TEPCO admits error in screening report
Japan’s Nuclear Regulation Authority is demanding an explanation from Tokyo Electric Power Company.
TEPCO has admitted to submitting inaccurate information from calculations 3 years ago on plans for restarting two of its nuclear reactors in Niigata Prefecture.
The regulator is in the final stages of screening the No.6 and 7 reactors at TEPCO’s Kashiwazaki-Kariwa plant.
The reactors must meet new government requirements introduced after the 2011 Fukushima disaster.
Regulators gathered on Tuesday for discussions with TEPCO about buildings at the plant to be used as headquarters in an emergency.
TEPCO officials admitted one of the buildings lacked the necessary quake-resistance in all 7 of the company’s tests.
They had earlier said that the building had failed 5 of the 7 tests. They said they would not use the building.
They blamed the discrepancy on a failure by the civil engineering department to convey test results to the equipment design department.
The regulators noted the lack of coordination between TEPCO departments on the impact of soil liquefaction on breakwaters.
They called the mistakes unacceptable, and they’re demanding that TEPCO provide details and countermeasures.
Kashiwazaki Mayor Masahiro Sakurai, center, visiting the Kashiwazaki-Kariwa nuclear power plant in Niigata Prefecture during an emergency drill in December. He is briefed by plant chief Chikashi Shitara, right
Key Niigata nuclear plant building may not be quake-proof
Tokyo Electric Power Co. has revealed that a key building at its Kashiwazaki-Kariwa nuclear power plant may not be able to withstand even half of the assumed strongest seismic shaking, contrary to its earlier assurances.
TEPCO’s disclosure came Feb. 14 during a screening by the Nuclear Regulation Authority (NRA) for the restart of the No. 6 and No. 7 reactors at the nuclear power plant in Niigata Prefecture, which is the world’s largest.
The utility became aware of the possibility in 2014, but the information was not shared within the company. TEPCO reported to the NRA that the building can withstand temblors of 7, the highest category on the Japanese seismic intensity scale.
The building is designed to serve as an on-site emergency headquarters in the event of a severe accident, such as one caused by an earthquake.
An earthquake that occurred off the Chuetsu region of Niigata Prefecture in 2007 badly damaged the Kashiwazaki-Kariwa plant.
In response, TEPCO constructed the building in question in 2009. At that time, it said the structure could withstand the assumed biggest earthquake motions that are 1.5 times stronger than those described in the Building Standards Law.
In 2014, the utility checked the building’s anti-quake capabilities again. It found that it may not be able to withstand horizontal movements triggered by even half the anticipated strongest earthquake, and that it could collapse into the side of an adjacent building.
That information was not conveyed to the company’s division in charge of the NRA’s screening, and thus escaped notice from NRA inspections.
Takafumi Anegawa, managing executive officer of TEPCO, apologized, saying, “We did not conceal the possibility. The in-house liaison was insufficient.”
An NRA official said, “Information is not shared in the company. Lessons from the accident at the Fukushima No. 1 nuclear power plant are not utilized.”
Japan’s nuclear watchdog will ease quake-related and other regulations on storing spent fuel to push the use of dry casks and reduce the dangers stemming from power failures at nuclear power plants.
The Nuclear Regulation Authority decided on Jan. 25 that utilities should place spent nuclear fuel in the special air cooling containers instead of the common practice of submerging the fuel rods in pools of water.
Fuel stored in pools is cooled by circulating water with pumps, but the system can shut down if earthquakes and other disasters cut off the power supply. The water could then evaporate, leaving the spent fuel and radioactive substances exposed to air.
Electric power companies have shown a positive attitude toward the dry storage system because it would enable them to keep more spent fuel when the pools are filled close to capacity.
However, municipalities that host nuclear power plants have expressed strong concerns that the system will let utilities keep spent nuclear fuel at plant sites for prolonged periods.
NRA Chairman Shunichi Tanaka stressed the need for safety.
“It (dry cask storage) is much safer than storing fuel in pools,” he said.
