{ "spore": "profile", "id": "potassium", "spore_version": "0.2", "family": "alkali-and-alkaline-earth-metals", "name": "Potassium metal and NaK eutectic", "abbreviation": "K", "role": "liquid-metal coolant", "category": "metals", "type": "heavy-metals", "summary": "Potassium is a soft silvery alkali metal that melts at 63.5 degC and boils at 759 degC. Mixed with sodium as the eutectic NaK-78 (22% sodium and 78% potassium by weight), it stays liquid down to -12.6 degC, which made it a working coolant for space fission reactors. The metal reacts violently with water, and that is the main hazard in handling and in any loop leak.\n", "best_for": "Liquid-metal heat transport in space fission reactor loops, where NaK stays liquid at room temperature", "weakest_at": "Any contact with water or oxygen: it reacts violently with water and forms a surface crust in air", "identity": { "formula": "K", "cas": "7440-09-7", "designations": [], "source": "pubchem-k", "where": "Names and Identifiers > Other Identifiers > CAS (7440-09-7). NaK-78 composition (22% Na and 78% K by weight) from the 1973 NASA and AEC summary report, Introduction." }, "tags": { "environments": [], "stresses": [], "applications": [ "thermal-control" ] }, "properties": [ { "benchmark": "melting_point", "label": "Melting point, potassium metal", "value": 63.5, "bound": "exact", "unit": "degC", "scope": "material", "conditions": { "form": "potassium metal, pure element as listed in PubChem" }, "method": "Experimental value listed in the PubChem compound record", "status": "ground", "source": "pubchem-k", "where": "Chemical and Physical Properties > Experimental Properties > Melting Point (63.5 degC entry)", "source_detail": { "title": "PubChem compound record, Potassium (CID 5462222)", "id": "CID 5462222; CAS 7440-09-7", "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/5462222/JSON", "year": 2026, "kind": "database", "license": "public domain (NCBI)" } }, { "benchmark": "boiling_point", "label": "Boiling point, potassium metal", "value": 759, "bound": "exact", "unit": "degC", "scope": "material", "conditions": { "pressure": "760 mmHg" }, "method": "Experimental value listed in the PubChem compound record", "status": "ground", "note": "A supplier SDS gives 774 degC at 1013 hPa. Both values are kept as printed; see the supplier SDS rows.", "source": "pubchem-k", "where": "Chemical and Physical Properties > Experimental Properties > Boiling Point (759 degC at 760 mmHg)", "source_detail": { "title": "PubChem compound record, Potassium (CID 5462222)", "id": "CID 5462222; CAS 7440-09-7", "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/5462222/JSON", "year": 2026, "kind": "database", "license": "public domain (NCBI)" } }, { "benchmark": "density", "label": "Density, potassium metal", "value": 0.856, "bound": "exact", "unit": "g/cm3", "scope": "material", "conditions": { "temperature": "not stated in the record" }, "method": "Experimental value listed in the PubChem compound record", "status": "ground", "source": "pubchem-k", "where": "Chemical and Physical Properties > Experimental Properties > Density (0.856 g/cm3 entry)", "source_detail": { "title": "PubChem compound record, Potassium (CID 5462222)", "id": "CID 5462222; CAS 7440-09-7", "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/5462222/JSON", "year": 2026, "kind": "database", "license": "public domain (NCBI)" } }, { "benchmark": "specific_heat", "label": "Specific heat at 0 degC, potassium metal", "value": 0.176, "bound": "exact", "unit": "cal/(g deg)", "scope": "material", "conditions": { "temperature": "0 degC", "unit_in_source": "cal/g deg" }, "method": "Experimental value listed in PubChem, kept in the unit it prints (not converted to J/(kg K))", "status": "ground", "source": "pubchem-k", "where": "Chemical and Physical Properties > Experimental Properties > Other Experimental Properties (specific heat, 0 degC)", "source_detail": { "title": "PubChem compound record, Potassium (CID 5462222)", "id": "CID 5462222; CAS 7440-09-7", "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/5462222/JSON", "year": 2026, "kind": "database", "license": "public