spore: profile
id: lithium-hydride
spore_version: 0.2
family: lithium
name: Lithium hydride
abbreviation: LiH
role: neutron shield, hydrogen source and reducing agent
category: shielding
type: hydrogen-rich-polymers
summary: |
  Lithium hydride (LiH) is a white-to-grey powder with a density of 0.78 g/cm3 at 20 °C and a melting point of 688 °C, according to the Albemarle technical data sheet. Its theoretical hydrogen content is 12.7 %. NASA's 1969 shield study calls lithium hydride one of the best neutron shield materials for a space power reactor, and a later NASA paper calls it the most effective neutron shield per unit mass. It hydrolyses rapidly in water and decomposes in humid air, so it must be kept dry and sealed.
best_for: Neutron shielding in space reactor designs where hydrogen per unit mass matters most (NASA TM X-1874 and the NASA nuclear thermal propulsion shielding paper)
weakest_at: 'Water and humid air: the powder hydrolyses rapidly and releases flammable gas, and NASA reports poor thermal conductivity, which makes active cooling of a LiH shield very difficult'
identity:
  formula: LiH
  cas: 7580-67-8
  source: albemarle-tds
  where: Title block (CAS-No. 7580-67-8; Molecular formula LiH); the product is Lithium Hydride, powder < 100 µm
tags:
  environments: []
  stresses:
    - total-radiation-dose
  applications:
    - radiation-shielding
    - electronics-and-chips
properties:
  - benchmark: density
    label: Density, LiH powder, 20 °C
    value: 0.78
    unit: g/cm3
    scope: material
    conditions:
      temperature: 20 °C
      form: powder, product 10000103 (< 100 µm)
    method: Density printed in the Albemarle technical data sheet
    status: ground
    source: albemarle-tds
    where: Physical properties, Density row
  - benchmark: melting_point
    label: Melting point, LiH powder
    value: 688
    unit: °C
    scope: material
    conditions:
      form: powder, product 10000103 (< 100 µm)
      atmosphere: not stated on the data sheet
    method: Melting point or range printed in the Albemarle technical data sheet (single value, no range given)
    status: ground
    source: albemarle-tds
    where: Physical properties, Melting point/range row
  - benchmark: molar_mass
    label: Molar mass of LiH
    value: 7.95
    unit: g/mol
    scope: material
    conditions:
      basis: molecular weight as printed by the supplier
    method: Molecular weight printed in the Albemarle technical data sheet (page 2)
    status: ground
    source: albemarle-tds
    where: Page 2, Molecular weight row
  - benchmark: thermal_decomposition_temperature
    label: Thermal decomposition temperature of LiH
    value: 800
    unit: °C
    scope: material
    conditions:
      printed: abt. 800 °C
      atmosphere: not stated on the data sheet
    method: Thermal stability value printed in the Albemarle technical data sheet, given as an approximate figure
    status: ground
    source: albemarle-tds
    where: Page 2, Thermal Stability row
  - benchmark: theoretical_hydrogen_content
    label: Theoretical hydrogen content of LiH
    value: 12.7
    unit: '%'
    scope: material
    conditions:
      basis: theoretical, from the formula LiH
    method: Value printed in the Albemarle technical data sheet (Additional Physical Properties)
    status: calculated
    source: albemarle-tds
    where: Page 2, Additional Physical Properties row
  - benchmark: hydrogen_yield_from_hydrolysis
    label: Hydrogen evolved per gram of LiH in hydrolysis
    value: 2.82
    unit: L/g
    scope: material
    conditions:
      basis: hydrogen evolved in hydrolysis, as printed in litres of hydrogen per g
      reaction: reaction with water or moisture
    method: Value printed in the Albemarle technical data sheet (Additional Physical Properties); the supplier does not give the gas temperature or pressure
    status: calculated
    source: albemarle-tds
    where: Page 2, Additional Physical Properties row
  - benchmark: hydrogen_equilibrium_pressure
    label: Hydrogen equilibrium pressure of LiH at 500 °C
    value: 0.09
    unit: mbar
    scope: material
    conditions:
      temperature: 500 °C
    method: Equilibrium pressure printed in the Albemarle technical data sheet
    status: ground
    source: albemarle-tds
    where: Page 2, Additional Physical Properties row
  - benchmark: hydrogen_equilibrium_pressure
    label: Hydrogen equilibrium pressure of LiH at 850 °C
    value: 1010
    unit: mbar
    scope: material
    conditions:
      temperature: 850 °C
    method: Equilibrium pressure printed in the Albemarle technical data sheet as approximately 1,010 mbar
