The 'why I am not worried' article, edited by MIT nuclear scientists • Hacker News Board

Re: The 'why I am not worried' article, edited by MIT nuclear scientists

#51

Post by marshray » Wed, Mar 16, 2011, 7:05 AM UTC

cperciva wrote: post #48

timr wrote: post #36

Earlier quoted context omitted.

"All good engineering works on the principle of defence in depth." That line is as much a sound-bite at this point as anything you'll hear on cable television. Yes, good engineering has many levels of fall-backs and redundancies. But when you've reached the point that you've evacuated the last fifty people from your site because it's no longer safe for them to be there , then you've exhausted your defenses. There's n…

Maybe the "wide concrete tray" will capture the waste. Maybe it won't. Maybe the laws of physics will change, but I'd be willing to bet that they won't. But in the meantime, you're hoping that there's not a secondary fire from the heat Concrete doesn't burn. or a steam explosion At the point when the nuclear fuel melts, all the water has boiled off 1000 degrees ago. or some other kind of explosion that flings radioac…

Sure the laws of physics don't change. But the state of this complex system is way way out of understood and explored space at this point.

http://www.digitalglobe.com/downloads/featured_images/japan_...

This game was out of the playbook from the beginning, as soon as all the batteries and backup generators failed.

Re: The 'why I am not worried' article, edited by MIT nuclear scientists

#52

Post by marshray » Wed, Mar 16, 2011, 7:13 AM UTC

Confusion wrote: post #49

Duff wrote: post #23

I'm really kind of sick of listening to people talk about how everything is hunky-dory. I heard one supposed expert on CNN basically state that a nuclear meltdown is no big deal. The lesson to learn here is when a government tells you everything is ok regarding an event with potential regional impact, get the hell out of town. I'm assuming the reactors are melting down and are out of control. Pumping seawater in may…

According to the IAEA, Reactors 1-3 have been in cold shutdown since yesterday, which means they finally are where they were supposed to end up, in a stable situation where no water is boiling off anymore, so all the risk is gone.

It seems that the IAEA is not a useful source of up-to-date information here. Apparently they're bound by agreements not to say anything without TEPCO's approval. The little they've said has been hours or days late.

Unit 2 and 3 are believed to have lost containment integrity. Unit 3 is currently billowing smoke/steam.

Re: The 'why I am not worried' article, edited by MIT nuclear scientists

#53

Post by rimantas » Wed, Mar 16, 2011, 7:32 AM UTC

kitsune_ wrote: post #50

This is BULLSHIT, the guy (Oehmen) is a mechanical engineer with a management focus. He worked at my alma mater (ETHZ). His field of experties is supply chain risk management. Look up his papers, he isn't a nuclear physicist. I'd say he's about as qualified to make a comment on the situation as I am. The "essay" by Oehmen was first published by a notorious nuclear lobbyist, Jason Morgan. Look at this: http://nuclearf…

> In short: FUD by nuclear energy lobbyists.

So mechanical engineer cannot possibly say anything truthful about nuclear energy?

The fact still remains: nuclear energy is the safest and cleanest we have for now.

So far we had what, three serious incidents with total number of causalities of 35, all in Chernobyl. Sure it affected much more people but still: the single incident at Sayano-Sushenskoye hydroelectric power plant claimed 75 lives. How about Banqiao Dam?

  According to the Hydrology Department of Henan Province,[5] in the
  province, approximately 26,000 people died from flooding and another
  145,000 died during subsequent epidemics and famine. In addition, about
  5,960,000 buildings collapsed, and 11 million residents were affected.

And thats not counting all the incidents in coal and oil industry (and the fact that burning coal releases more radiation for the same amount of energy produced than nuclear power plants).

Re: The 'why I am not worried' article, edited by MIT nuclear scientists

#54

Post by wladimir » Wed, Mar 16, 2011, 7:54 AM UTC

kitsune_ wrote: post #50

This is BULLSHIT, the guy (Oehmen) is a mechanical engineer with a management focus. He worked at my alma mater (ETHZ). His field of experties is supply chain risk management. Look up his papers, he isn't a nuclear physicist. I'd say he's about as qualified to make a comment on the situation as I am. The "essay" by Oehmen was first published by a notorious nuclear lobbyist, Jason Morgan. Look at this: http://nuclearf…

It reads very much like a last-ditch effort by nuclear energy lobbyists to convince us that nuclear energy is really safe. This brings back memories of the Iraqi information minister.

