5.3 Especially Designed Or Prepared Assemblies and Components for use in Gaseous Diffusion Enrichment Plants

INTRODUCI'ORY NOTE                                                                           

In the gaseous diffusion method of uranium isotope separation, the main technological assembly is a special porous gaseous diffusion barrier, heat exchanger for cooling the gas (which is heated by the process of compression), seal valves and control valves, and pipelines. Inasmuch as gaseous diffusion technology uses uranium hexafiuoride (UF6), all equipment, pipeline and instrumentation surfaces (that come in contact with the gas) must be made of materials that remain stable in contact with UF6. A gaseous diffusion facility requires a number of these assemblies, so that quantities can provide an important indication of end use.

5.3.1 Gaseous Diffusion Barriers

(a)  Especially designed or prepared thin, porous filters, with a pore size of 100 - 1,000 (angstroms), a thickness of 5 mm (0.2 in) or less, and for tubular forms, a diameter of 25 mm (1 in) or less, made of metallic, polymer or ceramic materials resistant to corrosion by UF6, and

(b)  Especially prepared compounds or powders for the manufacture of such filters. Such compounds and powders include nickel or alloys containing 60 per cent of more nickel, aluminum oxide, or UF6-resistant fully fluorinated hydrocarbon polymers having a purity of 99.9 per cent or more, a particle size less than 10 microns, and a high degree of particle size uniformity, which are especially prepared for the manufacture of gaseous diffusion barriers.

5.3.2 Diffuser Housings

Especially designed of prepared hermetically sealed cylindrical vessels greater than 300 mm (12 in) in diameter and greater than 900 mm (35 in) in length, or rectangular vessels of comparable dimensions, which have an inlet connection and two outlet connections all of which are greater than 50 mm (2 in) in diameter, for containing the gaseous diffusion barrier, made of or lined with UF6-resistant materials and designed for horizontal or vertical installation.

5.3.3 Compressors and Gas Blowers

Especially designed or prepared axial, centrifugal, or positive displacement compressors. or gas blowers with a suction volume capacity of 1 m3/min or more of UF6, and with a discharge pressure of up to several hundred -kPa (100 psi), designed for long-term operation in the UF6 environment with or without an electrical motor of appropriate power, as well as separate assemblies of such compressors and gas blowers. These compressors and gas blowers have a pressure ratio between 2:1 and 6:1 and are made of, or lined with, materials resistant to UF6.

5.3.4 Rotary Shaft Seals

Especially designed or prepared vacuum seals, with seal feed and seal exhaust connections, for sealing   the shall connecting the compressor or the gas blower rotor with the driver motor so as to ensure a reliable seal against in-leaking of air into the inner chamber of the compressor or gas blower which is filled with UF6. Such seals are normally designed for a buffer gas in-leakage rate of less than 1000 cm3/min (60 in3/min).

5.3.5 Heat Exchangers for Cooling UF6

Especially designed or prepared heat exchangers made of or lined with UF6-resistant materials (except stainless steel) or with copper or any combination of those metals, and intended for a lealmge pressure change rate of less than 10 pa (0.0015 psi) per hour under a pressure difference of 100 kPa (15 psi).

5.4 Especially Designed Or Prepared Auxiliary Systems,Equipment, and Components for use in Gaseous Diffusion Enrichment

INTRODUCTORY NOTE

The auxiliary systems, equipment and components for gaseous diffusion enrichment plants are the systems of plant needed to feed UF6 to the gaseous diffusion assembly, to link the individual assemblies to each other to form cascades (or stages) to allow for progressively higher enrichments and to extract the "product" and "tails" UF6 from the diffusion cascades. Because of the high inertial properties of diffusion cascades, any interruption in their operation, and especially their shut­down, leads to serious consequences. Therefore, a strict and constant maintenance of vacuum in all technological systems, automatic protection from accidents, and precise automated regulation of the gas flow is of importance in a gaseous diffusion plant. All this leads to a need to equip the plant with a large number of special measuring, regulating and controlling systems.

 Normally UF6 is evaporated from cylinders placed within autoclaves and is distributed in gaseous form to the entry point by way of cascade header pipework. The "product" and "tails" UF6 gaseous streams flowing from exit points ate passed by way of cascade header pipework to either cold traps or to compression stations where the UF6 gas is liquefied prior to onward transfer into suitable containers for transportation or storage. Because a gaseous diffusion enrichment plant consists of a large number of gaseous diffusion assemblies arranged in cascades, there are many kilometers of cascade header pipework, incorporating thousands of welds with substantial amounts of repetition of layout. The equipment, components and piping systems are fabricated to very high vacuum and cleanliness standards.

