Lead

Moderators & Coolants

Density: 11.35 g/cm³

Atom density: 0.032988 atoms/b·cm

Natural lead coolant for lead-cooled fast reactors, and a workhorse gamma shield.

Where these numbers come from

PNNL-15870 Rev. 2, "Lead" (id lead): density and full isotopic composition are taken from the compendium unchanged.

Open the compendium entry for the isotope-by-isotope table and the compendium's own notes.

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)	1.3782e-2	1.4000e-2	4.6183e-4
Pb-206 (82206)	2.3958e-1	2.4100e-1	7.9501e-3
Pb-207 (82207)	2.2076e-1	2.2100e-1	7.2904e-3
Pb-208 (82208)	5.2596e-1	5.2400e-1	1.7286e-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
c PNNL-15870 Rev. 2, "Lead" - reactormc.net/nrdp/material/lead; rho = 11.35
c g/cm3 (use -11.35 on the cell card)
m24    82204.80c  -0.013782  $ Pb204
       82206.80c  -0.239575  $ Pb206
       82207.80c  -0.220761  $ Pb207
       82208.80c  -0.525964  $ Pb208

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

Room-temperature density; molten lead at ~480 °C is about 10.5 g/cm³. Natural lead is 1.4% Pb-204, 24.1% Pb-206, 22.1% Pb-207, 52.4% Pb-208, and the card names all four — ENDF/B-VII.1 has no natural-lead evaluation.

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