Chronomorphic characterization and radiolytic degradation analysis of polyurethane with monte carlo modeling of the neutron spectra surrounding age pettrace cyclotron
This thesis describes the development of fast neutron irradiation positions at the MURR GE PETtrace cyclotron for polyurethane (PUR) radiolysis studies. Monte Carlo N-Particle (MCNP) Transport code was used to calculate the fast neutron flux spectra and absorbed neutron dose at the irradiation positions during routine fluorine-18 production. The calculated MCNP neutron flux is validated using neutron activation threshold foils with spectrum unfolding techniques. The a priori MCNP flux and experimentally measured flux spectra are ultimately shown to validate using TENDL-2015 cross section data for neutron production reactions by comparing results with CEM03.03, BERTINI INC, and INCL physics models within MCNP. Following irradiation of PUR, the degree of radiolysis was analyzed using attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) to quantify neutron dose dependent changes. Collectively, the results show that PURs do not appear to be affected up to doses of 5 kGy and should be considered for use in radiation fields.