    status: ground
    source: albemarle-tds
    where: Page 2, Additional Physical Properties row
  - benchmark: assay
    label: LiH content, minimum (supplier specification)
    value: 97
    unit: '%'
    scope: material
    conditions:
      grade: product 10000103, powder < 100 µm
    method: Minimum specification printed in the Albemarle technical data sheet
    status: ground
    source: albemarle-tds
    where: Specification table, LiH row
  - benchmark: impurity_sodium
    label: Sodium content, maximum (supplier specification)
    value: 0.9
    unit: '%'
    scope: material
    conditions:
      grade: product 10000103, powder < 100 µm
    method: Maximum specification printed in the Albemarle technical data sheet (upper bound)
    status: ground
    source: albemarle-tds
    where: Specification table, Na row
  - benchmark: bulk_density
    label: Bulk density, LiH powder
    value: 290
    value_high: 400
    bound: range
    unit: kg/m3
    scope: material
    conditions:
      form: powder, product 10000103 (< 100 µm)
    method: Range printed in the Albemarle technical data sheet
    status: ground
    source: albemarle-tds
    where: Physical properties, Bulk density row
  - benchmark: hydrogen_atom_density
    label: Hydrogen atom density, natural LiH in a reactor shield model
    value: 0.056837
    unit: atoms/barn-cm
    scope: material
    conditions:
      composition: natural lithium hydride as modelled in the shield region of a 2.2 MWt fast-spectrum space reactor
      source_table: Table I
    method: Atom density printed in NASA TM X-1874 for the model; a calculation input, not a measured property
    status: ground
    source: nasa-tmx1874
    where: Table I, Shield, natural lithium hydride, Hydrogen row
  - benchmark: lithium_6_atom_density
    label: Lithium-6 atom density, natural LiH in a reactor shield model
    value: 0.004217
    unit: atoms/barn-cm
    scope: material
    conditions:
      composition: natural lithium hydride as modelled in the shield region of a 2.2 MWt fast-spectrum space reactor
      source_table: Table I
    method: Atom density printed in NASA TM X-1874 for the model; a calculation input, not a measured property
    status: ground
    source: nasa-tmx1874
    where: Table I, Shield, natural lithium hydride, Lithium-6 row
  - benchmark: lithium_7_atom_density
    label: Lithium-7 atom density, natural LiH in a reactor shield model
    value: 0.05262
    unit: atoms/barn-cm
    scope: material
    conditions:
      composition: natural lithium hydride as modelled in the shield region of a 2.2 MWt fast-spectrum space reactor
      source_table: Table I
    method: Atom density printed in NASA TM X-1874 for the model; a calculation input, not a measured property
    status: ground
    source: nasa-tmx1874
    where: Table I, Shield, natural lithium hydride, Lithium-7 row
corrosion:
  - environment: Water and humid air
    headline: Lithium hydride hydrolyses rapidly and decomposes in contact with humidity, so it must be kept sealed and dry.
    effect: The Albemarle data sheet gives water solubility as 'Substance hydrolyses rapidly' and says the material decomposes in contact with humidity. ICSC 0813 says it reacts violently with water, producing corrosive lithium hydroxide fumes. The NASA shield paper says LiH is reactive and must be sealed within containment.
    rating: severe
    conditions:
      exposure: contact with water or moist air, at room temperature
      product: LiH powder, product 10000103
    source: albemarle-tds
    where: Page 2, Water solubility row; Handling and Storage
  - environment: Light and air at room conditions
    headline: The solid darkens on exposure to light and is hygroscopic.
    effect: ICSC 0813 describes lithium hydride as an odourless white-to-greyish hygroscopic solid that darkens with light exposure. The Albemarle data sheet says that stored under exclusion of air and humidity the material is fairly stable and should be retested 6 months after the date of analysis.
    rating: moderate
    conditions:
      exposure: light and ambient air; exposure time not stated
    source: icsc-0813
    where: Physical State; Appearance
  - environment: Molten LiH in a reactor shield
    headline: Liquid LiH expands in volume, so containment must allow for it.
    effect: NASA's shielding paper (Caffrey et al.) notes that the large volume expansion of lithium hydride in its melted liquid phase must be accounted for during casting and after containment closure, and that poor thermal conductivity limits cooling of the shield.
