Radioactive leak plugged, officials now eye hydrogen buildup: Japan nuclear timeline

Officials say workers have stopped highly radioactive water from leaking into the ocean from the stricken Fukushima Daiichi nuclear plant's No. 2 reactor. Concerns now center on a buildup of hydrogen inside reactor No. 1.

Japan Maritime Self-Defence Force/Reuters
A US military barge carrying pure water (bottom) leaves the quay near Tokyo Electric Power Co.'s Fukushima Daiichi Nuclear Power Plant to refill with pure water in Fukushima Prefecture, April 4. Japan officials say workers have stopped highly radioactive water leaking into the sea on Wednesday from the crippled nuclear plant and said it could have given more information to neighboring countries about contamination in the ocean. Nuclear experts are now concerned about possible damage to the core of reactor No.1.

This timeline will be updated with the latest nuclear developments in Japan.

Week 4, April 4 - April 8

April 6: Emergency workers have managed to stop the radioactive water, measured at 7.5 million times the legal limit, from leaking out of the Fukushima Daiichi nuclear plant's reactor No. 2 and into the ocean, say officials. Plant operator Tepco is now concerned about a build-up of hydrogen inside reactor No. 1, which may mean the reactor's core is damaged. As a precautionary measure, officials say workers are preparing to inject nitrogen into the containment vessel to try to bring the reactor under control. Meanwhile, Japan's official spokesperson, Yukio Edano apologized to neighboring countries for not notifying them before they started pumping low-level radioactive water into the ocean this past weekend.

April 5: Tepco says it is continuing to pump millions of gallons of contaminated water, overflow from efforts to cool the Fukushima Daiichi nuclear power plant, into the sea. The move is to help cooling efforts as workers attempt to slow a major leak of highly radioactive water from the plant. Tepco says it has succeeded in slowing leaking water from the No. 2 reactor. However, the levels of radioactive contamination of caesium in fish are now exceeding health guidelines, increasing environmental and food safety concerns. Meanwhile, Japanese police have charged two people with selling a fake radiation protectant drug, according to investigators.

April 4: Tepco said some 11,500 tons of contaminated water would be released today in order to make room for more radioactive water storage. Authorities say they have still not found the source of a leak they believe is responsible for highly contaminated water levels near Fukushima.

Some key Facts as of Friday, April 1:

  • Death toll: 11,600
  • Unaccounted for: at least 16,450
  • Displaced: about 500,000
  • Buildings damaged or destroyed: more than 155,000
  • International Search and Rescue specialists on the ground according to OCHA: 543 (14 teams) from 12 countries.
  • Countries that have pledged assistance to Japan: more than 120
  • Estimated damage cost: $309 billion

Find the full Japan nuclear timeline here

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