【国外标准】 Standard Practice for Determination of Tc-99 in Water by Inductively Coupled Plasma Mass Spectrometry (ICP-MS)

5.1 Technetium-99 is produced by the fission of uranium and plutonium, and has been released to the environment via nuclear weapons testing and nuclear materials processing. In an oxidizing environment, it exists as the very mobile pertechnetate ion, TcO4–, which is an analog to nitrate and can be taken up by living organisms. Monitoring of 99Tc in waters around nuclear processing facilities is part of a complete environmental monitoring program.5.2 Technetium-99 is a long-lived (half-life 2.1E+5years), weak beta (maximum beta energy of 293 keV) emitting radioisotope. There are no stable isotopes of Tc. Thus the determination of its activity concentration presents unique challenges to traditional radiochemical determination methods. This method provides an alternative to the spiked/unspiked replicate method of Method D7168 and uses options presented in Guide C1387 for the determination of 99Tc in soil.1.1 Technetium is separated and concentrated from a water sample by extraction chromatography using its chemical analog, rhenium, as a tracer. The ratio of technetium to rhenium is measured by inductively coupled plasma mass spectrometry (ICP-MS) to then quantify the 99Tc concentration.1.1.1 This practice is provided as an alternative to Test Method D7168 which provides for a different separation media geometry and measurement by liquid scintillation spectrometry. Similar detection limits should be attainable by this method.1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.3 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.