Transcript Calibration of Radiation Instruments

Hopewell Designs, Inc.
Calibration
of Radiation Instruments
Overview, Practical Techniques,
Irradiators Illustrated
by
Robert Rushton
Hopewell Designs, Inc.
OVERVIEW
• Calibration of Instruments
• Irradiators Illustrated
• Chain of Traceability
• NIST
• International Standards
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Calibration of Instruments
• Steps in a Typical Calibration Procedure
• What Is Important in a Calibration
• Features that Help Improve Calibrations
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Steps in a Typical Calibration
• Receive instrument and log into system
• Perform as found set of readings, typically
20% & 80% full scale, all scales
• If required, repair instrument
• Calibrate and adjust until it falls within
specifications, typically within 10%
• Record to database, prepare report
• Prepare for shipment, log out of system
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Elements of a Calibration Program
• Equipment
• Personnel
• Training
• Database, Records Keeping
• Procedures
• QA Program
• Traceability and Accreditation
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Why they are important …
• Procedures – drive the overall program
• QA – keeps the program on track
• Training – people make it happen,
training shows them how
• Records – documents what is done
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Calibration on an Irradiator
• Set up irradiator for exposure rate
– Track position
– Source & attenuator selection
– Expose source
• Record data and/or adjust instrument
• Go to next step in procedure
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Irradiator Control Screen
• System Status
• Exposure
Control
• Time
• Setup
• Positioning
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Exposure Rate Linked to Position
• Exposure rate calculates distance, or
• Enter desired distance & exposure rate
calculated
• Based on polynomial equation
from irradiator calibration
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Position Instrument on Platform
Box Calibrator
Gamma Beam Irradiator
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One Button Setup
• PROCEDURE –
defined by user
• STEPS
• Pull-down menu
• Can move to any step
in any order
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Control Screen with
Instrument Viewing
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Record Data to Database
• Record As Found / As Left readings &
comments
• Use separate database or irradiator’s
built-in function
• At completion, print out calibration report
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Features that Improve Calibration
• Automation helps with:
– Control of Irradiator
– Automation of Procedures
– Data Collection and Analysis
– Database Links
• Benefits Include
– Improved Accuracy
– Higher Throughput
– Audit Trail for Records
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Irradiators Illustrated
• An Overview of Irradiators – from
Sterilization to Calibration
• Calibration Irradiators – Types and
Isotopes
• A Detailed Look at 2 Types of Irradiators
– LSI and GBI at SRS
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An Overview of Irradiators –
from Sterilization to
Calibration
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NAS Radiation Source Use
and Replacement Report
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Radiation Sources: Uses and Origins
Radiation Source Risk
Accelerator and Detector Technology
Self-Contained Irradiators
Panoramic Irradiators
Radiotherapy
Industrial Radiography
Well Logging
Implementation Options to Encourage
Replacement of Sources with Alternatives
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Sterilization Irradiators
• 7 million Ci Co-60
• Electron Beam
• High Dose, High
Throughput
• Medical, Increasingly
Food
• Approx. 200 worldwide
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Blood Irradiators
• Prevents transfusion
associated graft versus host
disease
• Located at most major
hospitals
• 100’s in operation
• Self-contained, simple to
operate
• Majority use Cs-137
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X-Ray Blood and Research
Irradiators
• No Security Req’d
• Lower Energy Beam
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Research Irradiators
• Cs-137 irradiation for medical research,
Co-60 for higher doses
– Cancer research,
– Immunology,
– DNA damage/repair,
– Materials degradation
– Space research.
