Radiation Detection Instrumentation Radiation Safety Program Annual Refresher Training Click NEXT.

Radiation Detection Radiation Detection InstrumentationInstrumentation

Radiation Safety ProgramRadiation Safety ProgramAnnual Refresher TrainingAnnual Refresher Training

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UCLA Radiation Safety Annual Refresher TrainingUCLA Radiation Safety Annual Refresher Training

Personnel working with radioactive materials Personnel working with radioactive materials are required to complete annual refresher are required to complete annual refresher training and submit documentation of training and submit documentation of completion to Radiation Safety by the end of the completion to Radiation Safety by the end of the calendar year. This module may be used as one calendar year. This module may be used as one option for completion.option for completion.

Annual Refresher Training Annual Refresher Training

UCLA Radiation Safety Annual Refresher UCLA Radiation Safety Annual Refresher TrainingTraining

Humans do not possess the ability to detect Humans do not possess the ability to detect ionizing radiation with their 5 senses. ionizing radiation with their 5 senses.

Therefore, we must rely on instrumentation Therefore, we must rely on instrumentation for both the detection and measurement of for both the detection and measurement of ionizing radiation.ionizing radiation.

Radiation MeasurementsRadiation Measurements

In this training we will cover:In this training we will cover:Radiation detector theoryRadiation detector theoryCommon types of detectors at UCLACommon types of detectors at UCLAAnnual calibration requirementsAnnual calibration requirements

AgendaAgenda


Radiation Detection PrinciplesRadiation Detection Principles


There are several common sources of electrical There are several common sources of electrical energy such as friction, heat, pressure, and energy such as friction, heat, pressure, and magnetism.magnetism.

Ionizing radiation is also a source of electrical energy Ionizing radiation is also a source of electrical energy and can be used to quantify radioactivityand can be used to quantify radioactivity

Radioactive decay products such as alphas, betas, and Radioactive decay products such as alphas, betas, and gammasgammas

Electrical EnergyElectrical Energy


There are 3 elements to a radiation detection system:There are 3 elements to a radiation detection system:Measurement/DetectionMeasurement/Detection

Dependent on radiation type & intensityDependent on radiation type & intensity

Detector functionDetector function Interaction between detector material and incident radiation to Interaction between detector material and incident radiation to

produce an observable effectproduce an observable effect

Readout circuitryReadout circuitry Analyzes the produced effectAnalyzes the produced effect

Radiation Detection SystemsRadiation Detection Systems


Ionization detectors (gas-filled or solid)Ionization detectors (gas-filled or solid) Incident radiation creates ion pairs in the detector materialIncident radiation creates ion pairs in the detector material

Excitation detectorsExcitation detectors Incident radiation excites the atoms in the detector material and Incident radiation excites the atoms in the detector material and

emits visible lightemits visible light

Detector TypesDetector Types


As all detectors measure radiation as a function of As all detectors measure radiation as a function of its observed effects, a correlation must be made its observed effects, a correlation must be made between the effect and the incident radiation.between the effect and the incident radiation.

Factors that affect this correlation are:Factors that affect this correlation are: Detector size & shapeDetector size & shape Detector material characteristicsDetector material characteristics Radiation energyRadiation energy Probability of ionizationProbability of ionization

Quantifying RadiationQuantifying Radiation


Gas-Filled DetectorsGas-Filled Detectors


Comprised of:Comprised of: the detector gas or gas mixtures which can be ionizedthe detector gas or gas mixtures which can be ionized electrodes which collect the ion pairs produced from the gaselectrodes which collect the ion pairs produced from the gas high voltage supply that amplifies the signalhigh voltage supply that amplifies the signal

In a gas-filled detector, it is the magnitude of the In a gas-filled detector, it is the magnitude of the voltage placed between the electrodes that will voltage placed between the electrodes that will determine the type of response to each radiation determine the type of response to each radiation particle or photon.particle or photon.

Gas-Filled DetectorsGas-Filled Detectors


As the applied voltage is increased from zero to a large value, a As the applied voltage is increased from zero to a large value, a characteristic curve will result and is given below. Three gas-filled characteristic curve will result and is given below. Three gas-filled radiation detectors have been developed based on the three usable radiation detectors have been developed based on the three usable regions labeled on the figure. The 3 usable regions on this curve are regions labeled on the figure. The 3 usable regions on this curve are Ionization, Proportional and Geiger-Müller.Ionization, Proportional and Geiger-Müller.

