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119-616: The Hokuriku Technology Museum on nuclear power is located next to the plant site. Construction of the first unit was started on July 1, 1989, and finished in three years. The reactor reached its first criticality on November 20, 1992, and went into commercial operation on July 30, 1993. Construction of the second unit was started on August 20, 2001, and finished in three years. The reactor reached its first criticality on May 26, 2005, and went into commercial operation on March 15, 2006. Both units use boiling water reactors from Hitachi. Unit 1 supplied an average of 3600 GWh of electricity to

238-449: A LBLOCA (large-break loss-of-coolant accident – a massive pipe rupture leading to catastrophic loss of coolant pressure within the reactor, considered the most threatening "design basis accident" in probabilistic risk assessment and nuclear safety and security ), which is anticipated to lead to the temporary exposure of the core; this core drying-out event is termed core "uncovery", for the core loses its heat-removing cover of coolant, in

357-545: A boiling water reactor would be feasible for use in energy production. He found that it was, after subjecting his reactors to quite strenuous tests, proving the safety principles of the BWR. Following this series of tests, GE got involved and collaborated with Argonne National Laboratory to bring this technology to market. Larger-scale tests were conducted through the late 1950s/early/mid-1960s that only partially used directly generated (primary) nuclear boiler system steam to feed

476-512: A defence in depth philosophy, which is a design philosophy that is integrated throughout construction and commissioning . A BWR is similar to a pressurized water reactor (PWR) in that the reactor will continue to produce heat even after the fission reactions have stopped, which could make a core damage incident possible. This heat is produced by the radioactive decay of fission products and materials that have been activated by neutron absorption . BWRs contain multiple safety systems for cooling

595-514: A BWR and PWR is that in a BWR, the reactor core heats water, which turns to steam and then drives a steam turbine. In a PWR, the reactor core heats water, which does not boil. This hot water then exchanges heat with a lower pressure system, which turns water into steam that drives the turbine. The BWR was developed by the Argonne National Laboratory and General Electric (GE) in the mid-1950s. The main present manufacturer

714-409: A BWR core is substantiated by a calculation that proves that 99.9% of fuel rods in a BWR core will not enter the transition to film boiling during normal operation or anticipated operational occurrences. Since the BWR is boiling water, and steam does not transfer heat as well as liquid water, MFLCPR typically occurs at the top of a fuel assembly, where steam volume is the highest. FLLHGR (FDLRX, MFLPD)

833-482: A BWR tends to balance the savings due to the simpler design and greater thermal efficiency of a BWR when compared with a PWR. Most of the radioactivity in the water is very short-lived (mostly N-16, with a 7-second half-life ), so the turbine hall can be entered soon after the reactor is shut down. BWR steam turbines employ a high-pressure turbine designed to handle saturated steam, and multiple low-pressure turbines. The high-pressure turbine receives steam directly from

952-524: A BWR: MFLCPR, FLLHGR, and APLHGR must be kept less than 1.0 during normal operation; administrative controls are in place to assure some margin of error and margin of safety to these licensed limits. Typical computer simulations divide the reactor core into 24–25 axial planes ; relevant quantities (margins, burnup, power, void history) are tracked for each "node" in the reactor core (764 fuel assemblies x 25 nodes/assembly = 19100 nodal calculations/quantity). Specifically, MFLCPR represents how close

1071-490: A PWR, where the turbine steam demand is set manually by the operators, in a BWR, the turbine valves will modulate to maintain reactor pressure at a setpoint. Under this control mode, the turbine output will automatically follow reactor power changes. When the turbine is offline or trips, the main steam bypass/dump valves will open to direct steam directly to the condenser. These bypass valves will automatically or manually modulate as necessary to maintain reactor pressure and control

1190-538: A ban prohibiting stock trading by employees, numbering around 5,700, who had access to its internal news information management system. The employees were required to pledge in writing that they would not trade in stocks, and were required to gain approval from senior staff to sell shares they already held. NHK banned short-term stock trading completed in periods of six months or less for all other employees. The ban did not extend to employees' families, nor did NHK request any reports on their transactions. On 24 July 2013,

1309-444: A hearing on a case, in which the plaintiffs are seeking the plant's decommission. Boiling water reactor A boiling water reactor ( BWR ) is a type of light water nuclear reactor used for the generation of electrical power. It is the second most common type of electricity-generating nuclear reactor after the pressurized water reactor (PWR), which is also a type of light water nuclear reactor. The main difference between

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1428-632: A high power output (1350 MWe per reactor), and a significantly lowered probability of core damage. Most significantly, the ABWR was a completely standardized design, that could be made for series production. The ABWR was approved by the United States Nuclear Regulatory Commission for production as a standardized design in the early 1990s. Subsequently, numerous ABWRs were built in Japan. One development spurred by

1547-831: A list of operational and decommissioned BWRs, see List of BWRs . Experimental and other non-commercial BWRs include: NHK The Japan Broadcasting Corporation ( Japanese : 日本放送協会 , Hepburn : Nippon Hōsō Kyōkai ) , also known by its romanized initialism NHK , is a Japanese public broadcaster . It is a statutory corporation funded by viewers' payments of a television license fee . NHK operates two terrestrial television channels ( NHK General TV and NHK Educational TV ), three satellite television channels (NHK BS; as well as two ultra-high-definition television channels, NHK BS Premium 4K and NHK BS8K ), and three radio networks ( NHK Radio 1 , NHK Radio 2 , and NHK FM ). NHK also provides an international broadcasting service, known as NHK World-Japan . NHK World-Japan