domain (NCBI)" } }, { "benchmark": "thermal_conductivity", "label": "Thermal conductivity at 21 degC, potassium metal", "value": 0.23, "bound": "exact", "unit": "cal/(sec degC cm)", "scope": "material", "conditions": { "temperature": "21 degC", "unit_in_source": "cal/(sec degC cm)" }, "method": "Experimental value listed in PubChem, kept in the unit it prints (not converted to W/(m K))", "status": "ground", "source": "pubchem-k", "where": "Chemical and Physical Properties > Experimental Properties > Other Experimental Properties (thermal conductivity, 21 degC entry)", "source_detail": { "title": "PubChem compound record, Potassium (CID 5462222)", "id": "CID 5462222; CAS 7440-09-7", "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/5462222/JSON", "year": 2026, "kind": "database", "license": "public domain (NCBI)" } }, { "benchmark": "thermal_conductivity", "label": "Thermal conductivity at 400 degC, potassium metal", "value": 0.956, "bound": "exact", "unit": "cal/(sec degC cm)", "scope": "material", "conditions": { "temperature": "400 degC", "unit_in_source": "cal/(sec degC cm)" }, "method": "Experimental value listed in PubChem, kept in the unit it prints (not converted to W/(m K))", "status": "ground", "source": "pubchem-k", "where": "Chemical and Physical Properties > Experimental Properties > Other Experimental Properties (thermal conductivity, 400 degC entry)", "source_detail": { "title": "PubChem compound record, Potassium (CID 5462222)", "id": "CID 5462222; CAS 7440-09-7", "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/5462222/JSON", "year": 2026, "kind": "database", "license": "public domain (NCBI)" } }, { "benchmark": "vapor_pressure", "label": "Vapor pressure at 432 degC, potassium metal", "value": 8, "bound": "exact", "unit": "mm Hg", "scope": "material", "conditions": { "temperature": "432 degC" }, "method": "Experimental value listed in the PubChem compound record", "status": "ground", "source": "pubchem-k", "where": "Chemical and Physical Properties > Experimental Properties > Vapor Pressure (8 mm Hg at 432 degC)", "source_detail": { "title": "PubChem compound record, Potassium (CID 5462222)", "id": "CID 5462222; CAS 7440-09-7", "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/5462222/JSON", "year": 2026, "kind": "database", "license": "public domain (NCBI)" } }, { "benchmark": "melting_point", "label": "Melting point, supplier SDS (potassium metal)", "value": 64, "bound": "exact", "unit": "degC", "scope": "material", "conditions": { "form": "potassium metal, supplier SDS" }, "method": "Value printed in the supplier safety data sheet, Section 9", "status": "ground", "note": "Rounded value. PubChem gives 63.5 degC.", "source": "sa-k", "where": "Section 9, Melting point/freezing point", "source_detail": { "title": "Safety data sheet: Potassium metal (Stanford Advanced Materials)", "id": "revised 19 January 2023", "url": "https://samaterials.com/tds/1697120713-1699-potassium-k-metal-sds.pdf", "year": 2023, "kind": "datasheet", "license": "supplier document, linked not reproduced" } }, { "benchmark": "boiling_point", "label": "Boiling point, supplier SDS (potassium metal)", "value": 774, "bound": "exact", "unit": "degC", "scope": "material", "conditions": { "pressure": "1013 hPa (760 mmHg)" }, "method": "Value printed in the supplier safety data sheet, Section 9", "status": "ground", "note": "Differs from the PubChem value of 759 degC. Both are kept as printed.", "source": "sa-k", "where": "Section 9, Initial boiling point and boiling range", "source_detail": { "title": "Safety data sheet: Potassium metal (Stanford Advanced Materials)", "id": "revised 19 January 2023", "url": "https://samaterials.com/tds/1697120713-1699-potassium-k-metal-sds.pdf", "year": 2023, "kind": "datasheet", "license": "supplier document, linked not reproduced" } }, { "benchmark": "density", "label": "Relative density, supplier SDS (potassium metal)", "value": 0.86, "bound": "exact", "unit": "g/cm3", "scope": "material", "conditions": { "temperature": "not stated in the SDS" }, "method": "Value printed in the supplier safety data sheet, Section 