Abstract
The future PLINIUS-2 platform of CEA Cadarache will be dedicated to the study of corium interactions in severe nuclear accidents, and will host innovative large-scale experiments. The Nuclear Measurement Laboratory of CEA Cadarache is in charge of real-time high-energy X-ray imaging set-ups, for the study of the corium-water and corium-sodium interaction, and of the corium stratification process. Imaging such large and high-density objects requires a 15 MeV linear electron accelerator coupled to a tungsten target creating a high-energy Bremsstrahlung X-ray flux, with corresponding dose rate about 100 Gy/min at 1 m. The signal is detected by phosphor screens coupled to high-framerate scientific CMOS cameras. The imaging set-up is established using an experimentally-validated home-made simulation software (MODHERATO). The code computes quantitative radiographic signals from the description of the source, object geometry and composition, detector, and geometrical configuration (magnification factor, etc.). It accounts for several noise sources (photonic and electronic noises, swank and readout noise), and for image blur due to the source spot-size and to the detector unsharpness. In a view to PLINIUS-2, the simulation has been improved to account for the scattered flux, which is expected to be significant. The paper presents the scattered flux calculation using the MCNP transport code, and its integration into the MODHERATO simulation. Then the validation of the improved simulation is presented, through confrontation to real measurement images taken on a small-scale equivalent set-up on the PLINIUS platform. Excellent agreement is achieved. This improved simulation is therefore being used to design the PLINIUS-2 imaging set-ups (source, detectors, cameras, etc.).
Highlights
T HE study of severe nuclear accidents is a major research topic at CEA (French atomic energy agency)
The PLINIUS-2 imaging set-ups will rely on the same principle as KROTOS on which the simulation was validated, i.e. radiography using a linear electron accelerator (LINAC) and phosphor screens coupled to sCMOS cameras
We have presented real-time X-ray imaging which is a high value-added feature of severe nuclear accidents study performed at CEA in Cadarache
Summary
T HE study of severe nuclear accidents is a major research topic at CEA (French atomic energy agency) In this scope, the PLINIUS experimental platform situated in. Among the test facilities of PLINIUS, the KROTOS facility studies the corium-water interaction, through the release of corium into a water tank [2] It includes high-frequency X-ray imaging through the whole process, which allows a worldwide unique real-time visualization of the reaction [3] (see Fig. 1). High-energy X-ray imaging will be required on three experiments of PLINIUS-2: the test sections for water-corium interaction and sodium-corium interaction study, and the stratification process study. Higher attenuation than in KROTOS is expected on these bigger test columns In this scope, the design of imaging set-ups is carefully examined and.
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