A small sheet of paper may block most alpha particles.

Even the dead cells in the external skin layer offer sufficient protection since alpha particles cannot enter the skin.

There is thus no significant issue with protecting alpha radiation alone. Alpha radioactive nuclear may, nevertheless, lead to severe health risks via ingestion or inhalation (internal contamination). When eaten or breathed, the alpha particles damage the inside tissue severely as a result of decline. In addition, pure alpha radiation is highly uncommon, and alpha decay is often accompanied by gamma radiation.

Beta Radiation Shielding

Alpha particles or electrons (magnetic field deflected) in a cloud chamber from a thorium rod.

The following characteristics of beta particles (electrons) are essential for their protection.

  • The mass is equivalent to the mass of electrons they contact, and a much more portion of their initial energy is lost in the interaction, unlike the alpha particle. 
  • Beta particles are powerful electrons with a single negative electrode.
  • Their journey isn’t that simple. Beta particles take a highly zig-zag trajectory through the medium of absorption. This resultant particle route lengths the linear (range) penetration of the substance.
  • Because beta particles are extremely low in mass, they mainly attain relativistic energy.
  • Beta particles also vary in the percentage of energy lost via a radiative mechanism known as the brake exposure from other heavily loaded particles. Therefore thick materials are unsuitable for high-intensity beta radiation shielding.
  • The shockwave of electromagnetic radiation called Cherenkov radiation develops when a beta particle travels more quickly than the light velocity in the medium.

Beta ionizes matter less than alpha radiation. In contrast, the range of beta particles is longer and relies heavily on initial kinetic particle energy. Some have sufficient power to worry about external exposure. 

A 1 MeV beta particle may flow around 3.5 m in the air. Such beta particles may enter the body and deposit the internal dosage on the surface. Therefore, more protection is needed than in the case of alpha radiation.

As beta particle shields, materials with a low atomic Z number are suitable. The brake radiation (secondary radiation – X-rays) is linked with high Z materials. This radiation is generated when beta particles are slowed down while moving into a highly dense material. Heavy clothes, thick cardboard or thin plate aluminium, will shield against beta radiation and reduce brake radiation generation. 

Lead and plastic are often used to protect against beta radiation. The literature on radiation protection recommends placing plastic first to capture all beta particles before any plumbing protection being employed. This suggestion is based on the well-known notion that radiative losses in larger atomic quantities (Z) than in low Z materials are more common.