Ionization CurveIonization Curve


Gas-Filled Detector:Gas-Filled Detector:Ionization RegionIonization Region


At relatively low voltages, many of the ion pairs produced in an ion chamber At relatively low voltages, many of the ion pairs produced in an ion chamber will simply recombine, leaving no charge flow between the electrodeswill simply recombine, leaving no charge flow between the electrodes

As the voltage is increased, a certain point is reached where 100% of the ions As the voltage is increased, a certain point is reached where 100% of the ions produced will reach the electrodes. This plateau region is referred to as the produced will reach the electrodes. This plateau region is referred to as the ionization region.ionization region.

Ionization ChamberIonization Chamber


High Voltage

In this region, the number of ions collected by the In this region, the number of ions collected by the electrode will be equal to the number produced by the electrode will be equal to the number produced by the primary ionization event. Further small increases in primary ionization event. Further small increases in voltage have no effect on the current produced in the voltage have no effect on the current produced in the detector. detector.

The current is, however, affected by the type of radiation The current is, however, affected by the type of radiation and subsequently, the quantity of energy deposited by that and subsequently, the quantity of energy deposited by that radiation event. radiation event.

For example, an alpha particle, because of its charge and mass, will For example, an alpha particle, because of its charge and mass, will produce many ion pairs while traveling only a short distance in the gas. produce many ion pairs while traveling only a short distance in the gas. Photons, on the other hand, carry neither charge nor mass and will create Photons, on the other hand, carry neither charge nor mass and will create fewer ion pairs. fewer ion pairs.

Ionization RegionIonization Region


Ionization chambers have many applications Ionization chambers have many applications including:including:

dose calibrators pocket dosimeters survey metersdose calibrators pocket dosimeters survey meters

(Images not to scale)(Images not to scale)

Ion Chamber ApplicationsIon Chamber Applications


When used as a survey meter, an ionization chamber’s When used as a survey meter, an ionization chamber’s current reading is typically used to measure radiation current reading is typically used to measure radiation exposure and is commonly expressed in units of exposure and is commonly expressed in units of Roentgens (R) per hourRoentgens (R) per hour

The Roentgen is defined as the number of ionizations The Roentgen is defined as the number of ionizations produced per kilogram of dry air under standard produced per kilogram of dry air under standard temperature and pressure where:temperature and pressure where:

1 R = 2.58 x 101 R = 2.58 x 10-4-4 coulombs (C) [or 2 x 10 coulombs (C) [or 2 x 1088 ion pairs] ion pairs]

Radiation ExposureRadiation Exposure


Gas-Filled Detector:Gas-Filled Detector:Proportional RegionProportional Region


Proportional counters operate under the principle of gas Proportional counters operate under the principle of gas multiplication. As the voltage is increased past the multiplication. As the voltage is increased past the ionization region, ion pairs created by the incident ionization region, ion pairs created by the incident radiation produce secondary ion pairs due to the applied radiation produce secondary ion pairs due to the applied electric field in the chamber.electric field in the chamber.

Proportional RegionProportional Region


ßß--

The proportional counter is operated to detect all ion pairs The proportional counter is operated to detect all ion pairs generated from the incident radiation and count as a single generated from the incident radiation and count as a single pulsepulse

Ionization chambers, as discussed earlier, count each individual Ionization chambers, as discussed earlier, count each individual ion pair collected (current)ion pair collected (current)

The size of the pulse can be used to identify the type and The size of the pulse can be used to identify the type and energy of the incident radiationenergy of the incident radiation

Large pulse = alpha particleLarge pulse = alpha particle Small pulse = beta particleSmall pulse = beta particle Smaller pulse = gamma/x radiationSmaller pulse = gamma/x radiation

Pulse vs. CurrentPulse vs. Current


Gas-Flow ProportionalGas-Flow Proportional Alpha/beta countingAlpha/beta counting Tritium measurementTritium measurement

Air Proportional CountingAir Proportional Counting Alpha counting onlyAlpha counting only

Sealed ProportionalSealed Proportional Neutron measurement (BFNeutron measurement (BF33, He-3), He-3)

ApplicationsApplications


Gas-Filled Detector:Gas-Filled Detector:Geiger-Müller RegionGeiger-Müller Region


By continuing to increase the voltage above the By continuing to increase the voltage above the proportional region, a point is reached where the detector proportional region, a point is reached where the detector experiences a massive amount of gas multiplication and experiences a massive amount of gas multiplication and creates a very large output pulse.creates a very large output pulse.

