Accelerator-Based Biological Irradiation Facility Simulating Neutron Exposure from an Improvised Nuclear Device

Abstract

We describe here an accelerator-based neutron irradiation facility, intended to expose blood or small animals to neutron fields mimicking those from an improvised nuclear device at relevant distances from the epicenter. Neutrons are generated by a mixed proton/deuteron beam on a thick beryllium target, generating a broad spectrum of neutron energies that match those estimated for the Hiroshima bomb at 1.5 km from ground zero. This spectrum, dominated by neutron energies between 0.2 and 9 MeV, is significantly different from the standard reactor fission spectrum, as the initial bomb spectrum changes when the neutrons are transported through air. The neutron and gamma dose rates were measured using a custom tissue-equivalent gas ionization chamber and a compensated Geiger-Mueller dosimeter, respectively. Neutron spectra were evaluated by unfolding measurements using a proton-recoil proportional counter and a liquid scintillator detector. As an illustration of the potential use of this facility we present micronucleus yields in single divided, cytokinesis-blocked human peripheral lymphocytes up to 1.5 Gy demonstrating 3- to 5-fold enhancement over equivalent X-ray doses. This facility is currently in routine use, irradiating both mice and human blood samples for evaluation of neutron-specific biodosimetry assays. Future studies will focus on dose reconstruction in realistic mixed neutron/photon fields.

Metabolic Dysregulation after Neutron Exposures Expected from an Improvised Nuclear Device

“…Neutron irradiations were performed at RARAF, using an accelerator-based neutron irradiator mimicking the neutron energy spectrum from an IND (22). Briefly, a mixed beam of atomic and molecular ions of hydrogen and deuterium were accelerated to 5 MV potential and used to bombard a thick beryllium target.…”

“…To simulate these particular conditions, an accelerator-based neutron irradiation facility was constructed at the Columbia University Radiological Research Accelerator Facility (RARAF; Irvington, NY) (22, 23). The spectrum of neutrons was similar to that encountered in Hiroshima at 1–1.5 km from the epicenter (24), and dosimetry measurements indicated that the neutron exposures contained a ~20% photon dose with neutron energies ranging between 0.2 and 9 MeV, described in detail by Xu, et al .…”

“…The spectrum of neutrons was similar to that encountered in Hiroshima at 1–1.5 km from the epicenter (24), and dosimetry measurements indicated that the neutron exposures contained a ~20% photon dose with neutron energies ranging between 0.2 and 9 MeV, described in detail by Xu, et al . (22). The doses were chosen based on the limited data on IND-spectrum neutrons (25, 26).…”

“…The doses were chosen based on the limited data on IND-spectrum neutrons (25, 26). A calculated RBE of 4, based on micronuclei formation for this particular mixed field (22), was used for the comparative doses in our current studies; namely the neutron doses used were 0.25 and 1 Gy, whereas the X-ray doses used were 1 and 4 Gy. Global metabolomic and lipidomic analyses were performed on urine and serum to identify biomarkers associated with different radiation qualities.…”

THE DECADE OF THE RABiT (2005–15)

“…At this point developments transitioned to optimization of the existing system (7,19) , developing novel bioassays could be performed on the RABiT and testing the existing assays under complex radiation exposure scenarios (20)(21)(22) . The gamma-H2AX and CBMN RABiT assays were transitioned to BARDA funding for further development and rigorous validation in preparation for licensing by the Food and Drug Administration.…”