CRPA(R) Prep, December 2018 / Préparation à la désignation (A)ACRP, decembre 2018
In this section of the Bulletin, we introduce a question or two similar to the questions on the CRPA(R) exam, then we go through the solution in the next issue. We are hoping to give people an idea of the types of questions that are seen on the CRPA(R) exam and maybe, just maybe, convince more members to challenge the exam.
If you already have your CRPA(R) designation, we invite you to submit questions to be used in this column to earn points for your credential maintenance!
Question from the last issue:
The question from the last issue was our first non-calculation question.
What is the typical range of dose measurements possible for a thermoluminescent dosimeter (TLD)?
a. 0.01 à 0.1 mSv
b. 0.1 à 10 mSv
c. 1 à 100 mSv
d. 10 à 100 mSv
Some of the wily radiation safety veterans out there will simply know the answer through operational experience. But, what if you are not involved with the dosimetry program or you just can’t remember the answer? How can we figure this out?
Well, there are many different TLD configurations for different scenarios (including special ones for high-dose and low-dose operation). The key word to figuring out the answer is “typical.” What is the range for typical TLDs used at various facilities?
When you write the CRPA(R) exam, you are given a copy of the most recent regulations under the Nuclear Safety and Control Act. Among the radiation protection regulations in Section 8 is the following statement:
Every licensee shall use a licensed dosimetry service to measure and monitor the doses of radiation received by and committed to nuclear energy workers who have a reasonable probability of receiving an effective dose greater than 5 mSv in a one-year dosimetry period.
From that, we know our dosimeter needs to read in the 5 mSv range. Obviously we would want TLDs to cover this required range, so we can eliminate answers a (0.01 to 0.1 mSv) and d (10 to 100 mSv) as they are out of the required range.
Looking at the ranges of the two remaining choices, we should note that the range in answer c (1 to 100 mSv) is well over the annual regulatory dose limit of 50 mSv (also found in the Radiation Protection Regulations). So, the typical (most widely used) range is answer b (0.1 mSv to 10 mSv). Many dosimetry service providers quote 0.1 mSv as the minimum reportable dose for their TLD badges.
Even if you have no idea how to answer questions that do not require calculations, you can often use the resources provided to come up with a solution.
What is the transport index for a small package (less than 1 m2 cross-sectional area) being shipped as a Category III – yellow with the following dose rates?
- Surface = 510 µSv/h
- 1 metre from surface = 43 µSv/h
- 10 metres from surface = 0.5 µSv/h