Lead-bismuth eutectic (LBE) LBE

spore: profile
id: lead-bismuth-eutectic
spore_version: 0.2
family: low-melting-metals-and-solders
name: Lead-bismuth eutectic (LBE)
abbreviation: LBE
role: liquid-metal coolant
category: metals
type: heavy-metals
summary: |
  Lead-bismuth eutectic (LBE) is a liquid-metal alloy of 44.5 wt.% lead and 55.5 wt.% bismuth. Its melting point is 124 C, and the sources give a normal boiling point of 1670 C and of 1654 C. The IAEA slide table gives a density of 10453 kg/m3 at 200 C. LBE is a candidate coolant for fast reactors, and its main drawbacks are corrosion of steel and polonium-210 formed from bismuth under neutron bombardment.
best_for: Liquid-metal heat transfer at high temperature in fast reactors, where a low melting point and a high boiling point are wanted
weakest_at: Corrosion of steel, which depends on oxygen control, and polonium-210 formation under neutron bombardment; no space flight result was found in the sources opened
identity:
  formula: Pb-Bi eutectic alloy, 44.5 wt.% Pb + 55.5 wt.% Bi (a two-metal alloy, not one compound)
  source: oecd-ch2
  where: Section 2.1 and Table 2.3.3 comments (44.5 wt.% Pb + 55.5 wt.% Bi)
tags:
  environments: []
  stresses: []
  applications:
    - thermal-control
    - radiation-shielding
properties:
  - benchmark: melting_point
    label: Melting point of the eutectic, recommended mean
    value: 397.7
    unit: K
    scope: material
    uncertainty: 0.6 K
    conditions:
      composition: 44.5 wt.% Pb + 55.5 wt.% Bi
      pressure: normal atmospheric pressure
      basis: mean of selected handbook data (Eq. 2.3)
    method: Recommended mean value printed in a handbook compilation of published data
    status: ground
    source: oecd-ch2
    where: Section 2.3.3 (LBE), Eq. (2.3); Table 2.18.3, LBE column
  - benchmark: melting_point
    label: Eutectic melting temperature from the Pb-Bi phase diagram
    value: 124
    unit: °C
    scope: material
    conditions:
      composition: eutectic point at 55.5 wt.% Bi
      pressure: normal atmospheric pressure
    method: Value printed in the description of the Pb-Bi phase diagram
    status: ground
    source: oecd-ch2
    where: Section 2.2, bullet list after Figure 2.2.1
  - benchmark: melting_point
    label: Melting temperature in an IAEA slide table
    value: 125
    unit: °C
    scope: material
    conditions:
      composition: LBE (eutectic), as tabulated
    method: Value printed in a property table comparing LBE, lead, sodium and water
    status: ground
    source: pacio-iaea-2026
    where: Property table on the slide 'Pure lead or lead-bismuth eutectic (LBE)?', LBE column, Melting temperature row
  - benchmark: melting_point
    label: Melting temperature of pure lead, for comparison
    value: 327
    unit: °C
    scope: material
    conditions:
      material: pure lead, not the eutectic
    method: Value printed in the same slide property table
    status: ground
    source: pacio-iaea-2026
    where: Property table on the slide 'Pure lead or lead-bismuth eutectic (LBE)?', Lead column, Melting temperature row
  - benchmark: melting_point
    label: Melting point of pure bismuth, for comparison
    value: 271
    unit: °C
    scope: material
    conditions:
      material: pure bismuth, not the eutectic
    method: Value printed in the USGS bismuth commodity summary text
    status: ground
    source: usgs-bismuth
    where: Domestic Production and Use section, paragraph on metallurgical applications
  - benchmark: boiling_point
    label: Normal boiling temperature, recommended mean
    value: 1943
    unit: K
    scope: material
    uncertainty: 50 K (Eq. 2.9); Table 2.18.3 of the same handbook gives 10 K
    conditions:
      composition: 44.5 wt.% Pb + 55.5 wt.% Bi
      pressure: normal atmospheric pressure
    method: Recommended value printed in the handbook's boiling-point section
    status: ground
    source: oecd-ch2
    where: Section 2.6.3 (LBE), Eq. (2.9); Table 2.18.3, LBE column
  - benchmark: boiling_point
    label: Normal boiling temperature, Kutateladze database entry
    value: 1670
    unit: °C
    scope: material
    conditions:
      composition: 44.5 wt.% Pb + 55.5 wt.% Bi
      purity: unknown
      pressure: normal atmospheric pressure
    method: Value printed in the boiling-point database table (Kutateladze, 1959)
    status: ground
    source: oecd-ch2
    where: Section 2.6.3 (LBE), Table 2.6.3, row 6.3.2
  - benchmark: boiling_point
    label: Boiling temperature in an IAEA slide table
    value: 1654
    unit: °C
    scope: material
    conditions:
      composition: LBE (eutectic), as tabulated
    method: Value printed in the LBE column of the slide property table
    status: ground
    note: Differs from the 1670 °C database entry in the OECD handbook; both are recorded and not averaged.
