Tokyo Electric Power Company on April 17 issued a plan for cooling down the reactors and reducing radiation leaks within six to nine months at the crippled Fukushima Dai-ichi nuclear power plant on Japan’s Pacific coast. The plan was announced as a pair of remotely controlled robots measured radiation levels inside three of the reactor buildings too high for workers to endure.
On April 18, TEPCO released radiation data and photos taken by the US-made PackBot ground robots. Measurements showed that radiation levels are too high for workers to enter the reactor buildings. This is the first time conditions inside the buildings have been made public since the March 11 earthquake and tsunami caused the loss of cooling functions to the nuclear fuel when offsite power and emergency backup power were lost. Partial meltdowns of the nuclear fuel rods caused hydrogen gas explosions in three of the plant’s six reactors and high radiation levels have kept workers out of the buildings.
Officials announced for the first time April 18 that spent fuel rods in the Unit 2 reactor are damaged. Japan’s Nuclear and Industrial Safety Agency sent a report to the Nuclear Safety Commission, also saying that some fuel pellets and rods in the reactors in Units 1, 2 and 3 had overheated and melted, the first time the agency has given details of damage to the nuclear fuel.
All six reactors are shut down, but temperatures in the nuclear reactor pressure vessels remain above cold shutdown conditions in all units, typically less than 95 degrees Celsius. TEPCO continues to spray cooling water into Units 3 and 4 to cover the nuclear fuel, an operation that has been going on for weeks.
TEPCO said the robots surveyed inside the Unit 3 reactor for two hours and 30 minutes, but TEPCO says the robots had trouble moving around through the debris. The maximum radiation reading obtained was 57 millisieverts per hour. A person remaining in such an environment for five hours would be exposed to 285 millisierverts of radiation—35 millisierverts above the legal limit for nuclear workers in emergency situations.
A robot surveyed Units 1 and 2 for shorter periods and measured slightly lower levels of radiation.
Japan reported to the UN nuclear agency that 28 workers have received high radiation doses as they struggled to stabilize the damaged power plant.
On April 17, the Ministry of Economy, Trade and Industry and TEPCO announced the “Roadmap towards Restoration from the Accident at the Fukushima Daiichi Nuclear Power Station.” The roadmap outlines 63 measures to be taken in two steps over a period of six to nine months. Industry Minister Banri Kaieda called the plan “an important step forward.”
“Taking this opportunity,” Kaieda said, “we would like to move from the ’emergency response phase’ up until now to the ‘planned and stabilizing action phase,’ in which the settlement of the situation will be aimed under the solid roadmap.”
TEPCO declared the company will “make every effort to enable evacuees to return to their homes and for all citizens to be able to secure a sound life” within six to nine months. At a news conference TEPCO chairman Tsunehisa Katsumata explained the company’s plan. He said the company plans to put enormous covers over the reactor buildings to prevent the further release of radioactive substances into the air.
Over the next three months, TEPCO aims to cool the Unit 1 and 3 reactors by continuing to inject water into the containment vessels to cover the fuel rods. The company plans to purify contaminated cooling water, return it to the reactors and set up heat exchangers to remove heat from the reactors. At the Unit 2 reactor, TEPCO says it will contain the radiation leak by patching the damaged section, then take the same measures as at other two reactors. In the second stage, TEPCO plans to lower the temperature of the fuel in the reactors to below 100 degrees Celsius.
Japanese Prime Minister Naoto Kan on Monday said the government is suspending the plans to build new nuclear power plants in view of the ongoing crisis at Fukushima Daiichi. “We will not proceed with the plans that have been put forward until now” before the government completes a full examination of the accident and makes sure that nuclear plants in the country are safe,” Kan told parliament, Kyodo News reported.
Before the crisis, the Japanese government had planned to add at least 13 more nuclear power stations by 2030 in an attempt to limit global warming. Japan now has 54 operating nuclear power plants, with two others under construction.
From Environment News Service, April 18