Items of equipment that are considered to fall within the meaning of the phrase “equipment,
other than analytical instruments, especially designed or prepared“ for the separation
of isotopes of uranium include:
-
5.1.
Gas centrifuges and assemblies and components especially designed or prepared for
use in gas centrifuges
INTRODUCTORY NOTE
The gas centrifuge normally consists of a thin-walled cylinder(s) of between 75 mm
(3 in) and 400 mm (16 in) diameter contained in a vacuum environment and spun at high
peripheral speed of the order of 300 m/s or more with its central axis vertical. In
order to achieve high speed the materials of construction for the rotating components
have to be of a high strength to density ratio and the rotor assembly, and hence its
individual components, have to be manufactured to very close tolerances in order to
minimize the unbalance. In contrast to other centrifuges, the gas centrifuge for uranium
enrichment is characterized by having within the rotor chamber a rotating disc-shaped
baffle(s) and a stationary tube arrangement for feeding and extracting the UF6 gas and featuring at least 3 separate channels, of which 2 are connected to scoops
extending from the rotor axis towards the periphery of the rotor chamber. Also contained
within the vacuum environment are a number of critical items which do not rotate and
which although they are especially designed are not difficult to fabricate nor are
they fabricated out of unique materials. A centrifuge facility however requires a
large number of these components, so that quantities can provide an important indication
of end use.
-
5.2.
Especially designed or prepared auxiliary systems, equipment and components for gas
centrifuge enrichment plants
INTRODUCTORY NOTE
The auxiliary systems, equipment and components for a gas centrifuge enrichment plant
are the systems of plant needed to feed UF6 to the centrifuges, to link the individual centrifuges to each other to form cascades
(or stages) to allow for progressively higher enrichments and to extract the “product”
and “tails” UF6 from the centrifuges, together with the equipment required to drive the centrifuges
or to control the plant.
Normally UF6 is evaporated from the solid using heated autoclaves and is distributed in gaseous
form to the centrifuges by way of cascade header pipework. The “product” and “tails”
UF6 gaseous streams flowing from the centrifuges are also passed by way of cascade header
pipework to cold traps (operating at about 203 K (-70°C)) where they are condensed
prior to onward transfer into suitable containers for transportation or storage. Because
an enrichment plant consists of many thousands of centrifuges arranged in cascades
there are many kilometers of cascade header pipework, incorporating thousands of welds
with a substantial amount of repetition of layout. The equipment, components and piping
systems are fabricated to very high vacuum and cleanliness standards.
-
5.2.1.
Feed systems/product and tails withdrawal systems
Especially designed or prepared process systems including:
Feed autoclaves (or stations), used for passing UF6 to the centrifuge cascades at up to 100 kPa (15 psi) and at a rate of 1 kg/h or more;
Desublimers (or cold traps) used to remove UF6 from the cascades at up to 3 kPa (0.5 psi) pressure. The desublimers are capable
of being chilled to 203 K (-70 °C) and heated to 343 K (70 °C);
“Product” and “Tails” stations used for trapping UF6 into containers.
This plant, equipment and pipework is wholly made of or lined with UF6-resistant materials (see EXPLANATORY NOTE to this section) and is fabricated to very
high vacuum and cleanliness standards.
-
5.2.2.
Machine header piping systems
Especially designed or prepared piping systems and header systems for handling UF6 within the centrifuge cascades. The piping network is normally of the “triple” header
system with each centrifuge connected to each of the headers. There is thus a substantial
amount of repetition in its form. It is wholly made of UF6-resistant materials (see EXPLANATORY NOTE to this section) and is fabricated to very
high vacuum and cleanliness standards.
-
5.2.3.
UF6 mass spectrometers/ion sources
Especially designed or prepared magnetic or quadrupole 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 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) Having a collector system suitable for isotopic analysis.
-
5.2.4.
Frequency changers
Frequency changers (also known as converters or invertors) especially designed or
prepared to supply motor stators as defined under 5.1.2.(d), or parts, components
and sub-assemblies of such frequency changers having all of the following characteristics:
-
1. A multiphase output of 600 to 2000 Hz;
-
2. High stability (with frequency control better than 0.1%);
-
3. Low harmonic distortion (less than 2%); and
-
4. An efficiency of greater than 80%.
EXPLANATORY NOTE
The items listed above either come into direct contact with the UF6 process gas or directly control the centrifuges and the passage of the gas from centrifuge
to centrifuge and cascade to cascade.
