South Korean APR 1400 Reactor Plant Surprises UAE Officials
- By Duncan Williams -
Officials in the United Arab Emirates (UAE) are currently analyzing bids for a $40 billion contract to build and operate the country’s first nuclear reactor. Although the bidders include well-established leaders in the nuclear industry, a Wall Street Journal article published on November 16, 2009, titled “Korea Gains as Nuclear-Plant Bidder,” indicates that a bid submitted by a South Korean consortium is much more competitive than anyone first thought. The UAE also accepted bids from a French consortium, including Areva, Gaz de France (GdF), Suez SA, Electricité de France and Total SA, as well as a US-Japanese consortium, including General Electric Co. and Hitachi Ltd.
The South Korean consortium is led by Korea Electric Power Corp., which includes the construction units of Samsung and Hitachi, and Westinghouse, a unit of Japan’s Toshiba Corp. Korea Electric Power Co. works in conjunction with several other Korean entities, including Korea Nuclear Fuel Co., Ltd., Korea Hydro & Nuclear Power Co., Ltd., Korea Plant Service & Engineering Co., Ltd., and Korea Power Engineering Co., Ltd.
According to the Wall Street Journal article, the Korean team submitted a bid for a reactor known as the Advanced Power Reactor (APR) 1400, which is a pressurized water reactor having a capacity of 1400 MW. There are currently no APR1400 plants in operation, but four of these plants are currently being built in the Republic of Korea and are scheduled to become operational in 2013-14.
The UAE officials were surprised that the APR1400 design rivals the submissions from the other consortiums. The French consortium submitted designs for the European Pressurized Reactor (EPR), and the US-Japanese consortium submitted designs for the Advanced Boiling Water Reactor (ABWR). All three plants are designed to operate for 60 years – twice as long as most conventional nuclear reactors in use today. Additionally, all three plant designs require refueling after approximately 18 months of operation. While the EPR will take 57 months to build, both ABWR and the APR1400 will only take 48 months to construct.
Surprisingly, the APR1400 includes safety features not found in conventional reactors. For example, the design includes a missile shield to defend against both an internal and external missile attack. The design even includes seismic restraints and improved materials that would prevent damage to the reactor in the event of an earthquake.
The basic design of the reactor vessel of the APR1400 is shown on Korea Hydro & Nuclear Power’s (KHNP’s) website. The reactor vessel contains the nuclear fuel which drives the fission process in the reactor. In order to remove heat produced by the fission process, water is pumped into the reactor vessel through 4 inlet nozzles, and exits through 2 outlet nozzles. The outlet nozzles are placed vertically higher than the inlet nozzles in order to promote natural circulation in the event of a loss of pumps.
The nuclear fuel for the APR1400 was designed by Korea Nuclear Fuel. The APR1400 uses uranium dioxide, processed from enriched uranium-235. To manufacture the nuclear fuel, the uranium dioxide must first be processed into a powder form. It is then pressed into cylindrical pellets of approximately 10mm in length, 8mm in width, and weighing 5.2 grams. Approximately 365 pellets are then stacked end-to-end inside a hollow fuel rod made of a zirconium-niobium alloy.
A spring is placed on one end of the tube to keep the pellets tightly packed and held in place. The tube is then pressurized with helium gas as both ends of the fuel rod are welded shut. The helium gas improves the transfer of heat from the fuel pellets to fuel rod. Helium is an inert gas, so it won’t react with the pellets as the reactor is operating.
The sealed fuel rods are then arranged into what is known as a PLUS7 fuel assembly. In order to produce one PLUS7 fuel assembly, hundreds of fuel rods are formed into a rectangular box arrangement and held in place by a series of spacer grids. These novel spacer grids are partly made of inconel, and include mixing vanes which - unlike conventional nuclear reactors - intentionally create a turbulent flow of water over the fuel rods. Turbulent flow is necessary in the APR1400 to prevent the water from boiling in the reactor vessel where the high-energy nuclear fuel is located.
Unlike the ABWR design submitted by the US-Japanese consortium, boiling in the reactor vessel of the APR1400 can cause severe safety concerns. Without a turbulent flow, the water would form a smooth stream across the exterior of the fuel rod and would absorb an excessive amount of heat. If the water begins to boil, bubbles would coalesce on the surface of the fuel rod, forming a thin film of air that prevents heat removal. As the heat builds up in the fuel rod, the metal would begin to melt resulting in the release of uranium, along with its fission products, into the water.
