Stainless Steel Spiral Coil Tube for Integrated Pressurized Reactor Direct-Cycle Steam Generator
Product Overview
The Stainless Steel Spiral Coil Tube (Product No. 1716) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a high-performance tubular product engineered specifically for the direct-cycle steam generator of Integrated Pressurized Reactor (IPR) systems. This coil tube serves as the core heat exchanger element in compact nuclear reactor designs, where primary coolant water flows through the spiral coil tubes to generate steam directly, eliminating the need for a secondary loop.
Unlike conventional U-tube or straight-tube heat exchangers, the spiral coil tube geometry provides superior thermohydraulic performance, enhanced natural circulation driving force, and improved resistance to two-phase flow instabilities — critical requirements for the safe and efficient operation of integrated pressurized reactors. The helical geometry promotes helical secondary flow within the tube, intensifying convective heat transfer and reducing the likelihood of flow-induced vibrations and flow instability phenomena.
Material & Properties
The coil tubes are fabricated from austenitic stainless steel grades selected for exceptional corrosion resistance, high-temperature mechanical strength, and excellent weldability in nuclear-grade service environments. The primary material specifications are as follows:
- Primary Grade: 304L (UNS S30403) — Low-carbon austenitic stainless steel with superior resistance to intergranular corrosion
- Alternative Grade: 316L (UNS S31603) — Molybdenum-enhanced austenitic stainless steel for elevated chloride environments
- Nuclear-Grade Option: 316L(N) — Certified nuclear-grade stainless steel meeting ASME III requirements
Key Material Properties:
- Corrosion resistance in high-temperature water and steam environments up to 350°C
- Good thermal conductivity (~16.3 W/m·K for 304L) ensuring efficient heat transfer
- Low thermal expansion coefficient minimizing thermal stress during operational transients
- Excellent resistance to stress corrosion cracking (SCC) under controlled impurity conditions
- Non-magnetic austenitic structure suitable for nuclear instrumentation environments
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Category | Spiral Coil Tube (盘管) | — |
| Product Number | 1716 | — |
| Outer Diameter (OD) | 14.0 mm – 25.4 mm (configurable) | ASME B31.11 |
| Wall Thickness | 1.0 mm – 2.0 mm | ASME B31.11 |
| Helix Diameter | 200 mm – 600 mm | Custom design |
| Helix Pitch | 20 mm – 80 mm | Custom design |
| Coil Length (per stack) | Up to 12,000 mm | — |
| Surface Finish | Pickled & Passivated (Ra ≤ 0.4 μm) | ASTM A967 |
| Pressure Rating | Up to 17.5 MPa (Design) | ASME III |
| Temperature Range | -196°C to +350°C | — |
| Material Grade | 304L / 316L / 316L(N) | ASTM A213 / ASTM A269 |
| Welding Method | Orbital TIG (GTAW) / Autogenous Welding | ASME V |
| Heat Treatment | Solution Annealing (1050°C – 1150°C) | ASTM A213 |
| Design Life | ≥ 40 years | ASME III |
Manufacturing Process
The production of nuclear-grade spiral coil tubes follows a rigorous, multi-stage manufacturing protocol ensuring dimensional accuracy, metallurgical integrity, and weld quality in accordance with applicable nuclear codes:
- Raw Material Selection & Verification: Mill-certified stainless steel seamless tube stock (ASTM A213 TP304L/TP316L) is procured with full chemical analysis (including trace impurity control for C, N, S, and P) and mechanical property certification.
- Cold Forming & Coil Winding: Straight seamless tubes are cold-formed into precise helical geometries using CNC-controlled coil winding machines. The forming process maintains dimensional tolerances within ±0.1 mm for OD and ±0.05 mm for wall thickness, with controlled strain rates to prevent work hardening beyond specified limits.
- Heat Treatment (Solution Annealing): Formed coils undergo solution annealing at 1050°C–1150°C followed by controlled cooling to relieve residual stresses, restore full austenitic structure, and ensure minimum required elongation (≥ 35% per ASTM A213).
- Pickling & Passivation: Chemical cleaning removes mill scale and forming residues, followed by passivation treatment per ASTM A967 to establish a protective chromium oxide film. Surface roughness is verified to Ra ≤ 0.4 μm.
