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..