World AIDS Day.
Went to an event here in Japan to commemorate it. For a city this size, I think it was a rather good turnout on a cold December evening.
On the way home, the taxi driver said there is still no snow atop Mt. Fuji, but there usually is. Something odd for this time of year, not having snow this late into the year….
And now, for a few news articles:
Melted nuclear fuel eroded reactor container by up to 65 cm: TEPCO
TOKYO (Kyodo) — The operator of the crippled Fukushima Daiichi nuclear power plant said Wednesday that the concrete base of the No. 1 reactor container had been eroded by up to 65 centimeters when the fuel inside melted, although the steel container itself was left intact.
According to Tokyo Electric Power Co.’s analysis, all of the fuel inside the No. 1 reactor melted after cooling functions failed in the wake of the March 11 earthquake and tsunami, with a substantial amount of the fuel melting through the base of the reactor pressure vessel and dropping into the outer primary container.
If the erosion had expanded another 37 cm, the damage would have reached the steel wall, according to the utility known as TEPCO.
As for the Nos. 2 and 3 reactors, which also experienced meltdowns, the amount of fuel that dropped to the bottom of the pressure vessel is estimated to be around 60 percent.
The bottom of the two reactors’ pressure vessels is unlikely to have been damaged on a large scale. But if the fuel had melted through the vessels, the primary container of the No. 2 reactor could have been eroded by 12 cm and that of the No. 3 reactor by 20 cm, TEPCO said.
Currently, the melted fuel inside the Nos. 1 to 3 reactors is believed to be cooled by water injection and no further erosion is occurring, it said.
(Mainichi Japan) November 30, 2011
Nuclear experts back Tepco meltdown simulation findings
While disputing the details, nuclear experts basically concurred Thursday with the findings of a computer simulation run by Tokyo Electric Power Co. that concluded nuclear fuel in reactors at the Fukushima No. 1 plant had melted into but not breached their containment vessels.
The announcement by Tepco Wednesday was the latest indication that three overheated cores at the plant had not penetrated their concrete and steel containers and melted deep into the earth — a worst-case scenario China syndrome.
However, there is reason to dispute Tepco’s claim that the nuclear fuel in reactor 1 came within 37 cm of melting through surrounding concrete and reaching the containment vessel’s steel shell, said Kenji Sumita, a professor emeritus of nuclear engineering and a former deputy chief of the Nuclear Safety Commission.
“There are many computer simulation methods. I want to see simulations conducted by organizations other than Tepco,” Sumita said.
Commenting on the unknown margin of error in Tepco’s simulation, “I don’t believe the fuel got as close as 2 or 3 cm to the steel shell, but I am not sure how credible their details are,” he said.
However, Sumita claimed it was certain nuclear fuel had not escaped the containment vessels because no radioactive substances have leaked into the groundwater near the reactors.
Toshihiro Yamamoto, a specialist in reactor safety management at Kyoto University Research Reactor Institute, pointed out the difficulty of collecting data to base the computer simulation on.
“You cannot have experimental meltdowns. Thus the simulation will have to rely on many assumptions,” he said.
Meanwhile, Hiromi Ogawa, a former engineer at Toshiba Corp. who managed its nuclear power generation project, effectively guaranteed the credibility of the simulation.
“The simulation referred to lots of data collected from many experiments, and thus I think the results are very precise,” he said. “Still, the situation will have to be confirmed visually.”
According to Tepco’s simulation, the nuclear fuel in reactor 1 probably penetrated through as much as 65 cm of the containment vessel’s concrete floor, reaching as close as 37 cm to the vessel’s outer steel shell, the last line of defense.
Reactor 1 suffered the worst damage in the accident triggered by the March 11 earthquake and tsunami.
The findings also suggest that the nuclear fuel in reactor 2 melted through 12 cm of the vessel’s concrete floor, while fuel from reactor 3 burned through 20 cm.
Mr.Koide from Kyoto uni “Tepco’s assumption is baseless”
On the radio program ,”Tanemaki journal” on MBS , Mr.Koide from Kyoto university stated that Tepco’s assumption to tell there is still 37 cmto go has no basis.
