167-409: The Nippon Foundation ( 日本財団 , Nipponzaidan ) of Tokyo , Japan , is a private, non-profit grant-making organization. It was established in 1962 by Ryoichi Sasakawa . The foundation's mission is to direct Japanese motorboat racing revenue into philanthropic activities, it uses this money to pursue global maritime development and assistance for humanitarian work , both at home and abroad. In
334-487: A city 1,000 kilometres (620 mi) northeast of Chernobyl, where physicists from the V.G. Khlopin Radium Institute measured anomalous high levels of xenon-135 —a short half-life isotope—four days after the explosion. This meant that a nuclear event in the reactor may have ejected xenon to higher altitudes in the atmosphere than the later fire did, allowing widespread movement of xenon to remote locations. This
501-427: A combustible material, had been used in the construction of the roof of the reactor building and the turbine hall. Ejected material ignited at least five fires on the roof of the adjacent reactor No. 3, which was still operating. It was imperative to put out those fires and protect the cooling systems of reactor No. 3. Inside reactor No. 3, the chief of the night shift, Yuri Bagdasarov, wanted to shut down
668-535: A display of a North Korean spy vessel that had been sunk by the Japanese Self Defense Forces , and a survey of Okinotori Island . In addition, the foundation is providing support toward the establishment of a user-pays system to help the nations surrounding the Strait of Malacca in their efforts to both police the waters and maintain their environmental integrity. In international affairs,
835-491: A fatal radiation overdose from a criticality accident . The explosion and fire threw hot particles of the nuclear fuel and more dangerous fission products into the air. The residents of the surrounding area observed the radioactive cloud on the night of the explosion. The ionizing radiation levels in the worst-hit areas of the reactor building have been estimated to be 5.6 roentgens per second (R/s), equivalent to more than 20,000 roentgens per hour. A lethal dose
1002-543: A goal of increasing roadside trees in Tokyo to 1 million (from 480,000), and adding 1,000 ha (2,500 acres) of green space, 88 ha (220 acres) of which will be a new park named "Umi no Mori" (Sea Forest) which will be on a reclaimed island in Tokyo Bay which used to be a landfill. From 2007 to 2010, 436 ha (1,080 acres) of the planned 1,000 ha of green space was created and 220,000 trees were planted, bringing
1169-727: A leading global financial hub has diminished with the Lost Decades since the 1990s—when the Tokyo Stock Exchange (TSE) was the world's largest, with a market capitalization about 1.5 times that of the NYSE —the city is still a large financial hub, and the TSE remains among the world's top five major stock exchanges . Tokyo is categorized as an Alpha+ city by the Globalization and World Cities Research Network . The city
1336-432: A lesser extent Chiba and Ibaraki . Tokyo has been hit by powerful megathrust earthquakes in 1703, 1782, 1812, 1855, 1923, and much more indirectly (with some liquefaction in landfill zones) in 2011 ; the frequency of direct and large quakes is a relative rarity. The 1923 earthquake , with an estimated magnitude of 7.9, killed more than 100,000 people, the last time the urban area was directly hit. Mount Fuji
1503-475: A local government. The Tokyo Metropolitan Government administers the whole metropolis including the 23 special wards and the cities and towns that constitute the prefecture. It is headed by a publicly elected governor and metropolitan assembly. Its headquarters is in Shinjuku Ward. The governor of Tokyo is elected every four years. The incumbent governor, Yuriko Koike , was elected in 2016, following
1670-517: A major shopping and entertainment center. Various plans have been proposed for transferring national government functions from Tokyo to secondary capitals in other regions of Japan, to slow down rapid development in Tokyo and revitalize economically lagging areas of the country. These plans have been controversial within Japan and have yet to be realized. On September 7, 2013, the IOC selected Tokyo to host
1837-531: A reactor core fire that spread radioactive contaminants across the USSR and Europe. A 10-kilometre (6.2 mi) exclusion zone was established 36 hours after the accident, initially evacuating around 49,000 people. The exclusion zone was later expanded to 30 kilometres (19 mi), resulting in the evacuation of approximately 68,000 more people. Following the explosion, which killed two engineers and severely burned two others, an emergency operation began to put out
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#17327729479582004-403: A revised report, INSAG-7, in 1992. According to INSAG-1, the main cause of the accident was the operators' actions, but according to INSAG-7, the main cause was the reactor's design. Both reports identified an inadequate "safety culture" (INSAG-1 coined the term) at all managerial and operational levels as a major underlying factor. The nearby city of Pripyat was not immediately evacuated and
2171-589: A status distinct from refugees, whom Japan accepts in limited numbers. The foundation's support, totaling 8.58 billion yen ($ 64 million), is committed for three years and will be limited to 2,000 recipients. In June 2024, the Nippon Foundation also established the Ukrainian Evacuees Assistance Fund. The fund was closed at the end of March 2024 (circa 200 million yen donations as of March 5, 2024). According to conclusion of
2338-426: A test to simulate cooling the reactor during an accident in blackout conditions. The operators carried out the test despite an accidental drop in reactor power, and due to a design issue, attempting to shut down the reactor in those conditions resulted in a dramatic power surge. The reactor components ruptured, lost coolants, and the resulting steam explosions and meltdown destroyed the containment building, followed by
2505-484: A total of 68 major universities around the world. In the 1990s, on the home front, the Nippon Foundation invested heavily in the elderly of Japan, pushing for the improvement of retirement homes, building model retirement homes, and helping the nation to develop its hospice system nearly from the ground up. Related to this field, the foundation also began donating specially equipped vehicles to social welfare facilities and groups, enabling them to provide mobility services to
2672-490: A wetter summer and a drier winter. The growing season in Tokyo lasts for about 322 days from around mid-February to early January. Snowfall is sporadic, and occurs almost annually. Tokyo often sees typhoons every year, though few are strong. The wettest month since records began in 1876 was October 2004, with 780 millimeters (30 in) of rain, including 270.5 mm (10.65 in) on the ninth of that month. The most recent of four months on record to observe no precipitation
2839-530: A world city is said to have depreciated greatly during these three decades. Nonetheless, Tokyo still saw new urban developments during this period. Recent projects include Ebisu Garden Place, Tennōzu Isle , Shiodome , Roppongi Hills , Shinagawa , and the Marunouchi side of Tokyo Station . Land reclamation projects in Tokyo have also been going on for centuries. The most prominent is the Odaiba area, now
3006-704: Is Shofukuji in Higashi-Murayama . The current building was constructed in 1407, during the Muromachi period (1336–1573). Although greatly reduced in number by later fires, earthquakes, and air raids, a considerable number of Edo-era buildings survive to this day. The Tokyo Imperial Palace , which was occupied by the Tokugawa Shogunate as Edo Castle during the Edo Period (1603–1868), has many gates and towers dating from that era, although
3173-531: Is 40 m (131 ft). Chiba Prefecture borders it to the east, Yamanashi to the west, Kanagawa to the south, and Saitama to the north. Mainland Tokyo is further subdivided into the special wards (occupying the eastern half) and the Tama area ( 多摩地域 ) stretching westwards. Tokyo has a latitude of 35.65 (near the 36th parallel north ), which makes it more southern than Rome (41.90), Madrid (40.41), New York City (40.71) and Beijing (39.91). Within
3340-473: Is December 1995. Annual precipitation has ranged from 879.5 mm (34.63 in) in 1984 to 2,229.6 mm (87.78 in) in 1938. See or edit raw graph data . Tokyo's climate has warmed significantly since temperature records began in 1876. The western mountainous area of mainland Tokyo, Okutama also lies in the humid subtropical climate (Köppen classification: Cfa ). The climates of Tokyo's offshore territories vary significantly from those of
3507-713: Is a reference to the original settlement's location at the meeting of the Sumida River and Tokyo Bay . During the Meiji Restoration in 1868, the name of the city was changed to Tokyo ( 東京 , from 東 tō "east", and 京 kyō "capital") , when it became the new imperial capital, in line with the East Asian tradition of including the word capital ( 京 ) in the name of the capital city (for example, Kyoto ( 京都 ), Keijō ( 京城 ), Beijing ( 北京 ), Nanjing ( 南京 ), and Xijing ( 西京 )). During
