Fukushima Daiichi utility TEPCO has begun draining 11,500 tons of low-level radioactivity wastewater into the sea to make space for higher-level wastewater storage, according to Japanese news agency NHK, as republished by the Japan Atomic Industrial Forum.

Reactor-by-reactor, system-by-system summary from JAIF on 5 April

Reactor-by-reactor, system-by-system summary from JAIF on 5 April: yellow indicates abnormal/unstable; red means damaged/nonfunctional/unsafe

According to TEPCO, the level of iodine-131 is 100 times the legal limit, but even if people ate fish and seaweed from the affected region every day for a year, their radiation exposure would be 0.6 mSv, which is still just over half the maximum annual dose (1.0 mSv). The government approved the plan, according to chief cabinet secretary Yukio Edano, who also said that the government instructed the utility to monitor seawater radioactivity.

Most of the water, 10,000 tons, will be drained from the central radioactive waste store. Another 1500 tons comes from the sub-drain pits of unit 5 and 6, from which it is flowing into buildings, TEPCO said in a statement.

Tanks continue to be emptied to make space for radioactive water pooling in the turbine building basements.

In addition to its onshore tanks, TEPCO has approached Shizuoka City about renting an offshore floating platform to store radioactive water, NHK reports. The 136m by 46m barge can store 18,000 tons of water, although TEPCO plans to only use half after it is modified in a Yokohama shipyard. It is currently being used as a sport fishing park.

In other news, efforts to plug a crack in a leaking culvert at unit 2, which contains highly radioactive water, have so far been unsuccessful. However, that failure might not be so significant, since the exact pathway of radiation leaking into the sea remains unclear. On Monday 4 April TEPCO workers injected a dye into water in a tunnel that leads to the culvert, but the dyed water did not flow into the culvert.

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