9", "status": "ground", "source": "sa-k", "where": "Section 9, Relative density (0.860 g/cm3)", "source_detail": { "title": "Safety data sheet: Potassium metal (Stanford Advanced Materials)", "id": "revised 19 January 2023", "url": "https://samaterials.com/tds/1697120713-1699-potassium-k-metal-sds.pdf", "year": 2023, "kind": "datasheet", "license": "supplier document, linked not reproduced" } }, { "benchmark": "vapor_pressure", "label": "Vapor pressure at 260 degC, supplier SDS (potassium metal)", "value": 0.12, "bound": "exact", "unit": "hPa", "scope": "material", "conditions": { "temperature": "260 degC" }, "method": "Value printed in the supplier safety data sheet, Section 9", "status": "ground", "source": "sa-k", "where": "Section 9, Vapor pressure (0.12 hPa at 260 degC)", "source_detail": { "title": "Safety data sheet: Potassium metal (Stanford Advanced Materials)", "id": "revised 19 January 2023", "url": "https://samaterials.com/tds/1697120713-1699-potassium-k-metal-sds.pdf", "year": 2023, "kind": "datasheet", "license": "supplier document, linked not reproduced" } }, { "benchmark": "melting_point", "label": "Melting point, NaK-78 eutectic", "value": -12.6, "bound": "exact", "unit": "degC", "scope": "material", "conditions": { "material": "NaK-78 eutectic, 22% Na and 78% K by weight" }, "method": "Value stated in a NASA paper on a NaK-cooled circuit", "status": "ground", "source": "nasa-2006", "where": "Introduction, paragraph on liquid metals for space reactors (melting point of -12.6 degC)", "source_detail": { "title": "Design, Fabrication and Integration of a NaK-Cooled Circuit (NASA Marshall Space Flight Center, Paper 6389, 2006)", "id": "NTRS 20060025550", "url": "https://ntrs.nasa.gov/citations/20060025550", "year": 2006, "kind": "paper", "license": "public domain (NASA)" } }, { "benchmark": "boiling_point", "label": "Boiling point, NaK-78 eutectic", "value": 785, "bound": "exact", "unit": "degC", "scope": "material", "conditions": { "material": "NaK-78 eutectic, 22% Na and 78% K by weight" }, "method": "Value stated in a NASA paper on a NaK-cooled circuit", "status": "ground", "source": "nasa-2006", "where": "Introduction, paragraph on liquid metals for space reactors (boiling point of 785 degC)", "source_detail": { "title": "Design, Fabrication and Integration of a NaK-Cooled Circuit (NASA Marshall Space Flight Center, Paper 6389, 2006)", "id": "NTRS 20060025550", "url": "https://ntrs.nasa.gov/citations/20060025550", "year": 2006, "kind": "paper", "license": "public domain (NASA)" } }, { "benchmark": "volume_expansion", "label": "Volume increase of NaK heated from 25 degC to 650 degC", "value": 17, "bound": "exact", "unit": "%", "scope": "material", "conditions": { "material": "NaK", "from_temperature": "25 degC", "to_temperature": "650 degC" }, "method": "Value stated in a NASA paper on the fission surface power test circuit", "status": "ground", "source": "nasa-2007", "where": "Circuit design section, paragraph on expansion reservoir (NaK expands to 17% above its volume at 25 degC)", "source_detail": { "title": "Capabilities and Testing of the Fission Surface Power Primary Test Circuit (FSP-PTC), Space Nuclear Conference 2007, Paper 2030", "id": "NTRS 20070031971", "url": "https://ntrs.nasa.gov/citations/20070031971", "year": 2007, "kind": "paper", "license": "public domain (NASA)" } } ], "corrosion": [ { "environment": "Liquid water and wet air", "headline": "Potassium reacts violently with water, releasing hydrogen and forming a caustic hydroxide.", "effect": "NOAA CAMEO Chemicals records that potassium reacts violently or explosively with water. The PubChem entry for the alloy form says the reaction forms potassium hydroxide, a corrosive material, and hydrogen, a flammable gas that the heat may ignite.", "rating": "severe", "conditions": { "exposure": "contact with liquid or moist air", "form": "potassium metal" }, "source": "cameo-k", "where": "Reactivity profile, water entry" }, { "environment": "Oxygen in air (NaK in a loop)", "headline": "NaK forms a crust of potassium oxide, peroxide and superoxide on its surface.", "effect": "Exposure to oxygen makes NaK form