5.4.1 Feed System/Product and Tails Withdrawal Systems

Especially designed or prepared process systems, capable of operating at pressures of 300 kPa (45 psi) or less, including:  

Feed autoclaves (or systems), used for passing UF6 to the gaseous diffusion cascades; 

Desublimers (or cold traps) used to remove UF6 from diffusion cascades; 

Liquefaction stations where UF6 gas from the cascade is compressed and cooled to form liquid UF6; "Product" or "tails" stations used for transferring UF6 into containers.

5.4.2 Header Piping Systems

Especially designed or prepared piping systems and header systems for handling UF6 within the gaseous diffusion cascades. This piping network is normally of the "double" header system with each cell connected to each of the headers.

5.4.3 Vacuum Systems

(a) Especially designed or prepared large vacuum manifolds, vacuum headers and vacuum pumps having a suction capacity of 5 m3/nfin (175 fQ/min) or more.

(b) Vacuum pumps especially designed for service in UF6-bearing atmospheres made of, or lined with, aluminum, nickel, or alloys bearing more than 60% nickel. These pumps may be either rotary or positive, may have displacement and fluorocarbon seals, and may have special working fluids present.

5.4.4 Special Shut-off and Control Valves

Especially designed or prepared manual or automated shut-off and control bellows valves made of UFO-resistant materials with a diameter of 40 to 1500 nun (1.5 to 59 in) for installation in main and auxiliary systems of gaseous diffusion enrichment plants.

5.4.5 UF6 Mass Spectrometers/Ion Sources

Especially designed or prepared magnetic or quadrupole mass spectrometers capable of taking "on­line" samples of feed, product or tails, from UF6 gas streams and having all of the following characteristics:

 1.    Unit resolution for atomic mass unit greater than 320;

 2.    Ion sources constructed of or lined with nichrome or monel or nickel plated;

 3.    Electron bombardment ionization sources;

 4.    Collector system suitable for isotopic analysis.

 EXPLANATORY NOTE

 The items listed above either come into direct contact with the UF6 process gas or directly control the flow within the cascade. All surfaces which come into contact with the process gas are wholly made of, or lined with, UF6-resistant materials. For the proposes of the sections relating to gaseous diffusion items the materials resistant to corrosion by UF6 include stainless steel, aluminum, aluminum alloys, aluminum oxide, nickel or alloys containing 60% or more nickel and UF6-resistant fully fluorinated hydrocarbon polymers.

5.5 Especially Designed Or Prepared Systems, Equipment, and Components For Use in Aerodynamic Enrichment Plants

INTRODUCTORY NOTE

In aerodynamic enrichment processes, a mixture of gaseous UF6 and light gas (hydrogen or helium) is compressed and then passed through separating elements wherein isotopic separation is accomplished by the generation of high centrifugal forms over a curved-all geometry. Two processes of this type have been successfully developed: the separation nozzle process and the vortex tube process. For both processes the main components of a separation stage include cylindrical vessels housing the special separation elements (nozzles or vortex tubes), gas compressors and heat exchangers to remove the heat of compression. An aerodynamic plant requires a number of these stages, so that quantities can provide and important indication of end use. Since aerodynamic processes use UF6, all equipment, pipeline and instrumentation surfaces (that come in contact with the gas) must be made of materials that remain stable in contact with UF6.

EXPLANATORY NOTE

The items listed in this section either come into direct contact with the UF6 process gas or directly control the flow within the cascade. All surfaces which come into contact with the process gas are wholly made of or protected by UF6-resistant materials. For the purposes of the section relating to aerodynamic enrichment items, the materials resistant to corrosion by UF6 include copper, stainless steel, aluminum alloys, nickel or alloys containing 60% or more nickel and UF6-resistant fully fluorinated hydrocarbon polymers.

5.5.1 Separation Nozzles

Especially designed or prepared separation nozzles and assemblies thereof. The separation nozzles consist of slit-shaped, curved channels having a radius of curvature less than 1 mm (typically 0:1 to 0.05 ram), resistant to corrosion by UF6 and having a knife-edge within the nozzle that separates the as flowing through the nozzle into two fractions.

