BS-ISO-15573-1998.pdf

BRITISH STANDARD BS ISO 15573:1998 Practice for dosimetry in an electron-beam facility for radiation processing at energies between 80 keV and 300 keV ICS 17.240 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:41:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 15573:1998 This British Standard, having been prepared under the direction of the Engineering Sector Committee, was published under the authority of the Standards Committee and comes into effect on 15 August 1999 © BSI 03-2000 ISBN 0 580 32911 9 National foreword This British Standard reproduces verbatim ISO 15573:1998 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee NCE/2, Health physics instrumentation, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the ISO title page, pages ii to iv, pages 1 to 10 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:41:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 15573:1998 © BSI 03-2000i Contents Page National forewordInside front cover Forewordiii Text of ISO 155731 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:41:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:41:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:41:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 15573:1998 ii © BSI 03-2000 Contents Page Forewordiii 1Scope1 2Referenced Documents1 3Terminology1 4Significance and Use3 5Dosimetry System4 6Installation Qualification and Testing4 7Frequency of Dosimetric Measurements5 8Throughput Calculations5 9Certification5 10Measurement Uncertainty6 11Keywords6 Appendix X1 (Nonmandatory information) Method for measuring surface area rate coefficient (K), dose depth, and dose uniformity7 Figure 1 Depth Dose Curves (0.5 mil Ti Window, 0.5 in. Air Gap)3 Figure X1.1 Depth Dose Curve 300 kV (2.5 cm Air Gap, 13 4m Titanium Foil Window)8 Figure X1.2 Electron Beam Width Dose Uniformity9 Table 1 Calculated K Values at the Product Surface4 Table X1.1 Example of Depth Dose Distribution at 300 kV (Air Gap 2.5 cm, 13 4m Titanium Foil Window)7 References10 Related materials10 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:41:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 15573:1998 © BSI 03-2000iii Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard ISO 15573 was prepared by the American Society for Testing and Materials (ASTM) Subcommittee E10.01 (as E 1818-96) and was adopted, under a special “fast-track procedure”, by Technical Committee ISO/TC 85, Nuclear energy, in parallel with its approval by the ISO member bodies. A new ISO/TC 85 Working Group WG 3, High-level dosimetry for radiation processing, was formed to review the voting comments from the ISO “Fast-track procedure” and to maintain these standards. The USA holds the convenership of this working group. International Standard ISO 15573 is one of 20 standards developed and published by ASTM. The 20 fast-tracked standards and their associated ASTM designations are listed below: ISO DesignationASTM DesignationTitle 15554E 1204-93Practice for dosimetry in gamma irradiation facilities for food processing 15555E 1205-93Practice for use of a ceric-cerous sulfate dosimetry system 15556E 1261-94Guide for selection and calibration of dosimetry systems for radiation processing 15557E 1275-93Practice for use of a radiochromic film dosimetry system 15558E 1276-96Practice for use of a polymethylmethacrylate dosimetry system 15559E 1310-94Practice for use of a radiochromic optical waveguide dosimetry system 15560E 1400-95aPractice for characterization and performance of a high-dose radiation dosimetry calibration laboratory 15561E 1401-96Practice for use of a dichromate dosimetry system 15562E 1431-91Practice for dosimetry in electron and bremsstrahlung irradiation facilities for food processing 15563E 1538-93Practice for use of the ethanol-chlorobenzene dosimetry system 15564E 1539-93Guide for use of radiation-sensitive indicators 15565E 1540-93Practice for use of a radiochromic liquid dosimetry system 15566E 1607-94Practice for use of the alanine-EPR dosimetry system Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:41:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 15573:1998 iv © BSI 03-2000 ISO DesignationASTM DesignationTitle 15567E 1608-94Practice for dosimetry in an X-ray (bremsstrahlung) facility for radiation processing 15568E 1631-96Practice for use of calorimetric dosimetry systems for electron beam dose measurements and dosimeter calibrations 15569E 1649-94Practice for dosimetry in an electron-beam facility for radiation processing at energies between 300 keV and 25 MeV 15570E 1650-94Practice for use of cellulose acetate dosimetry system 15571E 1702-95Practice for dosimetry in a gamma irradiation facility for radiation processing 15572E 1707-95Guide for estimating uncertainties in dosimetry for radiation processing 15573E 1818-96Practice for dosimetry in an electron-beam facility for radiation processing at energies between 80 keV and 300 keV Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:41:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 15573:1998 © BSI 03-20001 1 Scope 1.1 This practice covers dosimetric procedures to be followed to determine the performance of low energy (300 keV or less) single-gap electron beam radiation processing facilities. Other practices and procedures related to facility characterization, product qualification, and routine processing are also discussed. 1.2 The electron energy range covered in this practice is from 80 keV to 300 keV. Such electron beams can be generated by single-gap self-contained thermal filament or plasma source accelerators. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2 Referenced Documents 2.1 ASTM Standards: E 170, Terminology Relating to Radiation Measurements and Dosimetry1). E 177, Practice for Use of the Terms Precision and Bias in ASTM Test Methods2). E 456, Terminology Relating to Quality and Statistics2). E 1261, Guide for Selection and Calibration of Dosimetry Systems for Radiation Processing1). E 1275, Practice for Use of a Radiochromic Film Dosimetry System1). E 1276, Practice for Use of a Polymethylmethacrylate Dosimetry System1). E 1607, Practice for Use of the Alanine-EPR Dosimetry System1). E 1650, Practice for Use of a Cellulose Acetate Dosimetry System1). E 1707, Guide for Estimating Uncertainties in Dosimetry for Radiation Processing1). 