International Atomic Energy Agency
(Unofficial electronic edition)
| INFCIRC/254/Rev.1/Part 1*/
The Permanent Mission of [Member State] to the International Atomic Energy Agency presents its compliments to the Director General of the International Atomic Energy Agency and has the honour to refer to its letter of [date of previous communication] in which the Government of [Member State announced its decision to act in accordance with the guidelines for nuclear transfers annexed to that letter.
The Government of [Member State] has implemented these guidelines accordingly and hopes that other Governments, who have not yet done so, may decide to base their own nuclear export policies upon the guidelines.
As a member of the European Community, the Government of [Member State] has implemented these guidelines in accordance with the Declaration of Common Policy, communicated by the Resident Representative of Italy on behalf of the European Community, in his letter of 22 March 1985. The Government of [Member State] hopes that other governments, who have not yet done so, may decide to base their own nuclear export policies upon the said guidelines.**/
In the aforementioned letter the Government of [Member State] pointed out the need to remove safeguards and non-proliferation assurances from the field of commercial competition. This need still exists.
In the years since the guidelines were formulated and published in INFCIRC/254 developments in nuclear technology have brought about the need further to clarify parts of the trigger list which is incorporated in Annex A to the guidelines. In the interest of clarity the resultant new Part A of the Annex A and a revised Annex to it (new Annex B) have been incorporated in the attached copy of the complete guidelines.
The Government of [Member State] requests that the Director General of the International Atomic Energy Agency should circulate the texts of this note and its enclosure to all member governments for their information and as a demonstration of support by the Government of [Member State] for the Agency's non-proliferation objectives and safeguards activities.
The Permanent Mission of [Member State] avails itself of this opportunity to renew to the Director General of the International Atomic Energy Agency the assurances of its highest consideration.
Prohibition on nuclear explosives
Safeguards triggered by the transfer of certain technology
Special controls on sensitive exports
Special controls on export of enrichment facilities, equipment and technology
Controls on supplied or derived weapons-usable material
Controls on retransfer
the recipient of the retransfer or transfer will have provided the same assurances as those required by the supplier for the original transfer.
Support for effective IAEA safeguards
Similarly, they should make every effort to support the IAEA in increasing further the adequacy of safeguards in the light of technical developments and the rapidly growing number of nuclear facilities, and to support appropriate initiatives aimed at improving the effectiveness of IAEA safeguards.
Sensitive plant design features
Pending the early outcome of such consultations, suppliers will not act in a manner that could prejudice any measure that may be adopted by other suppliers concerning their current contacts with that recipient.
Upon the findings of such consultations, the suppliers, bearing in mind Article XII of the IAEA Statute, should agree on an appropriate response and possible action which could include the termination of nuclear transfers to that recipient.
Trigger List Referred to in Guidelines
PART A. MATERIAL AND EQUIPMENT
As defined in Article XX of the Statute of the International Atomic Energy Agency:
1.1. "Source material"
The term "source material" means uranium containing the mixture of isotopes occurring in nature; uranium depleted in the isotope 235; thorium; any of the foregoing in the form of metal, alloy, chemical compound, or concentrate; any other material containing one or more of the foregoing in such concentration as the Board of Governors shall from time to time determine; and such other material as the Board of Governors shall from time to time determine.
1.2. "Special fissionable material"
However, for the purposes of the Guidelines, items specified in subparagraph (a) below, and exports of source or special fissionable material to a given recipient country, within a period of 12 months, below the limits specified in subparagraph (b) below, shall not be included:
Special fissionable material when used in gram quantities or less as a sensing component in instruments; and
Source material which the Government is satisfied is to be used only in non-nuclear activities, such as the production of alloys or ceramics;
|Special fissionable material||50 effective grams;|
|Natural uranium||500 kilograms;|
|Depleted uranium||1 000 kilograms; and|
|Thorium||1 000 kilograms.|
The designation of items of equipment and non-nuclear materials (hereafter referred to as the "Trigger List") adopted by the Government is as follows (quantities below the levels indicated in the Annex B being regarded as insignificant for practical purposes):
2.1. Reactors and equipment therefor (see Annex B, section 1.);
2.2. Non-nuclear materials for reactors (see Annex B, section 2.);
2.3. Plants for the reprocessing of irradiated fuel elements, and equipment especially designed or prepared therefor (see Annex B, section 3.);
2.4. Plants for the fabrication of fuel elements (see Annex B, section 4.);
2.5. Plants for the separation of isotopes of uranium and equipment, other than analytical instruments, especially designed or prepared therefor (see Annex B, section 5.);
2.6. Plants for the production of heavy water, deuterium and deuterium compounds and equipment especially designed or prepared therefor (see Annex B, section 6.).