Materials resistant to corrosion by UF6 include stainless steel, aluminium, aluminium alloys, nickel or alloys containing
60% or more nickel.
-
5.3.
Especially designed or prepared assemblies and components for use in gaseous diffusion
enrichment
INTRODUCTORY 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 hexafluoride
(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 Å
(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 or more nickel,
aluminium 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 or 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 shaft 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 leakage 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 shut-down, 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 are 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 systems/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/min (175 ft3/min) or more.
-
b) Vacuum pumps especially designed for service in UF6-bearing atmospheres made of, or lined with, aluminium, 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 UF6-resistant materials with a diameter of 40 to 1500 mm (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 “on-line“ 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 purposes of the sections relating to gaseous diffusion
items the materials resistant to corrosion by UF6 include stainless steel, aluminium, aluminium alloys, aluminium 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
forces over a curved-wall 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 an 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, aluminium, aluminium 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 mm), resistant to corrosion by UF6 and having a knife-edge within the nozzle that separates the gas flowing through
the nozzle into two fractions.
-
5.5.2.
Vortex tubes
Especially designed or prepared vortex tubes and assemblies thereof. The vortex tubes
are cylindrical or 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;
-
d) “Product” or “tails” stations used for transferring UF6 into containers.
-
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 network 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 UF6-bearing atmospheres,
-
b) Vacuum pumps especially designed or prepared for service in UF6-bearing 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 and 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 quadrupole 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.
-
5.5.12.
UF6/carrier gas separation systems
Especially designed or prepared process systems for separating UF6 from carrier gas (hydrogen or helium).
EXPLANATORY NOTE
These systems are 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 of UF6 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 or ion 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 ion exchange.
In the liquid-liquid chemical exchange process, immiscible liquid phases (aqueous
and organic) are countercurrently 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 exchange 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)
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 (such 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 U4+ 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 U4+ 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 U6+ or U4+ to U3+. 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 U3+ include glass, fluorocarbon polymers, polyphenyl sulfate or polyether sulfone plastic-lined
and resin-impregnated graphite.
-
5.6.5.
Uranium oxidation systems (Chemical exchange)
Especially designed or prepared systems for oxidation of U3+ to U4+ 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 U4+ 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 psia).
-
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 (Ti3+) as a reducing cation in which case the reduction system would regenerate Ti3+ by reducing Ti4+.
The process may use, for example, trivalent iron (Fe3+) as an oxidant in which case the oxidation system would regenerate Fe3+ by oxidizing Fe2+.
-
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 MOLIS) 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 the spectroscopy of uranium atoms and compounds may require incorporation
of any of a number of available laser technologies.
EXPLANATORY NOTE
Many of the items listed 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 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 vapor or liquid of uranium metal or uranium alloys include yttria-coated
graphite and tantalum; and the materials resistant to corrosion by UF6 include copper, stainless steel, aluminium, aluminium 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 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 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 (UF5) solid product collectors consisting of filter, impact, or cyclone-type collectors,
or combinations thereof, and which are corrosion resistant to the UF5/UF6 environment.
-
5.7.7.
UF6/carrier gas compressors (MLIS)
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 (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
UF6/carrier gas mixture.
-
5.7.9.
Fluorination systems (MLIS)
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 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 quadrupole 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 carrier 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 cryoseparators capable of temperatures of -120 °C or
less, or
-
b) Cryogenic refrigeration units capable of temperatures of -120 °C or less, or
-
c) UF6 cold 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 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 designed 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 U-235 ion resonance frequency so that they preferentially absorb
energy and increase the diameter of their corkscrew-like orbits. Ions with a large-diameter
path are trapped to produce a product enriched in U-235. 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 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 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 designed or prepared systems, equipment and components for use in electromagnetic
enrichment plants
INTRODUCTORY NOTE
In the electromagnetic process, uranium metal ions produced by ionization of a salt
feed material (typically UCl4) 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 reinstallation 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.
