Wednesday, December 28, 2011

"Now They Tell Us" Series: NISA Says Reactors 1 and 3 Explosions May Have Been Caused by Vent

(In case you haven't read about it during my absence...)

Nikkei Shinbun reports that NISA admitted the hydrogen explosions that took place in Reactor 1 and Reactor 3 at Fukushima I Nuclear Power Plant in March may have been caused by hydrogen flowing back from the exhaust stack. In other words, vent may have caused the explosions.

From Nikkei Shinbun (12/27/2011):

経済産業省原子力安全・保安院は27日開いた東京電力福島第1原子力発電所の事故原因に関する専門家の意見聴取会で、1、3号機の水素爆発の一因として、原子炉格納容器からベント(排気)した水素が別の排気管を通って建屋内に逆流した可能性があると公表した。津波による電源喪失で排気管の弁が開き、水素の逆流を防げなかったという。

The Nuclear and Industrial Safety Agency under the Ministry of Economy, Trade and Industry disclosed during the experts hearing on December 27 on the cause of the Fukushima I Nuclear Power Plant accident that a possible cause of the hydrogen explosions in Reactors 1 and 3 may have been that the hydrogen that was vented from the Containment Vessel [to the exhaust stack] flowed back into the reactor building through a different pipe. As the power was lost due to tsunami, the valve of this different pipe remained open, and unable to prevent the reverse flow of hydrogen, according to the NISA.

 1、3号機は炉心溶融で格納容器に水素がたまり、水素を抜くベントをした。ベントの排気管は、原子炉建屋の換気をする「非常用ガス処理系」の排気管と合流し、排気筒につながっている。

In Reactors 1 and 3, hydrogen accumulated in the Containment Vessels after the core meltdowns, and TEPCO carried out the vent in order to remove hydrogen. The exhaust pipe for the vent connects to the exhaust pipe for the "standby gas treatment system" for the air ventilation of the reactor building, and then to the exhaust stack.

 非常用ガス処理系の排気管は電源喪失時に建屋の換気を妨げないよう弁が開いた。実際に事故後の3号機の調査では弁が開いていたという。ベントをした際に水素が弁を通って建屋に逆流。格納容器の上蓋から漏れた水素と一緒に原子炉建屋に流れ込み、水素爆発したとみられる。

The valve of the exhaust pipe for the standby gas treatment system opened when the power was lost, so that the air ventilation of the reactor building would continue. In fact, the investigation of Reactor 3 after the accident showed the valve was open. When TEPCO did the vent, hydrogen may have flowed back to the reactor building through the open valve, and with the hydrogen leaked from the top lid of the Containment Vessel caused the hydrogen explosion.

 国内の他の原発も電源喪失で弁が開く構造。保安院は対策として、2本の排気管を独立させ、逆流防止弁を設置する方法を挙げた。奈良林直・北海道大学教授は「ベントを徹底的に改善する必要がある」と指摘する。

All the other nuclear reactors in Japan has the same system whereby the valve opens when the power is lost. As a countermeasure, the NISA suggests two separate exhaust pipes and installing a valve to prevent backflow. Professor Tadashi Narabayashi of Hokkaido University points out that the vent process needs to be improved fundamentally.

Narabayashi, one of the "Three Plutonium Brothers" who said the toxicity of plutonium was the same as salt, used to work for Toshiba.

So after more than 9 months since the accident NISA feels like telling the truth for some reason, now that the accident is officially "over".

The very act of venting probably caused the explosions, says NISA. How about that, GE?

Product liability lawsuits anyone?

8 comments:

Hélios said...

Dear Ultraman,

Sciatic ? It is so painful...I know that.
If you need to rest, do it.

We can wait for you and for the informations.

Good recovering

STeVe the JeW said...

pretty shocking that vents would fail after a 9.0 quake.

Anonymous said...

That particular valve should have failed shut.
The blame would be shared between NISA (who approved the design for use and then for life extension), TEPCO (who bought the design so caveat emptor DOES apply) and GE (who designed it in the first place).

Anonymous said...

And do other GE nuclear plants SHARE this design? Or other nuclear power plants. Pretty simple and deadly error....valve failure (does not shut) when power is lost..not exactly "fail safe"...GE could be looking at a pretty expensive cost for re-design or for legal actions for the desige flaw.

netudiant said...

This report deserves some real thought, not just airy dismissal as a design flaw.
The reactor containments were ruptured because some valves sealed shut when power was lost. Here we have valves staying open that also caused problems. So Prof Narabayashi is entirely right when he says that the vent process must be improved fundamentally.
A possible element of such a solution might be the use of a gravel filter mandated in Scandinavian reactors to allow direct venting of the reactor without fear of spreading a radioactive plume all over the country. That might solve some of the conflicting design requirements that helped create this disaster.

Zworld said...

Its my understanding that around 2000 they put in an emergency bypass line for venting high pressure loads, as the gas treatment system line was found not to be able to handle high pressures. It was primarily that filtering didnt work, so the emergency bypass line was just a straight shot out with no filt3ers.

All systems involved in the venting process are set to fail/open, and there are no backdraft dampers in the stack or vent lines. In essence, even without the fan system working, the pressure from the vent and the fact that hydrogen is very much lighter than air, should cause there to be a strong draft up the exhaust stack, carrying the hydrogen with it. Cam pics show this happening.

The fact that both Unit 3 and Unit 4 are airtight structures does not seem like the hydrogen would have an easy path into either, having to pass through multiple filtering systems on both lines.

I think this is more a "changing the backdrop to fit the scene" kind of thing. Tepcos been doing it since day one. I find the original explanations are usually closer to the truth, like when Tepco first reported detecting Cl.

But theyve been hiding and covering up all along, so who knows what the truth is.

Anonymous said...

Dear Ultraman, get in touch w/ John Sarno book, by example http://www.medscape.com/viewarticle/478840

Orange Undertow said...

@ anon, 10:53 AM

Citing a psychological cause is often merely the quickest and cheapest way to deal with and dismiss a patient's medical condition disregarding genuine physiological causes. In such cases, it is ethically questionable, unacceptable, bad science because it is unfalsifiable, and citing discredited pseudoscientific theories such as Freud's borders on quackery. Making such diagnoses can cause stress in patients who had none. This is also relevant to certain promoters of the evidence-free theory that 100mSv/mo even in pregnant women is harmless. Prefer consensus medical opinion. This comment is not intended to be medical advice; consult a qualified professional.

Post a Comment