Hopewell Designs, Inc.
Calibration of Radiation Instruments
Overview, Practical Techniques, Irradiators Illustrated
by
Robert Rushton
Hopewell Designs, Inc.
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
• 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• 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
• For EPDs, PICs, Instrument Probes
• 3 Attenuators – 0 to1000X
• Self contained
• 5 Ci Cs-137 source
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
• 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
• 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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• 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.
Radiation Interactions and Dosimetry Group
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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 atNIST 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
• 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
• 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 StandardsCanada’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)
• France
• Germany
• Canada
• Australia
• Austria
• Hungary• Netherlands
• New Zealand
• Russia
• Spain
• USA
• Italy
• Japan
• United Kingdom
• (plus others)
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Secondary Standards Labs (SSL)
AlgeriaArgentinaBangladeshBelarusBolivia BrazilBulgariaChileColombiaCuba
CyprusCzech RepublicDenmarkEcuadorEgyptEthiopiaFinlandGeorgiaGhanaGreeceGuatemala
HungaryIndiaIndonesiaIranIrelandIsraelKoreaKuwaitLatviaLibyaMadagascar
MalaysiaMexicoNorwayPakistanPeruPhilippinesPolandPortugalRomaniaSaudi ArabiaSerbiaSingapore
Slovak RepublicSloveniaSouth AfricaSudanSwedenSyriaTanzaniaThailandTunisiaTurkeyUruguayVenezuelaVietnam
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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