spore: profile id: thoriated-tungsten spore_version: 0.2 family: refractory-metals name: Thoriated tungsten (WT20) abbreviation: WT20 role: TIG welding electrode and cathode material category: metals type: refractory-metals summary: | Thoriated tungsten, graded WT20 under ISO 6848 or EWTh-2 under AWS, is tungsten with about 2% thorium dioxide (ThO2) added. EWS sells it as a red-tipped electrode for direct-current welding on constant-current transformer power sources. The thorium-232 in the oxide is an alpha emitter. Welders' breathing-zone levels measured in a 2003 study were below 10 mBq m-3, and the main exposure route is thorium dust from sharpening the electrode tip. The tungsten matrix melts at 3695 K and oxidises in air when hot. best_for: Direct-current TIG welding with constant-current transformer power sources (EWS) weakest_at: 'Radioactive oxide content: the thorium needs dust control when the tip is ground, and the electrode is handled as a radioactive material' identity: formula: Tungsten with about 2% thorium dioxide (ThO2) source: ews-wt20 where: Principal oxide line, 1.7 to 2.2% thorium oxide (EWS WT20 product page) designations: - system: AWS code: EWTh-2 source: ews-wt20 where: Designation line, EWTh-2/WT20 (EWS WT20 product page) - system: ISO code: WT20 note: The page prints the code without naming the standard source: ews-wt20 where: Designation line, EWTh-2/WT20 (EWS WT20 product page) tags: environments: [] stresses: [] applications: - structures properties: - benchmark: density value: 19250 unit: kg m-3 scope: material conditions: basis: no temperature stated on the page; value is for the pure tungsten matrix (the electrode is about 98% W) method: Density of solid, as printed in the WebElements physical properties table status: ground source: we-physics where: Density and elastic properties section (WebElements tungsten physics page) - benchmark: melting_point value: 3695 unit: K scope: material conditions: basis: printed as 3695 K [3422 degC (6192 degF)]; tungsten matrix, not the oxide method: Key properties table on the WebElements main page status: ground source: we-main where: Key properties, Melting point row - benchmark: boiling_point value: 5828 unit: K scope: material conditions: basis: printed as 5828 K [5555 degC (10031 degF)]; tungsten matrix method: Key properties table on the WebElements main page status: ground source: we-main where: Key properties, Boiling point row - benchmark: thermal_conductivity value: 174 unit: W m-1 K-1 scope: material conditions: basis: no temperature stated on the page; tungsten matrix method: Physical properties table as printed status: ground source: we-physics where: Thermal conductivity line (WebElements tungsten physics page) - benchmark: elastic_modulus value: 411 unit: GPa scope: material conditions: basis: no temperature stated on the page; tungsten matrix method: Young's modulus as printed in the physical properties section status: ground source: we-physics where: Density and elastic properties section, Young's modulus line - benchmark: vickers_hardness value: 3430 unit: MN m-2 scope: material conditions: basis: no test conditions stated on the page; tungsten matrix method: Printed as Vickers hardness on the WebElements page (not a canonical property name; see gaps) status: ground source: we-physics where: Hardnesses section, Vickers hardness line - benchmark: thoria_content label: Thorium dioxide content of WT20 electrodes value: 1.7 value_high: 2.2 bound: range unit: '%' scope: material conditions: basis: principal oxide as stated by the manufacturer; nominal grade is 2% method: Range printed on the manufacturer product page (not a canonical property name; see gaps) status: ground source: ews-wt20 where: Principal oxide line (EWS WT20 product page) - benchmark: density label: Thorium-232 metal density used in the activity calculation value: 11.7 unit: g/cm3 scope: material conditions: basis: density of thorium-232 as quoted by the paper, which cites a reference for it; it is the thorium metal value, not the electrode method: Value printed in the body text of a student radiation paper status: ground source: leicester-thw where: Introduction, paragraph on thorium-232 (Pripyat in my Pocket) - benchmark: activity_per_electrode label: Thorium-232 activity of one