Tokyo Electric Power Co. said the containment chambers of damaged reactors at its Fukushima nuclear plant were likely breached, identifying additional source of radiation leaks that may exceed Chernobyl.
Computer simulations of the meltdowns of three reactors in March indicates holes formed in chambers, the company known as Tepco said in a report.
The analysis confirms what independent researchers have said occurred after the March 11 earthquake and tsunami hit the plant. The report to the government raises fresh questions about how Tepco, which took more than two months to acknowledge fuel rods had melted, is handling the crisis, a nuclear researcher said.
“Unfortunately I can’t find any consistency in the report,” Hironobu Unesaki, a nuclear engineering professor at Kyoto University, said by phone. “Tepco hasn’t released sufficient radionuclide analysis of leaked contaminated water. Now they’ve confirmed fuel rods melted, they should also release more data including plutonium and uranium readings.”
Containment chambers surround the reactor vessel, which holds the fuel rods, and are meant to stop radiation and coolant leaks in the case of overheating.
Japan’s government in April raised the severity rating of nuclear crisis at the Fukushima Dai-Ichi nuclear plant to the highest, matching Chernobyl in 1986. At the time Tepco officials said the crippled plant may release more radiation than the Chernobyl.
Tepco shares fell 5.4 percent today to 315 yen in Tokyo. The shares are down more than 85 percent since the quake and tsunami struck.
The Fukushima plant 220 kilometers (137 miles) north of Tokyo hasn’t yet released as much radiation as Chernobyl, Junichi Matsumoto, a Tepco general manager, said yesterday. The company doesn’t expect large releases in future.
Tepco has been struggling to cool reactors and spent fuel pools to stop radiation leaks, including using pumps and fire engines to get water into the reactors to keep fuel rods and spent fuel cool after the quake and tsunami knocked out cooling systems.
Tepco’s analysis shows the No. 1 chamber has one hole and the No. 2 unit has two breaches, according to a report filed to a Japanese nuclear watchdog. Cooling systems may have been breached at the No. 3 reactor at the site, Tepco said.
“The breaches were created awhile ago, so they won’t cause rapid increases in radiation doses,” said Ken Nakajima, a professor of nuclear engineering at Kyoto University who specializes in reactor safety. “However, I’m concerned about a possible increase in tainted water leaking from the holes, which may lead to contamination of groundwater and seawater.”
Tepco yesterday confirmed meltdowns of fuel rods in the No. 2 and 3 reactors at the station north of Tokyo, which has been emitting radiation since an earthquake and tsunami knocked out power and cooling systems on March 11.
It revised the time the No. 1 reactor melted to within 15 hours of the quake, an hour earlier than it gave last week when it announced the damage to the reactor was worse than thought.