Preparedness for Nuclear Emergencies: Radiation Safety, Potassium Iodide and Dosimeters

Radiation is a serious concern in the aftermath of nuclear accidents or other NBC (Nuclear, Biological, Chemical) events. Having the proper equipment to detect ionizing radiation, and knowing the hierarchy of actions to take in order to reduce radiation damage, is critical for success in the face of such a crisis.

This guide will touch on the steps you can begin to implement now to protect yourself and those you love from direct radiation threats, radiation sickness from radioactive fallout, and consuming contaminated food and water.

What Is Ionizing Radiation?

First, it's important to understand what ionizing radiation is, and how it can be a threat to you. Ionizing radiation is electromagnetic radiation that has enough energy to strip electrons from atoms, creating ions. This type of radiation is dangerous because it can cause damage to DNA, which can lead to cancer.

There are four main types of ionizing radiation:

Alpha particles are relatively large and heavy, so they don't penetrate skin. However, if alpha particles are inhaled or ingested, they can be extremely harmful.

Beta particles are smaller and lighter than alpha particles. They can penetrate skin, but they're not as harmful as alpha particles because they don't stay in the body as long.

Gamma rays are similar to x-rays; they're high-energy waves that can penetrate skin and other materials.

Neutron radiation is made up of uncharged particles and is very penetrating. It's often used in cancer treatment because it can kill cells quickly.

Now that we know what ionizing radiation is and how it can be harmful, let's learn about some basic safety measures that everyone should take in the event of a radiological emergency, in order of importance.

Time, Distance and Shielding.

Anything you can do to:

- Minimize your time in a radiation zone,

- Maximize you distance from the source of the radiation and,

- Put the thickest, densest material between yourself and the source of the radiation, will increase your ability to not only survive, but thrive.


Particulate Radiation Threats and Considerations

Alpha and beta particles are tiny physical pieces of radioactive material that are often found in the fallout from nuclear emergencies or incidents. Hazmat suits along with gloves, full face respirators and boots, will block all but the most persistent Alpha and Beta particles from direct contact with your tissue. Be aware that since they are physical particles (think tiny radioactive dust motes), wind or rain can push them anywhere dust or smoke can access. They can remain radioactive for long periods of time, depending on the half life of the particular isotope, and can penetrate into water systems and crops.

The best defense against particulate radiation is to get away from it (ie: increase distance). If preparing for the possibility that you won’t be able to evacuate, the next most important actions are to have secure, covered food and water storage, and have the ability to seal up the building or structure you intend to shelter in. This would be a nuclear fallout or acid rain scenario, where you need to be prepared to stay in your dwelling for days or weeks.

If preparing for this possibility, assume the power will be out, the shower won’t work and the toilets won’t flush, and plan accordingly. Disease is a very real killer, and threatens anyone in this scenario.

Nuclear fallout from a nuclear attack or accident poses the greatest threat to people through inhalation and ingestion of radioactive iodine which quickly absorbs into the thyroid gland where it emits radioactivity and damages cells resulting in thyroid cancer. Potassium Iodide (Ki) pills protect your thyroid gland by flooding it with non-radioactive iodine which blocks cellular uptake of radioactive iodine.

As such, taking Ki pills offers a high degree of protection against one particular type of radioactivity, and should be limited to use only when eating or drinking contaminated food or water. Of course, you will need a dosimeter to be able to measure those contaminants – more on that later.


Thyrosafe and New Roots Ki Tablets

Thyrosafe, made by Recipharm, is a popular option for medical grade Potassium Iodide (Ki) tablets. They make up a large portion of the tablets being fielded by groups, organizations and agencies involved in nuclear disaster and emergency preparedness.

Thyrosafe comes in blister packs, 20 x 65mg tablets to a box. The price per unit is quite high. Since potassium iodide is simple and inexpensive to produce in its pure form, some prefer to seek other methods of storing Ki.


An alternative comes from the herbal industry. New Roots herbal produces Potassium Iodide (Ki) Pills for nuclear emergencies. They are 100 x 65mg tablets to a bottle, in Quebec, Canada. They are tested for purity in an ISO certified laboratory, and have recently gained popularity as world events have consumed the available supply of Thyrosafe and similar pharmaceutically produced products.


Electromagnetic Radiation Threats and Concerns

Gamma rays and X Rays are both electromagnetic (EM) radiation, like light. They travel in a straight line at the sped of light (186,000 miles per second).