The Great East Japan Earthquake and tsunami cut off power to Tokyo Electric Power Co.’s Fukushima No. 1 nuclear plant in March 2011. Three reactors melted down, and the cooling system would not work for more than 1,000 spent fuel assemblies in the pool in the No. 4 reactor building.
Fears arose that all water in the pool could evaporate. But emergency measures, including the pumping in of water, were taken to keep the fuel submerged.
Under the dry storage system, the fuel is sufficiently cooled in pools and placed in dedicated airtight cases. The special casks are then stored inside air-permeable facilities.
The NRA plans to promote use of casks that are currently used to transport spent nuclear fuel.
The containers have passed durability tests and can withstand falls from a height of 9 meters and high-temperature fires.
Dry storage containers are widely used in the United States and Europe.
But the use of dry casks has not spread in Japan because of the high hurdles that must be cleared. One requirement is that those containers must be stored in building that can withstand the strongest earthquake predicted in the area.
As a result, dry storage containers are used at only a few nuclear facilities in the country, such as Japan Atomic Power Co.’s Tokai No. 2 nuclear power plant in Ibaraki Prefecture.
According to the Federation of Electric Power Companies of Japan, a total of 15,000 tons of spent fuel is stored at 17 nuclear plants across Japan.
Seventy percent of their fuel pools and other storage facilities have been filled with spent fuel.
The R3 and R4 of the Genkai nuclear power plant, Pref. Saga, have met the new safety standards of the NRA. Restart announced at the end of summer.
As of today: Have met the safety standards, 10 reactors in 5 nuclear plant namely also Sendai R1, R2 – Takahama R1 to R4 – Mihama R3 – Ikata R3.
Two reactors have now been restarted: Sendai 1 and Ikata 3 (using MOX).
The Nuclear Regulation Authority formally decided Wednesday on the screening document certifying that the Nos. 3 and 4 reactors at Kyushu Electric Power Co.’s Genkai nuclear power plant in Saga Prefecture satisfied the country’s safety standards for their restart.
The latest decision made at an NRA regular meeting brings to 10 the number of reactors, at five nuclear power plants, that have satisfied the regulator’s new safety standards, introduced after the nuclear disaster at Tokyo Electric Power Company Holdings Inc.’s Fukushima No. 1 nuclear power plant in 2011. The two Genkai reactors are scheduled to be back online sometime in or after summer this year.
The Kyushu power company applied for a safety screening on those reactors in July 2013. At that time, the company anticipated an earthquake with an acceleration of up to 540 gal at the Genkai plant followed by tsunami of up to 3 meters high. However, the NRA deemed the simulation as “too optimistic” and the figures were raised to an acceleration of 620 gal with 4-meter-high tsunami.
In November last year, the NRA approved a draft document as the two reactors complied with the new standards. The NRA then solicited public opinions and received 4,200 comments, including concerns over possible earthquakes, but concluded that there was no problem with compliance.
With the formal decision being made on the Genkai plant, the focus for the restart has moved to an approval of a construction plan that maps out the specifications of related equipment for safe operation as well as whether it can obtain the consent of local governments for the restart.
So far, nuclear reactors that have passed the NRA’s screenings under the new standards are the Nos. 1 and 2 reactors at Kyushu’s Sendai power plant in Kagoshima Prefecture, the Nos. 1 to 4 reactors at Kansai Electric Power Co.’s Takahama plant and KEPCO’s No. 3 reactor at Mihama plant, both in Fukui Prefecture, and the No. 3 reactor at Shikoku Electric Power Co.’s Ikata plant in Ehime Prefecture. Currently, two reactors — Sendai plant’s No. 1 and Ikata’s No. 3 — are online.
The No. 3 reactor of the Mihama Nuclear Power Station in Mihama, Fukui Prefecture, is pictured in this photo taken from a Mainichi Shimbun helicopter on Nov. 12, 2016.
Another operation approval of aging nuclear reactor contradicts 40-year rule
The Nuclear Regulation Authority (NRA) has allowed Kansai Electric Power Co. to continue running the No. 3 reactor at its Mihama Nuclear Power Station in Fukui Prefecture beyond the 40-year limit.
