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108-430: The plant is on a site of 1.45 km (358 acres), employs 277 workers, and indirectly employs 790. The reactors are of the 3-loop M type pressurized water reactor , built by Mitsubishi Heavy Industries . Sendai has two nuclear reactors, Sendai-1 and Sendai-2. Both are pressurized water reactors that make 890 MW of power with a core tonnage of 72 tons of uranium dioxide . Sendai-1 was commissioned on July 4, 1984, at

216-442: A (partially) closed nuclear fuel cycle . Water is a nontoxic, transparent, chemically unreactive (by comparison with e.g. NaK ) coolant that is liquid at room temperature which makes visual inspection and maintenance easier. It is also easy and cheap to obtain unlike heavy water or even nuclear graphite . Compared to reactors operating on natural uranium , PWRs can achieve a relatively high burnup . A typical PWR will exchange

324-479: A CANDU reactor or any other heavy water reactor when ordinary light water is supplied to the reactor as an emergency coolant. Depending on burnup , boric acid or another neutron poison will have to be added to emergency coolant to avoid a criticality accident . PWRs are designed to be maintained in an undermoderated state, meaning that there is room for increased water volume or density to further increase moderation, because if moderation were near saturation, then

432-446: A Japanese court rejected a complaint against the restart. On May 28, 2015, The Nuclear Regulation Authority approved the station's emergency plans, which was the last regulatory hurdle remaining before restarts could happen. Owner Kyushu Electric Power Company then had all approvals necessary for restart. On July 7, 2015, fuel loading of Sendai unit #1 began. The NRA completed its pre-operational examinations and gave Kyushu Electric Company

540-465: A PWR cannot exceed a temperature of 647 K (374 °C; 705 °F) or a pressure of 22.064 MPa (3200 psi or 218 atm), because those are the critical point of water. Supercritical water reactors are (as of 2022) only a proposed concept in which the coolant would never leave the supercritical state. However, as this requires even higher pressures than a PWR and can cause issues of corrosion, so far no such reactor has been built. Pressure in

648-405: A PWR design. Nuclear fuel in the reactor pressure vessel is engaged in a controlled fission chain reaction , which produces heat, heating the water in the primary coolant loop by thermal conduction through the fuel cladding. The hot primary coolant is pumped into a heat exchanger called the steam generator , where it flows through several thousand small tubes. Heat is transferred through

756-475: A PWR is not suitable for most industrial applications as those require temperatures in excess of 400 °C (752 °F). Radiolysis and certain accident scenarios which involve interactions between hot steam and zircalloy cladding can produce hydrogen from the cooling water leading to hydrogen explosions as a potential accident scenario. During the Fukushima nuclear accident a hydrogen explosion damaging

864-459: A PWR. It can, however, be used in a CANDU with only minimal reprocessing in a process called "DUPIC" - Direct Use of spent PWR fuel in CANDU. Thermal efficiency , while better than for boiling water reactors , cannot achieve the values of reactors with higher operating temperatures such as those cooled with high temperature gases, liquid metals or molten salts. Similarly process heat drawn from

972-592: A Special Bulletin issued on July 17, 2014 by The Institute of Energy Economics, Japan, in June 2013 the Japanese Nuclear Regulation Authority (NRA) created new stricter safety standards for all Japanese nuclear power plants. Tests on 19 reactors at 12 nuclear power plants based on the new standards began the following month and were expected to take six months, but took longer on account of their strictness. The two-reactor Sendai plant

1080-446: A chance that people might not be able to live in the capital zone including Tokyo and would have to evacuate, and that he was haunted by the specter of an even bigger nuclear crisis forcing tens of millions of people to flee Tokyo and threatening the nation's existence. "If things had reached that level, not only would the public have had to face hardships but Japan's very existence would have been in peril". That convinced Kan to "declare

1188-851: A cost of 278.7 billion yen, and Sendai-2 was commissioned on November 28, 1985, at a cost of 228.7 billion yen. On 14 December 2011 the Kyushu Electric Power Company published the outcome of the primary safety assessments or "stress-tests" for three of its suspended nuclear reactors: two of them located at the Sendai Nuclear Power Plant in Kagoshima Prefecture, the third at was located the Genkai Nuclear Power Plant in Saga Prefecture . The reports were sent to

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1296-406: A debt bill and the renewable energy bill as final conditions, Kan expected "to see his successor in office [within the] week, according to a Kyodo news report, which cited cabinet ministers". At the same time, Seiji Maehara , who had supported Kan in 2010, was reported to have announced his intention to run to succeed Kan. Maehara was seen as the potential DPJ candidate most popular with the voters at

1404-590: A decades-old Japanese government drive to build more nuclear power plants in the country. "We must scrap the plan to have nuclear power contribute 53 percent (of electricity supply) by 2030 and reduce the degree of reliance on nuclear power," Kan told a government panel. Kan said Japan should abandon plans to build 14 new reactors by 2030. He wants to "pass a bill to promote renewable energy and questioned whether private companies should be running atomic plants". In August, Kan removed three of Japan's top nuclear energy officials in effort to break ties between government and

