Nuclear-Grade Valves: Core Components Ensuring Safe and Efficient Operation of Nuclear Power Plants

The nuclear industry stands as one of the most safety-critical sectors in the global energy system, with its core lying in the precise control of radioactive substances and high-temperature, high-pressure fluids. As the “throat” of fluid control, valves directly determine the overall safety of nuclear power plants—from normal operation to emergency response. TIANYU, a professional manufacturer with nearly 20 years of expertise in nuclear-grade valves, has always centered its R&D around “ultimate safety and long-term reliability.” We design a full range of nuclear-grade valve products tailored to the unique operating conditions of nuclear power plants, covering key systems such as reactor cooling systems, safety injection systems, and steam cycle systems. To date, we have supplied over 10,000 high-performance valves to more than 50 nuclear power plants worldwide, with no major safety incidents reported. All products fully comply with standards set by the International Atomic Energy Agency (IAEA), the U.S. Nuclear Regulatory Commission (NRC), and nuclear safety authorities across various countries.

1. Core Requirements of the Nuclear Industry for Valves: Why TIANYU Nuclear-Grade Valves Are Indispensable?

The operating environment of nuclear power plants can be described as “industrial extreme”: fluid temperatures in systems can exceed 550°C, pressures surpass 2500 psi, radiation doses in some areas reach 10⁶ Gy, and coolants contain corrosive media such as boric acid and lithium. This demands that valves not only perform basic fluid control but also possess “extreme environment resistance” and “zero-failure safety redundancy.” By precisely meeting the four core functional needs of nuclear power plants, TIANYU nuclear-grade valves serve as a critical barrier to ensure system safety.

1.1 Flow Regulation: Millisecond-Level Precision Control for Stable System Conditions

Parameters such as steam generator water level and reactor coolant flow in nuclear power plants require real-time, precise adjustment—deviations exceeding 1% can trigger system fluctuations. To address this need, TIANYU integrates a “parabolic valve core + servo-grade electric actuator” in its GL Series Nuclear-Grade Globe Valves:

The valve core is optimized via CFD (Computational Fluid Dynamics) simulation, achieving a flow regulation accuracy of ±0.5% and a controllable range of 0-100%.
Paired with TIANYU’s independently developed EA-300 electric actuator (response time ≤ 0.5 seconds), the valve can be directly integrated into the plant’s DCS (Distributed Control System), controlling flow fluctuations within ±0.3%.

Take the feedwater system of an inland nuclear power plant as an example: the feedwater adjustment link of its steam generator uses TIANYU GL-500 Globe Valves (nominal diameter DN100, design pressure 2500 psi, design temperature 350°C). By adjusting the feedwater pump outlet flow in real time via 4-20mA analog signals, the valve ensures the steam generator water level deviation remains ≤ 0.2%, providing critical support for the stable energy supply of the reactor.

1.2 Isolation and Shut-Off: Zero-Leakage Sealing to Prevent Risk Diffusion

During equipment maintenance or emergency situations in nuclear power plants, valves must quickly shut off radioactive fluid circuits to prevent contamination spread. TIANYU’s GV Series Nuclear-Grade Gate Valves employ “dual sealing + hardfacing” technology:

The primary seal uses Inconel 625 alloy hard sealing (hardness ≥ HRC 60, wear and radiation resistant), while the secondary seal adopts PTFE-reinforced graphite elastic sealing. Together, these achieve a leakage rate ≤ 1×10⁻⁶ cm³/s, meeting the highest ANSI Class VI sealing standard.
The valve body features a thick-walled design (15% thicker than industry standards), maintaining structural stability even under 3000 psi high pressure.

During the reactor overhaul of a coastal nuclear power plant in 2020, TIANYU GV-800 Gate Valves (design pressure 3000 psi, design temperature 500°C) successfully isolated the reactor cooling circuit. Over a 72-hour maintenance period, helium mass spectrometry leak detection confirmed a zero leakage rate, completely eliminating the risk of coolant leakage.

