l          Radiation Protection Basics

Three basic concepts apply to all types of ionizing radiation, namely time, distance and shielding.  When an authority develops regulations or standards that limit how much radiation a person can receive in a particular situation, these three concepts might affect a person’s exposure.

Ø          Time

The amount of radiation exposure increases and decreases with the time people spend near the source of radiation.  In general, the exposure time should be assessed as how long a person is near radioactive material.  Gamma and x-rays are the primary concern for external exposure.

Ø          Distance

The farther away people are from a radiation source, the less their exposure.  How close to a source of radiation can a worker be without getting a high exposure?  It depends on the energy of the radiation and the size (or activity) of the source.  Distance is a prime concern when dealing with gamma rays, because they can travel long distances.  Alpha and beta particles don’t have enough energy to travel very far.

As a rule, if you double the distance, you reduce the exposure by a factor of four.  Halving the distance increases the exposure by a factor of four.

Ø          Shielding

The greater the shielding around a radiation source, the smaller the exposure.  Shielding simply means having something that will absorb radiation between you and the source of the radiation (but using another person to absorb the radiation doesn't count as shielding).  The amount of shielding required to protect against different kinds of radiation depends on how much energy they have.

1.            Alpha (a) – a thin piece of light material, such as paper, or even the dead cells in the outer layer of human skin provides adequate shielding because a-particles can't penetrate it.  However, living tissue inside body, offers no protection against inhaled or ingested a-emitters.

2.            Beta (b) – additional covering, for example heavy clothing, is necessary to protect against b-emitters.  Some b-particles can penetrate and burn the skin.

3.            Gamma (g) – thick, dense shielding, such as lead, is necessary to protect against g-rays.  The higher the energy of the g-rays, the thicker the lead must be.

4.            X-rays – pose a similar challenge as g-rays, so x-ray technicians often give patients receiving medical or dental X-rays a lead apron to cover other parts of body.

According to International Commission of radiation Protection (ICRP), the annual individual dose limits is 20 mSv/year for a worker frequently in an exposure of radiation.  Every nuclear power plant would have own maximum dose and would monitor each worker to ensure that none of them would receive the annual dose exceeding the ICRP standard.