After the worst nuclear accident in Japan's history, workers at the Fukushima Daiichi nuclear power plant are still battling radiation and contaminated water in the decommissioning process. They've made progress, but there is still a long way to go.
The plant's 3 reactors suffered meltdowns following the earthquake and tsunami. It's believed nuclear fuel rods melted and fell to the bottom of containment vessels. Removing that fuel debris remains the most difficult part of decommissioning.
Engineers have found what appears to be fuel debris in 2 of the reactors using robots and cameras. But figuring out how much there is and how to remove it remain big questions. Still, Japan's government and the operator Tokyo Electric Power Company say they want to begin removing the debris from one of the reactors in about 3 years.
Radiation levels are so high near the reactors that workers can't spend much time there. But outside the buildings, levels have gone down through decontamination measures.
Another big problem is contaminated water. Groundwater continues to seep into the reactor buildings, getting contaminated. Although it is processed and stored, there's still no decision on what to do with more than 800 tanks.
The operator has built an underground wall of frozen soil to prevent some groundwater from getting in the buildings. TEPCO says it is not the only answer and is also trying other methods. The decommissioning process is expected to take decades, with the government estimating it will cost more than US$70 billion. Adding in costs for the broader decontamination of surrounding areas and compensation for affected residents, the bill could reach about US$200 billion.