1512-656: A given temperature set by the position of the control rods. In contrast, the Soviet RBMK reactor design used at Chernobyl, which uses graphite instead of water as the moderator and uses boiling water as the coolant, has a large positive thermal coefficient of reactivity. This means reactivity and heat generation increases when coolant and fuel temperatures increase, which makes the RBMK design less stable than pressurized water reactors at high operating temperature. In addition to its property of slowing down neutrons when serving as

1620-444: A heavy pressure vessel and hence increases construction costs. The higher pressure can increase the consequences of a loss-of-coolant accident . The reactor pressure vessel is manufactured from ductile steel but, as the plant is operated, neutron flux from the reactor causes this steel to become less ductile. Eventually the ductility of the steel will reach limits determined by the applicable boiler and pressure vessel standards, and

1728-402: A licensed benrishi (patent agent/attorney) in 1971. After graduating from college, Kan worked at a patent office for four years. He actively engaged in civic grassroots movements for years and also served on election campaign staff for Fusae Ichikawa , a women's rights activist. After having lost in the 1976 and 1979 general elections and 1977 Upper House election , Kan achieved

1836-426: A moderator). The pressure in the primary coolant loop is typically 15–16 megapascals (150–160  bar ), which is notably higher than in other nuclear reactors , and nearly twice that of a boiling water reactor (BWR). As an effect of this, only localized boiling occurs and steam will recondense promptly in the bulk fluid. By contrast, in a boiling water reactor the primary coolant is designed to boil. Light water

1944-423: A moderator, water also has a property of absorbing neutrons, albeit to a lesser degree. When the coolant water temperature increases, the boiling increases, which creates voids. Thus there is less water to absorb thermal neutrons that have already been slowed by the graphite moderator, causing an increase in reactivity. This property is called the void coefficient of reactivity, and in an RBMK reactor like Chernobyl,

2052-422: A panel entitled “Fukushima: Ongoing Lessons for California” [1] next to Nuclear Regulatory Commission chair Gregory Jaczko , former NRC Commissioner Peter A. Bradford , and nuclear engineer Arnie Gundersen , where they discussed nuclear power's risks. In his concluding statement Prime Minister Kan stated: "After Fukushima, my whole mindset about nuclear power has changed 180 degrees... I began to think there

2160-562: A pressurized water reactor (although the first power plant connected to the grid was at Obninsk , USSR), on insistence from Admiral Hyman G. Rickover that a viable commercial plant would include none of the "crazy thermodynamic cycles that everyone else wants to build". The United States Army Nuclear Power Program operated pressurized water reactors from 1954 to 1974. Three Mile Island Nuclear Generating Station initially operated two pressurized water reactor plants, TMI-1 and TMI-2. The partial meltdown of TMI-2 in 1979 essentially ended

2268-542: A quarter to a third of its fuel load every 18-24 months and have maintenance and inspection, that requires the reactor to be shut down, scheduled for this window. While more uranium ore is consumed per unit of electricity produced than in a natural uranium fueled reactor, the amount of spent fuel is less with the balance being depleted uranium whose radiological danger is lower than that of natural uranium. The coolant water must be highly pressurized to remain liquid at high temperatures. This requires high strength piping and

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2376-469: A reduction in density of the moderator/coolant could reduce neutron absorption significantly while reducing moderation only slightly, making the void coefficient positive. Also, light water is actually a somewhat stronger moderator of neutrons than heavy water, though heavy water's neutron absorption is much lower. Because of these two facts, light water reactors have a relatively small moderator volume and therefore have compact cores. One next generation design,

2484-686: A relationship with the Tokyo-dwelling Kan after entering Tsuda College . As the two are first cousins , the engagement was met with parental opposition. They have two sons, Gentarō and Shinjirō. Gentarō is a social activist and ran unsucessfully for the House of Representatives in 2003 and 2005 . He later served as political secretary to his father and was elected to the Musashino City Council in December 2023. Shinjiro

2592-607: A seat in the lower house in 1980 as a member of the Socialist Democratic Federation . He Later joined the New Party Sakigake . When the party was in coalition with the LDP, Kan was appointed Minister of Health and Welfare in the cabinet of Prime Minister Ryutaro Hashimoto in 1996. While serving in this position he gained national popularity for admitting the government's responsibility for

2700-567: A secondary system where steam is generated. The steam then drives turbines, which spin an electric generator. In contrast to a boiling water reactor (BWR), pressure in the primary coolant loop prevents the water from boiling within the reactor. All light-water reactors use ordinary water as both coolant and neutron moderator . Most use anywhere from two to four vertically mounted steam generators; VVER reactors use horizontal steam generators. PWRs were originally designed to serve as nuclear marine propulsion for nuclear submarines and were used in

2808-420: A shaft used for propulsion . Direct mechanical action by expansion of the steam can be used for a steam-powered aircraft catapult or similar applications. District heating by the steam is used in some countries and direct heating is applied to internal plant applications. Two things are characteristic for the pressurized water reactor (PWR) when compared with other reactor types: coolant loop separation from

