International Reactor Innovative and Secure (IRIS) is a Generation IV reactor

Generation IV reactor

Generation IV reactors are a set of theoretical nuclear reactor designs currently being researched. Most of these designs are generally not expected to be available for commercial construction before 2030...

 design made by an international team of companies, laboratories, and universities and coordinated by Westinghouse

Westinghouse Electric Company

Westinghouse Electric Company LLC is a nuclear power company, offering a wide range of nuclear products and services to utilities throughout the world, including nuclear fuel, service and maintenance, instrumentation and control and advanced nuclear plant designs...

. IRIS is hoped to open up new markets for nuclear power

Nuclear power

Nuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...

 and make a bridge from Generation III reactor

Generation III reactor

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...

 to Generation IV reactor

Generation IV reactor

Generation IV reactors are a set of theoretical nuclear reactor designs currently being researched. Most of these designs are generally not expected to be available for commercial construction before 2030...

 technology. The design is not yet specific to reactor power output. Notably, a 335 MW output has been proposed, but it could be tweaked to be as low as a 100 MW unit.

IRIS is a smaller-scale design for a Pressurized water reactor

Pressurized water reactor

Pressurized water reactors constitute a large majority of all western nuclear power plants and are one of three types of light water reactor , the other types being boiling water reactors and supercritical water reactors...

 (PWR) with an integral reactor coolant system layout, meaning the steam generators, pressurizer, control rod drive mechanisms, and reactor coolant pumps are all located within the reactor pressure vessel. This causes it to have a larger pressure vessel than an ordinary PWR despite a lower power rating, the size is more comparable to that of an ABWR

Advanced Boiling Water Reactor

The Advanced Boiling Water Reactor is a Generation III boiling water reactor. The ABWR is currently offered by GE Hitachi Nuclear Energy and Toshiba...

.

Many of these design goals coincide with the objectives of the GNEP

Global Nuclear Energy Partnership

The International Framework for Nuclear Energy Cooperation formerly the Global Nuclear Energy Partnership began as a U.S. proposal, announced by United States Secretary of Energy Samuel Bodman on February 6, 2006, to form an international partnership to promote the use of nuclear power and close...

 program launched by the Bush Administration. With large international acceptance, IRIS could be a very large part of GNEP, providing a plant type for user nations.

Contributors

The project has included the work of a number of organizations around the world, this is a list of the major contributors:

