ASTM E262 is a common nuclear engineering and radiation metrology technique of measuring thermal neutron reaction rates and fluence rates using radioactivation techniques. It is published by ASTM International and is used by labs dealing with reactors, neutron generators, and experimental irradiation systems. It is based on relying on exposure of the activation materials, e.g., gold or indium, to a specified neutron field, followed by the measurement of induced radioactivity with the help of the high-resolution detectors. Such a method is very sensitive and can thus be used in settings where direct neutron-measurement devices might be inadequate. Preparation requirements, decay corrections, and detector calibration, as well as data reduction, are also defined in the standard. ASTM E262 has become a fundamental tool in the research of reactor physics and neutron dosimetry by virtue of its reliability.
ASTM E262 Standard Test Method for Determining Thermal Neutron Reaction Rates and Thermal Neutron Fluence Rates by Radioactivation Techniques
What is ASTM E262?
What is the Scope of ASTM E262 Testing?
ASTM E262 is important because it offers a reproducible and reliable method of obtaining a measurement of the thermal neutron environment on a global scale. Its systematic approach enhances reactor safety tests, experimental reliability, and material performance forecasting under neutron exposure.
What are the Uses of ASTM E262 Testing?
This criterion is used in the calibration of reactors, evaluation of shielding materials, neutron beam studies, in testing of fuels, and in quality control in nuclear research centers. It is also applicable in regulatory compliance and experimental neutron dosimetry
ASTM E262 Materials Commonly Tested
The common types of foils are gold foils, indium foils, copper wires, and dysprosium discs because such foils have well-defined neutron capture cross sections and well-known activation behavior.
ASTM E262 Equipment and Sample Preparation Guide
| Specimen Preparation | Non-magnetic tools are used to cut foils into circular or rectangular specimens of mass between 20 mg and 80mg, so that they have a uniform geometry to activate. |
| Specimen Dimensions | The foil samples have a diameter of 5 mm to 12 mm, or any other area with a tight tolerance on the thickness of the foil to eliminate neutron absorption variations. |
| Preparation Equipment | Before irradiation, it is necessary to have precision cutting dies, digital micrometers with an accuracy of 0.001 mm, and holders without contamination to maintain the integrity of the specimen. |
Testing Procedures and Requirements for ASTM E262
| Selection of Activation Materials | The technique normally uses 99.9 percent pure gold foil with a nominal thickness of 0.01 mm to 0.05 mm so that the neutron capture performance and dependability of activation response may be accurately determined. |
| Irradiation Conditions | An irradiation of foils occurs in a field of thermal neutrons having a representative flux of 109-1013 neutrons/square centimeter/second, so that measurable induced activity can be measured later under gamma spectrometry. |
| Activity Measurement | The measurements are made using the calibrated high-purity germanium detector, and intervals of measurements have been adjusted according to the half-life of the activated isotopes (e.g., Au-198). |
ASTM E262 Analysis Results and Interpretation
Findings are presented in the form of thermal neutron reaction rates and respective fluence rates that are derived using measured activity, decay corrections, irradiation time, and detector efficiency. The induced activity is transferred into a reaction rate by known neutron cross sections provided by ASTM International. An increase in the measured activity means an increase in neutron flux exposure. Interpretation must be done with a strong element of uncertainty assessment, which involves counts, calibration accuracy, and mass determination of foils. Proper interpretation enables the laboratories to define the neutron fields and check the operating parameters of a reactor.
ASTM E262 Related Articles
ASTM E261 standard test method of determining neutron exposure using radiometric techniques, which addresses the area of fast neutron dosimetry. ASTM E264 practice on measuring fast-neutron reaction rates, describing the processes of measurements on high-energy neutron activation.
ASTM E262 Safety and Best Practices in the Standard
The procedure demands compliance with the radiation protection rules, correct handling of activated samples, restricted access to radiation locations, monitoring of the decay periods, and application of shielded counting stations. Documentation is very strict to limit exposure risk as well as traceability.
Updated on September 16, 2026
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