Hydrogen Embrittlement
As defined by a few research articles, hydrogen embrittlement is the polymerization of hydrogen dissolved in steel (or other items) into hydrogen molecules, causing stress concentrations that exceed the strength limitations of the steel, resulting in tiny cracks in said steel. once embrittlement has occurred, it cannot be reversed.
This phenomenon can lead to hydrogen leaking, and deterioration to the performance of steel materials. However, it is not only limited to steel: iron, nickel, titanium, cobalt, and alloys are all susceptible (Side note, copper, aluminum, and stainless steels are less susceptible)
Embrittlement can come from a variety of sources, such as during manufacturing or due to poor techniques. of example, poor arc welding practices resulting in the release of hydrogen can result in hydrogen embrittlement. Otherwise, it can also occur from hydrogen sulfide, resulting in sulfide stress cracking, a problem in the oil & gas industry.
This is mainly affected by
- hydrogen concentration
- ambient pressure
- temperature
- exposure time
- stress state
- mechanical properties
- microstructure
- surface conditions
- nature of material crack front
Hydrogen embrittlement is closely linked to claddingCladdingCladding is the thin walled metal tube that composes the outside of a fuel rod. It's purpose is to prevent corrosion of the fuel by the coolant & release of fission contents into the coolant. Although Zirconium alloy is common, aluminum and stainless steel is also used. Cladding Types Zirconium alloy has been used for so long due to it's properties being very good for nuclear reactors. * New research suggests that there is an alternative - SiGA cladding. This cladding is made from silicon car in nuclear reactors, such as BWR reactorBWR reactorA boiling water reactor uses Light Water as both coolant and neutron moderator. The second most used reactor, next to the PWR reactors, there are approximately 75 plants in current operation. The efficiency of these reactors is about 46%, with 33-34% in practice. Enriched uranium is used as nuclear fuel, as light water absorbs too many neutrons to use Uranium that is natural. Light water is not as good of a moderator compared to Heavy Water or graphite, but it is good as in the event of a LOCA os and RBMK ReactorRBMK Reactor\#stub It is a soviet designed nuclear reactor that uses enriched uranium, with graphite as a moderator, and Light Water as a coolant.s, alongside PWR reactorPWR reactorThis reactor is a PWR reactor - a pressurized water reactor. This is a specific type of Nuclear Reactor--in that it is pressurized water. This is also the most common type of reactor used and produced. The fuel rods are pressurized with helium, and the fission gas products result in more stability; as fuel "burns" in the reactor, the density increases resulting in small voids developing. Helium pressurization is necessary as these voids can cause potential rupture of fuel rods. Furthermore, thes as the hydrogen from zirconium alloy touching water can result in hydrogen embrittlement weakening the fuel rod structure and damaging the protective layer the zirconium alloy is meant for.