13-18 May 2018
Casino Conference Centre
Europe/Prague timezone

## Technetium separation from concentrated molybdate solution issuing recycling of molybdenum from irradiated CerMet nuclear fuel

14 May 2018, 17:15
1h 30m
Gallery (Casino Conference Centre)

### Gallery

#### Casino Conference Centre

Poster Separation Methods, Speciation

### Speaker

Martin Daňo (Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Nuclear Chemistry)

### Description

In the Partitioning and Transmutation (P&T) technology, minor actinides burning to shorter-lived radionuclides can happen in Accelerator-Driven Transmuters (ADT) or in the GEN IV nuclear reactors. Among the fuel matrices considered to embed minor actinides for burning, inert matrices composed of molybdenum metal (CerMet fuel) or inert ceramic magnesium oxide matrix (CerCer fuel) are high on the list of candidates.
Molybdenum-based CerMet fuels have an excellent thermal conductivity, however they require use of molybdenum with specific isotopic composition. $^{99}$Mo is the recommended isotope for ADT. A multi-recycling process of spent Mo-based CerMet fuels should hence include recycling of the isotopically manipulated molybdenum. In addition to separating the bulk transmuted radionuclides, separation of the residual inventory of radionuclidic impurities may be required prior to manufacture of new CerMet fuel from the re-cycled molybdenum. Among these potential impurities, $^{99}$Tc was identified.
Therefore, this study is focused on elimination of technetium (TcO$_4$$^{–}) from concentrated molybdenum solutions. A336-PAN(HNO_3) solid phase extractant has been identified and tested for this purpose. Based on the proposed reprocessing scheme of CerMet fuels, molybdate model solution with Mo concentration 100 g L^{–1} and pH = 9.1 was used. Although the pH 9.1 is given by dissolving MoO_3 in ammonia solution, it was found that in the range of pH 8.1 – 10.2 the extraction percentage varies by only about 0.8 %. In the conditions used, the maximum value of the extraction percentage corresponds to 99.1 %. This fact shows that small pH deviations will not have significant effect on the extraction process. Uptake of TcO_4$$^{–}$ is not very fast, the equilibrium is reached within 30 minutes. The dependence of weight distribution ratio (D$_g$) on molybdenum concentration in batch experiment revealed that D$_g$ values decrease with increasing molybdenum concentration. This decrease can be ascribed to the competition of NH$_4$$^{+} ions from ammonium dimolybdate. The highest D_g was reached for 10 g L^{–1} of Mo. Somewhat surprisingly, the lowest D_g (D_g ~ 0 mL g^{–1}) was found in absence of molybdenum. The probable reason may be associated with the low ionic strength of deionized water. Even at the molybdenum concentration 100 g L^{–1} Mo, the weight distribution ratio of technetium is sufficient for practical application (D_g = 24⋅10^{3} mL g^{–1}). The extraction capacity (Q_m) of A336-PAN(HNO_3) for TcO_4$$^{–}$ was investigated using the perrhenate carrier. The extraction isotherm, determined by batch technique, revealed that the maximum extraction capacity of A336-PAN(HNO$_3$), corresponding to the solid extractant saturation, is equal approximately to 1 mmol g$^{–1}$.
This study was supported by ASGARD Project supported by EU within 7th Framework Programme (EC-GA No. 295825), by grant SGS12/199/OHK4/3T/14 and SGS15/216/OHK4/3T/14.

### Primary authors

Kamil Vavřinec Mareš (Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Nuclear Chemistry) Jan John (Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Nuclear Chemistry) Ferdinand Šebesta (Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Nuclear Chemistry) Martin Daňo (Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Nuclear Chemistry)

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