Development of the pile oscillation method for the determination of integral cross section data at the AKR-2 training and research reactor

The development of Generation-IV reactors requires validated low uncertainty nuclear data for novel materials. To address this, the pile oscillation method for measuring integral absorption cross sections has been developed at the AKR-2 research reactor at Dresden University of Technology. The experimental setup consists of a linear motor-driven oscillator, four He-3 proportional counters, and a custom FPGA-based data acquisition system that records individual neutron events. Signals are transformed to the frequency domain, and cross-power spectral density analysis is used to determine the sample’s reactivity worth while minimizing biases. The method was validated against Monte Carlo simulations using Serpent 2.2.1. Measurements on foils of various natural materials, including gold, indium, iridium, copper, hafnium, zirconium, and carbon, were performed. Excellent agreement was found for strong absorbers like indium and iridium, with calculated-to-experimental ratios deviating by less than 6%, accurately reproducing self-shielding effects. As expected, larger deviations were observed for weakly absorbing materials such as copper and carbon, confirming the method’s performance characteristics. These results demonstrate that the developed experimental design, data acquisition, and analysis techniques provide a validated and reliable tool for obtaining integral cross-section data, supporting the validation of nuclear data libraries and the safety assessment of advanced reactor designs.