    rating: moderate
    conditions:
      state: melted liquid phase; expansion figure not given in the paper
    source: caffrey-ntp
    where: Material Selection section
risks:
  hazards:
    - text: PubChem's GHS summary for lithium hydride (CID 62714) lists the signal word Danger and hazard statement H260 (in contact with water releases flammable gases which may ignite spontaneously, 99.5% of ECHA notifications), H301 (toxic if swallowed, 82.4%) and H314 (causes severe skin burns and eye damage, 100%).
      ghs: []
      source: pubchem-lih
      where: GHS Classification, ECHA notified classification ratios
    - text: ICSC 0813 describes the substance as corrosive to the eyes, skin and respiratory tract; inhalation may cause severe swelling of the throat. The card gives a TLV of 0.05 mg/m3 (ceiling value) and an EU-OEL of 0.02 mg/m3 as STEL, both for the inhalable fraction.
      ghs: []
      source: icsc-0813
      where: Health Hazards and First Aid; Occupational Exposure Limits
  failure_risks:
    - mode: Contact with water or humid air
      trigger: Water or moisture reaching the powder or a containment that has been opened
      consequence: Rapid hydrolysis releases flammable gas that may ignite spontaneously (GHS H260) and forms corrosive lithium hydroxide (ICSC 0813).
      severity: high
      source: icsc-0813
      where: Chemical Dangers; GHS hazard statement H260
    - mode: Dust-air mixture
      trigger: Handling or use of the powder
      consequence: In use the powder may form flammable or explosive dust-air mixtures.
      severity: high
      source: albemarle-tds
      where: Page 2, Handling
    - mode: Heating above the stable range
      trigger: Heating of LiH
      consequence: The Albemarle data sheet gives a thermal decomposition at about 800 °C and a hydrogen equilibrium pressure of 0.09 mbar at 500 °C rising to about 1,010 mbar at 850 °C, so hydrogen is released on heating.
      severity: moderate
      source: albemarle-tds
      where: Page 2, Thermal Stability and Additional Physical Properties rows
  side_effects:
    - text: NASA's shielding paper (Caffrey et al.) says LiH's poor thermal conductivity and narrow operating temperature range make effective cooling strategies nearly impossible in high-flux environments, which led the study to set LiH aside in favour of a boron carbide pebble bed.
      affects: Reactor shield cooling and temperature margins
      source: caffrey-ntp
      where: Material Selection section; Shielding Development section on heating
  handling:
    - text: 'Albemarle: handle under an inert gas atmosphere, avoid contact with eyes, skin and clothing, and avoid inhalation. Store in tightly closed containers under exclusion of humidity at gentle temperatures, away from heat, sparks and fire.'
      source: albemarle-tds
      where: Handling & Storage
    - text: 'ICSC 0813: keep under mineral oil or inert gas, dry and cool, and separate from incompatible materials; store in an area without drain or sewer access.'
      source: icsc-0813
      where: Storage
    - text: 'Transport: UN 1414, class 4.3, packing group I (ADR, RID, IMDG and IATA as printed by Albemarle).'
      source: albemarle-tds
      where: Transport & Packaging
  mitigations:
    - text: Retest the material 6 months after the date of analysis if the certificate of analysis is included, or use the manufacturing date for the calculation if it is not (Albemarle).
      source: albemarle-tds
      where: Handling & Storage
    - text: NASA says the reactive nature of LiH mandates that it be sealed within some containment, and NASA's shield designs alternate LiH layers with metal layers to limit secondary gamma production.
      source: caffrey-ntp
      where: Material Selection section
uses:
  - application: radiation-shielding
    device: Layered shield for a nuclear space power reactor (NASA TM X-1874 study, ground analysis)
    example: NASA's 1969 study found an optimized shield weight of 25 300 kg with depleted uranium and 28 500 kg with tungsten, for a 2.2 MW-thermal fast-spectrum reactor, both using natural lithium hydride alternated with four metal layers as the neutron shield.
    source: nasa-tmx1874
    where: Abstract; Summary of results, paragraph on the optimized shield weights
  - application: radiation-shielding
    device: Neutron shield in nuclear thermal propulsion designs (NASA MSFC shielding study)
    example: NASA's shielding paper calls LiH the most effective neutron shield per unit mass, owing to its hydrogen and to lithium-6, but the study set LiH aside in favour of a boron carbide pebble-bed shield for cooling reasons.
    source: caffrey-ntp
    where: Material Selection section; Shielding Development section on heating
  - application: electronics-and-chips
    device: Industrial reducing agent and high-density hydrogen source (terrestrial chemistry, not a flight application)
    example: Albemarle lists lithium hydride as a reducing agent, a high-density hydrogen source and a material for producing high-purity monosilanes.