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#17327729479583674-512: Is about 100 km (62 mi) southwest of Tokyo. There is a low risk of eruption. The last recorded was the Hōei eruption which started on December 16, 1707, and ended about January 1, 1708 (16 days). During the Hōei eruption, the ash amount was 4 cm in southern Tokyo (bay area) and 2 cm to 0.5 cm in central Tokyo. Kanagawa had 16 cm to 8 cm ash and Saitama 0.5 to 0 cm. If
3841-516: Is also recognized as one of the world's most livable ones; it was ranked fourth in the world in the 2021 edition of the Global Livability Ranking . Tokyo has also been ranked as the safest city in the world in multiple international surveys. Tokyo was originally known as Edo ( 江戸 ) , a kanji compound of 江 ( e , "cove, inlet") and 戸 ( to , "entrance, gate, door"). The name, which can be translated as " estuary ",
4008-586: Is an international research and development hub and an academic center with several major universities , including the University of Tokyo , the top-ranking university in the country. Tokyo Station is the central hub for the Shinkansen , Japan's high-speed railway network, and Shinjuku Station in Tokyo is the world's busiest train station. The city is home to the world's tallest tower, Tokyo Skytree . The Tokyo Metro Ginza Line , which opened in 1927,
4175-474: Is around 500 roentgens (~5 Gray (Gy) in modern radiation units) over five hours. In some areas, unprotected workers received fatal doses in less than a minute. Unfortunately, a dosimeter capable of measuring up to 1,000 R/s was buried in the rubble of a collapsed part of the building, and another one failed when turned on. Most remaining dosimeters had limits of 0.001 R/s and therefore read "off scale". The reactor crew could ascertain only that
4342-456: Is believed to be the first explosion that many heard. This explosion ruptured further fuel channels, as well as severing most of the coolant lines feeding the reactor chamber. As a result, the remaining coolant flashed to steam and escaped the reactor core. The total water loss combined with a high positive void coefficient further increased the reactor's thermal power. A second, more powerful explosion occurred about two or three seconds after
4509-422: Is estimated to have had the power equivalent of 225 tons of TNT . According to observers outside Unit 4, burning lumps of material and sparks shot into the air above the reactor. Some of them fell onto the roof of the machine hall and started a fire. About 25% of the red-hot graphite blocks and overheated material from the fuel channels was ejected. Parts of the graphite blocks and fuel channels were out of
4676-515: Is in the tropical savanna climate zone (Köppen classification: Aw ). Tokyo's Izu and Ogasawara islands are affected by an average of 5.4 typhoons a year, compared to 3.1 in mainland Kantō. Tokyo is near the boundary of three plates , making it an extremely active region for smaller quakes and slippage which frequently affect the urban area with swaying as if in a boat, although epicenters within mainland Tokyo (excluding Tokyo's 2,000 km (1,243 mi)–long island jurisdiction) are quite rare. It
4843-465: Is located on the Kantō Plain with five river systems and dozens of rivers that expand during each season. Important rivers are Edogawa , Nakagawa , Arakawa , Kandagawa , Megurogawa and Tamagawa . In 1947, Typhoon Kathleen struck Tokyo, destroying 31,000 homes and killing 1,100 people. In 1958, Typhoon Ida dropped 400 mm (16 in) of rain in a single week, causing streets to flood. In
5010-458: Is not uncommon in the metro area to have hundreds of these minor quakes (magnitudes 4–6) that can be felt in a single year, something local residents merely brush off but can be a source of anxiety not only for foreign visitors but for Japanese from elsewhere as well. They rarely cause much damage (sometimes a few injuries) as they are either too small or far away as quakes tend to dance around the region. Particularly active are offshore regions and to
5177-581: Is part of the Kantō region on the central coast of Honshu , Japan's largest island. Tokyo serves as Japan's economic center and the seat of both the Japanese government and the Emperor of Japan . The Tokyo Metropolitan Government administers Tokyo's central 23 special wards (which formerly made up Tokyo City ), various commuter towns and suburbs in its western area , and two outlying island chains known as
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5344-461: Is possible that well over half of the graphite burned out. It was thought by some that the core fire was extinguished by a combined effort of helicopters dropping more than 5,000 tonnes (11 million pounds) of sand, lead, clay, and neutron-absorbing boron onto the burning reactor. It is now known that virtually none of these materials reached the core. Historians estimate that about 600 Soviet pilots risked dangerous levels of radiation to fly
5511-666: Is the oldest underground metro line in Asia–Pacific . Tokyo's nominal gross domestic output was 113.7 trillion yen or US$ 1.04 trillion in FY2021 and accounted for 20.7% of the country's total economic output, which converts to 8.07 million yen or US$ 73,820 per capita. Including the Greater Tokyo Area, Tokyo is the second-largest metropolitan economy in the world after New York , with a 2022 gross metropolitan product estimated at US$ 2.08 trillion. Although Tokyo's status as
5678-527: Is the third-smallest, above only Osaka and Kagawa . Its administrative structure is similar to that of Japan's other prefectures . The 23 special wards ( 特別区 , tokubetsu-ku ) , which until 1943 constituted the city of Tokyo , are self-governing municipalities , each having a mayor, a council, and the status of a city. In addition to these 23 special wards, Tokyo also includes 26 more cities ( 市 -shi ), five towns ( 町 -chō or machi ), and eight villages ( 村 -son or -mura ), each of which has
5845-467: The 1973 oil crisis put an end to the rapid post-war recovery and development of Japan's economy, its position as the world's second-largest economy at the time had seemed secure by that point, remaining so until 2010 when it was surpassed by China . Tokyo's development was sustained by its status as the economic, political, and cultural hub of such a country. In 1978, after years of the intense Sanrizuka Struggle , Narita International Airport opened as
6012-613: The 2020 Summer Olympics . Thus, Tokyo became the first Asian city to host the Olympic Games twice. However, the 2020 Olympic Games were postponed and held from July 23 to August 8, 2021, as a result of the COVID-19 pandemic . Under Japanese law , the prefecture of Tokyo is designated as a to ( 都 ) , translated as metropolis . Tokyo Prefecture is the most populous prefecture and the densest, with 6,100 inhabitants per square kilometer (16,000/sq mi); by geographic area it
6179-580: The Arakawa River are most at risk of flooding. Tokyo's buildings are too diverse to be characterized by any specific archtectural style, but it can be generally said that a majority of extant structures were built in the past a hundred years; twice in recent history has the metropolis been left in ruins: first in the 1923 Great Kantō earthquake and later after extensive firebombing in World War II . The oldest known extant building in Tokyo
6346-565: The Ethiopian famine of the mid-1980s , the foundation began a program of agricultural education throughout sub-Saharan Africa that eventually reached 14 countries, improving farmers’ yields by up to six times in some places. Finally, as a part of its human resources development program, the foundation created the Sasakawa Young Leaders’ Fellowship Fund, a program that would eventually establish million-dollar funds at
6513-677: The Kasumigaseki district in Chiyoda, and the name Kasumigaseki is often used as a metonym for the Japanese national civil service . Tokyo has 25 constituencies for the House of Representatives , 18 of which were won by the ruling Liberal Democrats and 7 by the main opposition Constitutional Democrats in the 2021 general election . Apart from these seats, through the Tokyo proportional representation block , Tokyo sends 17 more politicians to
6680-479: The Meiji Period . Some gardens were immune from such fates and are today open to the public; Hamarikyu ( Kofu Tokugawa family ), Shibarikyu ( Kishu Tokugawa family ), Koishikawa Korakuen ( Mito Tokugawa family ), Rikugien ( Yanagisawa family ), and Higo Hosokawa Garden ( Hosokawa family ). The Akamon , which is now widely seen as a symbol of the University of Tokyo , was originally built to commemorate
6847-456: The Meiji Restoration . The high survival rate of concrete buildings promoted the transition from timber and brick architecture to modern, earthquake-proof construction. The Tokyo Metro Ginza Line portion between Ueno and Asakusa , the first underground railway line built outside Europe and the American continents, was completed on December 30, 1927. Although Tokyo recovered robustly from