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Calibration Irradiators
• Calibration of radiation
instruments
• Smallest segment of
irradiator types in terms of
qnty and total isotope
activity
• Wide variety of designs and
isotopes
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Calibration
Irradiators
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Gamma
Box
X-Ray
Neutron
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Gamma
Free In Air
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Gamma Beam &
Panoramic Irradiators
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Panoramic
Dosimeter
Irradiator
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Box Calibrator
• Self-contained
• Typical dual source
with attenuator set
• 6 orders of
magnitude of
exposure rates
• Built in security (but
must be fed)
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Well Irradiator
• Good for production
calibration
• No exposure room req’d
• 9m travel & X100
attenuator give range of
4 orders of magnitude
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Gamma Well & Control Station
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Small Gamma Irradiator
• Self contained
• 5 Ci Cs-137 source
• For EPDs, PICs,
Instrument Probes
• 3 Attenuators – 0
to1000X
X3 8/ 4
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Am-241
Irradiator
• Low energy gamma
beam
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Neutron Free In Air
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Pneumatic Neutron/Gamma
Irradiator & 4 Positioning Tracks
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Pneumatic Transfer System
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Neutron Well Irradiator
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X-Ray Beam Irradiator
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Beta Beam Irradiator
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A Detailed Look at
2 Types of Irradiators –
LSI and GBI at SRS
• Mechanical & Electrical Design
• Sources and Ranges
• Control System
• Automated Irradiator Software
• Irradiator Calibration, Automated
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Low Scatter Irradiator
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LSI - 4 tracks, below ground source storage
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LSI Basement
• Below ground shield for 7 sources
• Staircase to basement
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Gamma Beam Irradiator
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Source Transfer
Tube for GBI curved to
prevent radiation
shine
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Source Holders - “Rabbits”
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Major Functions of Automation
• Control of Irradiator
• Automation of Procedures
• Data Collection and Analysis
• Database Links
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Computer Control
• 1 Button Setup
• Exposure Rate
Calculation
• Automated
Irradiator
Calibration
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Safety Systems
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Fail-Safe Design
Indicator Lights
Search & Evict Process
Door Interlocks
Emergency Off Switch
Error Monitoring
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CALIBRATION OF IRRADIATOR
• Ion chamber traceable to NIST used to
measure exposure rate
• Measurements made over full range of
track for each source/attenuator
• Data reviewed for accuracy and
consistency
• Actual data fit to polynomial equation for
exposure rate vs. distance.
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Calibration Set Up
Ion Chamber in Beam Centerline
Electrometer Linked to Computer
Software for Data Collection
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Irradiator Calibration
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Set up parameters
Ion Chamber
Electrometer
Calibration Points
Exposure
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Positioning Track Set Up
• Number of Distances to Measure
• Geometric/Linear
• Range
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Automated Irradiator Operation
• Track position set
• Electrometer
polled
• Exposure
controlled
• Data recorded
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Data Analysis
• Data is fit to
polynomial
curve
• Parameters
and equation
stored to
database.
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Chain of Traceability
• Instrument Calibration Labs
• Secondary Level Calibration Labs
• Primary Calibration Labs
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Secondary Calibration Labs
• High level of precision, accuracy, and
error checking
• Single tier traceability to national standard
• In the United States
– Univ. of Wisconsin
– K&S Associates
• International
– Many countries do not maintain primary
standards
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National Institute of
Standards and Technology
• Overview of the Ionizing Radiation
Division
• A Detailed Look at the X-Ray
Calibration Ranges
• Free Air Chamber – the Primary
Standard for 50 to 300 kV X-Rays
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Radiation Interactions and
Dosimetry Group
• Develops, maintains, and disseminates the
national measurement standards for the
dosimetry of x rays, gamma rays, and electrons
• Engages in research on radiation interactions
and effects to meet requirements for new
standards and to address the needs of industry,
medicine, and government.
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Control Station for Dual X-ray Sets
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300 kV X-Ray Range
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An Instrument Calibration at
NIST X-Ray Calibration Lab
• 100 kV Range
• 300 kV Range
• Mammography
Range
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Instrument Calibration Set Up
Free Air Chamber
(NIST National
Standard)
Customer’s Ion
Chamber
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Data Collection and Analysis
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10-15 Readings Taken per Ion Chamber
Mean and Standard Deviation Calculated
Correction Factors Calculated & Applied
Air Kerma, Exposure Rate Calculated for FAC
R/C Calculated for Ion Chamber
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Report for Ion
Chamber
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Shows Raw Data
Beam Code
Chamber Settings
Air Kerma
Calibration Factor
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Overall Uncertainty Reduced by
• Up to 15 correction factors calculated
and applied
• Measurements confirmed via multiple
paths
• Precision positioning
• High precision, ultra stable equipment
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Results in Uncertainties of:
• Primary calibration labs ± 1%
• Secondary labs ± 2-3%
• Calibration labs > 3%
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National Standards
Canada’s X-Ray Free Air Chamber
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IAEA
Co-60
Ion Chamber
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NIST
Wide Angle Free Air Chamber
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International Standards
• A Look at Calibration Labs Around the
World
• Intercomparison and Other International
Programs
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A Bit of Background
• About 20-25% of Hopewell Designs
work is international
• We researched international calibration
and dosimetry programs
• This presentation gives an overview of
what we found, and
• Reviews some of the laboratories where
we supplied equipment.
