If there is one word to describe events at the Fukushima No. 1 Nuclear Power Plant in the immediate aftermath of the March 11 quake and tsunami — with cooling systems failing and the worst nuclear disaster since Chernobyl brewing in its reactors — it would be “chaos.”

That is the picture painted by documents released by Tokyo Electric Power Co. (TEPCO) on May 16 describing the situation at the plant in the hours after tsunami slammed into the coastal facility. Coming more than two months after the disaster, the TEPCO data will soon be dissected by a government committee set up to analyze the causes of the nuclear crisis and the actions taken by both the government and TEPCO to contain it.

“The power-source trucks (to supply the reactors with outside power) are stuck in traffic!”

“We’ve given up on venting operations (to lower reactor vessel pressure). The radiation is just too high.”

These are just two of the TEPCO employee reports included in the documents, which also lay out the exact chronology of events at the plant as the disaster unfolded.

At exactly 46 minutes and 46 seconds past 2 p.m. on March 11 — just after the magnitude 9.0 earthquake had struck off the northeast coast of Japan — reactors No. 1-3 began emergency shut-down procedures (reactors No. 4-6 were not operating). However, as the reactors were shutting down, the plant log reveals workers were being bombarded with alarms for control rod insertions in each reactor, water level fluctuations, and other details of a nuclear plant swinging into crisis-response mode.

According to the TEPCO documents, the tsunami hit at about 3:30 p.m., cutting all power at the plant. In response, at about 5 p.m. TEPCO ordered power-source trucks to head to the plant from its branches nearby. However, “the trucks were unable to make progress due to road damage and traffic jams,” a report included in the documents states. Unable to get the trucks to the Fukushima plant, at 6:20 p.m., TEPCO requested neighboring Tohoku Electric Power Co. to send some in their stead.

The Tohoku Electric trucks did not arrive at the plant until about 11 p.m., but faced with “the dark, pools of tsunami water, missing manhole covers on the road, and debris everywhere hindering progress,” workers found hooking up the necessary power cables extremely difficult, according to a report from around dawn on March 12. Power was finally restored to the plant at about 3 p.m., but at 3:36 p.m. a massive hydrogen explosion in the No.1 reactor building destroyed the newly laid cables, cutting power once more.

Meanwhile, workers inside the plant were trying to vent the No. 1 reactor to relieve pressure building in the reactor vessel. Reports made as the crisis went on show workers tried to vent the reactor manually at about 9:15 p.m. on March 11 but soon had to stop, with an entry at about 9:30 p.m. stating, “We tried the operation onsite, but the radiation dose was so high we gave up.” The venting operation was eventually completed, but not until 10:17 p.m.

What the workers were doing between 9:30 p.m. and 10:17 p.m., however, is not revealed in the TEPCO documents, and a TEPCO representative told reporters, “We don’t know what kind of risk assessment led the workers to try again.”

However, an entry for 9:51 p.m. in the plant duty log also released by TEPCO states: “No entry permitted” to the No. 1 reactor building due to high radiation — an order that photos of memos on the plant’s central control room whiteboard show came directly from TEPCO President Masataka Shimizu. The high radiation that led to the no-entry order furthermore lends support to the theory that a core meltdown began soon after the tsunami struck.

While much of the detail surrounding TEPCO’s immediate response to the disaster is included in the documents, there is no record of the utility’s communications with the Prime Minister’s Office, leaving government-TEPCO interactions over critical decisions such as the venting operation and the use of sea water for cooling a mystery.

Mainichi , May 17, 2011
http://mdn.mainichi.jp/mdnnews/news/20110517p2a00m0na010000c.html

Reactor worker error comes to light

Shutting down cooling system before tsunami may have caused meltdown

The emergency cooling system for reactor 1 at the Fukushima No. 1
nuclear plant may have been shut down manually before the tsunami hit
March 11, according to a Tokyo Electric Power Co. spokesman and
documents released by the utility.

A part of the cooling system known as the isolation condenser was down
for about three hours, which could have contributed to the reactor
core’s meltdown.

The finding upends the government’s previous conclusion that the
condenser was functioning normally on March 11.

“I learned (of the shutdown) through media reports today,” Chief Cabinet
Secretary Yukio Edano told a news conference Tuesday. "We have asked the
Nuclear and Industry Safety Agency and other bodies to give detailed
analyses and reports (on that matter)."

NISA, the government agency that oversees nuclear plant operators, urged
Tepco on Tuesday to provide a detailed explanation by May 23.

Tepco, Japan’s largest electricity supplier, disclosed internal
documents and data Monday indicating the isolation condenser may have
been manually shut down around 3 p.m. March 11 shortly after kicking in
following the massive quake at 2:46 p.m. The plant was hit by tsunami
around 3:30 p.m.

The release of key data following the March 11 disaster was delayed
because most of it was kept in computers and documents in the plant’s
central control room, where high levels of radiation prevented workers
from entering, Tepco said.

The isolation condenser is designed to inject water into the reactor for
at least eight hours after the main coolant system loses power, as
happened March 11.

"It is possible that a worker may have manually closed the valve (of the
isolation condenser) to prevent a rapid decrease in temperature, as is
stipulated by a reactor operating guideline," Tepco spokesman Hajime
Motojuku told The Japan Times.

A worker may have stopped the condenser to keep cold water from coming
into contact with the hot steel of the reactor to prevent it from being
damaged.

By MINORU MATSUTANI and MASAMI ITO, Japan Times Staff writers, May 18, 2011
http://search.japantimes.co.jp/cgi-bin/nn20110518a2.html