    source: pacio-iaea-2026
    where: Property table on the slide 'Pure lead or lead-bismuth eutectic (LBE)?', LBE column, Boiling temperature row
  - benchmark: density
    label: Density of LBE at the 200 °C reference temperature
    value: 10453
    unit: kg/m3
    scope: material
    conditions:
      reference_temperature: 200 °C (reference column of the slide table)
      composition: LBE (eutectic)
    method: Value printed in the LBE column of the slide property table
    status: ground
    note: The OECD handbook gives density only as a temperature correlation (see gaps).
    source: pacio-iaea-2026
    where: Property table on the slide 'Pure lead or lead-bismuth eutectic (LBE)?', LBE column, Density row
  - benchmark: specific_heat
    label: Specific heat, constant interpolation (Kutateladze, 1959)
    value: 146.5
    unit: J/(kg·K)
    scope: material
    conditions:
      temperature_range: 403-973 K
      composition: 44.5 wt.% Pb + 55.5 wt.% Bi
      purity: unknown
      basis: constant interpolation function
    method: Constant value printed in the heat-capacity database table (direct heating)
    status: ground
    source: oecd-ch2
    where: Section 2.13.3, Table 2.13.1, row 13.1.2
  - benchmark: specific_heat
    label: Specific heat in an IAEA slide table
    value: 146.9
    unit: J/(kg·K)
    scope: material
    conditions:
      reference_temperature: 200 °C
      composition: LBE (eutectic), as tabulated
    method: Value printed in the LBE column of the slide property table
    status: ground
    source: pacio-iaea-2026
    where: Property table on the slide 'Pure lead or lead-bismuth eutectic (LBE)?', LBE column, Specific heat capacity row
  - benchmark: thermal_conductivity
    label: Thermal conductivity at the 200 °C reference temperature
    value: 10.4
    unit: W/(m·K)
    scope: material
    conditions:
      reference_temperature: 200 °C (reference column of the slide table)
      composition: LBE (eutectic)
    method: Value printed in the LBE column of the slide property table
    status: ground
    note: The OECD handbook gives thermal conductivity only as a temperature correlation (see gaps).
    source: pacio-iaea-2026
    where: Property table on the slide 'Pure lead or lead-bismuth eutectic (LBE)?', LBE column, Thermal conductivity row
  - benchmark: latent_heat_fusion
    label: Latent heat of melting, recommended mean
    value: 38.5
    unit: kJ/kg
    scope: material
    uncertainty: 0.3 kJ/kg
    conditions:
      composition: 44.5 wt.% Pb + 55.5 wt.% Bi
      pressure: normal atmospheric pressure
      molar_value: 8.01 kJ/mol, uncertainty 0.07 kJ/mol
    method: Recommended value printed in the handbook's melting-heat section
    status: ground
    note: Table 2.18.3 of the same handbook gives 38.6 kJ/kg; both are printed.
