Answer to Question #11358 Submitted to "Ask the Experts"

I have flown the polar route for many years as a flight attendant and would like to purchase a suitable, practical device for measuring my in-flight radiation dose. The “Instrumentation and Measurements” category of the Health Physics Society’s Ask the Experts feature mentions that one can purchase dosimeters, but that to be relevant they must contain a “suitable” neutron measurement system. What would you consider suitable?

It is true that the neutron contribution to in-flight dose may be a significant portion of your total in-flight dose. As such, if you are intending to measure your occupational dose you would be wise to use a device that measures both photon (gamma and x ray) and neutron radiation doses. There are numerous vendors who provide dosimetry services that include these radiations. Typically they operate by providing each user with a badge that is sent back to the vendor for processing on a regular basis (e.g., monthly or quarterly), and a recurring fee is charged for the service. The user does not purchase the dosimeter, but rather purchases the service in which the vendor provides the dosimeter on a temporary basis. Most vendors prefer to work with companies that employ multiple users, and this helps keep the cost to the employers lower. As a single individual you would have to speak with company representatives to determine availability and cost for a suitable service.

I am listing links to some vendors below, but these are simply representative and not intended as recommendations by me or by the Health Physics Society. All of those listed do include neutron capability in their dosimetry services, although different techniques may be used by different vendors. You can find others by searching for dosimetry vendors on the internet. You might also find some useful contacts through the Health Physics Society's Buyers' Guide.

The dominant neutron dosimetry techniques involve either (1) the use of thermoluminescent dosimeters (TLDs) that rely on the reflection and slowing down of neutrons in the user's body to produce a response or (2) the use of prepared plastic films, called track-etch detectors, that record damage tracks from fast neutrons incident on the films. With track-etch detectors, the damage tracks are etched to make them visible for assessment. CR-39 is the most common commercial product used in track-etch detectors.

For your application I would suggest the track-etch detector over the TLD because the TLD shows rather extreme neutron-energy dependence. With a TLD, you would likely have trouble establishing an appropriate calibration so that the vendor could use an appropriate dose-conversion factor.

Some vendors and the dosimetry services they provide include the following:

• Landauer (track-etch detector)
• Mirion Technologies (TLD)
• Sierra Radiation Dosimetry Service (TLD)
• Stanford Dosimetry (track-etch detector)
• MP Dosimetry (track-etch detector)
• Panasonic (TLD)

The kinds of dosimeters noted above are passive devices; i.e., you use them, they provide a response to incident radiation, and you send them to the vendor who will interpret the relevant dose(s) from the response(s). There are also available active electronic dosimetry devices, which one can purchase from manufacturers. These show dose responses that can be read from the devices in real time so that the user has an immediate indication of dose received. The most common of these are designed for photon dose measurements, but there are also some neutron-measuring devices available. Mirion Technologies (listed above) is one company that provides such devices. Each such electronic device may cost several hundred dollars.

I do not know what policy your airline has established with regard to considerations of flight employee doses and the assessment of such, but it may be worthwhile discussing your concerns with your managers to determine whether they would be willing to provide the dosimetry.

If you do talk to vendors, make sure you explain your needs, telling them your intentions and how the dosimeter will be used. I hope you are able to get your needs addressed and that you are able to obtain meaningful assessments of your in-flight doses.

George Chabot, PhD