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Material World
Application

Nuclear fuel

Releasing energy by fission, and the materials that must survive doing it.

A fission reactor is a materials problem as much as a nuclear one. The fuel must hold together while its own atoms split; the cladding must contain fission products without absorbing the neutrons that sustain the reaction; the control materials must absorb neutrons strongly on demand.

Each of those requirements points at a different element, and the list of materials that satisfy any of them is very short.

Medium confidence Weak evidence checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

uses

  • Boron — element · boron-10 absorbs neutrons better than almost anything, making it the standard control-rod material
  • Helium — element · as the coolant in some high-temperature reactor designs, and for leak detection throughout the fuel cycle
  • Uranium — element · after enrichment, since the fissile isotope is 0.7% of natural uranium
  • Zirconium — element · fuel cladding, chosen because it lets neutrons through
  • Thorium — element · not itself fissile — it breeds uranium-233
  • Plutonium — element · as mixed oxide fuel, and as Pu-238 in spacecraft generators
  • Hafnium — element · as a control rod absorber rather than as fuel

Sources

  • Material World
    Our own writing

Questions this page answers

Where it comes from, and what it becomes

Follow Nuclear fuel back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

  • Nuclear fuel → uses (as mixed oxide fuel, and as Pu-238 in spacecraft generators) → Plutonium → is produced by (from uranium-238 absorbing a neutron and decaying twice — produced in every power reactor whether or not anybody wants it, and recovered only by reprocessing spent fuel) → Neutron irradiation → takes as input (uranium-238 is the feedstock for everything heavier: it absorbs neutrons without fissioning, which is what starts the sequence) → Uranium → is produced by (as yellowcake rather than metal: leaching and solvent extraction end at a uranium oxide concentrate, and the metal is several conversion steps further on) → Solvent extraction and electrowinning → takes as input (in the low-grade and oxidised ores that flotation cannot economically treat, with bacteria oxidising the sulfide into a form the acid can attack) → Chalcopyrite
  • Nuclear fuel → uses (boron-10 absorbs neutrons better than almost anything, making it the standard control-rod material) → Boron → is produced by (magnesium reducing boron oxide, which gives an impure amorphous boron — the crystalline element needs a different route entirely) → Metallothermic reduction → takes as input (the cheapest reducing metal and the commonest, and the aluminium in thermite) → Aluminium → is extracted from (via alumina — bauxite is refined by the Bayer process before smelting) → Bauxite → is sourced from (the residue of prolonged tropical weathering, which strips the silica and alkalis out of an aluminosilicate rock and leaves the aluminium behind — basalt is one common parent among several) → Basalt
  • Nuclear fuel → uses (fuel cladding, chosen because it lets neutrons through) → Zirconium → is produced by (reduced from the tetrachloride with magnesium, by the same route and in the same kind of vessel as titanium) → Kroll process → takes as input (the inert atmosphere, without which the titanium would take oxygen from the air) → Argon → is produced by (drawn from an intermediate height in the column, between nitrogen and oxygen) → Air separation → takes as input (the feedstock, and an unusual one in being free, unlimited and available anywhere — the cost is entirely the energy to liquefy it) → Air
  • Nuclear fuel → uses (as a control rod absorber rather than as fuel) → Hafnium → is produced by (separated from zirconium first — the two are chemically almost identical, and only nuclear use makes the separation worth its cost — then reduced the same way) → Kroll process → takes as input (the inert atmosphere, without which the titanium would take oxygen from the air) → Argon → is produced by (drawn from an intermediate height in the column, between nitrogen and oxygen) → Air separation → takes as input (the feedstock, and an unusual one in being free, unlimited and available anywhere — the cost is entirely the energy to liquefy it) → Air
  • Nuclear fuel → uses (after enrichment, since the fissile isotope is 0.7% of natural uranium) → Uranium → is produced by (as yellowcake rather than metal: leaching and solvent extraction end at a uranium oxide concentrate, and the metal is several conversion steps further on) → Solvent extraction and electrowinning → takes as input (in the low-grade and oxidised ores that flotation cannot economically treat, with bacteria oxidising the sulfide into a form the acid can attack) → Chalcopyrite
  • Nuclear fuel → uses (not itself fissile — it breeds uranium-233) → Thorium → is produced by (leached from monazite processing residues, and as an oxide rather than a metal — thorium is a by-product nobody currently wants, which is the difficulty rare earth operations keep running into) → Solvent extraction and electrowinning → takes as input (in the low-grade and oxidised ores that flotation cannot economically treat, with bacteria oxidising the sulfide into a form the acid can attack) → Chalcopyrite

These are the most distinct paths back. Nuclear fuel can be traced through others besides.