The k2p blog

It is becoming increasingly clear that the Fukushima nuclear plant successfully withstood quake accelerations which were somewhat higher than had been designed for but the real damage came from the tsunami which overwhelmed the defences of the plant and then knocked out all the emergency generators (13 of them in the basement apparently). That in turn knocked out all cooling pumps and cooling functions and then the die was cast…..

image IAEA - credit Google Earth

From JAIF:

The chief executive of General Electric has stressed that the GE reactors at the Fukushima Daiichi nuclear plant have no structural problems. Jeff Immelt spoke to NHK and other media outlets on Thursday. Some observers say the No. 1 and 2 reactors, the oldest types at the plant, have a flaw in their designs. He said the GE reactor has been in service for more than 40 years and is well tested and well-designed and has been upgraded over time. Immelt said in Washington on Thursday that he was aware of the doubts expressed about nuclear power plants. But  he said it is necessary to diversify energy sources at a time of rising oil prices. In the United States, more than 20 reactors are in use that have similar structure to the Fukushima No. 1 and 2 reactors. Questions were raised about their safety after the Fukushima reactors were damaged last month.

Meanwhile TEPCO released further information about the forces measured during the quake:

TEPCO says 3 of the plant’s 6 reactors were shaken on March 11th by tremors exceeding forces they were designed to withstand. Reactor No.2 suffered the largest horizontal ground acceleration of 550 gals, which is 26 percent stronger than the reactor’s design limit.

(A gal – is named after Galileo Galilei (1564-1642) – and is a unit of acceleration equal to 1 centimetre per second per second – 1 cm /s/s)

TEPCO says the readings were 548 gals at the No.5 reactor, about 21 percent higher than its design limit; and 507 gals at the No.3 reactor, topping the capacity by about 15 percent. The power company says the strength of ground motions were close to or within the design parameters at the remaining 3 reactors, and at all 4 reactors of the nearby Fukushima Daini nuclear plant.
The utility says it had been planning to reinforce the reactors so they could withstand horizontal shaking of 600 gals, after the government reviewed their quake-resistance standards 5 years ago. But the work was not finished.

In the event strengthening the earthquake resistance would not have helped. By all accounts the tsunami wave was more than twice the height of the existing wall defences.

Reactors 3 and 4: image TEPCO

Tags: Fukushima Dai-ichi nuclear plant, GE reactors, The Tokyo Electric Power Company

This entry was posted on April 2, 2011 at 7:39 am and is filed under Japan, Natural Disasters, Nuclear Power. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.