Gama Radiation Penetration

 http://www.radiation-scott.org/radsource/1-0.htm

For radiological incident scenarios, one mainly deals with the following types of radiation: (1) alpha radiation, (2) beta radiation, (3) gamma rays, and (4) neutrons.

Alpha Radiation

Alpha radiation is made up of helium atoms stripped of electrons. The stripped atoms are called alpha particles.

Emitted alpha particles are positively charged. They can be stopped by a piece of paper and pose a concern mainly when emitted inside the body.

Alpha emitters are isotopes that emit alpha particles. When the alpha emitter is on the surface of the skin, the dead layer of the skin adequately protects the body from harm by trapping the emitted alpha particles. However, if the skin has a wound, the alpha emitter can enter the body through the wound and cause harm.

Beta Radiation

Beta radiation is made up of negatively charged electrons. These electrons are called beta particles.

Beta emitters are isotopes that emit beta particles. Beta particles can pass through the dead layer of the skin and cause harm to the body.

Clothing can provide some protection from beta radiation injury to humans when the beta emitter lands on the outside of the clothing. Beta emitters that are inhaled into the lung or ingested into the gastrointestinal tract can cause harm.

Gamma Rays

Gamma rays have no charge or mass. Gamma rays can go through the entire body and can damage multiple organs.

Gamma emitters are isotopes that emit gamma rays. Gamma emitters that deposit on the outside of the body and those taken inside the body both can cause harm. Clothing provides little protection from gamma rays.

Neutrons

Neutrons have mass but no charge. Neutrons can penetrate deep into the body, and while doing so, can produce gamma rays through their interaction with tissue atoms. Thus, all neutron exposures involve some gamma rays. Clothing provides essentially no protection from neutrons.

Figure 1.1 shows the relative penetrating power of different radiations.

FIGURE 1.1

People are exposed to radiation in mainly two modes:

1. From radiation sources outside the body (external exposure).

2. From radioactive substances that are inhaled or ingested into the body (internal exposure).

Figure 1.3 shows the external and internal models of exposure. Radioisotopes taken into the body deposit in and irradiated different tissue depending on their chemical properties.

FIGURE 1.3

Radiation sources can also enter the body via wounds.

There are many different radiation exposure scenarios that can be evaluated. Some examples follow:

• External exposure from relatively distant radiation sources (e.g., neutrons and/or gamma rays)

• External exposure from nearby radioactive soil

• External exposure from radioactive contamination on the outside of the body

• Internal exposure from inhaled radioactive substances

• Internal exposure from ingested radioactive substances

• Combinations of the above

The radiation exposures may be brief as during a nuclear detonation or protracted (i.e., spread over an extended period) as could arise after inhaling or ingesting radioactive substances released from a nuclear accident or radiological weapon.

1.2 Nuclear Workplace

The nuclear workplace includes occupational settings such as nuclear power plants, nuclear weapons production facilities, nuclear medicine-related facilities, and radiation therapy facilities. Many workers are routinely exposed to radiation in such facilities. However, their radiation exposures are usually strictly controlled to avoid harmful effects of irradiation.