Evac zone expanded & US ship bringing fresh water for reactor cooling (due to salt buildup)

[kristopher]

Japan expands nuclear plant's evacuation zone
Reporting from Tokyo—
Japan's government Friday urged residents living within 18 miles of the stricken Fukushima nuclear power plant to voluntarily evacuate to avoid further hardship and suggested that officials could order the zone cleared.

Residents living within 12 miles of the plant have been evacuated, yet those living between 12 and 18 miles of the facility have been told it is safe to remain as long as they stay indoors. But two weeks after a massive earthquake and tsunami struck the country and hobbled the plant, causing radiation to leak, the situation has yet to be resolved....

snip

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Japan has been cooling the reactors and spent-fuel pools at the nuclear facility by spraying them with seawater because normal cooling systems were knocked out by the quake and tsunami. But Japan's defense ministry said that American officials had expressed grave concern that the saltwater could cause equipment to seize up and corrode, making resolution of the situation even more difficult.

Japanese officials said the U.S. was dispatching a vessel carrying fresh water from Yokosuka naval base to the Fukushima site.

http://www.latimes.com/news/nationworld/world/la-fgw-japan-nuclear-plant-20110326,0,5763742.story

[jannyk]

1. Watch the actual report on NHKNews

http://www.ustream.tv/channel/nhk-world-tv

[kristopher]

2. Salt buildup - 99,000lb ea in 2&3 / 57,000lb in 1

Nuclear engineers have become increasingly concerned about a separate problem that may be putting pressure on the Japanese technicians to work faster: salt buildup inside the reactors, which could cause them to heat up more and, in the worst case, cause the uranium to melt, releasing a range of radioactive material.

He (GE engineer) estimates that 57,000 pounds of salt have accumulated in Reactor No. 1 and 99,000 pounds apiece in Reactors No. 2 and 3, which are larger.

The big question is how much of that salt is still mixed with water and how much now forms a crust on the uranium fuel rods.

Crusts insulate the rods from the water and allow them to heat up. If the crusts are thick enough, they can block water from circulating between the fuel rods. As the rods heat up, their zirconium cladding can rupture, which releases gaseous radioactive iodine inside and may even cause the uranium to melt and release much more radioactive material.

http://www.nytimes.com/2011/03/24/world/asia/24nuclear.html?_r=1&ref=asia