1666-402: A model of the fuel assembly but power it with resistive heaters. These mock fuel assemblies are put into a test stand where data points are taken at specific powers, flows, pressures. Experimental data is conservatively applied to BWR fuel to ensure that the transition to film boiling does not occur during normal or transient operation. Typical SLMCPR/MCPRSL (Safety Limit MCPR) licensing limit for

1785-399: A more homogeneous distribution of the power: in the upper side the density of the water is lower due to vapour formation, making the neutron moderation less efficient and the fission probability lower. In normal operation, the control rods are only used to keep a homogeneous power distribution in the reactor and to compensate for the consumption of the fuel, while the power is controlled through

1904-542: A reinforced concrete wall that should shield the reactors against a possible tsunami was started in October 2011. The wall was designed 4 meters high and 700 meters long, 11 meters above sea level. This was done to comply with extra governmental instructions ordered after the Fukushima accident. Next to this a new drainage gate was installed to minimize damage to plant facilities in case seawater would be able to climb over

2023-692: A reporter at NHK Metropolitan Broadcasting Center died of congestive heart failure . In May 2014, the Shibuya Labor Standards Inspection Office of the Tokyo Labor Bureau certified it as a karōshi (overwork death). Although NHK did not report on this matter, it was announced in October 2017. Ryōichi Ueda, the chairman of NHK, visited the reporter's parents' home and apologized to them. NHK has occasionally faced various criticisms for its treatment of Japan's wartime history. Katsuto Momii ( 籾井 勝人 ) ,

2142-564: A request to the Ishikawa prefectural government and the town of Shika for the restart of unit 1. The unit returned to power on May 11, 2009, and resumed commercial operation on May 13. Unit 2 reached a peak yearly electricity production of 9279 GWh in 2010. Following the 2011 Fukushima nuclear accident , the plant was temporarily shut down in March 2011 to make changes in order to comply with new regulatory requirements. Construction of

2261-463: A result, after a rash of NHK-related scandals including an accounting one , the number of people who had not paid the license fee surpassed one million watchers. This incident sparked debate over the fairness of the fee system. In 2006, the NHK opted to take legal action against those most flagrantly in violation of the law. This fee and how it is charged is unpopular with some citizens. This led to

2380-410: A safety-related contingency developed. For example, if the reactor got too hot, it would trigger a system that would release soluble neutron absorbers (generally a solution of borated materials, or a solution of borax ), or materials that greatly hamper a chain reaction by absorbing neutrons, into the reactor core. The tank containing the soluble neutron absorbers would be located above the reactor, and

2499-559: A section of the No.1 reactor control system had been dislodged by the quake, and that the Nuclear Regulation Authority chairperson instructed the operator for constructural improvements. Evacuation plans have since been questioned, with the majority of the Ishikawa prefecture designated routes for resident to flee the 30-km radius were cut off, leaving communities isolated. On 13 May 2024, Kanazawa District Court held

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2618-402: A series of notched positions with fixed intervals between these positions. Due to the limitations of the manual control system, it is possible while starting-up that the core can be placed into a condition where movement of a single control rod can cause a large nonlinear reactivity change, which could heat fuel elements to the point they fail (melt, ignite, weaken, etc.). As a result, GE developed

2737-415: A set of rules in 1977 called BPWS (Banked Position Withdrawal Sequence) which help minimize the effect of any single control rod movement and prevent fuel damage in the case of a control rod drop accident. BPWS separates control rods into four groups, A1, A2, B1, and B2. Then, either all of the A control rods or B control rods are pulled full out in a defined sequence to create a " checkerboard " pattern. Next,

2856-514: A single core-damaging event during their 100-year lifetimes. Earlier designs of the BWR, the BWR/4, had core damage probabilities as high as 1×10 core-damage events per reactor-year. This extraordinarily low CDP for the ESBWR far exceeds the other large LWRs on the market. Reactor start up ( criticality ) is achieved by withdrawing control rods from the core to raise core reactivity to a level where it

2975-468: A small group of engineers accidentally increased the reactor power level on an experimental reactor to such an extent that the water quickly boiled. This shut down the reactor, indicating the useful self-moderating property in emergency circumstances. In particular, Samuel Untermyer II , a researcher at Argonne National Laboratory , proposed and oversaw a series of experiments: the BORAX experiments —to see if

3094-465: A tortuous path where the water droplets are slowed and directed out into the downcomer or annulus region. The "dry" steam then exits the RPV through four main steam lines and goes to the turbine. Reactor power is controlled via two methods: by inserting or withdrawing control rods (control blades) and by changing the water flow through the reactor core . Positioning (withdrawing or inserting) control rods

3213-451: Is GE Hitachi Nuclear Energy , which specializes in the design and construction of this type of reactor. A boiling water reactor uses demineralized water as a coolant and neutron moderator . Heat is produced by nuclear fission in the reactor core, and this causes the cooling water to boil, producing steam. The steam is directly used to drive a turbine , after which it is cooled in a condenser and converted back to liquid water. This water

3332-401: Is a limit on fuel rod power in the reactor core. For new fuel, this limit is typically around 13 kW/ft (43 kW/m) of fuel rod. This limit ensures that the centerline temperature of the fuel pellets in the rods will not exceed the melting point of the fuel material ( uranium / gadolinium oxides) in the event of the worst possible plant transient/scram anticipated to occur. To illustrate

3451-459: Is also bilingual and airs on NHK General TV and the international channels and NHK World Premium. World News , a program which airs bulletins from international broadcasters interpreted in Japanese, is aired on NHK BS1 with Catch! Sekai no Top News in the morning and International News Report at night, with the latter also airing on NHK World Premium. News on NHK BS1 is aired at 50 minutes past

