Advanced Reactor Designs

In the United States and elsewhere, new reactors are being designed. For the most part, the successful designs are improvements on the current PWR and BWR designs.  Other design improvements include development of passive technologies which do not require components to start and run. Other designs include the Pebble Bed Modular reactor and improvements on prior gas cooled reactor designs. The latter designs appear to be progressing at a slower rate.
A.     Approved Designs
The US Nuclear Regulatory Commission (NRC) has certified 3 reactor designs (approval date in parenthesis):
The AP1000 is a larger version of Westinghouse’s approved AP600 design. The1000 MWe advanced pressurized water reactor incorporates passive safety systems, simplified system designs, a longer reactor vessel, longer fuel, larger steam generators, and a larger pressurizer than the AP600. The passive systems use natural driving forces without active pumps, diesels, and other support systems after actuation. Use of redundant, non-safety-related, active equipment and systems minimizes unnecessary use of safety-related systems.
Related References:
AP1000 Design Certification Documents, Revision 14
Current PWR Design

B.     Designs Under Consideration

The following additional designs are being evaluated.

General Electric ESBWR
The Economic and Simplified Boiling Water Reactor (ESBWR) is a 1,390 MWe, natural circulation boiling water reactor that incorporates passive safety features. This design is based on the 670 MWe  predecessor, Simplified BWR (SBWR), and the certified Advanced Boiling Water Reactor (ABWR). Natural circulation is enhanced by using a taller vessel, shorter core, and less flow restrictions. The design uses an isolation condenser system for high pressure inventory control and decay heat removal during isolated conditions. After initiation of the automatic depressurization system, low pressure inventory control is provided by the gravity driven cooling system. Containment cooling is provided by the Passive Containment Cooling System.
Related References:
GE Application for Final Design Approval and Design Certification of ESBWR Standard Plant Design
Current BWR Design
Atomic Energy of Canada Limited (AECL) ACR-700
The Advanced CANDU Reactor 700 (ACR-700) is an evolutionary 700-MWe design adapted from the current CANDU technology. The ACR-700 uses a conventional CANDU light water reactor cooling system with two steam generators and four heat transport pumps. The design uses slightly enriched uranium fuel, separate heavy water moderator and light water coolant, computer-controlled operation, and on-power refueling. The reactor has horizontal pressure tubes supported in a tank filled with the low pressure, low temperature heavy water moderator. The tank also supports the reactivity regulating and safety devices, which are located between the pressure tubes.
Related References:
ACR-700 Technical Description
Current CANDU Design
Framatome ANP European Passive Reactor (EPR)
The EPR is a large pressurized water reactor with design output of approximately 1600 MWe. Design features include four 100% capacity trains of engineered safety features, a double-walled containment, and a “core catcher” for containment and cooling of core materials for severe accidents resulting in reactor vessel failure. The design does not rely on passive safety features. The first EPR is currently being constructed at the Olkiluoto site in Finland. Framatome also hopes to build EPR’s at the Flammanville site in France, and has submitted a bid for EPR construction in China.
Related References:
Framatome EPR Reactor
IRIS (International Reactor Innovative and Secure) is a 335 MWe, 1000 MWt pressurized light water reactor being developed by an international consortium consisting of twenty-one organizations from ten countries led by Westinghouse. This project has been under development for three years with deployment expected in the 2012 to 2015 timeframe. The IRIS integral reactor vessel design houses not only the nuclear fuel and control rods, but also all the major reactor coolant system components including pumps, steam generators, pressurizer and neutron reflector. The IRIS integral vessel is larger than a traditional PWR pressure vessel, but the size of the IRIS containment is a fraction of the size of corresponding loop reactors.
Related References:
Publicly Available Information on the IRIS Reactor
Pebble Bed Modular Reactor (PBMR)
ESKOM, the South African utility has proposed the PBMR, a modular High Temperature Gas Cooled Reactor (HTGR) that uses helium as its coolant. The design consists of eight reactor modules, each rated at 165 MWe. The plant design includes a capacity to store 10 years of spent fuel in the plant with additional storage capability in onsite concrete silos. The PBMR core is based on the German high-temperature gas-cooled reactor technology and uses spherical fuel elements.
Related References:
Pebble Bed Modular Reactor Company
Gas Turbine-Modular Helium Reactor (GT-MHR)
The GT-MHR power plant consists of two interconnected pressure vessels enclosed within a below-ground concrete containment structure. One vessel contains the reactor system and is based on the steam-cycle MHR which was developed as part of the U.S. Department of Energy's Modular High Temperature Gas-cooled Reactor program.

The second vessel contains the entire power conversion system. The turbo-machine consists of a generator, turbine and two compressor sections mounted on a single shaft rotating on magnetic bearings. The active magnetic bearings control shaft stability while eliminating the need for lubricants within the primary system. The vessel also contains three compact heat exchangers. The most important of these is a 95% effective recuperator, which recovers turbine exhaust heat and boosts plant efficiency to 48%.

Related References:
General Atomics GT-MHR Home Page
Current GCR Design


C.     Industry References

Nuclear Energy Institute

Nuclear Regulatory Commission

Energy Information Administration

International Atomic Energy Agency

Copyright © 1996-2006.  Joseph Gonyeau, P.E.. The Virtual Nuclear Tourist. All rights reserved. Revised: January 2, 2006.