Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
A286 Nuclear Applications — ASME III Pressure Vessel and Internals
A286 nuclear applications span pressurized-water reactor (PWR), boiling-water reactor (BWR), and small modular reactor (SMR) pressure-vessel internals, control-rod-drive housings, primary-coolant-pump bolting, and steam-generator hand-hole studs. A286 is permitted in ASME Section III Subsection NB (pressure vessels) and Subsection NF (component supports) per ASTM A453 grade 660 for primary-pressure-bearing service. TorqBolt manufactures A286 nuclear components to ASTM A453 grade 660, ASTM A638 grade 660, AMS 5731-5895, ASME III Subsection NB acceptance, with EN 10204 type 3.2 third-party-witnessed inspection standard for nuclear-safety-critical lots. NRC and IAEA quality-program compliance maintained; nuclear-specific source surveillance welcomed. See parent A286 stainless steel, related sister applications jet engine, gas turbine, aerospace, and product variants A286 bolts, forged bar, flanges.
Why A286 for This Application
Nuclear primary-pressure-bearing service demands material with high yield strength + corrosion resistance + radiation stability + low neutron absorption. A286 satisfies these criteria: retained yield strength to 343 °C (PWR primary-coolant operating temperature 300-330 °C), corrosion resistance in high-temperature borated-water environments, radiation-induced embrittlement resistance at fluence levels typical of reactor pressure-vessel internals, low neutron-absorption cross-section (austenitic stainless matrix), and NACE MR0175 sour-service compliance (some boiling-water reactor applications). For higher-temperature applications (gas-cooled reactors at 750-950 °C), Inconel 617 / Hastelloy XR are required.
A286 Components Used in This Application
- Pressure-vessel internal bolting: ASTM A453 grade 660 Class A studs + matched hex nuts on PWR pressuriser bolting, BWR steam-separator attachment. Operating temp 300-330 °C primary-coolant.
- Control-rod-drive (CRD) housing: Forged A286 bar machined to CRD housing components — CRD housing supports, latch-mechanism brackets. ASME III Subsection NB acceptance.
- Primary-coolant-pump bolting: Heavy-hex A286 stud bolts + matched hex nuts on PWR primary-coolant pump (RCP) casing bolting. M48-M64 sizes typical for 1500 psig service.
- Steam-generator hand-hole stud: Stud bolts + matched A286 nuts on steam-generator hand-hole man-way bolting. Periodic access for inspection during refuelling outages.
- Reactor-vessel internal supports: ASTM A638 grade 660 forged A286 plates / brackets supporting reactor-vessel internals — fuel-bundle alignment fixtures, control-rod guide tubes.
- Pressuriser / surge-tank bolting: M30-M48 stud bolts + nuts on pressuriser flange bolting. Operating temp 343 °C.
- Safety-injection accumulator bolting: M16-M30 hex bolts + nuts on safety-injection accumulator vessel flanges. Standby service with infrequent thermal cycling.
- Instrumentation tube hangers: A286 threaded rod (M10-M16) as instrumentation tube hangers + supports inside reactor pressure vessel. Long-length thermal-expansion accommodation.
Governing Standards & Specifications
- ASTM A453 grade 660 Class A — High-temperature bolting material — the canonical nuclear bolt spec.
- ASTM A638 grade 660 Type 1/2 — Forged stock for nuclear pressure-vessel internal forgings.
- ASME Section III Subsection NB — Pressure-vessel components — primary-pressure-bearing acceptance.
- ASME Section III Subsection NF — Component supports — non-pressure-bearing nuclear acceptance.
- AMS 5731 / 5732 — Bar / forging for fastener manufacture.
- EN 10204 type 3.2 — Third-party-witnessed inspection — standard for nuclear-safety-critical lots.
- NACE MR0175 / ISO 15156-3 — Sour-service compliance for some boiling-water reactor applications.
- 10 CFR 50 Appendix B — NRC nuclear quality-program compliance — requires lot-traceability and approved-vendor status.
- ASME Section II — Material specification reference for ASTM A453 grade 660 acceptance.
- ASME NCA-3800 — Quality assurance program requirements for nuclear-safety-related applications.
Manufacturing & Quality Process
- VIM-VAR melt sourcing: AMS 5731 / 5732 chemistry from NRC-approved nuclear mills. Double-melted (VIM + VAR) for inclusion control. ASME III chemistry compliance verified.
- Forging route preferred: ASTM A638 grade 660 forging-grade microstructure for nuclear components — superior grain-flow continuity vs hot-rolled.
- Solution treatment: Vacuum heat-treat 1650 °F (Type 1) or 1800 °F (Type 2). 1 h per inch of section, oil-quench.
- Precipitation aging: 1325 °F (718 °C) for 16 hours, air-cool. ASME III hardness window 24-32 HRC.
- Ultrasonic + LPI inspection: 100 % UT per ASTM A388 + LPI per ASTM E1417 — Class 1 sensitivity for safety-critical nuclear components.
