Cross-Section Library Reference
Suffix naming convention
The suffix format is .XXy where XX is a library identifier and y is the data type.
| Type | Description |
|---|---|
| c | Continuous-energy neutron interaction data. The primary data type for transport calculations. |
| p | Photoatomic interaction data for photon transport (MODE P). |
| t | Thermal scattering S(α,β) data for bound-atom thermal treatment. |
| d | Dosimetry cross sections for activation and dose calculations. |
| u | Unresolved resonance probability tables. |
Library families
ENDF/B — Evaluated Nuclear Data File (US)
NNDC / BNL / LANL
The primary US nuclear data library maintained by the Cross Section Evaluation Working Group (CSEWG). ENDF/B-VIII.0 (2018) is the latest release with significant improvements to light nuclei, actinides, and thermal scattering data.
https://www.nndc.bnl.gov/endf/JEFF — Joint Evaluated Fission and Fusion File (Europe)
NEA Data Bank / OECD
The European evaluated library jointly developed by NEA member countries. JEFF-3.3 (2017) features strong structural material and fission product evaluations, often complementary to ENDF/B.
https://www.oecd-nea.org/dbdata/jeff/JENDL — Japanese Evaluated Nuclear Data Library
JAEA
Japan's comprehensive evaluated library. JENDL-5.0 (2021) includes extensive updates to minor actinides and fission products, particularly strong for fast-reactor applications.
https://wwwndc.jaea.go.jp/jendl/jendl.htmlSuffix table
| Suffix | Library | Temperature | Type | Energy range | Description |
|---|---|---|---|---|---|
| .80c | ENDF/B-VIII.0 | 293.6 K | Continuous-energy neutron | 1e-11 – 20 MeV | Latest US evaluated library. Recommended for most applications.(recommended) |
| .81c | ENDF/B-VIII.0 | 600 K | Continuous-energy neutron | 1e-11 – 20 MeV | ENDF/B-VIII.0 at 600 K for hot-zero-power conditions. |
| .82c | ENDF/B-VIII.0 | 900 K | Continuous-energy neutron | 1e-11 – 20 MeV | ENDF/B-VIII.0 at 900 K for fuel-temperature conditions. |
| .83c | ENDF/B-VIII.0 | 1200 K | Continuous-energy neutron | 1e-11 – 20 MeV | ENDF/B-VIII.0 at 1200 K for high-temperature fuel. |
| .84c | ENDF/B-VIII.0 | 2500 K | Continuous-energy neutron | 1e-11 – 20 MeV | ENDF/B-VIII.0 at 2500 K for accident-condition fuel temperatures. |
| .71c | ENDF/B-VII.1 | 293.6 K | Continuous-energy neutron | 1e-11 – 20 MeV | Widely used US library. Default in many MCNP installations.(recommended) |
| .72c | ENDF/B-VII.1 | 600 K | Continuous-energy neutron | 1e-11 – 20 MeV | ENDF/B-VII.1 at 600 K. |
| .73c | ENDF/B-VII.1 | 900 K | Continuous-energy neutron | 1e-11 – 20 MeV | ENDF/B-VII.1 at 900 K. |
| .74c | ENDF/B-VII.1 | 1200 K | Continuous-energy neutron | 1e-11 – 20 MeV | ENDF/B-VII.1 at 1200 K. |
| .70c | ENDF/B-VII.0 | 293.6 K | Continuous-energy neutron | 1e-11 – 20 MeV | Legacy US library. Superseded by VII.1 and VIII.0. |
| .66c | ENDF/B-VI.8 | 293.6 K | Continuous-energy neutron | 1e-11 – 20 MeV | Legacy library. Not recommended for new calculations. |
| .84p | ENDF/B-VIII.0 | N/A | Photoatomic | 1 keV – 100 GeV | Photon interaction cross sections (photoelectric, Compton, pair production).(recommended) |
| .70p | ENDF/B-VII.0 | N/A | Photoatomic | 1 keV – 100 GeV | Legacy photon interaction data. |
| .20t | ENDF/B-VIII.0 | 293.6 K | Thermal S(α,β) | < 4 eV | Thermal scattering law for bound atoms. Required for accurate thermal-spectrum transport.(recommended) |
| .21t | ENDF/B-VIII.0 | 350 K | Thermal S(α,β) | < 4 eV | S(α,β) data at 350 K. |
| .22t | ENDF/B-VIII.0 | 400 K | Thermal S(α,β) | < 4 eV | S(α,β) data at 400 K. |
| .23t | ENDF/B-VIII.0 | 500 K | Thermal S(α,β) | < 4 eV | S(α,β) data at 500 K. |
| .24t | ENDF/B-VIII.0 | 600 K | Thermal S(α,β) | < 4 eV | S(α,β) data at 600 K. |
| .25t | ENDF/B-VIII.0 | 800 K | Thermal S(α,β) | < 4 eV | S(α,β) data at 800 K. |
| .10t | ENDF/B-VII.1 | 293.6 K | Thermal S(α,β) | < 4 eV | Thermal scattering law tables from ENDF/B-VII.1. |
| .11t | ENDF/B-VII.1 | 350 K | Thermal S(α,β) | < 4 eV | S(α,β) data from ENDF/B-VII.1 at 350 K. |
| .12t | ENDF/B-VII.1 | 400 K | Thermal S(α,β) | < 4 eV | S(α,β) data from ENDF/B-VII.1 at 400 K. |
| .31c | JEFF-3.1 | 293.6 K | Continuous-energy neutron | 1e-11 – 20 MeV | European Joint Evaluated Fission and Fusion File. |
| .32c | JEFF-3.2 | 293.6 K | Continuous-energy neutron | 1e-11 – 20 MeV | Updated JEFF library with improved actinide evaluations. |
| .33c | JEFF-3.3 | 293.6 K | Continuous-energy neutron | 1e-11 – 20 MeV | Latest JEFF release. Strong for structural materials and fission products.(recommended) |
| .40j | JENDL-4.0 | 293.6 K | Continuous-energy neutron | 1e-11 – 20 MeV | Japanese Evaluated Nuclear Data Library. |
| .50j | JENDL-5.0 | 293.6 K | Continuous-energy neutron | 1e-11 – 20 MeV | Latest Japanese library with comprehensive updates to minor actinides.(recommended) |
ZAID identifier rules
A ZAID (Z and A IDentifier) uniquely identifies a nuclide: ZZZAAA where ZZZ is the atomic number and AAA is the mass number.
