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Radiation Protection > Test 3 - Radioactivity Detectors > Flashcards

Test 3 - Radioactivity Detectors Flashcards

1
Q

C-14

A

5730 yrs, max E = 156 keV

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2
Q

H-3

A

12.4 yrs, max E = 19 keV

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3
Q

I-131

A

8.07 days, max E = 806 keV

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4
Q

I-125

A

60 days, max E = 35.49 keV

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5
Q

P-32

A

14.3 days, max E = 1709 keV

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6
Q

S-35

A

87.5 days, max E = 167 keV

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7
Q

Cl-36

A

3x10^5 years, max E = 709 keV

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8
Q

Liquid scintillation materials

A
  1. Emulsifying and aqueous - safer and organic. Scintillator & emulsifier.
  2. Organic and non-aqueous - organic aromatic solvent. Scintillator only.
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9
Q

Types of Quenching

A

Chemical, color, dilution, photon

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10
Q

Quenching

A

When competing radical-forming chemicals or photon-absorbing materials are present in the solution, or when photon escapes, quenching (incomplete transfer of energy) occurs.

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11
Q

Chemical quenching agents

A

Nitromethane, chloroform, carbon tetrachloride, acetone

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12
Q

DPM vs CPM

A

Decay per minute is a 100% efficient Counts per minute. Or, CPM x 100% / DPM = % counting efficiency.

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13
Q

LSC Advantage / Disadvantage

A

Advantage: small sample size okay, mixture of B distinguishable, short preparation. Disadvantage: expensive, bulky, and calibration required

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14
Q

Liquid scintillation counting

A

Technique of measuring photoelectron emission from beta source in liquid scintillator with two opposing PMT. Current in PMT corresponds to energy. Gamma source will not work (escapes easily).

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15
Q

Quench curve

A

Curve of CPM vs energy (so spectrum) with varying degrees of quenching. More quenching = lower counts.

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16
Q

Quench indication parameter

A

Efficiency of counting can be calculated with this parameter.

17
Q

tSIE

A

Transformed spectral index of external standard. Uses Ba-133 to assign a numerical value to quench amount. THE LOWER THE tSIE THE MORE THE SAMPLE IS QUENCHED. Most accurate measure of quench so far.

18
Q

Gas-filled detectors (ionization chambers)

A

Ionization chamber, low V. Uses gases (Argon, halogens, organic gas) to monitor ionization, aka exposure. Specific geometry used, like cylinder or sphere. Convert to mR/hr.

19
Q

Proportional counters

A

Still ionization chamber, but higher V. Uses special gases, like argon-methane mixture. Response proportional to initial ionization. FOR ALPHA AND BETA COUNTING.

20
Q

Geiger-Muller detectors

A

Still ionization chamber, very high V. FOR HIGH-ENERGY BETA/GAMMA (P-32, I-131). Trouble detecting low E beta/gamma, because of over-sensitivity to low E beta/gamma.

21
Q

Geiger Counter windows

A

Pancake (large face), end (detector at end of rod), side (detector at side of rod)

22
Q

Solid Scintillator counters

A

Portable or stationary. Recommend for gamma emitters like I-125.

23
Q

H-3 detection is only possible with?

A

Liquid scintillation counters.

24
Q

What detectors are best for dose rate calculations?

A

Ionization chambers or tissue-equivalent organic scintillators. At high dose rate, only ionization chamber is useful. PGM (pancake geiger-muller) useful in an emergency.

25
Q

What detectors are best for contamination survey?

A

GM for high-energy gamma and liquid scintillator for H-3.

26
Q

What detectors are best for ID of source?

A

Liquid scintillator, well counter, gamma counter (which is energy-resolved!), portable Multi-Channel Analyzer (MCA)

27
Q

CPM versus DPM on regulations?

A

USE DPM. CPM is area-dependent, distance-dependent, and yield-dependent value.

28
Q

Liquid scintillator false positives

A

Liquid scintillators can give false positives when photoluminescence (lasting ~1 min), chemoluminescence (lasting hours) interfere with radioactivity.

29
Q

Gamma counter

A

ENERGY RESOLVED counting of gamma, similar preparation as liquid scintillator (blanks in vials). ONLY good for GAMMAS: I-125, I-131, and 51-Cr. No liquid scintillator required (PMT directly picks up the gamma), and NO false positives.

30
Q

Multi-Channel Analyzer (MCA)

A

Cadmium Tellurium (CdTe) detector. Many bins for each energy range.

31
Q

Personal Monitoring of Raditation for workers

A

Film, TLD, Electronic, OSL.

Radiation Protection (4 decks)

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