- List
- NSG – Trigger List (Part 1) – INFCIRC/254/Rev.15/Part 1 (21 April 2026)
INTRODUCTORY NOTE
Uranium conversion plants and systems may perform one or more transformations from one uranium chemical species to another, including: conversion of uranium ore concentrates to uranium trioxide (UO₃), conversion of UO₃ to uranium dioxide (UO₂), conversion of uranium oxides to uranium tetrafluoride (UF₄), UF₆, or UCl₄, conversion of UF₄ to UF₆, conversion of UF₆ to UF₄, conversion of UF₄ to uranium metal, and conversion of uranium fluorides to UO₂. Many of the key equipment items for uranium conversion plants are common to several segments of the chemical process industry. For example, the types of equipment employed in these processes may include: furnaces, rotary kilns, fluidised bed reactors, flame tower reactors, liquid centrifuges, distillation columns and liquid-liquid extraction columns. However, few of the items are available ‘off-the-shelf’; most would be prepared according to the requirements and specifications of the customer. In some instances, special design and construction considerations are required to address the corrosive properties of some of the chemicals handled (hydrogen fluoride (HF), fluorine (F₂), chlorine trifluoride (ClF₃), and uranium fluorides) as well as nuclear criticality concerns. Finally, it should be noted that, in all of the uranium conversion processes, items of equipment which individually are not especially designed or prepared for uranium conversion can be assembled into systems which are especially designed or prepared for use in uranium conversion.
7.1.1. Especially designed or prepared systems for the conversion of uranium ore concentrates to UO₃
EXPLANATORY NOTE
Conversion of uranium ore concentrates to UO₃ can be performed by first dissolving the ore in nitric acid and extracting purified uranyl nitrate (UO₂(NO₃)₂)using a solvent such as tributyl phosphate (TBP). Next, the uranyl nitrate is converted to UO₃ either by concentration and denitration or by neutralisation with gaseous NH₃ to produce ammonium diuranate with subsequent filtering, drying, and calcining.
7.1.2. Especially designed or prepared systems for the conversion of UO₃ to UF₆
EXPLANATORY NOTE
Conversion of UO₃ to UF₆ can be performed directly by fluorination. The process requires a source of F₂ or ClF₃.
7.1.3. Especially designed or prepared systems for the conversion of UO₃ to UO₂
EXPLANATORY NOTE
Conversion of UO₃ to UO₂ can be performed through reduction of UO₃ with cracked gaseous NH₃ or hydrogen.
7.1.4. Especially designed or prepared systems for the conversion of UO₂ to UF₄
EXPLANATORY NOTE
Conversion of UO₂ to UF₄ can be performed by reacting UO₂ with gaseous HF at 573773 K (300-500°C).
7.1.5. Especially designed or prepared systems for the conversion of UF₄ to UF₆
EXPLANATORY NOTE
Conversion of UF₄ to UF₆ is performed by exothermic reaction with fluorine in a tower reactor. UF₆ is condensed from the hot effluent gases by passing the effluent stream through a cold trap cooled to 263 K (-10°C). The process requires a source of gaseous F₂.
7.1.6. Especially designed or prepared systems for the conversion of UF₄ to uranium metal
EXPLANATORY NOTE
Conversion of UF₄ to uranium metal is performed by reduction with magnesium (large batches) or calcium (small batches). The reaction is carried out at temperatures above the melting point of uranium (1403 K (1130 °C)).
7.1.7. Especially designed or prepared systems for the conversion of UF₆ to UO₂
EXPLANATORY NOTE
Conversion of UF₆ to UO₂ can be performed by one of three processes. In the first, UF₆ is reduced and hydrolysed to UO₂ using hydrogen and steam. In the second, UF₆ is hydrolysed by solution in water, NH₃ is added to precipitate ammonium diuranate, and the diuranate is reduced to UO₂ with hydrogen at 1093 K (820 °C). In the third process, gaseous UF₆, CO₂, and NH₃ are combined in water, precipitating ammonium uranyl carbonate. The ammonium uranyl carbonate is combined with steam and hydrogen at 773-873 K (500-600 °C) to yield UO₂.
UF₆ to UO₂ conversion is often performed as the first stage of a fuel fabrication plant.
7.1.8. Especially designed or prepared systems for the conversion of UF₆ to UF₄
EXPLANATORY NOTE
Conversion of UF₆ to UF₄ is performed by reduction with hydrogen.
7.1.9. Especially designed or prepared systems for the conversion of UO₂ to UCl₄
EXPLANATORY NOTE
Conversion of UO₂ to UCl₄ can be performed by one of two processes. In the first, UO₂ is reacted with carbon tetrachloride (CCl₄) at approximately 673 K (400 °C). In the second, UO₂ is reacted at approximately 973 K (700 °C) in the presence of carbon black (CAS 1333-86-4), carbon monoxide, and chlorine to yield UCl₄.
