New KeV neutron scattering array for measurements of zirconium

Abstract

Nuclear data measurements are used to supplement nuclear interaction theory to develop evaluated nuclear data libraries when the theory is not sufficient to deduce reaction probabilities from first principles. These nuclear data libraries are widely used to model and simulate nuclear phenomena. The Evaluated Nuclear Data File (ENDF) is maintained by Brookhaven National Laboratory (BNL) in the United States of America, while the Joint European Fission and Fusion (JEFF) library is maintained in Europe and the Japanese Evaluated Nuclear Data Library (JENDL) is maintained in Japan. There are many applications that model systems with neutron radiation, from commercial nuclear power plants to nonproliferation and nuclear weapons. Cross section measurements are performed at the Rensselaer Polytechnic Institute (RPI) Gaerttner Linear Accelerator (LINAC) Center. Different types of reactions are measured with many detector systems.

Zirconium scattering was measured in two samples: 4 cm and 2 cm thicknesses. Detectors were placed at four angles, with two detectors at each angle: 35 degrees, 70 degrees, 115 degrees, and 150 degrees. The zirconium scattering measurements revealed that the extension of the resolved resonance region in ENDF/B-VIII.0 and JENDL 4.0 better fits the measured data. Also, the JENDL 3.3 angular distribution over-predicts backscattering in the URR to fast energy region. The ENDF/B-VIII.0 or JENDL 4.0 evaluated nuclear data libraries should be used for simulations that are sensitive to zirconium scattering.

This work will discuss measuring neutron scattering interactions with a detector system designed as part of this thesis. Measured neutron scattering data in the keV energy region are compared to a detailed simulation of the scattering experiment with different data libraries input for the sample material of interest. The comparison of simulations with different evaluated nuclear data libraries to the scattering data highlights where the scattering cross section and angular distributions differ from the observed experimental data. Knowledge of these inaccuracies in the cross section and angular distributions can be used to improve future nuclear data evaluations. Neutron scattering in zirconium in the keV energy range is of interest to the nuclear community because of the use of zirconium in nuclear reactors due to its mechanical strength and low neutron capture cross section. An experiment was developed at RPI to measure scattering in the keV energy range with lithium glass detectors. A new detector array was designed, built, and tested for this purpose.