- List
- NSG – Trigger List (Part 1) – INFCIRC/254/Rev.15/Part 1 (21 April 2026)
INTRODUCTORY NOTE
Present systems for enrichment processes using lasers fall into two categories: those in which the process medium is atomic uranium vapour and those in which the process medium is the vapour of a uranium compound, sometimes mixed with another gas or gases. Common nomenclature for such processes include:
- first category - atomic vapour laser isotope separation;
- second category - molecular laser isotope separation, including chemical reaction by isotope selective laser activation.
The systems, equipment and components for laser enrichment plants include:
(a) Devices to feed uranium-metal vapour (for selective photo-ionisation) or devices to feed the vapour of a uranium compound (for selective photo-dissociation or selective excitation/activation);
(b) Devices to collect enriched and depleted uranium metal as ‘product’ and ‘tails’ in the first category, and devices to collect enriched and depleted uranium compounds as ‘product’ and ‘tails’ in the second category;
(c) Process laser systems to selectively excite the uranium-235(²³⁵U)species;
(d) Feed preparation and product conversion equipment. The complexity of the spectroscopy of uranium atoms and compounds may require incorporation of any of a number of available laser and laser optics technologies.
EXPLANATORY NOTE
Many of the items listed in this section come into direct contact with uranium metal vapour or liquid or with process gas consisting of UF₆ or a mixture of UF₆ and other gases. All surfaces that come into direct contact with the uranium or UF₆ are wholly made of or protected by corrosion-resistant materials. For the purposes of the section relating to laser-based enrichment items, the materials resistant to corrosion by the vapour or liquid of uranium metal or uranium alloys include yttria-coated graphite and tantalum; and the materials resistant to corrosion by UF₆ include copper, copper alloys, stainless steel, aluminium, aluminium oxide, aluminium alloys, nickel or alloys containing 60% by weight or more nickel and fluorinated hydrocarbon polymers.
5.7.1. Uranium vaporisation systems (atomic vapour based methods)
Especially designed or prepared uranium metal vaporisation systems for use in laser enrichment.
EXPLANATORY NOTE
These systems may contain electron beam guns and are designed to achieve a delivered power (1 kW or greater) on the target sufficient to generate uranium metal vapour at a rate required for the laser enrichment function.
5.7.2. Liquid or vapour uranium metal handling systems and components (atomic vapour based methods)
Especially designed or prepared systems for handling molten uranium, molten uranium alloys or uranium metal vapour for use in laser enrichment, or especially designed or prepared components therefor.
EXPLANATORY NOTE
The liquid uranium metal handling systems may consist of crucibles and cooling equipment for the crucibles. The crucibles and other parts of this system that come into contact with molten uranium, molten uranium alloys or uranium metal vapour are made of or protected by materials of suitable corrosion and heat resistance. Suitable materials may include tantalum, yttria-coated graphite, graphite coated with other rare earth oxides (see INFCIRC/254/Part 2 as amended) or mixtures thereof.
5.7.3. Uranium metal ‘product’ and ‘tails’ collector assemblies (atomic vapour based methods)
Especially designed or prepared ‘product’ and ‘tails’ collector assemblies for collecting uranium metal in liquid or solid form.
EXPLANATORY NOTE
Components for these assemblies are made of or protected by materials resistant to the heat and corrosion of uranium metal vapour or liquid (such as yttria-coated graphite or tantalum) and may include pipes, valves, fittings, gutters, feed-throughs, heat exchangers and collector plates for magnetic, electrostatic or other separation methods.
5.7.4. Separator module housings (atomic vapour based methods)
Especially designed or prepared cylindrical or rectangular vessels for containing the uranium metal vapour source, the electron beam gun, and the ‘product’ and ‘tails’ collectors.
EXPLANATORY NOTE
These housings have multiplicity of ports for electrical and water feed-throughs, laser beam windows, vacuum pump connections and instrumentation diagnostics and monitoring. They have provisions for opening and closing to allow refurbishment of internal components.
5.7.5. Supersonic expansion nozzles (molecular based methods)
Especially designed or prepared supersonic expansion nozzles for cooling mixtures of UF₆ and carrier gas to 150 K (-123°C) or less and which are corrosion resistant to UF₆.