- Orbital TIG Welding: All weld joints (coil-to-header connections) are fabricated using automated orbital Gas Tungsten Arc Welding (GTAW) with argon shielding. Weld parameters are optimized to ensure full penetration, minimal heat-affected zone (HAZ), and freedom from defects.
- Non-Destructive Examination (NDE):strong> Welds undergo 100% Visual Examination (VT), 100% Dye Penetrant Testing (PT), and Radiographic Testing (RT) or Ultrasonic Testing (UT) per ASME Section V. Helical coils are inspected for geometric conformity using coordinate measurement systems.
- Hydrostatic Pressure Testing: Each coil assembly is hydrostatically tested at 1.5 times the design pressure (typically 26.25 MPa) and held for a minimum of 10 minutes with no visible leakage or permanent deformation.
- Final Dimensional Inspection & Documentation: Comprehensive dimensional verification, surface finish measurement, and material traceability documentation are compiled into the final product data package.
Applications
Primary Application: Integrated Pressurized Reactor (IPR) Steam Generator
The principal application of this spiral coil tube is as the heat exchange element in the Direct-Cycle Steam Generator (DCSG) of Integrated Pressurized Reactor systems. In this configuration:
- The spiral coil tubes carry primary coolant (high-temperature pressurized water) and transfer thermal energy to generate secondary steam directly
- The helical geometry promotes enhanced natural circulation, providing passive safety features without mechanical pumps
- The compact stacked coil arrangement maximizes heat transfer surface area within the reactor vessel footprint
- The design is optimized for thermohydraulic stability under normal operation and transient conditions, including startup, load follow, and accident scenarios
Additional Applications:
- Small Modular Reactor (SMR) heat exchanger components
- Advanced Gas-Cooled Reactor (AGR) intermediate heat exchanger tubes
- High-temperature process heat exchangers in petrochemical and power generation
- Supercritical water reactor (SCWR) prototyping
- Compact nuclear desalination systems
Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ASME III / NB | National Board registration for nuclear components |
| ASME BPV Code | Boiler and Pressure Vessel Code compliance |
| ISO 9001:2015 | Quality Management System certification |
| ISO 14001 | Environmental Management System |
| ISO 45001 | Occupational Health & Safety Management |
| ISO 3834-2 | Quality requirements for welding of metallic materials |
| EN 10204 3.1 | Inspection documentation certification |
| ASTM A213 | Standard specification for austenitic stainless steel seamless tube |
| ASTM A269 | Standard specification for austenitic stainless steel welded tube |
| ASTM A967 | Chemical cleaning and passivation of stainless steel parts |
Unique Selling Points
- Thermohydraulic Optimization: Spiral coil geometry designed through advanced thermohydraulic simulation (including two-phase flow instability analysis) to ensure stable operation across the full power range, from low-flow startup to full-power operation and beyond-boiling conditions.
- Nuclear-Grade Quality: Full traceability from raw material mill certificates through manufacturing, NDE, and final inspection, meeting the most stringent nuclear industry quality requirements.
- Compact & Efficient Design: Stacked spiral coil configuration achieves maximum heat transfer surface density, enabling compact reactor vessel design while maintaining adequate heat transfer margins.
- Resistance to Flow Instabilities: Helical geometry inherently suppresses density-wave oscillations and thermohydraulic instabilities that plague straight-tube designs in direct-cycle configurations.
- Passive Safety Compatibility: Designed to function effectively under natural circulation conditions without requiring active mechanical systems for coolant flow, supporting inherent safety design philosophy.
- Custom Engineering Capability: Full design flexibility in helix diameter, pitch, tube dimensions, and coil length to accommodate specific reactor design requirements and thermohydraulic performance targets.
Technical Note: The design and qualification of spiral coil tubes for IPR direct-cycle steam generators requires rigorous evaluation of two-phase flow instability phenomena, including density-wave oscillations (DWO), thermally induced oscillations, and flow-induced vibrations. Advanced system-level thermohydraulic analysis codes and component-level CFD (Computational Fluid Dynamics) simulations are employed to ensure design margins exceed regulatory requirements under all credible operating and accident scenarios.
Manufacturer Information
Wenzhou Jixing Metal Materials Co., Ltd. — A specialized manufacturer of stainless steel tubular products with expertise in precision coil forming, nuclear-grade welding, and heat exchanger component fabrication. The company maintains comprehensive quality systems and possesses the technical capability to deliver spiral coil tube assemblies meeting international nuclear industry standards for integrated reactor applications.