redfred18t

iTrader: (1)

so is sarbanes oxley and you still see ceo's doing illegal ****.

Rennkafer

iTrader: (3)

And it's only a deterrent AFTER you've sent a few to jail... until then the attitude would be "oh they won't really do it".

mgeoffriau

iTrader: (7)

So start by prosecuting the mortgage ratings agency execs. It's not isolated to energy companies -- right now the government's scared of actually prosecuting any execs from corporations that are "too big to fail", regardless of how negligent or fraudulent their actions may have been.

jbresee

Joe Perez-
Just wanted to say thanks for your comments. You have a gift for explaining complex concepts in a way that even I can understand. Appreciate it!

sixshooter

iTrader: (12)

Progress Energy is currently building two nuclear reactors on the Gulf coast of Florida just 50 or so miles north of their existing nuclear reactors at Crystal River, FL. Yay!

Joe Perez

iTrader: (8)

(Source: http://en.wikipedia.org/wiki/Pebble_bed_reactor#China)


Thanks, Not sure which one you're referring to (I was tired as hell when I wrote the Chernobyl response, so it is massively abridged) but I'm certainly no expert, just a civilian engineer who is fascinated by nuclear power in general.

For those who aren't familiar with plant design, a few notes are probably in order.

First, here's an extremely simplified drawing of a typical nuke plant.



This particular image is of a PWR (Pressurized Water Reactor) which is one of two styles common in the US and the west in general. The other common style is the BWR (Boiling Water Reactor) which is very similar, except that the control rods go in from the bottom, and the pressure inside the reactor is low enough that the water is permitted to boil inside the core, and exit the top as steam.

So, at the far left is the core. This is a giant stainless steel pot in which the uranium fuel is housed. Water is constantly being pumped through this core, and then up into the steam generator (aka, the boiler), as shown by the red lines. This is the primary coolant loop. You'll also note the pressurizer at the top of the primary loop. This is basically a shock-absorber. In a PWR, this is the one and only place where they allow steam to collect, to dampen any pulsation in the system. And it's actually critical that some steam be kept inside here. If the pressure in the system gets too high and all the steam in the pressurizer collapses into liquid water, then you lose your shock absorber and also your ability to fine-tune pressure in the system. So operators are trained to never, ever let this happen.

(BWRs don't have a pressurizer, since they're full of steam anyway. They also typically don't have a boiler or a secondary loop; the steam coming out of the core goes directly to the turbine. So, on the plus side, they are somewhat simpler. On the minus side, the steam coming out of the core and hitting the turbine and condenser (which are outside of the containment building) is radioactive, so there are a lot more potential failure points in the system for a primary loop rupture, release of radioactivity, etc.


At TMI, when the valve on top of the pressurizer stuck open, it started to let down the pressure in the primary loop. All the steam flowed out the top, and the water below expanded. Since the operators didn't want the pressurizer to fill with water completely, they started draining water out of the primary system (thus making matters worse) but couldn't re-establish equilibrium because of the stuck valve.


Ok, that's the primary loop. Next, you have the secondary loop. This goes from the steam generator to the turbine, then the condenser, and then back to the steam generator. This is the loop that ruptured at TMI and set the whole process in motion. Without this loop, no heat was being taken away from the steam generator, and consequently, all the heat built up in the primary system.

What heat? Well, even with the control rods fully inserted and the reactor "shut down" there is still a massive amount of decay heat as the reactor core gradually cools down. You know how after you shut off the engine in a turbo car, the water inside the turbo starts to boil even through there's no more exhaust flow? Same deal. You gotta keep the system running until the reactor has totally cooled off, which takes hours or days.



Last is the tertiary loop, which runs from the condenser off to the right side of the picture. On most reactors, this is the loop which runs out to the huge cooling towers outside. Some reactor (those located near large bodies of water) simply draw in water from the lake / river / ocean and use it as the tertiary loop.



Ok, nuclear physics 101: When a uranium atom splits (fission) it releases, among other things, a couple of neutrons. If those neutrons hit other uranium atoms, then those atoms split and emit more neutrons. This process creates heat.

Ideally, for every atom that splits, the emitted neutrons cause exactly one other atom to also split. This is called a critical reaction. If each fission event causes less than one atom to split, then power goes down. If each fission event causes more than one atom to split, this is a supercritical reaction, and power goes up. (Atomic bombs are massively supercritical.)

