As Japan resumed generating nuclear power Tuesday, restarting 1 reactor in the south, the destroyed Fukushima Dai-ichi plant in the northeast remains a highly radioactive site, more than four years after an earthquake and tsunami triggered meltdowns in three of its six reactors.

A look at the status of the plant:

RADIATION LEAKS

Water is still being pumped into the reactors to prevent further meltdowns, and huge amounts of it, now radioactive, have leaked out of the damaged containment chambers and into other parts of the buildings. Some has leaked outside, so a sea wall and an underground barrier have been built to try to block the contaminated water from reaching the sea. Any leakage now appears to be minimal, but the immediate coastal waters are largely closed to commercial fishing.

EVACUATIONS

Radioactive material spewed out by the initial explosions and meltdowns contaminated nearby towns and farms and driven more than 100,000 people to leave their homes. Some areas have been cleaned up, but decontamination work often needs to be repeated, and some remain off-limits. Some people have returned to areas deemed safe, many of them senior citizens, while families with children have tended to stay away. The government plans to send evacuees back to all but the most uninhabitable areas by March 2017, and to cut financial support for those who won't return.

DECOMMISSIONING

Removal of melted fuel from the three reactors — the most challenging part of the 30- to 40-year cleanup — will not begin until 2022. Experts have yet to pinpoint the exact location of the melted fuel and study it, and need to develop robots capable of working safely under extremely radioactive conditions.

IMPLICATIONS FOR JAPAN'S NUCLEAR INDUSTRY

The government has set a goal to have nuclear power share more than 20 percent of resource-poor Japan's power generation by 2030. However, additional costs to retrofit and modernize plants to meet post-Fukushima safety requirements, as well as huge decommissioning costs, could make nuclear power less appealing to utility companies. Most experts doubt Japan will build any new nuclear plants, and as aging reactors are taken offline, the industry may be phased out.