2.2 International Commission on Radiation Units and Measurements (ICRU) Reports.3) ICRU Report 33, Radiation Quantities and Units. ICRU Report 37, Stopping Powers for Electrons and Positrons. 2.3 Methods for Calculating Absorbed Dose and Dose Distribution.4) ZTRAN Monte Carlo Code Integrated Tiger Series (ITS) Monte Carlo Codes Energy Deposition in Multiple Layers (EDMULT) Electron Gamma Shower (EGS43) Monte Carlo Codes 3 Terminology 3.1 Definitions 3.1.1 Definitions of terms used in this practice may be found in Terminology E 170 and ICRU Report 33. 3.2 Definitions of Terms Specific to This Standard 3.2.1 absorbed dose (D), n quantity of ionizing radiation energy imparted per unit mass of a specified material. The SI unit of absorbed dose is the gray (Gy), where 1 gray is equivalent to the absorption of 1 joule per kilogram of the specified material (1 Gy = 1 J/kg). The mathematical relationship is the quotient ofby dm, where is the mean incremental energy imparted by ionizing radiation to matter of incremental mass dm (see ICRU Report 33). 3.2.1.1 discussion the discontinued unit for absorbed dose is the rad (1 rad = 100 erg/g = 0.01 Gy). Absorbed dose is sometimes referred to simply as dose 3.2.2 air gap, n the distance between the product plane and the electron beam window 3.2.3 backscatter, n the term used to describe additional absorbed dose caused by scatter of the primary electron beam from nearby material 3.2.4 beam current, n time-averaged electron beam current delivered from the accelerator 1) Annual Book of ASTM Standards, Vol 12.02. 2) Annual Book of ASTM Standards, Vol 14.02. 3) Available from the International Commission on Radiation Units and Measurements, 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814. 4) Available from the Radiation Shielding Information Center (RSIC), Oak Ridge National Laboratory (ORNL), P.O. Box 2008, Oak Ridge, TN 37831. (1) d for example, sterility, gel fraction, melt flow, modulus, molecular weight distribution, or cure analysis tests can be used to determine radiation dose in specific relevant materials. Wherever possible, the results of quantitative physical testing should be used in conjunction with dosimetry in commercial radiation processing applications. 4.2 Radiation processing specifications usually include a minimum or maximum absorbed dose limit, or both. For a given application these limits may be set by government regulation or by limits inherent to the product itself. Figure 1 Depth Dose Curves (0.5 mil Ti Window, 0.5 in. Air Gap) Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:41:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 15573:1998 4 © BSI 03-2000 Table 1 Calculated K Values at the Product Surface 4.3 Critical process parameters must be controlled to obtain reproducible dose distribution in processed materials. The electron beam energy (in eV), beam current (in mA), spatial distribution of the beam, and exposure time or process line speed all affect absorbed dose (see Section 5). In some liquid-to-solid polymerization applications (often referred to as radiation curing), the residual oxygen level during irradiation must be controlled to achieve consistent results. A high level of residual oxygen can affect product performance in these curing applications, but it will not affect the absorbed dose. 4.4 Before any radiation process can be utilized, it must be validated to determine its effectiveness. This involves testing of the process equipment, calibrating the measuring instruments, and demonstrating the ability to deliver the desired dose within the desired dose range in a reliable and reproducible manner. The desired improvements, as well as any undesirable effects due to radiation damage to a specific product, should be understood. 5 Dosimetry System 5.1 The documents listed in Section 2 provide detailed information on the selection and use of appropriate dosimetry systems for gamma-ray and electron beam irradiation. Due to the limited depth of penetration of low energy electron beams and the narrow air gaps that are inherent in self-shielded equipment, thin film dosimeters are usually preferred over thicker systems (see Refs 1, 2, and 3,5) Practices E 1275 and E 1650, and Guide E 1261). 6 Installation Qualification and Testing 6.1 Equipment Testing The first phase of qualifying an irradiation facility is to determine that the processing equipment performs in accordance with design specifications. The process should include mechanical and electrical testing of the electron beam accelerator and related processing equipment, and should include, but not be limited to, the following: 6.1.1 Operation of all safety interlocks, 6.1.2 Operation of all system interlocks, 6.1.3 An extended demonstration of system performance at specified ratings, 6.1.4 Operation of the system over the full range of voltage and beam current, 6.1.5 Radiation survey at maximum operating voltage and current, 6.1.6 Mechanical inspection of the system, 6.1.7 Electrical inspection of the system, 6.1.8 Performance of the inert gas system, if applicable, 6.1.9 Performance of the ozone exhaust system, if applicable, and 6.1.10 Testing and calibration of product handling system over the full performance range. 6.2 The second phase of qualifying an irradiation facility is to characterize the performance of the equipment using dosimetry. The purpose of these measurements is to qualify the dose delivering characteristics of the equipment for performance acceptance and for future reference. The process should include, but not be limited to, the following: 6.2.1 Surface Area Rate Measurements minimum of five measurements over the voltage range of interest with at least five dosimeters equally spaced across the width of the beam at the product plane at a nominal dose level. The surface area rate measurement should be repeated at a typical operating voltage level at several different beam current levels to establish and test the linearity between beam current and surface dose (see Appendix X1). 6.2.2 Beam Uniformity Measu