    source: oecd-ch2
    where: Section 2.5.3, Eq. (2.6)
  - benchmark: heat_of_vaporisation
    label: Latent heat of vaporisation at the normal boiling point
    value: 178
    unit: kJ/mol
    scope: material
    uncertainty: 0.4 kJ/mol
    conditions:
      composition: 44.5 wt.% Pb + 55.5 wt.% Bi
      pressure: normal atmospheric pressure
    method: Recommended value printed in the handbook's vaporisation section
    status: ground
    source: oecd-ch2
    where: Section 2.7.3, Eq. (2.12)
  - benchmark: speed_of_sound
    label: Speed of sound at the 200 °C reference temperature
    value: 1755
    unit: m/s
    scope: material
    conditions:
      reference_temperature: 200 °C
      composition: LBE (eutectic), as tabulated
    method: Value printed in the LBE column of the slide property table
    status: ground
    source: pacio-iaea-2026
    where: Property table on the slide 'Pure lead or lead-bismuth eutectic (LBE)?', LBE column, Speed of sound row
corrosion:
  - environment: Structural steels in flowing LBE at high temperature
    headline: Steel dissolves into flowing LBE at high temperature, and oxygen control decides how fast.
    effect: 'OECD chapter 6 describes dissolution of steel constituents into the liquid metal: under static conditions the corrosion rate falls with time, while in a circuit with a temperature difference, material moves from the hot zone to the cold zone and can plug the loop. Erosion-corrosion occurs at high flow velocity. Wikipedia states that lead and LBE are more corrosive to steel than sodium, which limits coolant flow velocity.'
    rating: moderate
    conditions:
      basis: mechanism description; no corrosion rate in micrometres per year was printed in the sections read
    source: oecd-ch6
    where: Corrosion mechanism section (diffusion through the boundary film, thermal gradient mass transfer, erosion-corrosion); Wikipedia, Limitations section
  - environment: Dissolved oxygen in LBE
    headline: Oxygen decides whether steel dissolves, oxidises or forms a protective film.
    effect: 'OECD chapter 4 reports three corrosion regimes for steels in liquid lead alloy: dissolution when oxygen is too low for a stable oxide film, rapid oxidation at high oxygen, and a transition band between them. For an LBE system whose coldest surface is at 200 °C, the upper oxygen limit for operation is 0.01 ppm. The handbook states that the oxygen potential must be above the film-formation potential on structural steel above 450 °C.'
    rating: moderate
    conditions:
      basis: oxygen control; regimes from Russian test data quoted in OECD chapter 4
    source: oecd-ch4
    where: Sections 4.2.1 (upper limit) and 4.2.2 (lower limit and corrosion regimes)
  - environment: Air and water at ambient conditions
    headline: LBE does not react readily with air or water, unlike sodium.
    effect: Wikipedia states that lead and LBE do not react readily with water or air, in contrast to sodium and NaK, which ignite in air and react explosively with water. The statement is qualitative and the sources opened give no corrosion rate for this case.
    rating: low
    source: wiki-lbe
    where: Advantages section
risks:
  hazards:
    - text: 'PubChem''s GHS summary for lead metal (CID 5352425): notifications provided by 2350 of 2477 reports by companies with hazard statement code(s). The codes listed are H360FD (May damage fertility; May damage the unborn child, signal word Danger), H362, H400 and H410 (Warning). The record is for lead metal, not for the eutectic.'
      ghs:
        - H360FD
        - H362
        - H400
        - H410
      source: pubchem-pb
      where: GHS Classification section
  failure_risks:
    - mode: Oxide blockage of the coolant circuit
      trigger: Oxygen above the upper limit set by the coldest surface
      consequence: Oxide forms first at the coldest point and can be carried to other parts of the circuit, where it blocks flow (OECD chapter 4).
