1. An exit stay apparatus for installation into a reaction hydraulic turbine, which has runner apparatus with runner blades secured to the runner crown, trun- cated at the bottom, and the draft tube cone, comprising an exit stay crown, an intermediate exit flange formed by two surfaces of revolution, a plurality of crown exit stay vanes secured to said exit stay crown and to crown side of said intermediate exit flange, a plurality of peripheral exit stay values secured to peripheral side of said intermediate exit flange; and when installed into said reaction hydraulic turbine; said exit stay crown is located immediately under said runner crown, which said exit stay crown together with said runner crown forms water passages at said runner apparatus exit; said crown exit stay vanes cross water passages from said exit stay crown to said crown side of said intermediate exit flange and said peripheral exit stay vanes cross water passages from said peripheral side of said intermediate exit flange to the periphery, so that the entire flow of the water through said reaction hydraulic turbine must pass through the channels formed by said crown exit stay vanes, said intermediate exit flange, and said peripheral exit stay vanes, said peripheral exit stay vanes are secured at the periphery and, therefore, said intermediate exit flange, said crown exit stay vanes, and said exit stay crown are supported by said peripheral exit stay vanes below said runner crown; said exit stay crown does not touch other parts of said reaction hydraulic turbine besides said crown exit stay vanes.

2. An exit stay apparatus in claim 1 wherein the meridional cross-section of said intermediate exit flange has a shape or non-symmetric profile when rounded inlet and sharp exit.

3. An exit stay apparatus in claim 2 wherein said peripheral side of said inter- mediate exit flange is formed, excluding the inlet part, by a stream surface of the flow leaving the runner at optimum operating regime in the turbine when said exit stay apparatus is not installed

4. An exit stay apparatus in claim 1 for installation into said reaction hydraulic turbine with runner apparatus having an intermediate flange with truncated exit, which said intermediate exit flange does not touch said intermediate flange of said runner apparatus and said crown and peripheral sides of said intermediate exit flange are continuations of crown peripheral sides of said intermediate flange of said runner apparatus.

5. An exit stay apparatus in claim 1 wherein said crown exit stay vanes are identical in shape, are evenly distributed around said exit stay crown, and the solidity of the cascades formed by profiles of said exit stay vanes (L/T)or, where L is the length of said exit vane profile and T is the maximum distance between adjacent profiles along circumference, has its value larger than 2Ø

6. An exit stay apparatus in claim 1 wherein said peripheral exit stay vanes are identical in shape, are evenly distributed around said exit intermediate exit flange, and the solidity of the cascades formed by profiles of said peripheral exit stay vanes (L/T)per, changes its value from high value between 0.9 and 1.0 at said intermediate exit flange peripheral side to small value, between 0.1 and 0.2, at the apparatus periphery.

7. An exit stay apparatus in claim 1 wherein said exit stay apparatus has an exit stay flange at the apparatus periphery secured to said draft tube cone with said peripheral exit stay vanes secured to said stay flange.