What Is a Dosimeter And How Does It Work?

Resource Description

A dosimeter is a device applied for determining ionizing radiation release. It is a significant device for the worker who operates in a situation where they are exposed to radiation.

Dosimeters are applied to ensure that a harmful dose of radiation is not received over the needed time. Radiation is harmful to human health and may be deadly when people are exposed to a high level of radiation. Dosimeters alert workers when the radiation level is too high so that they can leave the release area and be protected from radiation poisoning.

Types Of Dosimeters

There are two major types of dosimeters:

Passive dosimeters generate a radiation-induced signal that is retained in the device. The dosimeter is then converted and the output is examined. The most commonly applied passive dosimeters are Noise Badge and Thermo Luminescent (TLD) dosimeters.

Noise Badge Dosimeters

Noise badge dosimeters generate sound level determinants through the Bluetooth wireless connection. These dosimeters will alert workers through the free Airwave App by sending the readings to the Apple or Android device. The noise badge dosimeter is ideal for hazardous areas. It should be worn to the chest on the external side of clothing.

TLD - Thermoluminescent Dosimeter

A thermoluminescent dosimeter also known as TLD is a passive radiation dosimeter that determines ionizing radiation released by determining the intensity of the visible spectrum emitted from the sensitive crystal in the detector when this crystal is heated. The power of the emitted light is determined by a TLD reader and it is independent of the radiation release. Thermoluminescent dosimeters are used where present time information is not needed, but accurate accumulated dose monitoring records are required for field determinant comparison or evaluation of the potential for long-term health effects.

Mosfet Dosimeter

Mosfet dosimeter is a small portable device for monitoring and directly reading radiation dose rates. Since it is based on the MOSFET transistor, the principle of operation is similar to semiconductor detectors. Such types of dosimeters are also known as clinical dosimeters for radiotherapy radiation beams. The main benefit of this dosimeter is the physical size, which is less than 4mm2. In radiation therapy dosimetry, MOSFET dosimeters frequently exchange TLD dosimeters.

Active Dosimeter is a device that will provide a real-time value of the exposure. The device generates a radiation-induced signal and displays the direct reading of the detected dose in real-time. To achieve a real-time value of the exposure you may use the electronic personal dosimeter (EPD).

EPD - Electronic Personal Dosimeter

An electronic personal dosimeter is an innovative dosimeter that can provide a constant reading of the increasing dose and current dose rate and can alert the user wearing it when the specific dose rate or an increased dose is exceeded. EPD is specifically useful in high-dose areas where the residence time of the user is limited because of dose constraints.

The EPD may display a direct reading of the detected dose or dose in real-time. Electronic dosimeters can be applied as supplemental dosimeters as well as major devices. The passive dosimeters and the electronic personal dosimeters are usually applied together to complement each other.

The passive and the active dosimeters are commonly applied together to complete each other. To evaluate efficient doses, a dosimeter should be worn on the body, generally between the waist and the neck, and facing the radioactive source. It is recommended to wear dosimeters on the external side of clothes, around the chest, to determine the radioactive dose of the whole body.

Self-Reading Dosimeter

Self-reading dosimeter is a field-readable device that is worn on the body to determine the accumulated dose. This is an unpowered device that doesn't include a battery.

Devices in this group include:

A quartz fiber dosimeter also known as a self-indicating pocket dosimeter is a pen-shaped device that allows determining the increasing dose of ionizing radiation received by the device, generally over one work period.

Self-developing photochemical cards have the size of a simple credit card and are applied for instant color-developing emergency dosimeters. It is produced for regulating the exposure in radiological incidents for medical treatment purposes and to lessen worry and panic.

