【国外标准】 Standard Practice for The Ion Exchange Separation of Small Volume Samples Containing Uranium, Americium, and Plutonium Prior to Isotopic Abundance and Content Analysis

5.1 Uranium and plutonium are used in nuclear reactor fuel and must be analyzed to ensure that they meet acceptance criteria for isotopic composition as described in Specifications C833 and C1008. The criteria are set by mutual agreement between the manufacturer and end user (or between buyer and seller). This standard practice is used to separate chemically the isobaric interferences from 238U and 238Pu and from 241Am and 241Pu, and from other impurities prior to isotopic abundance determination by TIMS.5.2 In facilities where perchloric acid use is authorized, the separation in Test Method C698 may be used prior to isotopic abundance determination. Uranium and plutonium content as well as isotopic abundances using TIMS can be determined by using this separation practice and by following Test Methods C698, C1625, or C1672.1.1 This practice is an alternative to Practice C1411 for the ion exchange separation in small mass samples (~5 μg of plutonium and up to 0.5 mg of uranium in 1 mL of solution) of uranium and plutonium from each other and from other impurities for subsequent isotopic abundance and content analysis by thermal ionization mass spectrometry (TIMS). In addition to being adapted to smaller sample sizes, this practice also avoids the use of hydrochloric acid (HCl) and hydrofluoric acid (HF) and does not require the use of two anion exchange columns as required in Practice C1411.1.2 In chemically unseparated samples isobaric nuclides at mass 238 (238U and 238Pu), and mass 241 (241Pu and 241Am) will be measured together thus compromising the accuracy of the results of isotopic composition of Pu. Therefore, chemical separation of elements is essential prior to isotopic analyses. Concentrations and volumes given in the paragraphs below can be modified for larger sample sizes, different types of anion exchange resin, etc.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 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.