Stainless Steel Cooling Coil Tube — Nuclear Island Equipment Cooling Water System
1. Product Overview
The Stainless Steel Cooling Coil Tube (Product Code: JX-CT-857) is a precision-engineered heat exchange component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. for use in Nuclear Island (NI) equipment cooling water systems. These coil tubes serve as critical primary heat transfer elements within condensers, feedwater preheaters, and auxiliary cooling loops in pressurized water reactor (PWR) and boiling water reactor (BWR) nuclear power plants. The product is designed to meet the rigorous safety, reliability, and corrosion resistance demands of nuclear-grade applications, where failure can result in cascading operational hazards.
Based on extensive post-incident analysis of cooling coil tube leakage events in nuclear island cooling water systems, this product incorporates enhanced metallurgical design, improved manufacturing tolerances, and advanced quality assurance protocols to mitigate known failure modes including stress corrosion cracking (SCC), flow-induced vibration (FIV), and erosion-corrosion degradation.
2. Material & Properties
The coil tubes are fabricated from austenitic and super-austenitic stainless steel grades specifically selected for nuclear service environments. The following material grades are available:
- SAE 304 / 0Cr18Ni9 (UNS S30400) — General-purpose austenitic stainless steel with excellent corrosion resistance in non-chloride environments.
- SAE 304L / 022Cr17Ni12Mo2 (UNS S30403) — Low-carbon variant resistant to sensitization during welding operations.
- SAE 316L / 022Cr17Ni12Mo2 (UNS S31603) — Molybdenum-bearing grade offering superior resistance to pitting and crevice corrosion in chloride-containing cooling water.
- SAE 321 / 06Cr18Ni11Ti (UNS S32100) — Titanium-stabilized grade for high-temperature service resistance.
- SAE 347 / 06Cr19Ni10Nb (UNS S34700) — Niobium-stabilized variant for elevated temperature applications.
2.1 Key Mechanical Properties (Annealed Condition)
| Property | SAE 304L | SAE 316L | SAE 321 | SAE 347 |
|---|---|---|---|---|
| Tensile Strength (Rm) — MPa | ≥ 485 | ≥ 485 | ≥ 520 | ≥ 520 |
| Yield Strength (Rp0.2) — MPa | ≥ 205 | ≥ 205 | ≥ 205 | ≥ 205 |
| Elongation (A) — % | ≥ 40 | ≥ 40 | ≥ 40 | ≥ 40 |
| Impact Energy (20°C) — J | ≥ 55 | ≥ 55 | ≥ 55 | ≥ 55 |
| Operating Temperature Range — °C | −196 to +425 | −196 to +425 | −196 to +900 | −196 to +900 |
| Corrosion Resistance (Pitting, 3.5% NaCl) | Good | Excellent | Good | Good |
2.2 Chemical Composition Requirements (wt%)
| Element | SAE 304L | SAE 316L |
|---|---|---|
| C (Carbon) | ≤ 0.030 | ≤ 0.030 |
| Cr (Chromium) | 18.0 – 20.0 | 16.5 – 18.5 |
| Ni (Nickel) | 8.0 – 10.5 | 10.0 – 14.5 |
| Mo (Molybdenum) | — | 2.0 – 2.5 |
| N (Nitrogen) | ≤ 0.10 | ≤ 0.10 |
| P (Phosphorus) | ≤ 0.045 | ≤ 0.045 |
| S (Sulfur) | ≤ 0.030 | ≤ 0.030 |
3. Technical Specifications
| Parameter | Specification |
|---|---|
| Product Designation | JX-CT-857 (Cooling Coil Tube) |
| Outer Diameter (OD) | 12.7 mm (½") to 57.1 mm (2¼") |
| Wall Thickness | 0.8 mm – 6.0 mm (customizable) |
| Coil Diameter | 200 mm – 1200 mm (customizable) |
| Tightness Tolerance (OD) | ±0.1 mm |
| Wall Thickness Tolerance | ±10% |
| Surface Finish | Polished (Ra ≤ 0.4 μm) or Pickled & Passivated (Ra ≤ 1.6 μm) |
| Surface Roughness | Ra ≤ 0.4 μm (internal), Ra ≤ 0.8 μm (external) |
| End Condition | Plain end, Beveled end, or Threaded end |
| Applicable Standards | ASTM A213, ASTM A269, ASME SA-213, EN 10216-5, GB/T 12771 |
| Nuclear Grade Compliance | IEEE Std 383, RCC-M (France), NQA-1, HAF 6001 |
| Heat Treatment | Solution Annealed (1050°C – 1150°C) + Water Quenched |
| Welding Compatibility | TIG (GTAW), Orbital, Laser Welding |
4. Manufacturing Process
The manufacturing of nuclear-grade stainless steel cooling coil tubes follows a rigorous multi-stage process designed to ensure metallurgical integrity, dimensional accuracy, and freedom from defects that could lead to in-service leakage:
- Raw Material Inspection & Certification — Incoming stainless steel bar stock or seamless tube blanks are verified against mill test certificates (MTC) conforming to EN 10204 Type 3.1. Spectroscopic analysis confirms chemical composition compliance.
