Study of thermal to 14MeV neutron conversion in Triga reactor: application to averaged cross section measurement

Thermal-to-fusion neutron convertor and Monte Carlo coupled simulation of deuteron/triton transport and secondary products generation

“…In 1985, Perry calculated conversion efficiency and fusion spectra by numerical integral. While Professor EI Bardouni simulated this process with Monte Carlo method [4] in 1996, then measured the conversion efficiency with threshold activation foils in 1997 [5], and applied this convertor to averaged cross section measurement in 2004 [6]. Meanwhile, such research has also been performed in Russia [7,8] this decade.…”

“…While the peak moves to 160 keV for triton as incident particle. Along with slowing down in the target, the triton will produce fusion neutrons by the reaction of D(T, n) 4 H, 6 Li(T, n) 8 Be and 7 Li(T, n) 10 It's quite challenging to simulate this reaction sequence. r Designed for high energy physics, simulation results of current condensed history Monte Carlo codes, such as MCNPX, GEANT, FLUKA, are not good enough for ionization track at low energy (<40 MeV) [12].…”

“…For a certain initial triton energy triton, this quantity is related only with target materials. One triton with 2.73 MeV initial energy, produces about 2.32 Â 10 À4 fusion neutrons in infinite volume pure 6 LiD sample. Another conclusion can be make form Fig.…”

“…It should be noticed that, because of the large neutron absorption cross section of Li-6, about 30% of (n, T) reactions will occur in near surface (70 lm, triton range) for direct incident or 47% for isotropic incident, with 0.0253 eV neutron into pure 6 LiD. Tritons generated in this region have a large probability of escaping out of convertor materials.…”

“…7 illuminates the results of mono-energy neutron of different energy injecting upon 1 mm pure 6 LiD convertor with density of 0.7874 g/cm 3 , including: (a) fusion neutron yield per million neutrons absorbed in LiD; (b) fusion neutron yield per million neutrons incident upon the sample; (c) probability of neutron absorption by Li-6 for every incident neutron; (d) triton leakage out of sample from surfaces after it generated. For the vertical incident of thermal neutron with Maxwell spectrum upon 6 LiD, the conversion ratio of 1 mm 6 LiD is about 2.15 Â 10 À4 every incident neutron, or 2.18 Â 10 À4 per absorbed neutron, which is the same as William H. MILLER's measurement results [2] of 2.1 Â 10 À4 , whose experimental was more reliable, which was carried out using ''A'' beam port of the University of Missouri Research Reactor, where the incident direct neutron beam was a typical thermal distribution, with long counter detecting the 14 MeV fusion neutrons. Fusion neutron spectrum has also been counted in Fig.…”