Contributor	Country	Contributions
Industry
Westinghouse Westinghouse Electric Company Westinghouse Electric Company LLC is a nuclear power company, offering a wide range of nuclear products and services to utilities throughout the world, including nuclear fuel, service and maintenance, instrumentation and control and advanced nuclear plant designs...	USA	Overall coordination; leading core design, safety analyses and licensing, commercialization
BNFL BNFL British Nuclear Fuels Limited was a nuclear energy and fuels company owned by the UK Government. It was a former manufacturer and transporter of nuclear fuel , ran reactors, generated and sold electricity, reprocessed and managed spent fuel , and decommissioned nuclear plants and other similar...	UK	Fuel cycle
Ansaldo Energia Ansaldo Energia Ansaldo Energia, a subsidiary of Finmeccanica, is an Italian power engineering company. It is based in Genoa.-History:The parent company, Ansaldo, started in 1853. It was taken over by Finmeccanica in 1993...	Italy Italy Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...	Steam generators Steam generator (nuclear power) Steam generators are heat exchangers used to convert water into steam from heat produced in a nuclear reactor core. They are used in pressurized water reactors between the primary and secondary coolant loops....  design
Ansaldo Camozzi	Italy Italy Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...	Steam generators Steam generator (nuclear power) Steam generators are heat exchangers used to convert water into steam from heat produced in a nuclear reactor core. They are used in pressurized water reactors between the primary and secondary coolant loops....  fabrication
ENSA	Spain Spain Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...	Pressure vessel Pressure vessel A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.The pressure differential is dangerous and many fatal accidents have occurred in the history of their development and operation. Consequently, their design,...  and internals
NUCLEP NUCLEP Nuclep is Nuclebrás Equipamentos Pesados SA, and Nuclebrás is Empresas Nucleares Brasileiras SA, part of Nuclep.Nuclep was founded in December 1975 to design and fabricate heavy components for nuclear power plants.-See also:...	Brazil Brazil Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...	Containment
OKBM	Russia Russia Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...	Testing, desalination and district heating co-gen
LABORATORIES
ORNL Oak Ridge National Laboratory Oak Ridge National Laboratory is a multiprogram science and technology national laboratory managed for the United States Department of Energy by UT-Battelle. ORNL is the DOE's largest science and energy laboratory. ORNL is located in Oak Ridge, Tennessee, near Knoxville...	USA	I&C, PRA, desalination, shielding, pressurizer
CNEN National Nuclear Energy Commission The National Nuclear Energy Commission is the Brazilian government agency responsible for the orientation, planning, supervision, and control of Brazil's nuclear program. The agency was created on 10 October 1956...	Brazil	Transient and safety analyses, pressurizer, desalination
ININ	Mexico	PRA, neutronics support
LEI	Lithuania	Safety analyses, PRA, district heating co-gen
ENEA	Italy	Testing, financial and manpower support
UNIVERSITIES
Politecnico di Milano	Italy	Safety analyses, shielding, thermal hydraulics, steam generators design, advanced control system
University of California, Berkeley University of California, Berkeley The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...	USA	Advanced cores, maintenance, security
Tokyo Institute of Technology	Japan	Advanced cores, PRA
University of Zagreb University of Zagreb The University of Zagreb is the biggest Croatian university and the oldest continuously operating university in the area covering Central Europe south of Vienna and all of Southeastern Europe...	Croatia	Neutronics, safety analyses
University of Pisa University of Pisa The University of Pisa , located in Pisa, Tuscany, is one of the oldest universities in Italy. It was formally founded on September 3, 1343 by an edict of Pope Clement VI, although there had been lectures on law in Pisa since the 11th century...	Italy	Containment analyses, severe accident analyses, neutronics
Polytechnic University of Turin Polytechnic University of Turin The Polytechnic University of Turin is an engineering university based in Turin, northern Italy. Established in 1859, Politecnico di Torino is Italy’s oldest Technical University. In 2011 it was ranked as the best engineering university in Italy in the Academic Ranking of World Universities.It is...	Italy	Source term
University of Rome University of Rome La Sapienza The Sapienza University of Rome, officially Sapienza – Università di Roma, formerly known as Università degli studi di Roma "La Sapienza", is a coeducational, autonomous state university in Rome, Italy...	Italy	Radwaste system
Georgia Institute of Technology Georgia Institute of Technology The Georgia Institute of Technology is a public research university in Atlanta, Georgia, in the United States...	Atlanta, Georgia Atlanta, Georgia Atlanta is the capital and most populous city in the U.S. state of Georgia. According to the 2010 census, Atlanta's population is 420,003. Atlanta is the cultural and economic center of the Atlanta metropolitan area, which is home to 5,268,860 people and is the ninth largest metropolitan area in...	Shielding, Fuel Design, and Reactivity Control
POWER PRODUCERS
Eletronuclear Eletronuclear Eletronuclear is a nuclear power company, which was established in 1997 in Brazil. It operates Angra Nuclear Power Plant. Eletronuclear is a wholly owned subsidiary of Eletrobrás....	Brazil	Developing country utility perspective

Reactor Coolant System

The coolant system consists of a pressurizer, Steam generator

Steam generator (nuclear power)

Steam generators are heat exchangers used to convert water into steam from heat produced in a nuclear reactor core. They are used in pressurized water reactors between the primary and secondary coolant loops....

s, and reactor coolant pumps (RCPs). These are all located within the reactor pressure vessel

Pressure vessel

A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.The pressure differential is dangerous and many fatal accidents have occurred in the history of their development and operation. Consequently, their design,...

, making a very small, short loop that forms the primary coolant system, see the figure on the right for the relative locations of the components.

Pressurizer

Unlike ordinary PWRs, the pressurizer is not contained in a separate vessel and connected to the primary side, but rather is the top of the pressure vessel itself. Water line will be at some preset value, and then sprays and boilers within the pressurizer can be used to control pressure and water level. The unique aspect of this is that the pressurizer is of much greater volume than current plants, which helps to keep the pressure constant in accident situations.

Steam Generator

Water from the secondary (the water that is turned into steam and used in the turbine) enters at the bottom of the steam generators, and goes up through a helical coil to the top. The steam generators are once through, and the pressure is greater on the secondary side tubes (no boiling takes place in the tubes). The secondary side water is allowed to flash at the end of the steam generator tube and go out through the steam pipe. There are eight steam generators, as well as eight steam pipes and feedwater pipes.

Reactor Coolant Pumps (RCP)

The decision to put the RCPs on the inside of the vessel was a fairly radical innovation. With the existence of eight separate RCPs as opposed to the 2 or 4 of a typical PWR, when one pump goes out, that pump can be shut down and isolated, not be worked on until the next outage.

Core

It has in the past been proposed to use higher enrichments for IRIS, allowing a longer cycle life, but the design now calls for 4.95% enriched Uranium

Uranium

Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...

