Canning materials

In the nuclear engineering field special magnesium-base alloys are extensively used as canning materials for uranium in gas-cooled reactors. 

Water The corrosion resistance of pure niobium in water and steam at elevated temperatures is not sufficient to allow its use as a canning material in water-cooled nuclear reactors. Alloys of niobium with molybdenum, titanium, vanadium and zirconium however have improved resistance and have possibilities in this application. Whilst the Nb-lOTi-lOMo alloy offers... 

Bureauand others have tried to apply the technique for evaluating the corrosion rate of painted metals, and although the results are controversial the method has also been used successfully in the study of canning materials and lacquered surfaces . 

Applications NAA is a powerful technique for ultratrace analysis of metallic impurities in plastics. PE is one of the most important canning materials for NAA, mainly on account of its high purity and low price. The cross-section of PE for thermal neutrons amounts to... 

The Corrosion Resistance of Potential Canning Materials for Nuclear Fuel Waste", KBS TR 31, 1977... 

Reactor fuel elements are contained in cans. In early British reactors, these were made of aluminium or aluminium/magnesium alloy to minimise capture of neutrons in the canning material. Nowadays, uranium fuel is enriched with respect to the 235U content, and the extra reactivity enables steel or zirconium cans to be used. In the original... 

Leaflets issued by British Industrial Plastics Limited British Polymer Training Association British Xylonite Company Limited BX Plastics Limited BXL Plastics Limited Colloids Limited Dawe Instruments Limited Grant Spacey Limited Guyson International Limited Linx Printing Technology Limited Lloyd Instruments Limited Newport Corporation R. Simon (Dryers) Limited W. Canning Materials Limited. 

The details of reprocessing depend on the kind of fuel and of fuel elements. In the head-end process the fuel elements are taken apart and the fuel is chopped if necessary. Canning material and fuel may be separated mechanically by use of special machines or by chemical means. The chemical head end may consist in the dissolution of the canning, but more favourably fuel and canning are separated by dissolving the fuel after chopping the fuel elements ( chop-leach process). 

Gambir or Gambler (Pale Catechu). An odorless brown powder prepd by drying an extract from a decoction of the leaves and twigs of an Indian shrub, Ourouparia or Uncaria gambir. It is insol in w and sol in ale. LTsed as an astringent and Canning material... 

Canning materials with a lower coefficient of thermal expansion should be sought. 

Coatings are also very common in food packaging. An example is tomato products that are corrosive to canning materials (such as iron) which must be protected by polymer coatings. Otherwise the food will be contaminated by metallic ions, and rupture of the can can occur. 

Heat conduction between fuel and can is further improved by using boruling materials such as molten sodium, graphite powder, etc. The bonding material should also provide some lubrication between pellets and can. The canning material itself must not only be corrosion resistant to the coolant at all temperatures but should react with neither the fuel nor the bonding material. 

Radiation effects and oxidation causes changes in the tensile properties of the canning material. Fresh fuel has a can that is very ductile whereas the can of spent high bum-up fuel normally is hard and brittle. 

Figure 7.9 Jig for nickel plating the interior and exterior of kettle bodies. Note the PtjTi auxiliary anodes inside the kettles. Photograph supplied by W. Canning Materials Ltd.

The system was studied to provide a background for the description of the interaction between carbide fuels and steel canning materials. 

Other metals such as beryllium, hafnium, niobium, vanadium, and zirconium are known to have nuclear and other properties which make them desirable materials of construction in various designs of nuclear reactor, but also they have, or may have in the future, important uses outside that field. All these metals except hafnium have been used or proposed for canning materials to clad and protect the nuclear fuel metals from corrosion by the reactor coolants or moderators, air, carbon dioxide, water, heavy water, graphite or molten sodium, etc. In some cases the specifications for neutron-absorbing impurities are of the same order as for the fuel metals uranium and thorium. Hafnium, however, with a high neutron-capture cross-section, is a useful material for reactor control rods and exhibits favourable metallurgical properties under irradiation. 

Tamayo et al. (1984) studied several samples of canned fruit in syrup and canned fruit juices and found that most exceeded the international limits. They mention the need for a control system for the quality of canning materials used in Mexico. They also remarked that the labels did not orient the consumer properly. Their results are presented in Table 20. 

Fi s. IM4 Jig rack mourning of electroplated articles, (a) A jig for nickel-plating the interiors and exteriors of kettle bodies. Note the use of platinized titanium auxiliary anodes inside the kettle to provide improved current drsiribution. (Courtesy W, Canning Materials Ltd.) (b) A transported-scrviccd electroplating system, which may be semi- or fully automatic in operation and which utilizes rack- or jig-mounting of components. (Courteiy Electroloid Ltd.) ... 

Fig. 8L17 A divided cell for decorative chroiniuni dMroplilliig (the Envii roBii process), (a) The cell design, (b) The electrode reactions. (Courtesy W. Canning Materials Ltd and IBM UK )...

The Niederaichbach nuclear plant Is a prototype of a COg cooled, D2O moderated pressure tube reactor, with an output of 100 MWe (refs 6). If construction proceeds according to schedule the plant will be commissioned in 1970. A noteworthy feature of this reactor Is the high coolant temperature of 550°C at the reactor outlet, requiring, of course, steel as canning material for the fuel. 

Beryllium had been proposed as the canning material for the fuel rods, since it had the great advantage that it was an extremely good moderator. Unfortunately, it also reacted with fast neutrons producing helium gas, which would form pockets within the metal. There were also problems with its mechanical properties as well as its toxicity. However, the main reason for abandoning it was rather more mundane ... 

In most cases, food is not a significant avenue of lead exposure. Lead-free solder is used in canneries to ensure that lead is not leached from the canning materials by acidic foodstuffs. One area that lead can pose a hazard to the food supply is lead-coated cookware and tableware. In many countries lead continues to be used as a pottery colorant and glaze. Acidic foods can leach and absorb lead from these decorated surfaces. Crops can absorb lead and other metals into their edible parts. Table 4 lists some examples of metal contamination in crops. 

---