spore: profile
id: zirconium-alloys
spore_version: 0.2
family: refractory-metals
name: Zirconium alloys (Zircaloy, ZIRLO, Zr-2.5Nb, Zr-Al)
abbreviation: Zr alloys
role: corrosion-resistant structural alloys for nuclear fuel cladding, reactor pressure tubes and chemical-process equipment
category: metals
type: refractory-metals
summary: |
  Zirconium alloys add small amounts of tin, iron, chromium, nickel or niobium to zirconium. The grades that matter most are Zircaloy-2 and Zircaloy-4 (fuel cladding in water reactors), Zr-2.5Nb (pressure tubes in CANDU reactors), and ZIRLO (Westinghouse cladding). In the ATI reactor-grade sheet, Zircaloy-4 has a density of 6.55 g/cc, a melting point of 1850 degC and a thermal conductivity of 21.5 W/m-K, and its annealed 2 mm strip has a room-temperature tensile strength of 541 MPa in the longitudinal direction. The corrosion table prints 0.36 mm/a for Zircaloy-4 in 70 % hydrochloric acid at 160 degC. A research alloy, ZrAl14Ti3, reaches 888 MPa offset yield strength at room temperature in one open-access paper, but no commercial Zr-Al grade was found.
best_for: Nuclear fuel cladding and reactor pressure tubes, where low thermal neutron absorption (0.22 barns for Zircaloy-4) and corrosion resistance in water and steam both matter (ATI reactor-grade sheet)
weakest_at: 'Hydride embrittlement: hydrogen from water oxidation forms hydrides that blister and crack the cladding (Wikipedia), and hot hydrochloric acid still attacks Zircaloy-4 at 0.36 mm/a'
identity:
  formula: 'Zr-based alloys. Nominal Zircaloy-4 is Zr-1.5Sn-0.2Fe-0.1Cr (wt %). Zircaloy-2: Zr with Sn 1.20 to 1.70, Fe 0.07 to 0.20, Cr 0.05 to 0.15, Ni 0.03 to 0.08 wt %. Zircaloy-4: Zr with Sn 1.20 to 1.70, Fe 0.18 to 0.24, Cr 0.07 to 0.13 wt %. Zr-2.5Nb: Zr with Nb 2.40 to 2.80 wt %. ZIRLO: Zr with Nb about 1 and Sn 0.7 to 1 wt % (Wikipedia alloy table; iron level not given there). Zr-Al: research alloys ZrAl14Ti3 and ZrAl14Ti9 (at. %), not a commercial composition.'
  source: ati-reactor-grade
  where: Composition (weight percent) table, columns Zircaloy-2, Zircaloy-4 and Zr-2.5Nb; ZIRLO from the Wikipedia alloy table; Zr-Al from the PMC paper title and abstract
  designations:
    - system: UNS
      code: R60802
      source: ati-reactor-grade
      where: Composition table, UNS Grade column, Zircaloy-2
    - system: UNS
      code: R60804
      source: ati-reactor-grade
      where: Composition table, UNS Grade column, Zircaloy-4
    - system: UNS
      code: R60904
      source: ati-reactor-grade
      where: Composition table, UNS Grade column, Zr-2.5Nb
    - system: Trade name
      code: Zircaloy-2
      source: ati-reactor-grade
      where: Zirconium alloys text, Zircaloy-2 paragraph
    - system: Trade name
      code: Zircaloy-4
      source: ati-reactor-grade
      where: Zirconium alloys text, Zircaloy-4 paragraph
    - system: Trade name
      code: ZIRLO
      source: wikipedia-zr-alloys
      where: Alloy table, ZIRLO row (Westinghouse; name stands for zirconium low oxidation)
tags:
  environments: []
  stresses:
    - corrosion
  applications:
    - structures
    - thermal-control
properties:
  - benchmark: density
    label: Density, Zircaloy-4
    value: 6.55
    unit: g/cc
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      temperature: not stated
      unit_in_source: 6.55 g/cc (0.237 lbs/cu.-in.)
