ASTM E385 Oxygen Content Using a 14-MeV Neutron Activation and Direct-Counting Technique

Scope:

The traditional method for the determination of oxygen concentration of liquid or solid samples is a complicated chemical technique. It’s sluggish and normally has a low sensitivity level. The 14-MeV neutron activation and direct counting methodology provides a nondestructive, fast, and extremely sensitive method for determining oxygen in a variety of matrices. The chemical form of oxygen has no bearing on this test procedure. This test method can be utilized in metals, coal, and petroleum sectors for quality and process control, as well as for research in a wide range of applications.

Procedure:

In ASTM E385, a weighted sample is placed in a container for automatic movement from a sample-loading port to a particle accelerator’s 14-MeV neutron irradiation station. The high-energy gamma radiation produced by the radioactive decay of the ¹⁶N produced by the (n, p) nuclear process on ¹⁶O is measured by a gamma-ray detector. A gated scaler records the number of counts in a predetermined counting period. The number of events collected for samples and the monitor reference standard are standardized to the same irradiation and counting conditions. The monitor count as well as the total sample count is observed.

Video 01: Neutron Activation

Specimen Size:

Once a sample has been taken, it should be handled in such a way that contamination is minimized. It should be enclosed with an inert environment, such as dry nitrogen gas.

Data:

Calculation of the results in terms of weight percent of oxygen is as follows.

K = (A_std /A_m)/ W_std

A_std = total count from comparator standard.

A_m = total monitor count.

W_std = milligrams of oxygen in comparator standard.

K = sensitivity in counts per milligram of oxygen per unit monitor count.

Conclusion:

ASTM E385 method can be utilized on solid or liquid samples if they can be made to comply in size, shape, and macroscopic density while being irradiated and counted against a known oxygen content standard sample.