Nuclear Energy - I need to vent/rant

[Schneibster]

Oops.

 

[Schneibster]

LOL!!! Guess there was a problem with the site. Moderators please correct!

 

[luddite]

No matter what happens, if something goes wrong, the reaction stops. In the worst case, the entire bundle of fuel rods melts into a puddle of slag at the bottom of the containment, and the reaction stops. Nothing gets out of the containment.

How can we be so confident of the containment? My daughter, who is studying engineering, was shown examples at the beginning of her studies of a series of spectacular engineering failures which were not understood until they were studied after the fact. Building collapses, bridge failures, dams breaking. The twin towers were specifically designed to withstand a direct impact from an airplane.

In Ontario, it turned out after the fact that the Pickering nuclear power plant is built almost directly above the point where 2 previously unknown fault lines cross. It continues to operate on what is now recognized as the most geologically active point in the country. You couldn't have picked a shakier siting if you set out to choose one.

Then I want to add a point about human stupidity and carelessness. I read an article a few years ago that demonstrated that despite improvements in brakes, front panel design, mandatory seatbelts, child restraints, airbags and other clear safety improvements, automobile fatalities remain fairly constant. It appears that drivers come to rely on the safety mechanisms and simply take more risks. Buzzo's assertion that he would be extremely careful in an RBMK reactor, but would relax if he was in another nuclear plant is suggestive.

Routine leads to carelessness in any case. I know that in Bruce County in Ontario, there is a black market in the devices that measure radiation exposure for Bruce power workers. Apparently workers would rather not lose work days due to overexposure to radiation. Which leads me to two questions:

1. If the processes are so well understood and controlled, how do power workers routinely become exposed to radiation above the permitted levels?

2. Is this the sort of people we want monitoring our nuclear power plants?

I want to go back to sparks and point out that while he overstated the case in saying that no evidence whatsoever has been offered, I'd have to say that the evidence has been underwhelming.

In part this is because of the relative positions. By saying "It's perfectly safe" you set yourself up for a much more demanding proof than someone who says there might be safety concerns. Because to prove there are safety concerns you just have to identify one or two. To prove that it's perfectly safe, however, you have to demonstrate that at every stage of the process the risks are none or negligible, that the safety features are more than adequate. And I do not think this has been done.

There has been a lot of handwaving about how TMI and Chernobyl couldn't possibly happen again, but even this claim has been inadequately supported.

I've introduced two articles that spoke about potential dangers with western reactors and they've been completely ignored.

If we strip away the angry rhetoric, people like sparks are unconvinced because your evidence was not compelling enough. Perhaps sparks should ask more specific questions about what concerns he has. But the pro-nuclear supporters need to recognize that they have a massive challenge, too. And so far there have been too many angry assertions on both sides.

And I'm still trying to reconcile the fact that governments are designing architecture to contain civilian nuclear waste for as much as a million years (in the case of Finland) while people on this forum are asserting that it's harmless after a hundred. The DOE document cited in the National Geographic article I linked to is extensively quoted on the web. In references, the 400,000 number comes up repeatedly as the point of "peak radioactivity". I haven't been able to find the source document yet though.

We all have work to do.

 

[DRBUZZ0]

Well for one thing the amount of radiation that a worker is exposed to is very conservatively limited. I could see how a worker might not want to miss a day because they're pushing a few microrems for their monthly dose.

TMI could happen again. I think it's unlikely. The exact same senerio could not happen again, but could a partial meltdown occur: Unlikely but impossible to rule out. If it did, it would be another PR nightmare and would require the reactor be shut down and some clean up be done... that's about it.

Chernobyl, simply put, cannot happen in a light water pressurized reactor. That having been said there always need to be redundant and passive safety measures taken. For example:

The pressure vessel is designed to be 100% incapable of loosing containment in even the worst possible theoretical overpressure situation.

However, just incase you are wrong, a sump and internal containment system is added. This is gaurenteed to never fail in any forseable event.

But just incase you are wrong, you have ceramic fuel which is encased in zirconium alloy tubes. You are 100% sure that there is no senerio where this could cause the fuel to be despersed even if the reactor vessle and secondary containment fail.

Even despite this, you add a massively overbuilt containment dome.

Another key is "Fail to safe" design. In otherwords, a coolant system failure, a loss of pressure, a loss of control of the reactor and any other event will result in it being shut down. This is similar to "Passive safety"


I can give a parallel example: In deep ocean submersiples they are built to be lighter than water. They would float except for lead weights which are held on by electromagnets. There is no mechanical connection. If you need to surface, you can throw a switch to release them. There is no relay, no logic circuit. You directly cut the power. If the batteries fail, the weights drop. If the switch fails, it cuts power. If all else fails, the cord could be cut, because it runs through the pressure sphere.

