about half that for equivalent MOX fuels at the same burn-up, but the linear power
was lower than in equivalent U-MOX studies. Taking into account experimental
uncertainties, the fuel behavior seems to be at least as good as U-MOX.
The THORIUM CYCLE project was completed in 2006, but the postirradiation
experiments were performed under a subsequent experiment called
LWR-DEPUTY (coordinator, SCK.CEN). In this program, the main tests on
Th-MOX consisted of additional fuels studies (microscopy, radial distributions of
elements and isotopes) and radiochemical analyses. The objective of these analyses
was to obtain a reliable experimental database for burn-up analysis and to evaluate
changes in the heavy nuclide content:
• To optimize the dissolution and analysis strategies
• To establish the first dataset on heavy nuclide and fission product content in
irradiated Th-MOX to assess the overall uncertainties
• To use this dataset in a benchmark analysis program
The OMICO Project [4] was conducted from 2001 to 2007. Its scope included
the study and modeling of the influence of microstructure and matrix composition
on Th-MOX fuel in-pile behavior in normal PWR conditions. The following tasks
were undertaken:
• Fabrication of the Th-MOX fuels at the JRC-ITU
• Irradiation in the “CALLISTO” PWR loop in BR2, representing real PWR
conditions; the burn-up achieved at the end of this project was about 13 GWd/
tHM
• Nondestructive examinations (gamma-spectrometry, visual examinations) and
microstructure studies
It should be noted that the pins were instrumented for pressure and fuel temperature determination. The test matrix was such that the Th-MOX could be compared
with U-MOX and UO 2 fuels. Another test parameter consisted of the fabrication
process (homogeneous versus heterogeneous powder mixtures). The results of the
temperature/pressure readings were primarily used to benchmark computer code
models for Th-MOX fuels behavior in the first stage of their life.
Besides the irradiation, fuel characterization was performed, including thermal
diffusivity measurements, and the results were published [4, 9]. The results show a
similar thermal conductivity for (nonirradiated) Th-MOX as compared to U-MOX.
In the LWR-DEPUTY [5] project, selected samples of the OMICO and THORIUM CYCLE programs were extensively studied to provide experimental datasets
suitable for evaluating their in-pile performance. The experimental data were the
basis of a benchmark exercise on the Th-MOX fuel pin irradiated at the NPP KWO
to investigate the qualification of the numerical tools and software packages. A
scoping study of the leaching behavior was also conducted. In addition to the
experimental work, steady-state and transient analyses were performed for different
PWR designs fueled completely or partially with Th-MOX fuel. An assessment of
steady-state parameters (reactivity, shutdown margin, and reactivity feedback coefficients) has been performed in comparison with UO 2 . All feedback coefficients are
18 Overview of European Experience with Thorium Fuels
201
was lower than in equivalent U-MOX studies. Taking into account experimental
uncertainties, the fuel behavior seems to be at least as good as U-MOX.
The THORIUM CYCLE project was completed in 2006, but the postirradiation
experiments were performed under a subsequent experiment called
LWR-DEPUTY (coordinator, SCK.CEN). In this program, the main tests on
Th-MOX consisted of additional fuels studies (microscopy, radial distributions of
elements and isotopes) and radiochemical analyses. The objective of these analyses
was to obtain a reliable experimental database for burn-up analysis and to evaluate
changes in the heavy nuclide content:
• To optimize the dissolution and analysis strategies
• To establish the first dataset on heavy nuclide and fission product content in
irradiated Th-MOX to assess the overall uncertainties
• To use this dataset in a benchmark analysis program
The OMICO Project [4] was conducted from 2001 to 2007. Its scope included
the study and modeling of the influence of microstructure and matrix composition
on Th-MOX fuel in-pile behavior in normal PWR conditions. The following tasks
were undertaken:
• Fabrication of the Th-MOX fuels at the JRC-ITU
• Irradiation in the “CALLISTO” PWR loop in BR2, representing real PWR
conditions; the burn-up achieved at the end of this project was about 13 GWd/
tHM
• Nondestructive examinations (gamma-spectrometry, visual examinations) and
microstructure studies
It should be noted that the pins were instrumented for pressure and fuel temperature determination. The test matrix was such that the Th-MOX could be compared
with U-MOX and UO 2 fuels. Another test parameter consisted of the fabrication
process (homogeneous versus heterogeneous powder mixtures). The results of the
temperature/pressure readings were primarily used to benchmark computer code
models for Th-MOX fuels behavior in the first stage of their life.
Besides the irradiation, fuel characterization was performed, including thermal
diffusivity measurements, and the results were published [4, 9]. The results show a
similar thermal conductivity for (nonirradiated) Th-MOX as compared to U-MOX.
In the LWR-DEPUTY [5] project, selected samples of the OMICO and THORIUM CYCLE programs were extensively studied to provide experimental datasets
suitable for evaluating their in-pile performance. The experimental data were the
basis of a benchmark exercise on the Th-MOX fuel pin irradiated at the NPP KWO
to investigate the qualification of the numerical tools and software packages. A
scoping study of the leaching behavior was also conducted. In addition to the
experimental work, steady-state and transient analyses were performed for different
PWR designs fueled completely or partially with Th-MOX fuel. An assessment of
steady-state parameters (reactivity, shutdown margin, and reactivity feedback coefficients) has been performed in comparison with UO 2 . All feedback coefficients are
18 Overview of European Experience with Thorium Fuels
201