|Where the technology transferred is such as to make possible the construction in the recipient State of a facility of the following type, or major critical components thereof:||The following will be deemed to be facilities of the same type:|
|(a) an isotope separation plant of the gaseous diffusion type||any other isotope separation plant using the gaseous diffusion process|
|(b) an isotope separation plant of the gas centrifuge type||any other isotope separation plant using the gas centrifuge process.|
|(c) An isotope separation plant of the jet nozzle type||any other isotope separation plant using the jet nozzle process.|
|(d) an isotope separtion plant of the vortex type||any other isotope separation plant using the vortex process|
|(e) a fuel reprocessing plant using the solvent extraction process||any other fuel reprocessing plant using the solvent extraction process|
|(f) a heavy water plant using the exchange process||any other heavy water plant using the exchange process|
|(g) a heavy water plant using the electrolytic process||any other heavy water plant using the electrolytic process|
|(h) a heavy water plant using the hydrogen distillation process||any other heavy water plant using the hydrogen distillation process|
Note: In the case of reprocessing, enrichment, and heavy water facilities whose design, construction, or operation processes are based on physical or chemical processes other than those enumerated above, a similar approach would be applied to define facilities "of the same type" and a need to define major critical components of such facilities might arise.
Clarification of Items on the Trigger List
(as designated in Section 2 of Part A of Annex A)
1.1. Complete nuclear reactors
Nuclear reactors capable of operation so as to maintain a controlled self-sustaining fission chain reaction, excluding zero energy reactors, the latter being defined as reactors with a designed maximum rate of production of plutonium not exceeding 100 grams per year.
A "nuclear reactor" basically includes the items within or attached directly to the reactor vessel, the equipment which controls the level of power in the core, and the components which normally contain or come in direct contact with or control the primary coolant of the reactor core.
It is not intended to exclude reactors which could reasonably be capable of modification to produce significantly more than 100 grams of plutonium per year. Reactors designed for sustained operation at significant power levels, regardless of their capacity for plutonium production, are not considered as "zero energy reactors".
The export of the whole set of major items within this boundary will take place only in accordance with the procedures of the Guidelines. Those individual items within this functionally defined boundary which will be exported only in accordance with the procedures of the Guidelines are listed in paragraphs 1.2 to 1.7. The Government reserves the right to apply the procedures of the Guidelines to other items within the functionally defined boundary.
1.2. Reactor pressure vessels
Metal vessels, as complete units or as major shop-fabricated parts therefor, which are especially designed or prepared to contain the core of a nuclear reactor as defined in paragraph 1.1. above and are capable of withstanding the operating pressure of the primary coolant.
A top plate for a reactor pressure vessel is covered by item 1.2. as a major shop-fabricated part of a pressure vessel.
Reactor internals (eg support columns and plates for the core and other vessel internals, control rod guide tubes, thermal shields, baffles, core grid plates, diffuser plates, etc.) are normally supplied by the reactor supplier. In some cases, certain internal support components are included in the fabrication of the pressure vessel. These items are sufficiently critical to the safety and reliability of the operation of the reactor (and, therefore, to the guarantees and liability of the reactor supplier), so that their supply, outside the basic supply arrangement for the reactor itself, would not be common practice. Therefore, although the separate supply of these unique, especially designed and prepared, critical, large and expensive items would not necessarily be considered as falling outside the area of concern, such a mode of supply is considered unlikely.