This is the third nuclear reactor in the country that will have been allowed to continue to operate beyond the 40-year limit — following the No. 1 and 2 reactors at the Takahama plant also in Fukui Prefecture.
The move contradicts rules stipulating that nuclear reactors should be decommissioned after being operated for 40 years, in principle.
It had been viewed as extremely difficult to extend the lifespan of Mihama’s No. 3 reactor because of its old design and difficulties in improving the reactor’s quake resistance as the plant operator is required to largely increase the estimate of the scale of the maximum earthquake that could hit the plant.
As such, the NRA once hinted that it would discontinue examinations of the reactor to see if it meets the new regulatory standards.
However, Kansai Electric Power spent 165 billion yen on measures to enhance the safety of the reactor. The NRA increased its personnel to accelerate the examination of the plant, and managed to approve the continuation of its operation by the deadline.
Six aging nuclear reactors across the country are set to be shut down and decommissioned. Their operators voluntarily decided to decommission these reactors, whose outputs are small, considering the units’ cost-benefit performance.
However, if power companies apply for permission to extend the lifespan of nuclear reactors, the NRA will almost certainly grant permission.
The rules limiting the operation of a nuclear reactor to 40 years, in principle, was established with the aim of reducing Japan’s reliance on atomic power stations following the outbreak of the Fukushima nuclear crisis in March 2011. Both the NRA and power companies should go back to the fundamentals of the rules.
Operation extension approved for Mihama reactor
Japan’s nuclear regulator has said an aging reactor will be allowed to operate beyond its 40-year maximum life span.
The No.3 reactor at the Mihama nuclear power plant, on the Sea of Japan coast, has been given a 20-year extension. The Nuclear Regulation Authority made the unanimous decision on Wednesday.
The reactor, in Fukui Prefecture, went offline in March 2011 for a regular checkup and has not been restarted.
The Mihama reactor turns 40 years old later this year, and it will now be permitted to run until November 2036.
The Nuclear Regulation Authority heard evidence on Wednesday that the reactor’s pipes and electric cables are expected to meet required standards for up to 60 years since operations began in 1976.
Some members referred to a 2004 accident at the reactor in which 5 workers were killed after high-temperature steam leaked from a damaged pipe. They urged the operator, Kansai Electric Power Company, to keep checking for possible decay to the facility.
The reactor is the third in Japan to be granted an extension, after 2 reactors at the nearby Takahama plant were approved for restarts in June.
Kansai Electric said it will not restart operations until additional safety work has been completed, by March 2020 at the earliest. It said it believes the restart will be economically practical.
This May 2016 photo shows the stone wall of Kumamoto Castle that was damaged by the April earthquake.
A technique that estimates the scale of earthquakes announced by the Earthquake Research Committee in 2006 may be underestimating the size of earthquakes — a problem for the Nuclear Regulation Authority, which bases its earthquake resistance plans on the system.
Professor Kazuki Koketsu presented the results of his evaluation of the 2006 system at a research session of The Seismological Society of Japan on Oct. 5. Koketsu is a professor at the Earthquake Research Institute at The University of Tokyo and the head of the Subcommittee for Evaluation of Strong Ground Motion, part of the Earthquake Research Committee.
Koketsu compared the estimations of the 2006 technique and a 2009 method to the actual observed data from the magnitude 7.3 Kumamoto Earthquake in April.
While the 2009 technique predicted a magnitude of 7.0 to 7.2 for the active fault, the 2006 technique underestimated the possible magnitude as between 6.6 and 6.9. Koketsu concluded that the 2009 technique is more appropriate for estimating the scale of earthquakes.
However, the Nuclear Regulation Authority (NRA) still uses the estimates of the strongest possible tremor made by the 2006 system as the basis for examining earthquake resistance design plans for nuclear reactors.
In response to Koketsu’s presentation, a representative of the NRA stated at a press conference held on Oct. 5., “We will begin discussion over whether we should adopt the 2009 system after the Subcommittee for Evaluation of Strong Ground Motion has coordinated its views on the matter.”
