OLKILUOTO, Finland  As the Obama administration tries to steer America toward cleaner sources of energy, it would do well to consider the cautionary tale of this new-generation nuclear reactor site.

The massive power plant under construction on muddy terrain on this Finnish island was supposed to be the showpiece of a nuclear renaissance. The most powerful reactor ever built, its modular design was supposed to make it faster and cheaper to build. And it was supposed to be safer, too.

But things have not gone as planned.

After four years of construction and thousands of defects and deficiencies, the reactor’s 3 billion euro price tag, about $4.2 billion, has climbed at least 50 percent. And while the reactor was originally meant to be completed this summer, Areva, the French company building it, and the utility that ordered it, are no longer willing to make certain predictions on when it will go online.

While the American nuclear industry has predicted clear sailing after its first plants are built, the problems in Europe suggest these obstacles may be hard to avoid.