HASL, EML In 1977, the Energy Research and Development Administration's Health and Safety Laboratory (HASL) became a part of the U.S. Department of Energy as the Environmental Measurements Laboratory (EML). During the next two decades it performed extensive studies in radiation transport and dosimetry and established the Quality Assurance Program for environmental dosimeters and radioanalytical measurements. The lab also performed dose reconstructions for nuclear weapons tests, studied radon in homes. Since 1957, the EML Procedures Manual, HASL-300, has served as a significant resource for scientists throughout the world who collect samples, perform field measurements or analyze samples. The Manual includes sections on Quality Assurance, Sampling Techniques, Radiation Measurements, Analytical Chemistry Procedures, Radionuclide Data, EML Special Facilities, and Specifications for Equipment and Supplies. The Manual is no longer being updated and printed copies are no longer available.
Extensive experimental evidence indicates that variable and incomplete sample dissolution is one of the major causes of the inaccurate results being obtained widely in radiochemical analysis. This conclusion is easily demonstrated by analysis of the residues remaining after the sample has been leached. The residue often contains a significant fraction of the radionuclide being determined. Three procedures involving high-temperature fusions are recommended that ensure complete dissolution of virtually all types of inorganic samples routinely and reliably. With a few unique exceptions encountered over many years of constant use, dissolution of the entire matrix has been so complete that a Tyndall beam could not be observed when the solution of the final fusion cake was examined with a flashlight in a darkened room. Complete material balance studies using radioactive tracers have also shown no significant losses of even the large terand quadrivalent radionuclides that could be attributed to incomplete dissolution of high specific-activity particles of the most refractory and intractable species. The recommended fusion procedures are no more hazardous, time-consuming or difficult than other procedures giving much less complete or reliable dissolution.
Several techniques of sample attack for the determination of radioisotopes are reviewed. These techniques include 1) digestion with nitric or hydrochloric acid in Parr digestion bomb, 2) digestion with a mixture of nitric and hydrochloric acids, 3) digestion with a mixture of hydrofluoric, nitric and perchloric acids, and 4) fusion with sodium carbonate, potassium fluoride or alkali pyrosulfates. The effectiveness of these techniques to decompose various soils and minerals containing radioisotopes such as lead-210 uranium, thorium and radium-226 are discussed.
Simultaneous determination of all alpha activity has always been and continues to be a highly desirable option in radiochemical analysis. However, the usual practice of gross alpha counting samples of raw water evaporated to dryness in planchets, air dusts collected on filters, planchets full of soils, etc., and then reporting the results quantitatively is neither accurate nor reliable, since it is virtually impossible to determine the correct counting efficiency with which the count was actually made. Attempts to calibrate empirically for a given set of conditions are also of marginal value because of wide variability in the deposition patterns. Direct gross alpha counting of samples without chemical preparation is useful when the activity present is substantially higher than that from the natural activity in its surroundings, or when a rapid order-of-magnitude indication of alpha activity is desired. All too often the results of these screening methods are reported with precision and accuracy that they cannot possibly have. Even is excess alpha activity is indicated, a gross alpha count cannot distinguish between a man-made transuranium (TRU) radionuclide and a naturally occurring one. The current procedure provides a true total alpha while eliminating the problems just discussed.
(A fee may be required to access this article.) Samples of siliceous solids up to 1 g were dissolved completely by successive fusions with potassium fluoride and pyrosulfate in platinum dishes in the presence of appropriate tracers. Samples which contaminate or react deleteriously with platinum were treated extensively with hydrofluoric and perchloric acids before fusion with pyrosulfate in glass. The pyrosulfate cake was dissolved in dilute hydrochloric acid and the actinides were precipitated isomorphously with barium sulfate. The barium sulfate was dissolved in alkaline ethylenediaminetetraacetic acid (EDTA), and the actinides were precipitated as the hydroxides, filtered on a membrane filter and analyzed in an alpha spectrometer. When necessary, the hydroxides were converted to fluorides in the presence of various oxidizing agents to obtain improved resolution and additional separations. Isotopes of all elements from thorium through curium can be determined in one sequential procedure. The procedure was simpler and faster than others available, with higher yields and greater reliability. Resolution of the subsequent alpha spectra was comparable to that obtained by electrodeposition. The results were reproduced with a relative standard deviation of 1 to 2%. The accuracy of the determination on standards was generally as good as the statistical uncertainty of the measurement permits. Some results of actinides in pond sediments, incinerator ash, baghouse dusts, and ion exchange resins are given.
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