      severity: moderate
      source: oecd-ch4
      where: Section 4.2.1
    - mode: Freezing of the coolant
      trigger: Operation or shutdown near the melting temperature
      consequence: The higher melting points of lead and LBE may mean that solidification is a greater problem when the reactor runs at lower temperatures (Wikipedia). The handbook gives 397.7 K as the melting temperature.
      severity: moderate
      source: wiki-lbe
      where: Limitations section
    - mode: Polonium-210 formation and contamination
      trigger: Neutron capture on bismuth-209 in LBE in a reactor or spallation target
      consequence: Polonium-210 forms, which is a potent alpha emitter, so alpha-contamination precautions are needed during refuelling and component handling (Wikipedia; OECD chapter 5).
      severity: moderate
      source: oecd-ch5
      where: Section 5.1, paragraph on polonium production from 209Bi
    - mode: Wall loss of steel structures
      trigger: High temperature and high flow velocity in steel-walled circuits
      consequence: Dissolution, erosion-corrosion and mass transfer remove wall material from the hotter parts and deposit it in colder parts (OECD chapter 6).
      severity: moderate
      source: oecd-ch6
      where: Corrosion mechanism section
  side_effects:
    - text: Clean LBE is a shiny liquid like a mirror. Dirty LBE shows solid PbO precipitates floating on the surface (IAEA slide 'Primary Coolant must be clean at all times').
      affects: Coolant circuit cleanliness
      source: pacio-iaea-2026
      where: Slide titled 'Primary Coolant must be clean at all times'
  handling:
    - text: Keep oxygen between the upper limit (set by oxide formation at the coldest surface) and the lower limit (set by corrosion protection), as OECD chapter 4 describes.
      source: oecd-ch4
      where: Sections 4.2 to 4.2.2
    - text: Use alpha-contamination precautions for irradiated LBE during refuelling and handling of components in contact with it (Wikipedia, Limitations section).
      source: wiki-lbe
      where: Limitations section
  mitigations:
    - text: Keep enough oxygen in the liquid metal to form a protective oxide film on steel above 450 °C, as OECD chapter 4 describes.
      source: oecd-ch4
      where: Section 4.2.2
uses:
  - application: thermal-control
    device: Primary coolant in fast reactors and transportable nuclear power plants
    example: The OECD handbook lists LBE among candidate coolants for new-generation fast reactors and for liquid spallation neutron sources and accelerated driven systems. Wikipedia reports that the Soviet Alfa-class submarines used LBE as reactor coolant throughout the Cold War.
    source: oecd-ch2
    where: Section 2.1 (Introduction); Wikipedia, History section
  - application: radiation-shielding
    device: Gamma shield and spallation target
    example: Lead and bismuth absorb gamma radiation while being nearly transparent to neutrons, and as heavy nuclei they can be used as spallation targets for non-fission neutron production (Wikipedia, Advantages section).
    source: wiki-lbe
    where: Advantages section
supply:
  - subject: Bismuth (LBE is 55.5 wt.% bismuth)
    producers:
      - country: China
        share_percent: 88
        year: 2025
    critical_lists: []
    recycling: 'USGS: recycled bismuth-containing alloy scrap was estimated to compose up to 10% of U.S. bismuth apparent consumption for 2021 to 2025.'
    substitutes:
      - 'USGS: cadmium, indium, lead and tin can partially replace bismuth in low-temperature solders; bismuth is a nontoxic substitute for lead in plumbing and other applications.'
    source: usgs-bismuth
    where: World Refinery Production and Capacity; Recycling; Substitutes. China accounted for 88% of world bismuth production in 2025 (USGS text).
