Abstract
Thermal neutron scattering data have an important influence on the high-fidelity neutronics calculation of thermal reactors. Due to the limited storage capabilities of computers, a discrete ACE representation of the secondary neutron energy and angular distribution has been used for Monte Carlo calculation since the early 1980s. The use of this discrete representation does not produce noticeable effects in the integral calculations such as keff eigenvalues, but can produce noticeable deficiencies for differential calculations. A new continuous representation of the thermal neutron scattering data was created in 2006, but was not widely known. Recently, the continuous representation of the thermal neutron scattering ACE data based on ENDF/B-Ⅷ.0 library was officially released and was available for all users. The new representation shows great difference compared with the discrete one. In order to utilize the more physical and rigorous representation data for high fidelity neutronic-thermohydraulic coupling calculation, the on-the-fly treatment capability was proposed and implemented in RMC code. The two-dimensional linear-linear interpolation method was used to calculate the inelastic scattering cross sections and the secondary neutron energies and angles. The on-the-fly treatment capability was tested by a pressurized water reactor assembly. Results show that the on-the-fly treatment capability has high accuracy, and can be used to consider the temperature feedback in the neutronic-thermohydraulic coupling calculations. However, the efficiency of the on-the-fly treatment still need to be improved in the near future.
Highlights
Thermal neutron scattering data have an important influence on the high-fidelity neutronics calculation of thermal reactors
The second part of this paper gives a brief introduction to the continuous thermal neutron scattering data, the third part presents the detailed interpolation method for the on-the-fly treatment capability, the test cases and results are given in the fourth part, and a conclusion was drawn in the final part
The ENDF/B-VIII.0 based neutron ACE files were generated by using NJOY2016 [12]
Summary
Thermal neutron scattering data have an important influence on the high-fidelity neutronics calculation of thermal reactors. To overcome the inherent deficiencies of the discrete representation, a new continuous ACE representation for the thermal neutron scattering data was firstly created by Los Alamos National Laboratory in 2007 [5]. In the lasted ENDF/B-VIII.0 [8] data libraries, only the continuous ACE representation of the thermal neutron scattering data were provided by Los Alamos National Laboratory (LANL). In order to utilize the more physical and rigorous representation thermal neutron scattering data for high fidelity neutronics calculations, the continuous thermal neutron scattering data processing capability in Reactor Monte Carlo code RMC [9] has been developed and was introduced in our previous work[10]. The on-the-fly treatment capability for the continuous representation thermal neutron scattering data was developed to consider the temperature feedback effect in the neutronic-thermohydraulic coupling calculations. The second part of this paper gives a brief introduction to the continuous thermal neutron scattering data, the third part presents the detailed interpolation method for the on-the-fly treatment capability, the test cases and results are given in the fourth part, and a conclusion was drawn in the final part
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