The government’s Nuclear and Industrial Safety Agency (NISA) released part of an unedited severe accident manual for the Fukushima No. 1 Nuclear Power Plant on Oct. 24, revealing that Tokyo Electric Power Co. (TEPCO) had not envisioned the possibility of all power sources at the nuclear complex being lost.

TEPCO, the operator of the crippled nuclear power plant, had earlier submitted to a special House of Representatives committee largely blacked-out emergency operation manuals for the Fukushima nuclear facility. The manuals were in fact used when the Great East Japan Earthquake and ensuing tsunami struck the nuclear complex. On Oct. 24, NISA released part of an unedited manual after submitting it to the same lower house panel. The manual revealed the fact that there was no operational manual that envisioned a loss of all power sources needed to activate emergency condensers and back-up water injection devices to cool down nuclear reactors. The revelation highlights flaws in TEPCO’s contingency plan in the event of a loss of power sources.

What was released on Oct. 24 is part of an emergency operation manual for the No. 1 reactor at the Fukushima nuclear power plant. It shows methods of cooling down nuclear fuels as well as ways of “venting” in order to hold down pressure in the containment vessel. NISA also released documents prepared by TEPCO that compare the operation manual and what was actually done when the crisis broke out.

According to the documents, all power sources were lost due to the effects of tsunami at 3:37 p.m. on March 11. As a result, whether valves for emergency condensers were operating properly could not be confirmed. Because the manual did not envision possibilities of all power sources, including batteries, being lost in the event that emergency generators and external power sources were lost, the manual itself was in fact useless when all power sources were actually lost on that day.

Mainichi Shimbun , October 25, 2011
http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/10/25/20111025p2a00m0na007000c.html

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 TEPCO failed to act on 10% probability assessment for worst-case tsunami

TOKYO (Kyodo) — Tokyo Electric Power Co. estimated in 2006, using a new calculation method at the time, that the probability of a worst-case tsunami hitting the Fukushima Daiichi nuclear power plant was around 10 percent at the most over a span of 50 years, but the utility did not take measures based on the assessment, a nuclear energy expert at the company said Tuesday.

The expert told Kyodo News that the assessment showed the probability of a major tsunami hitting the plant in Fukushima Prefecture had “dramatically increased” and the company should have taken countermeasures as soon as possible.

Although the utility known as TEPCO describes the 2006 probability assessment as based on experimental analysis and says the figure was “small enough” in a draft report of an in-house panel investigating the nuclear crisis at the plant, experts at the utility as well as the central government are questioning TEPCO’s inaction.

The TEPCO expert who has long been involved in the field of nuclear energy said the 2006 assessment was only shared among people in the field and not disseminated to other relevant sections in the company.

The expert surmised that TEPCO did not take countermeasures because it did not want to spark concern among residents living near the plant and was worried about the possible impact on other electric power companies.

Under the Probabilistic Safety Assessment method, the probability of a tsunami of more than 5.7 meters hitting the Fukushima Daiichi plant in 50 years — the general operating life of a nuclear reactor — was around 10 percent at most and the probability of a tsunami of more than 10 meters that could cause a nuclear meltdown striking the plant was less than 1 percent.

The latter probability far surpasses the International Atomic Energy Agency’s safety standards that say the possible occurrence of a nuclear meltdown should be less than once in 100,000 years.

Kyodo Press, October 19, 2011
http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/10/19/20111019p2g00m0dm025000c.html

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TEPCO Links March 15 Blast Sound to No. 4 Reactor

Tokyo, Oct. 21 (Jiji Press)—Tokyo Electric Power Co. concluded Friday that an explosion heard on the early morning of March 15 at the ravaged Fukushima No. 1 plant resulted from a blast at the No. 4 reactor building, not at the No. 2 reactor.

TEPCO reached the conclusion based on its estimation using the data of seismometers at five locations in the plant. The power utility estimates that the vibratory motion detected at 6:12 a.m. on that day originated from the No. 4 reactor.

