19/04 TEPCO must provide more solid information on recovery from nuclear crisis

In this image released Saturday, April 16, 2011, by Tokyo Electric Power Co., top of the container of the nuclear reactor, painted in yellow, of Unit 4 at the Fukushima Dai-ichi Nuclear Plant is observed from its side with a T-Hawk drone Friday, April 15, 2011 in Okuma, Fukushima Prefecture, northeastern Japan. (AP Photo/Tokyo Electric Power Co.)

Layout of cooling systems at Fukushima No.1 Power Plant. (Mainichi)

Just when will people be able to breathe a sigh of relief that the crisis at the Fukushima No. 1 Nuclear Power Plant is over? The lives of residents living around the plant are hanging on an answer to this question. For local farmers and businesses, it is a matter of life and death.

Tokyo Electric Power Co. (TEPCO)'s announcement of a schedule for bringing the disaster under control was significant. Unfortunately, however, the schedule lacks concrete details. Rather than serving as a plan to solve the crisis it is a display of just how many difficulties remain.

Radioactive materials continue to leak from the plant's reactors, but the source of the leaks and the exact times materials have leaked remain unclear. To control the leaks, the reactors must be cooled to under 100 degrees Celsius and stabilized -- a process known as a "cold shutdown."

TEPCO's schedule says it will take six to nine months for reactors to be brought to a cold shutdown. But when looking squarely at the schedule, it seems unlikely that the process will be completed within this time frame. A year is probably more realistic.

In this image released by Tokyo Electric Power Co., a radio-controlled PakBot robot opens a door inside the reactor building of Unit 2 as it is monitored with another Pakbot from behind during inspection of the tsunami-damaged facilities at the Fukushima Dai-ichi Nuclear Power Plant Monday, April 18, 2011 in Okuma, Fukushima Prefecture, northeastern Japan.

The power company says that it will first drench the containment vessels of the plant's No. 1 and 3 reactors -- including the pressure vessels -- in water. But if the containment vessels are damaged, water will leak out. Drenching the containment vessels in water is something that has not been done before when handling a nuclear power plant accident, and workers must be well aware of the strength of containment vessels.

But even if this first stage goes well, a cold shutdown will not immediately follow. Water must be circulated in a closed loop to continually remove heat from the nuclear fuel.

The containment vessel of the No. 2 reactor has almost certainly been damaged. Plans to patch up the damage have been drawn up, but radiation levels around the reactor must first be reduced. Because of this, it remains unclear if such work will actually be possible. And even if another device to continually remove heat from the fuel is built, unforeseen problems could occur.

TEPCO should form plans to address each of these issues while taking alternative solutions into consideration, and produce a concrete appraisal of the situation. In doing so, it is vital to confirm the state of damage to the nuclear reactors and pipes. Which parts are damaged and what is the extent of the damage? Workers may not be able to view every part up close, but TEPCO should provide solid information on each possibility.

Overall there has been a lack of information regarding the nuclear power plant. We still don't know the amount of radioactive materials that continue to leak from the power plant. TEPCO's schedule says it will expand and enhance its monitoring of radiation within three months, but the company should make an effort to speed this process up and do its job of releasing information. Otherwise, residents will find it difficult to draw up plans for their futures.

This Sunday, April 10, 2011 photo released by Tokyo Electric Power Co. (TEPCO) shows orange colored floats suspending"silt fence," that was installed under water to help prevent contaminated water from spreading outside the Fukushima Dai-ichi nuclear power plant's bay. (AP Photo/Tokyo Electric Power Co.)

The process of bringing a nuclear power plant accident under control must be measured in years, not months. The work to achieve a solution must be shared, and a system to handle the crisis over the long term must be developed. The release of detailed information will form the pillars of these efforts.

Click here for the original Japanese story

(Mainichi Japan) April 19, 2011

19/04 TEPCO aims for cold shutdown in 6-9 months, but no guarantees

2011/04/19

TEPCO Chairman Tsunehisa Katsumata, right, and Executive Vice President Sakae Muto discuss the company's strategy to deal with the nuclear crisis on April 17. (Hiroshi Kawai)

Editor's note: We will update our earthquake news as frequently as possible on AJW's Facebook page:http://www.facebook.com/AJW.Asahi. Please check the latest developments in this disaster. From Toshio Jo, managing editor, International Division, The Asahi Shimbun.

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Tokyo Electric Power Co. has presented a two-stage scenario to stabilize the crippled Fukushima No. 1 nuclear power plant, but it is unclear whether its goals can be achieved as scheduled.

At least six months will be needed to achieve a cold shutdown of the reactors, which means bringing core temperatures under 100 degrees, according to the company's road map announced April 17.