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7014-518: The Ministry of Finance were also relocated to Tokyo by 1871, and the first railway line in the country was opened on 14 October 1872, connecting Shimbashi ( Shiodome ) and Yokohama ( Sakuragicho ), which is now part of the Tokaido line . The 1870s saw the establishment of other institutions and facilities that now symbolize Tokyo, such as Ueno Park (1873), the University of Tokyo (1877) and
7181-507: The Ministry of Justice building (1895), the International Library of Children's Literature (1906) and Mistubishi building one (1894, rebuilt in 2010) are some of the few brick survivors from this period. It was regarded as fashionable by some members of the Japanese aristocracy to build their Tokyo residences in grand and modern styles, and some of these buildings still exist, although most are in private hands and open to
7348-563: The Ogasawara Islands , which had been under control of the US since the war ended, were returned in 1968. Ryokichi Minobe , a Marxian economist who served as the governor for 12 years starting in 1967, is remembered for his welfare state policy, including free healthcare for the elderly and financial support for households with children, and his ‘war against pollution’ policy, as well as the large government deficit they caused. Although
7515-726: The Shuto Expressway to meet the increased demand brought about by the 1964 Tokyo Olympics , the first Olympic Games held in Asia. Around this time, the 31-metre height restriction, imposed on all buildings since 1920, was relaxed due to the increased demand for office buildings and advancements in earthquake-proof construction. Starting with the Kasumigaseki Building (147 metres) in 1968, skyscrapers began to dominate Tokyo's skyline. During this period of rapid rebuilding, Tokyo celebrated its 500th anniversary in 1956 and
7682-624: The Tokyo Islands . Despite most of the world recognizing Tokyo as a city, since 1943 its governing structure has been more akin to a prefecture, with an accompanying Governor and Assembly taking precedence over the smaller municipal governments which make up the metropolis. Notable special wards in Tokyo include Chiyoda , the site of the National Diet Building and the Tokyo Imperial Palace ; Shinjuku ,
7849-505: The Tokyo Metropolis (東京都, Tōkyō-to ). This reorganization aimed to create a more centralized and efficient administrative structure to better manage resources, urban planning, and civil defence during wartime. The Tokyo Metropolitan Government thus became responsible for both prefectural and city functions while administering cities, towns, and villages in the suburban and rural areas. Although Japan enjoyed significant success in
8016-423: The Tokyo Metropolis , is the capital city of Japan . With a population of over 14 million residents within the city proper as of 2023, it is one of the most populous cities in the world . The Greater Tokyo Area , which includes Tokyo and parts of six neighboring prefectures , is the most-populous metropolitan area in the world, with 41 million residents as of 2024 . Located at the head of Tokyo Bay , Tokyo
8183-831: The Tokyo Metropolitan Government Building (1991). Kisho Kurokawa was also active in the city, and his works there include the National Art Center (2005) and the Nakagin Capsule Tower (1972). Other notable contemporary buildings in Tokyo include the Tokyo Dome , Mode Gakuen Cocoon Tower , Roppongi Hills , Tokyo International Forum , and Asahi Beer Hall . As of October 2012, the official intercensal estimate showed 13.506 million people in Tokyo, with 9.214 million living within Tokyo's 23 wards. During
8350-424: The Tokyo Stock Exchange (1878). The rapid modernization of the country was driven from Tokyo, with its business districts such as Marunouchi filled with modern brick buildings and the railway network serving as a means to help the large influx of labour force needed to keep the development of the economy. The City of Tokyo was officially established on May 1, 1889. The Imperial Diet , the national legislature of
8517-479: The reaction of red-hot graphite with steam that produced hydrogen and carbon monoxide . Another hypothesis, by Konstantin Checherov, published in 1998, was that the second explosion was a thermal explosion of the reactor due to the uncontrollable escape of fast neutrons caused by the complete water loss in the reactor core. The force of the second explosion and the ratio of xenon radioisotopes released after
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#17327729479588684-432: The scram continued, the reactor output jumped to around 30,000 MW thermal, 10 times its normal operational output, the indicated last reading on the control panel. Some estimate the power spike may have gone 10 times higher than that. It was not possible to reconstruct the precise sequence of the processes that led to the destruction of the reactor and the power unit building, but a steam explosion appears to have been
8851-586: The second-largest in the world at the time behind that of the United States . As of 2023 , the city is home to 29 of the world's 500 largest companies, as listed in the annual Fortune Global 500 ; the second-highest number of any city. In the 20th and 21st centuries, Tokyo became the first city in Asia to host the Summer Olympics and Paralympics in 1964, and again in 2021, and it also hosted three G7 summits in 1979, 1986, and 1993. Tokyo
9018-557: The 1930s but canceled due to the war. However, due to the monetary contraction policy known as the Dodge Line , named after Joseph Dodge , the neoliberal economic advisor to MacArthur, the plan had to be reduced to a minimal one focusing on transport and other infrastructure. In 1947, the 35 pre-war special wards were reorganized into the current 23 wards . Tokyo did not experience fast economic growth until around 1950, when heavy industry output returned to pre-war levels. Since around
9185-547: The 1950s and 1960s, the government invested 6–7% of the national budget on disaster and risk reduction. A huge system of dams, levees and tunnels was constructed. The purpose is to manage heavy rain, typhonic rain, and river floods. Tokyo has currently the world's largest underground floodwater diversion facility called the Metropolitan Area Outer Underground Discharge Channel (MAOUDC). It took 13 years to build and
9352-679: The 26th Centenary of the Enthronement of Emperor Jimmu celebrations took place on a grand scale to boost morale and increase the sense of national identity in the same year. On 8 December 1941, Japan attacked the American bases at Pearl Harbor in Hawaii , entering the Second World War against the Allied Powers . The wartime regime greatly affected life in the city. In 1943, Tokyo City merged with Tokyo Prefecture to form
9519-426: The 5.5 MW needed to run one main pump. Special counterweights on each pump provided coolant via inertia to bridge the gap to generator startup. However, a potential safety risk existed in the event that a station blackout occurred simultaneously with the rupture of a coolant pipe. In this scenario the emergency core cooling system (ECCS) is needed to pump additional water into the core. It had been theorized that
9686-452: The House of Representatives, 6 of whom were members of the ruling LDP in the 2021 election. The Tokyo at-large district , which covers the entire metropolis, sends 12 members to the House of Councillors . The mainland portion of Tokyo lies northwest of Tokyo Bay and measures about 90 km (56 mi) east to west and 25 km (16 mi) north to south. The average elevation in Tokyo
9853-613: The Investigative Commission appointed by the Peru Congress, the Nippon Foundation was one of the organizations providing financial support for the forced sterilizations of impoverished Peruvians , initially laid out in the leaked documents of " Plan Verde " and subsequently executed by the Alberto Fujimori government as part of its National Population Program . Tokyo Tokyo , officially
10020-535: The Kiev grid controller allowed the reactor shutdown to resume. The day shift had long since departed, the evening shift was also preparing to leave, and the night shift would not take over until midnight, well into the job. According to plan, the test should have been finished during the day shift, and the night shift would only have had to maintain decay heat cooling systems in an otherwise shut-down plant. The night shift had very limited time to prepare for and carry out
10187-609: The Los Angeles 1984 Organizing Committee for use in those Olympics. It was much more than the LA Organizing Committee wanted to use, and they were forced to come up with a 25-minute fireworks show to accommodate the gift and NOT slight the Foundation. Sometime around 1988–1989, the foundation dropped that moniker and went by several other names including the all-inclusive "Nippon" Foundation. In response to
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#173277294795810354-542: The Meiji government, Edo was renamed Tokyo (Eastern Capital) on 3 September 1868. Emperor Meiji visited the city once at the end of that year and eventually moved there in 1869. Tokyo had already been the nation's political center for nearly three centuries, and the emperor's residence made it a de facto imperial capital as well, with the former Edo Castle becoming the Imperial Palace . Government ministries such as