3570-665: Is composed of NHK World TV , NHK World Premium , and the shortwave radio service Radio Japan (RJ). World Radio Japan also makes some of its programs available on the Internet. NHK was the first broadcaster in the world to broadcast in high-definition (using multiple sub-Nyquist sampling encoding , also known as Hi-Vision) and in 8K . In regards to NHK's relationship with Johnny & Associates, they have stated that NHK acknowledges that sexual abuse allegations related to Johnny & Associates had repeatedly been reported for many years, but NHK also stated that they lacked awareness of

3689-503: Is done via cranes and under water. For this reason the spent fuel storage pools are above the reactor in typical installations. They are shielded by water several times their height, and stored in rigid arrays in which their geometry is controlled to avoid criticality. In the Fukushima Daiichi nuclear disaster this became problematic because water was lost (as it was heated by the spent fuel) from one or more spent fuel pools and

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3808-421: Is easily varied by simply increasing or decreasing the forced recirculation flow through the recirculation pumps. The two-phase fluid (water and steam) above the core enters the riser area, which is the upper region contained inside of the shroud. The height of this region may be increased to increase the thermal natural recirculation pumping head. At the top of the riser area is the moisture separator. By swirling

3927-447: Is evident that the nuclear chain reaction is self-sustaining. This is known as "going critical". Control rod withdrawal is performed slowly, as to carefully monitor core conditions as the reactor approaches criticality. When the reactor is observed to become slightly super-critical, that is, reactor power is increasing on its own, the reactor is declared critical. Rod motion is performed using rod drive control systems. Newer BWRs such as

4046-459: Is funded by the Japanese government. The annual budget of NHK is subject to review and approval by the Diet of Japan . The Diet also appoints the twelve-member board of governors (経営委員会 keiei iinkai ) that oversees NHK. NHK is managed on a full-time basis by an executive board ( 理事会 , rijikai ) consisting of a president, executive vice president and seven to ten managing directors who oversee

4165-569: Is in place to ensure that the highest powered fuel rod will not melt if its power was rapidly increased following a pressurization transient. Abiding by the LHGR limit precludes melting of fuel in a pressurization transient. APLHGR, being an average of the Linear Heat Generation Rate (LHGR), a measure of the decay heat present in the fuel bundles, is a margin of safety associated with the potential for fuel failure to occur during

4284-423: Is known as the advanced boiling water reactor (ABWR). The ABWR was developed in the late 1980s and early 1990s, and has been further improved to the present day. The ABWR incorporates advanced technologies in the design, including computer control, plant automation, control rod removal, motion, and insertion, in-core pumping, and nuclear safety to deliver improvements over the original series of production BWRs, with

4403-433: Is licensed to operate, the fuel vendor/licensee simulate events with computer models. Their approach is to simulate worst case events when the reactor is in its most vulnerable state. APLHGR is commonly pronounced as "Apple Hugger" in the industry. PCIOMR is a set of rules and limits to prevent cladding damage due to pellet-clad interaction. During the first nuclear heatup, nuclear fuel pellets can crack. The jagged edges of

4522-408: Is monitored with an empirical correlation that is formulated by vendors of BWR fuel (GE, Westinghouse, AREVA-NP). The vendors have test rigs where they simulate nuclear heat with resistive heating and determine experimentally what conditions of coolant flow, fuel assembly power, and reactor pressure will be in/out of the transition boiling region for a particular fuel design. In essence, the vendors make

4641-453: Is required that the decay heat stored in the fuel assemblies at any one time does not overwhelm the ECCS. As such, the measure of decay heat generation known as LHGR was developed by GE's engineers, and from this measure, APLHGR is derived. APLHGR is monitored to ensure that the reactor is not operated at an average power level that would defeat the primary containment systems. When a refueled core

4760-435: Is saturated with a steam quality of about 15%. Typical core flow may be 45,000,000 kg/h (100,000,000 lb/h) with 6,500,000 kg/h (14,500,000 lb/h) steam flow. However, core-average void fraction is a significantly higher fraction (~40%). These sort of values may be found in each plant's publicly available Technical Specifications, Final Safety Analysis Report, or Core Operating Limits Report. The heating from

4879-515: Is standardized, with discounts for office workers and students who commute, as well a discount for residents of Okinawa prefecture . For viewers making annual payments by credit card with no special discounts, the reception fee is 13,600 yen per year for terrestrial reception only, and 24,090 yen per year for both terrestrial and broadcast satellite reception. However, the Broadcasting Act specifies no punitive actions for nonpayment; as

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4998-408: Is switched to a "Three-Element" control mode, where the controller looks at the current water level in the reactor, as well as the amount of water going in and the amount of steam leaving the reactor. By using the water injection and steam flow rates, the feed water control system can rapidly anticipate water level deviations and respond to maintain water level within a few inches of set point. If one of

5117-492: Is terminated by the automatic insertion of the control rods. So, when the reactor is isolated from the turbine rapidly, pressure in the vessel rises rapidly, which collapses the water vapor, which causes a power excursion which is terminated by the Reactor Protection System. If a fuel pin was operating at 13.0 kW/ft prior to the transient, the void collapse would cause its power to rise. The FLLHGR limit

5236-501: Is the normal method for controlling power when starting up a BWR. As control rods are withdrawn, neutron absorption decreases in the control material and increases in the fuel, so reactor power increases. As control rods are inserted, neutron absorption increases in the control material and decreases in the fuel, so reactor power decreases. Differently from the PWR, in a BWR the control rods ( boron carbide plates) are inserted from below to give

5355-429: Is then returned to the reactor core, completing the loop. The cooling water is maintained at about 75 atm (7.6 MPa , 1000–1100 psi ) so that it boils in the core at about 285 °C (550 °F). In comparison, there is no significant boiling allowed in a pressurized water reactor (PWR) because of the high pressure maintained in its primary loop—approximately 158 atm (16 MPa, 2300 psi). The core damage frequency of

