Radiation Detection FAQs

If one looks at a chart of the whole electromagnetic radiation spectrum, it can be seen that although the spectrum is quite wide, the slice of it that is visible light – what we can see – is very narrow indeed. Most of the electromagnetic radiation spectrum is invisible to the eye, but it is still there. Ultraviolet radiation can’t be seen, but it’s what causes sunburns. Infrared radiation, at the other end of the spectrum, can’t be seen either, but it can be felt as the warmth radiating from a fireplace or warm object. Since most radiation is invisible, we must find other ways of detecting it, since much of it affects us whether we can see it or not.

The type of radiation that the term itself brings to mind, for most of us, is Ionizing Radiation, what we normally associate with nuclear reactors and power plants. It is the type of radiation that we are primarily concerned with here. It is radiation that is powerful enough to remove electrons from atoms, and includes x-rays, cosmic rays, and emissions from radioactive materials.

The process by which unstable atoms spontaneously transform to new atoms (or the same atom in a lower energy state) and in the process emit radiation is known as Radioactivity. In process, a single high-energy atom decays to a lower energy state and dumps excess energy by ejecting a particle, set of particles, and/or gamma or x-ray photons. The emission of these particles is radioactivity, and they constitute ionizing radiation. We can’t see, hear, smell, taste, or touch ionizing radiation, so we use instruments to detect and measure it.

It would surprise some to know that our bodies are naturally exposed to very low levels of ionizing radiation throughout our lives, coming from various natural sources. Our bodies ‘absorb’ radiation and even though we don’t become radioactive ourselves, we nevertheless understand that the effects of radiation absorption are cumulative over our lifetimes and can result in health problems if the amount is excessive. That’s why it is important to be able to detect sources and intensities of ionizing radiation, especially in the workplace, and limit our exposure or ‘dose’ to avoid the deleterious effects of over-exposure to ionizing radiation over time.

Ionizing radiation is not only detectable, but can also be measured, which is extremely helpful. Measuring radiation isn’t the same as weighing a basket of vegetables; radioactivity actually happens one atom at a time, and although a single event is very directional, and multiple events are also very directional, not all events release particles in the same direction, so “radiation” goes off in all directions. A continuous stream of radiation is just a collection of  many, many separate decay events or transformations happening one after another. Thus, when we measure radiation, we’re measuring Units of Activity, and we express these measurements as Curie (Ci), or 37 Billion transformations per second (2.22 trillion per minute); and Bequerel (Bq), or 1 transformation per second. (“Curie” is the amount of activity in 1 gram of Radium, and is named after Marie Curie, a Nobel Prize physicist and chemist who conducted pioneering research on radioactivity.)

Radiation can be found in many industries and in thousands of locations across the country, not just in large metropolitan areas and nuclear power plants. If not properly controlled and monitored, they can be a threat to public health and safety. Here are some of the places where radiation detection and monitoring technologies should be used:

Holiday Events: If you are at a crowded holiday event, like a New Year’s Eve celebration, or ride the subway in that area, you may not even notice the officers in plain clothes walking around with backpacks; but these special radiation detection backpacks actually monitor the area to rapidly locate and detect gamma-emitting radioactive sources in large areas.

Sporting Events: Large sporting events are high-risk targets for malicious radiation threats. Where are the best places to monitor fans, do baseline scanning, and set up remote monitoring — and what technology is available?  Download the Sporting Event Radiation Event Scenario map with markers for safety and security radiation monitoring points.

View a PDF poster: U.S. Map of Radiation Threats

View a video map that outline the various locations of radiation threats in the U.S.

There are advanced, integrated radiation detection and radioactivity measurement instruments that help mitigate the threat and keep you safe, including radiation detectors, radiation monitoring devices, and radiation measurement instruments that provide comprehensive, real-time monitoring, early warning, and complete information in the palm of your hand, in the work place, and in your neighborhood. Here is a sample:

1. A Personal Radiation Detector (PRD) is a pager-sized instrument used for gamma detection, gamma ID, and neutron detection. Police officers wear this PRD as a primary means of locating source as they walk the event. The instruments use patented Natural Background Rejection (NBR) technology, to detect, locate, and identify radioactive nuclides such as nuclear weapons, dirty bombs, and orphaned or purposely masked sources while eliminating typical nuisance alarms from the natural environment such as granite buildings, underpasses, tunnels and subway systems.
2. Spectroscopic Area Monitors can detect and identify radiation on location and report results to users miles away from the source. They deliver high precision gamma and neutron radiation measurements and deliver real-time data across a wide range of environments and radiation dose rate levels. These types of instruments allow safety and security personnel to quickly and safely identify and address radiation threats while maintaining good ALARA principles. Units can be positioned at potentially dangerous locations to alert nearby personnel via a phone app or to a remote command center. Multiple instruments can be networked wirelessly to expand reach across a large venue or across an entire city, while keeping personnel away from the hazardous area.
3. A Radiation Detection Backpack is ideal for field use to quickly locate orphaned sources, radiation contamination and potential malicious intent sources – without being highly visible to the crowd. The backpack is equipped with a large, but lightweight, gamma radiation detector as well as a neutron detector especially designed for use with a human body without the need for expensive Helium-3 (He-3).  The pair of detectors provides excellent sensitivity while on the move and from distances up to several city blocks, making it ideal for high traffic, large area security like a parade.  Officers can strap the backpack on, and unobtrusively locate and very rapidly detect gamma-emitting radioactive sources in large areas.
4. A Handheld Radiation Isotope Identifier (RIID) is used to search for, and identify materials that could make a dirty bomb, by providing the exact isotope of the radioactive material in order to assess the potential threat and quickly initiate a plan of action. Typically used to confirm source identification when paired with a backpack or PRD, the RIID’s detector is high resolution for making accurate identifications and large enough to make the identification from a safe distance. 
5. A Mobile Detection System is an advanced mobile solution for radiation survey, patrol and isotope identification in applications such as nuclear incident response, radiological hotspot identification, environmental contamination detection and routine security surveillance. Some systems make it possible to easily survey an area to determine the baseline radiation contour so known areas of higher radiation such as hospitals and highway underpasses can be noted, eliminating the need to investigate those areas during an event. The survey data, correlated with GPS mapping coordinates, is saved for comparison with readings taken during periodic patrols. This results in increased response accuracy and eliminating false positives.

