Neutronic properties of high-temperature gas-cooled reactors with thorium fuel

Peculiarities of the radiation formation in dispersed microencapsulated nuclear fuel

“…Three types of fuel pellets designated 0817, 1017 and 1200 were used in (Shamanin et al 2018); the authors have shown that an increase in the fuel pellet diameter leads to a smaller fraction of graphite and a reduced reactivity margin r inf (t), and the reactor life depends on the initial quantity of 239 Pu and 232 Th and on the quantity of the 241 Pu and 233 U formed. When a fuel pellet of the type 0817 is used, 239 Pu burns out rapidly and 233 U and 241 Pu do not have enough time to accumulate in such quantity as required for maintaining the steady-state fission reaction.…”

“…In (Shamanin et al 2015, Shamanin et al 2016, the author studied the physics of a small high-temperature gas-cooled thorium reactor plant (НGTRU, Russia), and selected the best reactor core configuration and the best nuclear fuel material composition. The reactor considered in (Shamanin et al 2018) is capable to operate for not less than 3000 effective days at a power level of 60 MW. Peculiarities of the reactor core design, the material composition of dispersed microencapsulated nuclear fuel (microfuel), and operating conditions affect the radiation characteristics of fuel and require traditional nuclear fuel handling procedures to be revised at the reactor design stage.…”

“…In such studies, the yield q sf and the spectral distribution (spectrum) of spontaneous fission neutrons S sf (E) are comparatively easy to determine. For this reason, of greater interest is determination of the ratio of the quantity of the neutrons q an formed as a result of (a, n) reactions to the quantity of the neutrons resulting from spontaneous (q sf ) and induced (q f ) fission (in the event of large-size spent nuclear fuel (SNF) blocks) which is of interest both for calculating the neutron radiation dose rate during handling of such fuel Zabrodskaya 2005, Dulin andMatveyenko 2002) and in using the Rossi alpha method to determine the multiplication factor (k eff ) in subcritical systems (Dulin and Matveyenko 2002), such as the НGTRU fuel block (Shamanin et al 2018). This problem was examined rather thoroughly and solved in (Vlaskin et al 2015, Bulanenko 1979, Dulin and Zabrodskaya 2005, Dulin and Matveyenko 2002, Shamanin et al 2017, Bogatov et al 2015) and as part of other studies for fuel in the form of homogeneous dioxide.…”

“…Such studies are conducted with the use of verified codes and dedicated programs. It often turns out during numerical modeling of radiation fields and in development of new procedures and regulations for the SNF handling in a nuclear fuel cycle of a new generation (Shamanin et al 2018, Bogatov et al 2015, Glukhov et al 2016, Spirin et al 2015 that no standard codes can be used without respective scientific rationale and upgrades. For instance, the ORIGEN-S code enables determination of the nuclear fuel nuclide composition and the spectral composition of the SNF neutron and photon radiation sources depending on burn-up and decay time.…”

“…The nuclear reactor considered in (Shamanin et al 2018) is a reactor plant using prompt neutrons (~63.03 % of neutrons with an energy of 4 eV to 183 keV) and fast neutrons (~24.5 % of neutrons with an energy of 183 keV to 10 MeV) with the (Th,Pu)O 2 composition used as nuclear fuel. The (a, n) reaction can run in the nuclear fuel of such reactor not only on 17,18 O isotopes but also on 13 С and 29,30 Si contained in the microfuel (Ti 3 SiC 2 ) and fuel pellet (SiC) coatings.…”