Nuclear Non-proliferation Import and Export Control Regulations — A.2.4.1
A.2.4.1 Gas centrifuges and assemblies and components especially designed or prepared for use in gas centrifuges, including: A.2.4.1.1 Rotating components (a) complete rotor assemblies: thin-walled cylinders, or a number of interconnected thin-walled cylinders, manufactured from one or more of the high strength to density ratio materials. If interconnected, the cylinders are joined together by flexible bellows or rings as described in paragraph (c). The rotor is fitted with an internal baffle(s) and end caps, as described in paragraphs (d) and (e), 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 a thickness of 12 mm or less, a diameter of between 75 mm and 650 mm, and manufactured from high strength to density ratio materials; (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 is a short cylinder with a wall thickness of 3 mm or less, a diameter of between 75 mm and 650 mm, having a convolute, and manufactured from high strength to density ratio materials; (d) baffles: disc-shaped components of between 75 mm and 650 mm in 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 UF 6 gas circulation within the main separation chamber of the rotor tube, and manufactured from high strength to density ratio materials; and (e) top caps or bottom caps: disc-shaped components of between 75 mm and 650 mm in diameter especially designed or prepared to fit to the ends of the rotor tube, and so contain the UF 6 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 high strength to density ratio materials. NOTE 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) aluminium alloys capable of an ultimate tensile strength of 0.46 GPa or more; and (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 in N/m 3 and specific ultimate tensile strength is the ultimate tensile strength in N/m 2 divided by the specific weight in N/m 3 ). A.2.4.1.2 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 UF 6 -resistant material. The magnet couples with a pole piece or a second magnet fitted to the top cap described in paragraph A.2.4.1.1(e). The annular magnet may have a relationship between an outer and inner diameter smaller or equal to 1.6:1. It may also be in a form having an initial permeability of 0.15 H/m or more, or a remanence of 98.5% or more, or an energy product of greater than 80 kJ/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; or (2) active magnetic bearings especially designed or prepared for use in gas centrifuges; (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 with a hemisphere at one end with a means of attachment to the bottom cap described in paragraph A.2.4.