10521-641: The Mitsui Headquarters (1929), Mitsukoshi Nihonbashi flagship store (1914, refurbished in 1925), Takashimaya Nihonbashi flagship store (1932), Wako in Ginza (1932) and Isetan Shinjuku flagship store (1933). This spread of earthquake and fire-resistant architecture reached council housing too, most notably the Dōjunkai apartments . The 1930s saw the rise of styles that combined characteristics of both traditional Japanese and modern designs. Chuta Ito
10688-493: The Sasakawa Memorial Health Foundation for the purpose of eliminating leprosy as a public health problem—an effort that has resulted in its elimination in all but 1 of the 122 countries where the disease was initially prevalent. Support for the maritime world remained an important focus in the 1980s, building on the work of the previous decade. Examples of projects include "Swift Wings", which
10855-426: The US dollar, had a devastating effect on Japan's manufacturing sector, particularly affecting small to mid-size companies based in Tokyo. This led the government to adopt a domestic-demand-focused economic policy, ultimately causing an asset price bubble . Land redevelopment projects were planned across the city, and real estate prices skyrocketed. By 1990, the estimated value of the Imperial Palace surpassed that of
11022-520: The US seized control of the Mariana Islands . From these islands, newly developed long-range B-29 bombers could conduct return journeys. The bombing of Tokyo in 1944 and 1945 is estimated to have killed between 75,000 and 200,000 civilians and left more than half of the city destroyed. The deadliest night of the war came on March 9–10, 1945, the night of the American " Operation Meetinghouse " raid. Nearly 700,000 incendiary bombs were dropped on
11189-490: The absence of further operator action, a process known as reactor poisoning . In steady-state operation, this is avoided because xenon-135 is "burned off" as quickly as it is created, becoming highly stable xenon-136 . With the reactor power reduced, high quantities of previously produced iodine-135 were decaying into the neutron-absorbing xenon-135 faster than the reduced neutron flux could "burn it off". Xenon poisoning in this context made reactor control more difficult, but
11356-468: The accident led Sergei A. Pakhomov and Yuri V. Dubasov in 2009 to theorize that the second explosion could have been an extremely fast nuclear power transient resulting from core material melting in the absence of its water coolant and moderator. Pakhomov and Dubasov argued that there was no delayed supercritical increase in power but a runaway prompt criticality , similar to the explosion of a fizzled nuclear weapon . Their evidence came from Cherepovets ,
11523-577: The administrative boundaries of Tokyo Metropolis are two island chains in the Pacific Ocean directly south: the Izu Islands , and the Ogasawara Islands , which stretch more than 1,000 km (620 mi) away from the mainland. Because of these islands and the mountainous regions to the west, Tokyo's overall population density figures far under-represent the real figures for the urban and suburban regions of Tokyo. The former city of Tokyo and
11690-478: The area that had been Tokyo City until 1943, 30 other municipalities are located in the Tama area , and the remaining 9 are on Tokyo's outlying islands. Tokyo has enacted a measure to cut greenhouse gases. Governor Shintaro Ishihara created Japan's first emissions cap system , aiming to reduce greenhouse gas emission by a total of 25% by 2020 from the 2000 level. Tokyo is an example of an urban heat island , and
11857-569: The assumption that the new dosimeter must have been defective. Akimov stayed in the reactor building until morning, sending members of his crew to try to pump water into the reactor. None of them wore any protective gear. Most, including Akimov, died from radiation exposure within three weeks. The IAEA had created the International Nuclear Safety Advisory Group (INSAG) in 1985. INSAG produced two significant reports on Chernobyl: INSAG-1 in 1986, and
12024-458: The automatic regulators' ionization sensors. The result was a sudden power drop to an unintended near- shutdown state, with a power output of 30 MW thermal or less. The exact circumstances that caused the power drop are unknown. Most reports attribute the power drop to Toptunov's error, but Dyatlov reported that it was due to a fault in the AR-2 system. The reactor was now producing only 5% of
12191-475: The city's administrative center; and Shibuya , a commercial, cultural, and business hub in the city. Before the 17th century, Tokyo, then known as Edo , was mainly a fishing village. It gained political prominence in 1603 when it became the seat of the Tokugawa shogunate . By the mid-18th century, Edo was among the world's largest cities, with over a million residents. Following the Meiji Restoration in 1868,
12358-562: The city. The climate of Chichijima in Ogasawara village is on the boundary between the tropical savanna climate (Köppen classification: Aw ) and the tropical rainforest climate (Köppen classification: Af ). It is approximately 1,000 km (621 mi) south of the Greater Tokyo Area , resulting in much different climatic conditions. Tokyo's easternmost territory, the island of Minamitorishima in Ogasawara village ,
12525-430: The core in a loss-of-coolant accident . Approval from the site chief engineer had been obtained according to regulations. The test procedure was intended to run as follows: The test was to be conducted during the day-shift of 25 April 1986 as part of a scheduled reactor shutdown. The day shift had been instructed in advance on the reactor operating conditions to run the test, and a special team of electrical engineers
12692-469: The core, therefore entering the reactor very close to the boiling point. Unlike other light-water reactor designs, the RBMK design at that time had a positive void coefficient of reactivity at typical fuel burnup levels. This meant that the formation of steam bubbles (voids) from boiling cooling water intensified the nuclear chain reaction owing to voids having lower neutron absorption than water. Unknown to
12859-636: The country, leading to Japan joining the Second World War as an Axis power . Due to the country's political isolation on the international stage caused by its military aggression in China and the increasingly unstable geopolitical situations in Europe, Тоkуо had to give up hosting the 1940 Summer Olympics in 1938. Rationing started in June 1940 as the nation braced itself for another world war, while
13026-524: The country, was established in Tokyo in 1889, and it has ever since been operating in the city. On 1 September 1923, the Great Kanto Earthquake struck the city, and the earthquake and subsequent fire killed an estimated 105,000 citizens. The loss amounted to 37 percent of the country's economic output. On the other hand, the destruction provided an opportunity to reconsider the planning of the city, which had changed its shape hastily after
13193-476: The country. In the 1970s, the foundation continued to pursue its efforts to improve social services through such measures as the distribution of ambulances, training in the use of fire fighting equipment, the development of preventative measures for earthquakes and PR for the fire-fighting sector. It also donated medical ships to provide medical aid for people living on remote islands in Japan's inland sea. In 1971, it began its overseas work, and in 1974 established
13360-442: The daytime, the population swells by over 2.5 million as workers and students commute from adjacent areas. This effect is even more pronounced in the three central wards of Chiyoda , Chūō , and Minato , whose collective population as of the 2005 National Census was 326,000 at night, but 2.4 million during the day. According to April 2024 official estimates, Setagaya (942,003), Nerima (752,608), and Ota (748,081) were
13527-465: The disabling of the emergency core cooling system . Meanwhile, another regional power station unexpectedly went offline. At 14:00, the Kiev electrical grid controller requested that the further reduction of Chernobyl's output be postponed, as power was needed to satisfy the peak evening demand. Soon, the day shift was replaced by the evening shift. Despite the delay, the emergency core cooling system
13694-652: The disaster. The United Nations Scientific Committee on the Effects of Atomic Radiation estimates fewer than 100 deaths have resulted from the fallout. Predictions of the eventual total death toll vary; a 2006 World Health Organization study projected 9,000 cancer-related fatalities in Ukraine, Belarus, and Russia. Pripyat was abandoned and replaced by the purpose-built city of Slavutych . The Chernobyl Nuclear Power Plant sarcophagus , completed in December 1986, reduced
13861-488: The driver of one of the fire engines, later described what happened: We arrived there at 10 or 15 minutes to two in the morning ... We saw graphite scattered about. Misha asked: "Is that graphite?" I kicked it away. But one of the fighters on the other truck picked it up. "It's hot," he said. The pieces of graphite were of different sizes, some big, some small enough to pick them up [...] We didn't know much about radiation. Even those who worked there had no idea. There