Mr.Koide has been warning melt-out since May,yet he admitted that he can not assume where the melted fuel is now because human-beings have never gone through such a crisis.
He estimates the melted fuel may stop about 5~10 meters deep under ground because melted fuel becomes larger as it contains concrete ,the body of container vessel etc. It starts from 2800C,but the heat will decrease gradually.
However,he admits even this assumption does not have scientific basis.
Mr.Koide states,he suspects the container vessel has already been broken. Tepco assumes there is still 37cm to the wall of container vessel,but it is baseless.
They need data to assume ,such as temperature ,pressure ,etc ,but there is no data to consider.
He does not know on what “facts” they based on to assume the situation.
Even in Three mile island ,they took 7 years to confirm melt down happened.
It is considered to take much longer to know what was happening ,and it would take even longer to settle it down.
Fukushima I Nuke Plant Reactor 1: TEPCO and NHK’s Obfuscation on Corium in the Concrete
In the first post on the subject, I translated what NHK reported:
It has been discovered by TEPCO’s analysis that the significant amount of Reactor 1’s melted fuel pierced through the steel Reactor Pressure Vessel and dropped onto the Containment Vessel, then melted the concrete at the bottom of the CV. It is estimated that the melted fuel may have eaten into the concrete to maximum 65 centimeters deep.
Maximum 65 centimeters deep from the bottom of the concrete floor, right?
Well no. It’s 65 centimeters from the bottom of the deep groove on the concrete floor.
And neither NHK nor TEPCO would bother to tell you how deep the groove is.
At least, NHK Kabun (NHK’s last remaining conscience, as far as I’m concerned) tweeted and gave the link to its blog post, where NHK’s analysis of the concrete-eating corium is shown with the screenshots from the program:
The text below the screen says: “In the worst case, it [the corium] may have reached 65 centimeters from the surface of the concrete. Where the concrete is the thinnest, it may have reached within 37 centimeters from the steel plate [of the Containment Vessel].
The “surface of the concrete” turns out to be the surface of the bottom of the groove that is X centimeter deep.
It’s one thing for TEPCO’s Matsumoto to say “surface of the concrete” (as we’ve gotten used to hearing technically correct explanations from him), but for NHK to say so while showing the graphics indicating it is the surface of the bottom of the groove is at once deceptive and covering its behind. NHK can now say “We showed it in the graphics that it was 65 centimeters from the bottom of the groove, and people should have paid attention.”
(I’m asking NHK Kabun if they know the depth of the groove, but does anyone know or have access to a schematic diagram with measurement?)
Well, it does look like the Institute of Applied Energyis more right than TEPCO in saying the corium has eaten 2 meters into the concrete. And perhaps people like Hiroaki Koide of Kyoto University and the engineers who designed the reactors at Fukushima I Nuke Plant may be more right than the Institute of Applied Energy, and the corium has indeed escaped the Containment Vessel long time ago.
As the wiki entry on “corium” states, the corium can eat into the concrete 1 meters in the first one hour, and several centimeters per hour afterwards:
The fast erosion phase of the concrete basemat lasts for about an hour and progresses into about one meter depth, then slows to several centimeters per hour,and stops completely when the melt cools below the decomposition temperature of concrete (about 1100 °C). Complete melt-through can occur in several days even through several meters of concrete; the corium then penetrates several meters into the underlying soil, spreads around, cools and solidifies. During the interaction between corium and concrete, very high temperatures can be achieved.
Fukushima I Nuke Plant: 1.6 Million Bq/Kg of Cesium from Ocean Soil In Front of Water Intake for Reactors
TEPCO’s worst-case scenario (here and here) pales in comparison with the analysis by the Institute of Applied Energy, also presented on November 30 at the workshop held by the Nuclear and Industrial Safety Agency.
