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

#111

Post by moe » Wed, Mar 16, 2011, 4:01 PM UTC

Travis wrote: post #107

moe wrote: post #95

Earlier quoted context omitted.

Are you serious? According to [1] roughly 15k people died in plane accidents over the past decade. It doesn't seem unreasonable to assume that Chernobyl killed many more than that. Furthermore a nuke meltdown renders a large area uninhabitable and leaves an economic footprint "slightly" bigger than a few planes coming down every year. Quote from [2] (page 33): Coping with the impact of the disaster has placed a huge…

I looked at your first source, and immediately noticed that the 2001 death toll does not count those who died in the WTC collapse (article states for 2001, 200 accidents, 1534 dead, so it doesn't include ground zero casualties). In order to make an apples-to-apples comparison, you really need to include the deaths of those in the buildings, those in the planes, the rescue workers with respiratory problems, and anyone…

Yes, I already regret jumping in on the math-game, when the real point I wanted to make was that this is an invalid comparison (apples/oranges) - sorry for that.

Plane crashes are created relatively equal in rate and magnitude.

Nuke crashes are nothing like that. We have only a single datapoint to draw from, and one that in hindsight almost seems like a relatively lucky one.

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

#112

Post by Travis » Wed, Mar 16, 2011, 4:03 PM UTC

moe wrote: post #111

Travis wrote: post #107

Earlier quoted context omitted.

I looked at your first source, and immediately noticed that the 2001 death toll does not count those who died in the WTC collapse (article states for 2001, 200 accidents, 1534 dead, so it doesn't include ground zero casualties). In order to make an apples-to-apples comparison, you really need to include the deaths of those in the buildings, those in the planes, the rescue workers with respiratory problems, and anyone…

Yes, I already regret jumping in on the math-game, when the real point I wanted to make was that this is an invalid comparison (apples/oranges) - sorry for that. Plane crashes are created relatively equal in rate and magnitude. Nuke crashes are nothing like that. We have only a single datapoint to draw from, and one that in hindsight almost seems like a relatively lucky one.

No worries. I still think you are incorrect, based on this:

>Plane crashes are created relatively equal in rate and magnitude.

Not all of them are... 9/11 was a plane crash that wasn't like any other before it.

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

#113

Post by varjag » Wed, Mar 16, 2011, 4:14 PM UTC

dkersten wrote: post #90

varjag wrote: post #77

Earlier quoted context omitted.

> The fact still remains: nuclear energy is the safest and cleanest we have for now. Burning natural gas is both cleaner is safer, and it is a power source for much of Europe. I wonder why all nuclear advocates always bring in coal into the comparison.

I imagine this is why: http://upload.wikimedia.org/wikipedia/en/8/83/2008_US_electr...

And in China they indeed burn even more coal. However, why build nuclear stations to displace coal, when it's possible to burn gas instead?

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

#114

Post by moe » Wed, Mar 16, 2011, 4:16 PM UTC

Travis wrote: post #112

moe wrote: post #111

Earlier quoted context omitted.

Yes, I already regret jumping in on the math-game, when the real point I wanted to make was that this is an invalid comparison (apples/oranges) - sorry for that. Plane crashes are created relatively equal in rate and magnitude. Nuke crashes are nothing like that. We have only a single datapoint to draw from, and one that in hindsight almost seems like a relatively lucky one.

No worries. I still think you are incorrect, based on this: >Plane crashes are created relatively equal in rate and magnitude. Not all of them are... 9/11 was a plane crash that wasn't like any other before it.

9/11 was a plane crash that wasn't like any other before it.

Yes, but think of the scales.

How many 9/11's does it take to match a worst-case scenario involving Tokyo (~35 million people)?

When I say "relatively equal" then I mean somewhere between 500 and perhaps a few thousand deaths from a plane crash. Whereas a nuke accident may range from 600k exposed to.. well, let's hope Fukushima gets its act together.

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

#115

Post by NickPollard » Wed, Mar 16, 2011, 4:52 PM UTC

moe wrote: post #110

NickPollard wrote: post #101

Earlier quoted context omitted.