In 15 years, if there are no further disasters, they might crawl out of their holes and start preaching about the wonders of nuclear energy again. Until then, just give up.

Re: The 'why I am not worried' article, edited by MIT nuclear scientists

#55

Post by wtallis » Wed, Mar 16, 2011, 7:57 AM UTC

wazoox wrote: post #39

bgrainger wrote: post #34

One small nitpick: if earthquakes were still measured on the Richter scale, the difference between 8.2 and 8.9 would be 5 times (as stated in the corrected article). However, the USGS uses the Moment magnitude scale (M_w, see http://earthquake.usgs.gov/earthquakes/glossary.php#magnitud... and http://en.wikipedia.org/wiki/Moment_magnitude_scale for details), so the difference between an 8.2 and an 8.9 is 11.2 times--m…

AFAIK, all reports of the magnitude were on the Richter scale.

I'd suspect that at least half of the journalists reporting on this don't even know that there is a replacement for the Richter scale. Particularly with translation involved, it's pretty easy for one publication to drop the reference to the moment scale and the next publication to reattach the Richter name to the number.

Re: The 'why I am not worried' article, edited by MIT nuclear scientists

#56

Post by timr » Wed, Mar 16, 2011, 8:08 AM UTC

cperciva wrote: post #48

timr wrote: post #36

Earlier quoted context omitted.

"All good engineering works on the principle of defence in depth." That line is as much a sound-bite at this point as anything you'll hear on cable television. Yes, good engineering has many levels of fall-backs and redundancies. But when you've reached the point that you've evacuated the last fifty people from your site because it's no longer safe for them to be there , then you've exhausted your defenses. There's n…

Maybe the "wide concrete tray" will capture the waste. Maybe it won't. Maybe the laws of physics will change, but I'd be willing to bet that they won't. But in the meantime, you're hoping that there's not a secondary fire from the heat Concrete doesn't burn. or a steam explosion At the point when the nuclear fuel melts, all the water has boiled off 1000 degrees ago. or some other kind of explosion that flings radioac…

"Maybe the laws of physics will change, but I'd be willing to bet that they won't."

There's absolutely nothing about the "laws of physics" that guarantees that this particular reactor design is going to be able to contain a full meltdown, because it's never happened before. Nobody knows.

"Concrete doesn't burn."

No one said it did. There's plenty of other stuff around that does burn readily, which is why the plant is currently on fire. A lot of that stuff is radioactive.

"Explosions don't just happen for no reason."

Indeed. But red-hot piles of radioactive waste are a good way of making explosions happen, particularly when there's lots of hydrogen gas floating around from the breakdown of the cooling water and the fuel. That's why there have been several explosions at the plant.

"Nuclear reactors don't hold enough fuel to form a critical mass. In order to become critical, they need a moderator (usually water) which thermalizes neutrons."

You're assuming an intact core. Criticality is a function of density, shape and temperature, in addition to mass. Melt the fuel rods, and the guarantees of that nice, well-moderated behavior are off.

In general, you're making lots of simplistic assumptions about a nicely behaved, engineered, controlled system. What they've got now is far messier. Moreover, a lot of the stuff that you're saying can't happen, is actually happening right now. The reality of the situation trumps your theories of the situation, however confident.

Re: The 'why I am not worried' article, edited by MIT nuclear scientists

#57

Post by woodpanel » Wed, Mar 16, 2011, 8:11 AM UTC

gojomo wrote: post #12

This was quite a 'walk-back' of the original headline. It started as "Why I am not worried about Japan’s nuclear reactors" on one site. The title is now "Modified version of original post written by Josef Oehmen", with the content modified and moved to another site. It also now includes a disclaimer "Note that the title of the original blog does not reflect the views of the authors of the site." Perhaps they should j…

Perhaps they should just come out and say, "we're experts but please, stop mailing us questions".