In the first step, which will take about three months, TEPCO plans to cool the reactors in a stable manner and cap the amount of radioactive materials released.

In the second step, expected to be completed in six to nine months, the company aims to achieve cold shutdown and substantially reduce the amount of radioactive materials.

Industry minister Banri Kaieda said April 17 that the government plans to decide whether evacuees who were living in areas from around the Fukushima plant can return home after TEPCO's second step ends in six to nine months.

The government plans to review evacuation zones at that time after consulting with the Nuclear Safety Commission of Japan.

But TEPCO Chairman Tsunehisa Katsumata suggested the road map is only a list of all conceivable measures to deal with the crisis.

"There is no guarantee that we will be able to carry out the plan 100 percent," he said April 17. "We want to start with whatever we can do and cool the reactors successfully."

The key goal is to stabilize the reactors and storage pools for spent fuel rods, which have been releasing radioactive materials.

According to TEPCO, the risk of hydrogen explosions continues at reactors No. 1, 2 and 3, which have been cooled just enough to keep temperatures from rising to dangerous levels.

Nitrogen has been injected into the No. 1 reactor's containment vessel. In the first step of the road map, it will also be injected into the No. 2 and 3 reactors.

Water will also be poured into the containment vessels to cool the pressurized vessels that contain the fuel rods in a stable manner.

In the second step, TEPCO aims to restart circulating cooling systems to achieve a cold shutdown of the reactors.

Radioactive steam is still leaking from the containment vessels at the No. 1 and 3 reactors. TEPCO must locate and plug the leaks before the containment vessels are filled with water.

According to TEPCO, the No. 2 reactor will require additional work because its containment vessel was damaged and highly radioactive water is still flowing out.

While the company plans to close the damaged parts with cement, identifying those parts will be difficult.

In addition, the suppression pool connected to the containment vessel was likely damaged in a hydrogen explosion. Large amounts of highly radioactive water will flow into the ocean if water is poured into the containment vessel.

TEPCO therefore plans to seal the areas around the suppression pool with cement to prevent water leakage.

TEPCO aims to restore regular circulating cooling systems for the fuel storage pools at reactors No. 1, 3 and 4, where pumping trucks have been pouring in water from the outside.

A normal cooling system is already in operation at the No. 2 reactor.

According to TEPCO, the No. 4 reactor's fuel storage pool is vulnerable to earthquakes because of damage to the lower sections of the walls of the reactor building that support the pool.

In the first step, concrete supports will be installed at the bottom of the storage pool to bolster its anti-quake strength. The cracks in the lower parts of the walls will also be sealed.

TEPCO said it cannot yet tell when work can begin on anti-quake reinforcements.

In the road map's second step, a circulating cooling system will be restored while water trucks are deployed to pour water into the pool.

Over the midterm, TEPCO hopes to remove fuel rods from the pool, but specific methods to safely remove and store the damaged fuel rods have yet to be worked out.

The road map also aims to contain the release of radioactive materials into the atmosphere and the ocean.

In the first step, tanks and other facilities will be installed to store highly radioactive water found in the basements of the turbine buildings and outdoor trenches.

In the second step, the reactor buildings will be covered with special sheets.

An estimated 60,000 tons of highly radioactive water is in the basements of the turbine buildings alone.

TEPCO plans to move the contaminated water to a 30,000-ton central waste processing facility at the plant and install temporary tanks to store 12,000 tons by late April.

The water will also be moved to an offshore floating structure provided by the Shizuoka city government that can hold 10,000 tons.

The company also plans to set up a water treatment facility to remove radioactive materials using filters and flocculation agents.

19/04 Challenges abound to control crippled reactors

The Yomiuri Shimbun

Can Tokyo Electric Power Co. bring the four troubled reactors at its Fukushima No. 1 nuclear power plant under control within six to nine months as it announced Sunday? What challenges must it overcome before achieving its avowed goals?

Under the announced timetable, TEPCO aims to bring the crippled reactors to a stable condition known as a "cold shutdown"--a situation in which water temperatures inside the reactors are stabilized below 100 C--within six to nine months.

It will take this amount of time to achieve cold shutdown because the reactors, fuel rods and containment vessels are all in terrible conditions, experts said.

In the aftermath of a series of accidents at the Fukushima Prefecture power plant that was triggered by the March 11 earthquake and a massive tsunami, TEPCO studied measures such as purifying ever-increasing amounts of contaminated water and using it to cool the reactors and cooling water inside the reactors through heat exchangers by running seawater through narrow pipes.

But under its new timetable, the utility decided to give precedence to a method of pouring water to fill reactor containment vessels to cool pressure vessels as suggested by U.S. nuclear experts.