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Primary Standards Laboratories (PSL)
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France
Germany
Canada
Australia
Austria
Hungary
• Netherlands
• New Zealand
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Russia
Spain
USA
Italy
Japan
• United Kingdom
• (plus others)
Secondary Standards Labs
(SSL)
Algeria
Argentina
Bangladesh
Belarus
Bolivia
Brazil
Bulgaria
Chile
Colombia
Cuba
Cyprus
Czech Republic
Denmark
Ecuador
Egypt
Ethiopia
Finland
Georgia
Ghana
Greece
Guatemala
Hungary
India
Indonesia
Iran
Ireland
Israel
Korea
Kuwait
Latvia
Libya
Madagascar
Malaysia
Mexico
Norway
Pakistan
Peru
Philippines
Poland
Portugal
Romania
Saudi Arabia
Serbia
Singapore
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Slovak Republic
Slovenia
South Africa
Sudan
Sweden
Syria
Tanzania
Thailand
Tunisia
Turkey
Uruguay
Venezuela
Vietnam
The Bureau International des
Poids et Mesures (BIPM)
• Ensures world-wide uniformity of
measurements and traceability to
International System of Measurements
• Via Convention of the Metre
• Intercomparison Programs
• Measurement Related Research
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A Brief History – Dosimetry
and Nuclear Medicine
• 1950’s – Co-60 teletherapy introduced
• 1960’s – Recognized need for uniform
radiation measurements
• 1970’s – Several networks and
programs established in int’l arena
• 1980’s – Ongoing support for
calibration, training, new program
development
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International Traceability
• PSLs and BIPM provide 1st
link in chain of international
measurement system
• Direct comparison with
PSL’s standards
• BIPM and PSLs provide
calibration services to
SSLs & others
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Services for
Radioactivity Measurements
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Intercomparison Results –
One Example
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Primary Uses of Radiation Worldwide
• Nuclear Power
• Industrial Processing, Primarily
Sterilization
• Medical Diagnostic and Treatment
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Medical Treatment
• Largest Segment:
Cancer Treatment
• Most new cancer
cases in developing
countries
• On going effort by WHO and others to
support nuclear medicine programs
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Major Role of SSL
• Help assure accurate dosimetry thru:
– Instrument calibration – traceable to a primary
standard
– Dosimetry programs: Calibration & QA audits
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Work of the SSLs
• Maintain Radiation Dosimetry Standards
• Collaborate with hospitals and end users
• Provide services to end users
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A Short Tour of Recent Work
• Institut Rudjer Boskovic, Croatia
• Institute of Nuclear Physics, Albania
• Kazakhstan Atomic Energy Committee
• Ministry of Health, Kuwait
• Institute of Public Health, Romania
• Radiation Protection Institute of Ireland
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Institut Rudjer Boskovic,
Croatia
• Institute – nuclear
research for over 50 yrs
• Provides dosimetry
services
• Setting up instrument
calibration
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Co-60 Teletherapy Calibration
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X-Ray Techniques,
Cs-137 Protection Level Cal.
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Institute of Nuclear Physics,
Albania
• Nuclear research
• Dosimetry program
• Instrument calibration
program being
implemented
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X-Ray and
Cs-137
Calibrations
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Kazakhstan Atomic
Energy Committee
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Ministry of
Health, Kuwait
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Institute of Public Health,
Romania
• Active dosimetry and
instrument calibration
for over 30 years
• Upgrade Equipment
• Adding to Capabilities
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Radiation
Institute of
Ireland
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Thanks from Hopewell
Designs
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