Appendix E to Part 110 - Illustrative List of Chemical Exchange or Ion Exchange Enrichment Plant Equipment and Components Under NRC Export Licensing Authority
10:2.0.1.1.20.11.139.7.26 : Appendix E
Appendix E to Part 110 - Illustrative List of Chemical Exchange or
Ion Exchange Enrichment Plant Equipment and Components Under NRC
Export Licensing Authority 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.
A. 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.
(1) Liquid-liquid exchange columns.
Countercurrent liquid-liquid exchange columns having mechanical
power input 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 normally made of, or protected by, suitable plastic
materials (such as fluorinated hydrocarbon polymers) or glass. The
stage residence time of the columns is normally designed to be 30
seconds or less.
(2) Liquid-liquid centrifugal contactors.
Especially designed or prepared for uranium enrichment using the
chemical exchange process. These 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
normally made of, or protected by, suitable plastic materials (such
as fluorinated hydrocarbon polymers) or glass. The stage residence
time of the centrifugal contactors is designed to be short (30
seconds or less).
(3) Uranium reduction systems and equipment.
(i) 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.
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.
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. For those parts in contact with the process
stream, the system is constructed of equipment made of, or
protected by, materials such as glass, fluorocarbon polymers,
polyphenyl sulfate, polyether sulfone, and resin-impregnated
graphite.
(ii) 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.
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. For those parts in contact with the process
stream, the system is constructed of equipment made of, or
protected by, materials such as glass, fluorocarbon polymers,
polyphenyl sulfate, polyether sulfone, and resin-impregnated
graphite.
(4) Feed preparation systems.
Especially designed or prepared systems for producing
high-purity uranium chloride feed solutions for chemical exchange
uranium isotope separation plants.
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, fluorinated hydrocarbon polymers, polyphenyl sulfate
or polyether sulfone plastic-lined and resin-impregnated
graphite.
(5) Uranium oxidation systems.
Especially designed or prepared systems for oxidation of U+3 to
U+4 for return to the uranium isotope separation cascade in the
chemical exchange enrichment process.
These systems may incorporate equipment such as:
(i) 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; and
(ii) 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.
B. In the solid-liquid ion-exchange process, enrichment is
accomplished by uranium adsorption/desorption on a special,
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 in 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.
(1) Fast reacting ion exchange resins/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 373 K (100 °C) to 473 K (200 °C).
(2) Ion exchange columns.
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 373 K (100 °C) to 473 K (200 °C) and pressures above 0.7
MPa.
(3) Ion exchange reflux systems.
(i) Especially designed or prepared chemical or electrochemical
reduction systems for regeneration of the chemical reducing
agent(s) used in ion exchange uranium enrichment cascades.
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.
(ii) Especially designed or prepared chemical or electrochemical
oxidation systems for regeneration of the chemical oxidizing
agent(s) used in ion exchange uranium enrichment cascades.
The ion exchange enrichment 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.
C. Any other components especially designed or prepared for use
in a chemical exchange or ion exchange enrichment plant or in any
of the components described in this appendix.
[79 FR 39295, July 10, 2014]