1.3 Pressure Relief: Millisecond-Level Response to Block Overpressure Accidents

Overpressure in core equipment such as reactor pressure vessels (RPVs) and steam generators can lead to explosions or radioactive substance leakage. TIANYU’s PR Series Nuclear-Grade Pressure Relief Valves, acting as the “last safety barrier,” feature a “pilot-operated + spring-loaded” composite structure:

Set pressure accuracy is ±1%, opening response time ≤ 0.1 seconds, and closing pressure ratio ≥ 80% (ensuring reliable sealing after overpressure release).

In a simulated “Loss of Coolant Accident (LOCA)” test at a nuclear power plant, TIANYU PR-1000 Pressure Relief Valves (set pressure 2200 psi, design temperature 500°C) opened instantly when the system pressure reached 2530 psi. Within 30 seconds, the pressure was reduced to the safe range of 1800 psi, with no leakage after closing—fully complying with the emergency response standards outlined in IAEA’s Nuclear Power Plant Safety Design Requirements (SSR-2/1).

1.4 Backflow Prevention: Instant Check to Protect Clean Systems

Backflow in systems such as emergency cooling and chemical injection systems of nuclear power plants can contaminate clean water or air systems with radioactive substances. TIANYU’s CK Series Nuclear-Grade Check Valves adopt a “swing-type + spring-assisted closing” structure:

Closing speed is ≤ 0.2 seconds, and flow resistance coefficient ≤ 0.5 (no impact on normal system flow).
The sealing surface combines “Stellite alloy hard sealing + PTFE soft sealing,” adapting to a wide temperature range of -50°C to 450°C.

The Emergency Core Cooling System (ECCS) of a nuclear power plant uses TIANYU CK-600 Check Valves (nominal diameter DN200, design pressure 2000 psi). During a simulated pipeline rupture accident, the valve closed within 0.15 seconds, successfully preventing coolant backflow and avoiding contamination of the clean circuit—validating its reliability under extreme conditions.

2. Comprehensive Analysis of TIANYU’s Full Range of Nuclear-Grade Valves: Precise Adaptation to Various Nuclear Power Plant Scenarios

Operating conditions vary significantly across different nuclear power plant systems (e.g., high-temperature radiation in reactor compartments vs. medium-low pressure circulating water in cooling towers). TIANYU has developed six categories of nuclear-grade valves to address these differences, with each product optimized through a full “material-structure-testing” chain to ensure 100% compatibility with on-site requirements.

2.1 TIANYU GV Series Nuclear-Grade Gate Valves: “Steel Gates” for High-Pressure Isolation

Core Positioning: Designed for high-pressure systems requiring complete sealing and frequent isolation (e.g., Reactor Coolant Systems (RCS), main steam pipelines). With a design life of 40 years, it aligns with the overall service life of nuclear power plants.
Technical Highlights:

Materials: The main body uses Inconel 625 alloy (for high-temperature radiation areas) or 316L MOD low-carbon stainless steel (to reduce intergranular corrosion). Valve stems are made of 17-4 PH stainless steel (heat-treated via H900, yield strength ≥ 1100 MPa).
Sealing: A wedge-type double gate design is adopted, with Stellite 6 alloy hardfacing (3-5mm thickness) on the sealing surface. Combined with a “metal hard seal + elastic seal” dual structure, helium mass spectrometry leak detection confirms a leakage rate ≤ 1×10⁻⁹ Pa·m³/s.
Testing: Each valve undergoes a high-pressure strength test at 1.5 times the design pressure (30-minute pressure holding with no deformation) and a thermal cycle test from -40°C to 550°C (operation torque change ≤ 10% after 100 cycles).

Typical Application: The RCS of a nuclear power plant uses TIANYU GV-800 Gate Valves (nominal diameter DN200, design pressure 3000 psi, design temperature 500°C). After 8 years of operation, no maintenance failures have occurred, and the sealing performance remains above 95% of its initial state.

2.2 TIANYU GL Series Nuclear-Grade Globe Valves: “Precision Knobs” for Flow Regulation

Core Positioning: Used in systems requiring frequent, high-precision flow control (e.g., feedwater systems, condensate systems, chemical injection systems), delivering industry-leading regulation accuracy.
Technical Highlights:

Valve Core: Parabolic design optimized via CFD simulation for flow channels, achieving ±0.5% flow control accuracy and smooth full-stroke adjustment without jamming.
Sealing: Valve stems feature “V-type packing + metal bellows” dual sealing to prevent stem leakage, with a leakage rate ≤ 1×10⁻⁷ cm³/s.
Control: Supports PROFINET bus or 4-20mA signal control, seamlessly compatible with mainstream DCS systems from Siemens, Schneider, etc., with an actuator full-stroke time ≤ 5 seconds.

