United Kingdom Statutory Instruments

(i) the manufacture of centrifuge rotor tubes or the assembly of gas centrifuges;

(ii) the manufacture of diffusion barriers;

(iii) the manufacture or assembly of laser-based systems;

(iv) the manufacture or assembly of electromagnetic isotope separators;

(v) the manufacture or assembly of columns or extraction equipment;

(vi) the manufacture of aerodynamic separation nozzles or vortex tubes;

(vii) the manufacture or assembly of uranium plasma generation systems;

(viii) the manufacture of zirconium tubes;

(ix) the manufacture or upgrading of heavy water or deuterium;

(x) the manufacture of nuclear grade graphite;

(xi) the manufacture of flasks for irradiated fuel;

(xii) the manufacture of reactor control rods;

(xiii) the manufacture of criticality safe tanks and vessels;

(xiv) the manufacture of irradiated fuel element chopping machines;

(xv) the construction of hot cells.

     2. In paragraph 1:

"centrifuge rotor tubes" means thin-walled cylinders as described in entry 5.1.1(b);

"gas centrifuges" means centrifuges as described in the Introductory Note to entry 5.1;

"diffusion barriers" means thin, porous filters as described in entry 5.3.1(a);

"laser-based systems" means systems incorporating those items described in entry 5.7;

"electromagnetic isotope separators" means those items referred to in entry 5.9.1 containing ion sources as described in entry 5.9.1(a);

"columns or extraction equipment" means those items as described in entries 5.6.1, 5.6.2, 5.6.3, 5.6.5, 5.6.6, 5.6.7 and 5.6.8;

"aerodynamic separation nozzles or vortex tubes" means separation nozzles and vortex tubes as described respectively in entries 5.5.1 and 5.5.2;

"uranium plasma generation systems" means systems for the generation of uranium plasma as described in entry 5.8.3;

"zirconium tubes" means tubes as described in entry 1.6;

"heavy water or deuterium" means deuterium, heavy water (deuterium oxide) and any other deuterium compound in which the ratio of deuterium to hydrogen atoms exceeds 1:5000;

"nuclear grade graphite" means graphite having a purity level better than 5 parts per million boron equivalent and with a density greater than 1.50g/cm³;

"flask for irradiated fuel" means a vessel for the transportation and/or storage of irradiated fuel which provides chemical, thermal and radiological protection, and dissipates decay heat during handling, transportation and storage;

"reactor control rods" means rods as described in entry 1.4;

"criticality safe tanks and vessels" means those items as described in entries 3.2 and 3.4;

"irradiated fuel element chopping machines" means equipment as described in entry 3.1;

"hot cells" means a cell or interconnected cells totalling at least 6m³ in volume with shielding equal to or greater than the equivalent of 0.5m of concrete, with a density of 3.2g/cm³ or greater, outfitted with equipment for remote operations.

     3. The numbered entries referred to in paragraph 2 are the entries so numbered in Annex II, which entries are set out (with other entries referred to in them) in Part II of this Schedule.

(a) The pure uranium nitrate solution is concentrated by evaporation and passed to a denitration process where it is converted to uranium oxide. This oxide is re-used in the nuclear fuel cycle.

(b) The intensely radioactive fission products solution is normally concentrated by evaporation and stored as a liquor concentrate. This concentrate may be subsequently evaporated and converted to a form suitable for storage or disposal.

(c) The pure plutonium nitrate solution is concentrated and stored pending its transfer to further process steps. In particular, holding or storage vessels for plutonium solutions are designed to avoid criticality problems resulting from changes in concentration and form of this stream.

Especially designed or prepared holding or storage vessels for use in a plant for the reprocessing of irradiated fuel. The holding or storage vessels must be resistant to the corrosive effect of nitric acid. The holding or storage vessels are normally fabricated of materials such as low carbon stainless steels, titanium or zirconium, or other high quality materials. Holding or storage vessels may be designed for remote operation and maintenance and may have the following features for control of nuclear criticality:

    (1) walls or internal structures with a boron equivalent of at least two per cent, or

    (2) a maximum diameter of 175 mm (7 in) for cylindrical vessels, or

    (3) a maximum width of 75 mm (3 in) for either a slab or annular vessel.

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     5. PLANTS FOR THE SEPARATION OF ISOTOPES OF URANIUM AND EQUIPMENT, OTHER THAN ANALYTICAL INSTRUMENTS, ESPECIALLY DESIGNED OR PREPARED THEREFOR
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     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.

     5.1.1. Rotating components


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(b) Rotor tubes:

Especially designed or prepared thin-walled cylinders with thickness of 12 mm (0.5 in) or less, a diameter of between 75 mm (3 in) and 400 mm (16 in), and manufactured from one or more of the high strength to density ratio materials described in the EXPLANATORY NOTE to this Section.

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EXPLANATORY NOTE
The materials used for centrifuge rotating components are:

(a) Maraging steel capable of an ultimate tensile strength of 2.05 x 10⁹ N/m² (300,000 psi) or more;

(b) Aluminium alloys capable of an ultimate tensile strength of 0.46 x 10⁹ N/m² (67,000 psi) or more;

(c) Filamentary materials suitable for use in composite structures and having a specific modulus of 12.3 x 10⁶m or greater and a specific ultimate tensile strength of 0.3 x 10⁶m or greater ("Specific Modulus" is the Young's Modulus in N/m² divided by the specific weight in N/m³; "Specific Ultimate Tensile Strength" is the ultimate tensile strength in N/m² divided by the specific weight in N/m³).

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     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 …

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     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.

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     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).

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     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 1,000 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 (eg, 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.

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     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.

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     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.