2916-413: A slight edge among DPJ members of parliament, in the final vote Kan garnered the support of 206 DPJ lawmakers to Ozawa's 200. Local rank-and-file party members and activists overwhelmingly supported Kan, and according to opinion polls the wider Japanese public preferred Kan to Ozawa by as much as a 4:1 ratio. After the leadership challenge, Kan reshuffled his cabinet, which left many prominent members of

3024-486: A specific dollar-yen level as optimal to help exporters and stimulate the economy: "There are a lot of voices in the business world saying that (the dollar) around ¥95 is appropriate in terms of trade". Hatoyama appeared to rebuke Kan. "When it comes to foreign exchange, stability is desirable and rapid moves are undesirable. The government basically shouldn't comment on foreign exchange," he told reporters. On 2 June 2010, Yukio Hatoyama announced his intention to resign as

3132-598: A television newscaster and media consultant, Yūko Tonomoto. After Yukio Hatoyama resigned as the leader of the Democratic Party of Japan , Kan again took over the position. In July 2003, the DPJ and the Liberal Party led by Ichirō Ozawa agreed to form a united opposition party to prepare for the general election that was anticipated to take place in the fall. During the campaign of the election of 2003 ,

3240-456: Is a veterinarian and works at an animal hospital in Nerima, Tokyo . Kan is nicknamed "Ira-Kan" (Fretful Kan") due to his reputed short temper. His hobbies were go , shogi and origami . Kan built a machine to calculate the complicated mahjong point system and applied for a patent in 1973. Kan was portrayed by Shirō Sano in the 2020 film Fukushima 50 , and by Fumiyo Kohinata in

3348-484: Is a Japanese former politician who served as Prime Minister of Japan and President of the Democratic Party of Japan (DPJ) from June 2010 to September 2011. Kan was the first Prime Minister since the resignation of Junichiro Koizumi in 2006 to serve for more than one year, with his predecessors Yukio Hatoyama , Tarō Asō , Yasuo Fukuda , and Shinzo Abe either resigning prematurely or losing an election. On 26 August 2011, Kan announced his resignation. Yoshihiko Noda

Sendai Nuclear Power Plant - Misplaced Pages Continue

3456-517: Is a type of light-water nuclear reactor . PWRs constitute the large majority of the world's nuclear power plants (with notable exceptions being the UK, Japan and Canada). In a PWR, the primary coolant ( water ) is pumped under high pressure to the reactor core where it is heated by the energy released by the fission of atoms. The heated, high pressure water then flows to a steam generator , where it transfers its thermal energy to lower pressure water of

3564-402: Is generated per unit of uranium ore even though a higher burnup can be achieved. Nuclear reprocessing can "stretch" the fuel supply of both natural uranium and enriched uranium reactors but is virtually only practiced for light water reactors operating with lightly enriched fuel as spent fuel from e.g. CANDU reactors is very low in fissile material. Because water acts as a neutron moderator, it

3672-432: Is more dense (more collisions will occur). The use of water as a moderator is an important safety feature of PWRs, as an increase in temperature may cause the water to expand, giving greater 'gaps' between the water molecules and reducing the probability of thermalization — thereby reducing the extent to which neutrons are slowed and hence reducing the reactivity in the reactor. Therefore, if reactivity increases beyond normal,

3780-401: Is not possible to build a fast-neutron reactor with a PWR design. A reduced moderation water reactor may however achieve a breeding ratio greater than unity, though this reactor design has disadvantages of its own. Spent fuel from a PWR usually has a higher content of fissile material than natural uranium. Without nuclear reprocessing , this fissile material cannot be used as fuel in

3888-491: Is not to reproduce the experience of the crisis experienced by Naoto Kan that I produced this film. The media and public opinion, manipulated by the latter, were totally hostile to the Prime Minister, accusing him of having aggravated the accident and amplified the damage. Faced with this rejection, I was plagued by anger and disgust as they led me to make this film to put things in order. The reactors’ accident could, in

3996-527: Is on an 18–24 month cycle. Approximately one third of the core is replaced each refueling, though some more modern refueling schemes may reduce refuel time to a few days and allow refueling to occur on a shorter periodicity. In PWRs reactor power can be viewed as following steam (turbine) demand due to the reactivity feedback of the temperature change caused by increased or decreased steam flow. (See: Negative temperature coefficient .) Boron and cadmium control rods are used to maintain primary system temperature at

4104-465: Is used as the primary coolant in a PWR. Water enters through the bottom of the reactor's core at about 548  K (275 °C; 527 °F) and is heated as it flows upwards through the reactor core to a temperature of about 588 K (315 °C; 599 °F). The water remains liquid despite the high temperature due to the high pressure in the primary coolant loop, usually around 155 bar (15.5  MPa 153  atm , 2,250  psi ). The water in

4212-545: The Yomiuri Shimbun and other news outlets reported as fact, and opposition leader Sadakazu Tanigaki accused the government of causing the Fukushima meltdowns. Early in the morning of 15 March, amid rumors that TEPCO intended to abandon the plant and allow a full meltdown that would potentially trigger an evacuation of the entire Kanto region, Kan ordered the establishment of a joint response headquarters between