1.3. Reactor fuel charging and discharging machines
Manipulative equipment especially designed or prepared for inserting or removing fuel in a nuclear reactor as defined in paragraph 1.1. above capable of on-load operation or employing technically sophisticated positioning or alignment features to allow complex off-load fuelling operations such as those in which direct viewing of or access to the fuel is not normally available.
1.4. Reactor control rods
Rods especially designed or prepared for the control of the reaction rate in a nuclear reactor as defined in paragraph 1.1. above.
This item includes, in addition to the neutron absorbing part, the support or suspension structures therefor if supplied separately.
1.5. Reactor pressure tubes
Tubes which are especially designed or prepared to contain fuel elements and the primary coolant in a reactor as defined in paragraph 1.1. above at an operating pressure in excess of 5.1 MPa (740 psi).
1.6. Zirconium tubes
Zirconium metal and alloys in the form of tubes or assemblies of tubes, and in quantities exceeding 500 kg in any period of 12 months, especially designed or prepared for use in a reactor as defined in paragraph 1.1. above, and in which the relation of hafnium to zirconium is less than 1:500 parts by weight.
1.7. Primary coolant pumps
Pumps especially designed or prepared for circulating liquid metal as primary coolant for nuclear reactors as defined in paragraph 1.1. above.
2.1. Deuterium and heavy water
Deuterium, heavy water (deuterium oxide) and any other deuterium compound in which the ratio of deuterium to hydrogen atoms exceeds 1:5000 for use in a nuclear reactor as defined in paragraph 1.1. above in quantities exceeding 200 kg of deuterium atoms for any one recipient country in any period of 12 months.
2.2 Nuclear grade graphite
Graphite having a purity level better than 5 parts per million boron equivalent and with a density greater than 1.50 g/cm3 in quantities exceeding 3. 104 kg (30 metric tons) for any one recipient country in any period of 12 months.
Reprocessing irradiated nuclear fuel separates plutonium and uranium from intensely radioactive fission products and other transuranic elements. Different technical processes can accomplish this separation. However. over the years Purex has become the most commonly used and accepted process. Purex involves the dissolution of irradiated nuclear fuel in nitric acid, followed by separation of the uranium, plutonium, and fission products by solvent extraction using a mixture of tributyl phosphate in an organic diluent.
Purex facilities have process functions similar to each other, including: irradiated fuel element chopping, fuel dissolution, solvent extraction, and process liquor storage. There may also be equipment for thermal denitration of uranium nitrate, conversion of plutonium nitrate to oxide or metal, and treatment of fission product waste liquor to a form suitable for long term storage or disposal. However, the specific type and configuration of the equipment performing these functions may differ between Purex facilities for several reasons, including the type and quantity of irradiated nuclear fuel to be reprocessed and the intended disposition of the recovered materials, and the safety and maintenance philosophy incorporated into the design of the facility.
A "plant for the reprocessing of irradiated fuel elements", includes the equipment and components which normally come in direct contact with and directly control the irradiated fuel and the major nuclear material and fission-product processing streams.
These processes, including the complete systems for plutonium conversion and plutonium metal production, may be identified by the measures taken to avoid criticality (eg by geometry), radiation exposure (eg by shielding). and toxicity hazards (eg by containment).
The export of the whole set of major items this within this boundary will take place only in accordance with the procedures of the Guidelines.
The Government reserves to itself the right to apply the procedures of the Guidelines to other items within the functionally defined boundary as listed below.
Items of equipment that are considered to fall within the meaning of the phrase "and equipment especially designed or prepared" for the reprocessing of irradiated fuel elements include:
3.1. Irradiated fuel element chopping machines
This equipment breaches the cladding of the fuel to expose the irradiated nuclear material to dissolution. Especially designed metal cutting shears are the most commonly employed, although advanced equipment such as lasers, may be used.
Remotely operated equipment especially designed or prepared for use in a reprocessing plant as identified above and intended to cut, chop or shear irradiated nuclear fuel assemblies, bundles or rods.
Dissolvers normally receive the chopped-up spent fuel. In these critically safe vessels, the irradiated nuclear material is dissolved in nitric acid and the remaining hulls removed from the process stream.