14028-460: The early Meiji period , the city was sometimes called "Tōkei", an alternative pronunciation for the same characters representing "Tokyo", making it a kanji homograph . Some surviving official English documents use the spelling "Tokei"; however, this pronunciation is now obsolete. Tokyo was originally a village called Edo , part of the old Musashi Province . Edo was first fortified by the Edo clan in
14195-581: The earthquake and new cultural and liberal political movements, such as Taishō Democracy , spread, the 1930s saw an economic downturn caused by the Great Depression and major political turmoil. Two attempted military coups d'état happened in Tokyo, the May 15 incident in 1932 and the February 26 incident in 1936. This turmoil eventually allowed the military wings of the government to take control of
14362-482: The east end of the city ( shitamachi , 下町), an area with a high concentration of factories and working-class houses. Two-fifths of the city were completely burned, more than 276,000 buildings were destroyed, 100,000 civilians were killed, and 110,000 more were injured. Numerous Edo and Meiji-era buildings of historical significance were destroyed, including the main building of the Imperial Palace , Sensō-ji , Zōjō-ji , Sengaku-ji and Kabuki-za . Between 1940 and 1945,
14529-405: The elderly and those with disability. The decade also saw one of Japan's worst earthquakes of the 20th century , and the disorganization of volunteer groups in the wake of the quake lead the foundation to put special attention on bringing these many groups together under one umbrella—the volunteer support center—a central body that coordinated volunteer effort in the event of a major disaster. In
14696-521: The entire state of California . The Tokyo Stock Exchange became the largest stock exchange in the world by market capitalization, with the Tokyo-based NTT becoming the most highly valued company globally. After the bubble burst in the early 1990s, Japan experienced a prolonged economic downturn called the " Lost Decades ", which was charactized by extremely low or negative economic growth, deflation, stagnant asset prices. Tokyo's status as
14863-664: The establishment of the WHO Sasakawa Health prize and a massive project to aid the victims of the Chernobyl nuclear power disaster , under which the foundation spent a total of more than US$ 50 million over ten years, screening over 200,000 children for thyroid cancer. Up until 1988, the foundation went by the name the Japanese Shipbuilding Industry Foundation (JSIF), and even donated some supposedly $ 500,000 worth of fireworks to
15030-652: The experiment. Anatoly Dyatlov , deputy chief-engineer of the Chernobyl Nuclear Power Plant (ChNPP), was present to direct the test. He was one of the test's chief authors and he was the highest-ranking individual present. Unit Shift Supervisor Aleksandr Akimov was in charge of the Unit 4 night shift, and Leonid Toptunov was the Senior Reactor Control Engineer responsible for the reactor's operational regimen, including
15197-463: The fires and stabilize the reactor. Of the 237 workers hospitalized, 134 showed symptoms of acute radiation syndrome (ARS); 28 of them died within three months. Over the next decade, 14 more workers (nine of whom had ARS) died of various causes mostly unrelated to radiation exposure. It is the only instance in commercial nuclear power history where radiation-related fatalities occurred. As of 2011, 15 childhood thyroid cancer deaths were attributed to
15364-435: The fires. First on the scene was a Chernobyl Power Station firefighter brigade under the command of Lieutenant Volodymyr Pravyk , who died on 11 May 1986 of acute radiation sickness . They were not told how dangerously radioactive the smoke and the debris were, and may not even have known that the accident was anything more than a regular electrical fire: "We didn't know it was the reactor. No one had told us." Grigorii Khmel,
15531-427: The first; this explosion dispersed the damaged core and effectively terminated the nuclear chain reaction . This explosion compromised more of the reactor containment vessel and ejected hot lumps of graphite moderator. The ejected graphite and the demolished channels still in the remains of the reactor vessel caught fire on exposure to air, significantly contributing to the spread of radioactive fallout . The explosion
15698-517: The five-storey pagoda and the Shimizudo. The Nezu Shrine and Gokokuji were built by the fifth shogun Tsunayoshi Tokugawa in the late 1600s. All feudal lords ( daimyo ) had large Edo houses where they stayed when in Edo; at one point, these houses amounted to half the total area of Edo. None of the grand Edo-era daimyo houses still exist in Tokyo, as their vast land footprint made them easy targets for redevelopment programs for modernization during
15865-669: The foundation has most recently built more than 100 elementary schools in Myanmar and 100 in Cambodia . It has established a novel program to provide Mongolian nomadic families with boxes full of traditional medicines that can be replenished, at the cost only of those medicines used, a few times a year, when they come to market. Following the start of the Russian invasion of Ukraine , the Nippon Foundation has provided aid to 1,921 Ukrainians for travel and living expenses in Japan as evacuees,
16032-712: The foundation has promoted sign language with the aim of allowing deaf people to fully participate in society, in this way, they created scholarships for deaf people at Gallaudet University and the National Technical Institute for the Deaf (NTID) of USA . The current chairman is Yohei Sasakawa , World Health Organization Goodwill Ambassador for Leprosy Elimination, Special Envoy of the Government of Japan for National Reconciliation in Myanmar, and
16199-446: The full availability of the emergency generators, but would alleviate the situation. The turbine run-down energy capability still needed to be confirmed experimentally, and previous tests had ended unsuccessfully. An initial test carried out in 1982 indicated that the excitation voltage of the turbine-generator was insufficient. The electrical system was modified, and the test was repeated in 1984 but again proved unsuccessful. In 1985,
16366-464: The generators were to have completely picked up the MCPs' power needs by 01:23:43. As the momentum of the turbine generator decreased, so did the power it produced for the pumps. The water flow rate decreased, leading to increased formation of steam voids in the coolant flowing up through the fuel pressure tubes. At 01:23:40, a scram (emergency shutdown) of the reactor was initiated as the experiment
16533-541: The humanitarian field, it focuses on such fields as social welfare , public health , and education . The foundation has also been criticized for promoting Japanese historical revisionism , particularly in whitewashing Japanese war crimes committed in World War II . In 2001, the Peruvian Congress determined that the foundation financed forced sterilizations in that country (1990-1999). Since 2003
16700-583: The imperial capital in Kyoto was moved to Edo, and the city was renamed Tokyo ( lit. ' Eastern Capital ' ). In 1923, Tokyo was damaged substantially by the Great Kantō earthquake , and the city was later badly damaged by allied bombing raids during World War II . Beginning in the late 1940s, Tokyo underwent rapid reconstruction and expansion that contributed to the era's so-called Japanese economic miracle in which Japan's economy propelled to
16867-546: The initial stages of the war and rapidly expanded its sphere of influence, the Doolittle Raid on 18 April 1942, marked the first direct foreign attack on Tokyo. Although the physical damage was minimal, the raid demonstrated the vulnerability of the Japanese mainland to air attacks and boosted American morale. Large-scale Allied air bombing of cities in the Japanese home islands, including Tokyo, began in late 1944 when
17034-450: The late twelfth century. In 1457, Ōta Dōkan built Edo Castle to defend the region from the Chiba clan . After Dōkan was assassinated in 1486, the castle and the area came to be possessed by several feudal lords. In 1590, Tokugawa Ieyasu was granted the Kantō region by Toyotomi Hideyoshi and moved there from his ancestral land of Mikawa Province . He greatly expanded the castle, which
17201-553: The latter is the tallest tower in both Japan and the world, and the second tallest structure in the world after the Burj Khalifa in Dubai . With a scheduled completion date in 2027, Torch Tower (385m) will overtake Azabudai Hills Mori JP Tower (325.2m) as the tallest building in Tokyo. Kenzo Tange designed notable contemporary buildings in Tokyo, including Yoyogi National Gymnasium (1964), St. Mary's Cathedral (1967), and
17368-429: The low levels in one half of the steam/water separator drums, with accompanying drum separator pressure warnings. In response, personnel triggered rapid influxes of feedwater. Relief valves opened to relieve excess steam into a turbine condenser . When a power level of 200 MW was reattained, preparation for the experiment continued, although the power level was much lower than the prescribed 700 MW. As part of
