The stricken Fukushima Daiichi Nuclear Power Plant has probably been leaking contaminated water into the ocean for two years, ever since an earthquake and tsunami caused core meltdowns at three of the plant’s six reactors. However, neither the staff nor the plant’s operator know exactly where the leaks were coming from, or how to stop them.

 

The operator, Tokyo Electric Power, has reported spikes in the amounts of radioactive cesium, tritium and strontium detected in groundwater at the plant, adding urgency to the task of sealing any leaks. Radioactive cesium and strontium, especially, are known to raise risks of cancer in humans.

 

A critical problem has been the groundwater that has been pouring into the basements of the damaged reactor buildings and becoming contaminated. Workers have been pumping the water out to be stored in dozens of tanks at the plant, but have not stopped the inflow.

 

Since the Fukushima Daiichi plant is not watertight, experts have suspicions that the plant might have continued to leak radiation into the ocean long after the huge initial releases seen in the disaster’s early days.

 

Tepco has taken some measures in the hope of keeping contaminated groundwater away from the sea, including fortifying an underwater wall that runs along much of the shoreline at the plant site. Some experts wonder if those measures would be effective.