Hopewell Designs, Inc. Calibration of Radiation Instruments Overview, Practical Techniques,...

Hopewell Designs, Inc.

Calibration of Radiation Instruments

Overview, Practical Techniques, Irradiators Illustrated

by

Robert Rushton



OVERVIEW

• Calibration of Instruments

• Irradiators Illustrated

• Chain of Traceability

• NIST

• International Standards


Calibration of Instruments

• Steps in a Typical Calibration Procedure

• What Is Important in a Calibration

• Features that Help Improve Calibrations


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


Elements of a Calibration Program

• Equipment

• Personnel

• Training

• Database, Records Keeping

• Procedures

• QA Program

• Traceability and Accreditation


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


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


Irradiator Control Screen

• System Status

• Exposure Control

• Time

• Setup

• Positioning


Exposure Rate Linked to Position

• Exposure rate calculates distance, or• Enter desired distance & exposure rate

calculated• Based on polynomial equation

from irradiator calibration


Position Instrument on Platform

Box Calibrator Gamma Beam Irradiator


One Button Setup

• PROCEDURE – defined by user

• STEPS • Pull-down menu• Can move to any step

in any order


Control Screen with Instrument Viewing


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


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


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


An Overview of Irradiators – from Sterilization to Calibration


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


Sterilization Irradiators

• 7 million Ci Co-60

• Electron Beam

• High Dose, High Throughput

• Medical, Increasingly Food

• Approx. 200 worldwide


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


X-Ray Blood and Research Irradiators

• No Security Req’d

• Lower Energy Beam


Research Irradiators

• Cs-137 irradiation for medical research, Co-60 for higher doses– Cancer research, – Immunology, – DNA damage/repair, – Materials degradation– Space research.


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


Calibration Irradiators• Gamma• Box• X-Ray• Neutron


Gamma Free In Air


Gamma Beam & Panoramic Irradiators


Panoramic Dosimeter Irradiator


Box Calibrator

• Self-contained

• Typical dual source with attenuator set

• 6 orders of magnitude of exposure rates

• Built in security (but must be fed)


Well Irradiator

• Good for production calibration

• No exposure room req’d

• 9m travel & X100 attenuator give range of 4 orders of magnitude


Gamma Well & Control Station


Small Gamma Irradiator

• For EPDs, PICs, Instrument Probes

• 3 Attenuators – 0 to1000X

• Self contained

• 5 Ci Cs-137 source

X3 8/ 4


Am-241 Irradiator

• Low energy gamma beam


Neutron Free In Air


Pneumatic Neutron/Gamma Irradiator & 4 Positioning Tracks


Pneumatic Transfer System


Neutron Well Irradiator


X-Ray Beam Irradiator


Beta Beam Irradiator


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


Low Scatter Irradiator


LSI - 4 tracks, below ground source storage


LSI Basement

• Below ground shield for 7 sources

• Staircase to basement


Gamma Beam Irradiator


Source Transfer Tube for GBI -

curved to prevent radiation shine


Source Holders - “Rabbits”


Major Functions of Automation

• Control of Irradiator

• Automation of Procedures

• Data Collection and Analysis

• Database Links


Computer Control

• 1 Button Setup

• Exposure Rate Calculation

• Automated Irradiator Calibration


Safety Systems

• Fail-Safe Design

• Indicator Lights

• Search & Evict Process

• Door Interlocks

• Emergency Off Switch

• Error Monitoring


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.


Calibration Set Up

Ion Chamber in Beam Centerline

Electrometer Linked to Computer

Software for Data Collection


Irradiator Calibration

• Set up parameters• Ion Chamber• Electrometer• Calibration Points• Exposure


Positioning Track Set Up

• Number of Distances to Measure• Geometric/Linear• Range


Automated Irradiator Operation

• Track position set• Electrometer

polled• Exposure

controlled• Data recorded


Data Analysis

• Data is fit to polynomial curve

• Parameters and equation stored to database.


Chain of Traceability

• Instrument Calibration Labs

• Secondary Level Calibration Labs

• Primary Calibration Labs


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


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


• 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


Control Station for Dual X-ray Sets


300 kV X-Ray Range


An Instrument Calibration atNIST X-Ray Calibration Lab

• 100 kV Range

• 300 kV Range

• Mammography Range


Instrument Calibration Set Up

Free Air Chamber (NIST National

Standard)

Customer’s Ion Chamber


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


Report for Ion Chamber

• Shows Raw Data

• Beam Code

• Chamber Settings

• Air Kerma

• Calibration Factor


Overall Uncertainty Reduced by

• Up to 15 correction factors calculated and applied

• Measurements confirmed via multiple paths

• Precision positioning

• High precision, ultra stable equipment


Results in Uncertainties of:

• Primary calibration labs ± 1%

• Secondary labs ± 2-3%

• Calibration labs > 3%


National StandardsCanada’s X-Ray Free Air Chamber


IAEA Co-60

Ion Chamber


NIST Wide Angle Free Air Chamber


International Standards

• A Look at Calibration Labs Around the World

• Intercomparison and Other International Programs


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.


Primary Standards Laboratories (PSL)

• France

• Germany

• Canada

• Australia

• Austria

• Hungary• Netherlands

• New Zealand

• Russia

• Spain

• USA

• Italy

• Japan

• United Kingdom

• (plus others)


Secondary Standards Labs (SSL)

AlgeriaArgentinaBangladeshBelarusBolivia BrazilBulgariaChileColombiaCuba

CyprusCzech RepublicDenmarkEcuadorEgyptEthiopiaFinlandGeorgiaGhanaGreeceGuatemala

HungaryIndiaIndonesiaIranIrelandIsraelKoreaKuwaitLatviaLibyaMadagascar

MalaysiaMexicoNorwayPakistanPeruPhilippinesPolandPortugalRomaniaSaudi ArabiaSerbiaSingapore

Slovak RepublicSloveniaSouth AfricaSudanSwedenSyriaTanzaniaThailandTunisiaTurkeyUruguayVenezuelaVietnam


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


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


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


Services for Radioactivity Measurements


Intercomparison Results – One Example


Primary Uses of Radiation - Worldwide

• Nuclear Power

• Industrial Processing, Primarily Sterilization

• Medical Diagnostic and Treatment


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


Major Role of SSL

• Help assure accurate dosimetry thru:

– Instrument calibration – traceable to a primary standard

– Dosimetry programs: Calibration & QA audits


Work of the SSLs

• Maintain Radiation Dosimetry Standards

• Collaborate with hospitals and end users

• Provide services to end users


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


Institut Rudjer Boskovic, Croatia

• Institute – nuclear research for over 50 yrs

• Provides dosimetry services

• Setting up instrument calibration


Co-60 Teletherapy Calibration


X-Ray Techniques,Cs-137 Protection Level Cal.


Institute of Nuclear Physics, Albania

• Nuclear research

• Dosimetry program

• Instrument calibration program being implemented


X-Ray and Cs-137

Calibrations


Kazakhstan Atomic Energy Committee


Ministry of Health, Kuwait


Institute of Public Health, Romania

• Active dosimetry and instrument calibration for over 30 years

• Upgrade Equipment• Adding to Capabilities


Radiation Institute of

Ireland


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Hopewell Designs, Inc. Calibration of Radiation Instruments Overview, Practical Techniques,...

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