This water-filling method is able to bring about a cooling effect within a short period, TEPCO official Junichi Matsumoto said, adding that the utility determined that filling containment vessels with water would be "the fastest way to cool fuel rods."

Under the timetable, the water-filling operation for the Nos. 1 and 3 reactors requires three months for completion. As for the No. 2 reactor, TEPCO is aiming to finish related work within six to nine months because it is also necessary to repair the damaged pressure suppression chamber.

Each containment vessel has a water capacity of about 6,000 to 7,400 tons. Experts have pointed out risks such as the vessels breaking down after being loaded with such an enormous amount of water or being unable to withstand a series of aftershocks.

If it takes a long time before the reactors are cooled to a state of cold shutdown, the amount of radiation-generated hydrogen will gradually increase, boosting the possibility of a hydrogen explosion, experts said.

TEPCO Vice President Sakae Muto told a news conference that if the amount of water to be poured into the No. 2 reactor's containment vessel increases, so will the chances of radiation-contaminated water leaking.

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New water treatment facilities

As for the handling of contaminated water, there are plans to establish new water treatment facilities and create new reservoirs, according to TEPCO's timetable.

However, TEPCO has admitted the risk of possible delays in establishing such facilities and that they may not work as planned.

When transferring high-level contaminated water, careful handling is required to prevent the water from leaking from hose joints.

Meanwhile, it is highly likely that contaminated water is leaking from the No. 2 reactor, where a pressure suppression chamber is feared to have been damaged. Radiation levels around the reactor are too high for workers to approach and "seal" the reactor building.

At the No. 4 reactor, it is necessary to reinforce the structure below the temporary storage pool for spent nuclear fuel rods to prevent any possible spillage. However, this task is also expected to be fraught with difficulty.

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A race against time

The Fukushima crisis requires a much longer timeframe compared with previous nuclear power plant accidents to achieve cold shutdown.

In case of the 1979 Three Mile Island nuclear power plant accident in the United States, it took the reactors about a month to reach this state.

In the 1986 Chernobyl accident in the former Soviet Union, a radioactive fire caused by an explosion ended after 10 days. Construction of a concrete-walled "sarcophagus" to enclose the nuclear reactor was carried out over a six-month period.

According to TEPCO's timetable, Step 1 is expected to continue for about three months and radioactive substances will need to be discharged to the atmosphere and sea.

It also will take at least three months for the company to be able to control the leak of radioactive materials during Step 2.

The Cabinet Office's Nuclear Safety Commission has estimated that even in April, up to 1 terabecquerel per hour of radioactive substances are spreading into the air. Even if TEPCO's operations proceed as scheduled, several thousand terabecquerels of radioactive substances will be emitted by the time the situation is brought under control.

It is especially crucial during the first three months to suppress radioactivity by using underwater curtains and giant reactor building covers equipped with special filters. It is also feared that the upcoming typhoon season will impact on plans to enclose the damaged reactor buildings.

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Specialists skeptical

Specialists are skeptical of TEPCO's timetable for bring the reactors at the Fukushima plant to cold shutdown within nine months.

"Cooling the nuclear reactors should be the top priority, but TEPCO's timetable shows they will instead be doing many things at once," said Michio Ishikawa, a top advisor to the Japan Nuclear Technology Institute. "I'm worried that realizing the timetable might be pie in the sky."

Ishikawa emphasized that setting up new heat exchangers to cool the reactors was the most important step. Referring to TEPCO's plan to externally cool the reactors by filling the containment vessels with water, he said, "Cooling the reactors with impounded water is not such an effective strategy."

"Judging from difficulties experienced thus far [in efforts to bring the situation at the plant under control], I doubt that TEPCO can stabilize the reactors within nine months," said Ishikawa. "I think TEPCO also needs to review its organization, for example, by having someone who can exert strong leadership [to spearhead the timetable's implementation]."

Shojiro Matsuura, former chairman of the Cabinet Office's Nuclear Safety Commission, pointed out some difficulties involved in blanketing the reactor buildings with special covers.

"Temperatures and humidity will rise toward summer. It's already difficult to work wearing protective gear and the situation will be even worse in covered buildings," Matsuura said. "TEPCO needs to take measures against possible heat stroke [among workers]."

TEPCO also has said its goal is for evacuees to return home once the situation is stabilized.

However, Atsushi Kasai, former chief researcher at the Japan Atomic Energy Research Institute, expressed concern over soil contaminated with radioactive substances.

"I'm concerned about soil contamination by radioactive cesium--it has a long half-life of about 30 years," Kasai said. "These are highly contaminated areas. Careful consideration must be given as to whether residents be allowed to return home so early."

(Apr. 19, 2011)