...inlet control valves but Alstom's have only 1 inlet control valve? What are the advantage of having 2 HP inlet control valves?

In certain self-regulating closed loop steam turbine systems, it may be desirable to divert some input to a sensor array of some sort, then feed the input back into the system without interruption.You could do this with one control valve of course by using a splitter, but you then lose the extra options of running without sensors or running only with steam that passes through them.From a common sense point of view it probably cost siemens only a few $ to install the extra valve, but it makes many other applications possible.For examples- a reserve inlet, nested turbine systems, various testing or proving regimens, sensor calibration (by devoting one inlet to a control sample of known properties) and suchlike.