Typical Application: The condensate system of a nuclear power plant uses TIANYU GL-400 Globe Valves (nominal diameter DN80, design pressure 1500 psi, design temperature 250°C) to adjust the condensate pump outlet flow. This ensures stable water levels in the turbine condenser, with long-term adjustment errors ≤ 0.3%.

2.3 TIANYU CK Series Nuclear-Grade Check Valves: “Safety Sentinels” for Backflow Prevention

Core Positioning: Prevents reverse fluid flow to protect systems from water hammer or contamination (e.g., emergency cooling systems, ventilation systems), compatible with both horizontal and vertical installation.
Technical Highlights:

Structure: Swing-type disc with spring-assisted closing, achieving a closing speed ≤ 0.2 seconds and effectively suppressing water hammer (water hammer pressure ≤ 1.2 times the design pressure).
Materials: Valve bodies can be made of 316L stainless steel or Hastelloy C276 (corrosion resistant), with ceramic coating on disc surfaces (hardness ≥ HV 1200, erosion resistant).
Testing: Passes 1000 opening-closing cycle tests with no degradation in sealing performance; disc wear ≤ 0.02 mm after 5000 hours of operation under high-speed fluid (5 m/s).

Typical Application: The ventilation system of a nuclear power plant uses TIANYU CK-300 Check Valves (nominal diameter DN100, design pressure 100 psi) to prevent radioactive aerosols from flowing back into the control room. After 5 years of operation, no leakage has occurred, and air quality consistently meets nuclear safety standards.

2.4 TIANYU BL Series Nuclear-Grade Ball Valves: “Quick Switches” for Emergency Shut-Off

Core Positioning: Used in emergency systems requiring millisecond-level isolation (e.g., Safety Injection Systems (SIS), radioactive liquid treatment systems). Full open/close time is ≤ 10 seconds (electric drive), making it a “critical emergency response tool” for nuclear power plants.
Technical Highlights:

Ball: Floating ball with full-bore design, ensuring flow resistance loss ≤ 5%. Ball surfaces are coated with TIANYU’s patented XR-100 radiation-resistant coating (coating adhesion ≥ 5MPa under 10⁶ Gy irradiation).
Sealing: PTFE-reinforced seal rings are used for medium-low temperature conditions (temperature resistance: -200°C to 260°C), while Inconel 625 metal seals are used for high-temperature conditions (temperature resistance ≤ 500°C), achieving zero leakage.
Operation: Gear transmission with dual manual/electric drive; manual operation is available in emergencies (full-stroke time ≤ 30 seconds), and the actuator includes position feedback and fault alarm functions.

Typical Application: The safety injection system of a nuclear power plant uses TIANYU BL-700 Ball Valves (nominal diameter DN150, design pressure 3000 psi, design temperature 400°C). During a simulated reactor overheating accident, the valve fully closed within 1.2 seconds, isolating radioactive injection fluid and gaining critical time for emergency response.

2.5 TIANYU DF Series Nuclear-Grade Butterfly Valves: “Efficient Stewards” for Large-Diameter Systems

Core Positioning: Designed for large-diameter, medium-low pressure systems (e.g., cooling tower circulating water systems, sewage treatment systems, ventilation systems). Compared to gate valves of the same diameter, it weighs 40% less and reduces installation costs by 30%.
Technical Highlights:

Structure: Eccentric disc design achieves “zero leakage” (meeting ANSI Class V) with a low flow resistance coefficient (≤ 0.3).
Materials: Valve bodies are made of ductile iron lined with 316L stainless steel (cost-effective and durable) or full 316L stainless steel (for high-corrosion environments), with ceramic coating on disc surfaces (wear resistant).
Actuators: Equipped with TIANYU PA-400 pneumatic actuators (with fail-safe function, automatic closing upon air loss) or electric actuators, supporting modulating control (0-100% flow adjustment).