Uranium conversion plants and systems may perform one or more transformations from one uranium chemical species to another, including: conversion of uranium ore concentrates to uranium trioxide (UO₃), conversion of UO₃ to uranium dioxide (UO₂), conversion of uranium oxides to uranium tetrafluoride (UF₄), UF₆, or UCl₄, conversion of UF₄ to UF₆, conversion of UF₆ to UF₄, conversion of UF₄ to uranium metal, and conversion of uranium fluorides to UO₂. Many of the key equipment items for uranium conversion plants are common to several segments of the chemical process industry. For example, the types of equipment employed in these processes may include: furnaces, rotary kilns, fluidised bed reactors, flame tower reactors, liquid centrifuges, distillation columns and liquid-liquid extraction columns. However, few of the items are available ‘off-the-shelf’; most would be prepared according to the requirements and specifications of the customer. In some instances, special design and construction considerations are required to address the corrosive properties of some of the chemicals handled (hydrogen fluoride (HF), fluorine (F₂), chlorine trifluoride (ClF₃), and uranium fluorides) as well as nuclear criticality concerns. Finally, it should be noted that, in all of the uranium conversion processes, items of equipment which individually are not especially designed or prepared for uranium conversion can be assembled into systems which are especially designed or prepared for use in uranium conversion.
7.1.1. Especially designed or prepared systems for the conversion of uranium ore concentrates to UO₃
EXPLANATORY NOTE
Conversion of uranium ore concentrates to UO₃ can be performed by first dissolving the ore in nitric acid and extracting purified uranyl nitrate (UO₂(NO₃)₂)using a solvent such as tributyl phosphate (TBP). Next, the uranyl nitrate is converted to UO₃ either by concentration and denitration or by neutralisation with gaseous NH₃ to produce ammonium diuranate with subsequent filtering, drying, and calcining.
7.1.2. Especially designed or prepared systems for the conversion of UO₃ to UF₆
EXPLANATORY NOTE
Conversion of UO₃ to UF₆ can be performed directly by fluorination. The process requires a source of F₂ or ClF₃.
7.1.3. Especially designed or prepared systems for the conversion of UO₃ to UO₂
EXPLANATORY NOTE
Conversion of UO₃ to UO₂ can be performed through reduction of UO₃ with cracked gaseous NH₃ or hydrogen.
7.1.4. Especially designed or prepared systems for the conversion of UO₂ to UF₄
EXPLANATORY NOTE
Conversion of UO₂ to UF₄ can be performed by reacting UO₂ with gaseous HF at 573773 K (300-500°C).
7.1.5. Especially designed or prepared systems for the conversion of UF₄ to UF₆
EXPLANATORY NOTE
Conversion of UF₄ to UF₆ is performed by exothermic reaction with fluorine in a tower reactor. UF₆ is condensed from the hot effluent gases by passing the effluent stream through a cold trap cooled to 263 K (-10°C). The process requires a source of gaseous F₂.
7.1.6. Especially designed or prepared systems for the conversion of UF₄ to uranium metal
EXPLANATORY NOTE
Conversion of UF₄ to uranium metal is performed by reduction with magnesium (large batches) or calcium (small batches). The reaction is carried out at temperatures above the melting point of uranium (1403 K (1130 °C)).
7.1.7. Especially designed or prepared systems for the conversion of UF₆ to UO₂
EXPLANATORY NOTE
Conversion of UF₆ to UO₂ can be performed by one of three processes. In the first, UF₆ is reduced and hydrolysed to UO₂ using hydrogen and steam. In the second, UF₆ is hydrolysed by solution in water, NH₃ is added to precipitate ammonium diuranate, and the diuranate is reduced to UO₂ with hydrogen at 1093 K (820 °C). In the third process, gaseous UF₆, CO₂, and NH₃ are combined in water, precipitating ammonium uranyl carbonate. The ammonium uranyl carbonate is combined with steam and hydrogen at 773-873 K (500-600 °C) to yield UO₂.
UF₆ to UO₂ conversion is often performed as the first stage of a fuel fabrication plant.
7.1.8. Especially designed or prepared systems for the conversion of UF₆ to UF₄
EXPLANATORY NOTE
Conversion of UF₆ to UF₄ is performed by reduction with hydrogen.
7.1.9. Especially designed or prepared systems for the conversion of UO₂ to UCl₄
EXPLANATORY NOTE
Conversion of UO₂ to UCl₄ can be performed by one of two processes. In the first, UO₂ is reacted with carbon tetrachloride (CCl₄) at approximately 673 K (400 °C). In the second, UO₂ is reacted at approximately 973 K (700 °C) in the presence of carbon black (CAS 1333-86-4), carbon monoxide, and chlorine to yield UCl₄.