Structure of Metals
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
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.
304 Stainless Steel
304L Stainless Steel Bal.
316 Stainless Steel
316L Stainless Steel Bal.
405 Stainless Steel