Highly toxic plutonium has been found in soil in five separate locations at the crippled Fukushima Nuclear Power Plant in northeast Japan, the facility's operator said Tuesday, which has caused global concern about the growing severity of the crisis at the leaking plant.
Owner and operator of the stricken six-reactor plant, Tokyo Electric Power Co. (TEPCO), said that the plutonium may well have been discharged from nuclear fuel at the plant following the facility being damaged by the massive March 11 earthquake and ensuing tsunami.
The utility firm also said the levels of plutonium found were small, although a spokesperson for TEPCO said at a press conference that it was "deplorable" that plutonium had escaped, despite the plant's containment measures.
"I apologize for making people worried," said Sakae Muto, vice president of TEPCO, announcing the latest piece of bad news from Fukushima at a briefing in Tokyo.
Muto said the levels of radiation found in traces of plutonium-238, 239 and 240 were in keeping with levels found in Japan in the past due to particles in the atmosphere from nuclear testing in the U.S. and Russia.
"It's not at the level that's harmful to human health," Muto said.
Nuclear experts said that it was likely that some, if not all of the leaking plutonium probably came from spent nuclear fuel rods at the plant or caused by damage to the facility's troubled No. 3 reactor.
The No. 3 reactor is the only one at the six-reactor facility to use plutonium in its fuel mix, TEPCO said.
The United Nations' International Atomic Energy Agency said the find was expected due to known fuel degradation, however Japan's Nuclear and Industrial Safety Agency is highly worried about the radioactivity of the plutonium samples detected.
The levels of radioactive decay ranged from 0.18 to 0.54 becquerels per kg, the agency said.
"While it's not the level harmful to human health, I am not optimistic. This means the containment mechanism is being breached so I think the situation is worrisome," agency official Hidehiko Nishiyama said.
Plutonium is more toxic than other radioactive substances such as iodine and cesium and plutonium emits alpha radiation and low-energy x-rays which are easily absorbed by human tissue.
Human exposure occurs mainly by breathing contaminated air or ingesting contaminated food or water. Breathing is generally the route of most concern, experts said.
When plutonium particles are inhaled and lodge in lung tissue they continue to give off radiation internally and can remain in the lungs or enter the gastrointestinal tract and the bloodstream.
Roughly 80 percent of the plutonium that enters the bloodstream goes either to the liver, bone or bone marrow, where it is retained for years, damaging tissue nearby, that may result in cancer, said the experts.
Due to the escalating crisis at the power plant located 240 kilometers northeast of Tokyo, Japan's Chief Cabinet Secretary Yukio Edano said Monday that residents living within the 20-kilometer evacuation zone around the stricken facility should not return home for the time being.
"It is very likely that the area within 20 km from the plant is contaminated and there is a big risk to human health at the moment, " Edano said, adding that residents should remain outside the evacuation zone until told otherwise by the government.
TEPCO on Monday continued with work to remove contaminated water from four of the plant's reactors by pumping the water from the basements into the reactors' turbine condensers for storage.
The plant's operator said the concentration of radioactive substances detected in the pool at the No. 2 reactor was 100,000 times higher than usual, reading more than 1,000 millisieverts per hour at the surface of the flooded No. 2 reactor's turbine building.
The government's nuclear safety agency also said Monday that radioactive iodine-131 more than 1,000 times above the maximum level was detected Sunday in a seawater sample taken around 1.5 kilometers north of the drainage outlets of the plant's four most troubled reactors, suggesting the crisis is still far from over and radiation fears are mounting by the hour.
Three workers have been hospitalized following exposure to radiation at the faltering plant since work began to restore cooling systems following the March 11 earthquake and tsunami that devastated the region and damaged the plant.
A total of 19 workers have been exposed to radiation exceeding 100 millisieverts at the plant -- the previous legal limit before the government raised it to 250 millisieverts -- to allow for more workers to work in rotating shifts to deal with the world's worst nuclear crisis since the 1986 Chernobyl disaster in the Ukraine.
(Xinhua News Agency March 29, 2011)