  - subject: Lead (LBE is 44.5 wt.% lead)
    abundance: Identified world lead resources total more than 2 billion tons (USGS)
    producers:
      - country: China
        share_percent: 42.2
        year: 2025
      - country: Australia
        share_percent: 10.7
        year: 2025
      - country: Peru
        share_percent: 6.4
        year: 2025
      - country: Russia
        share_percent: 5.8
        year: 2025
    critical_lists:
      - list: U.S. Final 2025 List of Critical Minerals (lead added)
        listed: true
    recycling: 'USGS: in 2025 an estimated 1 million tons of secondary lead was produced, equal to 70% of apparent U.S. consumption; nearly all came from old scrap, mostly lead-acid batteries.'
    substitutes:
      - 'USGS: plastics have reduced lead in cable covering and cans; tin has replaced lead in solder for potable water systems; steel and zinc are common substitutes in wheel weights.'
    source: usgs-lead
    where: World Mine Production and Reserves table, 2025e (world total 4,500 thousand t; shares calculated by Space Mushroom from the country values); U.S. critical minerals text; Recycling; Substitutes
documents:
  - title: 'OECD NEA Handbook on Lead-bismuth Eutectic Alloy and Lead Properties, Chapter 2: Thermophysical and electric properties'
    type: report
    url: https://www.oecd-nea.org/science/reports/2007/pdf/chapter2.pdf
    year: 2007
  - title: 'OECD NEA Handbook on Lead-bismuth Eutectic Alloy and Lead Properties, Chapter 4: Chemistry control and monitoring systems'
    type: report
    url: https://www.oecd-nea.org/science/reports/2007/pdf/chapter4.pdf
    year: 2007
  - title: 'OECD NEA Handbook on Lead-bismuth Eutectic Alloy and Lead Properties, Chapter 5: Properties of irradiated LBE and Pb'
    type: report
    url: https://www.oecd-nea.org/science/reports/2007/pdf/chapter5.pdf
    year: 2007
  - title: 'OECD NEA Handbook on Lead-bismuth Eutectic Alloy and Lead Properties, Chapter 6: Compatibility of structural materials with LBE and Pb'
    type: report
    url: https://www.oecd-nea.org/science/reports/2007/pdf/chapter6.pdf
    year: 2007
  - title: 'Lead-Bismuth Eutectic Alloy as a Coolant: Benefits and Challenges (IAEA event slides, Pacio, SCK CEN)'
    type: report
    url: https://conferences.iaea.org/event/460/contributions/39519/attachments/22106/38018/2026_02_17_Pacio_IAEA_Lead-Bismuth%20Eutectic%20Alloy%20as%20a%20Coolant%20Benefits%20and%20Challenges.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Bismuth'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-bismuth.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Lead'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-lead.pdf
    year: 2026
  - title: 'PubChem: Lead (CID 5352425), GHS classification'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Lead
    year: 2026
  - title: 'Wikipedia: Lead-bismuth eutectic'
    type: database
    url: https://en.wikipedia.org/wiki/Lead%E2%80%93bismuth_eutectic
    year: 2026
gaps:
  - No density value at a fixed temperature was printed in the OECD handbook. It gives only the correlation rho = 11096 - 1.3236 T kg/m3 (T in K) for 403 to 1300 K with an estimated error of 0.8 % (Table 2.18.3). The IAEA slide value of 10453 kg/m3 at 200 C is recorded instead.
  - Electrical resistivity, dynamic viscosity, surface tension and thermal conductivity versus temperature appear in OECD and in the Chusov et al. correlations only as functions of temperature, several with exponents. No printed value at a fixed temperature was recorded except the 200 C thermal conductivity from the IAEA table.
  - Surface tension and kinematic viscosity at 200 C appear in the IAEA slide table but are printed in exponent form, so they are not recorded.
  - 'Volume change on melting: the handbook gives approximately zero for LBE (Table 2.4.1) and Wikipedia says negligible change. No numeric value was recorded because the printed value is zero.'
  - 'Boiling temperature disagrees across sources: 1670 C (OECD database), 1654 C (IAEA table) and 1943 K recommended in OECD with an uncertainty printed as 50 K in Eq. (2.9) and 10 K in Table 2.18.3. All are recorded; none is chosen.'
