Neutron-based sterilization of anthrax contamination.

With the anthrax threat becoming a reality, it is very important to have an effective way to sterilize areas contaminated by anthrax. Anthrax spores are the dormant form of the anthrax bacteria. They can germinate in tissues, producing new bacteria that release lethal toxins. Neutrons can be a powerful tool in our defense against anthrax contamination. Neutrons are elementary particles that have no charge, which allows them to be very penetrating, killing the anthrax spores on the surface and inside the containers. So neutrons have an advantage over other forms of radiation if deep penetration is required to kill biological organisms. A Cf neutron source allows for a low cost method of decontamination. It emits most neutrons in the 100 keV to 2 MeV energy regions, and a neutron in this energy region is 20 times more deadly than electrons or gamma rays in killing anthrax spores. If we just consider the first neutron collision with anthrax spores and that all the anthrax spores will not survive at the dose level above 2.0 x 10 Gy, our calculations show that a 0.5-g Cf neutron source within 20 min can generate 1.11 x 10 m fluence neutrons, which is good enough to kill the anthrax spores on the sample. An experimental confirmation of the above results may prove that to achieve 1.11 x 10 m fluence neutrons on the anthrax spore sample, the neutron irradiation time may be reduced dramatically or the Cf neutron source reduced to 0.1 g level or even less. The aim of this paper is to evaluate a feasible way to sterilize the anthrax contamination by using a Cf neutron source. Presently, we are mainly concentrating on the theoretical estimation of neutron fluence to see if the Cf neutron source can deliver enough neutron irradiation dose to kill the anthrax spores. Our future work will focus on experimental confirmation and Monte Carlo simulation by using Geant4 or MCNP codes. At that time, we will consider the effects of the real experimental setup, the shielding materials, the exact chemical components, and the biological structures of anthrax spores. We also need to consider the ways of carrying the anthrax spores, and this includes surface contamination, inside an envelope, or hidden in sealed metal containers and luggage.