1.1 This method describes the determination of the isotopic composition and/or the concentration of uranium and plutonium as nitrate solutions by the thermal ionization mass spectrometric (TIMS) total evaporation method. Purified uranium or plutonium nitrate solutions are loaded onto a degassed metal filament and placed in the mass spectrometer. Under computer control, ion currents are generated by heating of the filament(s). The ion beams are continually measured until the sample is exhausted. The measured ion currents are integrated over the course of the run, and normalized to a reference isotope ion current to yield isotopic ratios.

1.2 In principle, the total evaporation method should yield isotopic ratios that do not require mass bias correction. In practice, some samples may require this bias correction. When compared to the conventional TIMS method, the total evaporation method is approximately two times faster, improves precision from two to four fold, and utilizes smaller sample sizes.

1.3 The total evaporation method may lead to biases in minor isotope ratios due to peak tailing from adjacent major isotopes, depending on sample characteristics. The use of an electron multiplier equipped with an energy filter may eliminate or diminish peak tailing effects. Measurement of instrument abundance sensitivity may be used to ensure that such biases are negligible, or may be used to bias correct minor isotope ratios.

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.

2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

ASTM Standards

C753 Specification for Nuclear-Grade, Sinterable Uranium Dioxide Powder

C757 Specification for Nuclear-Grade Plutonium Dioxide Powder, Sinterable

C776 Specification for Sintered Uranium Dioxide Pellets

C787 Specification for Uranium Hexafluoride for Enrichment

C833 Specification for Sintered (Uranium-Plutonium) Dioxide Pellets

C967 Specification for Uranium Ore Concentrate

C996 Specification for Uranium Hexafluoride Enriched to Less Than 5 % 235U

C1008 Specification for Sintered (Uranium-Plutonium) Dioxide Pellets--Fast Reactor Fuel

C1068 Guide for Qualification of Measurement Methods by a Laboratory Within the Nuclear Industry

C1156 Guide for Establishing Calibration for a Measurement Method Used to Analyze Nuclear Fuel Cycle Materials

C1168 Practice for Preparation and Dissolution of Plutonium Materials for Analysis

C1347 Practice for Preparation and Dissolution of Uranium Materials for Analysis

C1411 Practice for The Ion Exchange Separation of Uranium and Plutonium Prior to Isotopic Analysis

C1415 Test Method for 238Pu Isotopic Abundance By Alpha Spectrometry

D3084 Practice for Alpha-Particle Spectrometry of Water

E137 Practice for Evaluation of Mass Spectrometers for Quantitative Analysis from a Batch Inlet

Keywords

atom percent; isotope dilution mass spectrometry; isotopic composition; mass fractionation; plutonium; thermal ionization mass spectrometry; total evaporation; uranium; weight percent;

ICS Code

ICS Number Code 27.120.30 (Fissile materials and nuclear fuel technology)

Citing ASTM Standards

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