5474-880: The Gyokuon-hōsō , the surrender speech made by Emperor Hirohito , in August 1945. Following the war, in September 1945, the Allied occupation administration under General Douglas MacArthur banned all international broadcasting by NHK, and repurposed several NHK facilities and frequencies for use by the Far East Network (now American Forces Network ). Japanese-American radio broadcaster Frank Shozo Baba joined NHK during this time and led an early post-war revamp of its programming. Radio Japan resumed overseas broadcasts in 1952. A new Broadcasting Act  [ ja ]

5593-581: The 1964 Summer Olympics , the first widely televised Olympic Games. The complex was gradually expanded through 1973 when it became the headquarters for NHK. The previous headquarters adjacent to Hibiya Park was redeveloped as the Hibiya City high-rise complex. NHK began experimental satellite broadcasting with the NHK BS ;1 channel in 1984, followed by NHK BS 2 in 1985. Both channels began regular broadcasts in 1989. In April 2011, BS 1

5712-495: The 2011 Tōhoku earthquake and tsunami – Iwate , Miyagi , Fukushima – where it was discontinued on 31 March 2012). From 1963 to 1999, NHK published the journal Studies of broadcasting: an international annual of broadcasting science . NHK is a dependent corporation chartered by the Japanese Broadcasting Act and primarily funded by license fees. NHK World broadcasting (for overseas viewers/listeners)

5831-519: The 2011 Tōhoku earthquake and tsunami . NHK broadcasts sumo wrestling , baseball games, Olympic Games , soccer games, and a range of other sports. Their broadcast of the last two days of October 1952's autumn sumo tournament became the first ever televised sports broadcast in Japan. The NHK Symphony Orchestra , financially sponsored by NHK, was formerly (until 1951) the Japanese Symphony Orchestra. Its website details

5950-554: The ABWR and ESBWR as well as all German and Swedish BWRs use the Fine Motion Control Rod Drive system, which allows multiple rods to be controlled with very smooth motions. This allows a reactor operator to evenly increase the core's reactivity until the reactor is critical. Older BWR designs use a manual control system, which is usually limited to controlling one or four control rods at a time, and only through

6069-603: The Black Lives Matter movement and George Floyd protests that was criticized for its "crude" animation of protesters and its focus on economic inequality rather than police brutality. An official statement signed by Yuichi Tabata, head of NHK's International News Division, was released through NHK's official website. On 9 January 2022, NHK issued an apology over false allegations made in Director Naomi Kawase 's Tokyo Olympics documentary. Kawase

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6188-565: The Emergency Core Cooling System . The ECCS is designed to rapidly flood the reactor pressure vessel, spray water on the core itself, and sufficiently cool the reactor fuel in this event. However, like any system, the ECCS has limits, in this case, to its cooling capacity, and there is a possibility that fuel could be designed that produces so much decay heat that the ECCS would be overwhelmed and could not cool it down successfully. So as to prevent this from happening, it

6307-722: The Imperial Japanese Army nationalised all public news agencies and coordinated their efforts via the Information Liaison Confidential Committee. All published and broadcast news reports became official announcements of the Imperial Army General Headquarters in Tokyo for the duration of World War II . The famous Tokyo Rose wartime programs were broadcast by NHK. NHK also recorded and broadcast

6426-789: The Japan Meteorological Agency makes NHK capable of delivering earthquake early warnings seconds after detection, as well as a more detailed report with Shindo intensity measurements within two-to-three minutes after the quake. They also broadcast air attack warnings in the event of war, using the J-Alert system. All warnings are broadcast in Japanese, with tsunami warnings also delivered in four foreign languages: English, Mandarin Chinese, Korean and Portuguese (Japan has small Chinese , Korean and Brazilian populations). The warnings were broadcast in these languages during

6545-546: The Taipei Times , stating, "[South] Korea's statements that Japan is the only nation that forced this are puzzling. 'Give us money, compensate us', they say, but since all of this was resolved by the Japan–Korea peace treaty, why are they reviving this issue? It's strange." It was subsequently reported by The Japan Times that on his first day at NHK Momii asked members of the executive team to hand in their resignation on

6664-555: The 21st Director-General of NHK, caused controversy by discussing Japan's actions in World War II at his first press conference after being appointed on 20 December 2013. It was reported that Momii said NHK should support the Japanese government in its territorial dispute with China and South Korea. He also caused controversy by what some describe as the playing down of the comfort women issue in World War II, according to

6783-479: The NHK brand is common for the whole country. All of them can also be tuned through the Internet, within the national territory. It also has one exclusive satellite channel, as well as two in ultra-high definition. NHK is funded by reception fees ( 受信料 , jushinryō ) , a system analogous to the license fee used in some English-speaking countries. The Broadcasting Act which governs NHK's funding stipulates anyone with equipment able to receive NHK must pay. The fee

6902-568: The NRA had reached a unanimous decision not to seek further opinion from experts who raised concerns of the faults being active. In January 2024 the plant was closest to a magnitude 7.6 earthquake in Ishikawa Prefecture , and survived the event with no major damage. Some water from a spent fuel pool spilled over during the earthquake. Following the Noto earthquake , the operator said

7021-482: The US's first research effort in nuclear power being devoted to the PWR, which was highly suited for naval vessels (submarines, especially), as space was at a premium, and PWRs could be made compact and high-power enough to fit into such vessels. But other researchers wanted to investigate whether the supposed instability caused by boiling water in a reactor core would really cause instability. During early reactor development,

