The Japanese school summer holidays have begun and on Kariwa’s vast beach two small boys are building sandcastles in the sun as their father inflates a rubber dinghy. They are quite alone on a strip of golden sand that normally draws thousands.

A hundred yards behind them, a street lies in ruins: about a quarter of the homes have been reduced to heaps of rubble. Pasted on the doors of the others are the dreaded red-and-yellow posters that mark them, perhaps forever, as uninhabitable.

And less than half a mile along the beach from where the boys are playing rise the ominously quiet exhaust chimneys of the world’s biggest nuclear power plant — its seven reactors silenced since the ground beneath was wrenched apart by the massive earthquake last month.

The awesome damage inflicted in just a few moments of extreme seismic violence has put Kashiwazaki at the centre of a painful debate — both for villagers here and Japan’s policy makers forced to confront the country’s so-called nuclear taboo.

The question is whether the badly damaged but economically vital plant should ever be allowed to switch its reactors back on.

The Times, armed with a small gamma-radiation detector, was allowed a rare tour of the reactor buildings yesterday — and the picture was grim. Inspectors from the International Atomic Energy Agency, who were also touring the reactors, were confronted by a dot-matrix screen at the site entrance that reads: “Consecutive days since last disaster — 4.”

The roads within the plant are puckered and twisted like rumpled carpets – many were patched-up hastily to allow heavy industrial vehicles to reach the worst-affected parts of the plant. Flights of stairs no longer meet their intended floors at either end, and steel lamp-posts lie strewn on the ground.

Some corridors within the reactor buildings themselves, are split by 12-inch cracks along the floor. Near one of the reactors the surrounding area has subsided by more than a yard.

The Tokyo Electric Power Company (Tepco) that runs the site insists that the facility is now safe but in the immediate aftermath of the 6.8 magnitude tremor, it was forced to make a series of startling admissions. The plant was not designed to withstand such a strong a earthquake, radioactive material leaked into the sea and air and dozens of drums containing toxic waste broke apart.

The admission that most stunned Japan, however, was that the site, which Tepco had insisted in the High Court was nowhere near an active faultline, was in fact built directly above one. The long, straight ridge and crevice that now runs alarmingly through the middle of the Kashiwazaki plant, said one of Japan’s most respected seismologists, clearly proves that.

That faultline now threatens the future of Kashiwazaki. Katsuhiko Ishi-bashi, the Seismology Professor of Kobe University who resigned from the Government’s nuclear safety advisory panel because he doubted its independence, believes that it must be closed forever. “Even by the Government’s own guidelines, the land on which Kashiwazaki stands is completely disqualified as a suitable place to build a power plant,” he said.

Others disagree, suggesting that it is only a matter of time before the plant is back in operation. Haruki Madarame, a University of Tokyo professor of nuclear engineering and chairman of the government committee studying the impact of the July 16 earthquake, was also visiting Kashiwazaki yesterday.

“Looking at it, there was no damage on important machinery and equipment. But whether the soundness is really retained or not cannot be known until we examine the plant in more detail,” he said. “Until then, we cannot consider restarting the plant.”

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