B3 Dosimeter Batch Calibration

The color response of each B3 dosimeter batch has a unique relationship to dose, and it is dependent on the conditions of use because of the effects from influence quantities. The dosimeter batch calibration is necessary to establish a mathematical relationship between the dosimeter response and dose (Gy or kGy).

The user must complete a calibration prior to routine use of the dosimeter measurement system to obtain valid dose values traceable to an international standard.

For detailed information, procedure templates and technical reports see Dosimeter Batch Calibration (Dosimetry System Calibration).

What is a ‘dosimeter batch calibration’?	The dosimeter batch calibration is necessary to establish a mathematical relationship between the dosimeter response and dose (Gy or kGy). See B3 Dosimetry Basics.
Do B3 dosimeters need to be calibrated prior to routine use?	Yes. Most industries require a valid dosimetry system calibration. A calibration curve (or response vs. dose table) is necessary to calculate a dose value from a dosimeter’s measured response value.
When do I calibrate and what is the calibration interval?	New Batch: The B3 dosimetry system must be calibrated for each new dosimeter batch; the dosimeter response will vary from one batch to another. Existing Batch: For an existing batch of dosimeters, a calibration verification check (or recalibration) should be conducted: Annually. (Per ASTM 52628) If there has been a change in any influence quantity, such as temperature, that may affect the dosimeter response. (Per ASTM 52628) Recalibration of an existing batch dosimeters must be conducted at a frequency specified by the user based on known characteristics of the dosimetry system. (Per ASTM 51261) Receiving new stock of an existing Batch: It is best practice to calibrate (or verify equivalency) of each new stock of B3 dosimeters, even if the new stock is the same Batch ID as an older stock. The user may verify the equivalency of response of this product between different stocks/deliveries with the same characteristics (e.g. dosimeter Batch ID) within defined limits. (Per ASTM 51261, CIRM 29). See GEX recommended procedure for Dosimeter Stock Receiving Inspection.
Why must I calibrate each batch of dosimeters?	The response of the dosimeter will vary from one dosimeter to another within the same batch having the same certified average thickness. Therefore, the process of dosimeter batch calibration involves irradiation and measurement of representative samples of a stock of dosimeters that are owned and stored by the user. (Per ASTM 51261, CIRM 29)
Why does GEX recommend ‘in-plant’ calibrations?	The dosimeter response is affected by the various influence quantities (see General Characteristics of B3 Dosimeters). In-plant (in-situ) calibration should capture environmental influences and specifics of the user’s irradiation and measurement process. Additional items to consider: The dosimeter response measured on one spectrophotometer will vary slightly from the value measured on a different spectrophotometer. To ensure measurement accuracy, it is standard industry practice to calibrate the dosimeter response on each instrument, as part of the dosimeter batch calibration (ASTM 51261, CIRM 29). You can choose to combine the instrument data, or one instrument demonstrated to be “equivalent” to another, but proper treatment of the data and assessment of additional measurement uncertainty components may be required as part of the dosimeter batch calibration. The dosimeter response will vary from one irradiator to another based on irradiation geometry and environmental differences between one irradiator and another. In addition to differences in irradiation geometry that may be present from one irradiator or irradiation pathway to another, the effect of influence quantities may also be different. Users should calibrate each irradiator or pathway independently unless they have evidence that they are equivalent and have accounted for allowed variability in their measurement uncertainty budget. Calibration curves are specific to the measurement system (reader). Calibration curves must not be used with other readers unless the user has demonstrated that the dose measurements agree within user defined limits (ASTM 51261).
Can GEX provide a ‘factory’ calibration for B3 dosimeters?	GEX can provide a factory calibration, but it is not included with the B3 product. This type of calibration does not provide valid dose values that are traceable to an international standard. Contact GEX Customer Support for more information.
Can GEX provide a calibration procedure template for users?	GEX offers a calibration procedure template - Performing a Dosimeter Batch Calibration - Procedure Template (Note: GEX provides this procedure template as a courtesy for B3 users. It is designed to comply with ASTM 51261, but the user must incorporate and verify all specifics for their use and assumes all responsibility for the use of this template).
Does GEX provide a dosimeter batch calibration service?	Yes, GEX provides complete and formalized dosimeter batch calibration services for a wide range of applications. Conforms to current recommended methods published in ASTM 51261. Product Number: S1101, S1102. Download product sheet: GEX Doc. 100-141 GEX Dosimeter Batch Calibration Service and Audits.
Does GEX have general guidance regarding dosimeter batch calibration specific for B3 dosimetry?	Dosimetry System Calibration - Technical Report Calibration of Dosimetry Systems in Low Energy Electron Irradiation - Technical Report
Industry guidance	See Industry Standards ASTM 51261 Standard Practice for Calibration of Routine Dosimetry Systems for Radiation Processing, ASTM 52628 Standard Practice for Dosimetry in Radiation Processing, NPL Report CIRM 29 “Guidelines for the Calibration of Dosimeters for use in Radiation Processing”.
GEX recommendations	GEX recommends in-plant calibration, under normal process and environmental conditions for all applications and processes and done in accordance with ASTM 51261 Method 2. The B3 dosimeters should be calibrated using the standard SOPs for dosimeter handling, measurement, and all other parameters the user can control to best capture the response under routine conditions. In general, a phantom absorber is required to ensure the dose to both the GEX dosimeters, and the reference dosimeter is equivalent. In general, GEX discourages the use of laboratory calibrations ISO 51261:2015 Method 1 except where the user can justify it and verify the applicability to their own irradiation process.

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