7140-499: The absorption solution, once the system was triggered, would flow into the core through force of gravity, and bring the reaction to a near-complete stop. Another example was the Isolation Condenser system , which relied on the principle of hot water/steam rising to bring hot coolant into large heat exchangers located above the reactor in very deep tanks of water, thus accomplishing residual heat removal. Yet another example

7259-422: The areas of NHK operations. The executive board reports to the board of governors. It maintains three radio stations available nationwide: All of them can also be tuned through the Internet, within the national territory. It manages two open signal channels through digital terrestrial television. Since Japan has a television network system, it schedules territorial disconnections in each of its centers. However,

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7378-484: The broadcasting industry" when it comes to using performers who best fit program content and production. The public broadcaster added that it did not fully acknowledge the sexual abuse matter despite various weekly magazine articles about the allegations and a Tokyo High Court ruling in 2004. A few weeks later, NHK announced that it would suspend new contracts with Johnny's performers–including for their annual New Year's Eve television special Kōhaku Uta Gassen –until

7497-436: The case of a BWR, light water. If the core is uncovered for too long, fuel failure can occur; for the purpose of design, fuel failure is assumed to occur when the temperature of the uncovered fuel reaches a critical temperature (1100 °C, 2200 °F). BWR designs incorporate failsafe protection systems to rapidly cool and make safe the uncovered fuel prior to it reaching this temperature; these failsafe systems are known as

7616-471: The cladding remains intact for the life of the rod. The BWR concept was developed slightly later than the PWR concept. Development of the BWR started in the early 1950s, and was a collaboration between General Electric (GE) and several US national laboratories. Research into nuclear power in the US was led by the three military services. The Navy, seeing the possibility of turning submarines into full-time underwater vehicles, and ships that could steam around

7735-479: The company has implemented compensation and recurrence prevention measures. In February 2024, the company announced a strict policy of terminating the appearance of talents formerly affiliated with Johnny & Associates on its programs and not allowing them to appear on new programs after FY2024. In October 2024, NHK Chairman Nobuo Inaba announced at a regular press conference that, he had confirmed efforts of Smile-Up to compensate victims and prevent recurrence and

7854-401: The cooling pool water level "has not changed significantly" after the spillage of more than 400 litres at Units 1 and 2, and that it "did not impact radiation levels outside." The plant's transformers were also damaged by the quake, leaving it "unable to receive electricity from outside". On 10 January, a second oil leak "in several gutters surrounding the main transformer of the No.2 reactor"

7973-477: The core after emergency shut down. The reactor fuel rods are occasionally replaced by moving them from the reactor pressure vessel to the spent fuel pool. A typical fuel cycle lasts 18–24 months, with about one third of fuel assemblies being replaced during a refueling outage. The remaining fuel assemblies are shuffled to new core locations to maximize the efficiency and power produced in the next fuel cycle. Because they are hot both radioactively and thermally, this

8092-454: The core creates a thermal head that assists the recirculation pumps in recirculating the water inside of the RPV. A BWR can be designed with no recirculation pumps and rely entirely on the thermal head to recirculate the water inside of the RPV. The forced recirculation head from the recirculation pumps is very useful in controlling power, however, and allows achieving higher power levels that would not otherwise be possible. The thermal power level

8211-564: The documentary should be removed. Some activists were concerned that the misinformation was spread by NHK to silence those who opposed the Tokyo Olympics during the pandemic. NHK denied that the footage was deliberately fabricated to mislead the public. On 13 January 2022, the NHK Osaka director Terunobu Maeda apologized during a press conference, admitting that the captions "should not have been included". Once again, he denied that

8330-408: The downcomer or annulus region, which is separated from the core by a tall shroud. The water then goes through either jet pumps or internal recirculation pumps that provide additional pumping power (hydraulic head). The water now makes a 180-degree turn and moves up through the lower core plate into the nuclear core, where the fuel elements heat the water. Water exiting the fuel channels at the top guide

8449-400: The earthquake could have altered the geometry. The fact that the fuel rods' cladding is a zirconium alloy was also problematic since this element can react with steam at temperatures above 1,500 K (1,230 °C) to produce hydrogen, which can ignite with oxygen in the air. Normally the fuel rods are kept sufficiently cool in the reactor and spent fuel pools that this is not a concern, and

8568-611: The end of April, its members would freeze their licence fee payments for half a year. While Momii did not resign, he was not reappointed and retired after serving only one term of three years. On 17 October 2014, The Times claimed to have received internal NHK documents which banned any reference to the Nanjing Massacre , to Japan's use of wartime sex slaves during World War II, and to its territorial dispute with China in its English-language broadcasting. On 10 June 2020, NHK apologized and took down an 80-second video about

8687-532: The event of a major safety contingency for at least 48 hours following the safety contingency; thence, it would only require periodic refilling of cooling water tanks located completely outside of the reactor, isolated from the cooling system, and designed to remove reactor waste heat through evaporation. The simplified boiling water reactor was submitted to the United States Nuclear Regulatory Commission , however, it

8806-428: The event of a transient requiring the quenching of steam), as well as the drywell, the elimination of the heat exchanger, the steam dryer, the distinctive general layout of the reactor building, and the standardization of reactor control and safety systems. The first, General Electric ( GE ), series of production BWRs evolved through 6 iterative design phases, each termed BWR/1 through BWR/6. (BWR/4s, BWR/5s, and BWR/6s are

8925-449: The feedwater heaters enters the reactor pressure vessel (RPV) through nozzles high on the vessel, well above the top of the nuclear fuel assemblies (these nuclear fuel assemblies constitute the "core") but below the water level. The feedwater enters into the downcomer or annulus region and combines with water exiting the moisture separators. The feedwater subcools the saturated water from the moisture separators. This water now flows down

