CRPA(R) Prep, June 2019 / Préparation à la désignation (A)ACRP, juin 2019
In this section of the Bulletin, we introduce a question or two similar to the questions on the CRPA(R) exam. In the next issue, we will provide the solution. The intention is to give people an idea of the types of questions that we use on the CRPA(R) exam and perhaps convince more members to challenge the exam.
If you already have your CRPA(R) designation, we invite you to submit questions to earn points for your registration maintenance!
Question from the last issue:
So, let’s take a look at the solution to the question from the last issue.
The amount of light emitted by a scintillation phosphor is proportional to what feature of photon energy?
As the CRPA Professional Registration Process document shows, an entire section of the CRPA(R) exam is dedicated to instrumentation and equipment. Obviously, when we are testing knowledge in this area, we can’t ask you to work out a mathematical solution. Instead, we try to gauge whether you have the knowledge that is expected of someone who is a CRPA(R).
The Registration Process document also includes a suggested reading list with many reputable sources for information about radiation detection and instrumentation. One of the references is the book Radiation Detection and Measurement by Glenn Knoll. (I used this book to prepare for the CRPA(R) exam.) In the book, Knoll describes ideal scintillation material as having specific helpful properties for radiation detection. One of the more important properties of scintillating material is that it should convert the kinetic energy of charged particles into detectable light with high scintillation efficiency, and the light yield should be proportional to deposited energy.
Another suggested reference in the Registration Process document is the Cember classic Introduction to Health Physics. In this book, Cember talks about the ability of scintillating material to convert energy absorbed to light. When this light strikes a photocathode, electrons are released to a photomultiplier tube, after which the signal is measured.
So, armed with what we learned from studying the suggested reference material, we know that the amount of light emitted is proportional to the energy deposited in (and, for the most part, absorbed by) a scintillating material. That leads us to the answer to the question from the last issue:
What is the net count rate in counts per minute (cpm) given the following information?
- Removable activity 3 Bq/cm2
- Area wiped 100 cm2
- Collection factor for the wipe 10%
- Instrument efficiency 50%
a. 15 cpm
b. 900 cpm
c. 90 cpm
d. 150 cpm
1. Knoll, G.F. (2000). Radiation Detection and Measurement (4th ed.). Hoboken, NJ:
John Wiley & Sons.
2. Cember, H., & Johnson, T. E. (2008). Introduction to Health Physics (4th ed.). New York, NY: McGraw-Hill Medical.