4320-449: The Democratic Party of Japan itself did not endorse any candidate, but Kan supported Kenji Utsunomiya (leftist lawyer), who shared Kan's anti-nuclear stance. Ultimately Utsunomiya came second in the election, losing to Naoki Inose who had been vice-governor under Ishihara from 2007 to 2012, and then acting governor after Ishihara's abrupt resignation. In the 2012 general election called by Kan's successor Noda, Kan lost his seat in

4428-485: The Fukushima I Nuclear Power Plant early the next morning, and was thereafter heavily involved in efforts to effectively respond to the Fukushima nuclear accident . Venting from the Fukushima plant began on the morning of 12 March, shortly after Kan's meeting with Tokyo Electric Power Company (TEPCO) management at the plant, and that afternoon the plant suffered its first explosion. That evening, following an order from METI Minister Kaieda to begin pumping seawater into

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4536-485: The Japan Self-Defense Forces should play a more prominent role on the international stage. On 6 January 2010, he was picked by Yukio Hatoyama to be the new finance minister, assuming the post in addition to deputy prime minister. He replaced Hirohisa Fujii as finance minister. In his first news conference, Kan announced his priority was stimulating growth and took the unusual step of naming

4644-584: The Nuclear Regulation Authority (NRA) announced it would install seabed sensors to monitor the Aira Caldera 40 km from the nuclear plant, to supplement land-based monitoring. In the extremely unlikely event of signs of major volcanic activity, it would be possible to remove nuclear fuel from the reactors. In March 2020, reactor #1 was shut down again because it could not meet the deadline for anti-terrorism safety measures. It

4752-590: The Senkaku Islands . China protested the arrest, as it claims the islands as part of its sovereign territory , and demanded the unconditional release of the captain. The captain was released on 24 September, after China had cut off all ministerial-level contacts with Japan and threatened further action. The incident brought Sino-Japanese relations to its lowest point since the Koizumi administration. The Kan government intervened in mid-September to weaken

4860-659: The Shikoku Pilgrimage . Later, the Ministry of Health, Labour and Welfare spokesman apologized, saying the unpaid record was due to an administrative error. In mid-October 2005, Kan, who turned 60 in 2006, proposed the creation of a new political party to be called the "Dankai ( baby boomer ) Party". The initial intent of the party was to offer places of activity for the Japanese baby boomers – 2.7 million of whom began to retire en masse in 2007. Kan believes

4968-547: The Tokyo 18th district , but retained a seat in the diet through the proportional representation system. In the 2014 general election , Kan lost his district seat but was again elected through the proportional block. He joined the Constitutional Democratic Party of Japan along with the liberal-leaning members of the Democratic Party following the party split prior to the 2017 general election . In

5076-452: The supercritical water reactor , is even less moderated. A less moderated neutron energy spectrum does worsen the capture/fission ratio for U and especially Pu, meaning that more fissile nuclei fail to fission on neutron absorption and instead capture the neutron to become a heavier nonfissile isotope, wasting one or more neutrons and increasing accumulation of heavy transuranic actinides, some of which have long half-lives. After enrichment,

5184-531: The uranium dioxide ( UO 2 ) powder is fired in a high-temperature, sintering furnace to create hard, ceramic pellets of enriched uranium dioxide. The cylindrical pellets are then clad in a corrosion-resistant zirconium metal alloy Zircaloy which are backfilled with helium to aid heat conduction and detect leakages. Zircaloy is chosen because of its mechanical properties and its low absorption cross section. The finished fuel rods are grouped in fuel assemblies, called fuel bundles, that are then used to build

5292-410: The 2023 Documentary Film SOS: The San Onofre Syndrome directed by James Heddle, Mary Beth Brangan and Morgan Peterson. On a recent interview producer Mary Beth Brangan stated that it was the Fukushima accident what set her and her life partner James Heddle into the making of that film. The film documents a very special visit prime minister Naoto Kan paid on June 4th, 2013 to San Diego to participate in

5400-453: The 2023 Netflix series The Days (in which his name was changed to Shinji Azuma). Both works portray Kan's role in the Fukushima crisis from a highly critical perspective. The docu-drama The Seal of the Sun (2016, 90 min.), directed by Futoshi Sato, produced by Kaori Otsuka and executive produced by Tamiyoshi Tachibana, shows how the Prime Minister's office and the field struggled following

5508-430: The DPJ called the election as the choice of the government between the ruling LDP-bloc and the DPJ, with Kan being presented as the alternative candidate to then Prime Minister Junichiro Koizumi . His face was used as the trademark of the campaign against the LDP. However, in 2004 Kan was accused of unpaid annuities and again resigned the position of leader. On 10 May 2004, he officially announced his resignation and made

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5616-711: The DPJ lost its majority and was forced to work with smaller, unaffiliated parties (such as Your Party , the JCP , and the SDP ) in order to secure passage of bills in the House of Councillors. In August, Kan apologised to the Republic of Korea on the 100th anniversary of the Japan–Korea Annexation Treaty . Ozawa challenged Kan's leadership of the DPJ in September. Although it was initially believed that Ozawa had