potassium oxide, potassium peroxide and potassium superoxide, which create a crust on the surface of the liquid metal. NASA lists this as a disadvantage of NaK.", "rating": "moderate", "conditions": { "form": "NaK-78 eutectic", "temperature": "not stated in the paper" }, "source": "nasa-2006", "where": "Introduction, paragraph on the disadvantages of NaK" }, { "environment": "Stainless steel in NaK up to 650 degC", "headline": "NaK has shown good compatibility with stainless steel up to 650 degC.", "effect": "NASA reports good compatibility between NaK and stainless steel over the temperature range tested, with a maximum of 650 degC. The paper gives no corrosion rate.", "rating": "low", "conditions": { "temperature": "up to 650 degC", "material": "stainless steel" }, "source": "nasa-2007", "where": "Introduction, paragraph on NaK properties" } ], "risks": { "hazards": [ { "text": "Classified Danger. In contact with water it releases flammable gases which may ignite spontaneously (H260), as reported in PubChem and the supplier SDS.", "ghs": [ "H260" ], "source": "pubchem-k", "where": "Safety and Hazards > GHS Classification (H260)" }, { "text": "Causes severe skin burns and eye damage (H314), as reported in PubChem and the supplier SDS.", "ghs": [ "H314" ], "source": "sa-k", "where": "Section 2, Hazards identification (H314)" }, { "text": "UN number 2257 (potassium) appears in the PubChem record.", "ghs": [], "source": "pubchem-k", "where": "Names and Identifiers > Other Identifiers > UN Number" } ], "failure_risks": [ { "mode": "Water entering the metal or the loop", "trigger": "Leak, wet surface, or moisture during storage, handling or filling", "consequence": "Violent reaction releases hydrogen, which may ignite spontaneously. The SDS warns of possible flash fire.", "severity": "high", "source": "sa-k", "where": "Section 2 (precautionary statement P223) and Section 10 (reacts violently with water)" }, { "mode": "Crust formation on the NaK surface", "trigger": "Exposure of NaK to oxygen", "consequence": "Potassium oxide, peroxide and superoxide form a crust on the liquid surface, which NASA lists as a disadvantage of NaK.", "severity": "moderate", "source": "nasa-2006", "where": "Introduction, paragraph on the disadvantages of NaK" } ], "side_effects": [ { "text": "Reaction with water forms hydrogen gas and potassium hydroxide, a corrosive solution.", "affects": "Anything the reaction products contact, including the loop or enclosure", "source": "pubchem-k", "where": "Chemical and Physical Properties > Physical Description (alloy entry)" } ], "handling": [ { "text": "Handle under inert gas and protect from moisture. Keep away from any possible contact with water.", "source": "sa-k", "where": "Section 2 (P223, P231 plus P232) and Section 7" }, { "text": "Never allow the product to contact water during storage. Handle and store under inert gas.", "source": "sa-k", "where": "Section 7, Conditions for safe storage" } ], "mitigations": [ { "text": "Use stainless steel, which NASA found compatible with NaK up to 650 degC in its test circuit.", "source": "nasa-2007", "where": "Introduction, paragraph on NaK properties" }, { "text": "Fight fires with dry sand, dry chemical or alcohol-resistant foam, as the SDS directs.", "source": "sa-k", "where": "Section 2 (P370 plus P378) and Section 5 (dry powder)" } ] }, "uses": [ { "application": "thermal-control", "device": "Liquid-metal reactor coolant loop for a space fission power system", "example": "The 1973 NASA and AEC summary describes a 5-kWe thermoelectric system in which reactor heat was carried by NaK, a eutectic of 22% Na and 78% K by weight, to a radiator.", "source": "nasa-1973", "where": "Description of the 5-kWe system, text near Figure 1" }, { "application": "thermal-control", "device": "Primary test circuit for fission surface power (ground test)", "example": "NASA Marshall selected NaK as the primary coolant for its fission surface power primary test circuit, because NaK was the coolant of the SNAP-10A fission reactor.", "source": "nasa-2007", "where": "Abstract" } ], "supply": [ { "subject": "Potassium (as potash, K2O