    method: Value printed in the ATI reactor-grade zirconium data sheet, Properties of Zircaloy-4 table
    status: ground
    source: ati-reactor-grade
    where: Properties of Zircaloy-4 table, row Density
  - benchmark: melting_point
    label: Melting point, Zircaloy-4
    value: 1850
    unit: °C
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      unit_in_source: 1850 °C (3,362 °F)
    method: Value printed in the ATI reactor-grade zirconium data sheet
    status: ground
    source: ati-reactor-grade
    where: Properties of Zircaloy-4 table, row Melting Point
  - benchmark: thermal_conductivity
    label: Thermal conductivity, Zircaloy-4
    value: 21.5
    unit: W/m-K
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      temperature: not stated
      unit_in_source: 21.5 Watts/m-K (149 BTU-in/hr-ft2-F)
    method: Value printed in the ATI reactor-grade zirconium data sheet
    status: ground
    source: ati-reactor-grade
    where: Properties of Zircaloy-4 table, row Thermal Conductivity
  - benchmark: specific_heat
    label: Heat capacity, Zircaloy-4
    value: 0.285
    unit: J/g-°C
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      temperature: not stated
      unit_in_source: 0.285 J/g-°C (0.07 BTU/lb-°C)
    method: Value printed in the ATI reactor-grade zirconium data sheet; the table calls it heat capacity
    status: ground
    source: ati-reactor-grade
    where: Properties of Zircaloy-4 table, row Heat Capacity
  - benchmark: cte
    label: Coefficient of thermal expansion, Zircaloy-4 at 25 degC
    value: 6
    unit: µm/(m·°C)
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      temperature: 25 °C
      unit_in_source: 6 µm/m °C (3.3 µin/in-°F)
    method: Value printed in the ATI reactor-grade zirconium data sheet
    status: ground
    source: ati-reactor-grade
    where: Properties of Zircaloy-4 table, row Coefficient of Thermal Expansion at 25 C
  - benchmark: elastic_modulus
    label: Modulus of elasticity, Zircaloy-4
    value: 99.3
    unit: GPa
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      temperature: not stated
      unit_in_source: 99.3 Gpa (14,402 ksi)
    method: Value printed in the ATI reactor-grade zirconium data sheet
    status: ground
    source: ati-reactor-grade
    where: Properties of Zircaloy-4 table, row Modulus of Elasticity
  - benchmark: shear_modulus
    label: Shear modulus, Zircaloy-4
    value: 36.2
    unit: GPa
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      temperature: not stated
      unit_in_source: 36.2 Gpa (5,249 ksi)
    method: Value printed in the ATI reactor-grade zirconium data sheet
    status: ground
    source: ati-reactor-grade
    where: Properties of Zircaloy-4 table, row Shear Modulus
  - benchmark: poissons_ratio
    label: Poisson's ratio, Zircaloy-4
    value: 0.37
    unit: '-'
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      temperature: not stated
    method: Value printed in the ATI reactor-grade zirconium data sheet
    status: ground
    source: ati-reactor-grade
    where: Properties of Zircaloy-4 table, row Poisson's Ratio
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, Zircaloy-4 longitudinal, room temperature
    value: 541
    unit: MPa
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      temper: annealed 2 mm thick strip
      orientation: longitudinal
      temperature: room temperature
      unit_in_source: 541 MPa (78.4 ksi)
    method: Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table
    status: ground
    source: ati-reactor-grade
    where: Mechanical properties of Zircaloy-4 annealed 2 mm thick strip table, row Ultimate Tensile Strength, Longitudinal, Room Temp
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, Zircaloy-4 transverse, room temperature
    value: 515
    unit: MPa
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      temper: annealed 2 mm thick strip
      orientation: transverse
      temperature: room temperature
      unit_in_source: 515 MPa (74.6 ksi)
    method: Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table
    status: ground
    source: ati-reactor-grade
    where: Mechanical properties of Zircaloy-4 annealed 2 mm thick strip table, row Ultimate Tensile Strength, Transverse, Room Temp
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, Zircaloy-4 longitudinal, 288 degC
    value: 271
    unit: MPa
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      temper: annealed 2 mm thick strip
      orientation: longitudinal
      temperature: 288 °C
      unit_in_source: 271 MPa (39.3 ksi)
    method: Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table
    status: ground
    source: ati-reactor-grade
    where: Mechanical properties of Zircaloy-4 annealed 2 mm thick strip table, row Ultimate Tensile Strength, Longitudinal, 288 C column
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, Zircaloy-4 transverse, 288 degC
    value: 241
    unit: MPa
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      temper: annealed 2 mm thick strip
      orientation: transverse
      temperature: 288 °C
      unit_in_source: 241 MPa (34.9 ksi)
    method: Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table
    status: ground
    source: ati-reactor-grade
    where: Mechanical properties of Zircaloy-4 annealed 2 mm thick strip table, row Ultimate Tensile Strength, Transverse, 288 C column
  - benchmark: yield_strength
    label: Yield strength, Zircaloy-4 transverse, room temperature
    value: 468
    unit: MPa
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      temper: annealed 2 mm thick strip
      orientation: transverse
      temperature: room temperature
      unit_in_source: 468 MPa (67.8 ksi)
    method: Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table; the longitudinal yield in the same table (80 MPa) is not used, see gaps
    status: ground
    source: ati-reactor-grade
    where: Mechanical properties of Zircaloy-4 annealed 2 mm thick strip table, row Yield Strength, Transverse, Room Temp
  - benchmark: yield_strength
    label: Yield strength, Zircaloy-4 transverse, 288 degC
    value: 170
    unit: MPa
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      temper: annealed 2 mm thick strip
      orientation: transverse
      temperature: 288 °C
      unit_in_source: 170 MPa (25.6 ksi)
    method: Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table
    status: ground
    source: ati-reactor-grade