, which is the same as what is being used in current plants. The fuel is designed for a 3 to 3.5 year life, and half of the core will reloaded in outages. This longer life is accomplished by having a very large core running a relatively low power plant.

Reactivity is controlled almost entirely by control rods and burnable poisons. This eliminates the need for Boron

Boron

Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...

 in the primary water, which is a plus for plant chemistry.

Containment

The containment of IRIS is spherical and set to be approximately 22–27 meters across. This is compared to 58 meters high and 40 meters in diameter for a typical 600 MW PWR. Additionally, two thirds of the containment will be underground, giving it a lower profile, in addition to its already very small footprint. While the containment will be smaller than typical plants, it will also be rated for a higher maximum pressure, increasing costs.

Advantages

Most of the advantages of the new IRIS design are safety related, although Westinghouse claims that IRIS will be able to deliver power at competitive rates as well.

Due to Economies of scale

Economies of scale

Economies of scale, in microeconomics, refers to the cost advantages that an enterprise obtains due to expansion. There are factors that cause a producer’s average cost per unit to fall as the scale of output is increased. "Economies of scale" is a long run concept and refers to reductions in unit...

, modern nuclear plants tend to be built with larger electrical outputs, such as the European Pressurized Reactor

European Pressurized Reactor

The EPR is a third generation pressurized water reactor design. It has been designed and developed mainly by Framatome , Electricité de France in France, and Siemens AG in Germany...

, which has scaled up power to 1600 MW in new plants. IRIS, on the other hand, is built to be used in countries where there are not extremely large electric power grids, mainly developing nations. Due to limitations on power of individual power stations versus total grid size, plants whose power is over a certain percentage of grid size are infeasible in such situations.

Due to simplifications and greater safety, it is believed by Westinghouse that in spite of its size, analysis estimated a target total cost of electricity at about 4 ¢/kWh. Given its small power and physical size, it is expected that multi-unit sites could be operated efficiently, Westinghouse estimates that a 3-unit site could be built in 9 years with a maximum cash outflow of 300 M$. One cost saver, for instance, is the need for only one control room, from which all units at a multi-unit site can be controlled.
Aside from economics, these are a few other advantages that the IRIS has:

• Fewer penetrations to the pressure vessel - by having the control rods and all drive mechanisms contained within the vessel, the need for dozens of small penetrations is eliminated, which are extremely costly. The only penetrations used are for the incoming and outgoing secondary coolant and for emergency safety systems.
• Large operating margins - the operating margins are typically the measure of a value compared to what that value would have to be to fail the fuel. IRIS effectively gets much lower operating margins by having a core with a much lower power density, while the core is mostly the same size as a current PWR, the thermal output is much smaller, making it much less likely to reach film boiling and fail in an accident.
• Lower radiation doses to workers - due to the confinement of all the RCS components and more shielding (by a larger water mass) result in low estimated doses for plant workers than current designs.
• Collaboration and research - incorporating so many universities and labs into the project is expected to have a number of benefits, one is contributing to the academic knowledge available for new plants, another is that researchers in many diverse countries with experience regarding the IRIS will be useful when they are deployed, because a goal of the project is to eventually build plants in countries that do not currently have nuclear plants.
• Lowered core damage frequency
  Core damage frequency
  Core damage frequency is a term used in probabilistic risk assessment that indicates the likelihood of an accident that would cause damage to a nuclear reactor core. Core damage accidents are considered serious because damage to the core may prevent control of the nuclear reaction, which can lead...
  
   (CDF) - as a result of all the individual innovations that improve safety and an in depth Probabilistic risk assessment
  Probabilistic risk assessment
  Probabilistic risk assessment is a systematic and comprehensive methodology to evaluate risks associated with a complex engineered technological entity ....
  
   study that refine the net safety risk, IRIS has the lowest CDF (which is a quantitative measure of the probability of a major core accident taking place) associated with any proposed plant of 10⁻⁸.
• Marketing and licensing - With the vastly improved safety, there should be a quick and easy licensing associated with the design, and it could occupy a large part of a growing market for small size nuclear power plants, which is also being targeted by other designs such as the Russian floating nuclear power station
  Russian floating nuclear power station
  Floating nuclear power stations are vessels projected by Rosatom that present self-contained, low-capacity, floating nuclear power plants...
  
  .

Disadvantages and Criticisms

Compared to Generation III reactor

Generation III reactor

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...

s, there are a lot more innovations that may require further investment and research. All the advantages of the reactor can't be proved until a plant is actually built.

Other criticisms are common for the entirety of the GNEP plan. These criticisms relate to the possible lack of demand for such a small power plant, and skepticism of the economics.