- Piercing & Hot Rolling — Billet steel is heated to 1100°C–1200°C and pierced to form seamless hollow tube blanks with precise outer diameter control.
- Cold Drawing & Sizing — Tubes undergo multi-pass cold drawing to achieve final OD and wall thickness dimensions within tight tolerances (±0.1 mm). This process enhances mechanical properties and surface finish.
- Coil Forming (Cold Bending) — Straight tubes are cold-bent into helical coil geometry using precision CNC coil forming machines. Bending radius is controlled to prevent wall thinning (>90% original thickness retained) and minimize residual stresses.
- Solution Annealing — Coils are heated to 1050°C–1150°C in a controlled atmosphere furnace and rapidly quenched to dissolve carbides, restore full austenitic microstructure, and relieve cold-work-induced residual stresses — a critical step to prevent stress corrosion cracking.
- Pickling & Passivation — Coils undergo acid pickling (HNO₃/HF mixture) to remove oxide scales, followed by passivation treatment to establish a stable chromium oxide protective film on the surface.
- Non-Destructive Testing (NDT) — 100% of coils are subjected to eddy current testing (ECT) for wall thickness and internal defect detection, plus visual inspection and dimensional verification.
- Leak Testing — Hydrostatic pressure testing at 1.5× design pressure to verify weld integrity and structural soundness.
- Final Inspection & Packaging — Coils are wrapped in protective film, packed in wooden crates with desiccant, and shipped with complete traceability documentation.
5. Applications
The JX-CT-857 Stainless Steel Cooling Coil Tube is engineered for the following nuclear and industrial applications:
- Nuclear Island Cooling Water Systems — Primary condensers, feedwater preheaters, and auxiliary cooling loops in PWR and BWR nuclear power plants.
- Reactor Coolant System (RCS) Components — Steam generator tube bundles and intermediate heat exchangers.
- Spent Fuel Pool Cooling — Immersion-type heat exchangers for spent fuel storage pools.
- Reactor Protection System (RPS) Cooling — Dedicated cooling circuits for instrumentation and control systems.
- Industrial Heat Exchangers — Chemical processing, pharmaceutical manufacturing, and food-grade heat exchange applications requiring sanitary-grade stainless steel.
- Marine & Offshore Equipment — Seawater cooling systems where chloride-induced corrosion resistance is critical.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains the following certifications and compliance frameworks to assure product quality for nuclear and critical infrastructure applications:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and testing operations.
- ISO 14001:2015 — Environmental Management System certification.
- NQA-1 (National Quality Assurance Project) — Quality assurance requirements for nuclear facilities, covering procurement, fabrication, and inspection.
- HAF 6001 — Chinese nuclear safety regulation for nuclear equipment manufacturing.
- ASME N Stamp — Authorization for fabrication of nuclear power plant components.
- RCC-M Compliance — French nuclear industry construction code compliance for material selection and testing.
- IEEE Std 383 — Guide for the selection of materials for nuclear power plant structures and components.
- EN 10204 Type 3.1 — Inspection certificates with specific test results for each batch.
7. Unique Selling Points
- Leakage Prevention Design — Informed by post-incident analysis of nuclear island cooling coil tube failures, the product incorporates enhanced metallurgical controls, optimized surface finish (Ra ≤ 0.4 μm internal), and rigorous residual stress elimination to mitigate SCC, FIV, and erosion-corrosion failure modes.
- Full Traceability — Each coil tube batch carries complete material pedigree documentation from raw material mill to final shipment, enabling root-cause analysis in the event of any anomaly.
- Customizable Geometry — Coil diameter, tube OD, wall thickness, and end conditions are fully customizable to meet specific heat exchanger design requirements.
- Multi-Grade Availability — Multiple stainless steel grades available to address varying levels of corrosion resistance, temperature capability, and mechanical strength demands.
- 100% NDT Coverage — Every coil undergoes complete eddy current and hydrostatic testing — no sampling-based inspection shortcuts.
Note: This product specification is intended for engineering reference and procurement purposes. All dimensions, tolerances, and material properties are subject to final agreement between the manufacturer and the purchaser. For nuclear service applications, compliance with the specific regulatory authority's requirements (e.g., NRC, CNSA, ASN) must be verified prior to installation.