Experimental Design Bureau of Machine Building (OKBM),
Russian Federation

VII — 1. DESCRIPTION OF THE GT-MHR CONCEPT

An international project for the GT-MHR was launched in 1995 by the Russian Ministry for Atomic Energy and the General Atomics Company of the USA. Later, the project was joined by the Framatome[53] (France) and Fuji Electric (Japan). At present, the preliminary design is completed, and the technology demonstration phase is underway. The goal of technology demonstration is experimental validation of key design solutions, mainly for fuel, for turbomachine, for structural materials, vessels, and for computer codes. A detailed description of the GT-MHR concept is presented in [VII-1].

The GT-MHR is a high temperature gas cooled reactor based on the following state of the art technologies:

— Technologies of modular helium cooled reactors using inherently safe micro fuel with several layers of

ceramic coating;

— Highly efficient gas turbines designed for aviation and power applications;

— Electromagnetic bearings;

— Effective compact plate heat exchangers.

The helium cooled modular GT-MHR, capable of generating high temperature heat, is coupled with a gas turbomachine consisting of a turbine, an electric generator, and compressors, and implements the direct Brayton gas-turbine cycle for electricity generation (see Fig. VII-1).

Figure VII-2 shows a flow diagram of the cooling system of the GT-MHR reactor plant. Main characteristics of the reactor plant are given in Table VII-1.

The reactor, the power conversion unit (PCU), and all associated primary circuit systems are located in an underground silo of the reactor building (see Fig. VII-3).

The reactor includes an annular core consisting of 1020 hexahedral fuel assemblies similar to those of the Fort Saint Vrain reactor. The core is surrounded by a graphite reflector. The lower part of the reactor vessel houses the shutdown cooling system (SCS).

The reactor vessel is surrounded by the surface cooler of the passive reactor cavity cooling system (RCCS). The RCCS removes heat from the reactor vessel in all accidents, including complete loss of coolant (LOCA).

The power conversion system is arranged in the PCU vessel and includes a turbomachine, a recuperator, and water cooled pre-cooler and intercooler. The single shaft turbomachine consists of a generator, a gas turbine, and two compressor sections with fully electromagnetic suspension systems.

Reactor design characteristics and the direct closed gas-turbine power conversion cycle are major advantages of the GT-MHR nuclear power plant (NPP) compared to other plants with steam cycles, because they allow for simplification and reduce the number of required equipment items and systems (including safety systems), by completely eliminating a steam turbine power circuit from the plant.

The GT-MHR can achieve a high safety standard through inherent safety features of the plant and via the use of passive safety systems that rule out the possibility of a reactor core meltdown in any accident, including LOCA.

1 — Generator; 2 — Recuperator; 3 — Turbocompressor; 4 — Intercooler;

5 — Precooler; 6 — Control and protection assembly; 7 — Reactor core; 8 — Vessel system;
9 — Reactor shutdown cooling system

FIG. VII-1. Reactor plant.