Typical Application: The cooling tower circulating water system of a nuclear power plant uses TIANYU DF-900 Butterfly Valves (nominal diameter DN800, design pressure 150 psi, design temperature 80°C) to adjust circulating water flow and control the cooling tower outlet water temperature between 25-30°C. After 6 years of operation, no corrosion or wear has occurred, and the maintenance cycle has been extended to 36 months.

2.6 TIANYU PR Series Nuclear-Grade Pressure Relief Valves: “Safety Valves” for Overpressure Protection

Core Positioning: A core component of nuclear power plant safety barriers, used in critical equipment such as reactor pressure vessels and steam generators to prevent catastrophic accidents caused by overpressure.
Technical Highlights:

Design: Pilot-operated structure with spring loading, achieving a set pressure deviation ≤ 3% and closing pressure ratio ≥ 80% (avoiding seal failure due to frequent opening).
Materials: Valve bodies use Inconel 625 alloy (high-temperature fatigue resistant), and springs use Inconel X-750 (elastic modulus change ≤ 5% at 550°C).
Testing: Each valve undergoes 1000 opening-closing cycle tests (no performance degradation) and overpressure burst tests (no valve body rupture under 2 times the design pressure), with complete third-party test reports (SGS or TÜV certification).

Typical Application: The steam generator (SG) of a nuclear power plant uses TIANYU PR-900 Pressure Relief Valves (set pressure 1800 psi, design temperature 350°C). During an overpressure incident caused by steam pipeline blockage, the valve opened within 0.08 seconds and reduced the pressure to 1400 psi within 15 seconds, avoiding damage to the SG tube sheet.

3. TIANYU’s Breakthroughs in Four Core Challenges of Nuclear-Grade Valve Design: From “Meeting Standards” to “Exceeding Standards”

The extreme conditions of the nuclear industry create an “impossible triangle” for valve design—simultaneously balancing temperature resistance, radiation resistance, and sealing performance. Through material innovation, structural optimization, and rigorous testing, TIANYU has addressed these industry pain points one by one, enabling its products to not only “meet standards” but also “exceed standards.”

3.1 Extreme Temperature and Pressure Challenges: Dual Enhancement of Materials and Structure

Pain Point: In reactor cooling systems, temperatures reach 500°C and pressures hit 3000 psi. Long-term operation can cause material fatigue, valve body deformation, and seal failure.
TIANYU’s Solution:

Material Selection: Nickel-based alloys (e.g., Inconel 625) are prioritized, retaining ≥ 85% yield strength at 550°C and showing no plastic deformation under 2500 psi. Valve internals use “17-4 PH stainless steel + dual aging treatment” (1020°C solution treatment + 480°C aging), improving high-temperature stability by 30%.
Structural Optimization: Valve bodies adopt a “thick-walled + reinforced rib” design—TIANYU GV Series Gate Valves have a body wall thickness of 50mm (compared to an industry average of 35mm for the same diameter), increasing pressure deformation resistance by 40%. TIANYU FJ-200 metal bellows joints are installed at valve-pipeline connections to absorb thermal expansion stress (compensation ±5mm).
Verification Data: TIANYU PR Series Pressure Relief Valves operate continuously for 1000 hours under 550°C and 3000 psi, with valve body deformation ≤ 0.1mm and no decline in sealing performance. After 100 thermal cycles from -40°C to 550°C, the operation torque change rate of GV Series Gate Valves is ≤ 10%.

3.2 Radiation Exposure Challenges: Full Protection from Materials to Coatings

Pain Point: Radiation doses in reactor compartments reach 10⁶-10⁸ Gy. Long-term radiation causes material embrittlement (reduced impact toughness), aging of organic seals, and coating peeling.
TIANYU’s Solution:

Radiation-Resistant Materials: Valve bodies use “low-cobalt alloys” (e.g., Inconel 625 LCF, cobalt content ≤ 0.1%) to reduce radiation-induced radioactive activation. Valve internals use 316L N stainless steel (nitrogen content 0.1-0.16%), retaining ≥ 70% impact toughness under 10⁶ Gy irradiation.
Seal Innovation: Traditional organic seals are replaced with Inconel 625 metal bellows seals (leakage rate ≤ 1×10⁻⁹ Pa·m³/s) or TIANYU’s patented XR-200 radiation-resistant rubber (retaining ≥ 80% elasticity under 10⁶ Gy irradiation).
Surface Protection: Valve body surfaces are coated with “nanoceramic radiation-resistant coating (XC-300)” (50-100μm thickness), showing no peeling or discoloration under 10⁸ Gy irradiation and protecting the valve body from radiation corrosion.
Verification Data: After 10⁶ Gy cobalt-60 irradiation, TIANYU CK Series Check Valves maintain a leakage rate ≤ 1×10⁻⁶ cm³/s, with a valve stem operation torque change rate ≤ 15%—fully meeting the radiation resistance requirements for nuclear-grade valves.