Similarly, on the Apollo landers, it's almost impossible to envision the accent engine not firing. It used two propellant in separate tanks which mixed to ignite the engine. If all else failed, the astronauts could manually open the valves. Once mixed they would ignite. No doubt there at all.


To understand why a worker might be exposed to more than permitted you have to realize that this is governed by "Linear Non-Thershhold Theory" and this amounts to exposure limits being "As low as reasonably possible." In other words: A tiny amount of radiation puts you at a tiny risk of health effects. A small amount puts you at a small risk of health effects. A somewhat larger dose means a somewhat larger risk. As such the dose limitations for the power industry are small... smaller than the airline industry. It's possible some workers may have "fudged" their dose because of not wanting to be sent home. I'm not excusing that, but that's not really a safety issue as it is made out to be.


As far as hundreds or millions of years for waste: That depends entirely on the nature of the waste. Also it depends on what is considered "harmless." One recognized standard is the point at which material presents a health hazard roughly equivalent to that of natural minerals.

Plutonium and other high-energy alpha emitters with long halflives will dramatically increase the time that you need to contain something.

 

[Lonewulf]

The twin towers were specifically designed to withstand a direct impact from an airplane.

Not that particular kind of airplane, no. Specifically, not something that big and with that much fuel.

Bad analogy.

 

[DRBUZZ0]

Well I think common sense dictates that it's just really dangerous to mix nuclear reactors and aircraft. Having aircraft flying at a nuclear reactor is pretty dangerous. The only thing I could think of that would be worse would be putting a nuclear reactor in harms way as an obvious target for enemy states or organizations who might want to attack by air means or otherwise. Yep....

Oh wait...

I once had someone tell me that it was dangerous to have a reactor near a city and they mentioned how Con-Ed had proposed a reactor in Brooklyn NY in the 1950's, as an insane proposal.

I said that the thought of a reactor in New York City was something most wouldn't consider..... except during "Fleet Week" Too bad they didn't get any super carriers in last time they did Fleet Week. Oh well... maybe next year. But I think a lot of them have been kinda busy with Bush's little forign policy stuff..

 

[Ziggurat]

Not that particular kind of airplane, no.

Correct - the design didn't consider planes that large. It's also worth noting that while not designed for such an impact, they DID withstand the impact.

 

[Lonewulf]

I think that the engineers also weren't counting on a full fuel tank. I think they were concentrating mostly on the possibility of an airplane out of fuel (and thus, not able to truly control itself), as opposed to an intentional contact.

 

[Ziggurat]

1. If the processes are so well understood and controlled, how do power workers routinely become exposed to radiation above the permitted levels?

By handling activated material outside the reactor itself. Radiation directly from the reactor is not a significant contributor.

2. Is this the sort of people we want monitoring our nuclear power plants?

You've got the question backwards. Do we want permitted levels set low enough that people will exceed them before they're put at any significant risk? And the answer is yes, we want them set that low, and they are set that low.

And I'm still trying to reconcile the fact that governments are designing architecture to contain civilian nuclear waste for as much as a million years (in the case of Finland) while people on this forum are asserting that it's harmless after a hundred.

Welcome to the world of politics. Governments do things that don't need to be done all the time. For those politicians who are opposed to nuclear power, or don't want it stored in a particular location, inflating the requirements for storage time on waste is essentially a back-door way of trying to prevent those activities. And while they might get input from various scientists, in the end, it's the legislators, not some impartial scientific expert pannel, which actually sets the requirements. That is as it should be, but it's not without drawbacks, and this is one of them.

The DOE document cited in the National Geographic article I linked to is extensively quoted on the web. In references, the 400,000 number comes up repeatedly as the point of "peak radioactivity". I haven't been able to find the source document yet though.

I haven't either. I've seen the 400,000 number listed in connection to the DOE and Yucca, but usually just in terms of them having to do a projection for that far into the future. The National Geographic article is the only one I've seen which connects that number to a future peak in radioactivity. And that claim doesn't make any sense, so I think the reporter screwed up on something.

 

[Ziggurat]

I can give a parallel example: In deep ocean submersiples they are built to be lighter than water. They would float except for lead weights which are held on by electromagnets. There is no mechanical connection. If you need to surface, you can throw a switch to release them. There is no relay, no logic circuit. You directly cut the power. If the batteries fail, the weights drop. If the switch fails, it cuts power. If all else fails, the cord could be cut, because it runs through the pressure sphere.