Critically safe tanks (eg small diameter, annular or slab tanks) especially designed or prepared for use in a reprocessing plant as identified above, intended for dissolution of irradiated nuclear fuel and which are capable of withstanding hot, highly corrosive liquid, and which can be remotely loaded and maintained.
3.3. Solvent extractors and solvent extraction equipment
Solvent extractors both receive the solution of irradiated fuel from the dissolvers and the organic solution which separates the uranium, plutonium, and fission products. Solvent extraction equipment is normally designed to meet strict operating parameters, such as long operating lifetimes with no maintenance requirements or adaptability to easy replacement, simplicity of operation and control, and flexibility for variations in process conditions.
Especially designed or prepared solvent extractors such as packed or pulse columns, mixer settlers or centrifugal contactors for use in a plant for the reprocessing of irradiated fuel. Solvent extractors must be resistant to the corrosive effect of nitric acid. Solvent extractors are normally fabricated to extremely high standards (including special welding and inspection and quality assurance and quality control techniques) out of low carbon stainless steels, titanium, zirconium, or other high quality materials.
3.4. Chemical holding or storage vessels
Three main process liquor streams result from the solvent extraction step. Holding or storage vessels are used in the further processing of all these streams, as follows:
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:
3.5. Plutonium nitrate to oxide conversion system
In most reprocessing facilities this final process involves the conversion of the plutonium nitrate solution to plutonium dioxide. The main functions involved in this process are:
process feed storage and adjustment, precipitation and solid/liquor separation, calcination, product handling, ventilation, waste management, and process control.
Complete systems especially designed or prepared for the conversion of plutonium nitrate to plutonium oxide, in particular adapted so as to avoid criticality and radiation effects and to minimize toxicity hazards.
3.6. Plutonium oxide to metal production system
This process, which could be related to a reprocessing facility, involves the fluorination of plutonium dioxide, normally with highly corrosive hydrogen fluoride, to produce plutonium fluoride which is subsequently reduced using high purity calcium metal to produce metallic plutonium and a calcium fluoride slag. The main functions involved in this process are: fluorination (eg involving equipment fabricated or lined with a precious metal), metal reduction (eg employing ceramic crucibles), slag recovery, product handling, ventilation, waste management and process control.
Complete systems especially designed or prepared for the production of plutonium metal, in particular adapted so as to avoid criticality and radiation effects and to minimize toxicity hazards.
A "plant for the fabrication of fuel elements" includes the equipment:
The export of the whole set of items for the foregoing operations will take place only in accordance with the procedures of the Guidelines. The Government will also give consideration to application of the procedures of Guidelines to individual items intended for any of the foregoing operations, as well as for other fuel fabrication operations such as checking the integrity of the cladding or the seal, and the finishing treatment of the sealed fuel.
Items of equipment that are considered to fall within the meaning of the phrase "equipment other than analytical instruments, especially designed or prepared" for the separation of isotopes of uranium include:
5.1. Gas centrifuges and assemblies and components especially designed or prepared for use in gas centrifuges
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.
If interconnected, the cylinders are joined together by flexible bellows or rings as described in section 5.1.1.(c) following. The rotor is fitted with an internal baffle(s) and end caps, as described in section 5.1.1.(d) and (e) following, if in final form. However the complete assembly may be delivered only partly assembled.
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 of the high strength to density ratio materials described in the EXPLANATORY NOTE to this Section.
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 of wall thickness 3 mm (0.12 in) or less, a diameter of between 75 mm (3 in) and 400 mm (16 in), having a convolute, and manufactured from one of the high strength to density ratio materials described in the EXPLANATORY NOTE to this Section.
Disc-shaped components of between 75 mm (3 in) and 400 mm (16 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 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 EXPLANATORY NOTE to this Section.
Disc-shaped components of between 75 mm (3 in) and 400 mm (16 in) 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 EXPLANATORY NOTE to this Section.