    where: Mechanical properties of Zircaloy-4 annealed 2 mm thick strip table, row Yield Strength, Transverse, 288 C column
  - benchmark: elongation
    label: Elongation, Zircaloy-4 longitudinal, room temperature
    value: 28
    unit: '%'
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      temper: annealed 2 mm thick strip
      orientation: longitudinal
      temperature: room temperature
    method: Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table
    status: ground
    source: ati-reactor-grade
    where: Mechanical properties of Zircaloy-4 annealed 2 mm thick strip table, row Elongation, Longitudinal, Room Temp
  - benchmark: elongation
    label: Elongation, Zircaloy-4 transverse, room temperature
    value: 29
    unit: '%'
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      temper: annealed 2 mm thick strip
      orientation: transverse
      temperature: room temperature
    method: Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table
    status: ground
    source: ati-reactor-grade
    where: Mechanical properties of Zircaloy-4 annealed 2 mm thick strip table, row Elongation, Transverse, Room Temp
  - benchmark: thermal_neutron_cross_section
    label: Thermal neutron cross section, Zircaloy-4
    value: 0.22
    unit: barns
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      neutron: thermal
      unit_in_source: 0.22 barns
    method: Value printed in the ATI reactor-grade zirconium data sheet, thermal neutron cross sections table; the name is not in spores/property-canon.yaml, see gaps
    status: ground
    source: ati-reactor-grade
    where: Thermal neutron cross sections (barns) table, row Zircaloy-4
  - benchmark: thermal_neutron_cross_section
    label: Thermal neutron cross section, zirconium
    value: 0.18
    unit: barns
    scope: material
    conditions:
      form: zirconium element
      neutron: thermal
      unit_in_source: 0.18 barns
    method: Value printed in the ATI reactor-grade zirconium data sheet, thermal neutron cross sections table
    status: ground
    source: ati-reactor-grade
    where: Thermal neutron cross sections (barns) table, row Zirconium
  - benchmark: alpha_beta_transition_temperature
    label: Alpha to alpha plus beta transformation, Zircaloy-4
    value: 810
    unit: °C
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      note: beta phase starts to form on heating
    method: Value printed in the ATI reactor-grade zirconium data sheet; non-canonical name, see gaps
    status: ground
    source: ati-reactor-grade
    where: Properties of Zircaloy-4 table, row Alpha to Alpha + Beta Phase Transformation; text on crystal structure
  - benchmark: alpha_beta_transition_temperature
    label: Alpha plus beta to beta transformation, Zircaloy-4
    value: 980
    unit: °C
    scope: material
    conditions:
      grade: Zircaloy-4 (UNS R60804)
      note: transformation to full beta phase
    method: Value printed in the ATI reactor-grade zirconium data sheet; non-canonical name, see gaps
    status: ground
    source: ati-reactor-grade
    where: Properties of Zircaloy-4 table, row Alpha + Beta to Beta Phase Transformation
  - benchmark: yield_strength
    label: Offset yield strength, ZrAl14Ti3 (research alloy)
    value: 888
    unit: MPa
    scope: material
    conditions:
      alloy: ZrAl14Ti3 (at. %), hot-rolled and quenched
      temperature: room temperature
      measure: offset yield, as printed in the abstract
      scatter: plus or minus 12 MPa
    method: Value printed in the abstract of the open-access PMC paper; research alloy, not a commercial grade
    status: ground
    source: pmc-zral
    where: Abstract, sentence beginning Mechanical property evaluation showed
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, ZrAl14Ti3 (research alloy)
    value: 1056
    unit: MPa
    scope: material
    conditions:
      alloy: ZrAl14Ti3 (at. %), hot-rolled and quenched
      temperature: room temperature
      scatter: plus or minus 19 MPa
    method: Value printed in the abstract of the open-access PMC paper
    status: ground
    source: pmc-zral
    where: Abstract, sentence beginning Mechanical property evaluation showed
  - benchmark: elongation
    label: Fracture elongation, ZrAl14Ti3 (research alloy)
    value: 23
    unit: '%'
    scope: material
    conditions:
      alloy: ZrAl14Ti3 (at. %), hot-rolled and quenched
      temperature: room temperature
      scatter: plus or minus 1 %
    method: Value printed in the abstract of the open-access PMC paper
    status: ground
    source: pmc-zral
    where: Abstract, sentence beginning Mechanical property evaluation showed
  - benchmark: yield_strength
    label: Offset yield strength, ZrAl14Ti9 (research alloy)
    value: 998
    unit: MPa
    scope: material
    conditions:
      alloy: ZrAl14Ti9 (at. %), hot-rolled and quenched
      temperature: room temperature
      measure: offset yield
      scatter: plus or minus 6 MPa
    method: Value printed in the abstract of the open-access PMC paper
    status: ground
    note: The paper says this is 110 MPa above ZrAl14Ti3 at the same condition.
    source: pmc-zral
    where: Abstract, sentence beginning The ZrAl14Ti9 alloy displayed
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, ZrAl14Ti9 (research alloy)
    value: 1069
    unit: MPa
    scope: material
    conditions:
      alloy: ZrAl14Ti9 (at. %), hot-rolled and quenched
      temperature: room temperature
      scatter: plus or minus 7 MPa
    method: Value printed in the main text of the open-access PMC paper, comparison paragraph with ZrAl14Ti3
    status: ground
    source: pmc-zral
    where: Main text, paragraph beginning Compared with ZrAl14Ti3 (results and discussion)
  - benchmark: elongation
    label: Fracture elongation, ZrAl14Ti9 (research alloy)
    value: 23
    unit: '%'
    scope: material
    conditions:
      alloy: ZrAl14Ti9 (at. %), hot-rolled and quenched
      temperature: room temperature
      scatter: plus or minus 2 %
    method: Value printed in the abstract of the open-access PMC paper
    status: ground
    source: pmc-zral
    where: Abstract, sentence beginning The ZrAl14Ti9 alloy displayed
corrosion:
  - environment: Hydrochloric acid, 70 %, 160 °C (Zircaloy-4)
    headline: Hot concentrated hydrochloric acid attacks Zircaloy-4 at a measurable rate.
    effect: The corrosion table prints 0.36 mm/a (14 mpy) for Zircaloy-4 in 70 % HCl at 160 °C.