Many reactors have essentially the same mechanism: a rod (or rods) held up by an electromagnet which will drop if power is cut, whether from some system failure or because of a decision to stop the reaction. Dropping the rod removes fuel from the core and drops an absorber in its place, shutting down the reaction. It's a passive safety system: nothing needs to be functioning in order for it to shut down the reaction, rather things need to continue to work in order for it to not shut down the reaction.

 

[luddite]

I think that the engineers also weren't counting on a full fuel tank. I think they were concentrating mostly on the possibility of an airplane out of fuel (and thus, not able to truly control itself), as opposed to an intentional contact.

This is really irrelevant to this forum. But I did see an interview with the chief architect who was simply devastated that the buildings fell. If I remember correctly, he did account for an airliner that size. He didn't calculate what the burning fuel would do, that's right. And that's the problem with engineering. You don't anticipate all the potential problems. But even if he had figured on the burning fuel, he wouldn't have come to the right conclusions. It took a long time for the structural engineers to figure out that the supports had bent with the heat and pulled the structure in on itself. Steel wasn't supposed to yield that way. In fact, months later they were still talking about what unexpected reaction had actually caused some of the steel to melt. Because jet fuel burns well below the point that steel melts, so it was hard to explain the molten steel.

 

[luddite]

I haven't either. I've seen the 400,000 number listed in connection to the DOE and Yucca, but usually just in terms of them having to do a projection for that far into the future. The National Geographic article is the only one I've seen which connects that number to a future peak in radioactivity. And that claim doesn't make any sense, so I think the reporter screwed up on something.

I've seen quite a few references to the 400,000 year peak dose. Like I said I haven't yet found the DOE source document. The best, most detailed information I've found is here:

http://www.osti.gov/bridge/servlets/purl/805733-vytCTn/webviewable/805733.PDF

There are graphs which clearly show the peak dose rising to 400,000 years and this explanation:

It is useful to know which radionuclides are the greatest contributors to the calculated dose. At early times (the first 60,000 to 90,000 years) the dose is dominated by the highly soluble, very mobile radionuclides, I4C, 99Tc,a nd Iz9I. After that, the dose is dominated by 237Np with increasing contributions by several other actinides at late times (231Pa2, 26Ra2, 27A2~42, 220 230Th, ‘“Pb).

Note that the document regards civilian waste.

 

[Ziggurat]

And that's the problem with engineering. You don't anticipate all the potential problems.

Well, sure. But the thing is, skyscrapers aren't designed to accomodate failure. The building was designed to not fall down when hit by a plane, but there was no design to account for how to contain damage in the event that the building did fall down. Which is why the collapse of the twin towers caused a number of surrounding buildings to also fall. And that's a fundamental difference in the design philosphy between something like a nuclear reactor and a skyscraper. The reactors are designed so that the containment vessel won't blow open, but they're ALSO designed (at least in the west) so that even if it does blow open, damage is contained.

In fact, months later they were still talking about what unexpected reaction had actually caused some of the steel to melt.

Melting has nothing to do with the failure mechanisms that led to collapse. Steel softens at significantly lower temperatures than it melts at, due to a phase transition. All you needed to get collapse was for enough key parts of the structure to hit that phase transition temperature. And actually, there aren't any credible reports of molten steel either.

Because jet fuel burns well below the point that steel melts, so it was hard to explain the molten steel.

This is based upon a fundamental misunderstanding. There is no specific temperature, or even temperature range, at which any fuel burns. There is a specific ignition temperature (meaning a minimum temperature you need to burn), there is a specific amount of heat given off by that combustion, and there are typical temperatures at which fuel burns under a given set of conditions. But change the conditions, and you will change the temperature that the flame produces. In particular, if you insulate the fire so that heat remains trapped, you can get far higher temperatures than can be achieved with an open flame. And you don't need jet fuel to melt steel. Burning carbon will do just fine, if you insulate the fire well enough. And there was plenty of available carbon for fires which were quite persistent even after collapse. So even if there were bits of steel which melted, there's no reason to think this had anything to do with burning jet fuel or the collapse itself.

 

[Ziggurat]

I've seen quite a few references to the 400,000 year peak dose.

This, then, is part of the missing puzzle. Peak dose is not the same as peak radiactivity. The radioactivity will continually decline. The dose rate rises because they're assuming that containment fails, and that various radioactive elements will then seep out. But what's relevant isn't really how far off that peak dose occurs, but what that peak dose is. And it's really not that large. It's on the order of our existing background radiation (~300 mrem/year).