    source: albemarle-tds
    where: Application row, first page
supply:
  - subject: Lithium
    producers:
      - country: Australia
        share_percent: 31.7
        year: 2025
      - country: China
        share_percent: 21.4
        year: 2025
      - country: Chile
        share_percent: 19.3
        year: 2025
      - country: Zimbabwe
        share_percent: 9.7
        year: 2025
      - country: Argentina
        share_percent: 7.9
        year: 2025
    recycling: 'USGS: construction of lithium battery recycling plants continued throughout 2025, and automobile companies and battery recyclers partnered to supply battery materials.'
    substitutes:
      - 'USGS: substitution for lithium compounds is possible in batteries, ceramics, greases and manufactured glass.'
    source: usgs-mcs2026-lithium
    where: World Mine Production and Reserves table, 2025 (shares calculated by Space Mushroom against the 290,000 t world total in that table); Recycling; Substitutes
documents:
  - title: 'Albemarle technical data sheet: Lithium Hydride, powder < 100 µm (product 10000103, issued 2025/11/28)'
    type: datasheet
    url: https://www.albemarle.com/sites/default/files/2026-01/_TDS_00000138_TDS_ALB_E.PDF
    year: 2025
  - title: 'NASA TM X-1874: Comparison of Tungsten and Depleted Uranium in Minimum-Weight, Layered Shields for a Space Power Reactor (1969)'
    type: report
    url: https://ntrs.nasa.gov/api/citations/19690026439/downloads/19690026439.pdf
    year: 1969
  - title: Shielding Development for Nuclear Thermal Propulsion (Caffrey, Gomez, Scharber; Oregon State University and NASA Marshall)
    type: paper
    url: https://ntrs.nasa.gov/api/citations/20150006884/downloads/20150006884.pdf
  - title: 'PubChem: Lithium hydride (CID 62714), GHS classification summary'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/62714
    year: 2026
  - title: 'ICSC 0813: Lithium hydride (International Chemical Safety Card)'
    type: database
    url: https://www.inchem.org/documents/icsc/icsc/eics0813.htm
  - title: 'USGS Mineral Commodity Summaries 2026: Lithium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-lithium.pdf
    year: 2026
  - title: IUPAC CIAAW standard atomic weight of lithium
    type: database
    url: https://ciaaw.org/lithium.htm
    year: 2009
  - title: IUPAC CIAAW standard atomic weight of hydrogen
    type: database
    url: https://ciaaw.org/hydrogen.htm
    year: 2009
gaps:
  - No media (images or crystal-structure drawings) were added; no licensed image was checked in this run.
  - No thermal conductivity or specific heat for LiH was found in a page we could read. Yaws' Handbook of Thermal Conductivity is the likely source but was not opened.
  - No lattice constant or crystal system was taken from a fetched primary source; Wikipedia gives an fcc NaCl-type structure but is not used for numbers here.
  - No boiling point, flash point or autoignition temperature was taken from a source we could open. Wikipedia lists values, but it is not used for numbers in this profile.
  - Sigma-Aldrich safety data sheet (product 323403) timed out and was not read; hazard data rest on PubChem, ICSC 0813 and the Albemarle data sheet.
  - Manufacturing route and purity controls beyond the Albemarle minimum assay and sodium and potassium limits were not found in a source we could read.
  - Lithium abundance in the Earth's crust, and the USGS and EU critical-mineral list status for lithium, were not read in this run (the USGS 2026 lithium summary was read only for production shares and recycling and substitutes).
  - Hydrogen supply and production shares were not read in a fetched source; the supply block covers lithium only.
  - Molar mass, bulk density, thermal decomposition temperature and hydrogen equilibrium pressure are not canonical names in spores/property-canon.yaml; they are short snake_case or canonical-alias names and were not mapped to the canon file.
  - Atomic weights for the recipe are the lower bounds of the CIAAW intervals (lithium [6.938, 6.997] and hydrogen [1.00784, 1.00811]); the single standard value is not printed by CIAAW.
