UPDATED 11:22 PM EST -- A second explosion has been reported at Japan's Fukushima Daiichi nuclear plant, this time at the building containing unit 3.
"A fresh explosion that rocked Japan's quake-stricken Fukushima Daiichi nuclear power complex on Monday has not damaged the plant's No.3 reactor vessel, news agency Jiji said, quoting the plant's owner, Tokyo Electric Power Co ."
Earlier on Sunday, officials warned such an explosion might occur as Tepco flooded the reactor with seawater and boric acid. Experts believe the unit 1 explosion likely was caused by vented hydrogen that formed when water contacted damaged fuel cladding in the core.
The Kyodo News Agency Sunday reported coolant issues at a third Japanese nuclear plant, bringing the total number of reactors with electrical or cooling problems following Friday's earthquake to seven.
The Kyodo bulletin read:
"The Fire and Disaster Management Agency said a cooling system pump stopped operating at Tokai No. 2 Power Station, a nuclear power plant, in the village of Tokai, Ibaraki Prefecture."
Later Sunday, officials reported that a backup coolant system was functioning, and that core temperatures and pressures were dropping.
Owned by the Japan Atomic Power Company, Tokai No. 2 is Japan's oldest commercial nuclear plant. It uses an 1,100 megawatt boiling water reactor placed into service in 1978. According to the Asian Nuclear Safety Network, the plant design features a General Electric BWR 5 reactor design with Mark II containment, which is somewhat newer and stronger than the Mark I containment at Fukushima Daiichi unit one.
Japanese officials suspect core damage in two reactors at Japan's Fukushima Daiichi nuclear plant following a catastrophic earthquake and tsunami that knocked out backup power to the plant's coolant systems.
Experts surmised that an explosion Saturday at Fukushima Daiichi unit one likely followed a hydrogen buildup caused by vented steam that had been in contact with damaged fuel cladding. Then, late Saturday, an Associated Press report indicated another reactor -- unit 3 -- may also be showing signs of core damage. The news agency quoted Japan's Chief Cabinet Secretary Yukio Edano as saying “because it's inside the reactor, we cannot directly check it. But we are taking measures on the assumption of the possible partial meltdown.”
Plant owner Tokyo Electric Power has overseen atmospheric releases of irradiated air from unit 3, where media reports said radiation readings briefly exceeded legal limits before declining. Edano also indicated in the AP report that low coolant levels left unit 3's fuel rods exposed for a period.
Tepco issued this statement regarding unit 3:
"High Pressure Coolant Injection System of Unit 3 automatically stopped. We endeavored to restart the Reactor Core Isolation Cooling System but failed. Also, we could not confirm the water inflow of Emergency Core Cooling System. As such, we decided at 5.10AM, Mar 12, and we reported and/or noticed the government agencies concerned to apply the clause 1 of the Article 15 of the Radiation Disaster Measure at 5:58AM, Mar 13. In order to fully secure safety, we operated the vent valve to reduce the pressure of the reactor containment vessels (partial release of air containing radioactive materials) and completed the procedure at 8:41AM, Mar 13."
Japanese officials also indicated they will initiate atmospheric steam releases from three reactors at the nearby Fukushima Daini Plant, which also suffered power failures.
Attempts to cool the overheated unit 1 reactor at Fukushima Daiichi by pumping seawater and boric acid into its cooling system resulted in an explosion, the Associated Press reported Saturday. Video of the plant shows a sizable blast consuming the reactor's outer building, where hydrogen reportedly built up from water in contact with the superheated reactor.
The reactor's primary containment is still in tact, officials said, adding that radiation readings around the plant have gone down since the explosion. Previous readings indicated radiation levels 1,000 times normal in unit 1's control room and 8 times normal at the plant gate. Officials have indicated both readings were not interpreted as a major health concern.
Japanese authorities are reported as saying the explosion may indicate core damage. Per Japan's Nikkei news service:
"The Nuclear and Industrial Safety Agency (NISA) said Saturday afternoon the explosion at the Fukushima No. 1 nuclear plant could only have been caused by a meltdown of the reactor core.