By the time you see evidence of a nuclear emergency, initial gamma rays have already reached you. Gamma rays are in the form of photons, which act like both particles and waves and damage living tissue by stripping electrons from it in a process called ionization.

Ionization of human tissue has been linked to causing legions and burns in the short term, and many different kinds of cancers over the long term. Gamma rays can also be scattered or reflected which increases the possibility of scattered dose exposure (SDE).

SDE is an indiscriminate type of exposure that occurs when gamma rays bounce off surfaces in the environment and come into contact with people or wildlife nearby.

Unlike the Alpha and Beta particulate radiation above, EM radiation can penetrate dense materials. The activity and energy levels of the photons dictate their penetrating ability, but typically X rays can penetrate wooden house walls and aluminum engine blocks, and Gamma rays can penetrate through wooden houses and brick walls.

The density of material required to offer protection starts at sandbag walls, and escalates up to wood piles, dirt berms and concrete blocks. This is the principal reason why trying to evacuate away from the source of radiation is the best practice for most people.

Neutron radiation is highly damaging and readily passes through most materials. Neutrons have no charge, and so can pass through dense objects but are shielded by light elements. Water, being primarily hydrogen, is an excellent shielding material. In the home, buckets or bins full of water and stacked to form a wall can make an effective barrier. One caveat is you need to know you're protecting against neutrons, and from which direction they are coming, so you'll need a dosimeter capable of measuring them in order to defend against them.

Personal Dosimeters and Their Uses

Now that we've covered some basic safety concerns, let's talk about dosimeters. Dosimeters are small devices worn on your body that measure exposure to ionizing radiation. There are three main types: film badge dosimeters, direct reading dosimeters and electronic dosimeters.

Film Badge photographic film exposed to ionizing radiation; they're typically worn by people who work with high levels of ionizing radiation on a regular basis. Some models are designed for the user to read, and discolour in a predictable rate as they become saturated with ionizing radiation. These models act as direct reading dosimeters.

Thermo-Luminescent Dosimeters (TLD) are used for higher end medical tracking and when heated will emit light proportional to the amount of ionizing charge, allowing the measuring station to obtain a fairly accurate dose reading.

Direct Reading (or Pencil) Dosimeters use an ionizing charge on a filament to tell the wearer how much radiation they have been exposed to. As the ionization chamber becomes charged from the radiation, the filament moves across a graph. Pencil dosimeters are readily available from old stock, and were used to great extent in civil emergency kits and in the nuclear industry. They have major logistical drawbacks in that they require re-calibration on a calibration station prior to each use, the angle of viewing often gives different filament readings and the filaments could be moved from kinetic impacts like dropping or bumping. They were eventually replaced by more reliable electronic dosimeters, but many still remain today.

Electronic Dosimeters use sensors that measure exposure to ionizing radiation; they provide real-time data and tracking on exposure and intensity levels, which makes them ideal for use during an emergency or as a mainstay in the nuclear industry.

An electronic dosimeter (or survey meter) will allow you to gather very important data, such as the direction from which the radiation is emanating, the current intensity of a radiation zone you might be in, the amount of whole body dose you have picked up over a period of time, and the positive indication that the mitigating actions you implement are working.

Briefly, to detect the direction of the radiation: Ensure the dosimeter is in rate or intensity measurement mode, then hold the it in your view and move forward and backwards, side to side, until you establish the directions you can travel that result in the intensity going up and down. Because EM radiation travels in straight lines, this data gives a good starting reference as to the probable direction of the source. Assuming no other factors, make you way out of the zone, using the dosimeter to continuously confirm that the radiation intensity is going down. If it begins to go up, repeat the process and adjust course.

Be aware that dense objects such as buildings, structures and topography directly in the path of the radiation can give you a false sense of the correct direction. You may progress in the dense object’s ‘shadow’ right up to it without noticeable change to the intensity readings, only to find much higher intensities as you come around the structure.

Best practice if you take a step forward and the intensity jumps up, is to take a step back, then reassess before moving any further.



These are just a few things you need to know about radiation safety. In the event of a radiological emergency, it's important to get away from the source of radiation as quickly as possible, and failing that, shelter in place and prepare your dwelling to resist ingress by radioactive fallout. It's also important to wear a dosimeter so you can monitor exposure levels and locate the safest route of egress from a radiation zone.

By taking these steps, you'll be better prepared in the event of a radiological emergency.

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