17535-646: The main palace buildings and the tenshu tower have been lost. Numerous temple and shrine buildings in Tokyo date from this era: the Ueno Toshogu still maintains the original 1651 building built by the third shogun Iemitsu Tokugawa . Although partially destroyed during the Second World War, Zojo-ji , which houses the Tokugawa family mausoleum, still has grand Edo-era buildings such as the Sangedatsu gate. Kaneiji has grand 17th-century buildings such as
17702-437: The majority of Tokyo prefecture lie in the humid subtropical climate zone ( Köppen climate classification : Cfa ), with hot, humid summers and mild to cool winters with occasional cold spells. The region, like much of Japan, experiences a one-month seasonal lag . The warmest month is August, which averages 26.9 °C (80.4 °F). The coolest month is January, averaging 5.4 °C (41.7 °F). The record low temperature
17869-422: The majority of its resources to rebuilding in the wake of the consistent fires, earthquakes , and other devastating natural disasters that plagued the city. Edo grew into one of the largest cities in the world with a population reaching one million by the 18th century. This prolonged period of seclusion however came to an end with the arrival of American Commodore Matthew C. Perry in 1853. Commodore Perry forced
18036-651: The maritime development field, the foundation began to turn its eye to the disparity in the level of training received by maritime experts in various countries. As a result, it provided funding for a scholarship for people from developing countries to attend the World Maritime University , in Malmö, Sweden. In perhaps an even broader effort, it created the International Association of Maritime Universities, uniting 50 institutions around
18203-459: The marriage of a shogun's daughter into the Maeda clan , one of the most affluent of the feudal lords, while the campus itself occupies their former edo estate. The Meiji era saw a rapid modernization in architectural styles as well; until the Great Kanto Earthquake in 1923 exposed their weakness to seimic shocks, grand brick buildings were constantly built across the city. Tokyo Station (1914),
18370-537: The maximum severity on the International Nuclear Event Scale , the other being the 2011 Fukushima nuclear accident . The response involved more than 500,000 personnel and cost an estimated 18 billion rubles (about $ 68 billion USD in 2019). It remains the worst nuclear disaster in history, and the costliest disaster in human history , with an estimated cost of $ 700 billion USD. The disaster occurred while running
18537-417: The minimum initial power level prescribed for the test. This low reactivity inhibited the burn-off of xenon-135 within the reactor core and hindered the rise of reactor power. To increase power, control-room personnel removed numerous control rods from the reactor. Several minutes elapsed before the reactor was restored to 160 MW at 00:39, at which point most control rods were at their upper limits, but
18704-523: The morning. ' " He also stated, "Of course we knew! If we'd followed regulations, we would never have gone near the reactor. But it was a moral obligation—our duty. We were like kamikaze ." The immediate priority was to extinguish fires on the roof of the station and the area around the building containing Reactor No. 4 to protect No. 3. The fires were extinguished by 5:00, but many firefighters received high doses of radiation. The fire inside Reactor No. 4 continued to burn until 10 May 1986; it
18871-413: The most populous wards and municipalities in Tokyo. The least inhabited of all Tokyo municipalities are remote island villages such as Aogashima (150), Mikurajima (289), and Toshima (306). In 2021, Tokyo's average and median ages were both 45.5 years old. This is below the national median age of 49.0, placing Tokyo among the youngest regions in Japan. 16.8% of the population was below 15, while 34.6%
19038-465: The movement of the control rods . 25-year-old Toptunov had worked independently as a senior engineer for approximately three months. The test plan called for a gradual decrease in reactor power to a thermal level of 700–1000 MW, and an output of 720 MW was reached at 00:05 on 26 April. However, due to the reactor's production of a fission byproduct, xenon-135 , which is a reaction-inhibiting neutron absorber , power continued to decrease in
19205-408: The new gateway to the city, while the relatively small Haneda Airport switched to primarily domestic flights. West Shinjuku , which had been occupied by the vast Yodobashi Water Purification Centre until 1965, became the site of an entirely new business district characterized by skyscrapers surpassing 200 metres during this period. The American-led Plaza Accord in 1985, which aimed to depreciate
19372-407: The next event. There is a general understanding that it was explosive steam pressure from the damaged fuel channels escaping into the reactor's exterior cooling structure that caused the explosion that destroyed the reactor casing, tearing off and blasting the upper plate called the upper biological shield, to which the entire reactor assembly is fastened, through the roof of the reactor building. This
19539-553: The opening of the ports of Shimoda and Hakodate , leading to an increase in the demand for new foreign goods and subsequently a severe rise in inflation. Social unrest mounted in the wake of these higher prices and culminated in widespread rebellions and demonstrations, especially in the form of the "smashing" of rice establishments. Meanwhile, supporters of the Emperor leveraged the disruption caused by widespread rebellious demonstrations to further consolidate power, which resulted in
19706-414: The operators, the void coefficient was not counterbalanced by other reactivity effects in the given operating regime, meaning that any increase in boiling would produce more steam voids which further intensified the chain reaction, leading to a positive feedback loop. Given this characteristic, reactor No. 4 was now at risk of a runaway increase in its core power with nothing to restrain it. The reactor
19873-499: The overthrow of the Tokugawa shogunate , for the first time in a few centuries, the Emperor ceased to be a mere figurehead and became both the de facto and de jure ruler of the country. Hisoka Maejima advocated for the relocation of the capital functions to Tokyo, recognizing the advantages of the existing infrastructure and the vastness of the Kanto Plain compared to the relatively small Kyoto basin . After being handed over to
20040-638: The overthrow of the last Tokugawa shōgun, Yoshinobu , in 1867. After 265 years, the Pax Tokugawa came to an end. In May 1868, Edo castle was handed to the Emperor-supporting forces after negotiation (the Fall of Edo ). Some forces loyal to the shogunate kept fighting, but with their loss in the Battle of Ueno on 4 July 1868, the entire city came under the control of the new government . After
20207-489: The phenomenon is especially serious in its special wards. According to the Tokyo Metropolitan Government, the annual mean temperature has increased by about 3 °C (5.4 °F) over the past 100 years. Tokyo has been cited as a "convincing example of the relationship between urban growth and climate". In 2006, Tokyo enacted the "10 Year Project for Green Tokyo" to be realized by 2016. It set
20374-462: The planned operating conditions. It was regarded as purely an electrical test of the generator, even though it involved critical unit systems. According to the existing regulations, such a test did not require approval by either the chief design authority for the reactor (NIKIET) or the nuclear safety regulator. The test program called for disabling the emergency core cooling system , a passive/active system of core cooling intended to provide water to
20541-576: The population of Tokyo dwindled from 6,700,000 to less than 2,800,000, as soldiers were sent to the front and children were evacuated. After the war, Tokyo became the base from which the Allied Occupation Forces , under Douglas MacArthur , an American general, administered Japan for six years. The original rebuilding plan of Tokyo was based on a plan modelled after the Metropolitan Green Belt of London , devised in
20708-488: The positive scram effect would be important would never occur. However, they did appear in almost every detail in the course of the actions leading to the Chernobyl accident." A few seconds into the scram, a power spike occurred, and the core overheated, causing some of the fuel rods to fracture. Some have speculated that this also blocked the control rod columns, jamming them at one-third insertion. Within three seconds
20875-866: The public on limited occasions. Aristocratic residences today open to the public include the Marquess Maeda residence in Komaba , the Baron Iwasaki residence in Ikenohata and the Baron Furukawa residence in Nishigahara. The Great Kanto Earthquake in 1923 ushered in an era of concrete architecture. Surviving reinforced concrete buildings from this era include the Meiji Insurance Headquarters (completed in 1934),
