Nuclear Fission Reactors: Boiling Water and Pressurized Water Reactors
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Nuclear Fission Reactors: Boiling Water and Pressurized Water Reactors DOUGLAS K. VOGT Lawrence Livermore National Laboratory Livermore, California, United States from hydrogen enriched in deuterium are called heavy 1. Electricity Production from Light Water Reactors water. light water reactor (LWR) Any reactor that is cooled and 2. Pressurized Water Reactors moderated by ordinary or light water. Both pressuri- 3. Boiling Water Reactors zed water and boiling water reactors are light water 4. Ship Propulsion reactors. pressurized water reactor (PWR) A reactor that operates at high pressure (typically 42000 psia). At this pressure, PWR coolant water does not experience significant Glossary boiling. Reactor coolant is heated by thermal energy from nuclear fission, resulting in a temperature increase. boiling water reactor (BWR) A light-water-cooled and - Heated coolant flows to a heat exchanger with lower B moderated reactor that operates at a pressure of 1000 pressure water (B1000 psia) on the ‘‘nonreactor side.’’ pounds per square inch at atmospheric pressure (psia). The lower pressure water is converted to steam. The At this pressure, reactor coolant is converted from steam from the steam generator flows to a conventional liquid water to steam by thermal energy from nuclear turbine-generator system, where it is converted to fission. The boiling occurs within the reactor core. electricity. Steam from the core of a BWR flows to a conventional turbine-generator system, where it is converted to electricity. decommissioning At the end-of-life stage of a nuclear power plant, the facility contains highly radioactive Scientists in the former Soviet Union and in the West components. As part of decommissioning, these com- ponents, including the reactor and other plant areas, are who developed nuclear weapons in World War II and decontaminated to reduce the amount of radioactivity. in the early days of the Cold War realized that the Some components will be removed from the reactor site tremendous energy produced by nuclear fission could and buried in an engineered disposal site. Pressurized be tapped either for direct use or for generating water, boiling water, and naval reactors are decommis- electricity. It was also clear that nuclear fission sioned. energy would allow development of compact, long- high-level radioactive waste repository An engineered lasting power sources that could have various facility that isolates spent fuel or the radioactive waste applications, including powering ships, especially from spent fuel reprocessing, safeguarding the environ- submarines. From their roots in naval nuclear power ment. programs, light water reactors have become an light water Hydrogen has two stable isotopes, (1) protium important source of electric power in many coun- (99.985% natural abundance), which has a nucleus consisting of one proton, and (2) deuterium (0.015% tries. Light water reactors built over the past 30 years natural abundance), which has a nucleus consisting of continue to generate electricity, and new reactor one proton and one neutron. Water molecules formed designs, the advanced boiling water reactor and the from water with natural abundance hydrogen (99.985% advanced pressurized water reactor, are planned for protium) are called light water. Water molecules formed operation in the 21st century. Encyclopedia of Energy, Volume 4. r 2004 Elsevier Inc. All rights reserved. 333 334 Nuclear Fission Reactors: Boiling Water and Pressurized Water Reactors 1. ELECTRICITY PRODUCTION Laboratory and General Electric Company were FROM LIGHT WATER REACTORS developing the boiling water reactor (BWR). A small prototype BWR, Vallecitos, generated electricity in The first nuclear reactor to produce electricity (albeit Pleasanton, California from 1957 to 1963. Dresden- a trivial amount) was the small experimental breeder 1, which was designed by General Electric, was the reactor (EBR-1) in Idaho, in the United States. EBR-1 first large commercial BWR (200 MWe). Dresden-1 started operating in December 1951. In 1953, was constructed 50 miles southwest of Chicago, President Eisenhower proposed his ‘‘Atoms for Illinois and operated from 1960 until 1978. Peace’’ program, setting the course for civilian In 1964, the first Soviet land-based PWR power nuclear energy development in the United States. reactor began power operations in Novovoronezh However, it was the U.S. effort under Admiral (Volga region). This reactor was a new 210-MWe Hyman Rickover that led to the development of the pressurized water reactor known as a VVER (an pressurized water reactor (PWR) for submarine use. acronym in Russian for veda-vodyanoi energetiches- As part of the PWR development, Westinghouse ky reaktor, meaning ‘‘water-cooled power reactor’’). Electric Corporation built a land-based submarine In the Murmansk region of the Arctic Northwest, a rector prototype at the National Reactor Testing slightly bigger VVER with a capacity of 440 MWe Station near Arco, Idaho. The