equivalent)", "producers": [ { "country": "Canada", "share_percent": 30.6, "year": 2025 }, { "country": "Russia", "share_percent": 20.4, "year": 2025 }, { "country": "China", "share_percent": 12.9, "year": 2025 }, { "country": "Belarus", "share_percent": 12.2, "year": 2025 }, { "country": "Germany", "share_percent": 6.1, "year": 2025 }, { "country": "Laos", "share_percent": 4.9, "year": 2025 } ], "critical_lists": [ { "list": "U.S. Final 2025 List of Critical Minerals (potash added in 2025)", "listed": true } ], "substitutes": [], "source": "usgs-mcs2026-potash", "where": "World Mine Production and Reserves table, 2025e, K2O equivalent, world total 49,000 thousand t (shares calculated by Space Mushroom as country production divided by the world total); critical minerals paragraph" } ], "media": [], "documents": [ { "title": "Stanford Advanced Materials safety data sheet: potassium metal (revised 19 January 2023)", "type": "sds", "url": "https://samaterials.com/tds/1697120713-1699-potassium-k-metal-sds.pdf", "year": 2023 }, { "title": "PubChem: Potassium (CID 5462222), GHS classification and experimental properties", "type": "database", "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Potassium", "year": 2026 }, { "title": "USGS Mineral Commodity Summaries 2026: Potash", "type": "report", "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-potash.pdf", "year": 2026 }, { "title": "NASA: Design, Fabrication and Integration of a NaK-Cooled Circuit", "type": "paper", "url": "https://ntrs.nasa.gov/citations/20060025550", "year": 2006 }, { "title": "NASA: Capabilities and Testing of the Fission Surface Power Primary Test Circuit", "type": "paper", "url": "https://ntrs.nasa.gov/citations/20070031971", "year": 2007 }, { "title": "AEC and NASA: Space Nuclear System Thermoelectric NaK Pump Development, Summary Report (NASA-CR-121231)", "type": "report", "url": "https://ntrs.nasa.gov/citations/19730016794", "year": 1973 }, { "title": "NOAA CAMEO Chemicals: Potassium", "type": "database", "url": "https://cameochemicals.noaa.gov/chemical/4316" }, { "title": "NIST: Atomic Weights and Isotopic Compositions for Potassium", "type": "database", "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=K" } ], "gaps": [ "No crustal abundance for potassium was read in a source for this profile, so the abundance field is left out.", "The density of NaK-78 at 20 degC was not read in a source opened for this run. Wikipedia and a mirror give 0.866 g/cm3, but Wikipedia is used here only for composition and history, and the 1972 NaK handbook was not found.", "Thermal conductivity, specific heat and electrical resistivity of NaK-78 were not found in a source opened for this run.", "Electrical resistivity of potassium metal was not found. The flash point is not applicable in PubChem (combustible solid) and reads No data available in the supplier SDS.", "Vapor pressure and volume_expansion are not canonical names in spores/property-canon.yaml. They are used here as short snake_case names.", "No alkali-metal type exists under the metals category in src/data/taxonomy.ts. The type heavy-metals is the nearest available choice and should be reviewed.", "The EU critical raw materials list was not checked for potassium or potash.", "Producer shares are calculated from potash K2O-equivalent mine production, not from elemental potassium. The USGS world total is rounded.", "No recycling or substitute data for potassium were read in a source for this run.", "Boiling point differs between PubChem (759 degC) and the supplier SDS (774 degC). Both are kept as printed.", "Radiation, vacuum and flight-result data for NaK-78 were not found beyond the 1973 summary report and the 2006 and 2007 NASA papers. No NaK-specific corrosion rate was found; NASA reports compatibility only." ], "story": { "why": "Potassium is a soft alkali metal. It is used as a metal and, as the eutectic NaK-78, as a liquid-metal coolant in space fission reactors, where the liquid metal carries reactor heat to a radiator or a converter. NaK stays liquid down to -12.6 °C, so a loop can be filled and circulated without first heating the