Time, Distance, & Shielding: Key Radiation Protection Principles

Radiation Safety

Time, Distance, & Shielding: Key Radiation Protection Principles

Any and all exposure to ionizing radiation is dangerous. However, it's truly impossible to avoid exposure completely. Since radiation is constantly present both in our environment (natural background radiation) and in our bodies. Even though this is the case, we must avoid excessive radiation exposure. We can do so by following the three basic tenets of radiation safety: time, distance, and shielding. In this article we'll explore how these three principles combine to work towards the goal of keeping radiation dose "ALARA". 

"ALARA" in Radiation Safety 

You'll remember from our recent blog post "Radiation Safety Programs: A Comprehensive Guide," that ALARA is an acronym that stands for “as low as reasonably achievable.” This simply means that the goal of any radiation safety program is to keep radiation doses as low as reasonably possible. 

We hope you find this article informative, and we look forward to hearing your feedback! 

Minimizing Radiation Exposure Time 

Limiting the amount of time someone is exposed to ionizing radiation (sometimes called ionising radiation outside of the US) in turn reduces the dose they receive. Minimizing the time of the exposure to radioactive material is crucial for radiation workers, patients receiving x-rays, and anyone who may be exposed to radioactive materials over the course of normal activities. 

Distance from the Radiation Source 

The intensity and dose of radiation decreases dramatically as the distance from the radiation source increases. An easy, logical way to think about the importance of distance is recognizing that the heat from a fire becomes less intense the further away you are from it. 

If you're able to calculate the intensity of radiation at one specific distance, it makes it possible to determine the intensity at any given distance. In these circumstances, the inverse square law is followed. 

Distance from the radiation source

The Inverse Square Law in Radiation 

The inverse square law states that radiation exposure is inversely proportional to the square of the distance from the source of radiation. For example, if the distance between an object and a radiation source doubles, there will be one fourth as much radiation exposure. If the distance between the object and the source of radiation is 10x'd, the exposure will be 100 times less. 

Radiation Safety Through Shielding 

Using or inserting the proper shield between yourself and a radiation source can greatly reduce or eliminate the dose received. Shielding measures minimize the radiation absorbed for anyone who may be exposed to sources of radiation. 

The importance of shielding in radiation is based on the principle of attenuation. Attenuation is the degree to which a radio wave or ray's effect can be blocked or bounced with the use of a barrier material. 

The barrier used depends on the type of radiation it's trying to block. For penetrating radiation (think gamma rays and neutrons), lead, concrete, and water provide the best level of protection. This is the reason that your dentist places a lead blanket on you when x-rays of your teeth are being taken. It's also why certain radioactive materials are stored underwater, or in concrete or lead-lined rooms. 

When it comes to alpha radiation and beta radiation, special plastic shields are able to stop beta particles, and - believe it or not - air stops alpha particles. 

The amount of shielding required depends on the intensity of the penetrating dose. Metals are often used due to their strength and high resistance to radiation damage. Lead's higher atomic number enables it to lessen the effects of gamma and x-rays. 

Generally, the higher the density of a material, the more effective it will be at blocking gamma and x-ray radiation. However, it is possible that lower density materials can become more effective with increased thickness. 

Shielding from xray

RDC's Commitment To Radiation Safety 

Radiation Detection Company is dedicated to keeping you and all your employees safe. We have 75 years of experience providing the highest quality dosimetry service to over 28,000 companies nationwide.  

Want to take the next step in getting your organization set up with RDC’s radiation safety products? Please visit our Solutions page to view our full suite of offerings. We offer a wide range of affordable and comprehensive solutions to fit the needs of any organization, large or small.  

Have a question that we did not address in this article? Please reach out to our Customer Care team, and one of our specialists will be happy to assist you. 


Dosimeter badge services for medical, dental, and veterinary businesses

Learn how Radiation Detection Company’s easy-to-use dosimetry solutions can boost the efficiency of your practice.

Radiation Safety Guide