To prevent this, spacer grids are formed with mixing vanes which create a turbulent flow of water throughout the reactor vessel. [Mixing vane mid grid] Turbulent water flow reduces the amount of time a particle of water is adjacent to the fuel rod, thus preventing boiling and the subsequent formation of thin layers of film. As can be seen in the diagram, the spacer grids are square-shaped and can hold 16 x 16 fuel rods. Sensors are placed in the large central hole in the spacer grid, and support guides containing non-nuclear material are placed in the four remaining large cavities to provide structural support. Fuel rods are positioned in the smaller holes in the grid and are held in place by a combination of springs and dimples. This unique design allegedly reduces the wearing and scratching of the fuel rods. The spacer grids near the bottom and top of the PLUS7 fuel assembly also include filters which prevent particulates from entering or exiting the reactor vessel.
To get an idea of the power output by the APR1400, one uranium dioxide pellet produces about 1,600 KWh of electricity, which is the average amount of electricity that one household uses over an 8 month period. Each fuel rod contains 365 pellets, and one PLUS7 fuel assembly is made up of 236 fuel rods. This means that each fuel assembly contains about 86,140 uranium dioxide pellets. Since there are 241 fuel assemblies in each APR1400 reactor vessel, one APR1400 reactor can generate enough electricity to power roughly 13.3 million homes for one year.
The APR1400 also comes with a sleek control room, which places many of the reactor plant operators in one central location in order to improve communication. Many of the redundant operational backup systems found in conventional reactor plants have been eliminated. The computer consoles in the control room not only display overviews and instructions for upcoming procedures, but they also display links to any other cross-referenced procedures.
Another interesting feature of the APR1400 design is the in-containment refueling water storage tank (IRWST), which is kept in the same area as the reactor vessel. The purpose of the IRWST is to quickly fill the reactor in the event of a pipe rupture or any other casualty causing a loss of coolant. Instead of placing the IRWST in a separate area connected to the reactor vessel via piping and valves as in a conventional reactor, the IRWST in the APR1400 design surrounds the reactor like a moat in a doughnut shaped tank. The close proximity of the IRWST ensures that water will be continuously supplied to the reactor vessel to remove heat in the event of a loss of coolant casualty.
Of course, one of the biggest factors influencing the UAE officials is the cost of the reactor plants. Even though the price tag attached to each bid remains confidential, it is apparent that the Korean consortiums bid is extremely competitive. If the APR1400 is chosen, it would be the first time that Korea would export its nuclear technology to another country, solidifying its place as a key player in the global nuclear industry.
Last Week's Column:
Everything You Always Wanted To Know About MOX Fuels - By Duncan Williams - Last week a nuclear reactor in Genkai, Japan, became the first Japanese nuclear reactor to use a type of nuclear fuel known as mixed-oxide (MOX) fuel. Although uncommon in Japan and America, MOX fuel is currently used in at least 30 reactors throughout ...
About Duncan Williams
Duncan Williams graduated from the University of Florida in 1994 with a B.S. in Physics, and a minor in mathematics. Upon graduation, he was commissioned in the U.S. Navy where he completed training in the Navy’s Nuclear Propulsion program. He then served onboard an 
aircraft carrier, the USS Theodore Roosevelt, as a reactor control division officer. Onboard, he was responsible for the operation and maintenance of the electrical and mechanical components that make up the reactor control systems. This includes the control rod drive mechanisms, the reactor safety and emergency systems, the reactor coolant pump systems, and the ion exchangers. He also developed and implemented ship-wide reactor safety drills in order to educate sailors in reactor safety.
Duncan then transferred to the U.S. Naval Academy, where he served as a senior instructor teaching Thermodynamics to senior cadets. While serving as an instructor at the Naval Academy, Duncan attended night law school at the George Washington University Law School. After receiving his J.D. in 2004, he resigned his commission and began working as an intellectual property associate with Kenyon & Kenyon LLP. While at Kenyon & Kenyon, he drafted numerous patents relating to medical devices, electronic devices, telecommunications, as well as other technologies. He also has experience in all stages of patent litigation, and has represented numerous Fortune 500 companies in protecting their intellectual property rights. Duncan is currently an intellectual property associate at Blank Rome LLP.
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