UZrH₁.₆ (TRIGA fuel)

UZrH₁.₆

Fuels

Density: 6 g/cm³

Uranium-zirconium hydride fuel used in TRIGA research reactors. 20% enriched U with Zr-H matrix providing inherent negative temperature feedback.

Composition

Nuclide / Element	Fraction
U-235	0.055556
U-238	0.222222
Zirconium (natural)	0.277778
H-1	0.444444

S(α,β) required: h-zr, zr-h

Code output

MCNP

c UZrH1.6 TRIGA fuel (20% enriched U)
c Density: 6.0 g/cm3 (use -6.0 on cell card)
c Atoms per formula: 1 U + 1 Zr + 1.6 H = 3.6
m8    92235.80c  0.055556  $ U-235
      92238.80c  0.222222  $ U-238
      40000.80c  0.277778  $ Zr (natural)
       1001.80c  0.444444  $ H-1
mt8   h-zr.20t zr-h.20t

Notes

U content is typically 8.5–12 wt% of the total fuel meat. Density and H/Zr ratio vary by fuel element type. The ZrH matrix provides a large prompt negative temperature coefficient.

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