Saturday, January 25, 2003

Let them eat cake

John Cole has moved his site here, and links to this on GM food and European governments' objections to it.

IMO what the Europeans are doing is revolting.

But we shouldn't forget that the problem with their position is not that GM organisms cannot cause problems under any circumstances. In principle at least they could. GM products do need testing before release.

Friday, January 24, 2003

The North Korean nuke plant

Here is a story about the North Korean nuclear power plant that has received all the attention.

Note that it is 5 MW. Five scuzzy megawatts. For contrast, consider a plant such as the never-completed Bellefonte unit in northwestern AL. It was to have provided 1300 MW per unit. It had 4 diesel generators for standby power of about 7.6 MW each.

Got that? One modern American nuke site has more than 4 times as much power onsite just for backup power. Yeah, it's for power alright.

The story also says it uses graphite, like Chernobyl. I'm not a reactor designer, but I'll note that graphite normally is used in reactors intended for more than just power generation.

I don't have any time right now, but I'll see if I can't dig up more later.

UPDATE: Per my comments, it's 5MW thermal. I had assumed that it was 5MW electrical out of the generator, so it's significantly smaller than I thought. (You don't swap heat for juice 1 for 1 - thermal is like beef on the hoof and electrical is the resulting steaks and hamburger).

Darwin, meet Frankenstein

Here scientists are studying evolution:
Talk about funny-looking birds: The duck had a quail's pointy beak and the quail a duck's flat bill.
But University of California scientists who switched birds' beaks through a little egg tinkering had more than avian oddity in mind: The experiment uncovered some of the key cellular players in bird evolution, and may even lead to better understanding of what causes facial birth defects such as cleft palate.
Isn't it amazing what they can do with this tinkering? In principle they could do it to human embryos too.

Of course I use the term "human" only to identify just one pathetic species among millions. Certainly no one would ever confer personhood to a fetus, so the scientists can do whatever they want, right? No slippery slopes here...

How bugs breathe

Right here.

Wednesday, January 22, 2003

The bubbles of Chernobyl

Jay Manifold cites the above here, noting that bubbles were implicated in the Chernobyl accident. As an engineer with a decade's worth of experience onsite at nuclear power plants during construction, startup and operation I must point out a big difference between Chernobyl and the BWRs and PWRs I mentioned above.

As Jay mentioned, the Chernobyl reactor had what we call a positive void coefficient. Here the voids are bubbles, and the idea was that the more bubbles there were, the more rapidly the reactivity, and thus the power, and thus the heat of the reactor would rise. Of course this would create even more voids. In fact this happened so rapidly that the Chernobyl unit 3 exploded from the violence of the sudden bubble generation.

In the US such a design could not be licensed for a commercial nuclear power plant precisely because of the above scenario. In fact, regulations insist on a negative void coefficient, such that the presence of bubbles suppresses the reaction. How do you do that?

The difference is fundamental in the design. A thermal nuclear reactor requires something called "moderation" - no moderation, no useful reaction. In a BWR or PWR (the reactors commonly found in the US, India, France, and Korea) most of this service is provided done by the liquid water in the reactor. In the stricken Chernobyl reactor, the water contributed to moderation, but most of the moderation was from graphite blocks in the reactor.

Notice I said liquid water. The bubbles of steam are water in the chemical sense, but in terms of moderation they behave very differently - steam moderates far less. So the presence of steam bubbles tends to calm the reactor down so to speak. But with the RBMK reactor design at Chernobyl, the influence of the steam bubbles was not sufficient.

I don't know the relevant figures for the RBMK design. But just to provide an example with numbers in it, suppose that the water provided 10% of the moderation, and production of a given amount of steam reduced that to 1%. Then turning the water to steam would drop the overall moderation figure to 91% of the original. If water provided 100% of the moderation, then the moderation would be 10% of the original. Again, this is not intended to represent that actual state of affairs, but just to show how there is a range of "tuning" at the design stage which can radically affect the reactor's behavior.

In licenseable US reactors this negative void coefficient behavior is built in. It is not possible for the operator to run the plant in such a way that this is not true. Thus such problems are prevented at the licensing stage in the US.

