Dosimetry

What is dosimetry?

Dosimetry is an accurate and systematic measurement of the absorbed dose in matter and tissue resulting from exposure to ionizing radiation.

Radiation Detection Company measures radiation exposure using thermoluminescent dosimeters. These dosimeters contain four separate phosphors. The badges are read with control values that are subtracted from the personnel badges. An algorithm then selects the correct energy the badge was exposed to in order to apply the appropriate dose.

When the thermoluminescent phosphors within the dosimeter are heated, the previously absorbed energy from the ionizing radiation is released in the form of light. We can accurately measure the light output with a device called a photo-multiplier tube. The signal from the photo-multiplier tube is then used to calculate the dose that the material had absorbed.

The type of radiation each badge is exposed to is determined through energy discrimination from filtration between the source and the phosphor material. As the radiation passes through the filters, some of the energy is shielded. Using the ratio response of the four phosphors, we can determine your proper dose.

All of our dosimeters contain either lithium fluoride, or lithium borate phosphors. Unlike aluminum oxide, these phosphors are considered tissue equivalent. This means we can accurately determine your dose using phosphors that respond to radiation almost exactly the way the tissue in your body does.

What is neutron dosimetry?

While the Panasonic 802 dosimeter that we utilize for gamma, beta, and x-ray radiation exposure does give a neutron signature, we do not report neutron readings from this dosimeter. Instead, we offer the same dosimeter with the addition of a track-etch element. This dosimeter type is referred to as an 83 badge.

The track-etch element is essentially a small piece of plastic that becomes pitted by neutron radiation as it passes through the badge. These pits are expanded using an etching process and counted under a microscope with an automated reader. This process is typically more accurate than using thermoluminescent dosimeters for neutron dosimetry.

Moisture or density gauges, containing americium-241, is mixed with beryllium to produce neutrons. It is the thermalization of these neutrons that provides an estimate of moisture or density.

Due to the high kinetic energy of neutrons, this radiation is considered to be the most severe and dangerous type of radiation. It is very important to have the right type of dosimeter when working with neutron radiation.

Who is required to be monitored?

All employees who may receive 500 mrem in one year must be badged. In addition, all declared pregnant workers must be monitored.

What does ALARA stand for?

ALARA in an acronym for "As Low As is Reasonably Achievable".  According to the NRC Regulations Title 10, Code of Federal Regulations, ALARA means making every reasonable effort to maintain exposures to radiation as far below the dose limits in this part as is practical consistent with the purpose for which the licensed activity is undertaken, taking into account the state of technology, the economics of improvements in relation to state of technology, the economics of improvements in relation to benefits to the public health and safety, and other societal and socioeconomic considerations, and in relation to utilization of nuclear energy and licensed materials in the public interest. 

What is a Passive Dosimeter?

A passive dosimeter absorbs radiation over time and can quantify the absorbed dose when it is processed or "read".

What is a TLD?

A thermoluminescent dosimeter, or TLD, is a type of radiation dosimeter. A TLD measures ionizing radiation exposure by measuring the amount of visible light emitted from a crystal in the detector when the crystal is heated. The amount of light emitted is dependent upon the radiation exposure. 

What kind of dosimeters do you use?

RDC uses the Panasonic UD-802 dosimeter (for photons and beta radiation and PN-3 for neutron monitoring). This dosimeter has been the dosimeter of choice in the critical nuclear power environment since the 1980's and is a well-known and very capable dosimeter.

With four individual detectors and filters, the badge design allows excellent photon discrimination. The use of the relatively tissue-equivalent lithium borate phosphor, means that the detectors require small correction factors, resulting in more precise, less error prone results than most other dosimeters.

We also offer finger ring dosimeters comprising a single element dosimeter contained in a waterproof, soft comfortable plastic (PVC) pouch on an adjustable plastic strap, adjustable from size 6 to 14. The finger ring is recommended for clients whose extremities are exposed to X-ray beams or who directly handle radioactive materials.

Who benefits from radiation monitoring?

Every employee monitored is a beneficiary as they work with peace of mind knowing that their health is not at risk.

Every company owner is a beneficiary as documented occupational dose monitoring provides protection against current and future legal employee health claims so long as the owner is able to show documented evidence that his/her employees did not exceed their occupational dose limits during their term of employment. This is why records should be kept for the lifetime of the business.

Providing workers with individual personal radiation dosimeters is about more than meeting regulations. It gives both worker and employer peace of mind knowing that radiation exposure is constantly being monitored with a fully accredited dosimeter.

Do we need dosimetry badges if we are using a digital X-ray machine?

Yes. Digital x-ray machines do not require film, but still produce the same risk of exposure as any other x-ray machine.

How can liability be limited in the workplace?

Responsibility for damage caused by exposure to radiation in the work place is most often assigned to the employer. Employers utilizing sources of radiation in their business are required by the NRC to have a license permitting safe use of their source. Exposure to hazardous radiation is governed by laws that are designed to protect employees through safe handling and use of radioactive sources. Radiation damage experienced by employees is often an indication of failing to abide by these laws which leaves the employer exposed to legal liability for the damage caused. Developing and implementing a radiation safety program which includes documented occupational dose monitoring will assist employers in limiting their exposure to liability in the workplace.

Why should I continue with my badge service after I have completed the state’s monitoring period and saw no dose on the report?

If there is a malfunction in your equipment and you have discontinued monitoring for radiation exposure, you may never know that your health and/or the health of your employees were compromised. Continuous monitoring for radiation exposure not only allows you to protect the health of you and your employees, but it also helps you to protect your business from liability should a lawsuit be filed by an employee who claims they received excessive radiation while under your employment.

Am I required to provide monitoring for a minor?

A minor cannot be a “Radiation Worker”.  While one may elect to provide a badge for a minor, they are prohibited from working with radioactive materials.   In this case, the minor would be badged as a “Member of the Public” only.  The dose limit for a “Member of the Public” may not exceed 100 mRem per year.

What is the definition of Health Physics?

The science concerned with the recognition, evaluation, and control of health hazards to permit the safe use and application of ionizing radiation.

What is a Leak Test?

Licensees who use sealed sources must have the source tested periodically for leakage. The wipe of a sealed source must be performed using a leak test kit. The sample must be analyzed for radioactive contamination. The analysis must be performed by a person approved by the NRC or an Agreement State.

Can I breastfeed after being exposed to x-ray radiation?

Yes, it is perfectly safe for a breastfeeding mother to perform, or receive any kind of X-ray procedure. X-ray radiation can kill living cells, but this does not affect the milk, nor does it expose the baby to any type of radiation. An x-ray machine only presents a hazard when it is energized, once the machine is turned off, a human being will not store, or emit ionizing radiation.