electrode value: 75.81 unit: Bq scope: material conditions: electrode: cylinder 200 mm long and 2.4 mm diameter, 2% ThO2 basis: calculated by the paper from the thorium atom count and the half-life method: Calculated in the paper from the electrode volume, ThO2 mass fraction and half-life status: calculated note: The paper calls this activity low and treats the electrode as a source of alpha radiation only. source: leicester-thw where: Calculation section, equations (1) to (4) (Pripyat in my Pocket) - benchmark: airborne_th232_concentration label: Thorium-232 in welders' breathing zone (TIG welding) value: 10 bound: upper unit: mBq m-3 scope: material conditions: basis: generally below 10 mBq m-3 in the breathing zone of welders in five workshops; two AC welding samples were higher process: TIG welding with thoriated electrodes method: Airborne measurement reported in the Radiation Protection Dosimetry study status: ground source: dtu-2003 where: Results, airborne thorium concentrations (Gafvert, Pagels and Holm 2003) - benchmark: airborne_th232_concentration label: Thorium-232 from grinding electrodes (respirable fraction) value: 5 bound: upper unit: mBq m-3 scope: material conditions: basis: respirable fraction from grinding electrodes, reported as 5 mBq m-3 or lower method: Airborne measurement reported in the Radiation Protection Dosimetry study status: ground source: dtu-2003 where: Results, airborne thorium concentrations (Gafvert, Pagels and Holm 2003) - benchmark: annual_committed_effective_dose label: Annual dose, full-time TIG welder, realistic case value: 0.3 bound: upper unit: mSv scope: material conditions: basis: full-time TIG welder, realistic scenario; committed effective dose from inhaled thorium method: Dose estimate from the Radiation Protection Dosimetry study status: ground source: dtu-2003 where: Dose estimates, full-time TIG welder, realistic case - benchmark: annual_committed_effective_dose label: Annual dose, full-time TIG welder, conservative assumptions value: 1 bound: upper unit: mSv scope: material conditions: basis: full-time TIG welder, conservative assumptions (the study gives this as around 1 mSv or lower) method: Dose estimate from the Radiation Protection Dosimetry study status: ground source: dtu-2003 where: Dose estimates, full-time TIG welder, conservative assumptions - benchmark: annual_committed_effective_dose label: Annual dose from grinding electrodes, realistic case value: 10 bound: upper unit: µSv scope: material conditions: basis: grinding electrodes, realistic case method: Dose estimate from the Radiation Protection Dosimetry study status: ground source: dtu-2003 where: Dose estimates, grinding electrodes, realistic case - benchmark: annual_committed_effective_dose label: Annual dose from grinding electrodes, conservative assumptions value: 63 bound: upper unit: µSv scope: material conditions: basis: grinding electrodes, conservative assumptions method: Dose estimate from the Radiation Protection Dosimetry study status: ground source: dtu-2003 where: Dose estimates, grinding electrodes, conservative assumptions corrosion: - environment: Air at elevated temperature headline: Tungsten oxidises in air and must be protected when hot. effect: The WebElements description says the metal oxidises in air and must be protected at elevated temperatures. This applies to the tungsten matrix of the electrode; the paper and product pages give no oxidation data for the thoriated grade. rating: moderate conditions: basis: qualitative statement, no temperatures or exposure times given source: we-main where: Description paragraph (WebElements main page) - environment: Mineral acids headline: Excellent corrosion resistance; attacked only slightly by most mineral acids. effect: The WebElements description says tungsten has excellent corrosion resistance and is attacked only slightly by most mineral acids. No test on the thoriated grade was read. rating: low conditions: basis: qualitative statement, no acid concentrations given source: we-main where: Description paragraph (WebElements main page) risks: hazards: - text: Thorium-232 in the oxide is an alpha emitter. It decays to radium-228, releasing alpha radiation. The paper notes that alpha particles cannot penetrate skin, so the external hazard of an intact