FAQS

Q: If all vendor dosimeters are NVLAP accredited, why should I go with CHP Dosimetry?
A: CHP Dosimetry gives you fast, personalized service, the kind of service big vendors offer their largest customers. In addition, we have Certified Health Physicists on hand who can help you choose the appropriate dosimeters and help you deal with regulators, should you need it. We provide this high level of service at a lower cost! We can do this because we keep our overhead low. We are located in Oak Ridge, TN, the "Secret City" and birthplace of radiation dosimetry. So, when you have a technical question, you talk with one of our Health Physicists – without having to fight your way through customer service!

We are a full service personal dosimetry company. If your employees are exposed to internal radiation [dose], we have Certified Health Physicists who can assess that for you too. If you have other [problems or] concerns related to radiation safety, we can refer our parent company, CHP Consultants, which provides radiological instrumentation, health physics, nuclear safety, shielding, and safety support services.

Q: What is a Thermoluminescent Dosimeter (TLD)?
A: TLD Dosimeters are one of the most advanced applications of Thermoluminescent Detectors. Modern TLD Dosimeters measure the Skin Dose, Eye Dose and Deep Dose specified in current regulations, in addition to the total dose from other nuclear particles. They consist of at least four separate TL detectors, which allow for discrimination of photon energies and the nature of the incident radiation. For more information, visit the Nukeworker site: Everything you wanted to know about TLD but were afraid to ask.

Q: How can you report LOWER doses than my current dosimetry provide?
A: Unless you are using a Panasonic 802 or other dosimeter utilizing lithium borate (Li2B4O7), your dosimeter is less tissue-equivalent than our whole body badge. This means that in order for the dosimeter to report the dose to your body (tissue), correction factors are required. On a less tissue equivalent dosimeter, these correction factors are needed to account for an order of magnitude difference (over 10 times!!) in response of the dosimeter higher than it would if it were tissue equivalent. At the testing laboratory, these correction factors work well. The problem comes in the fact that we wear dosimeters in the REAL world. For instance, radiation exposure may come from the side or back, bypassing the filters installed over their elements. The detector doesn't know where the signal came from so it assumes the radiation passed through the filters which will result in a higher than actual dose (the dosimeter thinks it is a higher energy radiation so it multiplies the resulting dose). This is particularly evident when exposed to X-rays such as during fluoroscopy procedures (as if the dose isn't high enough already...).

Q: Why does Tissue Equivalence matter?
A: The first thing they teach you in Health Physics is that your purpose is to measure the impact of radiation on PEOPLE. What dose does a person receive? You then learn about the ideal detector. This detector would respond to radiation the exact way that tissue does. Unfortunately there are no practical radiation dosimeters made from tissue, so the quest then becomes to make a detector that closely approximates the atomic composition of tissue. Hence the tissue equivalent dosimeter. CHP dosimetry uses the Panasonic 802 dosimeter. Lithium Borate has an effective atomic number (Z) of 7.23, this agrees closely with the value of 7.22 for soft tissue. Lithium Fluoride (LiF) has an efffective Z of 8.14 and aluminum oxide (Al2O3) is 10.65! What this means is that these less tissue equivalent dosimeters are more likely to over-respond to X-rays and lower energy photons yielding a higher than actual dose.

Q: Why doesn't my vendor offer the Panasonic Dosimeter?
A: The big vendors use dosimeters that either make their operations easier, or the ones they manufacture themselves. Basically they do it because it is easier or less costly for them to use what they have, and they think you don't know any better.