5724-566: The Japanese Nuclear and Industrial Safety Agency . The papers were also sent to the local authorities of the prefectures where the plants were located, because the reactors are not allowed to be restarted without their consent. According to the test, the reactors could withstand a seismic shock of 945 to 1,020 gals and tsunami-waves of a height of 13 to 15 meters. The power company asked its customers to reduce their power-consumption by at least 5% after 26 December, because at 25 December

5832-632: The NRA declared that the plant was safe to be operated. Actual operation was originally expected by the end of 2014, following approval of local authorities, however, local and national groups and NGO S opposed the planned restart of the Sendai nuclear plants. John Large of the London-based consulting Engineers Large & Associates, provided opinion and evidence in an ongoing civil action in Japan contesting

5940-613: The US, they were originally designed at the Oak Ridge National Laboratory for use as a nuclear submarine power plant with a fully operational submarine power plant located at the Idaho National Laboratory . Follow-on work was conducted by Westinghouse Bettis Atomic Power Laboratory . The first purely commercial nuclear power plant at Shippingport Atomic Power Station was originally designed as

6048-491: The age of 63, won the leadership of the DPJ with 291 votes to 129, defeating a relatively unknown Ozawa-backed legislator Shinji Tarutoko , 50, who was leading the environmental policy committee in the lower house of the Diet. Subsequently, on 4 June, Kan was designated prime minister by the Diet. On 8 June, Emperor Akihito formally appointed Kan as the 94th Prime Minister , and the 29th postwar prime minister. His cabinet

6156-467: The assumption of maximum tsunami height from 4 meters to 5 meters. Furthermore, a 10-meter-high protection wall was built. Design standards were further enhanced to take into account all other natural disasters, in particular volcanic eruptions and tornadoes, along with plans to address terrorist attacks. Further details on the tests may be found in the Special Bulletin. On 10 September 2014

6264-402: The atomic industry. When interviewed in 2012, after resigning as prime minister, Kan said the Fukushima accident made it clear to him that "Japan needs to dramatically reduce its dependence on nuclear power , which supplied 30 percent of its electricity before the crisis, and has turned him into a believer of renewable energy." He said that at one point Japan faced a situation where there was

6372-406: The containment building was a major concern, though the reactors at the plant were BWRs , which owing to the steam at the top of the pressure vessel by design carry a greater risk of this happening. Some reactors contain catalytic recombiners which let the hydrogen react with ambient oxygen in a non-explosive fashion. Naoto Kan Naoto Kan ( 菅 直人 , Kan Naoto , born 10 October 1946)

6480-426: The core of the reactor. A typical PWR has fuel assemblies of 200 to 300 rods each, and a large reactor would have about 150–250 such assemblies with 80–100 tons of uranium in all. Generally, the fuel bundles consist of fuel rods bundled 14 × 14 to 17 × 17. A PWR produces on the order of 900 to 1,600 MW e . PWR fuel bundles are about 4 meters in length. Refuelings for most commercial PWRs

6588-409: The country continued to suffer from the earthquake, tsunami, and nuclear crises of spring 2011. One year into his premiership on 2 June 2011, Kan proposed his resignation, hours before the Diet put forward a vote of no-confidence. The motion was defeated by 293 to 152, bolstering the Prime Minister's position. In July 2011, Kan said that Japan must reduce its dependence on nuclear energy, breaking with

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6696-544: The desired point. In order to decrease power, the operator throttles shut turbine inlet valves. This would result in less steam being drawn from the steam generators. This results in the primary loop increasing in temperature. The higher temperature causes the density of the primary reactor coolant water to decrease, allowing higher neutron speeds, thus less fission and decreased power output. This decrease of power will eventually result in primary system temperature returning to its previous steady-state value. The operator can control

6804-418: The disaster struck; he wore blue coveralls instead of a suit until the end of March. Kan took an increasingly anti-nuclear stance in the months following the Fukushima disaster. In May, he ordered that the aging Hamaoka Nuclear Power Plant be closed over earthquake and tsunami fears, and he said he would freeze plans to build new reactors. Despite falling popularity, Kan rejected calls to step down while

6912-629: The election, he regained his district seat, defeating the LDP incumbent Masatada Tsuchiya with a margin of 1,046 votes. In 2023, Kan stated publicly he would not run for a seat in the House of Representatives again. He further said that he would "still probably be involved in politics someway". His term ended when the House was dissolved in October 2024 . Kan married his wife Nobuko in 1970. Nobuko, born in Okayama Prefecture, entered

7020-399: The fast fission neutrons to be slowed (a process called moderation or thermalizing) in order to interact with the nuclear fuel and sustain the chain reaction. In PWRs the coolant water is used as a moderator by letting the neutrons undergo multiple collisions with light hydrogen atoms in the water, losing speed in the process. This "moderating" of neutrons will happen more often when the water

7128-418: The five days after the Fukushima nuclear accident. The film delves into the 3.11 Tohoku earthquake/Fukushima disaster from Prime Minister Naoto Kan and his cabinet's perspective. In this interview, executive producer Tachibana discusses why he created the film: At the time, I was simply a friend, one of his cadets in politics. It was only after the earthquake that I became a real member of his support group. It

