ASTM: D1890: Beta Activity in Water
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Official Method Name
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Standard Test Method for Beta Particle Radioactivity of Water |
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Current Revision
| 1996 |
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Media
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WATER |
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Instrumentation
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Beta Gas Proportional Counter |
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Method Subcategory
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Radiochemical |
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Method Source
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Citation
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Brief Method Summary
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Beta radioactivity may be measured by one of several types of instruments composed of a detecting device and combined amplifier, power supply, and scaler - the most widely used being proportional or Geiger-Muller counters. Where a wide range of counting rates is encountered (0.1 to 1300 counts per seconds), the proportional-type counter is preferable due to a shorter resolving time and greater stability of the instrument. The test sample is reduced to the minimum weight of solid material having measurable beta activity by precipitation, ion exchange resin, or evaporation techniques. Beta particles entering the sensitive region of the detector produce ionization of the counting gas. The negative ion of the original ion pair is accelerated towards the anode, producing additional ionization of the counting gas and developing a voltage pulse at the anode. By use of suitable electronic apparatus, the pulse is amplified to a voltage sufficient for operation of the counter scaler. The number of pulses per unit of time is related to the disintegration rate of the test sample. The beta-particle efficiency of the system can be determined by use of prepared standards having the same radionuclide composition as the test specimen and equivalent residual plated solids. An arbitrary efficiency factor can be defined in terms of some other standard such as cesium-137. |
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Scope and Application
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This test method covers the measurement of beta particle activity of water, as referenced to the beta energy of cesium-137, not corrected for conversion electrons. It is applicable to beta emitters having maximum energies above 0.1 MeV and at activity levels above 0.02 Bq/mL of radioactive homogeneous water for most counting systems. This test method is not applicable to samples containing radionuclides that are volatile under conditions of the analysis. This test method can be used for either absolute or relative determinations. In tracer work, the results may be expressed by comparison with a standard which is defined to be 100%. For radioassay, data may be expressed in terms of a known radionuclide standard if the radionuclides of concern are known and no fractionation occurred during processing, or may be expressed arbitrarily in terms of some other standard such as cesium-137. |
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Applicable Concentration Range
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> 0.02 Bq/mL |
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Interferences
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Material interposed between the test sample and the instrument detector, as well as increasing density in the sample containing the beta emitter, produces significant losses in sample counting rates. Liquid samples are evaporated to dryness in dishes that allow the sample to be counted directly by the detector. Since the absorption of beta particles in the sample solids increases with increasing density and varies inversely with the maximum beta energy, plated solids shall remain constant between related test samples and should duplicate the density of the solids of the plated standard. |
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Quality Control Requirements
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Sample Handling
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Collect the sample in accordance with Practices D 3370. Preserve the sample in a radioactively homogeneous state. A sample may be made homogeneous by addition of a reagent in which the radionuclides or compounds of the radionuclides present in the sample would be soluble in large concentrations. Addition of acids, complexing agents, or chemically similar stable carriers may be used to obtain homogeneity. Consideration of the chemical nature of the radionuclides and compounds present and the subsequent chemistry of the method will indicate the action to be taken. The addition of chemicals (HCl) corrosive to the mounting dish shall be avoided to prevent increased absorption of beta particles by the increased residual solids. |
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Maximum Holding Time
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Relative Cost
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Unknown |
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Sample Preparation Methods
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