The target of this repair was construction of a new high-pressure section of the turbine casing and the valve chamber. As the main drawback of the original concept it emerged the valve chamber that was inappropriately designed in light of construction and material selection, which led to cracks especially in the area diffusers. The original concept of the high-pressure casing and the chamber was a weldment from many parts. The selection of the valve chamber concept and design adaptations were selected with regard to the up-to-date trends and pieces of knowledge in the field of design, computations and service of steam turbines. The new design consists of the inlet chamber, whose semi-product is a casting. This is designed as a monoblock that is built into an opening in the upper half of the high-pressure casing and welded. Such solution fulfils the condition of symmetry of distribution of pressures and temperatures of both halves of the high-pressure casing. With regard to the inlet parameters of working medium, there are selected special materials on the basis of stainless steels that fulfil the condition of operation at high temperatures and pressures.