3.3 Corrosion and Erosion Challenges: Targeted Protection for Coolant Characteristics

Pain Point: Nuclear power plant coolants contain boric acid (concentration 2000-4000 ppm) and lithium (pH 7-10), which cause intergranular corrosion and stress corrosion cracking under high temperature and pressure. High-speed fluids (flow rate ≥ 5 m/s) lead to erosion and wear of valve internals.
TIANYU’s Solution:

Corrosion-Resistant Materials: Hastelloy C276 is used in boric acid coolant systems (annual corrosion rate ≤ 0.01 mm/year in 250°C boric acid solution). 316L MOD stainless steel (low carbon content ≤ 0.03%) is used in steam systems to prevent intergranular corrosion.
Erosion-Resistant Treatment: Valve internals (valve cores, seats) undergo “plasma nitriding” (hardness ≥ HV 1000) or “Stellite alloy hardfacing” (3-5mm thickness), improving wear resistance by 5x.
Flow Channel Optimization: “Streamlined flow channels” are designed via CFD simulation—TIANYU GL Series Globe Valves reduce local flow rates to ≤ 3 m/s, avoiding erosion caused by fluid eddies.
Verification Data: TIANYU GV Series Gate Valves are immersed in 4000 ppm boric acid solution (300°C, 2500 psi) for 1000 hours, showing no corrosion spots on the surface and weight loss ≤ 0.1 g/m². TIANYU BL Series Ball Valves operate under 5 m/s flow rate for 5000 hours, with seat wear ≤ 0.02 mm.

3.4 Seismic Toughness Challenges: Compliance with Global Highest Seismic Standards

Pain Point: Most nuclear power plants are located in seismically active zones (e.g., the Pacific Ring of Fire). Horizontal acceleration of 1.5 g caused by earthquakes can damage valve structures and actuator functions, affecting safety performance.
TIANYU’s Solution:

Compliance Design: All nuclear-grade valves meet ASME BPVC Section III and RCC-M Seismic Category D standards, covering seismic intensity up to magnitude 8 on the Richter scale.
Structural Reinforcement: Valve-pipeline connections use “thickened flanges + double bolt fixing” (bolt strength class 8.8). Actuator brackets adopt a “triangular support structure,” increasing impact resistance by 60%.
Component Fixing: Loose internal components (e.g., valve cores, stems) are fixed with “positioning pins + lock nuts” to prevent seismic displacement.
Verification Data: After seismic testing with 1.5 g horizontal acceleration and 1.0 g vertical acceleration, the set pressure change rate of TIANYU PR Series Pressure Relief Valves is ≤ 2%. TIANYU GV Series Gate Valves maintain normal manual/electric operation and meet sealing requirements after simulating a magnitude 8 earthquake.

4. Compliance and Quality Control of TIANYU Nuclear-Grade Valves: Full-Lifecycle Traceability from Production to Service

The quality of nuclear-grade valves not only affects product performance but also directly impacts nuclear safety. TIANYU has established a full-lifecycle quality control system covering “materials-production-testing-service,” with all links complying with global highest standards to ensure every valve is traceable and verifiable.

4.1 Compliance with Global Authoritative Standards: Covering International and National Requirements

TIANYU nuclear-grade valves fully comply with:

International Standards: IAEA’s Nuclear Power Plant Safety Design Requirements (SSR-2/1), ASME BPVC Section III (design and manufacturing standards for nuclear facility components), RCC-M (French rules for nuclear island mechanical equipment).
National/Regional Standards: China’s GB/T 19672 Nuclear-Grade Valves, U.S. NRC 10 CFR Part 50 (nuclear power plant licensing standards), EU EUR 23000 (nuclear safety guidelines).
Environmental Standards: RoHS 2.0 (banning harmful substances such as cadmium and lead), ISO 14001 Environmental Management System, ensuring environmental compliance throughout the product lifecycle.