You can view additional technologies in our Radiation Detection & Measurement web pages.

A Geiger counter — named after Hans Geiger, a German scientist from the early 1900s who worked on detecting radiation — is an instrument that can detect radiation. Geiger counters can tell you there is radiation around you, but it can’t tell you the original source of the radiation, what type it is or how much energy it contains.

Personal radiation detectors detect and localize radiation sources generated by manmade devices such as nuclear weapons, improvised nuclear devices (INDs) or radiological dispersal devices (RDDs.  They are worn on the person and provide radiation detection in the immediate area around the wearer. The instruments can quickly pinpoint the location of radioactive sources easily, allowing the wearer  to respond to the exact location of a threat.

For additional details, read What’s the Difference Between a Geiger Counter and a Personal Radiation Detector?

Yes, there are variations of personal radiation detectors that depend on type of use (eg police vs hospital worker) and needs, like monitoring dose rate, stay time, and peak values. Also, interdiction equipment is used if the primary requirement is to search out and find radiation.  Personal safety instruments are needed if you know you are in an environment where radiation exposure may be a factor and you want to be alerted when you are at risk. First responders and law enforcement usually need radiation detectors to locate illicit radiation sources.  One must also consider the type of environment one is working.  Is it challenging because of extreme temperatures or is it over water?  Make sure you get a personal radiation detector that can withstand harsh working conditions. If you are not in an emergency situation where radiation levels are wildly fluctuating or definitely unknown, but your job regularly exposes you to radiation, you may need to wear a dosimeter to monitor your radiation exposure for tracking and logging purposes toward a prescribed annual radiation dose limit. 

We’ve developed a ‘workflow’ type of questionnaire to help guide you in finding the best choice of personal radiation detection that will meet your needs.  It’s available as an interactive website page as well as an infographic pdf.

Radioactive material is commonly found throughout nature in air, water, soil, rocks and plants. The amount of natural radiation you are exposed to fluctuates depending on your activity and location. We refer to this as background radiation and the varying levels of it can cause false alarms when trying to determine if the high radiation levels you may be detecting on your radiation measurement and detection device have identified a potential threat.

Natural Background Rejection (NBR) technology is a technology used to eliminate fluctuating natural background levels while measuring radiation. This proprietary and patented technology is used to quickly differentiate between natural and artificial radiation by stripping away any natural background radiation that is registering, delivering you a more accurate result of artificial radiation levels.

Operators using instruments without NBR often set their alarm thresholds higher to eliminate the nuisances of false alarms or ignore alarms due to their frequency potentially missing out on hidden or shielded sources. Using an instrument with NBR allows you to keep your alarm threshold extremely low without the need to worry about false alarms from non-threatening sources so when the alarm goes off, you know it is time to take action.

By delivering a more accurate result, first responders and those responsible for identifying potential threats will be more confident and efficient in knowing when the threat is real.

The purpose of this educational section on radiation detection is to alert first responders, fire, and police departments that nearly every city and region has radiation sources.  The sources, if involved in an accident could produce unwanted exposure.  Think about it: if firefighters were called to a warehouse fire where bottling or packaging occurred or where density gauges were stored without radiation measurement devices, how would they know if they were being exposed to dangerous levels without radiation detectors?  Knowing that radiation sources are near, not always in plain sight like a hospital or nuclear power plant, and also knowing there is available grant money to procure state of the art instruments to measure and quantify the radiation, is the point of this map. 

Many communities believe there is no danger from radiation near them if there is no nuclear power plant.  That’s not true, which is why many fire departments and police carry radiation detectors today, most from the Cold War era.  Upgrading those aged detectors to also pull double duty to combat domestic terrorism threats, respond quickly to small amounts of radiation, alert users when radiation dose rates are high, are needs that every community should consider. 

Radiation detection and measurement is just another safety precaution that should be addressed by all communities.  Safety and security personnel should be able to detect, localize, identify, and measure radioactivity in any scenario. And the first step is being knowledgeable enough to know where the radiation concerns could be located.