Supercritical water-cooled reactor thermal efficiency

The supercritical-water-cooled reactor (SCWR) ( Fig. 58.21) system features two fuel cycle options the first is an open cycle with a thermal neutron spectrum reactor the second is a closed cycle with a fast-neutron spectmm reactor and full actinide recycle. Both options use a high-temperature, high-pressure, water-cooled reactor that operates above the thermodynamic critical point of water (22.1 MPa, 374°C) to achieve a thermal efficiency approaching 44%. The fuel cycle for the thermal option is a once-through uranium cycle. The fast-spectrum option uses central fuel cycle facilities based on advanced aqueous processing for actinide recycle. The fast-spectrum option depends upon the materials R D success to support a fast-spectrum reactor. 

Concepts of nuclear reactors cooled with water at supercritical pressures were studied as early as the 1950s and 1960s in the US and Russia. After a 30-year break, the idea of developing nuclear reactors cooled with supercritical water (SCW) became attractive again as the ultimate development path for water cooling. This statement is based on the known history of the thermal power industry, which made a revolutionary step forward from the level of subcritical pressures (15—16 MPa) to the level of supercritical pressures (23.5—35 MPa) more than 50 years ago with the same major objective as that of supercritical water-cooled reactors (SCWRs) to increase thermal efficiency of power plants. The main objectives of using SCW in nuclear reactors are (1) to increase the thermal efficiency of modem nuclear power plants (NPPs) from 30—35% to about 45—50% and (2) to decrease capital and operational costs and, hence decrease electrical energy costs. 

In general, the major driving force for all advances in thermal power plants and NPPs is thermal efficiency and generating costs. Ranges of gross thermal efficiencies of modem power plants are (1) combined-cycle thermal power plants (up to 62%) (2) supercritical-pressure coal-fired thermal power plants (up to 55%) (3) C02-cooled reactor NPPs (up to 42%) (4) sodium-cooled fast reactor NPPs (up to 40%) (5) subcritical-ptessure coal-fired thermal power plants (up to 40%) and (6) modem water-cooled reactors (30—36%). 

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