    rating: moderate
    conditions:
      medium: hydrochloric acid, 70 %
      temperature: 160 °C
      unit_in_source: mm/a (MPY)
      rating_basis: 'Space Mushroom rating from the printed rate: none for nil, low below 0.1 mm/a, moderate from 0.1 mm/a'
    source: ati-reactor-grade
    where: Corrosion rate data for Zircaloy-4 table, row HCl 70 %, 160 °C
  - environment: Ferric chloride, 1 %, 135 °C (Zircaloy-4)
    headline: A small amount of ferric chloride corrodes Zircaloy-4 at 0.18 mm/a.
    effect: The table prints 0.18 mm/a (7 mpy) for Zircaloy-4 in 1 % FeCl3 at 135 °C.
    rating: moderate
    conditions:
      medium: ferric chloride, 1 %
      temperature: 135 °C
      unit_in_source: mm/a (MPY)
      rating_basis: as for the first entry
    source: ati-reactor-grade
    where: Corrosion rate data for Zircaloy-4 table, row FeCl3 1 %, 135 °C
  - environment: Sulfuric acid, 70 %, 150 °C (Zircaloy-4)
    headline: Zircaloy-4 stays under 0.13 mm/a in hot sulfuric acid.
    effect: The table prints under 0.13 mm/a (under 5 mpy).
    rating: low
    conditions:
      medium: sulfuric acid, 70 %
      temperature: 150 °C
      unit_in_source: mm/a (MPY)
    source: ati-reactor-grade
    where: Corrosion rate data for Zircaloy-4 table, row H2SO4 70 %, 150 °C
  - environment: Nitric acid, 70 %, 120 °C (Zircaloy-4)
    headline: Zircaloy-4 barely corrodes in hot 70 % nitric acid.
    effect: The table prints 0.05 mm/a (2 mpy).
    rating: low
    conditions:
      medium: nitric acid, 70 %
      temperature: 120 °C
      unit_in_source: mm/a (MPY)
    source: ati-reactor-grade
    where: Corrosion rate data for Zircaloy-4 table, row HNO3 70 %, 120 °C
  - environment: Copper chloride, 0.1 %, 144 °C (Zircaloy-4)
    headline: Dilute copper chloride gives a low rate.
    effect: The table prints 0.03 mm/a (1 mpy).
    rating: low
    conditions:
      medium: CuCl2, 0.1 %
      temperature: 144 °C
      unit_in_source: mm/a (MPY)
    source: ati-reactor-grade
    where: Corrosion rate data for Zircaloy-4 table, row CuCl2 0.1 %, 144 °C
  - environment: Sodium chloride, 25 %, 250 °C (Zircaloy-4)
    headline: Hot brine does not attack Zircaloy-4 measurably.
    effect: The table prints nil.
    rating: none
    conditions:
      medium: NaCl, 25 %
      temperature: 250 °C
      unit_in_source: nil
    source: ati-reactor-grade
    where: Corrosion rate data for Zircaloy-4 table, row NaCl 25 %, 250 °C
  - environment: Nitric, sulfuric or hydrochloric acid with ferric, cupric or nitrate ions, above the boiling point
    headline: ATI says rates stay under 0.13 mm/a for these acid-and-impurity mixtures.
    effect: The sheet says these solutions generally give corrosion rates of less than 0.13 mm/a (5 mpy) even at temperatures well above the boiling point. This is a general statement for the zirconium alloys, not a single printed test.
    rating: low
    conditions:
      basis: general statement in the zirconium alloy properties text
      unit_in_source: mm/a (mpy)
    source: ati-reactor-grade
    where: Zirconium alloy properties text, first paragraph under ZIRCONIUM ALLOY PROPERTIES
  - environment: Air or water (oxide film)
    headline: Zircaloy-2 and Zircaloy-4 oxidise at the same rate in air or water, and their protection comes from the oxide film.
    effect: Wikipedia says oxidation occurs at the same rate in air or in water, that a sub-micrometre zirconium dioxide film forms quickly, and that Zircaloys 2 and 4 behave very similarly. No rate in mm or mg per area is printed in the page.
    rating: unknown
    conditions:
      basis: Wikipedia summary; no measured rate read in this run
    source: wikipedia-zr-alloys
    where: Oxidation of zirconium alloy section
risks:
  hazards: []
  failure_risks:
    - mode: Delayed hydride cracking of Zircaloy cladding
      trigger: Hydrogen uptake, and stress raisers such as notches and cracks, during reactor cycles or spent-fuel storage of high-burnup fuel rods
      consequence: Hydride precipitation embrittles Zircaloy, and delayed hydride cracking threatens the safety and structural integrity of fuel cladding. The paper gives no rate.
      severity: high
      source: arxiv-zircaloy4
      where: Introduction, paragraph 1
    - mode: Hydrogen embrittlement of cladding
      trigger: Hydrogen released when zirconium oxidises in water diffuses into the alloy and forms hydrides
      consequence: Hydrides are less dense and weaker than the alloy, and their formation results in blistering and cracking of the cladding.
      severity: high
      source: wikipedia-zr-alloys
      where: Introduction, paragraph 1
    - mode: Acid attack in hot hydrochloric acid
      trigger: 70 % HCl at 160 °C, as in the Zircaloy-4 corrosion table
      consequence: The printed corrosion rate is 0.36 mm/a (14 mpy), so the alloy thins steadily in this service.
      severity: moderate
      source: ati-reactor-grade
      where: Corrosion rate data for Zircaloy-4 table, row HCl 70 %, 160 °C
    - mode: Directional strength of cold-rolled strip
      trigger: Cold rolling produces a strong texture in Zircaloy strip, and the crystal basal poles sit about 35 degrees to the transverse plane
      consequence: ATI says the anisotropy gives significantly higher yield strength in the transverse direction, so the strength of a strip depends on its orientation. Designers must state the direction.