- Charpy V-notch impact testing: Required per ASME III for nuclear pressure-bearing components — Charpy at 0 °C, +50 °C, and operating temperature.
- EN 10204 type 3.2 third-party witness: Standard for nuclear-safety-critical lots — Lloyds, BV, DNV, TÜV witness present at heat-treat release and tensile testing.
- Lot serialization 1-N + traceability: Per 10 CFR 50 Appendix B + ASME NCA-3800 — every component lot traceable to VIM-VAR melt heat number.
Material Selection by Service Condition
- PWR pressuriser bolting (300-343 °C): A286 grade 660 Class A — the canonical PWR pressuriser bolting material per ASME III NB. Heavy-hex stud bolts + nuts, EN 10204 3.2 third-party witness.
- BWR steam-separator (290 °C): A286 grade 660 Class A — matched A286 stud bolts + nuts. NACE MR0175 hardness verification for some BWR variants.
- CRD housing (RCS pressure boundary): A286 forged bar (ASTM A638 grade 660 Type 2) — Type 2 for higher stress-rupture resistance during accident-condition transients.
- Primary-coolant pump bolting: Heavy-hex A286 grade 660 stud bolts (M48-M64). 1500 psig service. ASME PCC-1 preload calculation; matched A286 nuts and washers.
- Reactor pressure-vessel internals: ASTM A638 grade 660 forged plates / brackets. Radiation-induced-embrittlement-resistant; Charpy V-notch tested at end-of-life fluence.
- Gas-cooled reactor (≥ 750 °C): NOT A286 — Inconel 617, Hastelloy XR, Haynes 230 required for high-temperature gas-cooled reactor service.
A286 Nuclear Applications — ASME III Pressure Vessel and Internals — Frequently Asked Questions
Is A286 permitted in ASME Section III for nuclear pressure-bearing service?
Yes — ASTM A453 grade 660 is permitted in ASME Section III Subsection NB (pressure vessels) and Subsection NF (component supports) for primary-pressure-bearing nuclear applications. Used in PWR pressurisers, BWR steam-separators, primary-coolant-pump casings.
What's the operating temperature range for A286 nuclear applications?
Continuous service: -40 °C to ~700 °C. Standard PWR primary-coolant temperature 300-330 °C; A286 retains > 90 % of room-temperature yield at this temperature. For gas-cooled reactor applications at 750-950 °C, Inconel 617 / Hastelloy XR are required.
Does A286 require Charpy V-notch testing for nuclear?
Yes — ASME III nuclear pressure-bearing service requires Charpy V-notch impact testing per ASTM E23 at 0 °C, +50 °C, and operating temperature. Typical A286 Charpy V-notch values: ≥ 27 J at 0 °C, ≥ 35 J at operating temperature.
What QA program applies to A286 nuclear components?
10 CFR 50 Appendix B (NRC nuclear quality-program), ASME NCA-3800 (quality assurance for nuclear-safety-related), and EN 10204 type 3.2 third-party witness inspection. Manufacturer must hold approved-vendor status with utility / OEM.
Can A286 components be welded in nuclear service?
Yes — TIG welding with matching A286 welding rod (AMS 5853). Post-weld solution-treatment + aging required for full-strength weld zone. ASME IX welding-procedure qualification per nuclear-specific paragraph QW-153 to QW-157.
What's the radiation tolerance of A286?
A286 retains useful properties at fluence levels typical of reactor-pressure-vessel internals (10²² n/cm² thermal). Radiation-induced embrittlement is monitored in nuclear surveillance programs; A286 typically meets end-of-life acceptance criteria at 60-year licensed operating life.
Are A286 nuclear components NACE MR0175 compliant?
Yes — when supplied with hardness ≤ HRC 35 (HV ≤ 327) per NACE MR0175 / ISO 15156-3. Some BWR applications require sour-service compliance for water-chemistry control. Specify on PO; each heat receives Vickers traverse before release.
Is A286 used in small modular reactors (SMR)?
Yes — A286 is being adopted by SMR vendors (NuScale, Rolls-Royce SMR, GE-Hitachi BWRX-300, Holtec SMR-300) for pressure-vessel internal bolting and CRD components. SMR-specific qualification programs are in progress for novel SMR pressure profiles and operating temperatures.
What's the lead time on ASME III nuclear A286 components?
Standard A286 bar / forgings: 12-16 weeks from heat release. ASME III certified components with EN 10204 3.2 third-party witness: 16-24 weeks. Custom-drawing parts: 20-32 weeks. NRC-specific approved-vendor lots: confirmed 4-week minimum lead time, plan accordingly.
Related Applications & A286 Reference
Other A286 application reference pages: jet engine fasteners · gas turbine applications · nuclear applications · aerospace fasteners.
Canonical A286 reference: A286 chemical composition · A286 mechanical properties · A286 heat treatment · AMS / ASTM specifications hub · alloy comparisons (vs Inconel 718 · vs Waspaloy).
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