Geiger-Müller RegionGeiger-Müller Region


This area of operation is known as the Geiger-Müller This area of operation is known as the Geiger-Müller region. The size of the large output pulse is independent of region. The size of the large output pulse is independent of the amount of ionization produced by the incoming the amount of ionization produced by the incoming radiation. In other words, the pulse is the same regardless radiation. In other words, the pulse is the same regardless of the type of radiation (i.e. alpha, beta, or gamma). The of the type of radiation (i.e. alpha, beta, or gamma). The advantage is that the signal amplitude is large so that no advantage is that the signal amplitude is large so that no amplifiers are needed. amplifiers are needed.

Geiger-Müller RegionGeiger-Müller Region


Detectors operating in the region are called Geiger-Müller (GM) Detectors operating in the region are called Geiger-Müller (GM) detectors. They are simple to use and can detect radiation at very low detectors. They are simple to use and can detect radiation at very low radiation levels due to their large charge amplification. A primary radiation levels due to their large charge amplification. A primary purpose of G-M detectors is the detection of surface contamination purpose of G-M detectors is the detection of surface contamination from beta-emitting isotopes like C-14, P-32, and S-35. from beta-emitting isotopes like C-14, P-32, and S-35.

GM DetectorsGM Detectors


Similar to proportional detectors, when radiation is Similar to proportional detectors, when radiation is captured by a GM tube, ionization along the path of the captured by a GM tube, ionization along the path of the incident radiation results in large gas multiplication incident radiation results in large gas multiplication (avalanche).(avalanche).

GM DischargeGM Discharge


ß-

These “avalanches” require some quenching material in These “avalanches” require some quenching material in the gas in order for the ion pairs to recombine and allow the gas in order for the ion pairs to recombine and allow for detection of another radiation eventfor detection of another radiation event

The time it takes for the detector gas to “reset” is called the resolving timeThe time it takes for the detector gas to “reset” is called the resolving time

Sometimes, in high radiation fields, the pulses generated Sometimes, in high radiation fields, the pulses generated will be too low due to the resolving time losses that the will be too low due to the resolving time losses that the meter will effectively read zero and cease to respond to meter will effectively read zero and cease to respond to radiation (saturation).radiation (saturation).

Resolving TimeResolving Time


The efficiency of the G-M detector is affected by the energy of the The efficiency of the G-M detector is affected by the energy of the radiation being detected. Low energy beta emitters, like H-3 radiation being detected. Low energy beta emitters, like H-3 (Maximum energy (E(Maximum energy (Emaxmax) = 18.6 keV), possess insufficient energy to ) = 18.6 keV), possess insufficient energy to

penetrate the mica window and, thus, cannot be detected by a G-M penetrate the mica window and, thus, cannot be detected by a G-M detectordetector

For practical purposes, C-14 (EFor practical purposes, C-14 (Emaxmax = 156 keV) is the lowest energy beta emitter that = 156 keV) is the lowest energy beta emitter that

can be quantified with a G-M detector.can be quantified with a G-M detector.

Due to the uncharged nature of photons, the efficiency of G-M Due to the uncharged nature of photons, the efficiency of G-M detectors to detect photons is quite low. As a result, G-M detectors detectors to detect photons is quite low. As a result, G-M detectors should not be used to “quantify” I-125 as the measured efficiency for should not be used to “quantify” I-125 as the measured efficiency for this isotope is far less than 1%.this isotope is far less than 1%.

EfficiencyEfficiency


Practical UsesPractical Uses

On the other hand, due to the low On the other hand, due to the low efficiency and directional design of GM efficiency and directional design of GM detectors, they can be useful for detectors, they can be useful for “qualitatively” measuring gamma “qualitatively” measuring gamma contamination in high background areascontamination in high background areas


Scintillation DetectorsScintillation Detectors


Scintillations are small flashes of light that are emitted Scintillations are small flashes of light that are emitted when certain materials, for example NaI(Tl), absorb when certain materials, for example NaI(Tl), absorb radiationradiation

These materials, called scintillators, are commonly used to These materials, called scintillators, are commonly used to detect gamma or X radiationdetect gamma or X radiation

Scintillation DetectorsScintillation Detectors


Scin

tillator

Ionizing Radiation

The scintillations can be captured by a photomultiplier tube The scintillations can be captured by a photomultiplier tube (PMT) and converted to electrons which are used to (PMT) and converted to electrons which are used to quantify incident radiationquantify incident radiation

Photomultiplier TubesPhotomultiplier Tubes


PM

T

e-

Scin

tillator

Ionizing Radiation

An important feature of scintillation detectors is that the energy An important feature of scintillation detectors is that the energy deposited into the crystal is directly proportional to the voltage deposited into the crystal is directly proportional to the voltage generated through the circuitry; thus, an energy spectrum can be generated through the circuitry; thus, an energy spectrum can be plottedplotted