5.5.2 Vortex Separation Units

Especially designed or prepared vortex tubes and assemblies thereof. The vortex tubes are cylindrical r tapered, made of or protected by materials resistant to corrosion by UF6, having a diameter of between 0.5 cm and 4 cm, a length to diameter ratio of 20:1 or less and with one or more tangential inlets. The tubes may be equipped with nozzle-type appendages at either or both ends.

EXPLANATORY NOTE

The feed gas enters the vortex tube tangentially at one end or through swirl vanes or at numerous tangential positions along the periphery of the tube.

5.5.3. Compressors and Gas Blowers

Especially designed or prepared axial, centrifugal or positive displacement compressors or gas blowers made of or protected by materials resistant to corrosion by UF6 and with a suction volume capacity of 2 m3/min or more of UF6/carrier gas (hydrogen or helium) mixture.

EXPLANATORY NOTE

These compressors and gas blowers typically have a pressure ratio between 1.2:1 and 6:1.

5.5.4. Rotary Shaft Seals

Especially designed or prepared rotary shaft seals, with seal feed and seal exhaust connections, for sealing the shaft connecting the compressor rotor or the gas blower 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 or gas blower which is filled with a UF6/carrier gas mixture.

5.5.5. Heat Exchangers For Gas Cooling

Especially designed or prepared heat exchangers made of or protected by materials resistant to
corrosion by UF6.

5.5.6. Separation Element Housings

Especially designed or prepared separation element housings, made of or protected by materials resistant to corrosion by UF6, for containing vortex tubes or separation nozzles.

EXPLANATORY NOTE

These housings may be cylindrical vessels greater than 300 mm in diameter and greater than 900 mm in length, or may be rectangular vessels of comparable dimensions, and may be designed for horizontal or vertical installation.

5.5.7. Feed Systems/Product and Tails Withdrawal Systems

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;

5.5.8. Header Piping Systems

Especially designed or prepared header piping systems, made of or protected by materials resistant to corrosion by UF6, for handling UF6 within the aerodynamic cascades. This piping net work is normally of the 'double' header design with each stage or group of stages connected to each of the headers.

5.5.9 Vacuum Systems And Pumps

(a) Especially designed or prepared vacuum systems having a suction capacity of 5 m3/min or more, consisting of vacuum manifolds, vacuum headers and vacuum pumps, and designed for service in UFo-bearing atmospheres,

(b) Vacuum pumps especially designed or prepared for service in UF6-beating atmospheres and made of or protected by materials resistant to corrosion by UF6. These pumps may use fluorocarbon seals and special working fluids.

5.5.10. Special Shut-off And Control Valves

Especially designed or prepared manual or automated shut-off control bellows valves made of or
protected by materials resistant to corrosion by UF6 with a diameter of 40 to 1500 mm for installation in main and auxiliary systems of aerodynamic enrichment plants.

5.5.11. UF6 Mass Spectrometers/Ion Sources

Especially designed or prepared magnetic or quadmpole mass spectrometers capable of taking 'on-line' samples of feed, 'product' or 'tails', from UF6 gas streams and having all of the following
characteristics:

5.5.12. UF6/Carrier Gas Separation Systems

Especially designed or prepared process systems for separating UF6 from carrier gas (hydrogen or helium).

 EXPLANATORY NOTE

 These systems am designed to reduce the UF6 content in the carrier gas to 1 ppm or less and may incorporate equipment such as:

 (a)  Cryogenic heat exchangers and cryoseparators capable of temperatures of-120 °C or less, or

 (b)  Cryogenic refrigeration units capable of temperatures of-120 °C or less, or

 (c)  Separation nozzle or vortex tube units for the separation ofUF6 from carrier gas, or

 (d)  UF6 cold traps capable of temperatures of-20 °C or less.

5.6 Especially Designed Or Prepared Systems, Equipment, and Components For Use in Chemical Exchange Enrichment Plants

INTRODUCTORY NOTE

The slight difference in mass between the isotopes of uranium causes small changes in chemical reaction equilibria that can be used as a basis for separation of the isotopes. Two processes have been successfully developed: liquid-liquid chemical exchange and solid-liquid exchange.

