JRC’s contribution to international standards demonstrates how its expertise (knowledge production) is disseminated (knowledge transfer), leading to the implementation of new standards applicable in nuclear material analysis, accountancy and safeguards.
Standards for test methods in nuclear mass spectrometry are indispensable for the implementation of safeguards in the front-end of the nuclear fuel cycle, and in particular in the uranium enrichment phase, which represents a major priority for EURATOM and IAEA safeguards.
These standards are also widely used in the fields of geochemistry and cosmochemistry, reaching out to non-energy nuclear applications This JRC activity also strengthens JRC's relation with industry (EUR 28753 EN).
Standardised test methods
Standardised test methods are important to compare results achieved in laboratories worldwide. They are also subject to regular review and development.
The JRC collaborates with international bodies and organisations to harmonise scientific techniques and standardise analytical processes. ASTM International (American Society for Testing and Materials) is one of the global providers of voluntary consensus standards, including standards in the area of nuclear measurements.
Standard test methods for Thermal Ionisation Mass Spectrometry (TIMS)
ASTM C1832-21: The JRC-developed the Standard Test Method for Determination of Uranium Isotopic Composition by Modified Total Evaporation (MTE) Method Using Thermal Ionization Mass Spectrometer. This is a method for routine TIMS measurements of uranium isotope ratios with improved precision and accuracy for major (235U/238U) and minor isotope ratios (234U/238U and 236U/238U)
ASTM C1672-17: Standard Test Method for Determination of Uranium or Plutonium Isotopic Compo-sition or Concentration by the Total Evaporation Method Using a Thermal Ionization Mass Spectrometer. The total evaporation method allows for a wide range of sample loading with no significant change in precision or accuracy. The method is also suitable for trace-level loadings with some loss of precision and accuracy.
ASTM C1871-18: Standard Test Method for Determination of Uranium Isotopic Composition by the Double Spike Method Using a Thermal Ionization Mass Spectrometer. The double spike method has been used for studies of uranium fractionation effects in isotope geochemistry and cosmochemistry, for uranium source attribution in nuclear forensics and for investigation of conversion or sampling processes in nuclear industry and nuclear safeguards..
Uranium hexafluoride (UF6) gas source mass spectrometry
Facility operators and safeguards inspectors routinely take UF6 samples from processing lines, isotopic enrichment cascades or storage cylinders to determine their U isotopic composition, and most importantly the n(235U)/n(238U) isotope ratio, needed to calculate the amount of fissile 235U in the sample. Conventional sampling practices collect samples of UF6, usually in quantities greater than one gram and air transport operators are unwilling to transport such samples.
ASTM C1880-19: Standard Practice for Sampling Gaseous Uranium Hexafluoride using Alumina Pellets. “Cristallini" sampling method for UF6 by adsorption and hydrolysis of UF6 gas in alumina pellets inside a fluorothene P-10 tube, using the sorbent properties of aluminum oxide (Al2O3) for cheaper and safer nuclear transport.
ASTM C1913-21: Standard Practice for Sampling Gaseous Uranium Hexafluoride Using Zeolite in Single-Use Destructive Assay Sampler. SUDA samples are expected to be transported as “excepted small quantities” package because the conversion to a less hazardous, more stable chemical species avoids the chemical hazards of UF6.
Future objectives and challenges
The JRC continues the work on standardisation in order to include all relevant test methods to enhance the worldwide use of standardised methods for nuclear mass spectrometry measurement.
Meanwhile, the JRC transfers the knowledge of implementing standardised test methods in safeguards laboratories and promotes standardisation and a harmonised measurement system for the benefit of nuclear safeguards & security, the nuclear industry but also research institutions beyond the nuclear field.