In my view, the reason why this new version is less enjoyable to read is, that they've just precised the numbers, labels and terms rather than the conclusion.

Re: The 'why I am not worried' article, edited by MIT nuclear scientists

#58

Post by woodpanel » Wed, Mar 16, 2011, 8:20 AM UTC

cperciva wrote: post #48

timr wrote: post #36

Earlier quoted context omitted.

"All good engineering works on the principle of defence in depth." That line is as much a sound-bite at this point as anything you'll hear on cable television. Yes, good engineering has many levels of fall-backs and redundancies. But when you've reached the point that you've evacuated the last fifty people from your site because it's no longer safe for them to be there , then you've exhausted your defenses. There's n…

Maybe the "wide concrete tray" will capture the waste. Maybe it won't. Maybe the laws of physics will change, but I'd be willing to bet that they won't. But in the meantime, you're hoping that there's not a secondary fire from the heat Concrete doesn't burn. or a steam explosion At the point when the nuclear fuel melts, all the water has boiled off 1000 degrees ago. or some other kind of explosion that flings radioac…

I may ask you about the spent fuel disposals that seem to be on fire.

Are they within the containment? This picture doesn't clear things up for me (http://en.wikipedia.org/wiki/File:BWR_Mark_I_Containment_ske...)? And if so and if they are on fire, does the containment still work?

And if they are not within the containment, aren't we f..ked? Isn't the greatest risk of nuclear plants not the reactor but the proper waste disposal? Storing it near a nuclear plant seems to be idiotic.

EDIT: Most news articles read like there was a waste disposal next to the plants and outside of the containment

EDIT 2: http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300...

Re: The 'why I am not worried' article, edited by MIT nuclear scientists

#59

Post by dexen » Wed, Mar 16, 2011, 8:37 AM UTC

cperciva wrote: post #28

Duff wrote: post #23

I'm really kind of sick of listening to people talk about how everything is hunky-dory. I heard one supposed expert on CNN basically state that a nuclear meltdown is no big deal. The lesson to learn here is when a government tells you everything is ok regarding an event with potential regional impact, get the hell out of town. I'm assuming the reactors are melting down and are out of control. Pumping seawater in may…

I heard one supposed expert on CNN basically state that a nuclear meltdown is no big deal. He's right, in a sense. Modern nuclear reactors are designed so that if the fuel melts it will end up in a wide concrete tray which sits under the reactor, where -- thanks to the fact that the tray is very wide and not at all deep -- it will cool down to a safe temperature. All good engineering works on the principle of defence…

EDIT: nvm, found the answer by re-reading the article.

In short, even without chain reaction, substantial (7% of normal output early after shutdown) heat is produced, so some cooling is needed.

--

The original post:

Why are (or were) they pumping water in anyway? Wasn't the whole point of reactors moderated by water that once the moderating water escapes (evaporates or flows out), the unmoderated neutrons don't sustain chain reaction anymore and it basically ceases to produce heat?

Re: The 'why I am not worried' article, edited by MIT nuclear scientists

#60

Post by [deleted] » Wed, Mar 16, 2011, 8:37 AM UTC

rimantas wrote: post #53

kitsune_ wrote: post #50

This is BULLSHIT, the guy (Oehmen) is a mechanical engineer with a management focus. He worked at my alma mater (ETHZ). His field of experties is supply chain risk management. Look up his papers, he isn't a nuclear physicist. I'd say he's about as qualified to make a comment on the situation as I am. The "essay" by Oehmen was first published by a notorious nuclear lobbyist, Jason Morgan. Look at this: http://nuclearf…

> In short: FUD by nuclear energy lobbyists. So mechanical engineer cannot possibly say anything truthful about nuclear energy? The fact still remains: nuclear energy is the safest and cleanest we have for now. So far we had what, three serious incidents with total number of causalities of 35, all in Chernobyl. Sure it affected much more people but still: the single incident at Sayano-Sushenskoye hydroelectric power…

[deleted]