5.7.6. ‘Product’ or ‘tails’ collectors (molecular based methods)
Especially designed or prepared components or devices for collecting uranium product material or uranium tails material following illumination with laser light.
EXPLANATORY NOTE
In one example of molecular laser isotope separation, the product collectors serve to collect enriched uranium pentafluoride (UF₅) solid material. The product collectors may consist of filter, impact, or cyclone-type collectors, or combinations thereof, and must be corrosion resistant to the UF₅/ UF₆ environment.
5.7.7. UF₆/carrier gas compressors (molecular based methods)
Especially designed or prepared compressors for UF₆/carrier gas mixtures, designed for long term operation in a UF₆ environment. The components of these compressors that come into contact with process gas are made of or protected by materials resistant to corrosion by UF₆.
5.7.8. Rotary shaft seals (molecular based methods)
Especially designed or prepared rotary shaft seals, with seal feed and seal exhaust connections, for sealing the shaft connecting the compressor rotor with the driver motor so as to ensure a reliable seal against out-leakage of process gas or in-leakage of air or seal gas into the inner chamber of the compressor which is filled with a UF₆/carrier gas mixture.
5.7.9. Fluorination systems (molecular based methods)
Especially designed or prepared systems for fluorinating UF₅ (solid) to UF₆ (gas).
EXPLANATORY NOTE
These systems are designed to fluorinate the collected UF₅ powder to UF₆ for subsequent collection in product containers or for transfer as feed for additional enrichment. In one approach, the fluorination reaction may be accomplished within the isotope separation system to react and recover directly off the ‘product’ collectors. In another approach, the UF₅ powder may be removed/transferred from the ‘product’ collectors into a suitable reaction vessel (e.g., fluidised-bed reactor, screw reactor or flame tower) for fluorination. In both approaches, equipment for storage and transfer of fluorine (or other suitable fluorinating agents) and for collection and transfer of UF₆ are used.
5.7.10. UF₆ mass spectrometers/ion sources (molecular based methods)
Especially designed or prepared mass spectrometers capable of taking on-line samples from UF₆ gas streams and having all of the following:
1. Capable of measuring ions of 320 atomic mass units or greater and having a resolution of better than 1 part in 320;
2. Ion sources constructed of or protected by nickel, nickel-copper alloys with a nickel content of 60% by weight or more, or nickel-chrome alloys;
3. Electron bombardment ionisation sources; and
4. Having a collector system suitable for isotopic analysis.
5.7.11. Feed systems/product and tails withdrawal systems (molecular based methods)
Especially designed or prepared process systems or equipment for enrichment plants made of or protected by materials resistant to corrosion by UF₆, including:
(a) Feed autoclaves, ovens, or systems used for passing UF₆ to the enrichment process;
(b) Desublimers (or cold traps) used to remove UF₆ from the enrichment process for subsequent transfer upon heating;
(c) Solidification or liquefaction stations used to remove UF₆ from the enrichment process by compressing and converting UF₆ to a liquid or solid form;
(d) ‘Product’ or ‘tails’ stations used for transferring UF₆ into containers.
5.7.12. UF₆/carrier gas separation systems (molecular based methods)
Especially designed or prepared process systems for separating UF₆ from carrier gas.
EXPLANATORY NOTE
These systems may incorporate equipment such as:
(a) Cryogenic heat exchangers or cryoseparators capable of temperatures of 153 K (120°C) or less;
(b) Cryogenic refrigeration units capable of temperatures of 153 K (-120°C) or less;
(c) UF₆ cold traps capable of freezing out UF₆.
The carrier gas may be nitrogen, argon, or other gas.
5.7.13. Laser systems
Lasers or laser systems especially designed or prepared for the separation of uranium isotopes.
EXPLANATORY NOTE
The lasers and laser components of importance in laser-based enrichment processes include those identified in INFCIRC/254/Part 2 as amended. The laser system typically contains both optical and electronic components for the management of the laser beam (or beams) and the transmission to the isotope separation chamber. The laser system for atomic vapour based methods usually consists of tunable dye lasers pumped by another type of laser (e.g., copper vapour lasers or certain solid-state lasers). The laser system for molecular based methods may consist of carbon dioxide lasers or excimer lasers and a multi-pass optical cell. Lasers or laser systems for both methods require spectrum frequency stabilisation for operation over extended periods of time.
