ASTM/ISO 51401-02

1.1 This practice covers the preparation, testing, and procedure for using the acidic aqueous silver dichromate dosimetry system to measure absorbed dose in water when exposed to ionizing radiation. The system consists of a dosimeter and appropriate analytical instrumentation. For simplicity, the system will be referred to as the dichromate system. It is classified as a reference standard dosimetry system (see ISO/ASTM Guide 51261).

1.2 This practice describes the spectrophotometric analysis procedures for the dichromate system.

1.3 This practice applies only to γ-rays, X rays, and high energy electrons.

1.4 This practice applies provided the following conditions are satisfied:

1.4.1 The absorbed dose range is from 2 X 10 ³ to 5 X 10⁴ Gy.

1.4.2 The absorbed dose rate does not exceed 600 Gy/pulse with a pulse repetition rate not to exceed 12.5 Hz, or does not exceed an equivalent dose rate of 7.5 kGy/s from continuous sources (1).

1.4.3 For radionuclide gamma-ray sources, the initial photon energy shall be greater than 0.6 MeV. For bremsstrahlung photons, the initial energy of the electrons used to produce the bremsstrahlung photons shall be equal to or greater than 2 MeV. For electron beams, the initial electron energy shall be greater than 8 MeV.

Note 1—The lower energy limits given are appropriate for a cylindrical dosimeter ampoule of 12 mm diameter. Corrections for displacement effects and dose gradient across the ampoule may be required for electron beams (2). The dichromate system may be used at lower energies by employing thinner (in the beam direction) dosimeter containers (see ICRU Report 35).

1.4.4 The irradiation temperature of the dosimeter shall be above 0°C and should be below 80°C.

Note 2—The temperature coefficient of dosimeter response is known only in the range of 5 to 50°C (see 10.1.8). Use outside this range is not recommended.

1.5 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 precautionary statements are given in Note.