The short answer is that the Chernobyl reactors are fundamentally different in design from US plants such that they are subject to entirely new classes of problems, and the spectacular accident almost 17 years ago resulted from one of those problems. Thus its relevance to US plants is limited.

But they do get more paper cuts

Several have noted that contrary to race hustlers' claims, the front line US troops are not composed disproportionately of minorities. For blacks in particular, the trend is to non-combat jobs to develop marketable skills.

There certainly isn't anything wrong with that, and the military needs people in non-combat positions too. But then there's this:
This is also the reason that there are even fewer minorities in the higher ranks of the military. The military has traditionally relied on the servicemen with combat arms experience for top leadership positions.
It makes sense to me, but I'm sure it will become a cause celebre as soon as a focus group signs off on it.

Fearsome critter

Jackalopes are for wimps - check this out.

Then maybe a sitcom?

You've probably seen the website. Now check out the novel. And he's working on a screenplay too.

Monday, January 20, 2003

Better living through abortions

Medpundit links to this story of a girl having an abortion because her condom broke. There's no word about whether she's suing the condom manufacturer for the failure, but I think we already know the answer.

She says "Maybe my unborn child, maybe it would have the most horrible life ever. I don't want to take any chances." Heavens no, it might have grown up to receive the death penalty. Better to kill it for its own good, right?

Here's more on condom (un)reliability from Clayton Cramer.

Sunday, January 19, 2003

Bubbles 101

I woke up at the crack of dawn this morning when it was very quiet. I set some water to boiling and went into the other room. I knew I'd be able to hear it boil, but it seemed really loud.

That's no surprise to those of us who have worked at steam power plants. Steam is noisy stuff. Why?

When you hear a hiss, that's actually very high frequency sound, beyond shrill. OK, but why do we get that from the pot?

As you boil water, tiny bubbles form at the heated surface. Because of the slightly increased pressure at the bottom of the pan, the water must be heated a bit above the local atmospheric boiling point (212°F or 100°C is close enough for most of us).

Why do the bubbles form? That's not trivial - you might notice that below a certain size they don't seem to exist (likewise for drops of water - they'll only get so small by themselves). It's not your eyesight - smaller ones just don't exist long enough to see. As it happens, a number of small-scale forces such as surface tensionthat must be balanced to form a bubble, and they conspire to make it impossible to form stable bubbles below a certain size.

After formation, the bubbles try to rise through the bulk of the water. As they do the pressure against them decreases, making the bubble enlarge. But this increase in size increases the surface area. The increase in surface area increases the rate of heat loss from the bubble, and thus the rate of cooling of the vapor inside. Eventually the bubble becomes unsustainable and collapses, which generates noise and tremendous highly localized pressures.

A given bubble doesn't make much noise, but then there are thousands of them. The bubbles don't all go off at once, but they collapse at a very high frequency. This means that the corresponding noises are high frequency, which the ear perceives as a hiss.

Of course the bubble's heat is going to the bulk of the liquid above, and eventually the bulk is at about the boiling temperature. Then the bubbles can survive long enough to get to the surface and they get bigger as they rise. Now they're noisier when they pop at the surface, but the pops don't happen as often, so the character of the noise changes.

Why is it that when little bubbles collide they become a big bubble? Anytime you see something happening spontaneously it's because the final state has less energy or greater entropy than the initial state. This isn't the place to drag you through thermodynamics, but we can say that the bigger bubbles have less surface area relative to their volume than little ones do, and less surface area means less energy tied up in surface tension, so nature favors the bigger bubbles. The same logic applies to drops of water - they don't get smaller unless you force them to.

Had enough of bubbles yet? I haven't, and this is my blog, so you'll just have to suffer.

Bubbles 103

So far in this page-turning Bubbles series we've covered bubbles in pots and in piping systems. Now let's talk about bubbles in you.

Your circulatory system is like a very flexible piping system. So a lot of the stuff in Bubbles 102 applies to your body too.

For one, your heart is a positive displacement pump. Get a big enough bubble in there (an air embolism) and all of a sudden it can't pump your blood. Consequences are left as an exercise.

