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Significance and Use
4.1 The Fricke dosimetry system provides a reliable means for measurement of absorbed dose to water, based on a process of oxidation of ferrous ions to ferric ions in acidic aqueous solution by ionizing radiation (4). In situations not requiring traceability to national standards, this system can be used for absolute determination of absorbed dose without calibration, as the radiation chemical yield of ferric ions is well characterized (see Appendix X3).
4.2 The dosimeter is an air-saturated solution of ferrous sulfate or ferrous ammonium sulfate that indicates absorbed dose by an increase in optical absorbance at a specified wavelength. A temperature-controlled calibrated spectrophotometer is used to measure the absorbance (ICRU 80).
1.1 This practice covers the procedures for preparation, testing and using the acidic aqueous ferrous ammonium sulfate solution dosimetry system to measure absorbed dose to water when exposed to ionizing radiation. The system consists of a dosimeter and appropriate analytical instrumentation. The system will be referred to as the Fricke dosimetry system. The Fricke dosimetry system may be used as either a reference standard dosimetry system or a routine dosimetry system.
1.2 This practice is one of a set of standards that provides recommendations for properly implementing dosimetry in radiation processing, and describes a means of achieving compliance with the requirements of Practice E2628 for the Fricke dosimetry system. It is intended to be read in conjunction with Practice E2628.
1.5.2 The absorbed-dose rate does not exceed 106 Gy·s−1 (2).
1.5.3 For radioisotope gamma sources, the initial photon energy is greater than 0.6 MeV. For X-radiation (bremsstrahlung), the initial energy of the electrons used to produce the photons is equal to or greater than 2 MeV. For electron beams, the initial electron energy is greater than 8 MeV.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
C912 Practice for Designing a Process for Cleaning Technical Glasses
E170 Terminology Relating to Radiation Measurements and Dosimetry
E178 Practice for Dealing With Outlying Observations
E275 Practice for Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
E666 Practice for Calculating Absorbed Dose From Gamma or X Radiation
E668 Practice for Application of Thermoluminescence-Dosimetry (TLD) Systems for Determining Absorbed Dose in Radiation-Hardness Testing of Electronic Devices
E925 Practice for Monitoring the Calibration of Ultraviolet-Visible Spectrophotometers whose Spectral Bandwidth does not Exceed 2 nm
E958 Practice for Estimation of the Spectral Bandwidth of Ultraviolet-Visible Spectrophotometers
E2628 Practice for Dosimetry in Radiation Processing
ISO/ASTM51261 Practice for Calibration of Routine Dosimetry Systems for Radiation Processing
ISO/ASTM51707 Guide for Estimating Uncertainties in Dosimetry for Radiation Processing
ISO/IEC StandardISO/IEC17025 General requirements for the competence of testing and calibration laboratories Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
International Commission on Radiation Units and Measurements (ICRU) ReportsICRUReport14 Radiation Dosimetry: X Rays and Gamma Rays with Maximum Photon Energies Between 0.6 and 50 MeV ICRUReport35 Radiation Dosimetry: Electrons with Initial Energies Between 1 and 50 MeV ICRUReport64 Dosimetry of High-Energy Photon Beams based on Standards of Absorbed Dose to Water ICRUReport80 Dosimetry Systems for Use in Radiation Processing ICRUReport85a Fundamental Quantities and Units for Ionizing Radiation
Joint Committee for Guides in Metrology (JCGM) ReportsJCGM100:2008GUM1995 , with minor corrections, Evaluation of measurement data - Guide to the Expression of Uncertainty in Measurement
National Research Council Canada (NRCC)PIRS-0815 The IRS Fricke Dosimetry System Available from the National Research Council, Ionizing Radiation Standards, Institute for National Measurement Standards, Ottawa, Ontario. K1A 0R6.
ICS Number Code 17.240 (Radiation measurements)
UNSPSC Code 26141700(Dosimetry equipment)