Chapter 06: Generation III Advanced Nuclear Power Reactors – Part 1

According to the World Nuclear Association, as of February 2020:

  • Improved designs of nuclear power reactors are constantly being developed internationally.
  • The first so-called Generation III advanced reactors have been operating in Japan since 1996. These have now evolved further.
  • Newer advanced reactors now being built have simpler designs which are intended to reduce capital cost. They are more fuel efficient and are inherently safer.
  • Many new designs are small – up to 300 MWe. These are described in a separate information paper.

The nuclear power industry has been developing and improving reactor technology for more than five decades and is starting to build the next generation of nuclear power reactors to fill new orders. Several generations of reactors are commonly distinguished:

Several generations of reactors are commonly distinguished:

  • Generation I reactors were developed in 1950-60s, and the last one shut down in the UK in 2015;
  • Generation II reactors are typified by the present US and French fleets and most in operation elsewhere;
  • So-called Generation III (and III+) are the advanced reactors discussed in this paper, though the distinction from Generation II is arbitrary. The first ones are in operation in Japan and others are under construction in several countries; and
  • Generation IV designs are still on the drawing board and will not be operational before the 2020s.


A generation III reactor is a development of any of the generation II nuclear reactor designs incorporating evolutionary improvements in design developed during the lifetime of the generation II reactor designs. These reactors include improved fuel technology, superior thermal efficiency, passive safety systems, and standardized design for reduced maintenance and capital costs.

Third-generation reactors represent the following characteristics:

  1. A standardized design for each type to expedite licensing, reduce capital cost and reduce construction time;
  2. A simpler and more rugged design, making them easier to operate and less vulnerable to operational upsets;
  3. Higher availability and longer operating life—typically 60 years;
  4. Reduced possibility of core melt accidents;
  5. Resistance to serious damage that would allow radiological release from an aircraft impact;
  6. Higher burn-up to reduce fuel use and the amount of waste; and
  7. Burnable absorbers (“poisons”) to extend fuel life.

The US Nuclear Regulatory Commission (NRC) believes third-generation reactor designers should consider the following:

  1. Highly reliable, less complex safe shutdown systems, particularly ones with inherent or passive safety features;
  2. Simplified safety systems that allow more straightforward engineering analysis, operate with fewer operator actions and increase operator comprehension of reactor conditions;
  3. Concurrent resolution of safety and security requirements, resulting in an overall security system that requires fewer human actions;
  4. Features that prevent a simultaneous breach of containment and loss of core cooling from an aircraft impact, or that inherently delay any radiological release, and;
  5. Features that maintain spent fuel pool integrity following an aircraft impact.

The other major differences between conventional and advanced nuclear power reactors include:

  1. Many third-generation reactors incorporate passive or inherent safety features that require no active controls or operational intervention to avoid accidents in the event of malfunction, and may rely on gravity, natural convection or resistance to high temperatures. Traditional reactor safety systems are, “active” in the sense that they involve electrical or mechanical operation on command. Some engineered systems operate passively, e.g. pressure relief valves. They function without operator control and despite any loss of auxiliary power. Both require parallel redundant systems. Inherent or full passive safety depends only on physical phenomena such as convection, gravity or resistance to high temperatures, not on functioning of engineered components;
  2. Some third-generation reactors will be designed for load following. While most French reactors today are, operated in that mode to some extent, the European Pressurized Reactors (EPR) design has better capabilities. It will be able to maintain its output at 25 percent and then ramp up to full output at a rate of 2.5 percent of rated power per minute up to 60 percent output and at 5 percent of rated output per minute up to full rated power. This means that potentially the unit can change its output from 25 percent to 100 percent in less than 30 minutes, though this may be at some expense of wear and tear; and
  3. Many of third-generation reactors are larger than, predecessors. Increasingly they involve international collaboration.

However, certification of designs is on a national basis, and is safety-based. In Europe, there are moves towards harmonized requirements for licensing. In Europe, reactors may also be, certified according to compliance with European Utilities Requirements (EUR) of 12 generating companies, which have stringent safety criteria. The EUR are, basically, a utilities’ wish list of some 5000 items needed for new nuclear plants. Plants certified as complying with EUR include Westinghouse AP1000, Gidropress’ AES-92, Areva’s EPR, GE’s ABWR, Areva’s SWR-1000, and Westinghouse BWR 90.

