Fukushima Fun Zone: Reactor 2 still undergoing fission

[Sea Skimmer]

http://www3.nhk.or.jp/daily/english/02_38.html
TEPCO: Reactor may have gone critical

The operator of the crippled Fukushima Daiichi nuclear power plant says it found in the facility's No.2 reactor radioactive substances that could have resulted from continuous nuclear fission.

The Tokyo Electric Power Company, or TEPCO, said on Wednesday that it detected xenon-133 and xenon-135 in gas taken from the reactor's containment vessel on the previous day. The substances were reportedly in concentrations of 6 to more than 10 parts per million becquerels per cubic centimeter.

Xenon-135 was also detected in gas samples collected on Wednesday.

Radioactive xenon is produced during nuclear fission.
The half-life of xenon-133 is 5 days, and that of xenon-135 is 9 hours.

TEPCO says the findings suggest that nuclear fission may have occurred recently, not just after the March 11th accident, and that a state of criticality could have occurred temporarily in some areas.

TEPCO workers poured a boric acid solution into the reactor on Wednesday to suppress nuclear fission.

The utility says it has not found any significant change in temperature and pressure of the reactor, and that large-scale criticality did not occur.

TEPCO says the reactor's cooling process is continuing and that the firm expects to achieve cold shutdown at the plant this year as planned. But the utility also says it wants to take a close look at the situation of the plant's No.1 and 3 reactors.

Wednesday, November 02, 2011 20:37 +0900 (JST)

This is a fast evolving story, this is merely the most recent link. TEPCO has confirmed some kind of fission is still taking place, or very recently has taken place in unit 2. They are now saying that fission may be a sustained chain reactor, rather then short pulses. This is not really new... third parties have been saying fission was still taking place based off external air sampling but now TEPCO is not only confirming that, its very directly measuring it by having tapped directly into the unit 2 drywell to take direct samples.

[Lord Zentei]

TEPCO continues to amaze with their epic levels of incompetence. I have to admit that while I had very little respect for them previously, the situation has become so surreal that it's almost come full circle.

[Zixinus]

They still haven't cleaned up that mess? What is it with that reactor, is it next to some physics-defying reality bubble or what?

[Broomstick]

Yes, the mess is still there. You know what? It's going to be there for years to come. It took fourteen years to clean up from the much less serious Three Mile Island accident. Actually, if you want to get fussy technically TMI clean up is still not complete, thirty-two years later, because a certain amount was deferred until such time as the whole complex will be decommissioned as what's left isn't going anywhere until the physical structure and concrete is removed.

Get a grip on the fact that nuclear accidents on this scale are rare and no one has much experience at cleaning them up. That is both a blessing and a curse. Or perhaps you'd rather they rush and keep to some arbitrary time schedule no matter how many workers it might endanger or further problems just charging into the mess might generate?

Seriously, point me to even one agency - government, private industry, whatever - that actually knows how to clean up this sort of fucking mess. That is the one, big flaw with the notion of increasing reliance on nuclear power - while the accidents are rare, when they do happen it's one unholy shitpile and no one is sure what sort of shovel to use.

Does that absolve Fukishima's owners of all culpability in this matter? Of course not - we can all point to problems with how they've handled this. But let's not kid ourselves. NO government or utility company on the planet is really equipped to handle this sort of thing, it has to be figured out along the way. It's yet one more reason to try as hard as we can to prevent this sort of accident, but the brutal fact is that if we have nuclear power plants prevention is not enough. We really do have to have a plan for when disaster hits. We have to accept that we can neither foresee nor anticipate all situations. Shit happens.

[Zixinus]

Calm down. When I wrote "clean up" I meant "stop this mess from getting worse for the foreseeable feature and neutralize it".

[folti78]

Yes, the mess is still there. You know what? It's going to be there for years to come. It took fourteen years to clean up from the much less serious Three Mile Island accident.

Actually, if you want to get fussy technically TMI clean up is still not complete, thirty-two years later, because a certain amount was deferred until such time as the whole complex will be decommissioned as what's left isn't going anywhere until the physical structure and concrete is removed.