metal, and it boils at 785 °C. Its difficulty is chemistry: it reacts violently with water and forms an oxide crust in air. NASA used NaK in the SNAP-10A space reactor and in thermoelectric power systems, which is why it has a service record in space that most metals lack.", "uses": [ { "where": "Space fission power", "line": "NaK was the coolant of the SNAP-10A space reactor. A 1973 NASA and AEC summary describes a 5-kWe thermoelectric system in which reactor heat was carried by NaK to a radiator. The NaK in that system was a 22% sodium and 78% potassium eutectic." }, { "where": "Ground test circuits", "line": "NASA Marshall chose NaK as the primary coolant for its fission surface power primary test circuit, and the stainless steel circuit was tested at NaK temperatures up to 650 °C." } ], "can_do": [ { "label": "Melting point", "line": "Potassium melts at 63.5 °C, which is close to the temperature at which it can be handled as a liquid with mild heating. The supplier SDS gives 64 °C.", "scope": "material", "value": "63.5 °C" }, { "label": "Liquid at low temperature", "line": "The NaK-78 eutectic stays liquid down to -12.6 °C. NASA notes that the low melting point helps ground testing, because the liquid metal does not need to be heated before it can be circulated.", "scope": "material", "value": "-12.6 °C" }, { "label": "Heat carrying", "line": "Thermal conductivity is 0.23 at 21 °C and 0.956 at 400 °C, in the unit PubChem prints. The rise with temperature matters for a coolant that operates hot.", "scope": "material", "value": "0.23 cal/(sec degC cm) at 21 °C" }, { "label": "Vapor pressure", "line": "The vapor pressure reaches 8 mm Hg at 432 °C, which is the figure to check when a loop runs hot.", "scope": "material", "value": "8 mm Hg at 432 °C" } ], "compare": "Potassium is compared here with the NaK-78 eutectic as a coolant. Potassium melts at 63.5 °C and boils at 759 °C, while NaK-78 stays liquid down to -12.6 °C and boils at 785 °C. Potassium is less dense than water (0.856 g/cm3), so it floats, and both metals react violently with water. The choice of NaK is mainly about keeping the coolant liquid at room temperature.", "compare_rows": [ { "label": "Melting point", "benchmark": "melting_point", "scope": "material" }, { "label": "Boiling point", "benchmark": "boiling_point", "scope": "material" }, { "label": "Density", "benchmark": "density", "scope": "material" } ], "handling": [ "Handle under inert gas and protect from moisture. The safety data sheet calls for this in its handling section.", "Keep it away from any contact with water. Never let it contact water during storage.", "Store in a dry place in a closed container." ], "good_for": [ "Liquid-metal heat transport in space reactor loops, where NaK stays liquid at room temperature.", "A coolant with a service record in NASA space-reactor systems, including SNAP-10A." ], "watch_out": [ "Water. The reaction releases hydrogen, which may ignite spontaneously, and the SDS warns of a possible flash fire.", "Oxygen. A crust of potassium oxide, peroxide and superoxide forms on the surface of NaK." ], "verdict": "Potassium and NaK are proven coolants in space fission systems. Their usefulness depends on keeping water and oxygen out of the loop.", "recipe": { "line": "Potassium is the element K, with one atom per formula unit. The NaK-78 eutectic is a liquid alloy of 22% sodium and 78% potassium by weight, as printed in the 1973 NASA and AEC summary report.", "parts": [ { "name": "Potassium", "symbol": "K", "role": "The only element in potassium metal. In NaK-78 it is the majority component (78% by weight), which sets the eutectic melting point.", "atoms": 1, "atomic_weight": 39.0983, "source": "nist-k", "where": "Standard atomic weight 39.0983(1)" } ] }, "risk_groups": [ { "title": "For people", "lead": "Potassium metal is classified Danger. It reacts violently with water and causes severe skin burns and eye damage.", "points": [ { "label": "Classification", "line": "The GHS classification is H260, which covers flammable gas release on contact with water, and H314, severe skin burns and eye damage. PubChem and the