Neutron embrittlement, sometimes more broadly radiation embrittlement, is the embrittlement of various materials due to the action of neutrons. This is primarily seen in nuclear reactors, where the release of high-energy neutrons causes the long-term degradation of the reactor materials. The embrittlement is caused by the microscopic movement of atoms that are hit by the neutrons; this same action also gives rise to neutron-induced swelling causing materials to grow in size, and the Wigner effect causing energy buildup in certain materials that can lead to sudden releases of energy.
Diffusion of major defects, which leads to higher amounts of solute diffusion, as well as formation of nanoscale defect-solute cluster complexes, solute clusters, and distinct phases.[1]
Embrittlement in Nuclear Reactorsedit
Neutron irradiation embrittlement limits the service life of reactor-pressure vessels (RPV) in nuclear power plants due to the degradation of reactor materials. In order to perform at high efficiency and safely contain coolant water at temperatures around 290°C and pressures of ~7 MPa (for boiling water reactors) to 14 MPa (for pressurized water reactors), the RPV must be heavy-section steel. Due to regulations, RPV failure probabilities must be very low. To achieve sufficient safety, the design of the reactor assumes large cracks and extreme loading conditions. Under such conditions, a probable failure mode is rapid, catastrophic fracture if the vessel steel is brittle. Tough RPV base metals that are typically used are A302B, A533B plates, or A508 forgings; these are quenched and tempered, low-alloy steels with primarily tempered bainitic microstructures. Over the past few decades, RPV embrittlement has been addressed by the use of tougher steels with lower trace impurity contents, the decrease of neutron flux that the vessel is subject to, and the elimination of beltline welds. However, embrittlement remains an issue for older reactors.[2]
Pressurized water reactors are more susceptible to embrittlement than boiling water reactors. This is due to PWRs sustaining more neutron impacts. To counteract this, many PWRs have a specific core design that reduces the number of neutrons hitting the vessel wall. Moreover, PWR designs must be especially mindful of embrittlement because of pressurized thermal shock, an accident scenario that occurs when cold water enters a pressurized reactor vessel, introducing large thermal stress. This thermal stress may cause fracture if the reactor vessel is sufficiently brittle.[3]
neutron, embrittlement, sometimes, more, broadly, radiation, embrittlement, embrittlement, various, materials, action, neutrons, this, primarily, seen, nuclear, reactors, where, release, high, energy, neutrons, causes, long, term, degradation, reactor, materia. Neutron embrittlement sometimes more broadly radiation embrittlement is the embrittlement of various materials due to the action of neutrons This is primarily seen in nuclear reactors where the release of high energy neutrons causes the long term degradation of the reactor materials The embrittlement is caused by the microscopic movement of atoms that are hit by the neutrons this same action also gives rise to neutron induced swelling causing materials to grow in size and the Wigner effect causing energy buildup in certain materials that can lead to sudden releases of energy Neutron embrittlement mechanisms include Hardening and dislocation pinning due to nanometer features created by irradiation Generation of lattice defects in collision cascades via the high energy recoil atoms produced in the process of neutron scattering Diffusion of major defects which leads to higher amounts of solute diffusion as well as formation of nanoscale defect solute cluster complexes solute clusters and distinct phases 1 Embrittlement in Nuclear Reactors editNeutron irradiation embrittlement limits the service life of reactor pressure vessels RPV in nuclear power plants due to the degradation of reactor materials In order to perform at high efficiency and safely contain coolant water at temperatures around 290 C and pressures of 7 MPa for boiling water reactors to 14 MPa for pressurized water reactors the RPV must be heavy section steel Due to regulations RPV failure probabilities must be very low To achieve sufficient safety the design of the reactor assumes large cracks and extreme loading conditions Under such conditions a probable failure mode is rapid catastrophic fracture if the vessel steel is brittle Tough RPV base metals that are typically used are A302B A533B plates or A508 forgings these are quenched and tempered low alloy steels with primarily tempered bainitic microstructures Over the past few decades RPV embrittlement has been addressed by the use of tougher steels with lower trace impurity contents the decrease of neutron flux that the vessel is subject to and the elimination of beltline welds However embrittlement remains an issue for older reactors 2 Pressurized water reactors are more susceptible to embrittlement than boiling water reactors This is due to PWRs sustaining more neutron impacts To counteract this many PWRs have a specific core design that reduces the number of neutrons hitting the vessel wall Moreover PWR designs must be especially mindful of embrittlement because of pressurized thermal shock an accident scenario that occurs when cold water enters a pressurized reactor vessel introducing large thermal stress This thermal stress may cause fracture if the reactor vessel is sufficiently brittle 3 See also editRadiation damageReferences edit Backgrounder on Reactor Pressure Vessel Issues Nuclear Regulatory Commission February 2016 Pu Jue 18 March 2013 Radiation Embrittlement Stanford University Specific Embrittlement of Nuclear Reactor Pressure Vessels www tms org Retrieved 2018 03 02 Odette G R Lucas G E 2001 07 01 Embrittlement of nuclear reactor pressure vessels JOM 53 7 18 22 Bibcode 2001JOM 53g 18O doi 10 1007 s11837 001 0081 0 ISSN 1047 4838 S2CID 138790714 Backgrounder on Reactor Pressure Vessel Issues United States Nuclear Regulatory Commission April 8 2016 Retrieved March 1 2018 nbsp This nuclear physics or atomic physics related article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Neutron embrittlement amp oldid 1209018480, wikipedia, wiki, book, books, library,
