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[en] The process of conversion of UF6 to UO2 through Integrated Dry Route (IDR) is done in a rotary kiln reactor. There are two stages of initial treatment / conditioning before inserting the UF6 in to the reactor: changing UF6 solid into the gas phase at a temperature of 60°C in an evaporator, and then, raising the temperature of UF6 gas from 60°C to 290°C in a Heat Exchanger (HE). Therefore it is necessary to design a HE for heating UF6 gas by determination / calculation of HE specifications as a heater. The steps activities of determining the specifications of HE in the Following sequence: determining the value of the heat load Q, determining the approximate dimensions of the Heat Exchanger, determining the dimensions / specifications corrected Heat Exchanger, HE pressure drop calculation. The result of this design specification is a type of hairpin double pipe HE with a length of 12 ft, 2 x 1 ¼. IPS. Pipe material is Inconel (alloy -600) that is resistant to UF6, HF, and Steam. Annulus material is carbon steel. Pressure drop in annulus is 0.0004 psi, and in inner pipe is 0.042 psi. Heat Exchanger with specs like this can function as UF6 gas heater so that the temperature be 290°C. (author)
[en] Holdup in processing UF6 is analyzed in the present article. Under normal operation conditions of temperature and pressure, UF6 stays in gas phase. While if water moisture ingresses, chemical reaction between UF6 and moisture results in solid or liquid productions that can deposit on structure surfaces. The present report focuses on the chemistry of holdup and how to measure it, and safeguards and criticality safety concerns. An available statistic theoretical model is also discussed. (author)
[en] The purpose of this article is to use SLAB model and HGSYSTEM/UF6 model, to build the near source field evaluation model after UF6 leakage accidents. And based on the data of three UF6 release experiments carried by the French Bordeaux National Experimental Base, it tested the model preliminarily. It turned out that the model can simulate atmospheric diffusion and migration in the near source field after UF6 leakage very well (P/O = 1.0-2.4), the simulation results errors are acceptable. It also aims to provide theory basis for the later large model program development, and offer help for more precision simulation of contaminants transfer after UF6 leakage accidents. (authors)
[en] The DN30 package was developed by Daher Nuclear Technologies GmbH (DNT) for the transport of enriched commercial grade and reprocessed UF6 up to an enrichment of 5 %. It consists of a standard 30B cylinder and the DN30 Protective Structural Packaging (PSP) and is licensed as a type AF, IF and B(U)F package. Due to its chemical and physical properties, enriched UF6 presents several challenges to criticality safety that have to be taken into account for the safety assessment of the DN30 package. The assessment is based on variation calculations of criticality relevant parameters such as geometry and material composition for individual packages in isolation and arrays of packages. Single packages and infinite 3D arrays of packages were simulated to figure out most reactive arrangements and prove criticality safety. Since UF6 in 30B cylinders is under-moderated, the consideration of conservative amounts of moderation and the impact of their geometrical distribution on reactivity are of paramount importance. This involves the determination of all possible moderation sources, not only those resulting from inherent impurities in UF6, but also from the interaction of the UF6 content with in-leaking water vapor. Regarding impurities, the criticality analysis assumes up to 0.5 wt.% HF, and also takes new findings about hydrogenated uranium residues into account. Based on these potential quantities of moderation, the criticality analysis is performed for a variety of geometrical fuel/moderator distributions by means of conservative calculation models, incorporating accident conditions of transport and effects related to the physical properties of UF6. Criticality safety was proven for the DN30 package even for very conservative, hypothetical assumptions that are unlikely to be encountered in actual packaging, transportation, and storage configurations. In addition to the overview of the criticality analysis for the newly licensed DN30 package, an outlook on potential design optimizations for higher uranium enrichments will also be presented. (authors)
[en] This paper is a continuation of the Advanced Enrichment Monitoring Technology for UF6 Gas Centrifuge Enrichment Plant (GCEP) work, presented in the 2010 IAEA Safeguards Symposium. Here we will present the system architecture for a planned side-by-side field trial test of passive (186-keV line spectroscopy and pressure-based correction for UF6 gas density) and active (186-keV line spectroscopy and transmission measurement based correction for UF6 gas density) enrichment monitoring systems in URENCO’s enrichment plant in Capenhurst. Because the pressure and transmission measurements of UF6 are complementary, additional information on the importance of the presence of light gases and the UF6 gas temperature can be obtained by cross-correlation between simultaneous measurements of transmission, pressure and 186-keV intensity. We will discuss the calibration issues and performance in the context of accurate, on-line enrichment measurement. It is hoped that a simple and accurate on-line enrichment monitor can be built using the UF6 gas pressure provided by the Operator, based on online mass spectrometer calibration, assuming a negligible (a small fraction of percent) contribution of wall deposits. Unaccounted-for wall deposits present at the initial calibration will lead to unwanted sensitivity to changes in theUF6 gas pressure and thus to error in the enrichment results. Because the accumulated deposits in the cascade header pipe have been identified as an issue for Go/No Go measurements with the Cascade Header Enrichment Monitor (CHEM) and Continuous Enrichment Monitor (CEMO), it is important to explore their effect. Therefore we present the expected uncertainty on enrichment measurements obtained by propagating the errors introduced by deposits, gas density, etc. and will discuss the options for a deposit correction during initial calibration of an On-Line Enrichment Monitor (OLEM).
[en] This paper recommends the use of radiation detectors, singly or in sets, to trigger surveillance cameras. Ideally, the cameras will monitor cylinders transiting the process area as well as the process area itself. The general process area will be surveyed to record how many cylinders have been attached and detached to the process between inspections. Rad-triggered cameras can dramatically reduce the quantity of recorded images, because the movement of personnel and equipment not involving UF6 cylinders will not generate a surveillance review file.
[en] In May 2014, the World Nuclear Transport Institute (WNTI) formed an ad-hoc working group to focus on the identification of uranium hexafluoride (UF6) cylinders. WNTI was founded in 1998 to represent the collective interests of the nuclear transport industry, and those who rely upon the safe, secure, efficient, and reliable packaging and transport of radioactive materials. The working group scope, adopted by over 25 members, is to establish an industry-wide identification format that provide for uniquely identifying UF6 cylinders and to investigate methods for making the unique identifier (UID) machine-readable and independently verifiable by the International Atomic Energy Agency (IAEA). The working group held multiple conference calls and two face-to-face meeting amongst its members in December 2014 and 2015, in conjunction with the WNTI semiannual meeting in London, England. The primary focuses for 2016 are to provide a set of consensus recommendations for a preferred identification format and technology for machine readability and to participate in field testing, as needed, of key functional features. (author)
[en] The present article reviews a selection of results obtained in the AREVA/CNRS/UCA joint research laboratory. It focuses on interfaces formed by uranium hexafluoride (UF6) with chemical filter (purification), carbon (UF6 storage), and metallic substrate (corrosion). As a matter of fact, along the nuclear fuel cycle, metallic surfaces of the fluorination reactors, cooling systems (for the liquefaction of UF6), and storage containers are in contact with UF6, either in the gas or in the liquid phase. For the removal of volatile impurities before the enrichment, surface of chemical filters with a high specific surface area must be enhanced for both selectivity and efficiency. To store depleted UF6 (238U), graphite intercalation compounds are proposed and preliminary results are presented. (authors)