Some five tons of seawater is estimated to have entered a reactor core at the Hamaoka nuclear power station in central Japan, the operator said Thursday, according to dpa. That followed the discovery of an estimated 400 tons of seawater that has inundated the main steam condenser at reactor 5 of the Hamaoka nuclear plant in Shizuoka prefecture, south-west of Tokyo. Chubu Electric Power Co, which runs the plant, found the 400 tons of seawater while shutting down the reactor as requested by the government. Chubu Electric officials said their assessment of the purity of water inside the pressure vessel showed some 5 tons of seawater came from the condenser, Jiji Press reported. The utility will not decommission the reactor. Instead, it will dilute and desalinate the seawater to prevent any corrosion inside the reactor as salt causes corrosion. The steam condenser, designed to convert waste steam from a power-generation turbine into water, has some 64,000 tubes, each 3 centimetres in diameter, where seawater is injected to cool the steam, Jiji reported. The operator is now pumping fresh water into the pressure vessel to reduce the concentration of salt in the water to avoid corrosion of the vessel, company officials were quoted as saying by Jiji. On May 9, Chubu Electric decided to suspend the operation of the plant located near a geological fault line after Japanese Prime Minister Naoto Kan called for the shutdown over growing public concern about another possible nuclear accident after the nuclear emergency triggered by the March 11 earthquake and tsunami. Since the Fukushima Daiichi nuclear plant was crippled by the disaster, it has leaked radioactive substances into the environment. The plant is run by Tokyo Electric Power Co (TEPCO). On Saturday, after Chubu Electric started to put the Hamaoka plant in a stable state known as cold shutdown, it discovered seawater in the reactor core, Jiji said. Meanwhile, local officials in the prefecture of Miyagi said Thursday they had found high levels of radioactive substances in a sample of pasture grass. Local government officials detected 1,530 becquerels of radioactive caesium per kilogram in a sample collected a week ago from a farm run by the town of Marumori, some 60 kilometres north of the Fukushima plant. The figure was more than five times the legal limit of 300 becquerels. Local officials said they also found 350 becquerels of caesium in a sample from a farm in Osaki city. The Miyagi prefectural government has told some 6,000 livestock farmers across the prefecture to refrain from feeding grass to livestock and putting cattle out on grazing land. But the move will mainly affect dairy farmers as the legal limit of grass for breeding and commercial cattle is much higher - 5,000 becquerels, said Inao Yamada, a prefectural official. This is the first time radioactivity exceeding the legal limit has been found in grass or vegetables in the prefecture, Yamada said. Meanwhile, the operator said the total amount of radioactive water at the plant is estimated to top 100,000 tons, which includes some 7,500 tons of water that have already been removed from the buildings of reactors number 2 and 3, Jiji said citing TEPCO. The facilities of reactor number 2 are considered to have the largest amount of contaminated water totaling 25,000 tons - 6,500 tons in the basement of the reactor building, 13,000 tons in the turbine building basement and 5,500 tons in an underground tunnel that stretches toward the ocean, Jiji said. On Wednesday, TEPCO workers entered the building of reactor 2 for the first time since a blast at the containment vessel on March 15 to survey conditions ahead of planned repair work on the key cooling functions. In its revised plan announced Tuesday, TEPCO said it would aim to create a water circulation system in which it would remove radioactive substances from water inundating the facilities of reactors 1 to 4 and use the water to cool reactors. Some 13,800 tons of water at reactors 5 and 6 will be moved to temporary tanks and the operator will use zeolite to absorb radioactive substances in the water, Jiji said.
