4. IONISING RADIATION: MEASUREMENTS AND STANDARDS Flashcards
1
Q
- What is necessary to have when using Ionising Radiation?
A
- a method for detecting and recording its presence
2
Q
- Can ionisation be identified directly?
A
- NO
- we need the radiation to interact with another material
- this produce an effect
- this effect can be detected
3
Q
- Who is the Father of Radiology?
A
- Wilhelm Conrad Röntgen
- he is a mechanical engineer and physicist
4
Q
- When did Wilhelm discover X-Rays?
A
- in 1895
- on the 8th of November
- he did this accidentally
5
Q
- What did Henri Becquerel discover in 1896?
A
- he discovered radioactivity
- he did this when he accidentally detected radiation
6
Q
- What two methods did Becquerel use to detect ionising radiation?
A
- Film
- Electroscope
NB:
- both cases involve the interaction of radiation with
another material
- this allows for it to be detected
NB:
- both are still commonly used today
7
Q
- Why do we need to be able to calculate Dose Rate immediately?
A
- this allows us to calculate the accumulated dose
- this gives us a warning if the dose rate becomes very
high
8
Q
- What is a Dosimeter?
A
- this is an instrument that measures ionising radiation
9
Q
- What does a Dosimeter comprise of?
A
- it comprises of a measuring assembly
(this is often referred to as an electrometer) - it has one or more detector assemblies
(these may or may not be an integral part of the
measuring assembly)
10
Q
- What are Monitoring equipments often calibrated in?
A
- they are calibrated in terms of:
- mrad/h
- μGy/h
- centigrade / hour
11
Q
- How are low levels of dose rate measured?
A
- using a Geiger-Muller (G-M) tube
- using Scintillation Counters
12
Q
- What is an Ionisation Chamber?
A
- this is another way of measuring Dose Rates
- it is more accurate
- it is less affected by Radiation Energy
13
Q
- What is another advantage of the Ionisation Chamber systems?
A
- they can measure high dose rates
- this would saturate other monitors
14
Q
- What is the standard instruments for measuring dose rates?
A
- it is usually the Ionisation Chamber System
15
Q
- Why is it desirable to be able to monitor dose and dose rate with an instrument which can be worn on the body?
A
- we can use them to measure the ionising radiation
received by different doses in different parts of our
body
16
Q
- Name two examples of measuring methods that can be worn on the body.
A
- Pocket Dosimeters
- G-M Tube Instruments with a dose rate alarm
17
Q
- Why are Solid-State detectors and Scintillation Counter Systems not suitable for routine dose measurements?
A
- they are relatively expensive
18
Q
- What is currently the cheapest and most commonly used way to measure Radiation dose?
A
- personal monitors
- these use Thermoluminescent Dosimetry (TLD)
19
Q
- What is slowly replacing Thermoluminescent Dosimeters (TLDs)?
A
- Ionisation Chamber Dosimeters
- this is because TLDs are passive dosimeters
- they cannot provide direct measurements of ionising
radiation
20
Q
- What is the safety hazard with Dosimeters?
A
- they offer no active protection or mitigation from
harmful radiation - they do not alert individuals when they are exposed to
high doses - they are not radioactive themselves
21
Q
- List the 4 Advantages of Film Dosimeters.
A
- A FILM BADGE
- that acts as a personal monitoring device
- is very simple
- it is not expensive
- A FILM BADGE
- provides a permanent record
- FILM BADGE DOSIMETERS
- are very reliable
- A FILM BADGE IS USED TO:
- measure and record radiation exposure
- this radiation exposure is due to Gamma Rays, X-
Rays and Beta Particles
22
Q
- List the 3 disadvantages of Film Dosimeters.
A
- FILM DOSIMETERS USUALLY CANNOT BE READ ON
SITE- they have to be sent away for developing
- FILM DOSIMETERS ARE FOR ONE TIME USE ONLY
- they cannot be reused
- EXPOSURES OF LESS THAN 0.2 mSv OF GAMMA
RADIATION- this is 20 millirem of Gamma Radiation
- this cannot be actively measured
23
Q
- List the 4 Advantages of TLD Dosimeters?
A
- TLDs
- are able to measure a greater range of doses in
comparison with film badges
- are able to measure a greater range of doses in
- DOSES FROM TLDs
- can be easily obtained
- TLDs CAN BE READ ON SITE
- they usually do not have to be sent away for
developing
- they usually do not have to be sent away for
- TLDs
- are easily reusable
24
Q
- List the 2 disadvantages of TLDs?
A
- EACH DOSE
- cannot be read out more than once - THE READOUT PROCESS
- effectively zeroes the TLD
25
Q
- What is an Electronic Personal Dosimeter?
A
- it is a high range dosimeter
- it is alarming
- it is active
26
Q
- What was an Electronic Personal Dosimeter designed for?
A
- it was designed to be worn by occupational Radiation
Workers in planned exposure situations - it is meant to measure personal dose equivalence for
regulatory compliance
27
Q
- In which 2 settings are Electronic Personal Dosimeters used?
A
- Industrial
- Medical
28
Q
- What does the Electronic Personal Dosimeter display?
A
- it displays dose and dose rate
- this is because it has a high level of Radiation
sensitivity