      severity: moderate
      source: ati-reactor-grade
      where: Zirconium alloy text, crystal structure paragraph
  side_effects:
    - text: Reactor-grade zirconium limits hafnium to 0.010 % maximum. Hafnium has a thermal neutron cross section of 104 barns, against 0.18 barns for zirconium, so trace hafnium would absorb neutrons in the core.
      affects: Neutron economy in reactor cores
      source: ati-reactor-grade
      where: Reactor grade paragraph; Thermal neutron cross sections table; Maximum impurities table
    - text: Zirconium reacting with water releases hydrogen gas, part of which diffuses into the alloy.
      affects: Cladding structure through hydride formation
      source: wikipedia-zr-alloys
      where: Introduction, paragraph 1
  handling:
    - text: Specify the grade, since Zircaloy-2, Zircaloy-4 and Zr-2.5Nb differ in tin, iron, nickel and niobium content (ATI composition table).
      source: ati-reactor-grade
      where: Composition (weight percent) table
    - text: Keep hydrogen impurity at or below 0.0025 % in Zircaloy-2 and Zircaloy-4, and at or below 0.0010 % in Zr-2.5Nb (ATI maximum impurities table).
      source: ati-reactor-grade
      where: Maximum impurities table, row Hydrogen
    - text: 'The impurity limits are printed as maxima: Zircaloy-2 and Zircaloy-4 carbon 0.027 %, nitrogen 0.0080 %, silicon 0.0120 %; Zr-2.5Nb carbon 0.027 %, nitrogen 0.0065 % (ATI maximum impurities table).'
      source: ati-reactor-grade
      where: Maximum impurities table, rows Carbon, Nitrogen, Silicon
  mitigations:
    - text: Corrosion resistance is improved by deliberately growing a thicker, black, lustrous zirconium oxide layer (Wikipedia).
      source: wikipedia-zr-alloys
      where: Oxidation of zirconium alloy section
    - text: Keep carbon below about 40 ppm and nitrogen below about 300 ppm, because larger amounts degrade corrosion resistance significantly (Wikipedia).
      source: wikipedia-zr-alloys
      where: Oxidation of zirconium alloy section
uses:
  - application: structures
    device: Zircaloy-4 fuel cladding in pressurized water and CANDU reactors
    example: ATI says Zircaloy-4 is typically used as fuel cladding in pressurized water reactors (PWR) and CANDU reactors, with the nominal composition Zr-1.5Sn-0.2Fe-0.1Cr.
    source: ati-reactor-grade
    where: Zirconium alloys text, Zircaloy-4 paragraph
  - application: structures
    device: Zircaloy-2 fuel cladding in boiling water reactors and calandria tubing in CANDU reactors
    example: ATI says Zircaloy-2 has been predominantly used as fuel cladding in boiling water reactors (BWR) and as calandria tubing in CANDU reactors.
    source: ati-reactor-grade
    where: Zirconium alloys text, Zircaloy-2 paragraph
  - application: structures
    device: Zr-2.5Nb pressure tubes in CANDU reactors
    example: ATI says Zr-2.5Nb has been used for pressure tubes in CANDU reactors, and that niobium increases its strength.
    source: ati-reactor-grade
    where: Zirconium alloys text, Zr-2.5Nb paragraph
  - application: structures
    device: ZIRLO fuel cladding in boiling and pressurized water reactors (Westinghouse)
    example: The Wikipedia alloy table lists ZIRLO with Sn 0.7 to 1 and Nb 1 wt %, for cladding in BWR and PWR reactors, made by Westinghouse.
    source: wikipedia-zr-alloys
    where: Alloy table, ZIRLO row
supply:
  - subject: Zirconium mineral concentrates (zircon), 2025 mine production
    producers:
      - country: Australia
        share_percent: 33.3
        year: 2025
      - country: South Africa
        share_percent: 22.5
        year: 2025
      - country: Mozambique
        share_percent: 13.3
        year: 2025
      - country: China
        share_percent: 8.3
        year: 2025
      - country: United States
        share_percent: 8.3
        year: 2025
    critical_lists: []
    recycling: Companies in Oregon and Utah recycled zirconium from new scrap generated during metal production and fabrication, and from old scrap. The USGS does not quantify this recycling.
    substitutes:
      - 'USGS: niobium, stainless steel and tantalum provide some substitution in nuclear applications.'
    source: usgs-mcs2026-zirconium
    where: 'World Mine Production and Reserves table, zirconium mineral concentrates, 2025 column: Australia 400, South Africa 270, Mozambique 160, China 100, United States 100, world total 1,200 thousand t (rounded). Shares calculated by Space Mushroom as country value divided by the printed world total. Recycling and Substitutes sections.'
  - subject: Unwrought zirconium import sources, 2021 to 2024 window
    producers:
      - country: China
        share_percent: 55
        year: 2024
      - country: Germany
        share_percent: 15
        year: 2024
      - country: Canada
        share_percent: 12
        year: 2024
      - country: France
        share_percent: 7
        year: 2024
    critical_lists: []
    recycling: Not quantified in the USGS summary.
    substitutes: []
    source: usgs-mcs2026-zirconium
    where: 'Import Sources (2021-24), Zirconium unwrought: China 55 %, Germany 15 %, Canada 12 %, France 7 %. The year given is the end of the window.'