9044-574: The formation of the NHK Party ( NHK党 , NHK tō ) , also known as N-Koku ( N国 ) , a single-issue political party , which has protested this fee with representatives in the upper house . NHK broadcasts a variety of programming. NHK offers local, national, and world news reports. NHK News 7 airs daily and is broadcast bilingually with both Japanese and English audio tracks on NHK General TV and NHK's international channels TV Japan and NHK World Premium . The flagship news program News Watch 9

9163-442: The fuel, and reactor power increases. As flow of water through the core is decreased, steam voids remain longer in the core, the amount of liquid water in the core decreases, neutron moderation decreases, fewer neutrons are slowed enough to be absorbed by the fuel, and reactor power decreases. Thus the BWR has a negative void coefficient . Reactor pressure in a BWR is controlled by the main turbine or main steam bypass valves. Unlike

9282-445: The grid yearly during the first ten years of operation with a peak production of 4432 GWh in 1997. On June 18, 1999, during an inspection, an emergency control rod insertion was to be performed on Unit 1. One rod was to be inserted into the reactor, however, three control rods fell by accident. For the next 15 minutes, the reactor was in a critical state, an unintended self-sustaining nuclear fission chain reaction. This incident

9401-517: The grounds they had all been appointed by his predecessor. A number of civil society groups protested against Momii's continued tenure as Director-General of NHK. On 27 January 2014, the Viewers' Community to Observe and Encourage NHK ( NHKを監視・激励する視聴者コミュニティ ) issued a public letter calling for Momii's resignation on the grounds that the remarks he made at his inaugural press conference were explosive. The letter stated that if Momii did not resign by

9520-405: The heated surface to increase drastically to once again reach equilibrium heat transfer with the cooling fluid. In other words, steam semi-insulates the heated surface and surface temperature rises to allow heat to get to the cooling fluid (through convection and radiative heat transfer). Nuclear fuel could be damaged by film boiling; this would cause the fuel cladding to overheat and fail. MFLCPR

9639-512: The hour except during live sports events. NHK also offers news for the deaf (which airs on NHK Educational TV), regional news (which airs on NHK General TV) and children's news. Newsline is an English-language newscast designed for foreign viewers and airs on NHK World . In his book Broadcasting Politics in Japan: NHK and Television News , Ellis S. Krauss states: 'In the 1960s and 1970s, external critics of NHK news were complaining about

9758-433: The incident was a fabrication. In December 2023, Japan's Broadcasting Ethics and Program Improvement Organization (BPO) concluded that NHK had breached broadcasting ethics in its "News Watch 9" program, where people believed to have died from COVID-19 vaccine injury were treated as if they had died from COVID-19. Regarding the incident as an inappropriate way of reporting, NHK stated that it would take measures to avoid

9877-405: The inner walls of the fuel cladding which are resistant to perforation due to pellet-clad interactions, and the second is a set of rules created under PCIOMR. The PCIOMR rules require initial "conditioning" of new fuel. This means, for the first nuclear heatup of each fuel element, that local bundle power must be ramped very slowly to prevent cracking of the fuel pellets and limit the differences in

9996-399: The issue at that time and chose not to follow up or cover the issue entirely. In addition, they stated that they failed in their role as a news media organization, and simply sat idle as many minors became sexual abuse victims. On 8 September, 2023, NHK , said in a statement that they took the matter seriously, and that they would "work harder to ensure that human rights are more respected in

10115-615: The leadership of Count Gotō Shinpei . Tokyo Broadcasting Station, along with separate organizations in Osaka and Nagoya , began radio broadcasts in 1925. The three stations merged under the first incarnation of NHK in August 1926. NHK was modelled on the BBC of the United Kingdom , and the merger and reorganisation was carried out under the auspices of the pre-war Ministry of Communications . NHK's second radio network began in 1931, and

10234-400: The leading fuel bundle is to "dry-out" (or "departure from nucleate boiling" for a PWR). Transition boiling is the unstable transient region where nucleate boiling tends toward film boiling . A water drop dancing on a hot frying pan is an example of film boiling. During film boiling a volume of insulating vapor separates the heated surface from the cooling fluid; this causes the temperature of

10353-571: The most common types in service today.) The vast majority of BWRs in service throughout the world belong to one of these design phases. Containment variants were constructed using either concrete or steel for the Primary Containment, Drywell and Wetwell in various combinations. Apart from the GE designs there were others by ABB (Asea-Atom), MITSU, Toshiba and KWU (Kraftwerk Union). See List of boiling water reactors . A newer design of BWR

10472-469: The opposing group (B or A) is pulled in a defined sequence to positions 02, then 04, 08, 16, and finally full out (48). By following a BPWS compliant start-up sequence, the manual control system can be used to evenly and safely raise the entire core to critical, and prevent any fuel rods from exceeding 280 cal/gm energy release during any postulated event which could potentially damage the fuel. Several calculated/measured quantities are tracked while operating

10591-1131: The orchestra's history and ongoing concert programme. Since 1953, NHK has broadcast the Kōhaku Uta Gassen song contest on New Year's Eve, ending shortly before midnight in PIX System . A sentimental morning show , a weekly jidaigeki and a year-long show, the Taiga drama , spearhead the network's fiction offerings. NHK is also making efforts at broadcasting dramas made in foreign countries as overseas drama ( 海外ドラマ , Kaigai Dorama ) . The longest running children's show in Japan, Okaasan to Issho ( おかあさんといっしょ , With Mother ) , started broadcasting in 1959 and still airs to this day Monday to Friday at 17:36–18:00  JST , Sunday at 17:30–17:54 JST, with rebroadcasts Tuesday to Sunday at 5:00–5:24 JST on NHK World Premium. In 2007, three employees of NHK were fined and fired for insider trading . They had profited by trading shares based on exclusive NHK knowledge. On 11 July 2008, NHK introduced

