The pressure increase meant plant operators may need to deliberately release radioactive steam, prolonging a nuclear crisis that has consumed government attention even as it responded to the catastrophic earthquake and tsunami that savaged Japan on March 11.
Beyond the disaster area, an already shaken public grew uneasy with official reports that traces of radiation first detected in spinach and milk from farms near the nuclear plant are turning up farther away in tap water, rain and even dust.
In all cases, the government said the radiation levels were too small to pose an immediate risk to health. Still, Taiwan seized a batch of fava beans from Japan found with faint — and legal — amounts of iodine and cesium.
All six of the Fukushima Dai-ichi nuclear complex’s reactor units saw trouble after the disasters knocked out cooling systems. But officials reported headway this weekend in reconnecting two units to the electric grid and in pumping seawater to cool reactors and replenish bubbling or depleted pools for spent nuclear fuel.
Temperatures in storage pools for Units 5 and 6 continued their several days of decline on Sunday to a safe, cool level, the nuclear safety agency said.
But the buildup in pressure inside the vessel holding Unit 3’s reactor renewed the danger, forcing officials to consider venting. The tactic produced explosions during the early days of the crisis.
“Even if certain things go smoothly there would be twists and turns,” Chief Cabinet Secretary Yukio Edano said. “At the moment, we are not so optimistic that there will be a breakthrough.”
Nuclear safety officials said one of the options could release a cloud dense with iodine as well as the radioactive elements krypton and xenon.
The plant’s operator, Tokyo Electric Power Co, temporarily suspended the plans on Sunday after it said the pressure inside the reactor stopped climbing, though at a high level. “It has stabilised,” said Tokyo Electric manager Hikaru Kuroda.
Kuroda, who said temperatures inside the reactor reached 572 Fahrenheit degrees (300 degrees Celsius), said the option to release the highly radioactive gas inside is still under consideration if pressure rises.
Growing concerns about radiation add to the overwhelming chain of disasters Japan has struggled with since the 9.0-magnitude quake. Fuel, food and water remain scarce. The government in recent days acknowledged being caught ill-prepared by an enormous disaster that the prime minister has called the worst crisis since World War II.
Bodies are piling up in some of devastated communities and badly decomposing even amid chilly rain and snow.