7236-559: The flawed RBMK control rods design. These design flaws, in addition to operator errors that pushed the reactor to its limits, are generally seen as the causes of the Chernobyl disaster . The Canadian CANDU heavy water reactor design have a slight positive void coefficient, these reactors mitigate this issues with a number of built-in advanced passive safety systems not found in the Soviet RBMK design. No criticality could occur in

7344-479: The government and TEPCO, and personally traveled to TEPCO headquarters on half an hour's notice. While this move initially antagonized TEPCO, it was later positively evaluated as improving communications between the plant operator and government agencies such as the Self-Defense Forces and Tokyo Fire Department. Kan slept in the Prime Minister's Office and did not return home for an entire week after

7452-427: The green light to place fuel inside the reactor vessel. Sendai's reactor no. 1 was restarted on August 11, 2015. Naoto Kan , former Prime Minister (2010–2011), was among the protesters who were demonstrating in front of the Sendai plant when the reactor was restarted. On November 1, 2015, followed reactor n.2, at full-capacity the same day, with its thermal output reaching the maximum level, about two weeks after it

7560-578: The growth in new construction of nuclear power plants in the United States for two decades. Watts Bar unit 2 (a Westinghouse 4-loop PWR) came online in 2016, becoming the first new nuclear reactor in the United States since 1996. The pressurized water reactor has several new Generation III reactor evolutionary designs: the AP1000 , VVER-1200, ACPR1000+, APR1400, Hualong One , IPWR-900 and EPR . The first AP1000 and EPR reactors were connected to

7668-460: The heaters or emptying the pressurizer. Pressure transients in the primary coolant system manifest as temperature transients in the pressurizer and are controlled through the use of automatic heaters and water spray, which raise and lower pressurizer temperature, respectively. The coolant is pumped around the primary circuit by powerful pumps. These pumps have a rate of ~100,000 gallons of coolant per minute. After picking up heat as it passes through

7776-409: The leader of the Democratic Party of Japan (DPJ) and as prime minister, also saying that he had urged his backer in the party, Ichirō Ozawa , to resign as secretary general. The Cabinet resigned en masse on 4 June. Foreign Minister Katsuya Okada and Land and Transport Minister Seiji Maehara , though once considered to be possible successors to Hatoyama, announced their support for Kan. Kan, at

7884-518: The most deployed type of reactor globally, allowing for a wide range of suppliers of new plants and parts for existing plants. Due to long experience with their operation they are the closest thing to mature technology that exists in nuclear energy. PWRs - depending on type - can be fueled with MOX-fuel and/or the Russian Remix Fuel (which has a lower Pu and a higher U content than "regular" U/Pu MOX-fuel) allowing for

7992-445: The need for Japan to end its reliance on atomic power and promote renewable sources of energy such solar [sic] that have long taken a back seat in the resource-poor country's energy mix". He told a parliamentary investigation in 2012 that the nuclear industry had "shown no remorse" for the disaster, and was trying to push Japan back to nuclear power. Kan announced his intention to resign on 10 August 2011. On 26 August, with passage of

8100-430: The neutron activity correspondingly. An entire control system involving high pressure pumps (usually called the charging and letdown system) is required to remove water from the high pressure primary loop and re-inject the water back in with differing concentrations of boric acid. The reactor control rods, inserted through the reactor vessel head directly into the fuel bundles, are moved for the following reasons: to start up

8208-480: The nucleus of a boron-10 atom which subsequently splits into a lithium-7 and tritium atom. Pressurized water reactors annually emit several hundred curies of tritium to the environment as part of normal operation. Natural uranium is only 0.7% uranium-235, the isotope necessary for thermal reactors. This makes it necessary to enrich the uranium fuel, which significantly increases the costs of fuel production. Compared to reactors operating on natural uranium, less energy

8316-630: The number 4 reactor in Genkai would be taken out of operation for regular check-ups. Nuclear power generation did account for about 40 percent of the total output of the company, according to company official Akira Nakamura. He said that restarting reactors was crucial for them, and that the company will do all it can do to win back public-trust. However, Hideo Kishimoto, the mayor of Genkai said that it would be difficult to resume operations. He asked Kyushu Electric to disclose their practices in full, besides their efforts to prevent future accidents. According to

8424-544: The original design of the second commercial power plant at Shippingport Atomic Power Station . PWRs currently operating in the United States are considered Generation II reactors . Russia's VVER reactors are similar to US PWRs, but the VVER-1200 is not considered Generation II (see below). France operates many PWRs to generate the bulk of its electricity. Several hundred PWRs are used for marine propulsion in aircraft carriers , nuclear submarines and ice breakers . In

8532-440: The plant for emergency cooling purposes, Kan expressed concern that the seawater injection plan may lead to re-criticality, in response to which TEPCO directed plant manager Masao Yoshida to stop pumping (an order which Yoshida tacitly ignored). After further briefings on the issue, Kan directed pumping to continue later that evening. Several weeks later, Shinzo Abe circulated information that Kan had ordered pumping to stop, which

8640-667: The power grid in China in 2018. In 2020, NuScale Power became the first U.S. company to receive regulatory approval from the Nuclear Regulatory Commission for a small modular reactor with a modified PWR design. Also in 2020, the Energy Impact Center introduced the OPEN100 project, which published open-source blueprints for the construction of a 100 MW electric nuclear power plant with

