Hoax or Real? — Code & Data

This repository accompanies the paper
“Hoax or Real? On the Uniqueness of Nuclear Radiation Signatures”
by Christopher Fichtlscherer and Moritz Kütt, published in Science & Global Security (2024).
It contains every input file, simulation result, and script required to reproduce the figures and tables in the article.

Repository layout

Folder	What’s inside
unique/	Reusable library code – detector / geometry models, data I/O helpers, etc.
scripts/	One-off scripts that reproduce every figure and table.
data/	Experimental datasets and nuclear-data libraries used as inputs.
results/	Computed simulation outputs and rendered figures.

Quick start

git clone https://github.com/cfichtlscherer/Hoax_or_Real_Code.git cd Hoax_or_Real_Code pip install -e .

Reproduce a single figure, e.g. Figure 1

python scripts/plot_detector_response.py

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unique/ - library code

Module	Purpose
data.py	Collects constants and tables: Spontaneous-fission Watt parameters, branching ratios, half-lives, neutron-multiplicities, plus the list of isotopes available from the DOE Isotope Program.
detector.py	Detector utilities. Simulates the NaI(Tl) response in OpenMC, broadens pulse-height tallies, converts them to IBX II/TRIS formats, and evaluates the corresponding test statistics.
models.py	OpenMC geometries for all theoretical weapon models: the FPS model, a bare plutonium pit, and the W78 / W87 designs (each with and without their re-entry vehicle).
nndc_decay.py	Decays arbitrary material vectors and computes γ- and n-emission spectra using ENSDF data.
nndc_download.py	Bulk-downloads the ENSDF decay database from NuDat 3.
nndc_extraction.py	Cleans and restructures the raw ENSDF files into pandas-friendly tables.

scripts/ - producing figures & results

Generated figures are written to results/figures/ unless stated otherwise.

Category	Script / folder	Purpose
Detector-response simulation	simulate_detector_response/	Monte-Carlo simulation of the Mirion 802 NaI(Tl) 2×2″ detector using the pulse-height tally. • unique/detector.py – detector geometry & materials • run.py – runs 15 mono-energetic γ simulations • slurm.sh – SLURM batch template for one job • multi_starter.sh – submits ≈800 jobs in parallel • run_broadening.py – converts raw spectra (XXX.0_detector_sharp.npy) with the fitted resolution, producing XXX.0_detector_broad.npy (stored in results/detector_response/). Raw spectra are not included in the repository to keep its size reasonable.
Emission-source simulation	simulate_pit_emissions/ simulate_fps_emissions/ simulate_w78_emissions/ simulate_w87_emissions/	OpenMC source-term simulations for the plutonium pit, the FPS, W78 and W87 weapon models, respectively. Each folder contains a run.py, slurm.sh, and multi_starter.sh. The pit geometry is defined in unique/models.py. Results reside in results/<model>_emissions/.
Radioactive decay utilities	decay_all_isotopes.py	Decays every isotope with t½ > 7 days and stores the activities in all_decay_results_7hl_decay_3d.pickle and all_decay_results.pickle.
	decay_weapon_material.py	Performs the decay calculation for different plutonium and uranium compositions used in nuclear weapons.
Spectrum / system-signal generation	detector_and_system_signals_from_objects_and_isotopes.py	Generates detector count spectra and confirmation-system signals from the simulated object emissions.
Detector-resolution fit	fit_detector_resolution.py	Derives the NaI detector resolution parameters (a, b, c) from the experimental dataset osprey-35mm-na-cs (copied from sgs-lab/ibxII-measurements).
Plotting & figure generation	plot_detector_response.py	Creates Figure 1 (simulated detector response).
	plot_pit_emissions.py	Combines pit emission spectra for different ages and plots Figure 2 (0-year vs 50-year). Stores merged spectra in results/object_emission_spectra/pit_<age>_emissions.npy.
	plot_models_ray_tracing.py	Produces Figure 3 (ray-tracing views of the weapon models). Requires OpenMC PR #2655 “Raytrace plots”.
	plot_fps_emissions.py	Generates Figure 4 (FPS emissions).
	plot_total_emissions_thermo_nuclear_weapon_model.py	Generates Figures 5 & 6 (thermonuclear-weapon model emissions).
	plot_heatmap.py	Generates Figure 7.
	plot_emissions_PGPU_hoax.py	Produces Figure 8 (top & bottom).
	plot_halflife_vs_activity.py	Generates Figure 9 (half-life vs activity of γ-emitters in NNDC).
	determine_and_plot_hoaxes.py	Creates Figures 10 & 11 and the appendix examples.
	plot_alphan_energy_spectrum.py	Generates Figure 12 – (α,n) neutron-energy spectrum from Sources4C.
	find_and_plot_number_bins.py	Computes test results for different bin numbers (stored in results/test_results_number_of_bins.pickle) and plots Figure 13.
Hoax-search utilities	greedy_minimize.py	Iteratively removes isotopes and searches the remaining subset for minimal-isotope hoaxes for finding isotopes using only a very small number of isotopes.
Tables & printed outputs	print_pu3013_vector_and_U_emissions.py	Reads results/nndc_data_processed/* and prints the Pu-3013 vector plus uranium emissions (Tables 2 & 3 of the paper).

