Hafnium

Absorbers

Density: 13.31 g/cm³

Atom density: 0.0449084 atoms/b·cm

Hafnium metal control rod absorber. Used where a rod has to last: successive captures walk through the isotope chain and every step still absorbs.

Where these numbers come from

Natural hafnium metal. The compendium has no hafnium at all, so the isotopic abundances and masses come from the IUPAC/AME tables listed in scripts/nrdp/compendium.mjs, and the density is carried over from the previous NRDP entry.

Material compositions from PNNL-15870 Rev. 2 (April 2021), R.S. Detwiler, R.J. McConn Jr., T.F. Grimes, S.A. Upton, and E.J. Engel, Compendium of Material Composition Data for Radiation Transport Modeling, Pacific Northwest National Laboratory. Full report (DOI 10.2172/1782721)

Composition

Nuclide (ZAID)	Weight fraction	Atom fraction	Atom density (atoms/b·cm)
Hf-174 (72174)	1.5593e-3	1.6000e-3	7.1853e-5
Hf-176 (72176)	5.1850e-2	5.2600e-2	2.3622e-3
Hf-177 (72177)	1.8439e-1	1.8600e-1	8.3530e-3
Hf-178 (72178)	2.7197e-1	2.7280e-1	1.2251e-2
Hf-179 (72179)	1.3655e-1	1.3620e-1	6.1165e-3
Hf-180 (72180)	3.5367e-1	3.5080e-1	1.5754e-2

This is the material as formulated. The cards below carry weight fractions, written negative, which is what MCNP and Serpent read as a mass basis.

Generated material cards

MCNP

c Hafnium
c ReactorMC NRDP derived material - reactormc.net/nrdp/material/hafnium; rho =
c 13.31 g/cm3 (use -13.31 on the cell card)
m36    72174.80c  -0.001559  $ Hf174
       72176.80c  -0.051850  $ Hf176
       72177.80c  -0.184393  $ Hf177
       72178.80c  -0.271973  $ Hf178
       72179.80c  -0.136552  $ Hf179
       72180.80c  -0.353673  $ Hf180

MCNP and Serpent cards use .80c (ENDF/B-VII.1 at 293.6 K) — renumber m1 and change the suffix to match your deck. SCONE compositions are atom densities in atoms/barn-cm with the .03 suffix matching temp 300. See the library reference before changing a suffix: the mapping is not portable between vendors.

Notes

All six stable isotopes have significant capture cross sections, so hafnium depletes into more hafnium rather than into transparency. That is why it is used in naval reactor control rods, where rod replacement is not an option.

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