Measurement of Thermal Neutron Energy Spectrum and Fluence of the Thermal Column in Xi’an Pulse Reactor

Neutron energy spectrum and fluence of the devices in a reactor are important parameters for the users. In this paper, the thermal neutron spectrum of the thermal column in Xi’an pulse reactor were measurement by the method of time of flight (TOF), and the peak of the energy spectrum is 0.0248±0.0006eV and the neutrons average energy is 0.048±0.001eV. With the spectrum results, the average cross section of ²³⁵U(n,f) and ¹⁹⁷Au(n,γ) were calculated are respectively 92.08barn and 538.86barn. With the average cross sections, we measured the neutron fluence with the fission chamber and ¹⁹⁷Au(n, γ) activation method. The measurements of the two methods are respectively 1.08×10⁹n/m²s and 1.13×10⁹n/m²s. We also calculated the standard uncertainty of the measurements: the energy spectrums’ is less than 5%, and the neutron fluence’ is less than 2.2%.