Yes, I am serious. I said the plane falling happens more often, not that it is worse as a singular event. Unfortunately it is a problem with human psychology that we respond more strongly to a singular large event than to consistent low-level events. Some of the discussion on this page has suggested Chernobyl killed around 60k, directly and indirectly. Certainly a tragedy, and a huge one at that, but it is also the o…

Unfortunately it is a problem with human psychology that we respond more strongly to a singular large event than to consistent low-level events. I agree with that in general, although my opinion on this particular comparison differs. we're comparing approx 60k deaths, over the course of approximately 60 years Sorry to be nitpicking, but I'm not sure where the 60 years are coming from. However, since there's no hard d…

60 years is approximately how long we've had nuclear power for, I believe.

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

#116

Post by cperciva » Wed, Mar 16, 2011, 5:16 PM UTC

timr wrote: post #56

cperciva wrote: post #48

Earlier quoted context omitted.

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 i…

You're assuming an intact core.

No, I'm not.

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.

It is impossible for the uranium in a nuclear power plant to become critical in the absence of a moderator. Even if it's shaped into a sphere and supercooled. Add heat, and it gets further away from criticality (mostly due to doppler broadening; partly due to thermal expansion). Change the shape, and it gets further away from criticality (because there's more surface area to lose neutrons).

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

#117

Post by cperciva » Wed, Mar 16, 2011, 5:21 PM UTC

gjm11 wrote: post #99

wladimir wrote: post #54

Earlier quoted context omitted.

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.

> a last-ditch effort by nuclear energy lobbyists to convince us that nuclear energy is really safe. Well, let's see. In this case we've had a bunch of nuclear power stations very close to the site of a historically-large earthquake and the ensuing tsunami, large enough that even with Japan's outstanding disaster-preparedness thousands or tens of thousands of people have died. That would seem to be pretty much a wors…

And, so far, all the troubles at the nuclear reactors have produced a grand total of zero deaths.

Make that one death. One worker died as a result of the the crane he was working in becoming unbalanced and falling over.

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

#118

Post by cperciva » Wed, Mar 16, 2011, 5:24 PM UTC

retrogradeorbit wrote: post #64

He doesn't even get the units right, saying "231 micro sieverts" but specifying no time window. Per day? Per hour? Per minute? A decent physicist would _never_ make that error.

I've seen lots of nuclear physicists say "micro sieverts" when they mean "micro sieverts per hour". Apparently radiation levels are normally cited in hourly dosages, so people get lazy and don't say the "per hour" part...

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

#119

Post by timr » Wed, Mar 16, 2011, 5:53 PM UTC

yummyfajitas wrote: post #76

timr wrote: post #56

Earlier quoted context omitted.

"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 i…

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. Physics isn't biology/medicine. The laws of physics are not discovered by running experiments to enumerate every possible combination or permutation of configurations. You're assuming an intact core. Criticality is…

"Physics isn't biology/medicine. The laws of physics are not discovered by running experiments to enumerate every possible combination or permutation of configurations."

Wanna bet? Guess how we know most of what we know about criticality and neutron cross-sections? People like Louis Slotkin, who spent hundreds of hours poking at piles of radioactive material in the lab, to derive those mathematical models that you're leaning upon. Critical mass calculations, in particular, are so fiendishly complicated that the entire field of stochastic simulation (i.e. monte carlo methods) were invented to address them. So tell me again about the "laws of physics", and how they're not tested through pemutation.

"The optimal shape for criticality is a sphere....a wide, shallow puddle at the bottom of the containment chamber is the least dangerous shape."

Prove it. It's pretty amazing how everyone wants to cite "physics" to prove that there's no problem with a meltdown (in the face of overwhelming empirical evidence to the contrary), but nobody is doing much more than hand-waving allusions toward their undergrad physics textbook in defense of their assertions.

A sphere is definitely a shape where we have good calculations to model critical mass. Otherwise, we don't really know much that wasn't determined empirically. We know that criticality depends strongly on density. We've assumed that the structure of this reactor will prevent that density change from occurring. We don't actually know what will happen.

I can almost understand why a community of nerds is so strongly interested in maintaining the self-delusion that the world is a fully knowable, controllable place, but I don't understand how so many people can ignore so much real-world evidence for so long. If you're seriously telling yourself that a meltdown isn't a big deal, you need to go back and re-examine what you know about the situation, and why you think you know it.

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

#120

Post by Confusion » Wed, Mar 16, 2011, 6:01 PM 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.

Ai, I read it wrong. That was reactors 1-3 of the Daini station, not the Daiichi station.