Structure of Metals DOE-HDBK-1017/1-93 IMPERFECTIONS IN METALS Type 304 stainless steel (containing 18%-20% chromium and 8%-10.5% nickel) is used in the tritium  production  reactor tanks,  process  water  piping,  and original  process  heat exchangers. This alloy resists most types of corrosion. The wide variety of structures, systems, and components  found in DOE nuclear facilities  are made  from many  different types  of  materials.   Many of the  materials  are  alloys  with  a base metal  of iron,  nickel, or  zirconium.   The  selection of  a  material for  a  specific application  is based on many factors including the temperature and pressure that the material will be exposed to, the materials resistance to specific types of corrosion, the materials toughness and hardness, and other material properties. One material that has wide application in the systems of DOE facilities is stainless steel.  There are nearly 40 standard types of stainless steel and many other specialized types under various trade names.  Through the modification of the kinds and quantities of alloying elements, the steel can be adapted to specific applications.   Stainless steels are classified as austenitic or ferritic based on their lattice structure.  Austenitic stainless steels, including 304 and 316, have a face- centered  cubic  structure  of  iron  atoms  with  the  carbon  in  interstitial  solid  solution.   Ferritic stainless steels, including type 405, have a body-centered cubic iron lattice and contain no nickel. Ferritic  steels  are  easier  to  weld  and  fabricate  and  are  less  susceptible  to  stress  corrosion cracking than austenitic stainless steels.   They have only moderate resistance to other types of chemical attack. Other  metals  that  have  specific  applications  in  some  DOE  nuclear  facilities  are  inconel  and zircaloy.    The  composition  of  these  metals  and  various  types  of  stainless  steel  are  listed  in Table 2 below. %Fe %C Max %Cr %Ni %Mo %Mn Max %Si Max %Zr 304 Stainless Steel Bal. 0.08 19 10 2 1 304L Stainless Steel   Bal. 0.03 18 8 2 1 316 Stainless Steel Bal. 0.08 17 12 2.5 2 1 316L Stainless Steel   Bal. 0.03 17 12 2.5 2 405 Stainless Steel Bal. 0.08 13 1 1 Inconel 8 0.15 15 Bal. 1 0.5 Zircaloy-4 0.21 0.1 Bal. MS-01 Page 16 Rev. 0