Here is a table, which illustrates the configuration of Generation III Advanced Nuclear Power Reactors:

1.1European   Pressurized Water Reactor (EPR);
1.2Advanced   Passive 1000 (AP1000);
1.3Advanced   Boiling Water Reactors (ABWR);
1.4Economic   & Simplified Boiling Water Reactors (ESBWR);
1.5Advanced   Pressurized Water Reactors (APWR);
1.6Advanced   Pressurized Reactors 1400 (APR1400);
1.12International   Reactor Innovation and Secure (IRIS);
1.13VBER-300;   and
2.1Enhanced   CANDU-6(EC6);
2.2Advanced   CANDU Reactors (ACR);
2.3Advanced   Heavy Water Reactors (AHWR);
3.2Pebble   Bed Modular Reactors (PBMR); and
3.3Gas   Turbine – Modular Helium Reactors (G7-MHR).
4.1Fast   Breeder Reactors (FBR);
4.2Japan   Standard Fast Reactors (JSFR);
4.6European   Lead-Cooled System (ELSY);

This chapter will cover only Light Water Reactors (LWR):


The light water reactor or LWR is, defined as a type of thermal reactor that uses light water as a coolant and neutron moderator as opposed to heavy water as a coolant/moderator. Thermal reactors are the most common type of nuclear reactors, and light water reactors are the most common type of thermal reactor. There are the following three types of LWR:

  1. The Pressurized Water Reactor (PWR);
  2. The Boiling Water Reactor (BWR); and
  3. The Supercritical Water Reactor (SWR).

Here is a brief description for each nuclear reactor under this category and these descriptions are, derived from the World Nuclear Association:

Areva NP has developed a large (4590 MWt, typically 1750 MWe gross and 1630 MWe net) European pressurized water reactor (EPR)), which was confirmed in mid-1995 as the new standard design for France and received French design approval in 2004. It is a 4-loop design derived from the German Konvoi types with features from the French N4, and is, expected to provide power about 10 percent cheaper than the N4. It will operate flexibly to follow loads, have fuel burn-up of 65 GWd/t and a high thermal efficiency, of 37 percent, and net efficiency of 36 percent. It is capable of using a full core load of MOX. Availability is, expected to be 92 percent over a 60-year service life. It has four separate, redundant safety systems rather than passive safety.

The first EPR unit is, being built at Olkiluoto in Finland, the second at Flamanville in France, the third European one will be at Penly in France, and two further units are under construction at Taishan in China. A US version, the US-EPR, was, submitted for US design certification in December 2007, and this is, expected to be granted early 2012. The first unit (with 80 percent US content) is, expected to be grid connected by 2020. It is, now known as the Evolutionary PWR (EPR). Much of the one million person-hours, of work involved in developing this US EPR are making the necessary changes to output electricity at 60 Hz instead of the original design’s 50 Hz. The main development of the type is to be through UniStar Nuclear Energy, but other US proposals also involve it.

1.2     Advanced Passive 1000 (AP1000):

The AP1000, based on the proven performance of Westinghouse-designed PWR, is an advanced 1154 MWe nuclear power plant that uses the forces of nature and simplicity of design to enhance plant safety and operations and reduce construction costs. The AP1000 features proven technology, innovative passive safety systems and offers:

  • Unequaled safety;
  • Economic competitiveness; and
  • Improved and more efficient operations.

The AP1000 builds and improves upon the established technology of major components used in current Westinghouse-designed plants with proven, reliable operating experience over the past 50 years. These components include:

  1. Steam generators;
  2. Digital instrumentation and controls;
  3. Fuel;
  4. Pressurizer; and
  5. Reactor vessels.

The Westinghouse AP1000 is a 2-loop PWR that has evolved from the smaller AP600, one of the first Generation III reactor designs certified by the US NRC, in 2005. Simplification was a major design objective of the AP1000, in overall safety systems, normal operating systems, the control room, construction techniques, and instrumentation and control systems provide cost savings with improved safety margins. Core damage frequency is 5×10-7. It is being, built in China, and the Vogtle site is being, prepared for initial units in the USA.

