Monte Carlo N-particle simulation of neutron-based sterilisation of anthrax contamination

Objective: To simulate the neutron-based sterilisation of anthrax contamination by Monte Carlo N-particle (MCNP) 4C code. Methods: Neutrons are elementary particles that have no charge. They are 20 times more effective than electrons or γ-rays in killing anthrax spores on surfaces and inside closed containers. Neutrons emitted from a ²⁵²Cf neutron source are in the 100 keV to 2MeV energy range. A 2.5MeV D-D neutron generator can create neutrons at up to 10¹³ ns^-1 with current technology. All these enable an effective and low-cost method of killing anthrax spores. Results: There is no effect on neutron energy deposition on the anthrax sample when using a reflector that is thicker than its saturation thickness. Among all three reflecting materials tested in the MCNP simulation, paraffin is the best because it has the thinnest saturation thickness and is easy to machine. The MCNP radiation dose and fluence simulation calculation also showed that the MCNP-simulated neutron fluence that is needed to kill the anthrax spores agrees with previous analytical estimations very well. Conclusion: The MCNP simulation indicates that a 10 min neutron irradiation from a 0.5 g ²⁵²Cf neutron source or a 1 min neutron irradiation from a 2.5MeV D-D neutron generator may kill all anthrax spores in a sample. This is a promising result because a 2.5MeV D-D neutron generator output >10¹³ n s ^-1 should be attainable in the near future. This indicates that we could use a D-D neutron generator to sterilise anthrax contamination within several seconds.