The materials used for centrifuge rotating components are:
5.1.2. Static components
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 EXPLANATORY NOTE to Section 5.2.). The magnet couples with a pole piece or a second magnet fitted to the top cap described in Section 5.1.1.(e). 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 H/m (120,000 in CGS units) or more, or a remanence of 98.5% or more, or an energy product of greater than 80 kJ/m3 (107 gauss-oersteds). 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 0.004 in) or that homogeneity of the material of the magnet is specially called for.
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 section 5.1.1 .(e) at the other. The shaft may however have a hydrodynamic bearing attached. The cup is pellet-shaped with a hemispherical indentation in one surface. These components are often supplied separately to the damper.
Especially designed or prepared cylinders having internally machined or extruded helical grooves and internally machined bores. Typical dimensions are as follows: 75 mm (3 in) to 400 mm (16 in) internal diameter, 10 mm (0.4 in) or more wall thickness, 1 to 1 length to diameter ratio. The grooves are typically rectangular in cross-section and 2 mm (0.08 in) or more in depth.
Especially designed or prepared ring-shaped stators for high speed multiphase AC hysteresis (or reluctance) motors for synchronous operation within a vacuum in the frequency range of 600 - 2000 Hz and a power range of 50 - 1000 VA. The stators consist of multi-phase windings on a laminated low loss iron core comprised of thin layers typically 2.0 mm (0.08 in) thick or less.
5.2. Especially designed or prepared auxiliary systems, equipment and components for gas centrifuge enrichment plants
The auxiliary systems, equipment and components for a gas centrifuge enrichment plant are the systems of 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" 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" UF6 gaseous streams flowing from the centrifuges are also passed by way of cascade header pipework to cold traps (operating at about 203 K (-70oC)) 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, components and piping systems are fabricated to very high vacuum and cleanliness standards.
Especially designed or prepared process systems including:
Feed autoclaves (or stations), used for passing UF6 to the centrifuge cascades at up to 100 kPa (15 psi) and at a rate of 1 kg/h or more;
Desublimers (or cold traps) used to remove UF6 from the cascades at up to 3 kPa (0.5 psi) pressure. The desublimers are capable of being chilled to 203 K (-70oC) and heated to 343 K (70oC);
"Product' and "Tails" stations used for trapping UF6 into containers.
This plant, equipment and pipework is wholly made of or lined with UF6-resistant materials (see EXPLANATORY NOTE to this section) and is fabricated to very high vacuum and cleanliness standards.
5.2.2. Machine header piping systems
Especially designed or prepared piping systems and header systems for handling UF6 within the centrifuge cascades. The piping network is normally of the 'triple' header system with each centrifuge connected to each of the headers. There is thus a substantial amount of repetition in its form. It is wholly made of UF6-resistant materials (see EXPLANATORY NOTE to this section) and is fabricated to very high vacuum and cleanliness standards.
5.2.3. UF6 mass spectrometers/ion sources
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:
5.2.4. Frequency changers
Frequency changers (also known as converters or invertors) especially designed or prepared to supply motor stators as defined under 5.1 .2.(d), or parts, components and sub-assemblies of such frequency changers having all of the following characteristics:
The items listed above 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 stainless steel, aluminium, aluminium alloys, nickel or alloys containing 60% or more nickel.
5.3. Especially designed or prepared assemblies and components for use in gaseous diffusion enrichment
In the gaseous diffusion method of uranium isotope separation, the main technological assembly is a special porous gaseous diffusion barrier, heat exchanger for cooling the gas (which is heated by the process of compression), seal valves and control values, and pipelines. In as much as gaseous diffusion technology uses uranium hexafluoride (UF6), all equipment pipeline and instrumentation surfaces (that come in contact with the gas) must be made of materials that remain stable in contact with UF6. A gaseous diffusion facility requires a number of these assemblies, so that quantities can provide an important indication of end use.
5.3.2. Diffuser housings
Especially designed or prepared hermetically sealed cylindrical vessels greater then 300 mm (12 in) in diameter and greater than 900 mm (35 in) in length, or rectangular vessels of comparable dimensions, which have an inlet connection and two outlet connections all of which are greater than 50 mm (2 in) in diameter, for containing the gaseous diffusion barrier, made of or lined with UF-6 resistant materials and designed for horizontal or vertical installation.
