New composites for neutron radiation shielding.

A castable polyurethane (PUR) with soft segment made by polytetrahydrofuran polyol (or polytretramethylene ether glycol = PTMEG) derived from renewable sources was used as polymer matrix to prepare neutron shields. The PUR polymer matrix was filled with 20.4% of amorphous boron or with 20.9% by weight of hexagonal boron nitride (h-BN). The PUR composites were cast in foils 2 mm thick and tested as thermal neutron shields against reference unfilled PUR foils. The method of sandwitched copper wire activation till saturation was used for the determination of the neutron shielding effectiveness. Both the linear and massic attenuation coefficient of the two PUR composites were determined. Making 100 the linear attenuation coefficient μ of unfilled PUR, the μ value of 20.4% amorphous boron filled composite was found at 224 while that of 20.9% filled BN was found at 182. Making 100 the mass attenuation coefficient μ/ρ of the unfilled PUR the amorphous boron PUR filled composite was found at 311 while the BN filled PUR composite stopped at 178. Unfilled PUR and PUR composites were studied with FT-IR spectroscopy and DSC before and after neutron processing with a total dose of 1.5 × 1013 cm−2. No significant changes were detected neither in the FT-IR spectra nor in the DSC thermal behaviour confirming the excellent radiation resistance of PUR and its suitability as polymer matrix for neutrons and more in general radiation shielding. [ABSTRACT FROM AUTHOR]