Main operation procedures for ASTRID gas power conversion system

Until the end of the first part of the basic design phase (2017), the ASTRID project has made the choice of studying a power conversion system (PCS) based on a Brayton cycle with nitrogen as coolant. The justification is related to safety and public acceptance considerations in order to inherently eliminate the sodiumwater and sodium-water-air reactions risks. The objective of the engaged studies is to enhance the level of maturity of the gas PCS. The choice of two PCS of 300 MWe each has been made in order to limit the gas inventory, the size and length of gas pipes as well as maintaining a high level of availability. This paper presents specific operating procedures as start-up and normal shutdown of the plant, scram, rapid shutdowns, gas inventory control system, house load and grid frequency control. The current procedures of the plant and the expected control are presented. A focus will be made on the nitrogen inventory control which takes part of the electric power regulation provided to the grid. Finally some perspectives of remaining operation studies to be performed until the end of 2017 will be presented. Indeed the level of maturity of the gas PCS must be at a similar level compared to the classic watersteam Rankine cycle in order to make the best choice for the future of the sodium fast reactors in terms of better cost-effectiveness and reliability through optimization of the Brayton cycle technology and operations. (author)