5.3.3. Compressors and gas blowers
Especially designed or prepared axial, centrifugal, or positive displacement compressors, or gas blowers with a suction volume capacity of 1 m3/min or more of UF6, and with a discharge pressure of up to several hundred kPa (100 psi), designed for long-term operation in the UF6 environment with or without an electrical motor of appropriate power, as well as separate assemblies of such compressors and gas blowers. These compressors and gas blowers have a pressure ratio between 2:1 and 6:1 and are made of, or lined with, materials resistant to UF6.
5.3.4. Rotary shaft seals
Especially designed or prepared vacuum seals, with seal feed and seal exhaust connections, for sealing the shaft connecting the compressor or the gas blower rotor with the driver motor so as to ensure a reliable seal against in-leaking of air into the inner chamber of the compressor or gas blower which is filled with UF6. Such seals are normally designed for a buffer gas in-leakage rate of less than 1000 cm3/min (60 in3/min).
5.3.5. Heat exchangers for cooling UF6
Especially designed or prepared heat exchangers made of or lined with UF6-resistant materials (except stainless steel) or with copper or any combination of those metals, and intended for a leakage pressure change rate of less than 10 Pa (0.0015 psi) per hour under a pressure difference of 100 kPa (15 psi).
5.4. Especially designed or prepared auxiliary systems, equipment and components for use in gaseous diffusion enrichment
The auxiliary systems, equipment and components for gaseous diffusion enrichment plants are the systems of plant needed to feed UF6 to the gaseous diffusion assembly, to link the individual assemblies to each other to form cascades (or stages) to allow for progressively higher enrichments and to extract the "product" and "tails" UF6 from the diffusion cascades. Because of the high inertial properties of diffusion cascades, any interruption in their operation, and especially their shutdown, leads to serious consequences. Therefore, a strict and constant maintenance of vacuum in ail technological systems, automatic protection from accidents, and precise automated regulation of the gas flow is of importance in a gaseous diffusion plant. All this leads to a need to equip the plant with a large number of special measuring, regulating and controlling systems.
Normally UF6 is evaporated from cylinders placed within autoclaves and is distributed in gaseous form to the entry point by way of cascade header pipework. The "product" and "tails" UF6 gaseous streams flowing from exit points are passed by way of cascade header pipework to either cold traps or to compression stations where the UF6 gas is liquefied prior to onward transfer into suitable containers for transportation or storage. Because a gaseous diffusion enrichment plant consists of a large number of gaseous diffusion assemblies arranged in cascades, there are many kilometers of cascade header pipework, incorporating thousands of welds with substantial amounts of repetition of layout. The equipment, components and of piping systems are fabricated to very high vacuum and cleanliness standards.
Especially designed or prepared process systems, capable of operating at pressures of 300 kPa (45 psi) or less, including:
Feed autoclaves (or systems), used for passing UF6 to the gaseous diffusion cascades; Desublimers (or cold traps) used to remove UF6 from diffusion cascades;
Liquefaction stations where UF6 gas from the cascade is compressed and cooled to form liquid UF6;
"Product" or "tails" stations used for transferring UF6 into containers.
5.4.2. Header piping systems
Especially designed or prepared piping systems and header systems for handling UF6 within the gaseous diffusion cascades. This piping network is normally of the "double" header system with each cell connected to each of the headers.
5.4.3. Vacuum systems
5.4.4. Special shut-off and control valves
Especially designed or prepared manual or automated shut-off and control bellows valves made of UF6-resistant materials with a diameter of 40 to 1500 mm (1.5 to 59 in) for installation in main and auxiliary systems of gaseous diffusion enrichment plants.
5.4.5. UF6 mass spectrometers/ion sources
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:
The items listed above either come into direct contact with the UF6 process gas or directly control the flow within the cascade. All surfaces which come into contact with the process gas are wholly made of or lined with, UF6-resistant materials. For the purposes of the sections relating to gaseous diffusion items the materials resistant to corrosion by UF6 include stainless steel, aluminium, aluminium alloys, aluminium oxide, nickel or alloys containing 60% or more nickel and UF6-resistent fully fluorinated hydrocarbon polymers
5.5. Jet nozzle separation units
5.6. Vortex separation units
Heavy water can be produced by a variety of processes. However, the two processes that have proven to be commercially viable are the water-hydrogen suphide exchange process (GS process) and the ammonia-hydrogen exchange process.