There are a couple of factors that govern this reaction. The most obvious are the control rods. These rods are made from a material which absorbs neutrons. So if you want to lower power, you insert more rods, thus capturing atoms and preventing them from hitting other uranium atoms.

There's a second factor as well, one which is in fact far more critical. It may sound odd, but when a uranium atom first splits, the atoms which it ejects are traveling so fast that the chance of them striking another uranium atom and causing a fission is quite small. In order to achieve a stable reaction, you actually need to slow the atoms down. You do this by adding a "moderator" to the core- some substance which slows down neutrons without capturing them.


In a western-style reactor (PWR or BWR), plain ole' water is used as both the moderator and the coolant. This is actually a neat safety feature. Remember earlier where I talked about "negative void coefficients?" Well, since the same water that's cooling the reactor is also moderating it, if that water starts to disappear, then it can't slow down the neutrons. So, if the water goes down, the power level goes down. Essentially, this is what prevented TMI-2 from physically exploding, rather than simply melting down.


Now, in the Chernobyl reactor (the RBMK design which I referred to earlier), water was present in the core as a coolant, however the primary moderator was a massive matrix of graphite blocks. And due to an oddity of nuclear physics which I don't claim to understand, the water which is present acts more as a neutron absorber than a neutron moderator. So basically, you can take away all the coolant, and because the graphite is still there, not only will moderation continue to occur, but it will in fact increase, as the water is no longer capturing any neutrons.


And that's basically what happened. The operators were idiots, but the basic design of the Chernobyl reactor is what allowed it to go totally apeshit and blow up.


Some good reading, for those who are interested in a better explanation than mine:

Detailed narrative of the TMI-2 incident (A hell of a good read)

List of significant events including TMI, Chernobyl, Windscale, etc


Description of BWR reactors

Description of PWR reactor

Description of RBMK reactor (such as the one at Chernobyl.)

Narrative of Chernobyl incident

The Nuclear Tourist Lots of good info.




That's awesome. I had no idea they were moving forward on these units.

Cococarbine3

iTrader: (1)

The first TMI link was really awesome to read. Narrative Part 3 was suspenseful. I can't imagine being in the position of the one worker and finding radioactive contaminants in the primary water while getting a sample. "oh ****, oh ****, ****!"

In my opinion, development in fusion power really needs to be focused on rather than building a bunch more of fission power plants. One reason is that it has a higher energy yield. Although fission gives more energy per reaction (200 MeV, with 10MeV of it neutrinos), fusion gives more energy per unit mass. For reference fission gives you about 1 MeV/amu while D-T fusion provides 3.52 MeV/amu. It is also relatively safer. I guess the only problem is containing and harnessing the energy.

http://www.timesonline.co.uk/tol/new...cle7034945.ece



Granted, that^ is only for studying fusion for weapons development, not to be used for energy production.

NA6C-Guy

iTrader: (1)

Every time I think about nuclear power and why we aren't using it more widely, I get so damn angry. Especially with new methods vastly reducing waste, it's a no brainer. People need to get it out of their heads that nuclear power = mushroom cloud or Chernobyl. I was just looking at the Wiki page for Birmingham out of boredom and noticed a fact I didn't know about my area. There are 3 nuclear plants in Alabama and Georgia (1 in AL, 2 in GA) and those 3 plants supply 20% of the two states total power demands. Do that with other means, as cleanly as nuclear does it.

JasonC SBB

SOX is USELESS. It was an expensive knee-jerk reaction to the Enron debacle, which is written by, and benefits, the accounting firms. And it would not have prevented Enron. The Enron/Andersen debacle had violated existing laws. Those laws could have been enforced.

Besides, it wasn't any in the army of gov't regulators that caught Enron. It was a private short-seller. He peered into their public financial reports, saw a rotting corpse, shorted the stock, and blew the whistle.

The problem (and conundrum) with regulations, is the phenomenon of "regulatory capture" - those who are to be regulated often have the money to influence said regulations.
http://en.wikipedia.org/wiki/Regulatory_capture
So they end up being favorable for larger companies and detrimental for smaller ones. This is one reason why corporations tend to get ever bigger. They can afford to buy influence. Big companies then simply pass the cost on to the consumers.

SOX is one example - it is disproportionately more expensive for smaller companies to follow its rules.

Criminal sanctions for violating more basic laws are thus more effective and far less costly for the consumers.