10710-404: The pellet can rub and interact with the inner cladding wall. During power increases in the fuel pellet, the ceramic fuel material expands faster than the fuel cladding, and the jagged edges of the fuel pellet begin to press into the cladding, potentially causing a perforation. To prevent this from occurring, two corrective actions were taken. The first is the inclusion of a thin barrier layer against

10829-479: The pumps could be repaired during the next refueling outage. Instead, the designers of the simplified boiling water reactor used thermal analysis to design the reactor core such that natural circulation (cold water falls, hot water rises) would bring water to the center of the core to be boiled. The ultimate result of the passive safety features of the SBWR would be a reactor that would not require human intervention in

10948-510: The rates of thermal expansion of the fuel. PCIOMR rules also limit the maximum local power change (in kW/ft*hr), prevent pulling control rods below the tips of adjacent control rods, and require control rod sequences to be analyzed against core modelling software to prevent pellet-clad interactions. PCIOMR analysis look at local power peaks and xenon transients which could be caused by control rod position changes or rapid power changes to ensure that local power rates never exceed maximum ratings. For

11067-472: The reactor core passes through steam separators and dryer plates above the core and then directly to the turbine , which is part of the reactor circuit. Because the water around the core of a reactor is always contaminated with traces of radionuclides due to neutron capture from the water, the turbine must be shielded during normal operation, and radiological protection must be provided during maintenance. The increased cost related to operation and maintenance of

11186-456: The reactor was estimated to be between 10 and 10 (i.e., one core damage accident per every 10,000 to 10,000,000 reactor years). Steam exiting the turbine flows into condensers located underneath the low-pressure turbines, where the steam is cooled and returned to the liquid state (condensate). The condensate is then pumped through feedwater heaters that raise its temperature using extraction steam from various turbine stages. Feedwater from

11305-401: The reactor's heatup and cooldown rates while steaming is still in progress. Reactor water level is controlled by the main feedwater system. From about 0.5% power to 100% power, feedwater will automatically control the water level in the reactor. At low power conditions, the feedwater controller acts as a simple PID control by watching reactor water level. At high power conditions, the controller

11424-414: The reactor. The high-pressure turbine exhaust passes through a steam reheater which superheats the steam to over 400 degrees F (204.4 degrees celcius) for the low-pressure turbines to use. The exhaust of the low-pressure turbines is sent to the main condenser. The steam reheaters take some of the turbine's steam and use it as a heating source to reheat what comes out of the high-pressure turbine exhaust. While

11543-562: The reheaters take steam away from the turbine, the net result is that the reheaters improve the thermodynamic efficiency of the plant. A modern BWR fuel assembly comprises 74 to 100 fuel rods , and there are up to approximately 800 assemblies in a reactor core , holding up to approximately 140 short tons of low-enriched uranium . The number of fuel assemblies in a specific reactor is based on considerations of desired reactor power output, reactor core size and reactor power density. A modern reactor has many safety systems that are designed with

11662-479: The response of LHGR in transient imagine the rapid closure of the valves that admit steam to the turbines at full power. This causes the immediate cessation of steam flow and an immediate rise in BWR pressure. This rise in pressure effectively subcools the reactor coolant instantaneously; the voids (vapor) collapse into solid water. When the voids collapse in the reactor, the fission reaction is encouraged (more thermal neutrons); power increases drastically (120%) until it

11781-698: The resulting design to a larger size of 1,600  MWe (4,500 MWth). This Economic Simplified Boiling Water Reactor (ESBWR) design was submitted to the US Nuclear Regulatory Commission for approval in April 2005, and design certification was granted by the NRC in September 2014. Reportedly, this design has been advertised as having a core damage probability of only 3×10 core damage events per reactor-year. That is, there would need to be 3 million ESBWRs operating before one would expect

11900-482: The separation of management from Starto Entertainment is steadily progressing, and that requests to perform–including Kōhaku Uta Gassen for current Starto celebrities would resume. Commercial broadcasters had already announced on the resumption of new appointments to celebrities belonging to Starto. NHK's earliest forerunner was the Tokyo Broadcasting Station ( 東京放送局 ) , founded in 1924 under

12019-464: The so-called "100% rod line", power may be varied from approximately 30% to 100% of rated power by changing the reactor recirculation system flow by varying the speed of the recirculation pumps or modulating flow control valves. As flow of water through the core is increased, steam bubbles ("voids") are more quickly removed from the core, the amount of liquid water in the core increases, neutron moderation increases, more neutrons are slowed to be absorbed by

12138-656: The strict neutrality, the lack of criticism of the government, and the 'self-regulation in covering events'. Krauss claims that little had changed by the 1980s and 1990s. After the Fukushima nuclear disaster in 2011, NHK was criticised for underplaying the dangers from radioactive contamination . Under the Broadcasting Act, NHK is under the obligation to broadcast early warning emergency reporting in times of natural disasters such as earthquakes and tsunamis . Their national network of seismometers in cooperation with

12257-440: The success of the ABWR in Japan is that General Electric's nuclear energy division merged with Hitachi Corporation's nuclear energy division, forming GE Hitachi Nuclear Energy , which is now the major worldwide developer of the BWR design. Parallel to the development of the ABWR, General Electric also developed a different concept, known as the simplified boiling water reactor (SBWR). This smaller 600 megawatt electrical reactor

12376-511: The third radio network (FM) began in 1937. NHK began shortwave broadcasting on an experimental basis in the 1930s, and began regular English- and Japanese-language shortwave broadcasts in 1935 under the name Radio Japan , initially aimed at ethnic Japanese listeners in Hawaii and the west coast of North America . By the late 1930s, NHK's overseas broadcasts were known as Radio Tokyo , which became an official name in 1941. In November 1941,