Format
92235→ Z=92 (U), A=2351001→ Z=1 (H), A=18016→ Z=8 (O), A=1694239→ Z=94 (Pu), A=239
Common mistakes
92000= natural uranium (A=000), not U-200- Full ID in MCNP/Serpent:
92235.80c(ZAID + suffix) - SCONE (ACE):
92235.06incomposition— suffix must match a nuclide in your ACE library (see SCONE nuclear data) - OpenMC uses element names:
'U235', not numeric ZAIDs - Metastable states add 400 to A:
95642= Am-242m (95000 + 242 + 400)
Thermal scattering S(α,β) guide
Below ~4 eV, neutron scattering is affected by chemical binding and crystal structure. Free-atom cross-sections are inaccurate — you must apply S(α,β) thermal scattering libraries for bound scatterers.
| Scatterer | MCNP (mt card) | Serpent (therm) | OpenMC |
|---|---|---|---|
| H in light water | lwtr.20t | lwj3.11t / lwj3.22t | c_H_in_H2O |
| D in heavy water | hwtr.20t | hwj3.11t | c_D_in_D2O |
| C in graphite | grph.20t | grj3.11t | c_Graphite |
| H in polyethylene | poly.20t | polj3.11t | c_H_in_CH2 |
| H in ZrH | h-zr.20t | hzrj3.11t | c_H_in_ZrH |
| Be metal | be.20t | bej3.11t | c_Be |
| Zr in ZrH | zr-h.20t | zrzrj3.11t | c_Zr_in_ZrH |
Match the thermal scattering library temperature to your material temperature. Use .11t (~300 K) for room temperature and .22t (~600 K) for reactor operating conditions. Some libraries support interpolation between two temperatures.
SCONE: continuous-energy transport uses whatever thermal and S(α,β) data are present in your processed ACE library. Align material temp and ZAID suffixes with that library’s documentation—the MCNP/Serpent thermal names above describe the same underlying evaluations you often embed in ACE builds.
Common MT reaction numbers
MT numbers identify specific nuclear reactions in cross-section data and tally specifications.
| MT | Reaction | Description |
|---|---|---|
| 1 | (n,total) | Total cross-section |
| 2 | (n,elastic) | Elastic scattering |
| 4 | (n,inelastic) | Total inelastic scattering |
| 16 | (n,2n) | Neutron multiplication |
| 18 | (n,fission) | Total fission |
| 102 | (n,γ) | Radiative capture |
| 103 | (n,p) | Proton production |
| 104 | (n,d) | Deuteron production |
| 105 | (n,t) | Triton production |
| 107 | (n,α) | Alpha production |
| 251 | μ̄ | Average scattering cosine |
| -2 | absorption | Total absorption (MCNP tally multiplier) |
| -6 | fission ν | Total fission × ν (MCNP tally multiplier) |
Material card sanity checks
Before running
- Don't mix atom and weight fractions in the same material (MCNP/Serpent enforce this)
- Fractions don't need to sum to 1 — codes normalize automatically — but ratios must be correct
- Check density sign: negative = g/cm³, positive = atoms/barn-cm (MCNP cell cards; SCONE uses atoms/barn-cm in
composition) - Verify library suffix exists in your xsdir/xsdata for every ZAID (or, for SCONE, that each ZAID.suffix exists in your ACE file)
- Add S(α,β) for any bound scatterer below ~4 eV (water, graphite, poly, ZrH)
Common errors
- UO₂ with wrong O fraction: should be 2 atoms O per 1 atom U (atom ratio), not by weight
- Borated water: 1000 ppm boron ≈ 0.001 weight fraction, not 0.001 atom fraction
- Forgetting that Zirc-4 has Sn, Fe, Cr — not just Zr
- Using room-temperature density (1.0 g/cm³) for hot water at reactor conditions (~0.7 g/cm³)
- Missing thermal scattering for hydrogen — can shift k-eff by 1000+ pcm