Third Explosion at Fukushima – Reactor Unit 2

LATEST: Radiation at plant ‘3 times normal levels’ | Explosion heard in suppression chamber (unlike previous explosions); All but ‘critical’ workers evacuated | Fuel rods half exposed (2.7 meters); Concern that core containment vessel may have been damaged… blast was in bottom of vessel, indicating something wrong in last line of defense. Nuclear expert says plunge in pressure means there could be damage to vessel – the last line of defense. Very serious.

I was working on an UPDATE (not finished yet), concerning Fukushima Daiichi’s reactor Unit 2 on last night’s live blog thread following the explosion at Unit 3, when news just broke at 6:14am local time, that there has now been an explosion at the Unit 2 reactor.

The new explosion follows two others, said to have been hydrogen explosions first at Unit 1, and then Unit 3 a day later, and news late last night that the emergency cooling system at Unit 2 had been damaged during the Unit 3 blast, resulting in the uranium fuel rods at 2 becoming dangerously, and completely exposed for a number of hours before sea water injection was resumed in hopes of cooling the number 2 reactor.

Now, according to various reliable sources on Twitter over the last few minutes…

“@thedeadhandbook: NHK: “A big sound” at Unit No 2. Half of fuel rods 2.7 meter length is exposed.”

“@thedeadhandbook: NHK: operators evacuated from the site ‘just in case.’ Damage to “pressure suppression room”

“@Reuters: Fresh explosion heard at stricken Japan reactor http://reut.rs/gQJl88”

“@norishikata: We need to very closely watch what is happening to Unit 2. Most workers on-site evacuated, with minimum staff remaining.”

“@AkikoFujita: Explosion at Reactor unit #2 at 6:10am. Gov’t: “Radioactive levels up, but level not immediately harmful to human bodies.”

“NHK: NISA says rad levels not high to cause damage to human health, but if containment vessel damaged could be serious consequences”

In the case of Units 1 & 3, according to Japanese officials, the containment vessels housing the fuel rods were not breached, though “partial meltdowns” of at least some of the rods was being presumed. Whether or not that is the case again in Unit 2, now remains to be seen…

4:57pm PT: More now, still troubling, from NHK’s coverage of the Tokyo Electric Power Co. (TEPCO) news conference, as tweeted by @TheDeadHandbook…

“NHK notes there is a danger of contaminated water leaking out. still need to bring up water level. “a very serious situation”

“NHK: TEPCO: reporters pressing for information about possible damage to containment, but answers were vague.”

NHK: showing chart again that blast was in bottom of vessel, indicating something wrong in last line of defense”

“NHK: nuclear expert says plunge in pressure means there could be damage to vessel. the last line of defense. very serious”

“NHK: nuclear expert says does not mean immediate leak of radiation. water injection will continue.”

“NHK: nuclear expert notes that pressure in vessel was brought down to accomodate injection of water”

IDG News Services Tokyo bureau chief Martyn Williams, also covering the TEPCO news conference, adds:

“Tepco erred by starting with apology – making it seem big increase in seriousness – then unable to follow with simple explanation”

The Daily Yomiuri adds:

“Water levels are reportedly being restored at the No2 reactor at the Fukushima No1 nuclear plant. Rods now 2.8m exposed.”

“Radiation levels outside the main gate of the Fukushima No1 nuclear plant were reported as 16 times normal levels.”

Very good video coverage in English on NHK World streaming here…

5:14pm PT: Communications Director for PM’s office, Noriyuki Shikata, tweets:

“Please do not try to physically approach Unit 2 of Fukushima Daiichi for media coverage or other purposes.

“TEPCO says, the number of remaining workers on-site Unit 2 is around 50 people.”

5:46pm PT: VOA’s Steve Herman tweets that the Kyodo News Agency is reporting: “Fukushima’s No. 2 reactor container damaged, radiation leak feared.”

To explain that concern very quickly, there are several containers around the nuclear fuel for the reactor. The fuel itself is inside rods, which are, in turn, inside a steal and concrete container vessel, currently filled — or partially filled, in this case — with sea water, to try and cool the fuel rods. If the container vessel, “the last line of defense from keeping the radioactivity from being released,” has, in fact, been damaged by the explosion, fuel and radioactivity could leak into the environment.

Still trying to get hard confirm whether the vessel was breached (unlike at Units 1 & 3 before, where officials say the container was not breached when they had their own explosions previously.)

“This is a very serious situation” and could be a “worst case scenario”, according to the TEPCO official who gave a press conference within the past hour.

“There seems to be some faults with the compression pool,” which is the container vessel, reports NHK.

6:04pm PT: Here is Kyodo’s actual, one line report on damage to the reactor Unit 2 container vessel:

TOKYO (Kyodo)–Radiation is feared to have leaked after the container vessel was damaged at the No. 2 reactor of the Fukushima nuke plant Tuesday morning, Tokyo Electric Power Co. (9501) said.

…DEVELOPING…

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Updates from CLG:

Radiation Is Leaking At Ibaraki –Radiation leaking due to core problem at Fukushima Unit 2 Nuclear Reactor 15 Mar 2011

Japan Reports: Explosion At Third Reactor —Govt trying to prevent meltdowns in three nuclear reactors 14 Mar 2011 A fresh explosion was heard on Tuesday at a quake-stricken Japanese nuclear power plant, the country’s nuclear safety agency said. Authorities at the Fukushima Daiichi complex, damaged in Friday’s 9.0 magnitude earthquake and tsunami, are trying to prevent meltdowns in three of the plant’s nuclear reactors. Two previous explosions ripped through unit 1 and 3 reactor buildings, but these had not damaged the nuclear vessels, authorities have said. There was no immediate word on any damage from this third blast, which is now believed to have occurred in the remaining reactor, unit 2.

Plutonium threat at Japan reactor, expert warns —The Fukushima facility began using MOX fuel last September, becoming the third plant in Japan to do so. 14 Mar 2011 The fuel used in the Japanese nuclear reactor where an explosion occurred today is more volatile and toxic than the fuel used in the other reactors there, a Japanese nuclear expert warned. At a press conference in Tokyo, Masashi Goto, who worked for Toshiba as a reactor researcher and designer, said the mixed oxide (MOX) fuel used in unit 3 of the Fukushima Daiichi nuclear plant contains plutonium, which is much more toxic than the fuel used in the other reactors. MOX fuel is a mixture of uranium and plutonium reprocessed from spent uranium, and is sometimes involved in the disposal of weapons-grade plutonium.