The Yomiuri Shimbun
The government said it plans to soon begin using freshwater instead of seawater to cool reactors Nos. 1 to 4 at the Fukushima No. 1 nuclear power plant to prevent salt from eroding water pipes, after high levels of radioactive substances were found in the sea near the facility's south drain outlet.
Hidehiko Nishiyama, a senior official of the Economy, Trade and Industry Ministry, said Saturday morning that pressure inside the No. 1 reactor core had been stabilized thanks to freshwater injected into the reactor Friday.
After injecting freshwater into the No. 2 reactor's core Saturday morning, Nishiyama revealed a plan to also inject freshwater into the four reactors' temporary storage pools for spent nuclear fuel rods as early as Sunday.
Experts said the high level of radioactive substances found in the sea was probably from water-distribution pipes that are part of the reactors' cooling system. Those pipes are believed to have been damaged both by the March 11 earthquake and erosion from seawater used since the disaster, raising fear that further radiation leaks could occur.
Keiji Miyazaki, professor emeritus of Osaka University, said, "Crystallized salt left after seawater evaporates could clog the pipes and prevent water from flowing since seawater is about 3.5 percent salt."
"I don't know yet where [the radioactive substances] leaked from, but freshwater should be used to lessen damage to the pipes as soon as the reactors' freshwater pumps are repaired," Miyazaki said.
The Fukushima No. 1 plant's reactor cooling system normally uses freshwater from a nearby dam, removes any impurities, and saves it in a tank for emergencies. The March 11 earthquake and tsunami, however, destroyed the water-pumping equipment.
Tokyo Electric Power Co. decided to inject seawater after freshwater stored for firefighting purposes in the tank had run out. But injecting seawater with its many impurities could clog the pipes, erode cables, and damage storage pools and other equipment.
Work to enable a switch from seawater to freshwater has been in full swing after the motor for the freshwater pump was repaired Friday. Experts said it would be extremely difficult to determine how much damage seawater has caused to water pipes in the cooling system.
Meanwhile, working conditions near the reactors and turbine buildings continued to be dangerous after three workers were exposed to water with high levels of radioactive materials in the basement of the turbine building of the No. 3 reactor on Thursday. The focus is now on whether the use of freshwater can occur as scheduled.
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Experts blame management
Meanwhile, experts said TEPCO should ensure that workers are well-informed about how to protect themselves from contamination, as pools of water containing high levels of radioactive substances have been found inside buildings related to the facilities for reactors Nos. 1 to 4, and in the rubble surrounding those buildings.
Two of the three workers were wearing shoes when they stepped into a pool of contaminated water in the turbine building. The water eventually came into contact with their skin.
"The workers could have prevented themselves from being exposed to radiation just by wearing long boots," Kyoto University Prof. Masami Watanabe said. "Management should be blamed for the accident because it failed to keep workers well-informed."
The depth of the pool of water in the turbine building varied from about 20 centimeters to 150 centimeters. TEPCO said it told the subcontracted workers they should stop their work and evacuate.
Nagasaki University Prof. Shunichi Yamashita, an expert on the environmental risks of radiation, said workers at the nuclear plant have been under great stress.
"Workers' tension levels must be peaking, as they are doing vital work that involves great risk. In this situation, they are likely to make mistakes," Yamashita said. "Management must make every effort to prevent workers from using their own judgment in these operations."
(Mar. 27, 2011)
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