Japanese officials may only have hours to cool reactors that have been disabled by Friday’s massive earthquake and tsunami or face a nuclear meltdown.
Tokyo Electric Power Co (TEPCO) (9501.T) is racing to cool down the reactor core after a highly unusual “station blackout” — the total loss of power necessary to keep water circulating through the plant to prevent overheating.
Daiichi Units 1, 2 and 3 reactors shut down automatically at 2:46 p.m. local time due to the earthquake. But about an hour later, the on-site diesel back-up generators also shut, leaving the reactors without alternating current (AC) power.
That caused Tepco to declare an emergency and the government to evacuate thousands of people from near the plant. Such a blackout is “one of the most serious conditions that can affect a nuclear plant,” according to experts at the Union of Concerned Scientists, a U.S. based nuclear watchdog group.
“If all AC power is lost, the options to cool the core are limited,” the group warned.
TEPCO also said it has lost ability to control pressure at some of the reactors at its Daini plant nearby.
The reactors at Fukushima can operate without AC power because they are steam-driven and therefore do not require electric pumps, but the reactors do require direct current (DC) power from batteries for its valves and controls to function.
If battery power is depleted before AC power is restored, the plant would stop supplying water to the core and the cooling water level in the reactor core could drop.
Officials are now considering releasing some radiation to relieve pressure in the containment at the Daiichi plant and are also considering releasing pressure at Daini, signs that difficulties are mounting. Such a release has only occurred once in U.S. history, at Three Mile Island.
“(It’s) a sign that the Japanese are pulling out all the stops they can to prevent this accident from developing into a core melt and also prevent it from causing a breach of the containment (system) from the pressure that is building up inside the core because of excess heat,” said Mark Hibbs, a nuclear expert at the Carnegie Endowment for International Peace.
While the restoration of power through additional generators should allow TEPCO to bring the situation back under control, left unchecked the coolant could boil off within hours. That would cause the core to overheat and damage the fuel, according to nuclear experts familiar with the Three Mile Island accident in Pennsylvania in 1979.
It could take hours more for the metal surrounding the ceramic uranium fuel pellets in the fuel rods to melt, which is what happened at Three Mile Island. That accident essentially frozen the nuclear industry for three decades.
Seven years later the industry suffered another blow after the Chernobyl plant in Ukraine exploded due to an uncontrolled power surge that damaged the reactor core, releasing a radioactive cloud that blanketed Europe.
The metal on the fuel rods would not melt until temperatures far exceed 1,000 degrees F. The ceramic uranium pellets would not melt until temperatures reached about 2,000 degrees F, nuclear experts said.
Second Nuclear Reactor with Problems
Reports are emerging from Japan of a second nuclear reactor experiencing problems after a 8.9-magnitude earthquake struck the country, the largest in its history. Few details about the second plant are available at this time.
Meanwhile, at the crippled Fukushima Daiichi nuclear power plant, Japanese nuclear officials report radiation levels inside the plant have surged to 1,000 times their normal levels after the cooling system failed.
The earthquake was 1,000 times more powerful than the one that struck Christchurch in New Zealand recently. It was also a thousand times more powerful than the quake that hit Haiti last year.
The elevated reading was taken in the control room of the No. 1 reactor of the power plant, Agence France-Presse reported.
Pressure inside one of six boiling water reactors at the plant had risen to 1.5 times the level considered normal and authorities ordered an evacuation of a two-mile radius area adjacent to the plant. Around 3,000 people have evacuated their homes as the government declared a first of its kind nuclear emergency. People within a six-mile radius were warned to stay in their homes.
The 480-megawatt Fukushima Daiichi nuclear power plant is a hundred times more powerful than the ill-fated reactor at the Chernobyl plant in Ukraine. On April 26, 1986, the Soviet reactor exploded after a power surge. Four hundred times more radioactive material was released from the crippled nuclear power plant than had been by the atomic bomb at Hiroshima. The fallout was detected across Europe.
The loss of coolant at the Three Mile Island Nuclear Generating Station in Pennsylvania in 1979 for only 30 minutes led to a 50% meltdown of the core.
At least 11 of Japan’s 52 nuclear power reactors are shut down and three of those may pose a danger to the public, the Christian Science Monitor reports.
“If they can’t get adequate cooling to the core, it could be a Three Mile Island or worse,” nuclear physicist Edwin Lyman of the Union of Concerned Scientists told the Los Angeles Times.