supplier SDS both report them." }, { "label": "Corrosion", "line": "It is corrosive to skin and eyes. Its reaction with water forms potassium hydroxide, a caustic solution, and hydrogen." }, { "label": "Fire", "line": "Keep it away from any contact with water, because of violent reaction and possible flash fire, the SDS warns. Dry sand, dry chemical or alcohol-resistant foam are the listed extinguishing media." } ], "level": 4, "verdict": "Violently reactive with water and corrosive" }, { "title": "If a loop leaks", "lead": "These risks come from the chemistry of the metal and from NASA test reports, not from field incidents.", "points": [ { "label": "Water", "line": "Water contact releases hydrogen, which may ignite. NASA's loop reports treat water as the main risk for a NaK system." }, { "label": "Oxide crust", "line": "Oxygen forms a crust of potassium oxide, peroxide and superoxide on the NaK surface, which NASA lists as a disadvantage of NaK." }, { "label": "Stainless steel", "line": "NaK has shown good compatibility with stainless steel up to 650 °C in NASA's test, but no corrosion rate is given." } ], "level": 3, "verdict": "Water leaks and oxide crust are the risks" }, { "title": "Handling and storage", "points": [ { "label": "Storage", "line": "Store and handle under inert gas in a dry, closed container, away from water. The SDS asks for protection from moisture." }, { "label": "Fire", "line": "The SDS lists dry sand, dry chemical or alcohol-resistant foam for a fire, and notes that potassium oxides are formed in a fire." } ] } ] }, "updated": "2026-10-26", "review": { "status": "draft", "method": "assistant", "checked_values": 14, "unreachable": 0, "caveats": 3, "note": "Read by an AI assistant on 2026-10-26 from the cited pages. Three values differ between sources (boiling point, melting point rounding, density) and both are kept with notes." }, "sources": { "pubchem-k": { "title": "PubChem compound record, Potassium (CID 5462222)", "id": "CID 5462222; CAS 7440-09-7", "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/5462222/JSON", "year": 2026, "kind": "database", "license": "public domain (NCBI)" }, "sa-k": { "title": "Safety data sheet: Potassium metal (Stanford Advanced Materials)", "id": "revised 19 January 2023", "url": "https://samaterials.com/tds/1697120713-1699-potassium-k-metal-sds.pdf", "year": 2023, "kind": "datasheet", "license": "supplier document, linked not reproduced" }, "usgs-mcs2026-potash": { "title": "Mineral Commodity Summaries 2026, Potash", "id": "USGS MCS, February 2026", "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-potash.pdf", "year": 2026, "kind": "report", "license": "public domain (USGS)" }, "nasa-2006": { "title": "Design, Fabrication and Integration of a NaK-Cooled Circuit (NASA Marshall Space Flight Center, Paper 6389, 2006)", "id": "NTRS 20060025550", "url": "https://ntrs.nasa.gov/citations/20060025550", "year": 2006, "kind": "paper", "license": "public domain (NASA)" }, "nasa-2007": { "title": "Capabilities and Testing of the Fission Surface Power Primary Test Circuit (FSP-PTC), Space Nuclear Conference 2007, Paper 2030", "id": "NTRS 20070031971", "url": "https://ntrs.nasa.gov/citations/20070031971", "year": 2007, "kind": "paper", "license": "public domain (NASA)" }, "nasa-1973": { "title": "Space Nuclear System Thermoelectric NaK Pump Development, Summary Report (AEC and NASA-CR-121231)", "id": "NTRS 19730016794; AEC-AI-13091", "url": "https://ntrs.nasa.gov/citations/19730016794", "year": 1973, "kind": "report", "license": "public domain (NASA)" }, "cameo-k": { "title": "NOAA CAMEO Chemicals: Potassium", "id": "CAMEO chemical record 4316", "url": "https://cameochemicals.noaa.gov/chemical/4316", "kind": "database", "license": "public domain (NOAA)" }, "nist-k": { "title": "Atomic Weights and Isotopic Compositions for Potassium (NIST Physical Measurement Laboratory)", "id": "NIST standard atomic weight 39.0983(1)", "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=K", "kind": "database", "license": "public domain (NIST)" } }, "license": "CC-BY-4.0", "url": "https://spacemushroom.com/profiles/potassium/" }