But given its druthers, the bubble will rise to a high spot. Hopefully that's your head, and that's not a good place for bubbles either. Here a bubble could block blood flow to portions of your brain, giving you a stroke which could leave you more than half a bubble off at best.

Fortunately it's not hard to keep air out of your bloodstream. Health professionals have to make sure that hypodermic and IV needles are bubble-free before sticking you, and IVs are fed by the most reliable force we know of - gravity. And while you're at it, you don't want any bubbles in your douche bag either - believe it or not, this can cause an air embolism. (Given that colons are designed to handle gases, and can accomplish the remarkable feat of venting from the bottom, I don't think enema bags are a problem. But I understand that alcohol can be absorbed through the colon. Do with that information what you will).

That doesn't mean that there isn't gas in your bloodstream. There is, but it's in solution in your blood. Under normal circumstances it will stay there harmlessly.

But here in St. Louis over a century ago they found some abnormal circumstances. Workers there were deep beneath the Mississippi River in caissons and they were dying painfully. Unfortunately the chief engineer James Eads had discovered "the bends", a painful and often fatal condition caused by nitrogen bubbles in the blood.

Alright, I'm through. But I couldn't end a discussion of bubbles without linking to this.

Bubbles 102

In Bubbles 101 I wrote about bubbles in a pot. Now let's see what happens if the liquid that contains bubbles is contained in a piping system.

First you need to know a little about piping systems. If their contents are moving, that's because the pressure is higher where the liquid is coming from than it is where it's going to. In your house, you might have about 40 PSIG of pressure at the faucet when it's closed, but at the end just past the aerator the pressure is 0 PSIG whether the faucet is open or not. The greater the pressure difference the greater the flow.

For a straight level pipe the pressure drops off more or less linearly with length. Throw in direction changes, rough joints, valves, pumps, or changes in elevation, direction, temperature, pipe material or the properties of the contents and things get a lot more complicated in a hurry - in particular, there can be rapid changes of pressure from point to point. But the bottom line is that the pressure drops in the direction the flow is going.

As the pressure drops, it's easier for bubbles to form. That's why your Coke went flat and you change your cake recipe in the mountains. Anyway, it's not a problem if you just have a straight run of pipe - the bubbles just get bigger as you go downstream.

But if you throw in something as simple as an elevation change, the bubble formation rate changes. The bubbles will want to rise, perhaps even opposing the direction of the flow and introducing more flow resistance. More flow resistance means less pressure, and thus more bubbles...

At one power plant I worked at (which has never been in operation), an essential raw cooling water pipe was making incredibly loud noises. The 24" pipe exited a heat exchanger to a high point, turned horizontal and passed through two butterfly valves (one of which was not fully open), and then made a 90° turn straight down to a big discharge header which flowed to the heat sink. I told my supervision and anyone who would listen that the pipe was cavitating.

What's cavitation? Well, when the flow of fluid in a pipe is disturbed, the pressures in it can become unstable. When that is true, bubbles can flow into a volume where the pressure is too much for them, so they collapse. In the body of the fluid that's no problem, but if it happens at a solid surface bounding the fluid the effect is like a tiny chisel, and the pressures reach very high levels. Given enough time, this will chisel away anything while vibrating and making noise at deafening levels. (Conceptually similar mechanical things happen if large drops of water form in the steam in a steam turbine - they impinge on the blades and cause noise, vibration and ultimately failure.)

Anyway, after much bitching a work order was executed to work on the valve that had been throttled (not fully open). It wouldn't seal any more - imagine that. When they took the valve out, the maintenance guys were astounded at how thin the pipe walls had become and how shiny the normally rusty carbon steel surface was. They wound up replacing some pipe and changing operations practices to escape this problem.

(So cavitation produces sound. It turns out that sound can produce cavitation too. Terrific - about now that probably sounds about as useful as an appendix transplant, but in fact that's how ultrasonic cleaners work.)

Given a chance, bubbles will wind up collecting in the high points of the system, making big bubbles. Thus any decently designed piping system will have vents at the high points so the system can be filled fully before operation and perhaps periodically during operation. Fail that and then you're subject to hammering, which is just cavitation writ large. But when such a big "bubble" breaks or changes directions, the force when the water hits the pipe can be great enough to rip pipe right off its hangers and even rupture it. Or just annoy you - it's that loud slamming sound you might hear when you shut off the water suddenly.

