Materials for radiation sources transport packages
On 01.09.2010 we started new project: Tungsten heavy alloys production for radiation shields, espacially to be used in medicine. The project is financially supported by The National Centre for Research and Development www.ncbir.pl/ under contract NR15-0052-10/2010
The tungsten heavy alloys (WHA) are metal-metal composites produced by liquid phase sintering of mixed tungsten (90-97%), nickel, iron, copper and cobalt powders. After proper sintering the material consists of spherical tungsten particles embedded into a solid solution Ni-Fe-W(Co) or Ni-Cu-W matrix. These alloys exhibit unique combination of high density (17-18.6 g/cm3), high strength (700-900 MPa), good corrosion resistance, dumping capability, good thermal and electric conductivity and relatively high ductility which allow them to withstand moderate amounts of cold work. Their properties make them attractive for many applications e.g.: balance weights, welding electrodes, extruding dies, anti-vibration holders for tools and armour penetrators. The ductility and strength of heavy metals strongly depend on their microstructure which in turn is controlled by thermal treatment and trace impurity content.
Tungsten heavy alloys are worldwide more and more used as radiation shields. They successfully replace lead, formerly used in this application. The advantage of tungsten heavy alloys towards to lead is a combination of radiographic density, machinability, good corrosion resistance, high radiation absorption, high strength, high melting temperature and what is always pointed loss of toxicity. WHA can provide the same protection as lead with much reduced thickness of the wall of shields and containers. They are stable at high temperatures, what is important in case of fire, and they are characterized by good mechanical properties. These characteristics result in that this group of materials are used in such applications as: collimators, isotopes containers, different kinds of shield: e.g. syringe shields or nuclear shielding. They are utilized in geologging, pipe-line gamma inspection, industrial radiography, homeland security and border control and radiation shielding used in cancer treatment.