Gamma SpectrumGamma Spectrum


Liquid Scintillation CountingLiquid Scintillation Counting


The scintillating material is the “cocktail”The scintillating material is the “cocktail” Cocktails used in scintillation counting are typically Cocktails used in scintillation counting are typically

biodegradable but can sometimes contain an aromatic biodegradable but can sometimes contain an aromatic solvent (toluene or benzene)solvent (toluene or benzene)

Samples are dissolved or suspended in the cocktailSamples are dissolved or suspended in the cocktail The scintillations are captured by two PMTsThe scintillations are captured by two PMTs

Liquid ScintillationLiquid Scintillation


Belden, Alyssa

Explain coincidence gate

Because the “detector” is in direct contact with the sample, Because the “detector” is in direct contact with the sample, the Liquid Scintillation Counter (LSC) is the only the Liquid Scintillation Counter (LSC) is the only instrument that can efficiently detect tritiuminstrument that can efficiently detect tritium

Tritium (H-3)Tritium (H-3)


Typical efficiencies of LSC’s can be found in your Typical efficiencies of LSC’s can be found in your Radiation Safety Journal on the Monthly Radiation Survey Radiation Safety Journal on the Monthly Radiation Survey ReportReport

EfficienciesEfficiencies

50%50% 95%95% 95%95%


According to Title 17 California Code of Regulations §30275(b), each According to Title 17 California Code of Regulations §30275(b), each user shall perform or cause to have performed such reasonable tests user shall perform or cause to have performed such reasonable tests for the protection of life, health, or propertyfor the protection of life, health, or property

These tests are performed or coordinated through an outside vendor These tests are performed or coordinated through an outside vendor by UCLA Radiation Safety on an annual basis to ensure accuracy and by UCLA Radiation Safety on an annual basis to ensure accuracy and precision of radiation detection and monitoring instrumentsprecision of radiation detection and monitoring instruments

Annual CalibrationAnnual Calibration


Instruments can be dropped off at the UCLA Radiation Safety Central Instruments can be dropped off at the UCLA Radiation Safety Central Services DeskServices Desk

UCLA Radiation Safety Central Services Desk is located in CHS A6-UCLA Radiation Safety Central Services Desk is located in CHS A6-060C near the A-level loading dock060C near the A-level loading dock

Central Services Desk hours are Monday to Friday 9:00am – 4:00pm Central Services Desk hours are Monday to Friday 9:00am – 4:00pm (Closed from 11:30am – 1:00pm daily)(Closed from 11:30am – 1:00pm daily)

Phone: (310) 825-5396Phone: (310) 825-5396

Central Services DeskCentral Services Desk


Belden, Alyssa

Calibration requirements should start after LSCs. I'd also add information on Gamma Counters and proportional counters, maybe even MCAs.


If you have any questions If you have any questions regarding the topics discussed regarding the topics discussed during this presentation, please during this presentation, please

contact the Instrumentation contact the Instrumentation Manager at ext. 5-8797Manager at ext. 5-8797

Training Record FormTraining Record Form


In order to satisfy your annual In order to satisfy your annual refresher training requirement, refresher training requirement, your lab group must submit your lab group must submit the current year’s Principal the current year’s Principal Radiation Worker Training Radiation Worker Training Record Form. This form must Record Form. This form must be sent to Radiation Safety be sent to Radiation Safety before the end of the fall before the end of the fall quarter.quarter.

Beside your name, mark the “O” for OTHER, date, and Beside your name, mark the “O” for OTHER, date, and initial the form. If one of the workers listed is no longer initial the form. If one of the workers listed is no longer with UCLA, please indicate the termination date for the with UCLA, please indicate the termination date for the worker under the column outlined.worker under the column outlined.


1 Jan 2011 AE

If you have any questions If you have any questions regarding the annual refresher regarding the annual refresher training requirement or need a training requirement or need a copy of your lab group’s form, copy of your lab group’s form, please contact your please contact your responsible health physicist or responsible health physicist or the Radiation Safety training the Radiation Safety training manager at ext. manager at ext.

4-1876 or [email protected] or [email protected]


Belden, Alyssa

I'd add a note or slide saying that while peripheral workers need to be trained on hazards in the lab, they do not need to complete this training and shouldn't be added to the form.


Thank you for attention and congratulations on Thank you for attention and congratulations on completing your annual continuing training completing your annual continuing training

credit with the UCLA Radiation Safety.credit with the UCLA Radiation Safety.

END

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