  - Space flight, vacuum and radiation-exposure results for LiH were not found in a source we could open; the NASA shield results are ground design analyses.
sources:
  albemarle-tds:
    title: 'Technical Data Sheet: Lithium Hydride, powder < 100 µm (Albemarle, product 10000103)'
    id: Albemarle TDS, date of issue 2025/11/28; CAS 7580-67-8; EC 231-484-3
    url: https://www.albemarle.com/sites/default/files/2026-01/_TDS_00000138_TDS_ALB_E.PDF
    year: 2025
    kind: datasheet
    license: supplier document, linked not reproduced
  nasa-tmx1874:
    title: Comparison of Tungsten and Depleted Uranium in Minimum-Weight, Layered Shields for a Space Power Reactor (NASA TM X-1874, Lahti and Herrmann)
    id: NASA NTRS 19690026439; NASA TM X-1874 (August 1969)
    url: https://ntrs.nasa.gov/api/citations/19690026439/downloads/19690026439.pdf
    year: 1969
    kind: report
    license: public domain (NASA)
  caffrey-ntp:
    title: Shielding Development for Nuclear Thermal Propulsion (Caffrey, Gomez, Scharber)
    id: NASA NTRS 20150006884
    url: https://ntrs.nasa.gov/api/citations/20150006884/downloads/20150006884.pdf
    kind: paper
    license: public domain (NASA)
  icsc-0813:
    title: 'ICSC 0813: Lithium hydride, International Programme on Chemical Safety'
    id: ICSC 0813
    url: https://www.inchem.org/documents/icsc/icsc/eics0813.htm
    kind: handbook
    license: public domain (IPCS/INCHEM)
  pubchem-lih:
    title: PubChem compound record, Lithium hydride (CID 62714)
    id: CID 62714; EC 231-484-3
    url: https://pubchem.ncbi.nlm.nih.gov/compound/62714
    year: 2026
    kind: database
    license: public domain (NCBI)
  usgs-mcs2026-lithium:
    title: 'Mineral Commodity Summaries 2026: Lithium'
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-lithium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  ciaaw-lithium:
    title: IUPAC CIAAW standard atomic weight of lithium
    id: CIAAW, interval [6.938, 6.997], since 2009
    url: https://ciaaw.org/lithium.htm
    year: 2009
    kind: database
    license: CIAAW web page
  ciaaw-hydrogen:
    title: IUPAC CIAAW standard atomic weight of hydrogen
    id: CIAAW, interval [1.00784, 1.00811], since 2009
    url: https://ciaaw.org/hydrogen.htm
    year: 2009
    kind: database
    license: CIAAW web page
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 14
  unreachable: 1
  caveats: 3
  note: 'Written by an AI assistant on 2026-11-01 from pages read in this run: 14 property rows from the Albemarle datasheet and the NASA TM X-1874 atom-density table. The Sigma-Aldrich SDS timed out and was not read.'
story:
  recipe:
    line: 'LiH is lithium hydride: one lithium atom and one hydrogen atom per formula unit, as printed in the Albemarle molecular formula. The natural lithium used in NASA''s shield model is a mix of lithium-6 and lithium-7.'
    parts:
      - name: Lithium
        symbol: Li
        atoms: 1
        atomic_weight: 6.938
        role: The neutron absorber. NASA says lithium-6 has a dominant (n,alpha) reaction and that LiH is an excellent neutron absorber when enriched in Li-6; the NASA model uses natural lithium. The atomic weight is the lower bound of the CIAAW interval [6.938, 6.997].
      - name: Hydrogen
        symbol: H
        atoms: 1
        atomic_weight: 1.00784
        role: The moderator. NASA says hydrogen sheds fast-neutron energy by collisions with light atoms, and LiH has a high hydrogen density. The atomic weight is the lower bound of the CIAAW interval [1.00784, 1.00811].
  risk_groups:
    - title: For people
      level: 0
      verdict: Corrosive, toxic powder that reacts with water
      lead: The supplier and ICSC 0813 describe the powder as corrosive and toxic if swallowed, and it releases flammable gas on contact with water.
      points:
        - label: The powder
          line: PubChem's GHS summary lists H314 (severe skin burns and eye damage, 100% of notifications), H301 (toxic if swallowed, 82.4%) and the signal word Danger.
        - label: Dust and air
          line: ICSC 0813 says the solid is corrosive to the eyes, skin and respiratory tract, and inhalation may cause severe swelling of the throat. The TLV is 0.05 mg/m3 as a ceiling value.
        - label: Water
          line: H260 (flammable gas released on contact with water, which may ignite spontaneously) is the main hazard that handlers must avoid.
    - title: If the material gets wet or overheats
      lead: These effects are from supplier and ICSC data, and from NASA design studies, not from incidents.
      points:
        - label: Moisture
          line: The Albemarle data sheet says the material decomposes in contact with humidity and hydrolyses rapidly. Hydrogen is released.
