Transient behavior of ASTRID with a gas power conversion system

Abstract

The present article is dedicated to preliminary transient studies carried out for the analysis of the system overall behavior of the ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration) demonstrator developed in France by CEA and its industrial partners. ASTRID is foreseen to demonstrate the progress made in SFR technology at an industrial scale by qualifying innovative options, some of which still remain open in the areas requiring improvements, especially safety and operability. Among the innovative options, a gas power conversion systems (PCS) is envisaged. In this latter innovative PCS, the working gas is nitrogen whose flow rate delivers power to a turbine driving with the same shaft two compressors (low and high pressure) separated by an intercooler. The other part of the work delivered by the gas is used to drive the alternator that produces electricity. The main objective of such a PCS consists in avoiding physically the possibility of a sodium/water reaction with the secondary circuit but the impact of this PCS on the control of the accidents has also been studied. The main purpose of the studies presented in the paper is to assess the dynamic behavior of ASTRID including a gas PCS with the CATHARE2 code. The first transient presented deals with a loss of off-site power and has been calculated for the gas PCS but also for a classical steam/water PCS for comparison purpose. Then typical transients of gas system have been investigated. Several families of initiating events affecting the PCS are studied: breaches in the ternary circuit, a loss of power supply, a loss of main heat sink and the spurious

Loss of off-site power transient analysis for a sodium-cooled fast reactor equipped with a gas power conversion system and preliminary optimisation of its operation

“…The Initiating Event (IE) induces a loss of the pumps associated to the RRA and RRC systems, which can not be employed (Tenchine, 2010); -The alternative procedure, proposed in this paper, substitutes the RRB system by the gas PCS in case of a LOOP. This strategy has preliminary been investigated (Bertrand et al, 2016b). First, it was demonstrated that even if the TM rotation speed decreases to zero (normal behaviour for a LOOP accident), the recuperator HX allows the PCS to conserve a low natural circulation of gas which slows the heating up of the core.…”

Transient compressible simulation of a high-speed radial compressor using the CATHARE system code

“…In some SFR concepts with Brayton cycles as power conversion systems, compressors determine the global cycle efficiency and their transient modeling is therefore essential (see Refs. Bertrand et al, 2016;Mauger et al, 2019). Finally, more and more safety or power generation concepts involve supercritical CO2 cycles.…”