Appendix B to Part 110 - Illustrative List of Gas Centrifuge Enrichment Plant Components Under NRC's Export Licensing Authority
10:2.0.1.1.20.11.139.7.23 : Appendix B
Appendix B to Part 110 - Illustrative List of Gas Centrifuge
Enrichment Plant Components Under NRC's Export Licensing Authority
1. Assemblies and components especially designed or prepared
for use in gas centrifuges.
Note:
The gas centrifuge normally consists of a thin-walled
cylinder(s) of between 75 mm and 650 mm diameter contained in a
vacuum environment and spun at high peripheral speed (of the order
of 300 m/per second and more) with the central axis vertical. In
order to achieve high speed, the materials of construction for the
rotating 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 uranium hexafluoride (UF6)
gas and featuring at least three separate channels of which two 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.
1.1 Rotating Components
(a) Complete Rotor Assemblies: Thin-walled cylinders, or a
number of interconnected thin-walled cylinders, manufactured from
one of the high strength-to-density ratio materials described in
the footnote to this section.
If interconnected, the cylinders are joined together by flexible
bellows or rings as described in § 1.1(c) of this appendix. The
rotor is fitted with an internal baffle(s) and end caps, as
described in § 1.1(d) and (e) of this appendix, if in final form.
However, the complete assembly may be delivered only partly
assembled.
(b) Rotor Tubes: Especially designed or prepared thin-walled
cylinders with thickness of 12 mm or less, a diameter of between 75
mm and 650 mm, and manufactured from one of the high
strength-to-density ratio materials described in the footnote to
this section.
(c) Rings or Bellows: Components especially designed or prepared
to give localized support to the rotor tube or to join together a
number of rotor tubes. The bellows in a short cylinder of wall
thickness 3 mm or less, a diameter of between 75 mm and 650 mm,
having a convolute, and manufactured from one of the high
strength-to-density ratio materials described in the footnote to
this section.
(d) Baffles: Disc shaped components of between 75 mm and 650 mm
diameter especially designed or prepared to be mounted inside the
centrifuge rotor tube, in order to isolate the take-off chamber
from the main separation chamber and, in some cases, to assist the
UF6 gas circulation within the main separation chamber of the rotor
tube, and manufactured from one of the high strength-to-density
ratio materials described in the footnote to this section.
(e) Top Caps/Bottom Caps: Disc shaped components of between 75
mm and 650 mm diameter especially designed or prepared to fit to
the ends of the rotor tube, and so contain the UF6 within the rotor
tube, and in some cases to support, retain or contain as an
integrated part, an element of the upper bearing (top cap) or to
carry the rotating elements of the motor and lower bearing (bottom
cap), and manufactured from one of the high strength-to-density
ratio materials described in the footnote to this section.
Footnote
The materials used for centrifuge rotating components include
the following:
(a) Maraging steel capable of an ultimate tensile strength of
1.95 GPa or more.
(b) Aluminum alloys capable of an ultimate tensile strength of
0.46 GPa or more.
(c) Filamentary materials suitable for use in composite
structures and having a specific modulus of 3.18 × 10 6 m or
greater and a specific ultimate tensile strength of 7.62 × 10 4 m
or greater.
(“Specific Modulus” is the Young's modulus in N/m 2 divided by the
specific weight inN/m 3 when measured at a temperature of 23 ±20 °C
and a relative humidity of 50 ±5 percent. “Specific tensile
strength” is the ultimate tensile strength in N/m 2 divided by the
specific weight in N/m 3 when measured at a temperature of 23 ±20
°C and a relative humidity of 50 ±5 percent.) 1.2 Static Components
(a) Magnetic Suspension Bearings: 1. Especially designed or
prepared bearing assemblies consisting of an annular magnet
suspended within a housing containing a damping medium. The housing
will be manufactured from a UF6 resistant material (see footnote to
§ 2 of this appendix). The magnet couples with a pole piece or a
second magnet fitted to the top cap described in § 1.1(e) of this
appendix. The magnet may be ring-shaped with a relation between
outer and inner diameter smaller or equal to 1.6:1. The magnet may
be in a form having an initial permeability of 0.15 Henry/meter or
more, or a remanence of 98.5 percent or more, or an energy product
of greater than 80,000 joules/m 3. In addition to the usual
material properties, it is a prerequisite that the deviation of the
magnetic axes from the geometrical axes is limited to very small
tolerances (lower than 0.1 mm) or that homogeneity of the material
of the magnet is specially called for.
2. Active magnetic bearings especially designed or prepared for
use with gas centrifuges. These bearings usually have the following
characteristics:
(i) Designed to keep centred a rotor spinning at 600 Hz or more;
and
(ii) Associated to a reliable electrical power supply and/or to
an uninterruptible power supply (UPS) unit in order to function for
more than 1 hour.
