Ordinary Concrete (Portland)

Shielding

Density: 2.3 g/cm³

Atom density: 0.081429 atoms/b·cm

Portland cement concrete — the primary biological shield in most reactor facilities.

Where these numbers come from

PNNL-15870 Rev. 2, "Concrete, Portland" (id concrete-portland): 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)
H-1 (1001)	9.9974e-3	1.6873e-1	1.3740e-2
H-2 (1002)	2.2979e-6	1.9407e-5	1.5803e-6
C-12 (6012)	9.8843e-4	1.4011e-3	1.1409e-4
C-13 (6013)	1.1584e-5	1.5154e-5	1.2340e-6
O-16 (8016)	5.2767e-1	5.6116e-1	4.5694e-2
O-17 (8017)	2.1362e-4	2.1376e-4	1.7406e-5
O-18 (8018)	1.2202e-3	1.1532e-3	9.3902e-5
Na-23 (11023)	1.6000e-2	1.1838e-2	9.6397e-4
Mg-24 (12024)	1.5590e-3	1.1056e-3	9.0028e-5
Mg-25 (12025)	2.0560e-4	1.3997e-4	1.1397e-5
Mg-26 (12026)	2.3539e-4	1.5410e-4	1.2549e-5
Al-27 (13027)	3.3872e-2	2.1354e-2	1.7388e-3
Si-28 (14028)	3.0961e-1	1.8824e-1	1.5329e-2
Si-29 (14029)	1.6291e-2	9.5630e-3	7.7870e-4
Si-30 (14030)	1.1121e-2	6.3114e-3	5.1393e-4
K-39 (19039)	1.2082e-2	5.2744e-3	4.2949e-4
K-40 (19040)	1.5547e-6	6.6172e-7	5.3883e-8
K-41 (19041)	9.1663e-4	3.8064e-4	3.0995e-5
Ca-40 (20040)	4.2531e-2	1.8103e-2	1.4741e-3
Ca-42 (20042)	2.9804e-4	1.2082e-4	9.8385e-6
Ca-43 (20043)	6.3670e-5	2.5211e-5	2.0529e-6
Ca-44 (20044)	1.0066e-3	3.8955e-4	3.1721e-5
Ca-46 (20046)	2.0180e-6	7.4698e-7	6.0826e-8
Ca-48 (20048)	9.8446e-5	3.4921e-5	2.8436e-6
Fe-54 (26054)	7.9038e-4	2.4925e-4	2.0296e-5
Fe-56 (26056)	1.2866e-2	3.9126e-3	3.1860e-4
Fe-57 (26057)	3.0245e-4	9.0360e-5	7.3579e-6
Fe-58 (26058)	4.0956e-5	1.2025e-5	9.7920e-7

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.

Bound scattering

ENDF/B-VII.1 has a thermal scattering law for this material as formulated, so the cards attach lwtr.20t. Free-gas scattering would misplace the thermal spectrum here.

What ENDF/B-VII.1 forced

O18 folded into O16: ENDF/B-VII.1 has no O18 evaluation (0.001220 by weight, so the spectrum does not care).

The cards keep the material's mass and atom count; a nuclide the library cannot name hands its share to one it can. That is why a card row can differ slightly from the table above.

Generated material cards

MCNP

c Ordinary Concrete (Portland)
c PNNL-15870 Rev. 2, "Concrete, Portland" -
c reactormc.net/nrdp/material/concrete; rho = 2.3 g/cm3 (use -2.3 on the cell
c card)
c O18 folded into O16: ENDF/B-VII.1 has no O18 evaluation (0.001220 by weight,
c so the spectrum does not care).
m28    1001.80c  -0.009997  $ H1
       1002.80c  -2.2979e-6  $ H2
       6000.80c  -0.001000  $ C
       8016.80c  -0.528893  $ O16
       8017.80c  -2.1362e-4  $ O17
       11023.80c  -0.016000  $ Na23
       12024.80c  -0.001559  $ Mg24
       12025.80c  -2.0560e-4  $ Mg25
       12026.80c  -2.3539e-4  $ Mg26
       13027.80c  -0.033872  $ Al27
       14028.80c  -0.309615  $ Si28
       14029.80c  -0.016291  $ Si29
       14030.80c  -0.011121  $ Si30
       19039.80c  -0.012082  $ K39
       19040.80c  -1.5547e-6  $ K40
       19041.80c  -9.1663e-4  $ K41
       20040.80c  -0.042531  $ Ca40
       20042.80c  -2.9804e-4  $ Ca42
       20043.80c  -6.3670e-5  $ Ca43
       20044.80c  -0.001007  $ Ca44
       20046.80c  -2.0180e-6  $ Ca46
       20048.80c  -9.8446e-5  $ Ca48
       26054.80c  -7.9038e-4  $ Fe54
       26056.80c  -0.012866  $ Fe56
       26057.80c  -3.0245e-4  $ Fe57
       26058.80c  -4.0956e-5  $ Fe58
mt28   lwtr.20t

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

Hydrogen is only 1 wt% of concrete but does most of the neutron moderation, so mix design matters more than density for neutrons. ENDF/B-VII.1 has no bound-scattering evaluation for hydrogen in concrete; the card attaches lwtr.20t, which is the usual stand-in because the hydrogen is bound in cement hydrates. It is an approximation, not a table for concrete.

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