In the liquid-liquid exchange process, immiscible liquid phases (aqueous and organic) are counter currently contacted to give the cascading effect of thousands of separation stages. The aqueous phase consists of uranium chloride in hydrochloric acid solution; the organic phase consists of an extractant containing uranium chloride in an organic solvent. The contactors employed in the separation cascade can be liquid-liquid exchange columns (such as pulsed columns with sieve plates) or liquid centrifugal contactors. Chemical conversions (oxidation and reduction) are required at both ends of the separation cascade in order to provide for the reflux requirements at each end. A major design concern is to avoid contamination of the process streams with certain metal ions. Plastic, plastic-lined (including use of fluorocarbon polymers) and/or glass-lined columns and piping are therefore used.

 In the solid-liquid ion-exchange process, enrichment is accomplished by uranium adsorption/desorption on a special, very fast-acting, ion-exchange resin or adsorbent. A solution of uranium in hydrochloric acid and other chemical agents is passed through cylindrical enrichment columns containing packed beds of the adsorbent. For a continuous process, a reflux system is necessary to release the uranium from the adsorbent back into the liquid flow so that 'product' and 'tails' can be collected. This is accomplished with the use of suitable reduction/oxidation chemical agents that are fully regenerated in separate external circuits and that may be partially regenerated within the isotopic separation columns themselves. The presence of hot concentrated hydrochloric acid solutions in the process requires that the equipment be made of or protected by special corrosion-resistant materials.

5.6.1. Liquid-Liquid Exhange Columns (Chemical Exchange)

Countercurrent liquid-liquid exchange columns having mechanical power input (i.e., pulsed columns with sieve plates, reciprocating plate columns, and columns with internal turbine mixers), especially designed or prepared for uranium enrichment using the chemical exchange process. For corrosion resistance to concentrated hydrochloric acid solutions, these columns and their internals are made of or protected by suitable plastic materials (such as fluorocarbon polymers) or glass. The stage residence time of the columns is designed to be short (30 seconds or less).

5.6.2. Liquid-Liquid Centrifugal Contactors (Chemical Exchange)

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Liquid-liquid centrifugal contactors especially designed or prepared for uranium enrichment using the chemical exchange process. Such contactors use rotation to achieve dispersion of the organic and aqueous streams and then centrifugal force to separate the phases. For corrosion resistance to concentrated hydrochloric acid solutions, the contactors are made of or are lined with suitable plastic materials 9such as fluorocarbon polymers) or are lined with glass. The stage residence time of the centrifugal contactors is designed to be short (30 seconds or less).

5.6.3 Uranium Reduction Systems and Equipment (Chemical Exchange)

(a) Especially designed or prepared electrochemical reduction cells to reduce uranium from one valence state to another for uranium enrichment using the chemical exchange process. The cell materials in contact with process solutions must be corrosion resistant to concentrated hydrochloric acid solutions.

EXPLANATORY NOTE

The cell cathodic compartment must be designed to prevent re-oxidation of uranium to its higher valence state. To keep the uranium in the cathodic compartment, the cell may have an impervious diaphragm membrane constructed of special cation exchange material. The cathode consists of a suitable solid conductor such as graphite.

(b)     Especially designed or prepared systems at the product end of the cascade for taking the U*4 out of the organic stream, adjusting the acid concentration and feeding to the electrochemical reduction cells.

EXPLANATORY NOTE

These systems consist of solvent extraction equipment for stripping the U+4 from the organic stream into an aqueous solution, evaporation and/or other equipment to accomplish solution pH adjustment and control, and pumps or other transfer devices for feeding to the electrochemical reduction cells. A major design concern is to avoid contamination of the aqueous stream with certain metal ions. Consequently, for those parts in contact with the process stream, the system is constructed of equipment made of or protected by suitable materials (such as glass, fluorocarbon polymers, polyphenyl sulfate, polyether sulfone, and resin-impregnated graphite).

5.6.4.  Feed Preparation Systems (Chemical Exchange)

Especially designed or prepared systems for producing high-purity uranium chloride feed solutions for chemical exchange uranium isotope separation plants.

EXPLANATORY NOTE

These systems consist of dissolution, solvent extraction and/or ion exchange equipment for purification and electrolytic cells for reducing the uranium U+6 or U+4 to U+3. These systems produce uranium chloride solutions having only a few parts per million of metallic impurities such as chromium, iron, vanadium, molybdenum and other bivalent or higher multi-valent cations. Materials of construction for portions of the system processing high-purity U+3 include glass, fluorocarbon polymers, polyphenyl sulfate or polyether sulfone plastic-lined and rosin-impregnated graphite.