4.2 Material Traceability: Full Control from Smelting to Processing

Material Procurement: Critical materials (e.g., Inconel 625, Hastelloy C276) are only sourced from steel mills with ASME SA certification. Each batch of materials is accompanied by a “Material Test Certificate (MTC)” recording chemical composition, mechanical properties, and heat treatment processes.
Third-Party Testing: All materials are sent to third-party laboratories such as SGS and TÜV Rheinland for radiation resistance and corrosion resistance testing. Test reports are retained for ≥ 40 years (consistent with the service life of nuclear power plants).
Rejection of Non-Conforming Materials: A “material rejection system” is implemented—any batch of materials failing testing is immediately returned in full, ensuring 100% compliance of materials entering the production process.

4.3 Production and Testing: Rigor Exceeding Industry Norms

Production Control: TIANYU’s nuclear-grade valve production base holds ASME BPVC Section III NPT certification and RCC-M Class A certification. Workshops implement “cleanroom management” (Class 8 cleanliness), with key processes (e.g., seal surface hardfacing, ultra-precision grinding) operated by certified welders/technicians.
Factory Testing: Every valve must undergo three mandatory tests:
1. Pressure Strength Test: 1.5 times the design pressure for 30 minutes, with no leakage or deformation.
2. Leakage Test: Helium mass spectrometry leak detection (sensitivity 1×10⁻¹² Pa·m³/s) or underwater bubble testing (no bubbles).
3. Function Test: 5 full-stroke operations to ensure normal movement and accurate actuator feedback signals.
Type Certification: Each valve model passes “type testing,” including 1000-hour long-term operation testing, high-low temperature environmental testing, and radiation testing, obtaining type approval certificates from institutions such as IAEA and NRC.

4.4 Full-Lifecycle Service: End-to-End Support from Installation to Decommissioning

TIANYU provides “full-lifecycle services for nuclear-grade valves,” including:

Installation Guidance: Certified engineers are dispatched to the site to guide valve installation, ensuring compliance with nuclear power plant construction standards.
Regular Inspection: Annual “valve health diagnosis services” are provided, evaluating valve status via ultrasonic flaw detection, wall thickness measurement, and leakage testing.
Maintenance and Repair: Original spare parts are supplied (inventory cycle ≤ 72 hours), extending the maintenance cycle to 24-36 months and reducing customer operation costs.
Intelligent Monitoring: Some valves integrate temperature, pressure, and vibration sensors to transmit real-time data to the nuclear power plant’s DCS system, supporting predictive maintenance and early fault prevention.
Decommissioning Handling: Professional disassembly, testing, and environmental disposal services are provided during valve decommissioning to ensure no residual radioactive contamination.

5. Conclusion: TIANYU Empowers Safe and Sustainable Development of the Nuclear Industry

As the global “dual carbon” goals advance, the nuclear industry—with its clean, stable base-load energy—grows increasingly important. Nuclear-grade valves, as the “safety cornerstone” of nuclear power plants, demand continuous technological innovation. TIANYU will continue to invest in R&D, focusing on three key breakthrough directions in the future:

Intelligent Nuclear-Grade Valves: Integrating IoT and AI technologies to enable real-time valve status monitoring, fault early warning, and automatic maintenance, further enhancing operational reliability.
New Radiation-Resistant Materials: Developing ceramic matrix composites (CMCs) that retain ≥ 90% material strength under 10⁸ Gy irradiation, breaking the radiation resistance limits of existing metal materials.
Ultra-High-Pressure Large-Diameter Valves: Designing ultra-high-pressure valves with a design pressure of 4500 psi and nominal diameter of DN600 for next-generation advanced nuclear reactors (e.g., Small Modular Reactors (SMRs)) to adapt to more extreme operating conditions.

From laboratory R&D to on-site operation in nuclear power plants, TIANYU has always adhered to the philosophy of “safety first, customer foremost.” With professional nuclear-grade valve products, we are committed to safeguarding the safe, efficient, and sustainable development of the global nuclear industry.