The reactor building of TMI-2 was off limits for more than a year after the accident. They first had to estimate the conditions inside the building, wait for the radiation to decay and vent the radioactive gases out of it, before it was deemed safe enough for human entry.
It took nearly 5 years until the reactor was safe enough that they could open it to investigate and another year until the defueling process began.

@Zixinus: Nowadays we have better technology but it doesn't mean we don't have to wait for radiation levels to drop before sending in just the robots to look around. The responsible parties are still in the process of figuring out what's the exact situation inside the containment.

Calm down. When I wrote "clean up" I meant "stop this mess from getting worse for the foreseeable feature and neutralize it".

Thats not cleanup, just damage control.

[Ellindsey]

Latest word is that the fission that's going on is just the breakdown of unstable transuranic elements in the core and not signs of an ongoing chain reaction.

http://www.bloomberg.com/news/2011-11-0 ... ction.html

[K. A. Pital]

Latest word is TEPCO (or the Japanese government?) sent their engineers to Belorussia to gather experience on the Chernobyl liquidation. They should have done it like months ago.

[The Duchess of Zeon]

Latest word is that the fission that's going on is just the breakdown of unstable transuranic elements in the core and not signs of an ongoing chain reaction.

http://www.bloomberg.com/news/2011-11-0 ... ction.html

These days? Possibly. But I said it back when it happened and I still think it's true that some kind of criticality incident occurred after the nominal shutdown, and there may have been spikes of criticality straight into May.

[Sea Skimmer]

I would not believe a damn word TEPCO says on this which attempts to so conveniently minimize the problem. They've lied at every chance they've gotten, ever over really stupid stuff, and long before this gas sample made the problem impossible to deny many people had pointed out spikes in gas releases of a very large scale, not something you'd get from a tiny bit of fission. Spikes of criticality likely happened through July if not later that could have come from any one of three reactors, TEPCO is only examining one due to them being inept as hell (for anyone talking about robots, they basically have TWO in use). A truly sustained chain reaction is unlikely, but a lot of evidence supports pulses of criticality, some of which may have lasted days. You wouldn't expect anything to sustain itself all that long, because the fuel would melt again and change its configuration.

Of course it is possible that multiple things are going on at the same time, with parts of the core going critical at times and others undergoing lesser fission. If TEPCO really wanted to deny criticality they'd stick some neutron detectors into the core via whatever port they are using to take gas samples and settle the matter. If they don't do that real soon I think its very safe to say they are full of shit.

Meanwhile it looks like Japan is going to study building Tokyo-3
http://www.dailymail.co.uk/news/article ... Tokyo.html

[CJvR]

They need to fire their PR department, they are not a bunch of reality show participants; point is NOT getting headlines!!!

http://www3.nhk.or.jp/daily/english/03_19.html

TEPCO retracts criticality call

The operator of the Fukushima nuclear power plant has retracted an earlier assessment that a continuous nuclear reaction, or a criticality, could have taken place in the damaged Number 2 reactor.

The Tokyo Electric Power Company, or TEPCO, said on Thursday that the small amount of xenon-135 it detected in gas taken from the reactor's containment vessel was the result of the spontaneous nuclear fission of radioactive curium-242 and -244. The two substances are contained in nuclear fuel.

The amount of xenon-135 detected almost matched the amount that would have been produced if the radioactive curium in the fuel had undergone spontaneous fission.

TEPCO says a criticality event would have resulted in higher levels of xenon concentration.

Spontaneous fission refers to the nuclear fission of radioactive materials other than uranium, and it does not lead to criticality. Such fission is said to occur constantly.

The earlier detection of small amounts of Xenon-135 had suggested the possibility of a criticality occurrence in the melted fuel in the damaged reactor.

TEPCO sys it will send the assessment to the Nuclear and Industrial Safety Agency for reevaluation.

[Aleva13]

Meanwhile it looks like Japan is going to study building Tokyo-3
http://www.dailymail.co.uk/news/article ... Tokyo.html

Wouldn't that technically be Tokyo-2?