The corium has long escaped the Reactor Pressure Vessel as admitted by TEPCO and the government. There are experts (like Hiroaki Koide) who have suggested the corium may have already left the Containment Vessel of Reactor 1, and TEPCO itself said back in May that Reactor 1 CV may have a 7-centimeter hole. Now the company says the coriummay have eaten into the concrete floor of the CV to about 65-centimeter deep….
Study Shows Worse Picture of Meltdown in Japan
The findings are the latest in a series of increasingly grave scenarios presented by Tepco about the state of the reactors. The company initially insisted that there was no breach at any of the three most-damaged reactors; it later said that there might have been a breach, but that most of the nuclear fuel had remained within the containment vessels.
“This is still an overly optimistic simulation,” said Hiroaki Koide, an assistant professor of physics at the Kyoto University Research Reactor Institute, who has been a vocal critic of Tepco’s lack of disclosure of details of the disaster. Tepco would very much like to say that the outermost containment is not completely compromised and that the meltdown stopped before the outer steel barrier, he said, “but even by their own simulation, it’s very borderline.”
“I have always argued that the containment is broken, and that there is the danger of a wider radiation leak,” Mr. Koide said. “In reality, it’s impossible to look inside the reactor, and most measurement instruments have been knocked out. So nobody really knows how bad it is.”
Read the entire article at:
Hashimoto’s victory sets stage for nuclear power showdown with Kepco
OSAKA — A battle is brewing between newly elected Osaka Mayor Toru Hashimoto and Kansai Electric Power Co. over the future of nuclear power, electricity distribution and alternative energy.
With the city’s 8.9 percent stake making it Kepco’s largest shareholder, Hashimoto has vowed to use the utility’s shareholders’ meeting next June as the venue to make sweeping proposals that would reduce Osaka’s and Kansai’s dependence on nuclear power — the source of 51 percent of the region’s electricity in 2010.
“Reducing dependence on nuclear power is the consensus of Osaka Ishin no kai (One Osaka),” Hashimoto said after his victory Sunday night, warning the power company that it was not just his personal goal but that of his group, which now controls the mayor’s office, the governor’s office, and the majority of the prefectural assembly.
Osaka Ishin no kai’s platform also calls for a wider electricity distribution system with more competitors. Hashimoto and Osaka Ishin no kai are also pushing measures and policies that promote local production and consumption of energy through increased use of solar, small-scale hydropower and biomass plants.
“The city will use its position as a Kansai Electric shareholder to promote these goals,” the platform says.
But these reform plans are vigorously opposed by Kepco, especially Hashimoto’s attempts to greatly reduce nuclear power.
“Nuclear power is an important source as a stable supply of energy,” Kansai Electric President Makoto Yagi said at a press conference earlier this week.
Kepco has also long fought efforts by past mayors and other energy companies to switch to cleaner or renewable energy sources, such as natural gas. After the March 11 quake and tsunami, Hashimoto, then governor of Osaka, called for a gradual phaseout of nuclear plants in favor of renewable energy, especially solar power.
As for Hashimoto’s proposal to increase the number of players in the electricity distribution market, Yagi said the most appropriate way to deliver electric power was for one business responsible for the supply to have an integrated system of operations for generating and distributing the product.
“At times of stringent supply and demand, there’s not always a relation between selling electric power at a high or low cost,” Yagi said, adding he wanted a thorough discussion on the merits and demerits of Hashimoto’s plans.
Hashimoto has said his plans to ween Osaka off nuclear power are gradual and has indicated he would favor restarting the Kepco reactors currently shut down.
Kansai Electric’s economic and political influence in Osaka is huge, and even though the city is its top shareholder, the new mayor could find it difficult to force the utility to shut the plants down once they’re turned back on.
On the other hand, opinion polls in Osaka show a majority of city and prefectural residents support less nuclear power.
Adjacent prefectures like Shiga, which sits beside Fukui Prefecture where Kepco’s 11 nuclear power plants are located, support Hashimoto’s efforts out of concern for what might happen to Lake Biwa, the largest freshwater body in the nation, in the event of a major accident at one of the plants.
