Lead-Bismuth Eutectic

Pb-Bi

Moderators & Coolants

Density: 10.17 g/cm³

Atom density: 0.0294179 atoms/b·cm

Lead–bismuth eutectic: a liquid-metal coolant for fast reactors and spallation targets, melting at about 125 °C instead of lead's 327 °C.

Where these numbers come from

Eutectic composition 44.5 wt% Pb / 55.5 wt% Bi, with the lead expanded over its natural isotopes. Density carried over from the previous NRDP entry; not in the compendium.

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)
Pb-204 (82204)	6.2300e-3	6.3588e-3	1.8706e-4
Pb-206 (82206)	1.0724e-1	1.0840e-1	3.1889e-3
Pb-207 (82207)	9.8345e-2	9.8922e-2	2.9101e-3
Pb-208 (82208)	2.3318e-1	2.3342e-1	6.8667e-3
Bi-209 (83209)	5.5500e-1	5.5290e-1	1.6265e-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 Lead-Bismuth Eutectic
c ReactorMC NRDP derived material - reactormc.net/nrdp/material/lbe; rho = 10.17
c g/cm3 (use -10.17 on the cell card)
m25    82204.80c  -0.006230  $ Pb204
       82206.80c  -0.107245  $ Pb206
       82207.80c  -0.098345  $ Pb207
       82208.80c  -0.233180  $ Pb208
       83209.80c  -0.555000  $ Bi209

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

Bi-209 capture leads to Po-210, an intense alpha emitter with a 138-day half-life, which is the dominant radiological complication of LBE systems. Density falls with temperature; set it for your operating point.

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