The Supercritical-Water-Cooled Reactor (SCWR) system is a high-temperature, high-pressure water-cooled reactor that operates above the thermodynamic critical point of water (374 degrees Celsius, 22.1 MPa, or 705 degrees Fahrenheit, 3208 psia).

The supercritical water coolant enables a thermal efficiency about one-third higher than current light-water reactors, as well as simplification in the balance of plant. The balance of plant is considerably simplified because the coolant does not change phase in the reactor and is directly coupled to the energy conversion equipment. The reference system is 1,700 MWe with an operating pressure of 25 MPa, and a reactor outlet temperature of 510 degrees Celsius, possibly ranging up to 550 degrees Celsius. The fuel is uranium oxide. Passive safety features are incorporated similar to those of simplified boiling water reactors.

The SCWR system is primarily designed for efficient electricity production, with an option for actinide management based on two options in the core design: the SCWR may have a thermal or fast-spectrum reactor; the second is a closed cycle with a fast-spectrum reactor and full actinide recycle based on advanced aqueous processing at a central location.

This diagram illustrates a schematic concept of the reactor system and does not represent the reference design.

Advantages and challenges

As the system uses existing light water reactor technology, there is already extensive worldwide experience in constructing and operating this sort of reactor. Proposed designs are likely to enjoy high thermal efficiency and a simplified system configuration. A SCWR design could be developed with a fast neutron spectrum. Using fast neutrons with higher kinetic energies would enable the system to produce at least as much fissile material as it consumes (thereby fulfilling the sustainability goal as set out in the Generation IV roadmap). This concept’s tendency to have a positive void reactivity coefficient together with the potential for design basis loss-of-coolant accidents are likely to make this difficult to develop. The other major challenges for the SCWR are to develop a viable core design, accurately estimate the heat transfer coefficient and develop materials for the fuel and core structure that will be sufficiently corrosion-resistant to withstand SCWR conditions.

GIF progress in 2007

The SCWR system research plan was finalised in mid-2007. Project management boards have since been established in the following areas: thermal-hydraulics and safety; materials and chemistry; design and integration. Negotiations to put in place project plans for all of these areas have advanced significantly in the course of 2007.

Recent SCWR research papers and links

J. Yoo, Y. Ishiwatari, Y. Oka, J. Yang, J. Liu, Subchannel analysis of supercritical light water-cooled fast reactor assembly
Nuclear Engineering and Design, 237 (2007), 1096-1105.

M. Mori, W. Maschek and A. Rineiski, Heterogeneous cores for improved safety performance : A case study: The supercritical water fast reactor, Nuclear Engineering and Design,  Volume 236: 14-16  (2006), 1573-1579.

J. Yoo, Y. Ishiwatari, Y. Oka, J. Liu, Conceptual design of compact supercritical water-cooled fast reactor with thermal hydraulic coupling, Annals of Nuclear Energy, Volume 33 (2006), 945-956.

J. Yoo, Y. Ishiwatari, J. Liu, Composite Core Design of High Power Density Supercritical Water Cooled Fast Reactor, Paper No. 246, GLOBAL 2005, Tsukuba, Japan, 9-13 October 2005.

M. Mori, Core Design Analysis of the Supercritical Water Fast Reactor, Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft, Wissenschaftliche Berichte FZKA 7160 (2005).

M. Mori, Werner Maschek, Eckart Laurien, Koji Morita, Monte-Carlo/Simmer-III Reactivity Coefficients Calculations for the SuperCritical Water Fast Reactor, Paper No. 87753, GLOBAL 2003, New Orleans, Louisiana, 16-21 November 2003.

T. Mukohara, S. Koshizuka, Y. Oka, Core design of a high-temperature fast reactor cooled by supercritical light water, Annals of Nuclear Energy, 26 (1999) 1423-1436.

Y. Oka and S. Kozhizuka, Conceptual Design Study of Advanced Power Reactors, Progress in Nuclear Energy, 32 (1998), 163-177.

J.H. Lee, Y. Oka, S. Koshizuka, Safety System Consideration of Supercritical Water cooled Fast Reactor with Simplified PSA, Reliability Engineering and System Safety, 64 (1999), 327-338.

Y. Oka, S. Koshizuka, Y. Ishiwatari, A. Yamaji, Super light water reactors and Super fast reactors,
ISBN:978-1-4419-6034-4, 416 pages Springer 2010 2.

High Performance Light Water Reactor Phase 2

DOE Nuclear Energy Research Initiative SCWR Program Plan (pdf, 272 kb).

Contact: scwr@gen-4.org

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