3D reconstruction from incomplete Fourier spectra: An extrapolation approach

3D reconstruction from an incomplete data set is an ill-posed problem. To overcome this drawback, an approach based on constrained optimization is introduced. This approach provides a powerful mathematical framework for selecting a specific solution from the set of feasible solutions; this is done by minimizing some criteria depending on prior densitometric information. We propose a global optimization scheme using a deterministic relaxation algorithm based on Bregman's algorithm associated with half-quadratic minimization techniques. When used for 3D vascular reconstruction from 2D Digital subtracted Angiography (DSA) data, such an approach allows reconstructing well-contrasted 3D vascular network in comparison with results obtained by using standard algorithms. 1 Introduction In many computer imaging applications, such as medical, astronomical, or geophysical imaging, the measured data result from the transformation of an unknown physical parameter. The recovery of the physical param..

SAIGA : an in-pile test largely instrumented and devoted to study the degradation of a Sodium Fast Reactor core with mitigation device in Severe Accident Conditions

International audienceAfter the end of ASTRID conceptual design studies, CEA has launched a long-term R&D roadmap on generic Sodium Fast Reactor issues including the Severe Accident field based on 3 pillars:- Improving knowledge of the phenomena and equations governing the sequence of events occurring during a severe accident. Developing existing or future calculation codes and numerical platforms focusing specifically on severe accidents in order to sequence and couple these codes;- Extend the experimental database needed to validate the calculation and simulation tools, such as SIMMER-V code, to cover the ranges of the parameters expected in future reactors incorporating advanced design options;- Qualify innovative systems for mitigating the consequences of radioactive emissions in severe accident conditions proposed for future reactors.Transfer Tubes have been installed in recent SFR core designs so that molten core can rapidly relocate out of core region. The objective is to prevent prompt criticality in the core region by removing sufficiently rapidly a significant mass of fissile material. This mitigation device is designed to help return the reactor to a safe state after a severe accident. SAIGA Project will provide experimental results of an integral test to validate SIMMER-V calculations on Corium Transfer Tube