Neutron Field Measurements in Phantom with Foil Activation Methods

摘要

The threshold neutron-foil spectrometry method, utilizing the SAND II spectrum unfolding code, was evaluated by carrying out a measurement in the standard fission source facility, simultaneous with six (6) in-phantom measurements of neutron spectra. The foil spectrometry was done with the full set of threshold foils, mid-thorax in ER1, where a 2 in. lead wall separated reactor and phantom. A five-foil set was utilized for the phantom mid-head and phantom hip measurements in ER1, as well as for mid-thorax, mid-head and hip in ER2, free field. Calculations of the mid-thorax and mid-head spectra in ER1 and ER2 were carried out, with the source term normalized to nickel foil activations at the reactor entrance window. A simple 5-foil perturbation method for neutron dosimetry, utilizing hand calculations, was developed and evaluated for the ER1 and ER2 spectra. It appears to be the order of 6 percent accurate versus 3-4 percent for SAND II, which utilizes the best (calculated) a prior data available for spectral shape information.