Fuel Sphere Manufacture

Presented by: David Boyes – STL Nuclear

IAEA 2015

Contents

• Fuel Sphere Design Overview

• Matrix Graphite Powder (MGP) Manufacture

• Coated Particle Over-coating (OCP)

• Fuel Sphere Manufacture (FS)

• Mould Manufacture

• Complex Processes

Fuel Sphere Design Overview

Fuel Sphere Design Overview (Cont.)

• The Kernel contains the heat-generating fuel material and provides chemical hold-up of fission products

• The Buffer Layer provides void volume for gaseous fission products and accommodates Kernel swelling

• The Inner Pyrolytic Carbon Layer provides a gastight diffusion barrier for metallic fission products and reduces tensile stresses on the Silicon Carbide Layer

• The Silicon Carbide Layer is the main diffusion barrier to metallic fission products and the primary pressure-retaining layer

• The Outer Pyrolytic Carbon Layer provides a barrier to gaseous fission products, a diffusion barrier to metallic fission products and reduces tensile stresses on the Silicone Carbide Layer

Fuel Sphere Design Overview (Cont.)

• The Graphite Matrix:

- consists of carbonized organic binder and nuclear-grade graphite material which acts as a fission neutron moderator

- provides the contact with the Coated Particles as a heat transfer medium and acts as a buffer to prevent exposure and damage of Coated Particles

- should exhibit high density, high thermal conductivity, high mechanical strength, low thermal expansion, low anisotropy, low Young’s modulus, good corrosion resistance and good dimensional stability under neutron irradiation

MGP Manufacture - Process Flow

Kneading

Drying (1000C)

Hammer Milling

Pre-Crushing

Graphite Powder Natural (64 %)

Graphite Powder Electro (16 %)

Phenolic Resin (20 %)

Methanol

Homogenization Dissolving

Homogenization

To Fuel Sphere Manufacture

Fine Milling To Coated Particle Over-coating

Swarf from Fuel Sphere Manufacture

(~11%)

TO FUEL SPHERES

MANUFACTURE

DISSOLVER MIXER

STORAGE

FINE MILLING

MILLING

RECYCLED GRAPHITE (SWARF)

METHANOL RECOVERY

DRYING OVEN

Coarse Milling

KNEADER

SOLVENT (METHANOL) & PHENOL BINDER

ELECTROLYTIC GRAPHITE NATURAL GRAPHITE

OVERCOAT MATRIX POWDER

MIXER

MIXER

MATRIX GRAPHITE POWDER

Matrix Graphite Powder

Manufacture

TO FUEL SPHERES

MANUFACTURE

DISSOLVER MIXER

STORAGE

FINE MILLING

MILLING

RECYCLED GRAPHITE (SWARF)

METHANOL RECOVERY

DRYING OVEN

Coarse Milling

KNEADER

SOLVENT (METHANOL) & PHENOL BINDER

ELECTROLYTIC GRAPHITE NATURAL GRAPHITE

OVERCOAT MATRIX POWDER

MIXER

MIXER

MATRIX GRAPHITE POWDER

Matrix Graphite Powder

Manufacture

OCP Manufacture - Process Flow

Over-coating (200µm)

Drying (800C)

Sorting

Sieving

Portioning

To Fuel Sphere Manufacture

Methanol

Removal of Over-coat Layer

Combining and Portioning

Fine Milled MGP from Matrix

Graphite Powder Manufacture

Scrap

Scrap

Coated Particles

OVERCOATING

OVERCOAT GRAPHITE & SOLVENT (METHANOL)

COATED PARTICLES

METHANOL REMOVAL

DRYING

SIEVING &SORTING

REJECT

COMBINING & PORTIONING

Coated Particle Over-coating

OVERCOATING

OVERCOAT GRAPHITE & SOLVENT (METHANOL)

COATED PARTICLES

METHANOL REMOVAL

DRYING

SIEVING &SORTING

REJECT

COMBINING & PORTIONING

Coated Particle Over-coating

FS Manufacture – Process Flow

Final Pressing (3 t/cm2)

Machining

Annealing (19500C in vacuum)

Carbonizing (8000C) Argon

Core Pressing

MGP from Matrix Graphite

Powder Manufacture

OCPs from Over-Coated Particle Manufacture

Core and Final Moulds from Mould Manufacture

Storage

Swarf to MGP Manufacture

OVERCOATED PARTICLES

CORE MOULD

PRE MIXER

MATRIX GRAPHITE POWDER

PRESSED FUEL

SPHERE CORE

CORE PRESS

SPLITTER

INMOULD MIXER

SCREW FEEDER

ROBOT

Fuel Sphere Manufacture (Sheet 1)

PRESSED FUEL

SPHERE

X-RAY INSPECTION

QA

MATRIX GRAPHITE POWDER FINAL PRESS

MATRIX GRAPHITE POWDER

SHELL FORMING

FINAL MOULD

CARBONISING CHARGE CARRIER

SWARF TO MGP MANUFACTURE

BUFFER STORAGE

PRESSEDFUEL

SPHERES

BUFFER STORAGE

VACUUM LIFTING INTO TRAYS

MACHINING

CARBONISING FURNACE

ANNEALING FURNACE

QA

REJECTS

DIMENSION INSPECTION VISUAL INSPECTION

MASS CONTROL X-RAY

COOLING TOWER

Fuel Sphere Manufacture (Sheet 2)

FINAL FUEL

SPHERES TO

STORAGE

CARBONISING CHARGE CARRIER

SWARF TO MGP MANUFACTURE

BUFFER STORAGE

PRESSEDFUEL

SPHERES

BUFFER STORAGE

VACUUM LIFTING INTO TRAYS

MACHINING

CARBONISING FURNACE

ANNEALING FURNACE

QA

REJECTS

DIMENSION INSPECTION VISUAL INSPECTION

MASS CONTROL X-RAY

COOLING TOWER

Fuel Sphere Manufacture (Sheet 2)

FINAL FUEL

SPHERES TO

STORAGE

Complex Processes are:

• To produce a particle size and distribution with hammer milling for reaching optimum density with the Graphite Matrix

• Mould tooling design

• Assembly of a fuel sphere

• Over-coating of coated particles

• Sorting of coated particles

• Understanding the splitting and portioning of Over-coated Particles to obtaining the correct fissile material loading per fuel sphere

Complex Processes