21042-419: The radiation levels were somewhere above 0.001 R/s (3.6 R/h), while the true levels were vastly higher in some areas. Because of the inaccurate low readings, the reactor crew chief Aleksandr Akimov assumed that the reactor was intact. The evidence of pieces of graphite and reactor fuel lying around the building was ignored, and the readings of another dosimeter brought in by 04:30 were dismissed under
21209-410: The reaction rate in the lower part of the core. This behaviour was discovered when the initial insertion of control rods in another RBMK reactor at Ignalina Nuclear Power Plant in 1983 induced a power spike. Procedural countermeasures were not implemented in response to Ignalina. The IAEA investigative report INSAG-7 later stated, "Apparently, there was a widespread view that the conditions under which
21376-431: The reactor building. As a result of the damage to the building, an airflow through the core was established by the core's high temperature. The air ignited the hot graphite and started a graphite fire. After the larger explosion, several employees at the power station went outside to get a clearer view of the extent of the damage. One such survivor, Alexander Yuvchenko , said that once he stepped out and looked up towards
21543-450: The reactor fell below the required value of 15. This was not apparent to the operators, because the RBMK did not have any instruments capable of calculating the inserted rod worth in real time. The combined effect of these various actions was an extremely unstable reactor configuration. Nearly all of the 211 control rods had been extracted, and excessively high coolant flow rates meant that the water had less time to cool between trips through
21710-414: The reactor hall, he saw a "very beautiful" laser-like beam of blue light caused by the ionized-air glow that appeared to be "flooding up into infinity". There were initially several hypotheses about the nature of the second, larger explosion. One view was that the second explosion was caused by the combustion of hydrogen , which had been produced either by the overheated steam- zirconium reaction or by
21877-404: The reactor immediately, but chief engineer Nikolai Fomin would not allow this. The operators were given respirators and potassium iodide tablets and told to continue working. At 05:00, Bagdasarov made his own decision to shut down the reactor, which was confirmed in writing by Dyatlov and Station Shift Supervisor Rogozhkin. Shortly after the accident, firefighters arrived to try to extinguish
22044-451: The reactor output rose above 530 MW. Instruments did not register the subsequent course of events; it was reconstructed through mathematical simulation. The power spike would have caused an increase in fuel temperature and steam buildup, leading to a rapid increase in steam pressure . This caused the fuel cladding to fail, releasing the fuel elements into the coolant and rupturing the channels in which these elements were located. As
22211-536: The reactor shuts down. Continued coolant circulation is essential to prevent core overheating or a core meltdown . RBMK reactors, like those at Chernobyl, use water as a coolant, circulated by electrically driven pumps. Reactor No. 4 had 1,661 individual fuel channels, requiring over 12 million US gallons (45 million litres) per hour for the entire reactor. In case of a total power loss, each of Chernobyl's reactors had three backup diesel generators , but they took 60–75 seconds to reach full load and generate
22378-442: The reactor. That is, when a control rod was at maximum extraction, a neutron-moderating graphite extension was centered in the core with 1.25 metres (4.1 ft) columns of water above and below it. Consequently, injecting a control rod downward into the reactor in a scram initially displaced neutron-absorbing water in the lower portion of the reactor with neutron-moderating graphite. Thus, an emergency scram could initially increase
22545-514: The reason why the button was pressed when it was is not certain, as only the deceased Akimov and Toptunov made that decision, though the atmosphere in the control room was calm, according to eyewitnesses. The RBMK designers claim the button had to have been pressed only after the reactor already began to self-destruct. When the AZ-5 button was pressed, the insertion of control rods into the reactor core began. The control rod insertion mechanism moved
22712-553: The resignation of her predecessor, Yoichi Masuzoe . She was re-elected in 2020 and in 2024. The legislature of the Metropolis is called the Metropolitan Assembly , and it has one house with 127 seats. The assembly is responsible for enacting and amending prefectural ordinances, approving the budget (8.5 trillion yen in fiscal 2024), and voting on important administrative appointments made by the governor, including
22879-473: The rod configuration was still within its normal operating limit, with Operational Reactivity Margin (ORM) equivalent to having more than 15 rods inserted. Over the next twenty minutes, reactor power would be increased further to 200 MW. The operation of the reactor at the low power level was accompanied by unstable core temperatures and coolant flow, and possibly by instability of neutron flux . The control room received repeated emergency signals regarding
23046-452: The rods at 0.4 metres per second (1.3 ft/s), so that the rods took 18 to 20 seconds to travel the full height of the core , about 7 metres (23 ft). A bigger problem was the design of the RBMK control rods , each of which had a graphite neutron moderator section attached to its end to boost reactor output by displacing water when the control rod section had been fully withdrawn from
23213-478: The rotational momentum of the reactor's steam turbine could be used to generate the required electrical power to operate the ECCS via the feedwater pumps. The turbine's speed would run down as energy was taken from it, but analysis indicated that there might be sufficient energy to provide electrical power to run the coolant pumps for 45 seconds. This would not quite bridge the gap between an external power failure and
23380-505: The shipbuilding industry, and the protection of safety in the Strait of Malacca —vital to Japan's national security, due to the fact that more than 80 percent of her oil passes this way. In the field of public welfare , the foundation pursued such youth-oriented initiatives as the building of sports facilities, the building of day care centers and the promotion of traffic safety education. In addition, it began donating mobile clinics and blood-mobiles, as well as constructing blood banks around
23547-578: The son of the foundation's founder, Ryoichi Sasakawa. In 1962, The Nippon Foundation was established as the Japan Shipbuilding Industry Foundation under the auspices of the Japanese Motorboat Racing Law. The law and the foundation were initiatives of Ryoichi Sasakawa who, as chair, used them to both help rebuild the Japanese shipbuilding sector, and to conduct philanthropic activities around
23714-547: The spread of radioactive contamination and provided radiological protection for the crews of the undamaged reactors. In 2016–2018, the Chernobyl New Safe Confinement was constructed around the old sarcophagus to enable the removal of the reactor debris, with clean-up scheduled for completion by 2065. In nuclear reactor operation, most heat is generated by nuclear fission , but over 6% comes from radioactive decay heat, which continues after
23881-418: The test was conducted a third time but also yielded no results due to a problem with the recording equipment. The test procedure was to be run again in 1986 and was scheduled to take place during a controlled power-down of reactor No. 4, which was preparatory to a planned maintenance outage. A test procedure had been written, but the authors were not aware of the unusual RBMK-1000 reactor behaviour under
24048-429: The test, two additional main circulating pumps were activated at 01:05. The increased coolant flow lowered the overall core temperature and reduced the existing steam voids in the core. Because water absorbs neutrons better than steam, the neutron flux and reactivity decreased. The operators responded by removing more manual control rods to maintain power. It was around this time that the number of control rods inserted in
24215-434: The thousands of flights needed to cover reactor No. 4 in this attempt to seal off radiation. From eyewitness accounts of the firefighters involved before they died, one described his experience of the radiation as "tasting like metal", and feeling a sensation similar to pins and needles all over his face. This is consistent with the description given by Louis Slotin , a Manhattan Project physicist who died days after
24382-486: The time the Allied occupation of Japan ended in 1952, Tokyo's focus shifted from rebuilding to developing beyond its pre-war stature. From the 1950s onwards, Tokyo's Metro and railway network saw significant expansion, culminating in the launch of the world's first dedicated high-speed railway line, the Shinkansen , between Tokyo and Osaka in 1964. The same year saw the development of other transport infrastructure such as
