Principle of Zr radiation resistance

[wulianlian]

I am a graduate student specialising in Nuclear Material. Could somebody give me some suggestions on the principle of high Radiation Resistance of Zirconium from the viewpoint of an expert?

Thanks!

 

[Astronuc]

I am a graduate student specialising in Nuclear Material. Could somebody give me some suggestions on the principle of high Radiation Resistance of Zirconium from the viewpoint of an expert?

Thanks!

What does one mean by high radiation resistance of zirconium?

Like any material, zirconium undergoes irradation damage in the lattice. Radiation produces dislocations in the microstructure, and under typical environmental conditions, zirconium allows experience creep and growth. Normally, Zr alloys are used at temperatures below about 350°C, or less than 0.3 of T_melt.

Zirconium is an hcp metal, so fabricated products have a texture, and the creep and growth are anisotropic. The texture can be tailored according to the mechanical and thermal treatments during manufacture.

Zirconium is typically used in an alloy form - often a dilute alloy contain varying levels of Sn, Nb, Fe, Cr, Ni, and a few others. Impurities are kept quite low - preferably in low ppm range.

One must also consider the irradiation environment. Most zirconium alloys are used in LWRs and CANDUs. The outer surface of cladding tubes (and endplugs) and the surfaces of spacer grids are exposed to high temperature water (and various cations = corrosion products). So waterside corrosion is a concern with respect to operating lifetime and safety. A consequence of corrosion in an aqueous environment is hydrogen pickup whereby some hydrogen from the reaction Zr + 2 H₂O => ZrO₂ + 2H₂ is absorbed into the Zr matrix where it forms ZrH_x, where x varies locally according to the bulk H content. Zr hydrides embrittle Zr alloys, so the corrosion (oxidation) and hydrogen pickup must be limited.


The best sources of information on Zr and alloy technology are found in the ASTM STPs containing the proceedings of Zirconium in the Nuclear Industry: --th International Symposium

 

[rmattila]

I think the question might be about the low neutron capture rate at Zr, compared to some other structural materials? This is due to the fact - which ultimately is based on the quantum-mechanical properties of Zr nuclei - that the neutron reaction cross sections of Zr nuclei are small, i.e. they do not capture neutrons passing-by as eagerly as e.g. iron tends to.

 

[wizwom]

Zircalloy is used because it enhances (or at least does not detract) from moderation. As you note, the very low absorption cross section is unusual; this is because Zr90 is on the N=50 stability line.

 

[alphy]

I am happy to provide some suggestions on the principle of high radiation resistance of zirconium. Zirconium is known for its high radiation resistance, which is due to its unique atomic structure and properties.

Firstly, zirconium has a high melting point of 1855°C, which makes it suitable for use in high-temperature environments such as nuclear reactors. This high melting point is due to the strong bonds between zirconium atoms, which can withstand the disruptive effects of radiation.

Secondly, zirconium has a low neutron cross-section, meaning that it does not easily absorb neutrons, which are a type of ionizing radiation. This is important in nuclear reactors, as the absorption of neutrons can lead to the formation of radioactive isotopes and potential damage to the reactor.

Furthermore, zirconium has a high corrosion resistance, which is crucial for its use in nuclear reactors where it is exposed to harsh environments. This is due to the formation of a protective oxide layer on the surface of zirconium when exposed to air or water. This oxide layer acts as a barrier, preventing the penetration of radiation and other corrosive elements.

In addition, zirconium has a high ductility, allowing it to deform and absorb the effects of radiation without fracturing. This is important in nuclear materials, as it allows for the safe handling and processing of zirconium-based materials.

Overall, the high radiation resistance of zirconium can be attributed to its strong atomic bonds, low neutron cross-section, high corrosion resistance, and ductility. These properties make it a valuable material for use in nuclear reactors, where it can withstand the effects of radiation and maintain its structural integrity. I hope this information is helpful in your studies.