  - 'Melting temperature: the OECD handbook gives a range of 123.5 to 125.5 C in its database; 124 C, 125 C and 397.7 K are recorded.'
  - No UNS, EN, ASTM or trade designation for the eutectic was printed in the sources opened. It is named by composition only.
  - No space flight, vacuum, radiation-test or outgassing result for LBE was found in the sources opened. The earlier claim of space nuclear concepts is not supported by a source in this profile.
  - 'Atomic oxygen and vacuum behaviour of LBE: not found.'
  - 'Corrosion rates for steels in LBE in micrometres per year: not printed in the chapters read, so the corrosion ratings are qualitative.'
  - 'Polonium release and volatility from LBE: OECD chapter 5 discusses evaporation, but its numbers are in exponent form and were not recorded.'
  - Hazard classification for bismuth metal was not read in this run. Only the PubChem record for lead metal was opened, and it is for lead, not for the eutectic.
  - Sodium and water comparison columns of the IAEA slide table are not recorded in this profile.
  - No nuclear-reactor application slug exists in the taxonomy. Reactor coolant use is recorded under thermal control.
  - 'Critical-minerals listing for bismuth: the USGS bismuth summary does not state one, and the EU list was not checked.'
sources:
  oecd-ch2:
    title: 'OECD NEA Handbook on Lead-bismuth Eutectic Alloy and Lead Properties, Chapter 2: Thermophysical and electric properties'
    id: OECD NEA 2007 handbook, chapter 2 (PDF)
    url: https://www.oecd-nea.org/science/reports/2007/pdf/chapter2.pdf
    year: 2007
    kind: handbook
    license: OECD NEA publication (cited, not reproduced)
  oecd-ch4:
    title: 'OECD NEA Handbook on Lead-bismuth Eutectic Alloy and Lead Properties, Chapter 4: Chemistry control and monitoring systems'
    id: OECD NEA 2007 handbook, chapter 4 (PDF)
    url: https://www.oecd-nea.org/science/reports/2007/pdf/chapter4.pdf
    year: 2007
    kind: handbook
    license: OECD NEA publication (cited, not reproduced)
  oecd-ch5:
    title: 'OECD NEA Handbook on Lead-bismuth Eutectic Alloy and Lead Properties, Chapter 5: Properties of irradiated LBE and Pb'
    id: OECD NEA 2007 handbook, chapter 5 (PDF)
    url: https://www.oecd-nea.org/science/reports/2007/pdf/chapter5.pdf
    year: 2007
    kind: handbook
    license: OECD NEA publication (cited, not reproduced)
  oecd-ch6:
    title: 'OECD NEA Handbook on Lead-bismuth Eutectic Alloy and Lead Properties, Chapter 6: Compatibility of structural materials with LBE and Pb'
    id: OECD NEA 2007 handbook, chapter 6 (PDF)
    url: https://www.oecd-nea.org/science/reports/2007/pdf/chapter6.pdf
    year: 2007
    kind: handbook
    license: OECD NEA publication (cited, not reproduced)
  pacio-iaea-2026:
    title: 'Lead-Bismuth Eutectic Alloy as a Coolant: Benefits and Challenges (IAEA event slides, 17 February 2026, Pacio, SCK CEN)'
    id: IAEA event 460, contribution 39519
    url: https://conferences.iaea.org/event/460/contributions/39519/attachments/22106/38018/2026_02_17_Pacio_IAEA_Lead-Bismuth%20Eutectic%20Alloy%20as%20a%20Coolant%20Benefits%20and%20Challenges.pdf
    year: 2026
    kind: report
    license: Conference slides (cited, not reproduced)
  usgs-bismuth:
    title: Mineral Commodity Summaries 2026, Bismuth
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-bismuth.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-lead:
    title: Mineral Commodity Summaries 2026, Lead
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-lead.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  pubchem-pb:
    title: PubChem compound record, Lead (CID 5352425), GHS classification
    id: CID 5352425; CAS 7439-92-1
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Lead
    year: 2026
    kind: database
    license: public domain (NCBI)
  wiki-lbe:
    title: Lead-bismuth eutectic (Wikipedia)
    url: https://en.wikipedia.org/wiki/Lead%E2%80%93bismuth_eutectic
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 15
  unreachable: 1
  caveats: 3
  note: 'Values read by an AI assistant on 2026-11-01 from the OECD handbook chapters and the IAEA slide table fetched in this run; USGS, PubChem and Wikipedia text checked by reading. Unreachable: American Elements (HTTP 403), so its density figure is not used. Caveats: the handbook disagrees with itself on boiling temperature and heat of melting; density is recorded only from the slide table at 200 C.'
