TEPCO starts dumping radioactive water into ocean

2011/04/06

The Fukushima No. 1 nuclear power plant (Provided by Air Photo Service)

Editor's note: We will update our earthquake news as frequently as possible on AJW's Facebook page: http://www.facebook.com/AJW.Asahi. Please check the latest developments in this disaster. From Toshio Jo, managing editor, International Division, The Asahi Shimbun.

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With an apology to the public, Tokyo Electric Power Co. on Monday night began discharging water with low levels of radiation into the ocean from the crippled Fukushima No. 1 nuclear power plant.

"Because the volume of contaminated water is huge and due to time constraints, we chose the option of discharging the water," a TEPCO official told a news conference.

TEPCO officials explained the decision was made to free up storage space within the plant grounds for water contaminated with much higher levels of radiation.

This is the first time TEPCO has knowingly discharged contaminated water into the ocean.

A total of 11,500 tons of contaminated water will be dumped into the ocean over the next few days.

Under the reactor regulation law, contaminated water can be discharged as an "emergency measure." TEPCO officials submitted the water discharge plan to the Nuclear and Industrial Safety Agency and received its approval.

An NISA official said the TEPCO decision was "unavoidable."

According to TEPCO officials who calculated the effects from the water discharged, even if an individual ate fish and seaweed taken at least 1 kilometer from the Fukushima plant on a daily basis for a year, the amount of radiation ingested would only be one-fourth of the natural radiation exposure over the course of a year of 2.4 millisieverts.

TEPCO officials said 10,000 tons of water would be discharged from the central waste processing facility.

Once the water has been discharged, highly contaminated water at the basement of the turbine building for the No. 2 reactor would be moved to the waste processing facility.

In addition, 1,500 tons of groundwater stored around the No. 5 and No. 6 reactors will also be released into the ocean to prevent the water seeping from the ground from flooding important equipment in those reactors, such as emergency generators.

The contaminated water at the No. 2 reactor turbine building contains radioactive iodine at levels of several million becquerels per cubic centimeter.

In contrast, the water in the central waste processing facility has a radioactivity level of 6.3 becquerels while the water from the No. 5 reactor has a radioactivity level of 1.6 becquerels and the water from the No. 6 reactor 20 becquerels.

While the radiation levels of the water to be discharged into the ocean are similar to contaminated rainfall around the Fukushima plant, they are still 100 times the standard for radiation levels in seawater as defined by the reactor regulation law.

The total amount of radioactivity that will be discharged into the ocean will be 170 billion becquerels.

While that may seem like a lot, the radioactivity level in 10,000 tons of the discharged water is equivalent to about 10 liters of contaminated water accumulated at the basement of the No. 2 reactor.

The highly contaminated water in the No. 2 reactor turbine building is slowing work to restore a cooling mechanism that would be necessary to eventually achieve a cold shutdown of the reactor core.

One idea initially considered was moving the contaminated water into the central waste processing facility, but the facility was flooded by the tsunami following the March 11 Great East Japan Earthquake.

An attempt to move the water in the waste processing facility to another location failed.

The water is believed to have been contaminated from radioactive materials that spread from the Fukushima plant.

The reactor buildings and turbine buildings were also flooded by the tsunami because the buildings were located near the coastline.

Although the contamination levels of the water to be discharged are low, there will inevitably be effects on the environment.

The Hirakata fishing cooperative in Kita-Ibaraki announced Monday that Japanese sand lance caught off the coast contained radioactive iodine at levels of 4,080 becquerels per kilogram.

Because the Food Sanitation Law does not currently contain standards for radioactive iodine in fish and meat, health ministry officials are considering establishing such standards.

Cesium at radioactivity levels of 447 becquerels was also found in the sand lance. The legal standard for cesium is 500 becquerels.

The fishing cooperative caught five types of fish as an experiment before the resumption of fishing.

Health ministry officials advised against eating the sand lance because the radioactive levels were double the standards set for some vegetables.

Ibaraki prefectural government officials said the sand lance would not be available on the market because there was no fishing of it off the coast of Ibaraki.

Masashi Kusakabe of the Marine Ecology Research Institute said: "Although the half-life of iodine is short at eight days, fish that swim in waters that are constantly contaminated with radiation will accumulate a certain level of radiation. A thorough check of the fish is necessary because fish tend to be eaten while fresh."

TEPCO workers are still a long way from stable cooling of three reactors. And water contaminated by high levels of radiation continues to leak from the No. 2 reactor, where its containment vessel is believed to have been damaged.

The No. 1 reactor still requires careful calibration of the water pumped into the core because the relative airtightness of the core has led to fluctuations in core pressure.

The temperature in the No. 1 reactor core reached about 400 degrees on March 23. While the temperature has since fallen, it was still 234 degrees as of 6 a.m. Tuesday.

Pipes to the pressure container of the No. 2 reactor have been damaged, so there is the possibility that core pressure is dropping as a result. That has, in turn, made it easier for water to be pumped in, which likely led to a decrease in the temperature, some experts said.

However, the water that overflows from the reactor is believed to have leaked onto the plant grounds.