Nuclear reactor structural materials

Schulson, E.M. (1994) A potential nuclear reactor structural material. In Intermetallic Compounds Principles and Practice, eds. Westbrook, J.H. and Fleischer, R.L. (J. Wiley Sons Ltd, Chichester, England), Vol. 2, p. 133. 

Another application of sintered oxides is in nuclear reactors—uranium oxide is used as a nuclear reactor fuel material. A large fraction of uranium atoms can be fissioned without degradation of the structure. Other oxides that are used in pure form after sintering are BeO, MgO, Th02, Zr02, and MgAl204. 

Structural materials for fission reactors (as well as for future fusion reactors) are being exposed to intense neutron flux for many years. In the case of fusion reactor, 14-MeV neutrons, produced by the fusion reaction of d + t He + n, induce nuclear reactions of... 

Graphite is chosen for use in nuclear reactors because it is the most readily available material with good moderating properties and a low neutron capture cross section. Other features that make its use widespread are its low cost, stability at elevated temperatures in atmospheres free of oxygen and water vapor, good heat transfer characteristics, good mechanical and structural properties, and excellent machinability. 

With the development of nuclear reactors, giving strong beams of thermal neutrons, crystal structures can now be studied by neutron diffraction, with which the location of the hydrogen atoms is greatly improved. Indeed it is the actual proton which is located for neutrons are scattered by the atomic nuclei, not by the electron density. Since it enables us to locate the proton in A-H B, neutron diffraction is proving of special importance in the study of hydrogen bonds. Deuterons are more powerful neutron-scatterers than protons it is usually advantageous to work with deuteriated materials if possible. 

Although Pb styphnate was the material most impact-sensitive in the KIWI—TNT test, the fact that the second sample on the support structure survived the excursion raised doubt that the detonation was caused by blast or impact. Further evidence supporting this view was obtained whenVl. 8 gram sample of Pb styphnate detonated after only two minutes of irradiation in a steady-state nuclear reactor (GETR)... 

Because of its low neutron absorption, zirconium is an attractive structural material and fuel cladding for nuclear power reactors, but it has low strength and highly variable corrosion behavior. However, Zircalloy-2, with a nominal composition of 1.5 wt % tin, 0.12 wt % iron, 0.05 wt % nickel, 0.10 wt % chromium, and the remainder zirconium, can be used in all nuclear power reactors that employ pressurized water as coolant and moderator (see... 

The optical anisotropy observed in most carbon materials reflects the ordered stacking of graphite-like microcrystalline units that has been recognized to be essential in determining their properties. Pitch-based carbon fiber, electrode and metallurgical cokes, and carbons for nuclear reactors are characterized by their anisotropic texture since this structural factor is fundamentally related to their mechanical, thermal, electronic, and chemical properties (1-5) ... 

The fission neutrons at birth have energies of approximately 1 to 2 MeV In a thermal reactor the neutron energy is rapidly reduced through collisions with light nuclei to thermal (—.02 to 1 eV), to promote for more efficient capture. Besides the nuclear fuel, there are many other materials in the reactor core also competing for the neutrons, including the moderator (the material used to slow down or thermalize the neutrons), fertile nuclides that produce additional fissile material (discussed in a later section), neutron poisons present in control rods, the coolant, fuel element cladding, and other structural materials. 

OH radical could be the most important oxidizing species that is assumed to be closely related to the corrosion of the structural materials in nuclear reactors. The studies of the reactions of OH radical at elevated temperatures or supercritical water are thus essential. 

Tritium, H, is produced in nuclear reactors from the various neutron activation reactions of H, Li and impurities in structural materials. 

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