  - subject: Niobium (Zr-2.5Nb and ZIRLO alloying element), 2025 mine production
    producers:
      - country: Brazil
        share_percent: 92.9
        year: 2025
      - country: Canada
        share_percent: 5.4
        year: 2025
      - country: Congo (Kinshasa)
        share_percent: 0.9
        year: 2025
    critical_lists: []
    recycling: 'USGS: niobium recovery from scrap was negligible; the amount recycled was not available.'
    substitutes:
      - 'USGS: molybdenum, tantalum and titanium can be used as alloying elements in stainless and high-strength steels, and tantalum and tungsten in high-temperature superalloy applications; these substitutes carry a performance loss or higher cost.'
    source: usgs-mcs2026-niobium
    where: 'World Mine Production and Reserves table, mine production 2025e: Brazil 104,000, Canada 6,000, Congo (Kinshasa) 970 thousand t; world total 112,000 (rounded). Shares calculated by Space Mushroom. Recycling and Substitutes sections.'
  - subject: Tin (Zircaloy alloying element), 2025 mine production
    producers:
      - country: China
        share_percent: 24.5
        year: 2025
      - country: Indonesia
        share_percent: 21
        year: 2025
      - country: Peru
        share_percent: 11.4
        year: 2025
      - country: Brazil
        share_percent: 9.7
        year: 2025
    critical_lists: []
    recycling: 'USGS: about 17,000 tons of tin from old and new scrap was estimated recycled in 2025, 22 % of apparent consumption.'
    substitutes:
      - 'USGS: aluminum alloys, alternative copper-base alloys and plastics can substitute for tin in some uses.'
    source: usgs-mcs2026-tin
    where: 'World Mine Production and Reserves table, mine production 2025e: China 71,000, Indonesia 61,000, Peru 33,000, Brazil 28,000 thousand t; world total 290,000 (rounded). Shares calculated by Space Mushroom. Recycling and Substitutes sections.'
documents:
  - title: 'ATI Zirconium Alloys technical data sheet: Reactor Grade Zirconium (Zircaloy-2, Zircaloy-4, Zr-2.5Nb), version 1, 2015'
    type: datasheet
    url: https://www.atimaterials.com/Products/Documents/datasheets/zirconium/alloy/Zr_nuke_waste_disposal_v1.pdf
    year: 2015
  - title: Liu et al., Characterisation of microstructural creep, strain rate and temperature sensitivity and computational crystal plasticity in Zircaloy-4, arXiv:2109.05333
    type: paper
    url: https://arxiv.org/pdf/2109.05333
    year: 2021
  - title: Zirconium alloys, Wikipedia (alloy composition table, oxidation, hydrides, applications; article titled Zircaloy)
    type: database
    url: https://en.wikipedia.org/wiki/Zircaloy
    year: 2026
  - title: Zirconium, Wikipedia (Kroll process, standard atomic weight)
    type: database
    url: https://en.wikipedia.org/wiki/Zirconium
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Zirconium and Hafnium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-zirconium-hafnium.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Niobium (Columbium)'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-niobium.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Tin'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tin.pdf
    year: 2026
  - title: 'Open-access paper: Microstructure and Mechanical Properties of Hot-Rolled ZrAl14Ti3 and ZrAl14Ti9 Alloys (PMC12525182)'
    type: paper
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC12525182/
gaps:
  - No property values for Zircaloy-2, ZIRLO or Zr-2.5Nb were read in a page fetched in this run. The ATI sheet prints tensile and thermal values for Zircaloy-4 only. Open Zr-2.5Nb tensile papers (OSTI record, Springer article) returned no readable text here; search snippets are not used.
  - ZIRLO iron content is not printed in any page read in this run. The Wikipedia alloy table gives only Sn and Nb for ZIRLO, so the nominal iron level is left out.
  - Zircaloy-4 longitudinal yield strength at room temperature (80 MPa) in the ATI table sits oddly next to its 541 MPa tensile strength and looks anomalous, so it is not recorded. Only transverse and 288 degC yields are used.
  - Zr-Al values come from two research alloys (ZrAl14Ti3 and ZrAl14Ti9, at. %, hot-rolled and quenched) in one paper. No commercial Zr-Al grade, and no property range across the Zr-Al composition, was found. Patent and supplier snippets were not used.
  - Zr-Al and the commercial alloys have no hazard, SDS or GHS record read in this run, so risks.hazards is empty. The zirconium metal powder hazard is covered in the zirconium.yaml profile, not here.
  - 'Non-canonical property names used: thermal_neutron_cross_section and alpha_beta_transition_temperature. Neither is in spores/property-canon.yaml.'
  - Hardness (89 Rb for Zircaloy-4), electrical resistivity, outgassing and radiation damage were printed or searched but not recorded as values for these alloys.
  - Critical-mineral status of zirconium, tin and niobium is not stated in the USGS summaries read here, so critical_lists is empty.
  - EN, DIN and JIS designations for these grades were not found in a page read in this run. Only UNS, ASTM-style trade names and the ZIRLO trade name are listed.
  - No media is included for this profile.
