Reprocessability of molybdenum and magnesia based inert matrix fuels

This work focuses on the reprocessability of metallic 92Mo and ceramic MgO, which is under investigation for (Pu,MA)-oxide (MA = minor actinide) fuel within a metallic 92Mo matrix (CERMET) and a ceramic MgO matrix (CERCER). Magnesium oxide and molybdenum reference samples have been fabricated by powder metallurgy. The dissolution of the matrices was studied as a function of HNO3 concentration (1-7 mol/L) and temperature (25-90°C). The rate of dissolution of magnesium oxide and metallic molybdenum increased with temperature. While the MgO rate was independent of the acid concentration (1-7 mol/L), the rate of dissolution of Mo increased with acid concentration. However, the dissolution of Mo at high temperatures and nitric acid concentrations was accompanied by precipitation of MoO3. The extraction of uranium, americium, and europium in the presence of macro amounts of Mo and Mg was studied by three different extraction agents: tri-n-butylphosphate (TBP), N,Nʹ-dimethyl-N,Nʹ-dioctylhexylethoxymalonamide (DMDOHEMA), and N,N,N’,N’- -tetraoctyldiglycolamide (TODGA). With TBP no extraction of Mo and Mg occurred. Both matrix materials are partly extracted by DMDOHEMA. Magnesium is not extracted by TODGA (D < 0.1), but a weak extraction of Mo is observed at low Mo concentration.

Analysis of Isotopic Contributions to Doppler Coefficients of Inert Matrix Fuels

The Minor Actinides (MA) generated by nowadays PWRs fleet has significant impact on environment and biosphere. Inert Matrix Fuels (IMF) is a possible way to reduce the production and hazard of MA in recent. From neutronic aspect, using the MCNP code with temperature related continuous neutron data, the present paper analyses the isotopic contributions to the Doppler Coefficients of certain types IMF fuels. It is concluded that, the Doppler Coefficients of Al2O3+ZrO2+MgO and ZrO2 based IMF fuels are much smaller than those containing ThO2, since the low neutron absorptions and lacking of resonance broadening of Al, Zr, Mg and O elements. For the same Inert Matrix, Reactor Grade Plutonium (RG-Pu) IMF fuels have more negative Doppler Coefficients than Weapon Grade Plutonium (WG-Pu) IMF fuels, which induce by the more abundance of resonance isotopes 240Pu, 242Pu in RG-Pu. Since the different neutron absorption cross-section profiles, the Er2O3 burnable poison has negative contribution to the Doppler Coefficient, however 10B, a typical 1/v absorber, is on the contrary way.