The GS process is based upon the exchange of hydrogen and deuterium between water and hydrogen sulphide within a series of towers which are operated with the top section cold and the bottom section hot. Water flows down the towers while the hydrogen sulphide gas circulates from the bottom to the top of the towers. A series of perforated trays are used to promote mixing between the gas and the water. Deuterium migrates to the water at low temperatures and to the hydrogen sulphide at high temperatures. Gas or water, enriched in deuterium, is removed from the first stage lowers at the junction of the hot and cold sections and the process is repeated in subsequent stage towers. The product of the test cage, water enriched up to 30% in deuterium, is sent to a distillation unit to produce reactor grade heavy water; i.e., 99.75% deuterium oxide.
The ammonia-hydrogen exchange process can extract deuterium from synthesis gas through contact with liquid ammonia in the presence of a catalyst. The synthesis gas is fed into exchange towers and to an ammonia converter. Inside the towers the gas flows from the bottom to the top while the liquid ammonia flows from the top to the bottom. The deuterium is stripped from the hydrogen in the synthesis gas and concentrated in the ammonia. The ammonia then flows into an ammonia cracker at the bottom of the tower while the gas flows into an ammonia converter at the top. Further enrichment takes place in subsequent stages and reactor grade heavy water is produced through final distillation. The synthesis gas feed can be provided by an ammonia plant that, in turn, can be constructed in association with a heavy water ammonia-hydrogen exchange plant. The ammonia-hydrogen exchange process can also use ordinary water as a feed source of deuterium.
Many of the key equipment items for heavy water production plants using GS or the ammonia-hydrogen exchange processes are common to several segments of the chemical and petroleum industries This is particularly so for small plants using the GS process. However, few of the items are available "off-the-shelf". The GS and ammonia-hydrogen processes require the handling of large quantities of flammable, corrosive and toxic fluids at elevated pressures. Accordingly, in establishing the design and operating standards for plants and equipment using these processes, careful attention to the materials selection and specifications is required to ensure long service life with high safety and reliability factors. The choice of scale is primarily a function of economics and need. Thus, most of the equipment items would be prepared according to the requirements of the customer.
Finally, it should be noted that, in both the GS and the ammonia-hydrogen exchange processes, items of equipment which individually are not especially designed or prepared for heavy water production can be assembled into systems which are especially designed or prepared for producing heavy water. The catalyst production system used in the ammonia-hydrogen exchange process and water distillation systems used for the final concentration of heavy water to reactor-grade in either process are examples of such systems.
The items of equipment which are especially designed or prepared for the production of heavy water utilizing either the water-hydrogen suphide exchange pro cess or the ammonia-hydrogen exchange process include the following:
6.1. Water-Hydrogen Sulphide Exchange Towers
Exchange towers fabricated from fine carbon steel (such as ASTM A516) with diameters of 6 m (20 ft) to 9 m (30 ft), capable of operating at pressures greater than or equal to 2 MPa (300 psi) and with a corrosion allowance of 6 mm or greater, especially designed or prepared for heavy water production utilizing the water-hydrogen sulphide exchange process.
6.2. Blowers and Compressors
Single stage, low head (i.e., 0.2 MPa or 30 psi) centrifugal blowers or compressors for hydrogen sulphide -gas circulation (i.e., gas containing more than 70% H2S) especially designed or prepared for heavy water production utilizing the water-hydrogen sulphide exchange process. These blowers or compressors have a throughput capacity greater than or equal to 56 m3/second (120,000 SCFM) while operating at pressures greater than or equal to 1.8 MPa (260 psi) suction and have seals designed for wet H2S service.