data/  – input datasets and reference files

Item	Description	Origin / Notes
IBX_II_measurement_data/	Experimental NaI(Tl) pulse‑height spectra used to fit the detector resolution.	Copied from the ibxII‑measurements repository.
Q_values.csv	Nuclear Q‑values (MeV) for all relevant decay modes.	Downloaded directly from NuDat 3.
nuclear_walled_decay_data.csv	Needed for (i) stable nuclides and (ii) spontaneous‑fission branching ratios.	https://www.nndc.bnl.gov/walletcards/.
pyne_nuclide_names.txt	Canonical nuclide names.	Taken from PyNE.
PoBe_equal_atom_fraction.npy	Neutron‑energy spectrum of a PoBe (α,n) source with equal atom fraction.	Calculated by M. Kütt using SOURCES‑4C on a local workstation.

results/ – simulation outputs & figures

Path	Description
detector_response/	NaI(Tl) response functions for mono-energetic γ-rays from 0 keV to 12,029 keV (already Gaussian-broadened). - 30,000 channels (0.1 keV each) per spectrum - Filenames: XXX.0_detector_broad.npy
figures/	All PDF figures cited in the paper (Figure 1 – 13).
isotope_emission_spectra/	Photon-emission and detector-signal libraries for every nuclide considered in the hoax search. For each isotope you will find: • *_emissions.npy – differential γ-emission rate (1 keV bins, units = γ s⁻¹ mol⁻¹) • *_detector.npy – 30 000-channel detector spectrum (0.1 keV bins) • *_ibx.npy – 12-channel IBX-II signature • *_tris.npy – 14-channel TRIS signature.
object_emission_spectra/	Combined emission spectra and detector signals for the theoretical weapon models (pit, FPS, W78, W87, …). Range: 0–12 MeV in 1 keV steps.
test_results_number_of_bins.pickle	Simulation results from find_and_plot_number_bins.py used in Figure 13.
nndc_data_processed/	Processed ENSDF decay data and derived material vectors: • big_df_all_nuclide_data.pickle – master dataframe containing all NNDC decay information(~200 k rows) • all_gamma_intensities.pickle – γ-intensity per isotope (1 mol s⁻¹) • all_equilibria.pickle / all_decay_results_7hl.pickle – equilibria / decaying all isotopes in which the parent has the longest half-live for 7hl of the parent • all_decay_results.pickle – composition of 3-day decay of all t½ > 7d nuclides • all_decay_results_7hl_3d.pickle – all_equilibria plus 3 days extra decay • Additional pickles with the compositions & emissions of WGPu, LEU, etc.