Radionuclides, analysis

Each column fraction was divided into two portions, one for radionuclide analysis and the other for organic analysis. 

This laboratory experiment describes the preparation of a vegetation sample (e.g., grass) for radiochemical analysis. The sample is dried and ashed. In Part 12A, the ash is fused with sodium hydroxide and sodium carbonate to bring it into solution. An alternative method in Part 12B uses a microwave-assisted digestion technique with nitric and hydrofluoric acid. The prepared sample is suitable for radionuclide analysis, notably for radio-strontium or plutonium. 

Radionuclide analysis of bottom sediment samples taken 10 m from the submarine along... 

Two methods of comparison, the sample dividing method and the reference sample method , were adopted for comparing the results of radionuclide analysis. 

Typical effects of the separation methods on the partition coefficient have been studies by Calmano (1979). Data from radionuclide analysis in Table 4-2 indicate that distribution coefficients between solid and aqueous phases generally are higher from filtration methods than from centrifuge separation for cesium and chromium the difference is a factor of about 10, for iron even higher. 

Radionuclide analysis methods are published in analytical chemistry and radiochemistry journals, and in methods manuals issued by nuclear facilities such as government laboratories. For example, the Environmental Measurements Laboratory Procedures manual, HASL-300 (Chieco 1997), is an excellent source. Standard methods for radionuclide analysis (see Section 6.7) are available, and should be used whenever appropriate. If conditions differ from those to which published methods have been applied, radionuclide recovery and decontamination must be tested and additional process steps may have to be inserted. 

A sample prepared for radionuclide analysis generally should be completely dissolved, without residual solids that could retain radionuclides. In contrast, stable-element analysis permits residual solids if the dissolution process has been demonstrated to dissolve completely the substance of interest. 

Processing solids by leaching—i.e., incomplete dissolution of the matrix— is acceptable for radionuclide analysis only if knowledge of the retention process supported by leaching tests assures that the radionuclides of interest are leached to a reproducible extent. Without positive knowledge that leaching recovers large and consistent fractions of the radionuclides of interest, results are uncertain. 

The sample may arrive unliltered or separated as filtered water and the filter that contains the solids. The water sample is preserved with dilute acid or a preservative suitable for a radionuclide such as 1 that may be lost from an acid solution. Water without suspended solids is ready for evaporation to measure the gross alpha- and beta-particle activity, measure gamma rays by spectral analysis, and perform radiochemical analysis. The solids usually are counted similarly and then processed for dissolution as described in Section 6.2.1 for subsequent radionuclide analysis. 

The liquid waste in the second tank is treated by adjusting the pH to >5.2 and then sampled for radionuclide analysis. If the concentration is acceptable, then the tank may be discharged to the sanitary sewage system. If the concentration exceeds release limits, several options may be considered. The three simplest are ... 

Access between the two appropriately labeled radiation areas should be restricted, in order to avoid contaminating the low-level area. In laboratories where both hot and cold operations are being performed in a small amount of space, it is important to set up well-defined and clearly labeled radioactive material work stations. In this way, radionuclide analysis is confined so that its impact on the surrounding laboratory is minimal. The presence of radiation throughout the laboratory should be monitored as discussed below. 

Automated Laboratory and Field Radionuclide Analysis Systems... 

The user friendliness of major MS methods for radionuclide analysis varies widely. The commercially available ICP/MS instrument is highly automated. Minimally trained staff can operate it for routine work when supported by trained maintenance staff. The TIMS instrument also can be obtained as a highly automated system, but greater operator skill generally is required than for ICP/MS to achieve a comparable level of data quality. Likewise, the SIMS instrument is complex, both from an operational aspect, as well as for calibration and interpretation of... 

At the heart of the TIMS ion source are one or more hot filaments that serve to vaporize and ionize atoms or molecules of interest. Once generated, the ions are accelerated, focused, and directed into the mass analyzer for measurement. The classic TIMS instrument consists of an ion source, a single magnetic sector mass separator, and an ion detector. Such an instrument is capable of measuring isotope ratios as small as 1 x 10 6, sufficient for the isotopic analysis of most elements. For radionuclide analysis, smaller isotope ratios are often encountered. Specialized mass spectrometers include multiple magnetic and electric sectors and sector instruments with retarding quadrupole lenses (Smith, 2000) to measure down to the 10-9 range. 

The laser typically used for laser ablation is the frequency quadrupled Nd YAG (266 nm) with a pulse width of a few nanoseconds. With this laser, some fractionation will occur. Unless a good external standard is used, quantification of the elements in the sample is difficult if not impossible. This is not an impediment to use of laser ablation in the field of radiochemistry or radionuclides. One of the most important aspects of radionuclide analysis is determining isotope ratios of elements of interest. All isotopes of a particular element behave the same when removed from a solid sample by a laser pulse. Ionization of those isotopes can depend on the laser bandwidth and polarization so care must be used when using lasers for direct ionization of atomic species. 

Accordingly, if a definite hazard is to be assessed, i.e. if the exceeding of individual limit values is to be established, there is no further option but to carry out a selective radionuclide analysis when effecting measurement. This analysis consists of a combination of radiochemistry and spectrometry and can be extremely involved. 

Presently, gamma-ray spectrometry is the most powerful tool in the field of radionuclide analysis. It is used for the qualitative and quantitative determination of radionuclides that emit gamma radiation. Most of the radionuclides send out gamma radiation during their transformations to stable decay products. 

Ramola, R.C., Choubey, V.M., Prasad, G. et al. (2011). Radionuclide analysis in the soil of Kumaun Himalaya, India using gamma ray spectrometry, Curr. Sci. 100, 906-914. 

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