 

[luddite]

I know. I'm resisting the urge to comment more because this is so irrelevant to nuclear power.

I'm referring not to the post immediately above, but the one about jet fuel.

 

[Hindmost]

Finally found something on the subsidy issue..

US Department of Energy figures show that over the 40 years to 1993 US expenditure on nuclear R&D totalled $60 billion, resulting in it supplying 20% of the electricity, whereas solar & geothermal received $22 billion and supplied only 3% of the power. More recent figures show the renewables total in the DOE R&D budget as $356 million in FY2000 and $375 million in FY2001, of which wind got $33 and $40 million respectively.

http://www.uic.com.au/nip71.htm

The subsidies are substantial for nuclear power...but it seems it has given more back for the investment.

http://en.wikipedia.org/wiki/Energy_Policy_Act_of_2005

The energy policy has now been revised and this wiki site seems to have a reasonable set of highlites.

glenn

 

[DRBUZZ0]

Finally found something on the subsidy issue..



http://www.uic.com.au/nip71.htm

The subsidies are substantial for nuclear power...but it seems it has given more back for the investment.

http://en.wikipedia.org/wiki/Energy_Policy_Act_of_2005

The energy policy has now been revised and this wiki site seems to have a reasonable set of highlites.

glenn

To be fair not all the subsidies are directly pertaining to nuclear energy. Some of it was to encourage development of mining and enrichment infrastruicture, which benifits nuclear energy but prior to the 60's was really oriented almost entirely toward military applications.

But in any case, the numbers, even not adjusted for such things are pretty compelling IMHO.

 

[Schneibster]

This, then, is part of the missing puzzle. Peak dose is not the same as peak radioactivity. The radioactivity will continually decline. The dose rate rises because they're assuming that containment fails, and that various radioactive elements will then seep out. But what's relevant isn't really how far off that peak dose occurs, but what that peak dose is. And it's really not that large. It's on the order of our existing background radiation (~300 mrem/year).

I agree, examining the paper it specifies how much radioactive material will move how far in how much time if containment fails, and differentiates between early radionuclides that are highly mobile (carbon-14, technetium-99, and iodine-129), and late, long half-life radionuclides that are much less mobile (neptunium-237, with lesser contributions from a number of actinides, protactinium-231, radium-226, thorium-229 and -230, actinium-227, plutonium-242, and lead-210). The later radionuclides' lesser mobility is due to them not being water-soluble; they are heavy metals, as opposed to carbon, technetium, and iodine in the early stages, all of which can be carried away by water. The earlier radionuclides also have shorter half-lives, whereas the later ones are longer-lived, and therefore less active. The chart on the right side on page 10 of 13 indicates an approximate maximum worst-case dosage of about 300 mrem/yr, and average background in the US is 360 mrem/yr, more than half of it caused by radon-226 released from decaying uranium naturally present in the soil.

The containment failure modes are low-temperature, caused by water, and high-temperature, caused by "igneous events," i.e., a volcano erupts on the exact site of the nuclear waste storage depot. The low-temperature scenario is far more likely, and even then is given a chance of well under 1 in 1,000,000 of occurring; given our knowledge of plate tectonics, the "igneous event" scenario is unlikely in the extreme, approximately equal to the chance of winning the lottery on successive draws.

 

[DRBUZZ0]

It is worth noting that there are similar natural events of similar likelihood which could produce radioactive exposure from entirely natural sources of equal or larger dose and toxicity.

For example (I will try to find the article) but radium-226 is a strong alpha emitter with a half-life in the thousands of years (long enough to be a long-term concern. Short enough to be highly radioactive) and which is capable of binding to organic materials or otherwise being taken up into an organism and causing damage.

It occurs naturally in uranium ore as a product of decay. In at least one example I read about some time ago there was evidence that unusual water activity caused this material and other highly radioactive uranium daughters to be leached from a large uranium ore deposit and concentrated in a local water table.

Obviously such events would be exceedingly rare. Geology doesn't usually work that fast and uranium ore is generally of high enough density that not a lot leaches out of it.

But such an (extremely) rare event could pose a hazard to local wildlife or humans. This is a very unlikely event but impossible to completely rule out. As such, most radioactive waste will not really pose a greater hazard or probability than other events like this..

It's just one more deposit of radioactive material on a planet that already has many.

 

[JEROME DA GNOME]

I will tell you why we are not currently building new nuclear reactors for powering our cities.

YELLOW BOOTIES

Way to go Jimmy!

A US navy trained nuclear scientist acting as president roaming about in yellow booties.