Neutronic behavior of reactor moderated by mixtures of light and heavy waters at different ratios

Neutron absorption profile in a reactor moderated by different mixtures of light and heavy waters

“…It is noticeable that the fraction of neutrons that are absorbed in the control rods is inversely proportional to the neutrons' spectral hardening in the reactor. It was demonstrated in an earlier work of the authors (Nagy et al, 2014) that the neutron spectrum is increasingly hardened with increase of heavy water percentage in moderator till 90% D 2 O, and then it becomes less hard. As the neutron spectrum becomes harder, more neutrons are competitively captured in 238 U and hence less neutrons are available for absorption in the control rods.…”

“…Earlier studies of the mixed heavy/light water moderator of nuclear reactors showed that the neutron spectrum in a reactor is hardened as the percentage of heavy water in its moderator increases (Wehmeyer et al, 1962;Barrett et al, 1962;Tochihara et al, 1998;Nagy et al, 2014). An earlier work of the authors (Nagy et al, 2014) on the neutronic behavior of a nuclear reactor moderated by different mixtures of heavy/light waters showed that the total mass of control rods needed to attain criticality in reactor did not linearly decrease with increase of the heavy water percentage in moderator.…”

“…More details of the materials used in the components of the LR-0 reactor model can be found in appendix A of a previous paper for the authors (Nagy et al, 2014).…”

“…An earlier work of the authors (Nagy et al, 2014) on the neutronic behavior of a nuclear reactor moderated by different mixtures of heavy/light waters showed that the total mass of control rods needed to attain criticality in reactor did not linearly decrease with increase of the heavy water percentage in moderator. This non-linearity was presumed to be due to the neutron spectral shift, that called for further exploration of the neutron absorption profile in control rods at different mixed heavy/light water moderator mixtures.…”

Investigation of a new approach for regulating the reactivity and achieving economic feasibility using thorium in a blanket‐seed assembly of pressurized water reactors

“…The spectral shift reactor control is involved in the neutron spectrum hardening at BOL; therefore, the excess neutrons are absorbed in the fertile isotopes rather than in burnable absorbers materials, then the neutron spectrum is shifted back to the thermal region at the EOL 13,14 . The neutron spectrum shift can be achieved mechanically by changing the moderator‐to‐fuel ratio 15,16 or by using a moderator of light‐heavy water mixture 17,18 …”