The 2006 technique bases its estimates on both the estimated length and breadth of active faults. In 2009, the Earthquake Research Committee released a new system based mainly on the length of faults in order to calculate the expected magnitude of quakes on as many active faults as possible in a short amount of time. In Koketsu’s study, the 2006 system miscalculated the length and width of the faults involved in the Kumamoto earthquake, leading to the underestimation of the scale.
While both techniques appear side by side in the research committee’s manual, the committee’s national earthquake scale prediction map for quakes measuring at least lower-6 on the 7-point Japanese intensity scale estimated to occur within the next 30 years along active faults are all calculated using the 2009 system.
The Nuclear Regulation Authority (NRA) on July 27 concluded that there is no need to review the maximum possible earthquake estimate — known as the standard ground motion — for Kansai Electric Power Co.’s Oi Nuclear Power Plant in Fukui
The NRA reached the conclusion at a regular meeting after former acting NRA chairman Kunihiko Shimazaki pointed out that Kansai Electric had “underestimated” the calculated standard ground motion for its Oi plant. The NRA said that the result of Kansai Electric’s calculation was reasonable. The NRA then dismissed Shimazaki’s argument by saying that calculation methods other than the current one used for the Oi plant “have not reached a degree of scientific and technological maturity.”
Shimazaki had earlier suggested that the so-called “Irikura-Miyake method” used by Kansai Electric was the cause of the underestimated standard ground motion. The NRA’s secretariat checked the validity of other methods such as the “Takemura method,” but it concluded that ways of taking into account the “uncertainties” involved in predicting standard ground motions have not been established. Five NRA commissioners approved the secretariat’s verification results.
A string of issues over the calculations of standard ground motions raised questions about the NRA’s expertise.
After recalculating the estimated standard ground motion for the Oi plant using the “Irikura-Miyake method” — the same method used by Kansai Electric — the NRA secretariat found that the recalculated estimate was 356 gals, “gal” being a unit of acceleration. Its recalculation based on the “Takemura” method showed 644 gals. These two figures fell below Kansai Electric’s estimate of 856 gals. Therefore, the NRA secretariat determined that Kansai Electric’s figure was not “underestimated.” The NRA approved the secretariat’s findings on July 13.
On July 19, the NRA secretariat effectively withdrew its findings, saying that “They were unreasonable calculations.” Thus, it came to light that the NRA had confirmed the secretariat’s findings without verifying the validity of the calculations. It also came to light that the NRA had not grasped the detailed process of Kansai Electric’s calculation as the secretariat’s calculation result conflicted with that of Kansai Electric. The NRA approved Kansai Electric’s calculation of the standard ground motion in the autumn of 2014, but questions were subsequently raised about the way in which the screening was conducted.
Among the five NRA commissioners is a geologist, but there is no expert on ground motion. At a news conference on July 27, NRA Chairman Shunichi Tanaka acknowledged that his group was lacking expertise, saying, “That’s what we need to reflect on.” But when he met Shimazaki on July 19, Tanaka bluntly said, “There is no room for listening to outside experts nor am I in a position to do so.” As the biggest lesson learned from the Fukushima nuclear crisis ought to be that the most up-to-date expertise should be reflected in safety measures, the NRA is urged to listen to arguments and suggestions from outside experts.
In March this year, Tokyo Electric Power Co. (TEPCO) began work on a subterranean wall of frozen soil mainly on the seaward side of the disaster-stricken Fukushima No. 1 nuclear plant, with most of another wall on the landward side begun in June. The purpose of the barriers is to stop the flow of groundwater into the plant buildings — a problem that has resulted in enormous volumes of contaminated water. However, three months since the freezing process began, TEPCO is ominously silent on the ice wall’s effectiveness, and the plan is quickly approaching its do-or-die moment.
The problem itself is simply put. Every day, some 850 metric tons of groundwater flows down from the mountains and under the Fukushima No. 1 plant property. Some of the water collects in the shattered reactor buildings, coming into contact with melted nuclear fuel and other radioactive substances and becoming heavily contaminated. TEPCO needs to stop the groundwater from getting into these buildings.