5.6.5. Uranium oxidation systems (Chemical Exchange)

Especially designed or prepared systems for oxidation of U+3 to L?4 for return to the uranium isotope separation cascade in the chemical exchange enrichment process.

EXPLANATORY NOTE

These systems may incorporate equipment such as:

(a) Equipment for contacting chlorine and oxygen with the aqueous effluent from the isotope separation equipment and extracting the resultant U+4 into the stripped organic stream returning from the product end of the cascade.

(b) Equipment that separates water from hydrochloric acid so that the water and the concentrated hydrochloric acid may be reintroduced to the process at the proper locations.

5.6.6. Fast-Reacting Ion Exchange Resins/Adsorbents (Ion Exchange)

Fast-reacting ion-exchange resins or adsorbents especially designed or prepared for uranium enrichment using the ion exchange process, including porous macroreticular resins, and/or pellicular structures in which the active chemical exchange groups are limited to a coating on the surface of an inactive porous support structure, and other composite structures in any suitable form including particles or fibers. These ion exchange resins/adsorbents have diameters of 0.2 mm or less and must be chemically resistant to concentrated hydrochloric acid solutions as well as physically strong enough so as not to degrade in the exchange columns. The resins/adsorbents are especially designed to achieve very fast uranium isotope exchange kinetics (exchange rate half-time of less than 10 seconds) and are capable of operating at a temperature in the range of 100 °C to 200 °C.

5.6.7. Ion Exchange Columns (Ion Exchange)

Cylindrical columns greater than 1000 mm in diameter for containing and supporting packed beds of ion exchange resin/adsorbent, especially designed or prepared for uranium enrichment using the ion exchange process. These columns are made of or protected by materials (such as titanium or fluorocarbon plastics) resistant to corrosion by concentrated hydrochloric acid solutions and are capable of operating at a temperature in the range of 100 °C to 200 °C and pressures above 0.7 MPa (102 psi).

5.6.8.  Ion Exchange Reflux Systems (Ion Exchange)

(a)  Especially designed or prepared chemical or electrochemical reduction systems for regeneration of the chemical reducing agent(s) used in ion exchange uranium enrichment cascades.

(b) Especially designed or prepared chemical or electrochemical oxidation systems for regeneration of the chemical oxidizing agent(s) used in ion exchange uranium enrichment cascades.

EXPLANATORY NOTE

The ion exchange enrichment process may use, for example, trivalent titanium (TI+3) as a reducing cation in which case the reduction system would regenerate Ti+3 by reducing Ti+4.

The process may use, for example, trivalent iron (Fe+3) as an oxidant in which case the oxidation system would regenerate Fe+3 by oxidizing Fe+2.

5.7. Especially Designed Or Prepared Systems, Equipment and Components for Use in Laser-Based Enrichment Plants.

INTRODUCTORY NOTE

 Present systems for enrichment processes using lasers fall into two categories: those in which the process medium is atomic uranium vapor and those in which the process medium is the vapor of a uranium compound. Common nomenclature for such processes include: first category - atomic vapor laser isotope separation (AVLIS or SILVA); second category - molecular laser isotope separation (MLIS or MOOLIS) and chemical reaction by isotope selective laser activation (CRISLA). The systems, equipment and components for laser enrichment plants embrace: (a) devices to feed uranium-metal vapor (for selective photo-ionization) or devices to feed the vapor of a uranium compound (for photo-dissociation or chemical activation); (b) devices to collect enriched and depleted uranium metal as 'product' and 'tails' in the first category, and devices to collect dissociated or reacted compounds as 'product' and unaffected material as 'tails' in the second category; (c) process laser systems to selectively excite the uranium-235 species; and (d) feed preparation and product conversion equipment. The complexity of uranium atoms and compounds may require incorporation of any of a number of available laser technologies.

EXPLANATORY NOTE

Many of the items in this section come into direct contact with uranium metal vapor or liquid or with process gas consisting of UF6 or a mixture of UF6 and other gases. All surfaces that come into contact with the uranium of 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 vapor or liquid of uranium metal or uranium alloys include ytaia-coated graphite and tantalum; and the materials resistant to corrosion by UF6 include copper, stainless steel, aluminum, aluminum alloys, nickel or alloys containing 60 % or more nickel and UF6-resistant fully fluorinated hydrocarbon polymers.