        - label: Heat
          line: The data sheet gives a thermal decomposition at about 800 °C and a hydrogen equilibrium pressure of 0.09 mbar at 500 °C, rising to about 1,010 mbar at 850 °C.
    - title: Handling and storage
      points:
        - label: Atmosphere
          line: Albemarle says to handle the powder under an inert gas atmosphere and to store it in tightly closed containers, excluded from humidity.
        - label: Transport
          line: UN 1414, class 4.3, packing group I, as printed by Albemarle for road, rail, sea and air transport.
  why: Lithium hydride (LiH) is a lithium compound with a high hydrogen content. Albemarle's technical data sheet gives a density of 0.78 g/cm3 and a melting point of 688 °C, and says that the powder decomposes in contact with humidity. NASA's 1969 shield study found LiH to be one of the best neutron shield materials for a space power reactor. A later NASA paper calls it the most effective neutron shield per unit mass, but it sets LiH aside because a simple cooling model could not keep the shield within temperature limits.
  uses:
    - where: Space reactor radiation shields
      line: NASA's 1969 ground study of a 2.2 MW-thermal fast-spectrum reactor found an optimized shield weight of 25 300 kg with depleted uranium and 28 500 kg with tungsten. Both designs used natural lithium hydride as the neutron shield, in four layers alternated with three metal layers.
    - where: Nuclear thermal propulsion shielding
      line: A later NASA shielding paper says lithium hydride is the most effective neutron shield per unit mass, but its poor thermal conductivity makes cooling nearly impossible in a high-flux reactor. The study chose a boron carbide pebble bed instead.
    - where: Chemistry
      line: Albemarle sells lithium hydride as a reducing agent, a high-density hydrogen source and a raw material for high-purity monosilanes. These are terrestrial industrial uses, not space applications.
  can_do:
    - label: Density
      benchmark: density
      line: Lithium hydride powder has a density of 0.78 g/cm3 at 20 °C, per the Albemarle data sheet. Its bulk density is 290 to 400 kg/m3 as a powder.
    - label: Hydrogen content
      benchmark: theoretical_hydrogen_content
      value: 12.7 %
      line: The theoretical hydrogen content is 12.7 %, and the data sheet gives 2.82 litres of hydrogen evolved per gram of LiH in hydrolysis. This is the figure behind its use as a high-density hydrogen source.
    - label: Melting point
      benchmark: melting_point
      value: 688 °C
      line: The data sheet gives a melting point of 688 °C and a thermal decomposition at about 800 °C.
    - label: Purity
      benchmark: assay
      value: 97 %
      line: The supplier specification is a minimum of 97 % LiH, with sodium at most 0.9 % and potassium at most 0.05 %.
  compare: Lithium hydride is the most effective neutron shield per unit mass in NASA's reactor-shield studies, but its cooling is difficult. The NASA shielding paper by Caffrey and colleagues says a boron carbide shield has a mass penalty of about 20 % greater than a practical LiH shield, and that boron carbide has excellent thermal conductivity, hardness and chemical stability. The table compares LiH with the reference points in this profile.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting point
      benchmark: melting_point
    - label: Hydrogen content
      benchmark: theoretical_hydrogen_content
  handling:
    - Handle the powder under an inert gas atmosphere, away from water and humidity (Albemarle).
    - Store in tightly closed containers, dry, cool and separated from incompatible materials (Albemarle and ICSC 0813).
    - Avoid dust. In use the powder may form flammable or explosive dust-air mixtures, and Albemarle says to avoid inhalation.
    - Retest the material 6 months after the analysis date (Albemarle).
  good_for:
    - Neutron shielding by mass. NASA's studies call LiH the most effective neutron shield per unit mass (NASA shielding paper).
    - Hydrogen-dense powder. The theoretical hydrogen content is 12.7 %, and Albemarle sells the powder as a high-density hydrogen source.
  watch_out:
    - Water and humid air. The powder hydrolyses rapidly and releases flammable gas (H260).
    - Poor thermal conductivity. NASA says LiH is hard to cool in a high-flux reactor shield.
    - Corrosive and toxic if swallowed. ICSC 0813 and PubChem describe the powder as corrosive (H314) and toxic (H301).
  verdict: Lithium hydride is the hydrogen-rich neutron shield that NASA's studies rate highest per unit mass, but it must be kept dry and sealed, and it is hard to cool in a reactor. Its use in space shielding has been studied on paper and in ground analysis, and no flight result was found.