8748-432: The pressure drop across the turbine, and hence the energy extracted from the steam, is maximized. Before being fed into the steam generator, the condensed steam (referred to as feedwater) is sometimes preheated in order to minimize thermal shock. The steam generated has other uses besides power generation. In nuclear ships and submarines, the steam is fed through a steam turbine connected to a set of speed reduction gears to

8856-518: The pressure vessel must be repaired or replaced. This might not be practical or economic, and so determines the life of the plant. Additional high pressure components such as reactor coolant pumps, pressurizer, and steam generators are also needed. This also increases the capital cost and complexity of a PWR power plant. The high temperature water coolant with boric acid dissolved in it is corrosive to carbon steel (but not stainless steel ); this can cause radioactive corrosion products to circulate in

8964-419: The pressurized steam is fed through a steam turbine which drives an electrical generator connected to the electric grid for transmission. After passing through the turbine the secondary coolant (water-steam mixture) is cooled down and condensed in a condenser . The condenser converts the steam to a liquid so that it can be pumped back into the steam generator, and maintains a vacuum at the turbine outlet so that

9072-414: The pressurizer temperature and the highest temperature in the reactor core) of 30 °C (54 °F). As 345 °C is the boiling point of water at 155 bar, the liquid water is at the edge of a phase change. Thermal transients in the reactor coolant system result in large swings in pressurizer liquid/steam volume, and total pressurizer volume is designed around absorbing these transients without uncovering

9180-441: The primary circuit is maintained by a pressurizer, a separate vessel that is connected to the primary circuit and partially filled with water which is heated to the saturation temperature (boiling point) for the desired pressure by submerged electrical heaters. To achieve a pressure of 155 bars (15.5 MPa), the pressurizer temperature is maintained at 345 °C (653 °F), which gives a subcooling margin (the difference between

9288-423: The primary coolant loop. This not only limits the lifetime of the reactor, but the systems that filter out the corrosion products and adjust the boric acid concentration add significantly to the overall cost of the reactor and to radiation exposure. In one instance, this has resulted in severe corrosion to control rod drive mechanisms when the boric acid solution leaked through the seal between the mechanism itself and

9396-406: The primary system. Due to the requirement to load a pressurized water reactor's primary coolant loop with boron, undesirable radioactive secondary tritium production in the water is over 25 times greater than in boiling water reactors of similar power, owing to the latter's absence of the neutron moderating element in its coolant loop. The tritium is created by the absorption of a fast neutron in

9504-582: The pro-Ozawa faction of the DPJ without important posts in the new cabinet. The cabinet reshuffle also resulted in the promotion of long-time Kan ally Yoshito Sengoku to Chief Cabinet Secretary. Sengoku was labeled by the opposition LDP as the "second" Prime Minister of the Kan cabinet. On 7 September, a Chinese fishing boat captain was arrested by the Japan Coast Guard (JCG) after his trawler had collided with JCG patrol boats in disputed waters near

9612-432: The reactor coolant and control the reactor power by adjusting the reactor coolant flow rate. PWR reactors are very stable due to their tendency to produce less power as temperatures increase; this makes the reactor easier to operate from a stability standpoint. PWR turbine cycle loop is separate from the primary loop, so the water in the secondary loop is not contaminated by radioactive materials. PWRs can passively scram

9720-455: The reactor core, the primary coolant transfers heat in a steam generator to water in a lower pressure secondary circuit, evaporating the secondary coolant to saturated steam — in most designs 6.2 MPa (60 atm, 900  psia ), 275 °C (530 °F) — for use in the steam turbine. The cooled primary coolant is then returned to the reactor vessel to be heated again. Pressurized water reactors, like all thermal reactor designs, require

9828-403: The reactor in case offsite power is lost to immediately stop the primary nuclear reaction. The control rods are held by electromagnets and fall by gravity when current is lost; full insertion safely shuts down the primary nuclear reaction. PWR technology is favoured by nations seeking to develop a nuclear navy; the compact reactors fit well in nuclear submarines and other nuclear ships. PWRs are

9936-428: The reactor, to shut down the primary nuclear reactions in the reactor, to accommodate short term transients, such as changes to load on the turbine, The control rods can also be used to compensate for nuclear poison inventory and to compensate for nuclear fuel depletion. However, these effects are more usually accommodated by altering the primary coolant boric acid concentration. In contrast, BWRs have no boron in

10044-431: The reduced moderation of neutrons will cause the chain reaction to slow down, producing less heat. This property, known as the negative temperature coefficient of reactivity, makes PWR reactors very stable. This process is referred to as 'Self-Regulating', i.e. the hotter the coolant becomes, the less reactive the plant becomes, shutting itself down slightly to compensate and vice versa. Thus the plant controls itself around

10152-567: The restart of the Sendai Nuclear Power Plant and separately Large & Associates prepared an assessment of the effectiveness of the Japanese NRA recently introduced guide for the evaluation of nuclear power plant sites with respect to the potential effects of volcanic activity, specifically aligning this to the Sendai NPP presently proposed for restart following a four-year shut down in the aftermath of Fukushima Daiichi . In April 2015,