Present systems for enrichment processes using lasers fall into two categories: those in which the process medium is atomic uranium vapour and those in which the process medium is the vapour of a uranium compound, sometimes mixed with another gas or gases. Common nomenclature for such processes include:
- first category - atomic vapour laser isotope separation;
- second category - molecular laser isotope separation, including chemical reaction by isotope selective laser activation.
The systems, equipment and components for laser enrichment plants include:
(a) Devices to feed uranium-metal vapour (for selective photo-ionisation) or devices to feed the vapour of a uranium compound (for selective photo-dissociation or selective excitation/activation);
(b) Devices to collect enriched and depleted uranium metal as ‘product’ and ‘tails’ in the first category, and devices to collect enriched and depleted uranium compounds as ‘product’ and ‘tails’ in the second category;
(c) Process laser systems to selectively excite the uranium-235(²³⁵U)species;
(d) Feed preparation and product conversion equipment. The complexity of the spectroscopy of uranium atoms and compounds may require incorporation of any of a number of available laser and laser optics technologies.
EXPLANATORY NOTE
Many of the items listed in this section come into direct contact with uranium metal vapour or liquid or with process gas consisting of UF₆ or a mixture of UF₆ and other gases. All surfaces that come into direct contact with the uranium or UF₆ are wholly made of or protected by corrosion-resistant materials. For the purposes of the section relating to laser-based enrichment items, the materials resistant to corrosion by the vapour or liquid of uranium metal or uranium alloys include yttria-coated graphite and tantalum; and the materials resistant to corrosion by UF₆ include copper, copper alloys, stainless steel, aluminium, aluminium oxide, aluminium alloys, nickel or alloys containing 60% by weight or more nickel and fluorinated hydrocarbon polymers.
5.7.1. Uranium vaporisation systems (atomic vapour based methods)
Especially designed or prepared uranium metal vaporisation systems for use in laser enrichment.
EXPLANATORY NOTE
These systems may contain electron beam guns and are designed to achieve a delivered power (1 kW or greater) on the target sufficient to generate uranium metal vapour at a rate required for the laser enrichment function.
5.7.2. Liquid or vapour uranium metal handling systems and components (atomic vapour based methods)
Especially designed or prepared systems for handling molten uranium, molten uranium alloys or uranium metal vapour for use in laser enrichment, or especially designed or prepared components therefor.
EXPLANATORY NOTE
The liquid uranium metal handling systems may consist of crucibles and cooling equipment for the crucibles. The crucibles and other parts of this system that come into contact with molten uranium, molten uranium alloys or uranium metal vapour are made of or protected by materials of suitable corrosion and heat resistance. Suitable materials may include tantalum, yttria-coated graphite, graphite coated with other rare earth oxides (see INFCIRC/254/Part 2 as amended) or mixtures thereof.
5.7.3. Uranium metal ‘product’ and ‘tails’ collector assemblies (atomic vapour based methods)
Especially designed or prepared ‘product’ and ‘tails’ collector assemblies for collecting uranium metal in liquid or solid form.
EXPLANATORY NOTE
Components for these assemblies are made of or protected by materials resistant to the heat and corrosion of uranium metal vapour or liquid (such as yttria-coated graphite or tantalum) and may include pipes, valves, fittings, gutters, feed-throughs, heat exchangers and collector plates for magnetic, electrostatic or other separation methods.
5.7.4. Separator module housings (atomic vapour based methods)
Especially designed or prepared cylindrical or rectangular vessels for containing the uranium metal vapour source, the electron beam gun, and the ‘product’ and ‘tails’ collectors.
EXPLANATORY NOTE
These housings have multiplicity of ports for electrical and water feed-throughs, laser beam windows, vacuum pump connections and instrumentation diagnostics and monitoring. They have provisions for opening and closing to allow refurbishment of internal components.
5.7.5. Supersonic expansion nozzles (molecular based methods)
Especially designed or prepared supersonic expansion nozzles for cooling mixtures of UF₆ and carrier gas to 150 K (-123°C) or less and which are corrosion resistant to UF₆.
5.7.6. ‘Product’ or ‘tails’ collectors (molecular based methods)
Especially designed or prepared components or devices for collecting uranium product material or uranium tails material following illumination with laser light.