Big bubbles can also effectively cut off flow in a system if they're in a pipe. Such a bubble complicated the response to the Three Mile Island accident. They can also prevent positive displacement or metering pumps from working effectively or delivering at all, which can be a real problem at chemical or water treatment plants.

Bubbles are a really big deal with nuclear reactors, and not just because of the TMI event. Boiling water reactors (BWRs) (like Dresden, Quad Cities, Clinton and LaSalle County in IL, Hatch in GA, River Bend in LA, Perry in OH or Grand Gulf in MS) are designed to have a certain amount of bubbling in the reactor core in normal operation, but only so much (the presence of bubbles affects both the rate of heat removal from the core and the rate of power generation - more bubbles -> less power). The much more common pressurized water reactors (PWRs) (like Braidwood and Byron in IL, Callaway in MO, Wolf Creek in KS, Farley and Bellefonte in AL, Indian Point in NY, Sequoyah in TN, Davis-Besse in OH and TMI, Susquehanna, Peach Bottom and Beaver Valley in PA) are not to have noticeable bubbles in them under any circumstances, and when they do you've got a problem.

Stay tuned for the next exciting segment of Bubbles: The Series....

The real McCoy

Elijah McCoy was born in Colchester, Ontario, Canada in 1843 to George and Mildred McCoy. His parents had both been slaves in Kentucky before they had escaped to Canada riding the underground railroad before the Civil War. When McCoy was young his family returned to America and moved to Ypsilanti, Michigan where his father worked in the logging industry.

Early on Elijah was fascinated with all things mechanical. He attended grammar school until he was fifteen. With money that they had saved up, his parents sent him to Edinburgh, Scotland to serve an apprenticeship in mechanical engineering. When he returned he was a full fledged engineer but he couldn't find work.

With his engineering training in hand, the only job that he could get was as a fireman (the person who put wood in the furnace) for the Michigan Central Railroad. In addition, part of his job was to oil the moving parts when the train stopped. It didn't take him long to figure out that this was quite a dangerous job since moving trains would often run into trains that were stopped on the tracks for oiling. (Remember the trains didn't really have any way to communicate with each other until Granville T. Woods invented the induction telegraph system in 1887.) To make matters worse, the need to stop the train for oiling was expensive and very time consuming. He began to work on self-lubricating devices to solve this problem and in 1872 he received his first patent for a lubricator for steam engines. His device allowed machines to be oiled automatically while the train was moving.

In the beginning, his device was belittled because a black man had created it but this didn't last long. His invention worked so well that people insisted that the "real McCoy" be in their engines, not some other device designed to do the same thing.

The real Reed

This post by Dean Esmay reminded me of an experience I had doing contract work for Commonwealth Edison 10+ years ago.

In college I kept an eye on ComEd because they were based in Chicago, near where I wanted to locate after graduation. So I researched their recruiters whenever they came to the campus. And I noticed that they were always black.

This wasn't exactly a scientific sample, but it did defy probabilities. And by then I knew of the Bakke case and was disgusted that the issue had ever come up. Yeah, that's it - the way to achieve equality is through systematic discrimination, to gain "the just spoils of a righteous war". The cumulative effect of these and other random observations, independent of suggestions from anyone else and contrary to the way I had been conditioned, was to make me inherently suspicious of blacks in high positions.

Then I became aware of a black executive at ComEd named Cordell Reed. He was high in the engineering department over the nuclear power plants, and I was morbidly curious - was he what I was already thinking of as "an affirmative action special"?

So I asked around as discreetly as possible. Everyone I asked said that he was the genuine article. He was one of the first 3 engineering graduates from the University of Illinois. He was also a nuclear power pioneer - he had worked in the control room at Dresden, which at the time was first commercial nuclear power plant built entirely without federal money. I have no reason to believe that anyone was being PC - they really thought well of the man.

Mr. Reed did it the hard way, as recognized here and and at the National Academy of Engineering.

So, I offer the now-retired Mr. Reed my profound apologies and respect. It's the sorriest honor he'll ever get, but it's all I have.