Production

A nuclear weapon is a sophisticated device, and depending upon the complexity of the design and the constraints on the designer -- such as size, weight, and amount of special nuclear materials which can be used -- may or may not require very precise manufacture. At the state of the art, however, factories producing the nuclear components (and some nonnuclear components) of modern devices must be capable of carrying out dimensional measurements which are both precise and accurate. Relative thicknesses must be measured to high precision, and the absolute values of those measurements must be compared to a set of standards with extreme accuracy.

The term "Conversion Time" is used in the counter-proliferation field to define time needed to convert diverted fissile material into a form that could be used in a nuclear weapon. The times are: for each of plutonium and highly-enriched uranium, 7 to 10 days; for plutonium oxide 1 to 3 weeks; for plutonium in spent nuclear-reactor fuel, 1 to 3 months [the time required for reproceesing]; for low-enriched and natural uranium 12 months [the time required for enrichment to weapons grade].

It is common, of course, for the most technically advanced nuclear powers to employ all of the modern tools of computer-assisted fabrication, including computer numerically controlled (CNC) machine tools. Shapes which can be manufactured with a modern 5-axis CNC machine tool can be approximated on a simpler machine if the work can be repositioned during machining or if the component can be made in parts which are later joined together. Significant hand work is usually required in either case. The accuracy of the approximation depends upon the precision with which the work can be repositioned or with which the separate components can be joined and in both instances, on the skills of the engineers/machinists. The history of American nuclear efforts is illustrative. The first thermonuclear bomb was produced in the 1951-1952 time frame; the first use of 3-axis machine tools occurred in 1952, and the first 5-axis machine tools were used in 1954.

In most cases, the technologies, the equipment, and the know-how required for the production of equipment used to manufacture nuclear weapons are dual-use and affect civilian applications where, for example, considerations of costs, flexibility, and competitiveness have become major concerns. A number of different technologies associated with a modern industrial base include many types of machine tools and processing equipment, certain inspection equipment, and certain robots.

Machine tools include NC (numerically controlled) machines in which the motions of the various axes are simultaneously and continually coordinated, thereby maintaining a predetermined (programmed) path. This includes turning, milling, and grinding machines and electrical discharge machines (EDM). Advanced manufacturing technique equipment includes spin, flow, and shear forming machines; filament-winding machines; hot isostatic presses; high-temperature furnaces and heaters; equipment for the manufacture of centrifuge rotors; vibration/shaker systems; and flash x-ray systems. It is often suggested that all or even most of these manufacturing and mensuration systems are required to build weapons of mass destruction in general and nuclear weapons in particular.

Manufacturing technologies are fundamental to the national industrial base. As much as any other technology, they are vital for the manufacture of military and civil hardware, and they either enable the manufacture of vital military systems or are essential for the design and manufacture of future military systems. Without some level of manufacturing equipment capability, it would be impossible to produce the military systems used by the world's military forces. Many commercial technologies are far more advanced than those available to the first several nuclear weapon states when they built their first nuclear and thermonuclear weapons, weapons generally considered quite satisfactory for their avowed purposes of deterrence and warfighting.

Modern weapon systems require a variety of processing equipment to manufacture necessary components. For example, machine tools or precision casting are used in the machining of hemi-shells for nuclear weapons; spin, flow, and shear forming machines are required for the fabrication of thin-walled, long, concentric hollow bodies, such as rotors for centrifuge devices used in uranium enrichment. Superplastic forming/diffusion bonding equipment is used for the fabrication of sheet metal structures of advanced alloys (e.g., titanium, nickel, and aluminum), in which reliability and cost are important factors, and high-temperature furnaces are used for casting uranium and plutonium, both key weapons materials.

