Another leak at Fukushima

Another radioactive leak found at Japan's Fukushima nuclear plant

A discharge of contaminated water has been discovered at the disabled Fukushima Daiichi nuclear plant. It is the latest in a string of incident hindering the clean up of the worst nuclear disaster since Chernobyl in 1986.

RT,

5 June, 2013

Tokyo Electric Power Co (Tepco), the owner of the wrecked plant, said it discovered the leak on Wednesday, fueling yet more criticism of the company as it seeks permission to release water into the sea, Reuters reported.

Shunichi Tanaka, the head of Japan's new nuclear regulator, created after its predecessor was discredited in the 2011 accident, told a news conference that Tepco should deal with the situation “without delay.”

Japan’s regulator, however, did not regard the matter as serious, he added.

The Fukushima Daiichi Nuclear Power plant suffered a reactor meltdown and the release of radiation following the 9.0 magnitude Tokohu earthquake - the most powerful earthquake ever to hit Japan - that struck off the coast of Japan on March 11, 2011.

The earthquake unleashed a tsunami with waves of up to 14 meters high (Fukushima was designed to handle up to 5.7-meter waves) that knocked out emergency generators required to cool the reactors.

Wednesday’s setback comes after Tepco revealed this week it had detected radioactive caesium in groundwater flowing into the plant, contradicting an early finding that contamination levels around the facility were negligible.

About 400 tons of groundwater flows daily into the reactor buildings, where it is mixed with highly contaminated water used as coolant for the melted fuel. The realization that groundwater is being contaminated before it enters the damaged reactor units complicates Tepco’s efforts to convince local authorities that the groundwater is safe enough to be dumped into the ocean.

The news also comes as a major political challenge to Prime Minister Shinzo Abe, whose government is set on plans to export Japan's nuclear technology.

The government ordered Tepco last week to increase storage capacity of water tanks and build earthworks around the four reactor buildings to control the flow of groundwater seeping into the facility.

Leaks were discovered in underground storage tanks in April, prompting Tepco to speed up the construction of stronger above-ground containers. The leak discovered on Wednesday was from one of the sturdier tanks, Reuters reported.

The power company is also seeking approval to dump 100 tons of groundwater a day from the plant into the sea, a plan that requires the consent of fishermen who are strongly against the idea.

On May 30, Tepco told fishermen that radioactive caesium in the groundwater was at a level that could not be detected.

But the results were inaccurate as they were skewed by using procedures that failed to take into account the background radiation at the damaged plant, Tepco told Reuters on Tuesday.

"We'll have to correct the way we analyse sample data," said Mayumi Yoshida, a Tepco spokeswoman.

The revised results continue to show radiation levels below what Tepco views as the upper threshold for releasing groundwater - one Becquerel of caesium per 137 per liter. A Becquerel is a measure of radioactivity.

On December 21, 2011, the Japanese government released a comprehensive program for the clean up efforts, which predicted that the full clean up will take 40 years.

TEPCO's failure at math may have increased radiation release at Fukushima plant

Workers miscalculated pressure levels inside a reactor during the early stages of the Fukushima nuclear crisis, leading to a reduction in cooling water and a possible increase in the volume of radioactive materials released.

Asahi Shumbun,

June 05, 2013

By TOSHIHIRO OKUYAMA/ Senior Staff Writer

Tokyo Electric Power Co. estimated the pressure inside the No. 2 reactor containment vessel at 400 kilopascals on March 16, 2011, five days after the Fukushima No. 1 nuclear plant was crippled by the Great East Japan Earthquake and tsunami.

The actual pressure was 40 kilopascals, far below the 101 kilopascals of the surrounding atmosphere, suggesting that a large amount of radioactive materials escaped from the reactor.

TEPCO later discovered the mistake but did not announce it. Instead, the correct pressure figures were included in a deluge of information released by the utility.

TEPCO concluded that pressure was rising on the afternoon of March 16 and halved the amount of water being injected into the No. 2 reactor on the morning of March 17.

Tadayuki Yokomura, chief of the company’s Kashiwazaki-Kariwa nuclear plant in Niigata Prefecture, warned TEPCO officials against lowering the water level later that morning.

“I think the airtightness (of the containment vessel) has not been maintained,” Yokomura said, according to a video footage of a TEPCO teleconference.

However, TEPCO further reduced the amount of water by midday, apparently fearing that flooding the reactor could lead to a rise in pressure that might cause an explosion.

TEPCO increased the amount of water in the late afternoon of March 17 because some officials suspected that much of the injected water was leaking out.

TEPCO noticed the mistake in the pressure level when it reconfirmed data more than a month later. The company said it cannot say whether the mistake affected the situation.

“Radiation levels were unchanged before and after the amount of water injected was changed,” an official said.

The No. 2 reactor was considered the most dangerous at the Fukushima No. 1 nuclear plant early in the crisis. Cooling functions were lost on March 14, and the reactor melted down following the No. 1 and No. 3 reactors.

The difficulty in venting fueled concerns that mounting pressure could rupture the containment vessel and release lethal levels of radioactive materials.

Early on March 15, TEPCO temporarily evacuated all but the minimum required 70 or so workers from the plant compound.

Officials were closely monitoring pressure levels inside the containment vessel as an indicator of whether radioactive materials were contained within the reactor.

At TEPCO’s news conference on the afternoon of March 16, reporters asked about the possibility that the containment vessel had already lost airtightness due to structural damage, and that the pressure inside had fallen to the level of the atmosphere.

Late on the night of March 16, a TEPCO official told reporters that the pressure was rising.

The company presented data that showed the pressure had increased from 220-240 kilopascals earlier in the day to 400 kilopascals or more between 7 a.m. and 2 p.m.

However, the actual figure was 40 kilopascals from early morning through noon.

According to TEPCO, workers thought the reading of a pressure gauge at the central control room was either 40 or 400 kilopascals past noon. However, they were unable to reconfirm the reading for fear of being exposed to high radiation levels.

Instead, workers calculated the pressure based on data from a system that suspends reactor operations if it detects an abnormal pressure rise. But they used a wrong conversion formula and erroneously concluded that it was 400 kilopascals.

TEPCO noticed the mistake in late April at the earliest. The company included corrected pressure figures when it distributed a large volume of electronic data--including figures for other reactors--at a news conference on May 16, 2011.

TEPCO officials did not clearly explain that the March 16 pressure data for the No. 2 reactor had been corrected.

The corrections went largely unnoticed. And the panels set up by the government, the Diet and TEPCO to investigate the nuclear accident failed to address the issue.

The Asahi Shimbun independently analyzed the data for the No. 2 reactor and has asked TEPCO to provide an explanation since April 2012.

“Workers applied a wrong conversion formula while they were preoccupied with dealing with the accident,” a TEPCO public relations official said.

The official also indicated that there was no problem with the way the corrected figures were disclosed.

“We compiled and provided as much information as possible while giving priority to recovery operations at the plant,” the official said.