Significance and Use
The test methods in this standard may be used to measure the concentrations of 99Tc, 230Th, and 234U in soil samples. The test methods are applicable to soils that have been contaminated by nuclear-related activities such as uranium ore processing and uranium enrichment. The FI concentration step reduces detection limits by approximately a factor of ten compared to ICP-MS with conventional sample introduction. Approximate IDLs are listed in Table 1.
Scope
1.1 This test method covers a procedure for measuring 99Tc and a procedure for measuring 230Th and 234U in soils. It is applicable to background soils and soils that have been contaminated by nuclear processes. It is intended as an alternative to radiochemical methods because it is faster, requires less labor, and produces less waste than many radiochemical methods.
1.2 Samples are dried, ground, dissolved by fusion, and analyzed by inductively coupled plasma-mass spectrometry (ICP-MS). A sequential flow injection (FI) technique is used to provide lower detection limits than those obtained with direct aspiration into an ICP-MS, and, in the case of 99Tc, provides separation from interferences.
1.3 The 230Th and 234U procedure also would work for 232Th, 235U, and 238U, but the FI preconcentration usually is not required to measure these isotopes at the concentrations typically found in soils.
1.4 This test method is guided by quality control procedures derived from U.S. EPA procedures for inorganic analysis reported in SW-846 and the Contract Laboratory Program Statement of Work. The required level of quality control may vary between laboratories and projects. Laboratory statistical quality control procedures are required to ensure that this test method is reliable.
1.5 Becquerel (Bq) is the acceptable metric unit for radionuclide activity. However, picocurie (pCi) frequently is the unit used to express regulatory limits for radioactivity. The values stated in either of these units shall be regarded as standard. The values stated in each system may not be exact equivalents; therefore, each system must be used independently of the other, without combining values in any way.
1.6 Refer to Practice C 998 for information on soil sample collection.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
