Experimental demonstration of an isotope-sensitive warhead verification technique using nuclear resonance fluorescence

Abstract

Future nuclear arms reduction efforts will require technologies to verify that warheads slated for dismantlement are authentic without revealing any sensitive weapons design information to international inspectors. Despite several decades of research, no technology has met these requirements simultaneously. Recent work by Kemp et al. [Kemp RS, Danagoulian A, Macdonald RR, Vavrek JR (2016) 113:8618-8623] has produced a novel physical cryptographic verification protocol that approaches this treaty verification problem by exploiting the isotope-specific nature of nuclear resonance fluorescence (NRF) measurements to verify the authenticity of a warhead. To protect sensitive information, the NRF signal from the warhead is convolved with that of an encryption foil that contains key warhead isotopes in amounts unknown to the inspector. The convolved spectrum from a candidate warhead is statistically compared against that from an authenticated template warhead to determine whether the candidate itself is authentic. Here we report on recent proof-of-concept warhead verification experiments conducted at the Massachusetts Institute of Technology. Using high-purity germanium (HPGe) detectors, we measured NRF spectra from the interrogation of proxy "genuine" and "hoax" objects by a 2.52 MeV endpoint bremsstrahlung beam. The observed differences in NRF intensities near 2.2 MeV indicate that the physical cryptographic protocol can distinguish between proxy genuine and hoax objects with high confidence in realistic measurement times.

Selective Isotope CT Imaging Based on Nuclear Resonance Fluorescence Transmission Method

“…If the energy of an incident gamma ray is nearly identical to the excitation energy of an isotope of interest, the isotope is excited and subsequently decays either to the ground state or to an excited state through the emission of a gamma ray. The energy dependence of the NRF cross section is described by the Breit-Wigner resonance [7], [8]. Owing to the dependence of the excitation energies on the nuclear species (isotope), the NRF assay can provide isotope-specific signatures for many materials [1].…”

High-accuracy Geant4 simulation and semi-analytical modeling of nuclear resonance fluorescence

“…Comparison of the semi-analytical model and G4NRF against the experimental data of Ref. [1] is covered in a forthcoming paper [30].…”

“…These discrepancies may introduce systematic uncertainties much larger than our desired accuracy for the verification study; for consistency, then, both the calculations and simulations in this work use an assumed set of cross section parameters (in isotopes relevant to nuclear security applications-see Refs. [1,2]) from various references as shown in Table 1. For the U-238 resonances, preference is given to experimentally-determined (i.e., not ENSDF-evaluated) data; specifically, the integrated cross sections and ratios of widths in Table 1 of Ref.…”

Nanoscale Spatially Resolved Mapping of Uranium Enrichment in Actinide-Bearing Materials

“…The LEU-10Mo was subjected to subsequent thermo-mechanical processing treatments (hot and cold rolling) to form the final fuel foil. Additional sample fabrication details are reported in References [47, 19,17]…”

“…Uranium (U) is the heaviest element naturally occurring in the Earth's crust in significant amounts, and is used both in its natural, processed, and anthropogenic forms. U isotopes are central to a diverse set of scientific disciplines, most notably earth and planetary sciences [1][2][3][4][5][6][7][8], toxicology, environmental monitoring and bioremediation [9][10][11], and the nuclear fuel cycle, forensics, and safeguards [12][13][14][15][16][17][18][19][20][21][22]. Specifically in nuclear fuel cycle applications, the amount of the fissionable U isotope ( 235 U) relative to all U (defined as enrichment) is a critical parameter in fuel performance, and thus impacts economic viability of nuclear power.…”