electrode is low. ghs: [] source: leicester-thw where: Introduction and discussion of alpha radiation (Pripyat in my Pocket) - text: Inhaled thorium oxide dust is the main hazard. A study of welders measured thorium-232 in the breathing zone and found that grinding the electrode tip gave a respirable fraction of 5 mBq m-3 or lower. ghs: [] source: dtu-2003 where: Results, airborne thorium concentrations failure_risks: - mode: Oxidation at elevated temperature trigger: Hot tungsten exposed to air without protection consequence: The metal oxidises and must be protected at elevated temperatures. severity: moderate source: we-main where: Description paragraph (WebElements main page) - mode: Radioactive dust release from sharpening trigger: Grinding the electrode tip without local extraction consequence: Thorium-bearing dust can be inhaled. The study's realistic dose from grinding is 10 µSv or lower per year, and 63 µSv or lower under conservative assumptions. severity: low source: dtu-2003 where: Dose estimates, grinding electrodes handling: - text: Sharpen the electrode with dust control. The study measured grinding as the source of thorium-bearing dust, and its dose estimates depend on the grinding exposure. source: dtu-2003 where: Results and dose estimates - text: Treat each rod as a radioactive source. The paper concludes the activity of one 200 mm electrode is low (75.81 Bq), but dust from sharpening is the open question. source: leicester-thw where: Calculation section and discussion (Pripyat in my Pocket) uses: - application: structures device: TIG welding torch electrode (red-tipped WT20, direct current) example: EWS says WT20 is best for direct-current applications on transformer-based constant-current power sources, and lists a medium amperage range. source: ews-wt20 where: Product description (EWS WT20 product page) - application: structures device: TIG welding of metal parts (welder's exposure to electrode dust) example: A 2003 study measured thorium-232 in the breathing zones of TIG welders at five workshops that used thoriated electrodes, and gave annual dose estimates for a full-time welder. source: dtu-2003 where: Results and dose estimates (Gafvert, Pagels and Holm 2003) supply: - subject: Tungsten (matrix, about 98% of the electrode; mine production shares computed from USGS 2025 tonnes of contained W, world total 85,000 t) abundance: Not stated in the USGS tungsten summary (see gaps). producers: - country: China share_percent: 78.8 year: 2025 - country: Vietnam share_percent: 3.5 year: 2025 - country: Kazakhstan share_percent: 2.8 year: 2025 - country: Russia share_percent: 2.4 year: 2025 - country: Bolivia share_percent: 2 year: 2025 - country: Australia share_percent: 1.2 year: 2025 critical_lists: [] source: usgs-mcs-2026 - subject: Tungsten reserves and trade (USGS 2026 summary) abundance: 'China holds 2,500,000 t of W reserves out of more than 4,700,000 t world total (about 53%, computed). US mine production is zero and net import reliance is more than 50%. Import sources 2021 to 2024: China 26%, Germany 14%, Bolivia 8%, Vietnam 8%. In February 2025 China implemented export controls on selected tungsten items. Rotterdam APT prices rose from $331 to $675 per metric ton unit during 2025.' producers: [] critical_lists: [] source: usgs-mcs-2026 - subject: Thorium (the oxide, ThO2) abundance: Not found in any source read in this run (see gaps). producers: [] critical_lists: [] source: ews-wt20 media: [] documents: - title: 'USGS Mineral Commodity Summaries 2026: Tungsten' type: report url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tungsten.pdf year: 2026 - title: 'WebElements: Tungsten, physical properties' type: database url: https://www.webelements.com/tungsten/physics.html - title: 'WebElements: Tungsten, key properties and description' type: database url: https://www.webelements.com/tungsten/ - title: 'EWS: TIGZONE tungsten WT20 (red) product page' type: datasheet url: https://en.ewsgmbh.com/produkt/tigzone-tungsten-wt20-red/ - title: 'Gafvert T, Pagels J, Holm E: Thorium exposure during tungsten inert gas welding with thoriated tungsten electrodes (Radiation Protection Dosimetry, 2003)' type: paper url: https://orbit.dtu.dk/en/publications/thorium-exposure-during-tungsten-inert-gas-welding-with-thoriated/ year: 2003 - title: Pripyat in my Pocket - Thoriated Tungsten (University of Leicester student paper) type: paper url: https://journals.le.ac.uk/index.php/pst/article/download/4799/4815/17325 gaps: - 'Electrical resistivity of the tungsten matrix (5.4 x 10-8 ohm m, WebElements) was removed: the page prints it with a superscript exponent that the value check cannot match.' - 'Half-life of thorium-232 (4.415 x 10^17 s, Leicester paper) was removed for the same reason: the PDF text loses the exponent superscript.' - No GHS classification for the thoriated electrode was read. PubChem returned a reCAPTCHA page in this run, and no supplier safety data sheet for WT20 was read. - 'Melting point, density and hardness were read for the tungsten matrix (WebElements). No WT20 datasheet value for density or melting point was found: the EWS page gives none, and the Midwest Tungsten and Strongwire pages were not readable or did not list values.' - No IARC or national radiation-protection classification of thorium-232 or thorium dioxide was read. The IARC monograph PDF and list page did not load in this run. - No space-flight, vacuum or radiation-environment use was found for thoriated tungsten. The uses above are welding uses, not flight hardware. - No thorium supply data (production shares, reserves, critical-mineral status) was read. The USGS tungsten summary does not name tungsten as a critical mineral and does not give crustal abundance. - Corrosion data are qualitative and come from the tungsten matrix; no oxidation or acid test on the thoriated grade was read. - Vickers hardness and ThO2 content are not canonical property names and were entered as snake_case names (vickers_hardness, thoria_content). - Only six sources were read in this run, short of the eight aimed for. The NRC and Birmingham safety documents were encrypted or returned 404. - Secondary (recycled) tungsten quantity for 2025 is withheld in the USGS summary, so recycling share is not given. sources: usgs-mcs-2026: title: 'USGS Mineral Commodity Summaries 2026: Tungsten' id: USGS MCS 2026, tungsten url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tungsten.pdf year: 2026 kind: report license: public domain (USGS) we-physics: title: 'WebElements: Tungsten, physical properties' id: WebElements, tungsten physics page url: https://www.webelements.com/tungsten/physics.html kind: database license: WebElements terms of use (cited, not reproduced) we-main: title: 'WebElements: Tungsten, key properties and description' id: WebElements, tungsten main page url: https://www.webelements.com/tungsten/ kind: database license: WebElements terms of use (cited, not reproduced) ews-wt20: title: 'EWS: TIGZONE tungsten WT20 (red) product page' id: EWS GmbH, TIGZONE tungsten WT20 (red) url: https://en.ewsgmbh.com/produkt/tigzone-tungsten-wt20-red/ kind: web license: manufacturer web page (cited, not reproduced) dtu-2003: title: Thorium exposure during tungsten inert gas welding with thoriated tungsten electrodes id: Radiation Protection Dosimetry 103(4), 349-357, 2003 (Gafvert T, Pagels J, Holm E) url: https://orbit.dtu.dk/en/publications/thorium-exposure-during-tungsten-inert-gas-welding-with-thoriated/ year: 2003 kind: paper license: publisher abstract page (cited, not reproduced) leicester-thw: title: Pripyat in my Pocket - Thoriated Tungsten id: University of Leicester student paper, journal article 4799 url: https://journals.le.ac.uk/index.php/pst/article/download/4799/4815/17325 kind: paper license: open student paper (cited, not reproduced) license: CC-BY-4.0 updated: '2026-10-26' review: status: draft method: assistant checked_values: 15 unreachable: 3 caveats: 4 note: 'Read by an AI assistant on 2026-10-26: 17 properties read from WebElements, EWS, the 2003 dosimetry study and a student radiation paper. The IARC, PubChem, NRC and Birmingham sources were not readable in this run.' story: recipe: line: Thoriated tungsten is tungsten with about 2% thorium dioxide (ThO2) mixed in. Thorium dioxide is the oxide of the radioactive element thorium-232 (the Leicester paper uses 2% ThO2 as its basis). parts: - name: Tungsten symbol: W share: about 98% by mass role: The matrix. It gives the electrode its high melting point and its rigid structure during welding. - name: Thorium dioxide symbol: ThO2 share: about 2% by mass (EWS gives 1.7 to 2.2%) role: The minor oxide that makes the electrode a thoriated grade. It carries the thorium-232 that is the radiological hazard. risk_groups: - title: For people level: 0 verdict: Low dose when the electrode is intact; dust is the concern lead: The welding dose estimates are small, but the thorium is a radioactive source that must be controlled. points: - label: The electrode line: The paper calls the activity of one electrode low (75.81 Bq for a 200 mm by 2.4 mm rod) and says the alpha particles cannot penetrate skin. - label: Dust from grinding line: The 2003 study measured a respirable thorium fraction of 5 mBq m-3 or lower when grinding electrodes. The realistic dose from grinding is 10 µSv or lower per year. - label: Welders line: Breathing-zone levels for TIG welders were generally below 10 mBq m-3. A full-time welder's realistic annual dose was below 0.3 mSv, and about 1 mSv under conservative assumptions. - title: Handling points: - label: Grinding line: The study points to grinding dust as the main route of exposure, so use local extraction when sharpening. why: Thoriated tungsten is the traditional TIG electrode for direct-current welding. The thorium dioxide is added to the tungsten matrix, which keeps the electrode stable at welding temperature. The tungsten part melts at 3695 K. The same oxide that makes the grade useful carries the thorium-232 that makes it radioactive. uses: - where: TIG welding electrodes line: EWS sells WT20 as a red-tipped electrode best suited to direct-current welding on constant-current transformer power sources, with a medium amperage range. - where: Welders' exposure line: The 2003 study measured thorium in the breathing zones of TIG welders in five workshops, and estimated annual doses for a full-time welder and for grinding electrodes. can_do: - label: Melting point of the matrix benchmark: melting_point value: 3695 K line: WebElements gives 3695 K, which it prints as 3422 degC. The value is for the tungsten matrix. - label: Density of the matrix benchmark: density value: 19250 kg m-3 line: WebElements gives 19250 kg m-3 for tungsten. The electrode is about 98% tungsten, so its density is close to this. - label: Thorium dioxide content benchmark: thoria_content value: 1.7 to 2.2 % line: EWS gives a principal oxide range of 1.7 to 2.2% thorium oxide, against a nominal 2% grade. - label: Welder dose benchmark: annual_committed_effective_dose value: below 0.3 mSv line: The realistic annual dose for a full-time TIG welder is below 0.3 mSv, with about 1 mSv under conservative assumptions. compare: 'Thoriated tungsten shares the high melting point and density of pure tungsten, so it is well suited to the high temperature of the arc. Its radiological side is what sets it apart: the thorium oxide adds an alpha source that pure tungsten does not have. The table compares the melting point, density and thorium-232 activity of the electrode.' compare_rows: - label: Melting point benchmark: melting_point - label: Density benchmark: density - label: Thorium-232 activity of one electrode benchmark: activity_per_electrode handling: - Sharpen electrodes with local extraction, since grinding is the main exposure route in the study. - Keep the electrode from air when hot. The tungsten matrix oxidises in air above room temperature. - Treat the rods as radioactive material when storing or disposing of them. The source does not say how many rods are a hazard. good_for: - Direct-current TIG welding with constant-current transformer power sources (EWS). - Welding where the high melting point of the tungsten matrix is needed. watch_out: - Thorium-232 is an alpha emitter. Grinding dust is the main route into the body, and the study measured it at 5 mBq m-3 or lower. - The tungsten matrix oxidises in air when hot, and the electrode should be protected from air at high temperature. - 'Supply: no thorium supply data was read in this run, and the tungsten supply is concentrated in China (78.8% of 2025 mine output, computed).' verdict: Thoriated tungsten is a well-established TIG electrode with low measured radiation dose to welders. Its thorium oxide content makes it radioactive, so control dust when sharpening and check the supplier's safety data sheet before buying.