The first four units are on schedule, being, assembled from modules. It is quoted as 1200 MWe gross and 1117 MWe net (3400 MWt), though 1250 MWe gross in China. Westinghouse earlier claimed a 36-month, construction time to fuel loading, but the first ones being built in China are on a 51-month timeline to fuel loading, or 57-month schedule to grid connection.

1.3     Advanced Boiling Water Reactors (ABWR):

The advanced boiling water reactor (ABWR) is, derived from a General Electric design. Two examples built by Hitachi and two by Toshiba are in commercial operation in Japan (1315 MWe net, but two down-rated to 1108 and 1212 MWe net), with another two under construction there and two in Taiwan. Four more are, planned in Japan and another two in the USA. It is basically a 1380 MWe (gross) unit (3926 MWt in Toshiba version), though GE Hitachi quote 1350-1600 MWe net and Hitachi is also developing 600, 900 and 1700 MWe versions of it. Toshiba outlines development from 1350 MWe class of 1600-1700 MWe class as well as 800-1000 MWe class derivatives. Tepco is funding the design of a next generation BWR, and the ABWR-II is, quoted as 1717 MWe.

The first four ABWR, were each built in 39 months on a single-shift basis. Though GE and Hitachi have subsequently joined up, Toshiba retains some rights over the design, as does Tepco. Both GE-Hitachi and Toshiba (with NRG Energy in USA) are marketing the design. Design life is 60 years.

The following highlights Technology Enhancements that Improve Performance:

  1. Reactor internal pumps –improved safety and performance by eliminating external recirculation systems;
  2. Integrated containment and reactor building–improved seismic response, compact, and easier to construct;
  3. Compact reactor building–less construction material and shorter construction times;
  4. Optimized modularization–module designs refined and proven in real installations;
  5. Sophisticated control systems–fully digital, providing reliable and accurate plant monitoring, control, and diagnostics; and
  6. High integrity fuel, improved water chemistry, and radiation source elimination–reduced radwaste and occupational exposure.

Benefits and Features of the ABWR over Previous BWR Designs include:

  1. Improved safety, reliability, operability, and maintainability;
  2. Demonstrated reduction in capital and O & M costs;
  3. Proven advanced reactor technology and performance enhancements; and
  4. Shorter construction time of approximately 39 months from first concrete to first fuel load proven in Japan.

1.4     Economic and Simplified Boiling Water Reactors (ESBWR):

GE Hitachi Nuclear Energy’s ESBWR is a Generation III+ technology that utilizes passive safety features and natural circulation principles and is essentially an evolution from a predecessor design, the SBWR at 670 MWe.

GE says it is safer and more efficient than earlier models, with 25 percent fewer pumps, valves and motors. The ESBWR will produce approximately 1600 MWe gross, 1520 MWe net, depending on site conditions, and has a design life of 60 years. It was more fully known as the Economic & Simplified BWR (ESBWR) and leverages proven technologies from the ABWR. The ESBWR is in advanced stages of licensing review with the US NRC for GE Hitachi and is on schedule for full design certification in 2010-11. Core damage frequency is, quoted as 1×10-8.




  1. World Nuclear Association: Advanced Nuclear Power Reactors;
  2. Advanced Nuclear Energy Systems;
  3. GE Hitachi Nuclear Energy;
  4. Wikipedia:      Economic Simplified Boiling Water Reactor;
  5. ATMEA:      The ATMEA1 Reactor;
  6. Multiphase Flow Dynamics      4 – Review;
  7. AES-92 for Belene;
  8. MIR-1200;
  9. Wikipedia: International Reactor Innovative and Secure;
  10. Wikipedia: Heavy Water      Reactors.

This chapter was published on “Inuitech – Intuitech Technologies for Sustainability” on April 8, 2011; and

This chapter was updated on 9 June 2020.

Chapter 06 – Part 2 …