Metrology covers technologies for dimensional measuring systems and equipment needed for precise determination of the dimensions of manufactured parts, machine tools, and inspection machines. Included are systems for in-process measurement, as well as post-manufacture inspection. This technology area is of paramount importance for the construction of systems incorporating mechanical or electrical com-ponents built to exacting tolerances, whether such hardware is military or civil. It is highly dependent on sensors, positioners, feedback systems, digital computers, and associated components and hardware. Included in the list of metrology equipment are coordinate, linear, and angular measurement machines using laser, standard light, and noncontact techniques. The tolerances of parts measured range from ±1 nm (corresponding to an optical surface finish prepared by diamond turning with ion beam polishing) to ±10 mm (corresponding to more traditional metal machining).

Modern precision manufacturing depends upon being able to make a large number of dimensional measurements precisely and accurately, and to know that measurements made at each site can be referred to a set of secondary standards which can, if necessary, be calibrated against the international standards. A centimeter measured in one laboratory must be the same as a centimeter measured with different equipment at another laboratory, and that equality must be demonstrable quickly and economically. In many ways, technological progress has been demarcated by our ability to make precision, standard measurements and to transfer this ability from the laboratory to the production floor. This is the science of metrology. Accurate dimensional inspection is essential for the design, development, manufacture, and use of a wide range of military hardware. Dimensional inspection machines are used for the measurement of centrifuge and nuclear weapons parts; linear inspection machines are used for the measurement of bearing races or shafts (used in advanced machine tools), centrifuges, and nuclear weapons parts. Specialized measuring equipment is critical for measuring hemi-shells.

The term "robots" covers the technology for the general category of robots, controllers, and end-effectors, which are used in conjunction with other manufacturing equipment for the production or testing of critical hardware. Robots can essentially be separated into four distinct disciplines, the robot, the controller (computer), sensors (the "eyes" of the robot), and end-effectors (the "gripper"). Robots have found a wide range of applications in manufacturing, including welders, sprayers, assemblers, loaders/unloaders, etc. They have also found use in handling hazardous or radioactive materials, transporting explosive weapons, and performing tasks in space. In most advanced manufacturing plants robots have replaced humans in many operations which are repetitive and do not require human intervention. Such applica-tions include welding, painting, surveillance, and pick-and-place assembly. This type of robot is commonplace in industrial countries and is not included in this document. Robots are indispensable in many hazardous military operations, including the handling of munitions, operating in highly radioactive environments, and performing tasks in space. The use of robots in these applications extends the military capability much further than what could be accomplished with "protected" humans.

Signatures

Every stage of nuclear weapon development, from material production to deployment, can generate signatures that provide some indication of a weapon program's existence or status, although only a few of them point fairly un-ambiguously to a nuclear weapon program.

Final assembly of nuclear weapons can take place at small facilities. Indicators of such facilities could include special security arrangements and structures designed to handle accidental detonation of high explosives. These signs, however, could also indicate conventional military facilities.

Import patterns of dual-use items might again provide indicators of intent to fabricate weapons. During their inspections of weapon facilities in Iraq, the IAEA found items such as computer-numerically controlled (CNC) machinery, two-axis lathes, vacuum furnaces, and isostatic presses that had been imported through a vast network of foreign suppliers and front companies. Since this equipment has a variety of industrial and nonnuclear military uses, it would be very difficult to determine its exact connection to a nuclear program simply by knowing the quantities being imported. Nevertheless, if sufficient monitoring could be implemented to detect and analyze changes or unusual patterns of import, or if reliable accounts of these items' ultimate end-use could be kept, tracking some subset of duaI-use equipment might provide an indication of weapon development. The import of a suite of multiuse items would provide more important information than that of individual items.

Effluents and solid waste from a suspected weapon-fabrication site might include characteristic substances associated with working plutonium metal ''buttons' into raw shapes before machining, such as tantalum, magnesium oxide, aluminum, graphite, calcium fluoride, plutonium, and plutonium oxide.

References

• Adapted from - Nuclear Weapons Technology Militarily Critical Technologies List (MCTL) Part II: Weapons of Mass Destruction Technologies