DIS Dosimeter

DIS dosimeter (direct-ion storage dosimeter), is an electronic device, from which the dose information for both Hp(10) and Hp(0.07) may be generated at once at the workplace by applying the electronic reader unit. This type of dosimeter is based on the ion chamber and non-volatile electronic charge storage element combination. Dis dosimeter uses the analog memory cell inside the small, gas-filled, ionization chamber. Incident radiation causes ionizations in the chamber wall and the gas, and the charge is retained for followed reading. The DIS dosimeter may be read by the connection to the electronic reader unit

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A pen dosimeter is a device that determines the dose of radiation effect to be indicated more precisely. It measures and reads accumulated doses of radiation exposure directly. A radiation dosimeter is a sturdy metal clip that fixes the dosimeter to the pocket or any object to regulate total radiation exposure.

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How Does A Dosimeter Work?

Extended exposure to X-rays, gamma rays, and specific radioactive particles lead to ionizing radiation. This radiation has the potential to block electrons in normally stable molecules through its energy. Likewise, if this appears with living tissues, this lack of electrons will lead to a lot of damage.

Nevertheless, you may capture and determine these unmonitored electrons providing the right circumstances. As a result, the unmonitored electrons by ionizing radiation can be seized within phosphor crystals, like those that represent dosimeters. If you heat the phosphor crystals that capture electrons, they will release in the form of light. It will help to determine the radiation the dosimeter was exposed to.

What Is Radiation Detector

Radiation detectors also known as radiation devices are instruments that sense and measure radiation emissions or levels of radiation generated by the source. Radiation detectors may be divided by the types of radiation they measure.

The most common radiation types:

Gas-filled radiation detectors operate based on the ionization effect that appears when radiation passes through the air or specific gas.

Scintillation radiation detectors apply the level of light energy generated when radiation interacts with a material to ultimately establish the level of radiation. The scintillator light flashes may be brief in their duration, which allows for the radiation detector to measure large numbers of particles in a short time period.

Solid-state radiation detectors work by using ionization principle within a semiconductor device containing two types of materials: n-type ( has more electrons than holes)and p-type (has more holes than electrons).

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What Is Radiometer

The radiometer is a specific light-bulb-shaped device that includes an object similar to the weather vane. The radiometer improved to determine the intensity of radiant energy or heat will help to determine the principle of energy conversion and how heat and mechanical energy are products of energy conversion. One of the reasons you should take energy for granted is that it constantly changes from one form to another which is called a conversion. During the conversion, the energy changes from one form to another. In all energy conversion, the useful energy output is less than the energy output. This is because some energy is applied to do work, and some energy is converted to heat.

How does the radiometer work?

When the light strikes the surface, some of the light is absorbed and transformed into heat, while some of it is reflected. The radiometer includes four panels mounted on a pin-tip so it can spin freely. One side of each panel is black, and the other sides are bare metal. The air is removed from these four panels. The panels may spin quite freely. The remaining air is in contact with the panels’ surfaces. The air that is connected with the black side gets heated more than the air that touches the metal surface. The hotter the air the greater the pressure and the stronger the push on the black side of the panel than on the metallic side. As a result, the array of panels starts spinning. The more intense the radiation, the more energy is transferred to the panels and the faster the array spins.

Where Are Dosimeters Used?

Dosimeters are most commonly used by professionals in industrial and medical applications and also by radiation emergency workers such as HAZMAT professionals.

Typical applications where dosimeters are used are

  • Nuclear power;
  • Radiology;
  • Oncology;
  • Nuclear medicine;
  • Construction;
  • Maritime;
  • Public safety.

Workers use personal radiation dosimeters to determine increasing radiation dose exposure. Several dosimeters may warn about the use of extremely harmful doses of radiation when others are parts of the increased radiation dose regulation and protection program.

First workers and HAZMAT professionals will be alerted about the radiation emission. So, the radiation regulating zones are established to determine the radiation and protect workers from high radiation doses.

There are three main regulation zones when processing the radiation incident:

The cold zone is a pollution-free area that encourages operations and critical planning to eliminate radiation from the emergency incident. The radiation level is at the background dose in this area.

The warm zone is the depollution area and is set up between the cold and hot zones.

The hot zone surrounds the radiation scene right away. Proper personal protective equipment (PPE) is strictly required here.

Personal radiation dosimeters are used by emergency professionals in these regulating areas and will be alerted when radiation levels are hazardous.

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