EXPLANATORY NOTE
In one example of molecular laser isotope separation, the product collectors serve to collect enriched uranium pentafluoride (UF₅) solid material. The product collectors may consist of filter, impact, or cyclone-type collectors, or combinations thereof, and must be corrosion resistant to the UF₅/ UF₆ environment.
5.7.7. UF₆/carrier gas compressors (molecular based methods)
Especially designed or prepared compressors for UF₆/carrier gas mixtures, designed for long term operation in a UF₆ environment. The components of these compressors that come into contact with process gas are made of or protected by materials resistant to corrosion by UF₆.
5.7.8. Rotary shaft seals (molecular based methods)
Especially designed or prepared rotary shaft seals, with seal feed and seal exhaust connections, for sealing the shaft connecting the compressor rotor with the driver motor so as to ensure a reliable seal against out-leakage of process gas or in-leakage of air or seal gas into the inner chamber of the compressor which is filled with a UF₆/carrier gas mixture.
5.7.9. Fluorination systems (molecular based methods)
Especially designed or prepared systems for fluorinating UF₅ (solid) to UF₆ (gas).
EXPLANATORY NOTE
These systems are designed to fluorinate the collected UF₅ powder to UF₆ for subsequent collection in product containers or for transfer as feed for additional enrichment. In one approach, the fluorination reaction may be accomplished within the isotope separation system to react and recover directly off the ‘product’ collectors. In another approach, the UF₅ powder may be removed/transferred from the ‘product’ collectors into a suitable reaction vessel (e.g., fluidised-bed reactor, screw reactor or flame tower) for fluorination. In both approaches, equipment for storage and transfer of fluorine (or other suitable fluorinating agents) and for collection and transfer of UF₆ are used.
5.7.10. UF₆ mass spectrometers/ion sources (molecular based methods)
Especially designed or prepared mass spectrometers capable of taking on-line samples from UF₆ gas streams and having all of the following:
1. Capable of measuring ions of 320 atomic mass units or greater and having a resolution of better than 1 part in 320;
2. Ion sources constructed of or protected by nickel, nickel-copper alloys with a nickel content of 60% by weight or more, or nickel-chrome alloys;
3. Electron bombardment ionisation sources; and
4. Having a collector system suitable for isotopic analysis.
5.7.11. Feed systems/product and tails withdrawal systems (molecular based methods)
Especially designed or prepared process systems or equipment for enrichment plants made of or protected by materials resistant to corrosion by UF₆, including:
(a) Feed autoclaves, ovens, or systems used for passing UF₆ to the enrichment process;
(b) Desublimers (or cold traps) used to remove UF₆ from the enrichment process for subsequent transfer upon heating;
(c) Solidification or liquefaction stations used to remove UF₆ from the enrichment process by compressing and converting UF₆ to a liquid or solid form;
(d) ‘Product’ or ‘tails’ stations used for transferring UF₆ into containers.
5.7.12. UF₆/carrier gas separation systems (molecular based methods)
Especially designed or prepared process systems for separating UF₆ from carrier gas.
EXPLANATORY NOTE
These systems may incorporate equipment such as:
(a) Cryogenic heat exchangers or cryoseparators capable of temperatures of 153 K (120°C) or less;
(b) Cryogenic refrigeration units capable of temperatures of 153 K (-120°C) or less;
(c) UF₆ cold traps capable of freezing out UF₆.
The carrier gas may be nitrogen, argon, or other gas.
5.7.13. Laser systems
Lasers or laser systems especially designed or prepared for the separation of uranium isotopes.
EXPLANATORY NOTE
The lasers and laser components of importance in laser-based enrichment processes include those identified in INFCIRC/254/Part 2 as amended. The laser system typically contains both optical and electronic components for the management of the laser beam (or beams) and the transmission to the isotope separation chamber. The laser system for atomic vapour based methods usually consists of tunable dye lasers pumped by another type of laser (e.g., copper vapour lasers or certain solid-state lasers). The laser system for molecular based methods may consist of carbon dioxide lasers or excimer lasers and a multi-pass optical cell. Lasers or laser systems for both methods require spectrum frequency stabilisation for operation over extended periods of time.