Steam generator for BN-800 reactor NPP

Its structure is based on section-modular concept, which allows to keep SG in operation even in case of heat-exchanging surface depressurization of one of the modules of any section.

The SG consists of 10 sections, each having one straight-tube module of evaporator and superheater, binding pipelines with necessary valves. The BN-800 SG is a further upgrading of the BN-600 plant SG, which has been successfully operated in power mode since April 1980.

SG is intended for generation of superheated steam as a part of power unit of a three-loop BN-800 plant with fast neutron reactor and sodium coolant in the primary and secondary circuits.

SG structure and fastening provide:

• normal continuous operation under OBE of magnitude 6 according to MSK 64 scale;
• normal operation of the secondary side under SSE of magnitude 7 according to MSK 64 scale, plant cooldown under all modes except for the cases of loss of feedwater supply in modes “water-stop”, “loss of power”;
• keeping SG in operation under the condition of “small leak” of water into sodium by quick automatic disconnection of the section containing the failed module;
• protection of the secondary equipment against overpressure under the condition of “large leak” and bringing SG out of operation with discharge of products of water-sodium interaction into the emergency protection system tanks;
• integrity of module body, secondary equipment and pipelines under pressure increase in them in case of instantaneous guillotine break of one heat-exchanging tube. 

SG structure provides:

• easy access for examination, repair and replacement of the internals on the third side;
• replacement of the failed module with a new one;
• performance of non-destructive test of binding pipeline connections and pipe-to-module welds;
• withdrawal of heat exchanging tubes for laboratory studies.
   

Specifications: