Synthesis and investigation of neptunium zirconium phosphate, a member of the NZP family: crystal structure, thermal behaviour and Mössbauer spectroscopy studies

A new double neptunium zirconium phosphate of the type MxZr2(PO4)3 (M = Np), crystallizing in the structure type NaZr2(PO4)3 (NZP, NASICON), was synthesized by solid state reactions at high temperatures and characterized by X-ray diffraction, infrared spectroscopy and Mössbauer spectroscopy. The Rietveld refinement of the XRD pattern together...

Fission product partitioning in aerosol release from simulated spent nuclear fuel

Aerosols created by the vaporization of simulated spent nuclear fuel (simfuel) were produced by laser heating techniques and characterised by a wide range of post-analyses. In particular attention has been focused on determining the fission product behaviour in the aerosols, in order to improve the evaluation of the source term and consequently...

Thermodynamic assessment of the LiF–ThF4–PuF3–UF4 system

The LiF–ThF4–PuF3–UF4 system is the reference salt mixture considered for the Molten Salt Fast Reactor (MSFR) concept started with PuF3. In order to obtain the complete thermodynamic description of this quaternary system, two binary systems (ThF4–PuF3 and UF4–PuF3) and two ternary systems (LiF–ThF4–PuF3 and LiF–UF4–PuF3) have been assessed for...

High temperature phase transition of mixed (PuO2 + ThO2) investigated by laser melting

A laser heating approach combined with fast pyrometry in a thermal arrest method was used to provide new data for the melting/solidification phase transition in mixed (PuO2 + ThO2) at high temperature. At low concentration of ThO2 in PuO2 a minimum in the solidification temperature in the pseudo binary (PuO2 + ThO2) was observed. The minimum was...

Excess heat capacity of the (Li1?xCax)F1+x liquid solution determined by differential scanning calorimetry and drop calorimetry

The work presents the measured heat capacity of the (Li1?xCax)F1+x liquid solution. Four samples with different compositions have been prepared and measured using a Differential Scanning Calorimeter. Since this technique was newly adopted for measuring encapsulated fluoride samples, some modifications were introduced in the standard...

The solidification behaviour of the UO2–ThO2 system in a laser heating study

The high-temperature phase diagram of the UO2–ThO2 system has been experimentally revisited in the present study for the first time since 1970, using a laser heating approach combined with fast pyrometry in a thermal arrest method. The melting/solidification temperature, which is of fundamental information for a reactor design was studied here....

Nuclear Reactor Fuels: Materials with Highly Complex Behaviour

Revisiting the melting temperature of NpO2 and the challenges associated with high temperature actinide compound measurements

This work revisits the melting behaviour of neptunium dioxide, an actinide compound which can be produced in the nuclear fuel during operation, and which has an important impact on the nuclear fuel and waste radioactivity especially on the very long term. The present experimental approach employs remote laser heating under controlled atmosphere...