High Levels of Radioactive Strontium-90 Detected in Fukushima Groundwater [VIDEO]

Groundwater at Japan's beleaguered Fukushima Daiichi nuclear power plant contains high levels of the toxic radioactive isotope strontium-90, officials at the facility said Wednesday.

Tokyo Electric Power Company (Tepco) said tests shows levels of strontium-90 were present at 30 times the legal rate. Tritium, a less-harmful radioactive isotope, has also been detected at elevated levels.

The nuclear power station, which was crippled by a powerful earthquake and tsunami in 2011, has been plagued recently with a string of power failures and leaks.

Toshihiko Fukuda, a Tepco official, reportedly said strontium levels in groundwater around the stricken nuclear reactor had increased 100-fold in the past year.

Strontium-90 is a byproduct of the fission of uranium and plutonium in nuclear reactors and nuclear weapons. The radioactive isotope likely accumulated after water poured over the melted fuel leaked out from a turbine in the building, Fukuda said.

"As it's near where the leak from reactor number two happened, and taking into account the situation at the time, we believe that water left over from that time is the highest possibility," Fukuda said. He said Tepco did not believe any of the strontium-90 has leaked into the ocean, according to a Reuters report.

The admission of radioactive strontium and tritium in the groundwater is a further revision of Tepco's earlier claims that groundwater at the facility was not radioactive. Earlier this month the utility reversed a prior claim and reported trace amounts of cesium in the groundwater.

The levels of cesium found in the groundwater, were low, reported at 0.39 becquerels of radioactive cesium-137 per liter of water. Japan's safety level for cesium in drinking water is 10 becquerels per liter. A becquerel is a measure of radioactive decay.

Between December 8, 2012 and May 24 groundwater tests showed that strontium-90 increased from 8.6 becquerels to 1,000 becquerels per liter. The legal limit for strontium is 30 becquerels per liter, about 30 times the legal limit. Tritium levels were also higher across the same time span, testing at eight times the allowable levels.

Dealing with contaminated water has proven to be one of the greatest challenges for Tepco. The presence of radioactive material in the water has caused public resistance to Tepco's plan to pump the groundwater into the sea, which will likely be further compounded by the latest news.

"This contaminated water should not be released to the ocean," Michiaki Furukawa, a nuclear chemist and professor emeritus at Nagoya University, told Reuters. "They have to keep it somewhere so that it can't escape outside the plant."