[en] In France a probabilistic risk assessment (PRA) is presently in progress in the Safety Assessment Department of CEA for a standardized 900 MW PWR plant. Indeed, the French safety approach for severe accidents management is the implementation of a set of special emergency procedures which identify the optimal actions even for out of design situations. So by accounting for these procedures (correctly or incorrectly applied) an important set of operator actions can be included in the PRA. This approach implies the introduction of the notion of procedure failure at the level of the Event Trees. Quantification of the corresponding probabilities leads to several problems as physical efficiency of the procedures, systems availability (including instrumentation), and human behavior. Among these problems the physics of the sequence is a primary question, both to state the efficiency of the procedure to prevent a core damage, and to assess the allowable time for the operator actions. So a set of thermohydraulic studies was initiated for various accident sequences and procedures. The authors present the example of the small LOCA Event Trees and the studies related to the introduction of procedure actions in case of HPSI failure. The results illustrate the interest of the approach and its significant impact on the PRA

[en] Irradiation of silicon P.I.N. junction has been studied primarily for the purpose of developing a radiation damage dosimeter, but also for the purpose of investigating silicon itself. It is known that the rate of recombination of electrons and holes is a linear function of defects introduced by neutron irradiation. Two methods have been used to measure that rate of recombination: forward characteristic measurements, recovery time measurements. In order to explain how these two parameters depend on recombination rate we have given a theory of the P.I.N. junction. We have also given an idea of the carrier lifetime dependence versus temperature. Annealing effects in the range of 70 to 700 K have also been studied, we found five annealing stages with corresponding activation energies. As an application for these studies, we developed a radiation damage dosimeter with which we made several experiments in facilities such as Naiade or Marias. (author)

No abstract available

No abstract available

[en] The two probabilistic safety assessments of 900MWe and 1300MWe Pressurized Water Reactors (PWRs) recently completed in France constitute an important knowledge resource for the assessment of PWR safety. One innovative feature of this research programme, which yielded many valuable lessons, comes from the fact that plant shutdown state and long term post-accident conditions were fully taken into account. (author)