story:
  recipe:
    line: Lead-bismuth eutectic is a two-metal alloy of 44.5 wt.% lead and 55.5 wt.% bismuth (OECD handbook). The sources opened do not describe how the alloy is made, so the process is not stated here.
    parts:
      - name: Lead
        symbol: Pb
        share_percent: 44.5
        role: Melts together with bismuth at the eutectic composition, which gives the lowest melting point of the pair.
        source: oecd-ch2
        where: Section 2.1 and Table 2.3.3 comments
      - name: Bismuth
        symbol: Bi
        share_percent: 55.5
        role: The larger share by weight. Bismuth-209 is the source of polonium-210 when it captures a neutron in the coolant.
        source: oecd-ch2
        where: Section 2.1 and Table 2.3.3 comments
  risk_groups:
    - title: For people
      lead: The hazards are the lead content and, after irradiation, polonium-210. The sources opened do not describe a hazard classification for the alloy itself.
      level: 2
      verdict: Lead hazards; polonium after irradiation
      points:
        - label: Lead
          line: PubChem's GHS summary for lead metal lists H360FD (may damage fertility and the unborn child, signal word Danger), H362, H400 and H410. It reports notifications from 2350 of 2477 company reports with hazard codes.
        - label: Irradiated LBE
          line: Bismuth-209 captures a neutron and forms polonium-210, a potent alpha emitter. Irradiated LBE needs alpha-contamination precautions during refuelling and handling (Wikipedia; OECD chapter 5).
    - title: If the coolant fails
      lead: These are chemistry and freezing routes found in the sources. None is a field incident in the sources opened.
      level: 2
      verdict: Oxide plugs and freezing
      points:
        - label: Oxide
          line: If oxygen is too high, oxide forms first at the coldest surface. For an LBE system whose coldest surface is at 200 °C, the upper oxygen limit for operation is 0.01 ppm (OECD chapter 4).
        - label: Freezing
          line: The melting point is 124 °C, so the coolant freezes if it is run too cold. Wikipedia notes that solidification may be a greater problem at lower operating temperatures.
        - label: Corrosion
          line: Steel dissolves or oxidises depending on the oxygen level. OECD chapter 4 describes three corrosion regimes for steels in lead alloys.
    - title: Handling and storage
      points:
        - label: Cleanliness
          line: Clean LBE looks like a shiny liquid, like a mirror. Dirty LBE shows solid PbO floating on it, which is why the slide deck says the coolant must be kept clean at all times.
        - label: Oxygen
          line: Oxygen is kept between an upper limit set by oxide formation and a lower limit set by corrosion protection. Above 450 °C a protective oxide film can form on steel (OECD chapter 4).
  why: Lead-bismuth eutectic (LBE) is a liquid metal made of 44.5 wt.% lead and 55.5 wt.% bismuth. It melts at 124 °C, well below pure bismuth at 271 °C and pure lead at 327 °C, and it boils at about 1670 °C in the OECD database. Its low melting point and high boiling point let it carry heat without high pressure, which is why it is studied as a coolant for fast reactors. The trade-offs are corrosion of steel, which depends on oxygen control, and polonium-210 formed from bismuth under neutron bombardment.
  uses:
    - where: Fast reactors and transportable nuclear plants
      line: The OECD handbook lists LBE among candidate coolants for new-generation fast reactors and for liquid spallation neutron sources and accelerated driven systems. Wikipedia reports that the Soviet Alfa-class submarines used LBE as reactor coolant throughout the Cold War.