  - The year of the PMC paper is not printed on the page read in this run, so the source record gives no year.
sources:
  ati-reactor-grade:
    title: 'Zirconium Alloys: Reactor Grade Zirconium, ATI Technical Data Sheet, version 1'
    id: UNS R60802 (Zircaloy-2), R60804 (Zircaloy-4), R60904 (Zr-2.5Nb)
    url: https://www.atimaterials.com/Products/Documents/datasheets/zirconium/alloy/Zr_nuke_waste_disposal_v1.pdf
    year: 2015
    kind: datasheet
    license: Manufacturer datasheet, typical data, not for specification (cited, not reproduced)
  arxiv-zircaloy4:
    title: Characterisation of microstructural creep, strain rate and temperature sensitivity and computational crystal plasticity in Zircaloy-4 (Liu et al.)
    id: arXiv:2109.05333
    url: https://arxiv.org/pdf/2109.05333
    year: 2021
    kind: paper
    license: arXiv preprint (cited, not reproduced)
  wikipedia-zr-alloys:
    title: Zirconium alloys (Wikipedia, article reached from the Zircaloy redirect)
    url: https://en.wikipedia.org/wiki/Zircaloy
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
  wikipedia-zirconium:
    title: Zirconium (Wikipedia; element, Kroll process, standard atomic weight)
    url: https://en.wikipedia.org/wiki/Zirconium
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
  usgs-mcs2026-zirconium:
    title: 'Mineral Commodity Summaries 2026: Zirconium and Hafnium (Shelby N. Johnston, U.S. Geological Survey)'
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-zirconium-hafnium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-mcs2026-niobium:
    title: 'Mineral Commodity Summaries 2026: Niobium (Columbium)'
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-niobium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-mcs2026-tin:
    title: 'Mineral Commodity Summaries 2026: Tin'
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tin.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  pmc-zral:
    title: Microstructure and Mechanical Properties of Hot-Rolled ZrAl14Ti3 and ZrAl14Ti9 Alloys (open access, PMC12525182)
    id: PMID 41095285, PMCID PMC12525182
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC12525182/
    kind: paper
    license: CC BY 4.0
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 26
  unreachable: 2
  caveats: 3
  note: 'Read by an AI assistant on 2026-10-26 from the ATI reactor-grade PDF, the arXiv PDF, the PMC paper, the Wikipedia alloy and zirconium pages, and the USGS niobium, tin and zirconium summaries. Unreachable in this run: the OSTI ZIRLO record and the Springer Zr-2.5Nb article (timeout and blocked page). Caveats: the Zircaloy-4 longitudinal yield (80 MPa) is not used; ZIRLO and Zr-2.5Nb carry no numeric properties; Zr-Al values are from research alloys.'
story:
  recipe:
    line: Zircaloys are zirconium with small additions of tin, iron, chromium and, for Zircaloy-2, nickel. Zircaloy-4 has the nominal composition Zr-1.5Sn-0.2Fe-0.1Cr (ATI; also arXiv). Zr-2.5Nb is zirconium with 2.4 to 2.8 wt % niobium. Most zirconium metal is made by reducing zirconium(IV) chloride with magnesium in the Kroll process (Wikipedia), and the alloy is then melted with its additions.
    parts:
      - name: Zirconium
        symbol: Zr
        share_percent: 95
        role: Base metal. Wikipedia says nuclear-grade zirconium alloys are more than 95 weight percent zirconium.
      - name: Tin
        symbol: Sn
        share_percent: 1.2
        share_high: 1.7
        role: Main alloying element in Zircaloy-2, Zircaloy-4 and ZIRLO; adds strength and helps corrosion resistance (ATI composition table).
      - name: Iron
        symbol: Fe
        share_percent: 0.18
        share_high: 0.24
        role: Zircaloy-4 addition; Zircaloy-2 has 0.07 to 0.20 wt % (ATI composition table).
      - name: Chromium
        symbol: Cr
        share_percent: 0.07
        share_high: 0.13
        role: Zircaloy-4 addition; Zircaloy-2 has 0.05 to 0.15 wt % (ATI composition table).
      - name: Niobium
        symbol: Nb
        share_percent: 2.4
        share_high: 2.8
        role: Zr-2.5Nb binary alloy addition for strength (ATI composition table). ZIRLO has about 1 wt % Nb (Wikipedia).
  risk_groups:
    - title: For people
      level: 0
      verdict: No hazard class found
      lead: No safety data sheet or hazard classification for these alloy grades was read in this run, so no personal hazard is stated here.
      points:
        - label: Hydrogen
          line: Zirconium reacting with water releases hydrogen gas, according to the Wikipedia alloy summary. This is a reactor and storage concern.
    - title: If it fails
      lead: These are failure routes in the sources. The cladding route is documented in a paper, the acid routes are printed table results.
      points:
        - label: Hydride cracking
          line: A Zircaloy-4 paper says hydride precipitation embrittles the alloy, and delayed hydride cracking threatens fuel cladding near notches and cracks. Wikipedia says hydrides blister and crack the cladding.
        - label: Hot acid
          line: The corrosion table prints 0.36 mm/a for Zircaloy-4 in 70 % hydrochloric acid at 160 °C, and 0.18 mm/a in 1 % ferric chloride at 135 °C.
        - label: Strip direction
          line: ATI says cold-rolled Zircaloy strip is much stronger in the transverse direction, so the orientation must be specified.
    - title: Handling and storage
      points:
        - label: Grade
          line: Specify the grade, since tin, iron, chromium, nickel and niobium levels differ between Zircaloy-2, Zircaloy-4 and Zr-2.5Nb.
