Transition to steel 10ГН2МФА during RCP set production.
The materials used to manufacture the RCP set and its auxiliary systems shall be chosen according to the requirements of the regulatory documents valid in the RF and the requirements of the foreign Customers' documents when making the orders for the foreign Customers.
The Supplier of RCP set is responsible for a choice of the materials and shall choose the materials meeting the process requirements, the requirements for fabrication.
If the material is produced according to the technical conditions not approved and certified by the world-wide recognized norms, the Manufacturer of the material is to give his justifications. The justification shall be based on the risk analysis and be the proving evidence that the chosen materials have the same safety level as the materials authorized.
The applied materials shall withstand the corrosion and erosion effect caused by the coolant or external effects and decontaminating solutions.
The material of the components made of stainless chromium-nickel austenitic steels shall be intercrystalline corrosion resistant.
The physical and mechanical properties of materials shall assure the required service life of 60 years.
The need for transition has arisen because of the problem of weldability of RCP set vessel steel 06Х12Н3ДЛ with the welded forged reducers of steel 10ГН2МФА in the suction and pressure nozzles (welding is performed by electrodes ЦЛ-51).
For the base metal of RCP set vessel and especially of welded joints performed by electrode ЦЛ-51 the contract requirements for materials properties, and also the RD requirements for LBB concept application are not satisfied.
The calculated assessment of LBB concept applicability for MCP-to-RCP set welded joint (electrode ЦЛ-51) at the various levels of the possible seismic SSE loads for "Hanhikivi" NPP RP showed that the required margins for this weld are not satisfied and there is a large risk to obtain the negative results when justifying the LBB concept for "Hanhikivi" NPP.
The RCP set components shall be made of steel 10ГН2МФА with anti-corrosive cladding on the internal surface.
The chemical composition and mechanical properties shall be determined for the base metal and weld metal of the RCP set hydraulic casing in accordance with the requirements of the regulatory documents. In addition (on the Customer's request), the brittle fracture characteristics shall be determined:
- ductile-to-brittle transition temperature in the initial state of the RCP set material and welded joint metal;
- upper shelf energy;
- temperature Т₀.
The full report isn't submitted..