In September 2015, the utility started digging a chain of wells called subdrains to catch and drain the groundwater. This is just one of many countermeasures tried so far, including the ice wall. Work on the latter began in June 2014, and eventually 1,568 pipes were sunk along a 1.5-kilometer perimeter around the No. 1-4 reactors and turbine buildings. The plan calls for coolant chilled to minus 30 degrees Celsius to be pumped into the pipes, freezing the soil around them to a depth of about 30 meters and creating a solid barrier.
“Ice walls are often used in public works projects, but the one at the Fukushima No. 1 nuclear plant is by far the largest ever tried,” says Mie University associate professor Kunio Watanabe. When building a tunnel, for example, ice walls are used to prevent groundwater from flowing into the construction area after the bedrock has been fractured. In Japan, the method has been used on some 600 such projects since 1962. The largest ice wall ever created was about 37,700 cubic meters, during construction of a subway line in Tokyo. The Fukushima plant ice wall is nearly double that, at about 70,000 cubic meters.
TEPCO tested the method in April 2015, freezing one section of the subterranean wall. To stop contaminated groundwater from flowing into the ocean, the utility started injecting coolant in the pipes on the seaward side and part of the landward wall in late March in an attempt to create about an 820-meter-long subterranean barrier — or 55 percent of the eventual total length. Saying that the temperatures were dropping according to plan, the utility started freezing operations on most of the remaining landward section at the beginning of June, and now only seven sections totaling 45 meters on the landward side are left.
TEPCO has stated that “the ice wall is going according to plan.” However, the Nuclear Regulation Authority (NRA) has pointed out that the volume of groundwater collecting in waterfront wells has not decreased, casting doubt on TEPCO’s claim.
At a meeting this month, NRA committee member Toyoshi Fuketa stated, “This is not a wall in a true sense. Perhaps it’s more akin to a bamboo screen, with groundwater trickling through the gaps.” TEPCO has responded that the quick flow of the groundwater likely makes it hard to freeze the soil in some places, and it is proceeding with work to create cement barriers to slow the water down.
There are also worries that the large volumes of highly contaminated water already collecting in the reactor and turbine buildings could leak into the environment if only the landward ice wall proves effective and the seaward wall has gaps. While TEPCO is looking to expand the ice wall, the NRA has not altered its stance that it must first confirm the effectiveness of the freezing operations already undertaken. The ice wall has already cost 34.5 billion yen in government funds.
The Nuclear Regulation Authority (NRA) concluded on June 29 that three nuclear power plants were guilty of “level 2” safety violations by breaching standards on placement of power cables
A “level 2” violation is the second heaviest violation in the NRA’s four-tier list.
The NRA deemed that new safety standards regarding power cable installation had been violated at Tokyo Electric Power Co. (TEPCO)’s Fukushima No. 2 Nuclear Power Plant in Fukushima Prefecture, Tohoku Electric Power Co.’s Onagawa plant in Miyagi Prefecture and Chubu Electric Power Co.’s Hamaoka plant in Shizuoka Prefecture. TEPCO’s Kashiwazaki-Kariwa nuclear station in Niigata Prefecture was earlier found to have committed a level 2 violation.
The NRA is set to carry out additional safety inspections on the three recently named nuclear plants as well as at the Kashiwazaki-Kariwa plant to check whether problems at these plants have been corrected.
Violation of power cable-related safety standards has been found at 19 reactors within 6 nuclear plants, as well as at Japan Nuclear Fuel Ltd.’s spent fuel reprocessing facility in Aomori Prefecture. Subsequent inspections by power companies and the NRA found such violations at a total of 5,344 locations on the premises of those nuclear plants. Of these, violations at the four nuclear stations including the Kashiwazaki-Kariwa plant were deemed particularly malicious as utilities failed to check their power cable placing and continued to violate the safety standards even after regulations for power companies to conduct in-house inspections on power cable installation were introduced in October 2003.
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