TEPCO May Give Up N-Reactor Construction in Northern Japan
Tokyo, Dec. 1 (Jiji Press)–Tokyo Electric Power Co. <9501> may give up an ongoing project to construct a nuclear power reactor in Aomori Prefecture, northern Japan, informed sources said Thursday.
The company, known as TEPCO, is struggling to secure funds for the project because of the huge costs to pay compensation to those affected by the accident at its Fukushima No. 1 nuclear plant, the sources said.
If TEPCO abandons the project, other projects may be affected, including one to build a third reactor at Chugoku Electric Power Co.’s <9504> Shimane plant in Matsue, western Japan, and one to construct a nuclear plant in Oma, Aomori, for Electric Power Development Co. <9513>, or J-Power.
Under the current plan, TEPCO will build two reactors in the village of Higashidori with construction work for the first reactor starting in January.
The No. 1 reactor will have an output capacity of 1,385,000 kilowatts, one of the biggest nuclear reactors in Japan. Its operations are scheduled to begin in March 2017.
Study shows deeper meltdown at Japan nuke reactor
Findings will not change stabilization efforts
Updated: Wednesday, 30 Nov 2011, 12:53 PM EST
Published : Wednesday, 30 Nov 2011, 12:53 PM EST
- MARI YAMAGUCHI,Associated Press
TOKYO (AP) — Radioactive debris from melted fuel rods may have seeped deeper into the floor of a Japan’s tsunami-hit nuclear reactor than previously thought, to within a foot from breaching the crucial steel barrier, a new simulation showed Wednesday.
The findings will not change the ongoing efforts to stabilize the reactors more than eight months after the Fukushima Dai-ichi plant was disabled, but they harshly depict the meltdowns that occurred and conditions within the reactors, which will be off-limits for years.
The plant operator Tokyo Electric Power Co. said its latest simulation showed fuel at the No. 1 reactor may have eroded part of the primary containment vessel’s thick concrete floor. The vessel is a beaker-shaped steel container, set into the floor. A concrete foundation below that is the last manmade barrier before earth.
The fuel came within a foot of the container’s steel bottom in the worst-case scenario but has been somewhat cooled, TEPCO’s nuclear safety official Yoshihiro Oyama said at a government workshop. He said fuel rods in the No. 1 reactor were the worst damaged because it lost cooling capacity before the other two reactors, leaving its rods dry and overheated for hours before water was pumped in.
The nuclear crisis following the March 11 earthquake and tsunami caused massive radiation leaks and the relocation of some 100,000 people.
Another simulation on the structure released by the government-funded Japan Nuclear Energy Safety Organization, or JNES, said the erosion of the concrete could be deeper and the possibility of structural damage to the reactor’s foundation needs to be studied.
JNES official Masanori Naito said the melting fuel rods lost their shape as they collapsed to the bottom of the vessel, then deteriorated into drops when water pumping resumed, and the fuel drops spattered and smashed against the concrete as they fell, Naito said.
TEPCO and government officials are aiming to achieve “cold shutdown” by the end of the year — a first step toward creating a stable enough environment for work to proceed on removing the reactors’ nuclear fuel and closing the plant altogether.
The government estimates it will take 30 years or more to safely decommission Fukushima Dai-ichi.
Wednesday’s simulations depict what happened early in the crisis and do not mean a recent deterioration of the No. 1 reactor. Oyama said, however, the results are based only on available data and may not match the actual conditions inside the reactors, which cannot be opened for years.
Some experts have raised questions about achieving the “cold shutdown,” which means bringing the temperature of the pressure vessel containing healthy fuel rods to way below the benchmark 100 Celsius (212 Fahrenheit). They say the fuel is no longer there and measuring the temperature of empty cores is meaningless, while nobody knows where and how hot the melted fuel really is.
Kiyoharu Abe, a nuclear expert at JNES, said it’s too early to make a conclusion and more simulations should be done to get accurate estimates.
“I don’t think the simulation today was wrong, but we should look at this from various viewpoints rather than making a conclusion from one simulation,” Abe said. “It’s just the beginning of a long process.”