Fuel Assembly

Product Specifications

Technical details and manufacturing context for Fuel Assembly

Definition

A fuel assembly is the fundamental modular unit within a nuclear reactor core that houses multiple nuclear fuel rods in a precisely engineered configuration. It serves as the primary containment structure for fissile material, facilitating controlled nuclear fission while maintaining structural integrity under extreme thermal, mechanical, and radiation conditions. Each assembly is designed to optimize neutron moderation, heat transfer, and fuel burnup efficiency throughout its operational lifecycle. The assembly typically consists of a framework of zirconium alloy cladding tubes filled with enriched uranium dioxide pellets, arranged in a lattice pattern such as the standard 17×17 arrangement for pressurized water reactors. The structural components, often made of stainless steel or Inconel, provide mechanical support and precise spacing to ensure uniform coolant flow and neutron flux distribution. Key parameters include an overall length of 4000–5000 mm, a cross-section width of 200–300 mm, and a fuel rod outer diameter of 9.5–11.0 mm. The cladding material is typically Zr-4 per ASTM B353, and the fuel pellet material is UO2 per ASTM C753, with uranium enrichment of 3.0–5.0% per ASTM C996. The assembly weight ranges from 600–800 kg, and it operates at temperatures of 300–400°C and pressures of 15.5–16.0 MPa. Coolant flow rate is 20–30 kg/s, with a pressure drop of 0.2–0.4 MPa. Neutron flux is 3.0–5.0 × 10^13 n/cm²·s, and the design lifetime is 4–6 years. These values are reference ranges and must be verified for the specific model and application with the legal manufacturer or supplier.

Working Principle

Fuel assemblies contain enriched uranium or other fissile materials in fuel rods. When positioned in the reactor core, they sustain a controlled nuclear chain reaction. Neutrons released during fission are moderated and absorbed by adjacent fuel rods, generating heat that is transferred to a coolant (typically water). The assembly's structural framework maintains precise rod spacing for optimal neutron flux distribution and coolant flow while providing mechanical support and handling capabilities. The heat generated is removed by the coolant, which flows through the assembly at a rate of 20–30 kg/s, with a pressure drop of 0.2–0.4 MPa. The operating temperature and pressure are 300–400°C and 15.5–16.0 MPa, respectively. The design ensures efficient heat transfer and neutron moderation, contributing to the overall performance and safety of the reactor.

Common Materials

Zirconium alloy cladding, Enriched uranium dioxide pellets, Stainless steel or Inconel structural components

Technical Parameters

Parameter	Typical range	Notes & selection driver
Overall Length	4000–5000 mm	Determines reactor core height compatibility
Cross-Section Width	200–300 mm	Fits fuel assembly pitch
Number of Fuel Rods	17×17	Standard PWR lattice arrangement
Fuel Rod Outer Diameter	9.5–11.0 mm	Affects heat transfer and neutron moderation
Cladding Material	Zr-4	Zirconium alloy for low neutron absorptionASTM B353
Fuel Pellet Material	UO2	Uranium dioxide with 3–5% enrichmentASTM C753
Uranium Enrichment	3.0–5.0 %	Critical for reactivity controlASTM C996
Assembly Weight	600–800 kg	Handling and transport constraints
Operating Temperature	300–400 °C	Coolant outlet temperature range
Operating Pressure	15.5–16.0 MPa	Primary coolant pressure
Coolant Flow Rate	20–30 kg/s	Ensures adequate heat removal
Pressure Drop	0.2–0.4 MPa	Affects pump sizing and flow distribution
Neutron Flux	3.0–5.0 10^13 n/cm²·s	Determines power density
Design Lifetime	4–6 years	Fuel cycle length

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Components / BOM

Fuel Rod Part
Contains nuclear fuel pellets and provides first containment barrier

Material: Zirconium alloy cladding with uranium dioxide pellets
Spacer Grid Part
Maintains precise spacing between fuel rods and promotes coolant mixing

Material: Zirconium alloy or Inconel
Top and Bottom Nozzles
Provide structural support, flow distribution, and handling interfaces

Material: Stainless steel or Inconel
Guide Thimble Part
Houses control rod channels and instrumentation conduits

Material: Zirconium alloy

Applied To / Applications

This component is essential for the following industrial systems and equipment:

Reactor Core

View system integration details

Manufacturers of Fuel Assembly

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Frequently Asked Questions

What is the typical lattice arrangement for a fuel assembly?

The standard arrangement for pressurized water reactors is 17×17, meaning 17 rods per side in a square lattice. This configuration is common, but other arrangements exist depending on reactor design.

What materials are used in fuel assembly construction?

Fuel rods are clad in zirconium alloy (typically Zr-4 per ASTM B353) and contain uranium dioxide pellets (UO2 per ASTM C753) with enrichment levels of 3.0–5.0% per ASTM C996. Structural components may be stainless steel or Inconel.

What are the key operating parameters?

Typical operating temperature is 300–400°C, pressure is 15.5–16.0 MPa, coolant flow rate is 20–30 kg/s, and neutron flux is 3.0–5.0 × 10^13 n/cm²·s. These are reference ranges; verify for your specific application.

How long does a fuel assembly last?

The design lifetime is typically 4–6 years, depending on the fuel cycle and reactor operation. Actual lifetime may vary based on burnup and operational conditions.

Data Basis

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pressure:	15-16 MPa (PWR primary coolant pressure)
flow rate:	4-6 m/s coolant velocity
temperature:	+300°C to +400°C
neutron flux:	Up to 3×10^14 n/cm²·s thermal

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