scope:

This practice covers the procedure for preparation, handling, testing, and use of the ethanol-chlorobenzene (ECB) dosimetry system to determine absorbed dose (in terms of absorbed dose to water) in materials irradiated by photons (gamma radiation or X-radiation/bremsstrahlung) or high energy electrons. The system consists of a dosimeter and appropriate analytical instrumentation. For simplicity, the system will be referred to as the ECB system. It is classified as a reference-standard dosimetry system and is also used as a routine dosimetry system (see ISO/ASTM Guide 51261).

This practice describes the mercurimetric titration analysis as a standard readout procedure for the ECB dosimeter when used as a reference standard dosimetry system. Other readout methods (spectrophotometric, oscillometric) that are applicable when the ECB system is used as a routine dosimetry system are described in Annex A1 and Annex A2.

This practice applies provided the following conditions are satisfied:

The absorbed dose range is between 10 Gy and 2 MGy for gamma radiation and between 10 Gy and 200 kGy for high current electron accelerators (1,2).² (Warning-the boiling point of ethanol chlorobenzene solutions is approximately 80°C. Ampoules may explode if the temperature during irradiation exceeds the boiling point. This boiling point may be exceeded if an absorbed dose greater than 200 kGy is given in a short period of time.)

The absorbed-dose rate is less than 10⁶ Gy s⁻¹(2).

For radionuclide gamma-ray sources, the initial photon energy is greater than 0.6 MeV. For bremsstrahlung photons, the energy of the electrons used to produce the bremsstrahlung photons is equal to or greater than 2 MeV. For electron beams, the initial electron energy is equal to or greater than 4 MeV (3) (see ICRU Reports 34 and 35).

NOTE 1-The same response relative to ⁶⁰Co gamma radiation was obtained in high-power bremsstrahlung irradiation produced by a 5 MeV electron accelerator (4). The lower limits of energy given are appropriate for a cylindrical dosimeter ampoule of 12-mm diameter. Corrections for dose gradients across an ampoule of that diameter or less are not required. The ECB system may be used at energies of incident electrons lower than 4 MeV by employing thinner (in the beam direction) dosimeters. The ECB system may also be used at X-ray energies as low as 120 kVp (5). However, in this range of photon energies the effect caused by the ampoule wall is considerable.

The irradiation temperature of the dosimeter is within the range from −40°C to 80°C.

NOTE 2-The temperature dependence of dosimeter response is known only in this range (see 4.3). For use outside this range, the dosimetry system should be calibrated for the required range of irradiation temperatures.

The effects of size and shape of the dosimeter on the response of the dosimeter can adequately be taken into account by performing the appropriate calculations using cavity theory (6).

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. Specific warnings are given in 8.2 and 9.2.

² The boldface numbers in parentheses refer to the bibliography at the end of this practice.