Neutron transmission experiment with PTFE at AKR-2

Fluorine is a crucial element for the nuclear industry and technology due to its application in nuclear fuel production as uranium hexafluoride (UF$_6$), its use of Teflon® in criticality experiments, and its use in coolant/fuel materials in several Molten Salt Reactor (MSR) concepts currently being designed. There have been many efforts to improve the neutron reaction cross sections for fluorine. The neutron broad-beam transmission experiment through the PTFE (PolyTetraFluoroEthylene) block at the Dresden AKR-2 reactor has been performed to validate existing evaluated cross-section libraries from 1 to 10 MeV of incident neutron energies. Calculations with studied data sets (ENDF/B-VIII.0, INDEN, JEFF-3.3, and JENDL-5) show satisfactory agreement with the experiment in the energy region above 2.1 MeV within the uncertainty range. The measured neutron transmission shows a systematic disagreement in a calculation to experiment comparison in the energy region 1–2.1 MeV. This behavior is consistent with the measured $^{252}$Cf(s.f.) neutron leakage in the PTFE block with dimensions of 60 × 50 × 50 cm. Improvement of evaluated cross sections below 2 MeV of neutron incident energy is needed.