5.7.1. Uranium Vaporization Systems (AVLIS)

Especially designed or prepared uranium vaporization systems which contain high-power strip or scanning electron beam guns with a delivered power on the target of more than 2.5 kW/cm.

5.7.2. Liquid Uranium Metal Handling Systems (AVLIS)

Especially designed or prepared liquid metal handling systems for molten uranium or uranium alloys, consisting of crucibles and cooling equipment for the crucibles.

EXPLANATORY NOTE

The crucibles and other parts of this systems that come into contact with molten uranium or uranium alloys are made of or protected by materials of suitable corrosion and heat resistance. Suitable materials include tantalum, yttra-coated graphite, graphite coated with other rare earth oxides (see INFCIRC/254/Rev. l/part 2, item 2.7) or mixtures thereof.

5.7.3. Uranium Metal 'Product' and 'Tails' Collector Assemblies (AVLIS)

Especially designed or prepared 'product' and 'tails' collector assemblies for 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 vapor 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 (AVLIS)

Especially designed or prepared cylindrical or rectangular vessels for containing the uranium metal vapor 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 closure to allow refurbishment of internal components.

5.7.5. Supersonic Expansion Nozzles (MLIS)

Especially designed or prepared supersonic expansion nozzles for cooling mixtures of UF6 and carrier gas to 150 K or less and which are corrosion resistant to UF6.

5.7.6.  Uranium Pentafluoride Product Collectors (MLIS)

Especially designed or prepared uranium pentafluoride (UFs) solid product collectors consisting of filter, impact, or cyclone-type collectors, or combinations thereof, and which are corrosion resistant to the UFs/UF6 environment.

5.7.7.  UF6/Carrier Gas Compressors (MLIS)

Especially designed or prepared compressors for UFdcarrier 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 (MLIS)

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 UF6carrier gas mixture.

5.7.9. Fluorination Systems (MLIS)

Especially designed or prepared systems for fluorinating UF5 (solid) to UF6 (gas).

EXPLANATORY NOTE

These systems am designed to fluorinate the collected UF5 powder to UF6 for subsequent collection in product containers or for transfer as feed to MLIS units 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., fluidized-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 (MLIS)

Especially designed or prepared magnetic or quadmpole mass spectrometers capable of taking 'on-
                line' samples of feed, 'product' or 'tails', from UF6 gas streams and having all of the following
                characteristics:

1. Unit resolution for mass greater than 320

2. Ion sources constructed of or lined with nichrome or monel or nickel plated;

3. Electron bombardment ionization sources;

4. Collector system suitable for isotopic analysis.

5.7.11. Feed Systems/Product and Tails Withdrawal Systems (MLIS)

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 (MLIS)

Especially designed or prepared process systems for separating UF6 from carder gas. The carrier
gas may be nitrogen, argon, or other gas.

EXPLANATORY NOTE

These systems may incorporate equipment such as:

(a) Cryogenic heat exchangers or cryosepamtors capable of temperatures of-120 °C or less, or 

(b) Cryogenic refrigeration units capable of temperatures of-120 °C or less, or

(c) UF6 c01d traps capable of temperatures of-20 °C or less.

5.7.13.  Laser Systems (AVLIS, MLIS, and CRISLA)

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 item 3.6 or INFCIRC/254/Rev. 1/Part 2. The laser system for the AVLIS process usually consists of two lasers: a copper vapor laser and a dye laser. The laser system for MLIS usually consists of a CO2 or excimer laser and a multi-pass optical cell with revolving mirrors at both ends. Lasers or laser systems for both processes require a spectrum frequency stabilizer for operation over extended periods of time.

5.8.  Especially Designated Or Prepared Systems, Equipment and Components For Use in Plasma Separation Enrichment Plants

INTRODUCTORY NOTE

In the plasma separation process, a plasma of uranium ions passes through an electric field tuned to the 235U. The plasma, which is made by ionizing uranium vapor, is contained in a vacuum chamber with a high-strength magnetic field produced by a superconducting magnet. The main technological systems of the process include the uranium plasma generation system, the separator module with superconducting magnet (see item 3.10 of INFClRC/254/Rev. 1/Part 2), and metal removal systems for the collection of 'product' and 'tails'.

5.8.1.  Microwave Power Sources and Antennae

Especially designed or prepared microwave power sources and antennae for producing or accelerating ions and having the following characteristics: greater than 30 GHz frequency and greater than 50 kW mean power output for ion production.