24549-514: The total to 700,000. As of 2014 , roadside trees in Tokyo have increased to 950,000, and a further 300 ha (740 acres) of green space has been added. Tokyo is the seat of all three branches of government : the legislature ( National Diet ), the executive ( Cabinet led by the Prime Minister ), and the judiciary ( Supreme Court of Japan ), as well as the Emperor of Japan , the head of state. Most government ministries are concentrated in
24716-462: The vice governors. Its members are also elected on a four-year cycle. Since the completion of the Great Mergers of Heisei in 2001, Tokyo consists of 62 municipalities : 23 special wards , 26 cities , 5 towns and 8 villages . All municipalities in Japan have a directly elected mayor and a directly elected assembly, each elected on independent four-year cycles. The 23 Special Wards cover
24883-441: The wind blows north-east it could send volcanic ash to Tokyo metropolis. According to the government, less than a millimeter of the volcanic ash from a Mount Fuji eruption could cause power grid problems such as blackouts and stop trains in the Tokyo metropolitan area. A mixture of ash with rain could stick to cellphone antennas, power lines and cause temporary power outages. The affected areas would need to be evacuated. Tokyo
25050-401: The world, in an effort to standardize both the level of education and the materials used. The past years have seen the foundation continue to build on its work of the first four decades, working in the maritime, welfare and international cooperation fields. Since its origins, the foundation has been interested in aiding the nation's shipbuilding and maritime efforts, leading it to support both
25217-430: The world. This system of using gambling revenue to provide aid to needy sectors was a novel one in Japan at that time, and came under intense scrutiny. In response, the foundation strove for transparency in conducting its activities, making its records publicly accessible from its earliest days. Initiatives pursued in this period include research for the development of super tankers and their engines, direct support for
25384-564: Was English (209 residents), followed by American (182) and Chinese nationals (137). Chernobyl disaster The Chernobyl disaster began on 26 April 1986 with the explosion of the No. 4 reactor of the Chernobyl Nuclear Power Plant near the city of Pripyat in northern Ukraine, near the Belarus border in the Soviet Union . It is one of only two nuclear energy accidents rated at
25551-871: Was a leading figure in this movement, and his extant works in Tokyo include Tsukiji Hongan-ji (1934). The Imperial Crown Style , which often features Japanese-style roofs on top of elevated concrete structures, was adopted for the Tokyo National Museum in Ueno and the Kudan Hall in Kudanminami . Since the 30-metre height restriction was lifted in the 1960s, Tokyo's most dense areas have been dominated by skyscrapers. As of May 2024, there are at least 184 buildings exceeding 150 metres (492 feet) in Tokyo. Apart from these, Tokyo Tower (333m) and Tokyo Sky Tree (634m) feature high-elevation observation decks;
25718-478: Was a predictable phenomenon during such a power reduction. When the reactor power had decreased to approximately 500 MW, the reactor power control was switched from local automatic regulator to the automatic regulators, to manually maintain the required power level. AR-1 then activated, removing all four of AR-1's control rods automatically, but AR-2 failed to activate due to an imbalance in its ionization chambers. In response, Toptunov reduced power to stabilize
25885-564: Was a sail system designed for modern cargo ships, and research toward a "Techno Superliner", a 1,000-ton cargo vessel that could attain speeds of up to 50 knots. On the international cooperative support front, the foundation involved itself heavily in disaster relief, sending aid to help the victims of major disasters in countries around the world, and establishing the United Nations Sasakawa Award for Disaster Relief. Health initiatives that began in this decade include
26052-622: Was above 65. In the same year, the youngest municipalities in Tokyo were Mikura-jima (average age 40.72), Chuo (41.92), and Chiyoda (42.07), while the oldest included Okutama (59.11) and Miyake (53.82). In 1889, the Home Ministry recorded 1,375,937 people in Tokyo City and a total of 1,694,292 people in Tokyo-fu . In the same year, a total of 779 foreign nationals were recorded as residing in Tokyo. The most common nationality
26219-409: Was an alternative to the more accepted explanation of a positive-feedback power excursion where the reactor disassembled itself by steam explosion. The energy released by the second explosion, which produced the majority of the damage, was estimated by Pakhomov and Dubasov to be at 40 billion joules , the equivalent of about 10 tons of TNT . Pakhomov and Dubasov's nuclear fizzle hypothesis
26386-463: Was based in Kyoto from 794 to 1868, so Edo was still not the capital of Japan. During the Edo period , the city enjoyed a prolonged period of peace known as the Pax Tokugawa , and in the presence of such peace, the shogunate adopted a stringent policy of seclusion, which helped to perpetuate the lack of any serious military threat to the city. The absence of war-inflicted devastation allowed Edo to devote
26553-539: Was completed in 2006. The MAOUDC is a 6.3 km (3.9 mi) long system of tunnels, 22 meters (72 ft) underground, with 70-meter (230 ft) tall cylindrical tanks, each tank being large enough to fit a space shuttle or the Statue of Liberty. During floods, excess water is collected from rivers and drained to the Edo River . Low-lying areas of Kōtō , Edogawa , Sumida , Katsushika , Taitō and Arakawa near
26720-470: Was examined in 2017 by Lars-Erik De Geer, Christer Persson and Henning Rodhe, who put the hypothesized fizzle event as the more probable cause of the first explosion. Both analyses argue that the nuclear fizzle event, whether producing the second or first explosion, consisted of a prompt chain reaction that was limited to a small portion of the reactor core, since self-disassembly occurs rapidly in fizzle events. Contrary to safety regulations, bitumen ,
26887-420: Was left disabled. This system had to be disconnected via a manual isolating slide valve, which in practice meant that two or three people spent the whole shift manually turning sailboat-helm-sized valve wheels. The system had no influence on the disaster, but allowing the reactor to run for 11 hours outside of the test without emergency protection was indicative of a general lack of safety culture. At 23:04,
27054-481: Was no water left in the trucks. Misha filled a cistern and we aimed the water at the top. Then those boys who died went up to the roof—Vashchik, Kolya and others, and Volodya Pravik ... They went up the ladder ... and I never saw them again. Anatoli Zakharov, a fireman stationed in Chernobyl, offered a different description in 2008: "I remember joking to the others, 'There must be an incredible amount of radiation here. We'll be lucky if we're all still alive in
27221-453: Was now very sensitive to the regenerative effect of steam voids on reactor power. At 01:23:04, the test began. Four of the eight main circulating pumps (MCP) were to be powered by voltage from the coasting turbine, while the remaining four pumps received electrical power from the grid as normal. The steam to the turbines was shut off, beginning a run-down of the turbine generator. The diesel generators started and sequentially picked up loads;
27388-409: Was present to conduct the electrical test once the correct conditions were reached. As planned, a gradual reduction in the output of the power unit began at 01:06 on 25 April, and the power level had reached 50% of its nominal 3,200 MW thermal level by the beginning of the day shift. The day shift was scheduled to perform the test at 14:15. Preparations for the test were carried out, including
27555-486: Was said to have been abandoned and in tatters when he moved there, and ruled the region from there. When he became shōgun , the de facto ruler of the country, in 1603, the whole country came to be ruled from Edo. While the Tokugawa shogunate ruled the country in practice, the Imperial House of Japan was still the de jure ruler, and the title of shōgun was granted by the Emperor as a formality. The Imperial House
27722-427: Was wrapping-up. The scram was started when the AZ-5 button of the reactor emergency protection system was pressed: this engaged the drive mechanism on all control rods to fully insert them, including the manual control rods that had been withdrawn earlier. The personnel had intended to shut down using the AZ-5 button in preparation for scheduled maintenance and the scram preceded the sharp increase in power. However,
27889-407: Was −9.2 °C (15.4 °F) on January 13, 1876. The record high was 39.5 °C (103.1 °F) on July 20, 2004. The record highest low temperature is 30.3 °C (86.5 °F), on August 12, 2013, making Tokyo one of only seven observation sites in Japan that have recorded a low temperature over 30 °C (86.0 °F). Annual rainfall averages nearly 1,600 millimeters (63.0 in), with
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