Standard Practice for Sampling Gaseous Uranium Hexafluoride Using Zeolite in Single-Use Destructive Assay Sampler

Importancia y uso:

5.1 Facility operators and safeguards inspectors routinely collect UF₆ samples from processing lines, isotopic enrichment cascades or storage cylinders to determine uranium isotopic composition. The isotope ratio n(²³⁵U)/n(²³⁸U) is particularly important since it is used to calculate the amount of fissile ²³⁵U in the sample.

5.2 Conventional sampling practices (such as Practices C1052 and C1703) collect samples of UF₆, usually in quantities greater than one gram. Due to the chemical hazards of UF₆ (and in some cases the high collection mass), an increasing number of air transport operators are unwilling to transport such samples. In contrast, SUDA samples are expected to be transported as excepted quantities (for example, under UN 2910 (3)), as the conversion to a less hazardous, more stable chemical species avoids the chemical hazards of UF₆ similar to Practice C1880. Additionally, the decreased shipping requirement and small collection mass of SUDA samplers (less than Practice C1880) allow for multiple SUDA samples to be transported in the same shipment.

5.3 For safeguards applications, isotopic measurements that fall within the 2010 International Target Value (ITV) ranges (5) have been demonstrated (1).

5.4 This practice provides the following qualities:

5.4.1 Fitness for purpose in verifying nuclear material declarations.

5.4.2 A safe, simple and fast procedure for the sample collector that minimizes sample handling and potential for cross-contamination.

5.4.3 Flexibility for use in a wide variety of facilities.

5.4.4 Robustness to adapt to minor changes in facility operating parameters.

5.4.5 Confidentiality for the operating facility from which the sample is collected.

5.4.6 Safety in sample handling and transport since the sample is a less hazardous, more stable form (specifically, UO₂F₂ is more stable and less volatile than UF₆ gas).

5.4.7 Ease of sample preparation in the laboratory with reduced processing hazards during recovery of the uranium content (1).

5.5 Samples collected using this practice are suitable for determination of uranium isotopic composition, as described in 4.5, for safeguards applications. Care must be taken to ensure cleanliness of the sampling tap to be used for SUDA samples, as any UF₆ holdup in the sampling tap from previous sample collection could affect sample collection and isotopic measurements (see Section 9 for further details regarding this issue). Other applications of this practice are possible but require validation prior to use.

Subcomité:

C26.02

Volúmen:

12.01

Número ICS:

27.120.30 (Fissile materials and nuclear fuel technology)

Palabras clave:

enrichment; nuclear material safeguards; uranium hexafluoride sampling; uranium isotope ratios; uranium isotopic composition;