5.8.2.  Ion Excitation Coils

Especially designed or prepared radio frequency ion excitation coils for frequencies of more than 100 kHz and capable of handling more than 40 kW mean power.

5.8.3.  Uranium Plasma Generation Systems

Especially designed or prepared systems for the generation of uranium plasma, which may contain high-power strip or scanning electron beam guns with a delivered power on the target of more than 2.5 kW/cm.

5.8.4.  Liquid Uranium Metal Handling Systems

Especially designed or prepared liquid metal handling systems for molten uranium or uranium alloys, consisting of crucibles and cooling equipment for the crucibles.

 EXPLANATORY NOTE

 The crucibles and other parts of this system that come into contact with molten uranium or uranium alloys are made of or protected by materials of suitable corrosion and heat resistance. Suitable materials include tantalum, yttria-coated graphite, graphite coated with other rare earth oxides (see INFCIRC/254/Rev. 1/Part 2, item 2.7) or mixtures thereof.

5.8.5.  Uranium Metal 'Product' and "Tails' Collector Assemblies

Especially designed or prepared 'product' and 'tails' collector assemblies for uranium metal in solid form. These collector assemblies are made of or protected by materials resistant to the heat and corrosion of uranium metal vapor, such as yttria-coated graphite or tantalum.

5.8.6.  Separator Module Housings

Cylindrical vessels especially designed or prepared for use in plasma separation enrichment plants for containing the uranium plasma source, radio-frequency drive coil and the 'product' and 'tails' collectors.

EXPLANATORY NOTE

These housings have a multiplicity of ports for electrical feed-throughs, diffusion pump connections and instrumentation diagnostics and monitoring. They have provisions for opening and closure to allow for refurbishment of internal components and are constructed of a suitable non-magnetic material such as stainless steel.

5.9.  Especially Designated Or Prepared Systems, Equipment And Componenets For Use In Electromagnetic Enrichment Plants

INTRODUCTORY NOTE

In the electromagnetic process, uranium metal ions produced by ionization of a salt feed material (typically UCI4) are accelerated and passed through a magnetic field that has the effect of causing the ions of different isotopes to follow different paths. The major components of an electromagnetic isotope separator include: a magnetic field for ion-beam diversion/separation of the isotopes, an ion source with its acceleration system, and a collection system for the separated ions. Auxiliary systems for the process include the magnet power supply system, the ion source high-voltage power supply system, the vacuum system, and extensive chemical handling systems for recovery of product and cleaning/recycling of components.

5.9.1. Electromagnetic Isotope Separators

Electromagnetic isotope separators especially designed or prepared for the separation of uranium isotopes, and equipment and components therefor, including:

(a) Ion sources

Especially designed or prepared single or multiple uranium ion sources consisting of a vapor source, ionizer, and beam accelerator, constructed of suitable materials such 'as graphite, stainless steel, or copper, and capable of providing a total ion beam current of 50 mA or greater.

(b) ion collectors

Collector plates consisting of two or more slits and pockets especially designed or prepared for collection of enriched and depleted uranium ion beams and constructed of suitable materials such as graphite or stainless steel.

(c)  Vacuum housings

Especially designed or prepared vacuum housings for uranium electromagnetic separators, constructed of suitable non-magnetic materials such as stainless steel and designed for operation at pressures of 0.1 Pa or lower.

EXPLANATORY NOTE ·

The housings are specially designed to contain the ion sources, collector plates and water-cooled liners and have provision for diffusion pump connections and opening and closure for removal and  installation of these components.

(d)  Magnet pole pieces

Especially designed or prepared magnet pole pieces having a diameter greater than 2 m used to maintain a constant magnetic field within an electromagnetic isotope separator and to transfer the magnetic field between adjoining separators.

5.9.2.  High Voltage Power Supplies

Especially designed or prepared high-voltage power supplies for ion sources, having all of the following characteristics: capable of continuous operation, output voltage of 20,000 V or greater, output current of 1 A or greater, and voltage regulation of better than 0.01% over a time period of 8 hours.

5.9.3.  Magnet Power Supplies

Especially designed or prepared high-power, direct current magnet power supplies having all of the following characteristics: capable of continuously producing a current output of 500 A or greater at a voltage of 100 V or greater and with a current or voltage regulation better than 0.01% over a period of 8 hours.