prototype started was constructed at the Kola Nuclear Power Plant. operation in March 1953, and in 1954, the first This became a standard Russian PWR design. nuclear-powered submarine, the USS Nautilus, was By the end of the 1960s, electric utilities world- launched. In 1959, both the United States and the wide were placing orders for PWR and BWR units former Soviet Union launched their first nuclear- of 400 MWe to more than 1000 MWe. Other powered surface vessels. countries have built primarily PWR and BWR types, The success of the submarine prototype reactor so that today, 65% of the world nuclear electric led to the U.S. Atomic Energy Commission decision generating capacity is PWR and 23% is BWR. to build the 90-megawatt electric (MWe) output Overall, 16% of the world’s electricity now comes Shippingport demonstration PWR near Pittsburgh, from nuclear energy. Throughout the world, there Pennsylvania. Shippingport started operation in are 438 commercial nuclear generating units with 1957 and operated as a commercial nuclear power a total capacity of about 351,000 MWe. Worldwide, plant until 1982. In the United States, Westinghouse LWRs generated over 2,000,000,000 megawatt- Electric Corporation designed the first fully commer- hours (MWh) of electricity in 2001. Figure 1 shows cial 250-MWe PWR, Yankee Rowe, which started the location of nuclear power plants worldwide operation in 1960 and operated until 1992. As the that are under construction, in operation, or under- PWR was being developed, Argonne National going decommissioning. Figure 2 summarizes the Europe Russia 60°N North America Asia 45°N 30°N Africa 15°N East Asia West Asia 0° South America 15°S 30°S 45°S 120°W90°W60°W30°W0° 30°E 60°E 90°E 120°E 150°E FIGURE 1 Location of nuclear power plants worldwide. Map from the International Nuclear Safety Center (Argonne National Laboratory). Nuclear Fission Reactors: Boiling Water and Pressurized Water Reactors 335 United States WA France NH MT ME ND VT Japan MN OR Germany MA ID SD WI NY MI RI Russian Federation WY CT Ukraine PA NV NE IA NJ UT South Korea CO IN OH DE WV Sweden CA KS IL VA MD MO KY Spain NC AZ NM TN Belgium OK SC AR MS Bulgaria AL GA Taiwan TX LA Slovak Republic Switzerland FL Czech Republic Hungary Finland Years of Number of Average China commercial operation reactors capacity (MDC) India 0−9 2 1134 South Africa 10−19 47 1092 Mexico 20−29 55 779 Brazil United Kingdom FIGURE 3 Locations of operating light water reactors in the Pakistan United States as of December 2000 (there are no commercial Slovenia reactors in Alaska or Hawaii). MDC, Maximum dependable Netherlands capacity. This map and additional data are available on the Armenia Internet at the Web site of the U.S. Nuclear Regulatory 020406080 100 120 Commission (http://www.nrc.gov). Power plants FIGURE 2 Number of light water reactor nuclear power plants worldwide. Containment structure Steam line number of operating LWR nuclear power plants in Control rods Steam Reactor Generator each country. vessel generator To minimize dependence on fossil fuel imports, Pump Reactor several countries have placed significant dependence Turbine Cooling tower on nuclear energy from LWRs. The following Condensor Pump cooling countries generate more than 30% of electricity water output using LWRs: France, Belgium, Slovak Repub- lic, Ukraine, Sweden, Bulgaria, South Korea, Hun- FIGURE 4 Schematic view of a pressurized water reactor. gary, Slovenia, Switzerland, Armenia, Japan, Finland, and Germany. Eight countries have manu- active material from the reactor under accident factured large LWRs for electricity generation: the conditions; a steam-powered turbine-generator that United States, France, Japan, Germany, Russia, produces electricity; and a condenser and cooling South Korea, Sweden, and the United Kingdom. towers for heat rejection. Figure 3 shows the 32 states with operating LWRs in The nuclear steam supply system includes nuclear the United States. fuel that is configured as the ‘‘reactor core’’ in a reactor pressure vessel. Reactor coolant water is pumped through the reactor core and heated. Heated water passes through tube-and-shell heat exchangers 2. PRESSURIZED WATER REACTORS called ‘‘steam generators.’’ On the reactor side of the steam generator, the water enters the inside, or tube 2.1 Plant Design Characteristics side, of the steam generator, passes through, and Figure 4 provides a schematic view of a pressurized eventually returns to the reactor through a closed water reactor power plant. The power plant systems piping system, to be reheated. On the turbine- include a nuclear reactor and steam generator (called generator side, the water passes over the outside, or the nuclear steam supply system), which produce shell side, of the steam generator tubes and is heated. steam using energy from nuclear fission; a reactor Heat transfer through the tubes provides the energy ‘‘containment system,’’ which limits release of radio- to convert liquid water to steam on the shell side of 336 Nuclear Fission Reactors: Boiling Water and Pressurized Water Reactors the steam generator.