The same day, Tokyo Electric Power Co., which runs the plant, began to flood the damaged reactor with seawater to cool it down, resorting to measures that could rust the reactor and force the utility to scrap it.
Cesium and iodine, by-products of nuclear fission, were detected around the plant, which would make the explosion the worst accident in the roughly 50-year history of Japanese nuclear power generation."
CNN International quoted an expert as saying the gas likely moved from the closed reactor cooling system to the exterior reactor housing during steam venting announced earlier. The news service quoted Malcolm Grimston, Associate Fellow for Energy, Environment and Development at London's Chatham House as saying:
"Because they lost power to the water cooling system, they needed to vent the pressure that's building up inside.
"My suspicion is that as the temperature inside the reactor was rising, some of the metal cans that surround the fuel may have burst and at high temperature, that fuel cladding can react with water to produce zirconium oxide and hydrogen.
"That hydrogen then will be part of the gases that need to be vented. That hydrogen then mixes with the surrounding air. Hydrogen and oxygen can then recombine explosively.
"So it seems while the explosion wasn't directly connected with the nuclear processes, it was indirectly connected, because the hydrogen was only present because of what was going on in the reactor core."
Earlier Tokyo Electric Power Company officials reported that 1.7 meters of the 4.5 meter-long fuel rods at Fukushima Daiichi's Unit 1 may have been exposed to air as power problems in the coolant system cased water levels in the reactor to drop.
Media reports also indicated the utility has released irradiated steam from the reactor into the atmosphere to control pressure within the reactor and its containment vessel. The plant now faces the possibility of fuel damage as operators work to replace electrical systems and add coolant.
Early Saturday morning The Wall Street Journal quoted a Tepco spokesman as saying "if the water level remains at this level, the reactor core might be damaged, but we are now pouring water into the reactor to prevent it from happening."
Power systems failed at the plants after an earthquake struck the northeast coast of Japan early Friday morning, killing thousands and creating a tsunami that inflicted massive damage to coastal communities and raised alarms as far away as Peru. The 8.9 magnitude quake, reportedly the biggest in Japan in 140 years, is believed to have disabled a backup diesel generator system at Fukushima Daiichi. While all 6 reactors at the Tokyo Electric Power Co. plant scrammed or had been down for inspections, a buildup of decay heat in unit 1 has raised alarm among plant operators.
As of Friday afternoon, additional backup generators were en route to the plant, and unit 1's coolant system was running temporarily on a battery. Japanese regulators stated that pressure in the reactor had risen to 1.5 times normal levels. At 750 degrees, an engineer familiar with the BWR design told the Los Angeles Times Friday, the temperature is well below the 2,200-degree design limit for preventing cladding failure.
NPR quoted a defense ministry official as saying troops trained for chemical disasters and four special vehicles had been sent to the plant in case of a radiation leak.
Nearby residents had been evacuated earlier. Per the BBC:
"Japan's government has declared an emergency situation at the Fukushima Daiichi nuclear plant after a reactor cooling system malfunction. But officials say there is no radiation leaking. Some 3,000 residents living near the plant in Fukushima prefecture, north of Tokyo, have been told to evacuate the area."
Later, evacuations were expanded to a 20 km radius surrounding the plant.
Previously, a 7.2 magnitude earthquake rocked the country Wednesday. The country's nuclear plants were not damaged. Japan strengthened earthquake safeguards at its nuclear plants after a similar-sized tremblor in 2007 damaged the 7-reactor Kashiwazaki-Kariwa station, then the world’s largest nuclear plant. While the reactors were unharmed, radioactive water leaked into the sea and barrels of low-level waste tipped over.
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The latest news I can find on your website it over two days old.
If this is the most current you can publish.....I need to find someone who
can furnish current situation reports in a timely manner. Got any suggestions?
Bill , You are commenting on a news story that was published 2 days ago?? The home page has the lateset news and is kept up to date as news is released.