    - where: Gamma shield and spallation target
      line: Lead and bismuth absorb gamma radiation and are nearly transparent to neutrons. As heavy nuclei they can serve as spallation targets for producing neutrons (Wikipedia).
  can_do:
    - label: Melting
      value: 124 °C
      line: The eutectic melts at 124 °C. The handbook's recommended mean is 397.7 K with an uncertainty of 0.6 K.
    - label: Boiling
      value: 1670 °C
      line: The OECD database gives a normal boiling temperature of 1670 °C. The IAEA slide table gives 1654 °C, and the recommended boiling temperature in the handbook is 1943 K.
    - label: Density
      value: 10453 kg/m3 at 200 °C
      line: The IAEA slide table gives a density of 10453 kg/m3 at the 200 °C reference temperature. The handbook gives only a temperature correlation for density.
    - label: Heat storage
      value: 146.5 J/(kg·K)
      line: The handbook's constant specific heat is 146.5 J/(kg·K) over 403 to 973 K (Kutateladze, 1959). The IAEA table gives 146.9 J/(kg·K) at 200 °C.
    - label: Heat carrying
      value: 10.4 W/(m·K)
      line: The thermal conductivity is 10.4 W/(m·K) at the 200 °C reference temperature in the IAEA table.
    - label: Phase change energy
      value: 178 kJ/mol
      line: Evaporation needs 178 kJ/mol at the normal boiling point (recommended, uncertainty 0.4 kJ/mol). Melting needs 38.5 kJ/kg (uncertainty 0.3 kJ/kg).
    - label: Sound
      value: 1755 m/s
      line: The speed of sound at 200 °C is 1755 m/s in the IAEA table.
  compare: Compared with its two parts, LBE melts at 124 °C, below pure bismuth at 271 °C and pure lead at 327 °C. Its melting point is the reason it stays liquid in a coolant loop at temperatures where either metal alone would be solid. The handbook gives a density only as a temperature correlation, so the density in the table comes from the IAEA slide value at 200 °C rather than from a like-for-like comparison.
  compare_rows:
    - label: Melting point
      benchmark: melting_point
    - label: Density
      benchmark: density
    - label: Thermal conductivity
      benchmark: thermal_conductivity
  handling:
    - Keep the metal clean. Oxygen must stay between the upper limit set by oxide formation and the lower limit set by corrosion protection.
    - Treat irradiated LBE as polonium-bearing material and use alpha-contamination precautions during refuelling and component handling.
    - Keep the metal above its melting point of 124 °C in service to avoid freezing in the circuit.
  good_for:
    - 'Liquid-metal heat transfer at high temperature: liquid from 124 °C up to about 1670 °C in the OECD database.'
    - Radiation shielding against gamma rays while passing neutrons, per Wikipedia.
  watch_out:
    - 'Corrosion of steel: LBE is more corrosive to steel than sodium (Wikipedia), and the rate depends on oxygen (OECD chapter 4).'
    - Polonium-210 forms from bismuth-209 under neutron bombardment (OECD chapter 5; Wikipedia).
    - 'Freezing: the coolant solidifies at 124 °C and can block cold parts of a circuit (Wikipedia; OECD chapter 4).'
    - No space flight result was found. The sources give fast-reactor and ground test uses only.
  verdict: LBE is a well-characterised liquid-metal coolant with printed melting and boiling points, a printed density at 200 °C and a printed heat capacity. Its main limits are corrosion of steel, oxygen control and polonium production, and no space flight record was found in the sources opened.