12495-461: The turbine and incorporated heat exchangers for the generation of secondary steam to drive separate parts of the turbines. The literature does not indicate why this was the case, but it was eliminated on production models of the BWR. The first generation of production boiling water reactors saw the incremental development of the unique and distinctive features of the BWR: the torus (used to quench steam in

12614-515: The two feedwater pumps fails during operation, the feedwater system will command the recirculation system to rapidly reduce core flow, effectively reducing reactor power from 100% to 50% in a few seconds. At this power level a single feedwater pump can maintain the core water level. If all feedwater is lost, the reactor will scram and the Emergency Core Cooling System is used to restore reactor water level. Steam produced in

12733-418: The two-phase flow in cyclone separators, the steam is separated and rises upwards towards the steam dryer while the water remains behind and flows horizontally out into the downcomer or annulus region. In the downcomer or annulus region, it combines with the feedwater flow and the cycle repeats. The saturated steam that rises above the separator is dried by a chevron dryer structure. The "wet" steam goes through

12852-498: The wall and would submerge the plant. Other emergency safety measures included the installing of an extra pump to cool the reactors with seawater and an extra power source to operate a valve for venting steam out of reactors. Construction was expected to be completed by the end of March 2013. After finishing the safety upgrades, permission for the restart of unit 2 from the Nuclear Regulation Authority (NRA)

12971-478: The water flow (see below). Some early BWRs and the proposed ESBWR (Economic Simplified BWR made by General Electric Hitachi) designs use only natural circulation with control rod positioning to control power from zero to 100% because they do not have reactor recirculation systems. Changing (increasing or decreasing) the flow of water through the core is the normal and convenient method for controlling power from approximately 30% to 100% reactor power. When operating on

13090-546: The world without refueling, sent their man in engineering, Captain Hyman Rickover to run their nuclear power program. Rickover decided on the PWR route for the Navy, as the early researchers in the field of nuclear power feared that the direct production of steam within a reactor would cause instability, while they knew that the use of pressurized water would definitively work as a means of heat transfer. This concern led to

13209-421: Was covered up by the operator, and was not revealed until March 15, 2007. Unit 1 was subsequently shut down from March 2007 to March 2009, during judicial and bureaucratic evaluation. In April 2007 the event had been provisionally categorized as an INES level-2 incident . A lower court had ordered the entire plant to be shut down, but that decision was later overturned by Nagoya 's high court. The utility put in

13328-500: Was enacted in 1950, which made NHK a listener-supported independent corporation and simultaneously opened the market for commercial broadcasting in Japan. NHK started television broadcasting in 1953, followed by its educational TV channel in 1959 and color television broadcasts in 1960. NHK opened the first stage of its current headquarters in Japan's capital city 's special ward Shibuya as an international broadcasting center for

13447-422: Was first sought in August 2014. The NRA safety review was however delayed considerably over the determination of whether there are active geological faults underneath the site, which lasted until March 2023, when it was concluded that there are no such faults. Following these results, Hokuriku Electric submitted an application with a plan to restart unit 2 in early 2026. Unit 1 is to follow soon afterwards. Earlier,

13566-407: Was notable for its incorporation—for the first time ever in a light water reactor —of " passive safety " design principles. The concept of passive safety means that the reactor, rather than requiring the intervention of active systems, such as emergency injection pumps, to keep the reactor within safety margins, was instead designed to return to a safe state solely through operation of natural forces if

13685-930: Was rebranded while BS 2 channel ceased broadcasting and was replaced by "BS Premium" which broadcasts on the channel formerly used by BShi. International satellite broadcasts to North America and Europe began in 1995, which led to the launch of NHK World in 1998. It became free-to-air over the Astra 19.2°E ( Astra 1L ) and Eurobird satellites in Europe in 2008. NHK began digital television broadcasting in December 2000 through BS Digital, followed by terrestrial digital TV broadcasts in three major metropolitan areas in 2003. NHK's digital television coverage gradually expanded to cover almost all of Japan by 24 July 2011, when analog transmissions were discontinued & ended (except in three prefectures that were heavily affected by

13804-519: Was reported, as well a second "oil slick measuring about 100 meters by 30 meters" on the sea in front of the power plant. "In addition to the loss of the two external power sources [...] some 23,400 litres of oil leaked when transformers for both the No. 1 and 2 reactors were damaged," the Mainichi reported. Following the incident, the plant's former construction site manager has claimed the plant should be decommissioned. On 17 April, NHK reported that

13923-582: Was selected by the IOC in 2018 to cover Japanese reactions to the event and later during the COVID-19 pandemic . Footage and captions in the documentary alleged that protesters were being paid money to attend anti-Olympics rallies. One of the men interviewed later stated he was "unsure" if he had actually attended any anti-Olympics rallies. NHK Osaka cited "editorial oversights" and "deficiencies in research", issuing an apology. Some anti-Olympic activists demanded that

14042-439: Was the omission of recirculation pumps within the core; these pumps were used in other BWR designs to keep cooling water moving; they were expensive, hard to reach to repair, and could occasionally fail; so as to improve reliability, the ABWR incorporated no less than 10 of these recirculation pumps, so that even if several failed, a sufficient number would remain serviceable so that an unscheduled shutdown would not be necessary, and

14161-399: Was withdrawn prior to approval; still, the concept remained intriguing to General Electric's designers, and served as the basis of future developments. During a period beginning in the late 1990s, GE engineers proposed to combine the features of the advanced boiling water reactor design with the distinctive safety features of the simplified boiling water reactor design, along with scaling up

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