High Performance Materials for Nuclear Applications
Today’s nuclear reactors are old. They require long storage time
for spent radioactive reactor fuel. In addition, extension of life for an additional
twenty years will be expensive.
Generation IV nuclear reactors are in the concept stage of
design. These nuclear reactors would have advantage over existing nuclear
reactors in many aspects. One concept is the design of a reactor that can be
constructed and placed on a flat bed for transport to remote sites or sites requiring
less space and less isolation. These lighter weight, more efficient, safer
reactors would make it possible to establish the reactor at sites such as a
waste water area, where the water could be purified for public consumption, and generate electricity for additional usage. Similarly these
transportable reactors could be small enough and safe to power large industrial
plants, building complexes and even small cities, if coupled with additional
similar reactors to supply the required capacity. In addition, the energy
produced is clean, could possibly be used to produce clean fuels, and could
reduce or eliminate fossil fuels that currently pollute the atmosphere..
To render
these smaller reactors cost effective and safe; these reactors must operate at
higher temperatures . Estimated temperature required for the
short term is 8500C and ultimately 10000C..Higher
operating temperatures cause problems because current alloys are not capable
of resisting corrosion, and approach limits of functional capability at these
temperatures. In addition any material selected must comply with ASME Boiler
and Pressure Vessel Code Section III Division V.
Inconel 617 is one of the alloys of
interest because it can satisfy high temperature mechanical properties and be
accepted within the confines of the Code. Actually it could serve as components
of pumps used to remove heat generated by the reactor, and also in DRECS
that serve as reservoirs for storage of
the salt, if the alloy had improved surface protection against harsh corrosive
environments, such as molten salts, which are being considered as coolants. Therefore a coating resistant
to the corrosive liquid salts or coolant specified is a must. Thin coatings are
available but are not being considered as a solution to the corrosion problem
because they have been found to peel, spall, debind and scratch over the
service life of the part. Therefore, coatings greater than 0.635 mm are being
considered to provide the required elevated temperature corrosion resistance.
MagnaTech has developed a process that provides protective
surfaces that resists abrasion, impact and also provides excellent corrosion
resistance from salt water. Surfaces
were produced to protect stainless steel and low alloy steels to combat
the conditions required of shoes of hook points of F-35 aircraft. There was no
spalling, peeling, or debinding that
resulted from the various impact or abrasion tests administered to the surface
modified alloys. This was because the process is one that deposits atoms of
carbon and/or nitrogen on the activated surface of the substrate to react with
elements alloyed within the surface of the steel to form stable
carbides and nitrides that provides surfaces that have no interface with the steel
matrix. In addition, surface grain boundaries consist of stable carbides and/or
nitrides that prevent grain boundary sensitization, resulting in improved corrosion
resistance of the alloy, in this case resistance to salt water. MagnaTech
believes that the same mechanisms used for the application intended could be
used to provide the required surface resistance from the high temperature
corrodants transported in pumps to cool
the reactor and in DRECS used to store the coolant , probably liquid salt
solutions.
Markets will not be established until the early 2020 s. If developed a huge market for this clean, transportable energy source will rapidly emerge..