10260-411: The spread of HIV-tainted blood in the 1980s and directly apologized to victims. His frank action was completely unprecedented and was applauded by the media and the public. In September of the same year, after having left cabinet, Kan founded the Democratic Party of Japan along with Yukio Hatoyama . In 1998, his image was affected by allegations of an affair, vigorously denied by both parties, with

10368-426: The steady state operating temperature by addition of boric acid and/or movement of control rods. Reactivity adjustment to maintain 100% power as the fuel is burned up in most commercial PWRs is normally achieved by varying the concentration of boric acid dissolved in the primary reactor coolant. Boron readily absorbs neutrons and increasing or decreasing its concentration in the reactor coolant will therefore affect

10476-427: The steam system and pressure inside the primary coolant loop. In a PWR, there are two separate coolant loops (primary and secondary), which are both filled with demineralized/deionized water. A boiling water reactor, by contrast, has only one coolant loop, while more exotic designs such as breeder reactors use substances other than water for coolant and moderator (e.g. sodium in its liquid state as coolant or graphite as

10584-449: The surging yen by buying U.S. dollars , a move which temporarily relieved Japan's exporters. The move proved popular with stock brokers, Japanese exporters, and the Japanese public. It was the first such move by a Japanese government since 2004. Later, in October, after the yen had offset the intervention and had reached a 15-year high, the Kan cabinet approved a stimulus package worth about 5.1 trillion yen ($ 62 billion) in order to weaken

10692-442: The time, but several other cabinet members joined the race, and the election of the DPJ successor was scheduled for 29 August. At that time, Yoshihiko Noda , most recently finance minister, was elected as the new DPJ leader and, as leader of the largest party in the Diet, became prime minister as well. During 16 December 2012 Tokyo gubernatorial election , called due to the resignation of incumbent Governor Shintaro Ishihara ,

10800-409: The void coefficient is positive, and fairly large, making it very hard to regulate when the reaction begins to run away. The RBMK reactors also have a flawed control rods design in which during rapid scrams, the graphite reaction enhancement tips of the rods would displace water at the bottom of the reactor and locally increase reactivity there. This is called the "positive scram effect" that is unique to

10908-414: The walls of these tubes to the lower pressure secondary coolant located on the shell side of the exchanger where the secondary coolant evaporates to pressurized steam. This transfer of heat is accomplished without mixing the two fluids to prevent the secondary coolant from becoming radioactive. Some common steam generator arrangements are u-tubes or single pass heat exchangers. In a nuclear power station,

11016-493: The worst case, have caused the evacuation of the entire population living within a radius of 250km, including Tokyo, a total of 50 million people. Naoto Kan was the only one to have guessed the extreme gravity of the accident and to have realized that we were one step away from the collapse of Japan. If he had not been Prime Minister, if the crisis had to be managed by another in his place, the country could have been completely destroyed. Naoto Kan has an important cameo appearance in

11124-465: The yen and fight deflation. In November, Kan spoke out forcefully in support of South Korea and in harsh criticism of North Korea in the wake of the latter's bombardment of Yeonpyeong , meanwhile ignoring China's public comments which had not yet included denunciation of the North. After the earthquake and tsunami in northeastern Japan on the afternoon of March 11, 2011, Kan flew by helicopter to

11232-579: Was elected as his successor . On 1 August 2012, United Nations Secretary-General Ban Ki-moon announced Kan would be one of the members of the UN high-level panel on the post-2015 development agenda. Kan was born in Ube, Yamaguchi , the eldest son of Hisao Kan, the executive director of the glass manufacturing company Central Glass. He graduated in 1970 from the Tokyo Institute of Technology and became

11340-494: Was formed later on the day. Kan's approval ratings fell in the month of June after he proposed an increase in the sales tax rate from 5% to 10%. His sales tax increase proposal was opposed by Ichirō Ozawa , amongst others in the DPJ, and the proposal was quickly scaled back by Kan. The botched sales tax increase proposal was partially blamed for the DPJ's disappointing results in the July House of Councillors election , where

11448-508: Was given priority and was approved by the NRA as meeting both its earthquake and tsunami assumptions in March 2014. An effective safety test pass certificate was issued on July 16 and the draft safety test report was opened to public comments until August 15. The basis for the approval was enhanced safety measures, in particular raising the previous assumption for the Sendai plant of 540 gal for maximum earthquake strength to 620 gal, and similarly

11556-417: Was reactivated. No major problems occurred in the process. The utility first restarted reactor n.2, removing the control rods on October, 15. The unit 1 was shut down for maintenance from October to December 2016; Kagoshima governor Satoshi Mitazono approved the restarting of the reactor despite his personal opposition to nuclear power. On 7 January 2017 unit 1 resumed commercial operation. In March 2019,

11664-570: Was the first time a reactor was shut down for this reason in Japan. After the required work was completed, the reactor was restarted in November 2020. Reactor #2 was shut down for the same reason in May 2020; it is expected to be restarted in January 2021 after installing anti-terrorism safety measures and completing maintenance. Pressurized water reactor A pressurized water reactor ( PWR )

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