6.3. Ammonia-Hydrogen Exchange Towers
Ammonia-hydrogen exchange towers greater than or equal to 35 m (114.3 ft) in height with diameters of 1.5 m (4.9 ft) to 2.5 m (8.2 ft) capable of operating at pressures greater than 15 MPa (2225 psi) especially designed or prepared for heavy water production utilizing the ammonia-hydrogen exchange process. These towers also have at least one flanged, axial opening of the same diameter as the cylindrical part through which the tower internals can be inserted or withdrawn.
6.4. Tower Internals and Stage Pumps
Tower internals and stage pumps especially designed or prepared for towers for heavy water production utilizing the ammonia-hydrogen exchange process. Tower internals include especially designed stage contactors which promote intimate gas/liquid contact. Stage pumps include especially designed submersible pumps for circulation of liquid ammonia within a contacting stage internal to the stage towers.
6.5. Ammonia Crackers
Ammonia crackers with operating pressures greater than or equal to 3 MPa (450 psi) especially designed or prepared for heavy water production utilizing the ammonia- hydrogen exchange process.
6.6. Infrared Absorption Analyzers
Infrared absorption analyzers capable of "on-line" hydrogen/deuterium ratio analysis where deuterium concentrations are equal to or greater than 90%.
6.7. Catalytic Burners
Catalytic burners for the conversion of enriched deuterium gas into heavy water especially designed or prepared for heavy water production utilizing the ammonia-hydrogen exchange process.
Criteria for Levels of Physical Protection
Use and Storage within an area to which access in controlled.
Transportation under special precautions including prior arrangements among sender, recipient and carrier, and prior agreement between entities subject to the jurisdiction and regulation of supplier and recipient States, respectively, in case of international transport specifying time, place and procedures for transferring transport responsibility.
Use and Storage within a protected area to which access is controlled, i.e. an area under constant surveillance by guards or electronic devices, surrounded by a physical barrier with a limited number of points of entry under appropriate control, or any area with an equivalent level of physical protection.
Transportation under special precautions including prior arrangements among sender, recipient and carrier, and prior agreement between entities subject to the jurisdiction and regulation of supplier and recipient States, respectively, in case of international transport, specifying time, place and procedures for transferring transport responsibility.
Materials in this category shall be protected with highly reliable systems against unauthorized use as follows:
Use and Storage within a highly protected area, i.e. a protected area as defined for Category II above, to which, in addition, access is restricted to persons whose trustworthiness has been determined, and which is under surveillance by guards who are in close communication with appropriate response forces. Specific measures taken in this context should have as their objective the detection and prevention of any assault, unauthorized access or unauthorized removal of material
Transportation under special precautions as identified above for transportation of Category II and III materials and, in addition, under constant surveillance by escorts and under conditions which assure close communication with appropriate response forces.
|Table: Categorization of Nuclear Material|
|1. Plutonium[a]||Unirradiated[b]||2 kg or more||Less than 2 kg but more than 500 g||500 g or less[c]|
||5 kg or more||Less than 5 kg but more than 1 kg||1 kg or less[c]|
||-||10 kg or more||Less than 10 kg[c]|
||10 kg or more|
|3. Uranium-233||Unirradiated[b]||2 kg or more||Less than 2 kg but more than 500 g||500 g or less[c]|
|4. Irradiated fuel||Depleted or natural uranium, thorium or low-enriched fuel (less than 10% fissile content)[e],[f]|
**/ Paragraph in the notes verbales from the members of the European Community used in place of the second paragraph above.
[a] As identified in the Trigger List.
[b] Material not irradiated in a reactor or material irradiated in a reactor but with a radiation level equal to or less than 100 rads/hour at one metre unshielded.
[c] Less than a radiologically significant quantity should be exempted.
[d] Natural uranium, depleted uranium and thorium and quantities of uranium enriched to less than 10% not falling in Category III should be protected in accordance with prudent management practice.
[e] Although this level of protection is recommended, it would be open to States, upon evaluation of the specific circumstances, to assign a different category of physical protection.
[f] Other fuel which by virtue of its original fissile material content is classified as Category I or II before irradiation may be reduced one category level while the radiation level from the fuel exceeds 100 rads/hour at one metre unshielded.