(b) Bearings/Dampers: Especially designed or prepared bearings
comprising a pivot/cup assembly mounted on a damper. The pivot is
normally a hardened steel shaft polished into a hemisphere at one
end with a means of attachment to the bottom cap described in §
1.1(e) of this appendix at the other. The shaft may, however, have
a hydrodynamic bearing attached. The cup is pellet-shaped with
hemispherical indentation in one surface. These components are
often supplied separately to the damper.
(c) Molecular Pumps: Especially designed or prepared cylinders
having internally machined or extruded helical grooves and
internally machined bores. Typical dimensions are as follows: 75 mm
to 650 mm internal diameter, 10 mm or more wall thickness, with a
length equal to or greater than the diameter. The grooves are
typically rectangular in cross-section and 2 mm or more in
depth.
(d) Motor Stators: Especially designed or prepared ring shaped
stators for high speed multi-phase alternating current (AC)
hysteresis (or reluctance) motors for synchronous operation within
a vacuum at a frequency of 600 Hz or greater and a power of 40
volts amps or greater. The stators may consist of multi-phase
windings on a laminated low loss iron core comprised of thin layers
typically 2.0 mm thick or less.
(e) Centrifuge housing/recipients: Components especially
designed or prepared to contain the rotor tube assembly of a gas
centrifuge. The housing consists of a rigid cylinder of wall
thickness up to 30 mm with precision machined ends to locate the
bearings and with one or more flanges for mounting. The machined
ends are parallel to each other and perpendicular to the cylinder's
longitudinal axis to within 0.05 degrees or less. The housing may
also be a honeycomb type structure to accommodate several rotor
tubes.
(f) Scoops: Especially designed or prepared tubes for the
extraction of UF6 gas from within the rotor tube by a Pitot tube
action (that is, with an aperture facing into the circumferential
gas flow within the rotor tube, for example by bending the end of a
radially disposed tube) and capable of being fixed to the central
gas extraction system.
2. Especially designed or prepared auxiliary systems,
equipment, and components for gas centrifuge enrichment
plants.
Note:
The auxiliary systems, equipment, and components for a gas
centrifuge enrichment plant are the systems of the 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 of 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” of 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, component and piping systems
are fabricated to very high vacuum and cleanliness standards.
Some of the items listed below 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 copper,
copper alloys, stainless steel, aluminum, aluminum oxide, aluminum
alloys, nickel or alloys containing 60 percent or more nickel, and
fluorinated hydrocarbon polymers.
(a) 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:
1. Feed autoclaves, ovens, or systems used for passing UF6 to
the enrichment process.
2. Desublimers, cold traps, or pumps used to remove UF6 from the
enrichment process for subsequent transfer upon heating.
3. Solidification or liquefaction stations used to remove UF6
from the enrichment process by compressing and converting UF6 to a
liquid or solid form.
4. “Product” and “tails” stations used for transferring UF6 into
containers.
(b) Machine Header Piping Systems: Especially designed or
prepared piping systems and header systems for handling UF6 within
the centrifuge cascades.
This piping network is normally of the “triple” header system
with each centrifuge connected to each of the headers. There is
therefore a substantial amount of repetition in its form. It is
wholly made of or protected by UF6 resistant materials (see Note to
this section) and is fabricated to very high vacuum and cleanliness
standards.
(c) Special shut-off and control valves:
1. Shut-off valves especially designed or prepared to act on the
feed, “product” or “tails” UF6 gaseous streams of an individual gas
centrifuge.
2. Bellows-sealed valves, manual or automated, shut-off or
control, made of or protected by materials resistant to corrosion
by UF6, with an inside diameter of 10 to 160 mm, especially
designed or prepared for use in main or auxiliary systems of gas
centrifuge enrichment plants.
Typical especially designed or prepared valves include
bellow-sealed valves, fast acting closure-types, fast acting
valves, and others.
(d) UF6 Mass Spectrometers/Ion Sources: 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 percent or more by
weight, or nickel-chrome alloys.
3. Electron bombardment ionization sources.
4. Having a collector system suitable for isotope analysis.
(e) Frequency Changers: Frequency changers (also known as
converters or inverters) especially designed or prepared to supply
motor stators as defined under § 1.2(d) of this appendix, or parts,
components, and subassemblies of such frequency changers having all
of the following characteristics:
1. A multiphase output of 600 Hz or greater; and
2. High stability (with frequency control better than 0.2
percent).
(f) Any other components especially designed or prepared for use
in a gas centrifuge enrichment plant or in any of the components
described in this appendix.
[79 FR 39291, July 10, 2014]