NOVELTY - The system (90) has a turbo pump placed in a working fluid circuit (102). An attemperation line (160) is coupled to the working fluid circuit upstream of heat exchangers (120, 130) and downstream of one of the heat exchangers. A power turbine bypass line (119) is coupled to the working fluid circuit upstream of a power turbine (128) and downstream of the power turbine, and circumvents working fluid around the power turbine. An inventory system (180) is coupled to the fluid circuit by an inventory system line (186), and comprises an inventory tank (181) and refrigeration systems (182, 183).    USE - Heat engine system for encompassing elements of a thermodynamic cycle e.g. rankine cycle and derivative of a rankine cycle, for generating electrical energy from solar or geothermal sources for industrial applications. Uses include but are not limited to thermal engine, power generation device, heat or waste heat recovery system and heat-to-electricity system.    ADVANTAGE - The system manages a volume of the working fluid during a system shutdown, so that temperature and pressure can be regulated to avoid venting of the working fluid and avoid damage to components of the system. The system allows a heat sink to absorb a portion of the thermal energy from the working fluid in the inventory tank, thus reducing and maintaining the pressure within the inventory tank below maximum allowable working pressure (MAWP).    DETAILED DESCRIPTION - The inventory tank is a low-pressure storage tank. The turbo pump is a turbo-drive pump and a turbine-drive pump. The working fluid is lower boiling-point working fluid e.g. hydrocarbons such as light hydrocarbons e.g. propane and butane, and halogenated hydrocarbons such as hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) e.g. R245fa, and non-hydrocarbon working fluids such as ammonia. An INDEPENDENT CLAIM is also included for a method for managing working fluid in a heat engine system during an emergency shutdown.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic block diagram of a heat engine system.    Heat engine system (90)    Working fluid circuit (102)    Power turbine bypass line (119)    Heat exchangers (120, 130)    Power turbine (128)    Attemperation line (160)    Inventory system (180)    Inventory tank (181)    Refrigeration systems (182, 183)    Inventory system line (186)