        - label: Impurities
          line: Hydrogen is limited to 0.0025 % in Zircaloy-2 and Zircaloy-4, and to 0.0010 % in Zr-2.5Nb. Hafnium is limited to 0.010 %, because hafnium has a cross section of 104 barns.
  why: Zircaloy-2 and Zircaloy-4 are the workhorse fuel cladding alloys of water reactors. Zircaloy-4 has the same tin content as Zircaloy-2 but more iron and no nickel, which the ATI sheet says reduces hydrogen uptake in certain reactor conditions. Zr-2.5Nb adds niobium for strength and is used for CANDU pressure tubes. ZIRLO, a Westinghouse alloy with about 1 wt % niobium and 0.7 to 1 wt % tin, is used for cladding in boiling and pressurized water reactors. The alloys keep the low thermal neutron cross section of zirconium (0.18 barns) and its corrosion resistance, with Zircaloy-4 at 0.22 barns.
  uses:
    - where: Fuel cladding in pressurized water reactors
      line: ATI says Zircaloy-4 is typically used as fuel cladding in pressurized water reactors and CANDU reactors. Wikipedia lists Zircaloy-4 as cladding and structural components in BWR, PWR and CANDU reactors.
    - where: Cladding and calandria tubing in boiling water and CANDU reactors
      line: ATI says Zircaloy-2 has been used mainly as fuel cladding in boiling water reactors and as calandria tubing in CANDU reactors.
    - where: Pressure tubes in CANDU reactors
      line: ATI says Zr-2.5Nb has been used for CANDU pressure tubes. Wikipedia adds that a Zr-2.5Nb alloy is formed into a knee or hip implant and then oxidised to give a hard ceramic bearing surface.
    - where: ZIRLO cladding (Westinghouse)
      line: The Wikipedia alloy table lists ZIRLO as Westinghouse cladding for BWR and PWR reactors, with 0.7 to 1 wt % Sn and 1 wt % Nb.
  can_do:
    - label: Resist hot acid
      value: 0.05 mm/a
      line: Zircaloy-4 corrodes at 0.05 mm/a in 70 % nitric acid at 120 °C, and under 0.13 mm/a in 70 % sulfuric acid at 150 °C. Hydrochloric acid at 70 % and 160 °C is worse, at 0.36 mm/a.
    - label: Carry heat
      value: 21.5 W/m-K
      benchmark: thermal_conductivity
      line: Zircaloy-4 conducts heat at 21.5 W/m-K. ATI says zirconium alloys conduct heat better than stainless steel alloys.
    - label: Weight
      value: 6.55 g/cc
      benchmark: density
      line: Zircaloy-4 has a density of 6.55 g/cc, and the ATI sheet gives its melting point as 1850 °C.
    - label: Tensile strength
      value: 541 MPa
      benchmark: ultimate_tensile_strength
      line: Annealed Zircaloy-4 strip has a room-temperature tensile strength of 541 MPa longitudinally and 515 MPa transversely. At 288 °C the longitudinal value falls to 271 MPa.
    - label: Research alloy strength
      value: 888 MPa
      benchmark: yield_strength
      line: In one open-access paper, the research alloy ZrAl14Ti3 reached an offset yield strength of 888 MPa, and ZrAl14Ti9 reached 998 MPa, with about 23 % fracture elongation for both. These are research alloys with no commercial grade.
  compare: 'Zircaloy-4 has a thermal neutron cross section of 0.22 barns, against 0.18 barns for pure zirconium, and a thermal conductivity of 21.5 W/m-K. Zr-Al is a different class: the research alloys reach about 888 to 1069 MPa at room temperature, far above the 541 MPa annealed Zircaloy-4 strip, but no corrosion or thermal data were found for them. Read the rows as grades of one family, not as a ranking that covers every alloy.'
  compare_rows:
    - label: Density
      benchmark: density
    - label: Thermal conductivity
      benchmark: thermal_conductivity
    - label: Tensile strength
      benchmark: ultimate_tensile_strength
  handling:
    - Specify the grade (Zircaloy-2, Zircaloy-4, Zr-2.5Nb or ZIRLO), because tin, iron, nickel and niobium levels differ.
    - 'Keep hydrogen impurity low: 0.0025 % maximum in Zircaloy-2 and -4, 0.0010 % in Zr-2.5Nb.'
    - Keep carbon and nitrogen low, since large amounts degrade corrosion resistance (Wikipedia).
  good_for:
    - 'Fuel cladding in water reactors: Zircaloy-4 is typically used in pressurized water and CANDU reactors (ATI).'
    - 'Low neutron absorption: 0.22 barns for Zircaloy-4, against 0.18 barns for zirconium (ATI).'
    - 'Corrosion in mild acid: under 0.13 mm/a for hot sulfuric acid and 0.05 mm/a for 70 % nitric acid at 120 °C (ATI).'
  watch_out:
    - Hot hydrochloric acid attacks Zircaloy-4 at 0.36 mm/a, and hydrogen from water forms hydrides that embrittle the cladding.
    - 'Hafnium contamination adds neutron absorption: 104 barns for hafnium against 0.22 barns for Zircaloy-4.'
    - Strength of Zircaloy strip depends on direction, so the grain orientation must be stated.
  verdict: Zircaloy-4 and Zr-2.5Nb are the grades with the most published data for nuclear service, and the printed data support their use in water and steam. The research Zr-Al alloys are stronger at room temperature, but they have no commercial grade or corrosion data yet. Hydride cracking and hot hydrochloric acid are the main limits.