The company assumes that the explosion at the No. 4 reactor of the plant knocked out by the March 11 quake and tsunami was caused by hydrogen that streamed from the No. 3 reactor, which suffered a meltdown.

The Japanese government said in a report submitted to the International Atomic Energy Agency in June that a loud impact sound possibly from a hydrogen explosion was confirmed at the No. 2 reactor.

Since the pressure inside the No. 2 reactor suppression pool, which holds water and steam from the reactor core, fell sharply, TEPCO will examine whether the chamber suffered some crack that did not create an explosion sound.

Jiji Press, October 21, 2011
http://jen.jiji.com/jc/eng?g=eco&k=2011102101003

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 Fukushima assembly adopts petition for decommissioning local reactors

FUKUSHIMA (Kyodo) — The Fukushima prefectural assembly adopted on Thursday a petition calling for decommissioning all 10 reactors at the prefecture’s two nuclear power plants in the aftermath of the nuclear disaster at one of them following the March earthquake and tsunami.

The request over Tokyo Electric Power Co.’s crisis-hit Fukushima Daiichi plant, where four of six reactor units were damaged, and nearby Fukushima Daini plant with four reactors goes further than statements by the utility and the central government, which have yet to unveil their plan on the future of the plants’ six undamaged reactors.

Fukushima Gov. Yuhei Sato said the assembly’s move “really has weight” and reiterated his view that it is impossible for the Daiichi and Daini plants to resume operations.

Among assemblies of the 13 Japanese prefectures home to nuclear power stations, the Fukushima assembly is the first to approve a request to decommission such plants.

The assembly passed the petition, filed by a pro-Japanese Communist Party citizens group, at a plenary session ahead of the Nov. 20 Fukushima prefectural assembly election. All the parties and groups in the assembly have already called for a departure from nuclear power.

Of 53 assembly members who attended Thursday’s meeting, five left the meeting room just prior to the adoption and the 48 others who remained were all in favor of the petition.

One of those who left the room said following the session, “I felt that calling for an immediate decommissioning at a time when the outlook for employment is uncertain would strip evacuated residents of the opportunity to return to their homes.”

The petition says, “Citizens in Fukushima Prefecture have been fighting against things invisible and horrible, and have spent time amid fears,” and almost all the people hope for denuclearization.

It also says people with children are particularly concerned about the future effects of radiation on children.

The central government and plant operator Tokyo Electric have already said the four troubled reactors at the Fukushima Daiichi plant will be decommissioned.

But they have yet to say whether the remaining two reactors at the Fukushima Daiichi plant and the four reactors at the Fukushima Daini plant will be decommissioned.

The citizens group filed the petition with the prefectural assembly during its regular session in June. But the assembly had postponed taking a vote on the petition.

Kyodo Press, October 21, 2011
http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/10/21/20111021p2g00m0dm030000c.html

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Outer covering complete at Fukushima Daiichi plant’s No. 1 reactor

TOKYO (Kyodo) — Tokyo Electric Power Co. said Friday that it has finished installing a covering over the No. 1 reactor at its crippled Fukushima Daiichi nuclear power plant in Fukushima Prefecture.

The 54-meter-high covering, with a ventilation system equipped with filters that remove radioactive materials, will reduce the release of radioactive substances into the air by roughly 99 percent, according to the plant operator.

Work to install the covering, 47 meters wide and 42 meters deep, began in August at the reactor, which was badly damaged by a hydrogen explosion after the plant was crippled by the March 11 earthquake and tsunami.

Debris is still being removed from the adjacent Nos. 3 and 4 reactors, which were also damaged by hydrogen explosions. The operator will consider whether to install similar coverings for the reactors.

Also Friday, Tokyo Electric began full operations at the No. 2 reactor of equipment designed to remove radioactive materials from the reactor’s containment vessel. The building covering the No. 2 reactor suffered only minor damage though the unit is assumed to have suffered a meltdown at its core.

Kyodo Press, October 29, 2011
http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/10/29/20111029p2g00m0dm011000c.html

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