Nuclear Physics?


Uh... yeah, so I just watched this "movie" on TNT with the rest of you kids, and well, I don't think it makes any sense. A.) The acting isn't and B.) The science is equally not. Why would exposing those rods cause an explosion? Why would anybody hire those actors? Why would any of us post about this movie? So many questions.

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I've read that spent rods generate a lot of heat, and need to be kept in the cooling pools for a few years. But I've never read anything that syas they'd explode. but let's not forget the baby sitter's cleavage

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If any technical person was consulted for this movie, there is a very high probability that individual was sipping bongwater. Any event in the movie should be viewed with due skepticism.

That said...exposed fuel rods can, hypothetically, reach a temperature at which the metals in the cladding chemically reduce water with the resulting production of hydrogen gas. Hydrogen can form explosive mixtures in air. The threat of burning hydrogen was real in the Three Mile Island incident back in '79. In that situation though, the fuel was uncovered in the core itself and was producing vastly more decay heat than would be found from spent fuel removed for storage.

I have not seen this movie and so cannot make specific comments, but it sounds like a great comedy as the first reviewer wrote...to be enjoyed with as high a blood alcohol concentration as possible.

-Carl

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the only way it could explode is if the coolant couldnt get to it, cause a rise in temp. and then so much pressure would cause a small explosion in the core, in which high levels of gamma radiation would be spread out a few k/m in radius and also make a nuclaer death cloud, its like chernobyl

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I studied Nuclear Chemistry for a while...

In the movie, I dont think that they were worried about an explosion. A Nuclear reactor rod cannot explode like a bomb, but it can melt...hence the terms 'meltdown' i presume. Also, after these spent fuel rods are no longer practical to use (ie concentrations of fission products and heavy elemets have increased to large amounts)the rods are removed. They emit Dangerous levels of Heat and Radiation...which is not good, so they put the rods in storage ponds to cool anywhere from several months to several years..depending on the reactivity and heat of the rods. Obviously if it takes years to cool something down...do you think it MAY be a little warm?? Thus...if our water can boil at 100 degrees...and heavy water which they use would probably have a greater boiling point...but not by far...I beleve it is possible to flash boil gallons of water in seconds. It's not completely inaccurate...

Regardless...I somewhat enjoyed the movie...even though it failed to be completely accurate in all degrees of measure.

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Ok, I think there has been some confusion on this part of the movie, partially because they didn't explain what was happening well enough (IMO). At the end of the movie, the rods that are in danger of being exposed are spent fuel rods. They are in a storage pool, and are not part of the active core. The actual reactor core for a plant is encolsed in a pressure vessel that is made out of steel that is more than six inches thick.

Once fuel rods are done with their time in the reactor, they are removed. Because of nuclear reactions that occur in the neutron-rich environment of the reactor core, certain isotopes are created within the fuel. Some of these are highly radioactive, so this spent fuel presents a health hazard (it is worth pointing out that fuel on its way into the reactor for the first time is safe to handle by hand). In addition to a radiation hazard, there is a thermodynamic hazard presented by these spent fuel rods because the chemical and nuclear reactons that occur in them will continue to give off signifficant amounts of heat even after they are removed from the reactor.

To solve both of these problems, the fuel is placed in a pool of water (the lack of a central repository for spent fuel means that every reactor in the US keeps its spent fuel on site). The water is a good shield against the radiation emitted by the fuel, and it also serves as a coolant for the rods. The water has enough thermal mass that it can withstand the heating as long as the water is cooled by means of a heat exchanger with a cold water source (a river or lake, for example).

If this water were to somehow be removed from the pool, the fuel elements would heat up above acceptable levels. Air would not be adequate to remove the heat, so the fuel would melt. It is hypothesized that the fuel might heat up enough for it to catch fire, and that would be very bad because it would spread radioactive material within the containment structure. At the same time, the loss of the water would mean the loss of the nuclear shielding, so there would be signifficant health risks to people in the room, especially if they are within the line of site of the rods. The firefighters in the movie all would have likely died if there was less than a foot of water covering the rods since it takes several feet of water to adequately absorb neutron radiation.

While there is potential for fire, there is no potential for an explosion. Steam can react with the Zircaloy cladding on the fuel rods to generate Hydrogen, but the Hydrogen would never reach concentrations high enough for an explosion. Since the spent fuel pools are open pools, and Hydrogen generated would be released into the containment (because Hydrogen is lighter than air). The sheer volume of the containment along with systems designed to detect and deal with Hydrogen would prevent the concentration from getting high enough for an explosion. Accidents inside of the reactor vessel can create a possibility of explosion, but that is because of the highher temperatures involved in an active core versus spent fuel and because the hydrogen can become trapped inside the vessel itself, and there it could potentially reach concentrations adequate for an explosion.

It is worth addressing the Chernobyl accident briefly since the question pertains to explosions. The Chernobyl accident involved a steam explosion, not a combustion or nuclear explosion. The fuel element-containing pressure tubes and the pressure vessel-like structure (it was not an actual sealed vessel) failed after great amounts of steam had been generated inside of them, and the resulting pressure release was the explosion that destroyed the building. There may have been a Hydrogen explosion as well when the Hydrogen generated in the core reached the atmoshphere, but that is unclear and it would only have been a secondary explosion if it did happen. The fire at Chernobyl was the result of the graphite moderator used in the core. When it was released to the air at such a high temperature, it caught fire. The graphite fires spread by the steam explosion were the cause of the massive release of radioactive materials from the plant. The threat of graphite fires is one of the primary reasons that graphite is not used as a moderator in American plants.(something the United states decided long before graphite proved how devastating it could be at Chernobyl).

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I'm watching this comedy at the moment. I have several thoughts:

1. I imagine that the designers of this nuclear power station have also built several along the San Andreas fault, and in all the areas where there are dangers from hurricans, as well as tornadoes. Are there really people that stupid working in the US? (alright, I suppose Democrats will answer that there are such people in the White House at the moment).

2. The builders should be sued because of the poor quality of materials used and the poor workmanship.

3. This plant much be extremely automated, as there seem to be only hald a dozen people on site.

4. The problem with graphite as a moderator mentioned by pvt1863 was discovered in 1957 at the British reactor at Windscale, part of the British bomb production project. Details can be found at http://en.wikipedia.org/wiki/Windscale_fire. Local farmers were not allowed to sell their milk and had to poor it away and were compensated by the Government. Milk production rose . . .

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"The threat of graphite fires is one of the primary reasons that graphite is not used as a moderator in American plants."

I disagree. I don't think the risk of fire is the main hinderance to using graphite as a moderator.

Firstly graphite doesn't burn easilly. I even have some sources doubting that it was a *graphite* fire at Chernobyl, but instead there may have been something else burning, such as debris. However that suspicion is not well corroborated at the moment so I'll stick with the official explanation "graphite fire" for the time and assume a graphite core can burn.

Secondly, which is much more important: graphite is the main reason there was a power excursion, which in turn led to the steam explosion that wrecked the reactor and the building. A graphite moderated reactor, cooled by light water and using natural unenriched uranium for fuel, has a very high positive void coefficient. That is to say that when the reactor starts to go out of control, this factor will drive the reactor into a death spiral and just exasberate the deviation until the structural integrity of the reactor fails catastrophically... i.e. it blows up in a steam explosion.

After that, a graphite fire is "just" icing on the cake.

/J

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I'm sure there are quite a few factual errors with this movie, but it wasn't ever intended to be a documentary on the way nuclear power plants work

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I notice they mostly build them by the sea or a river in case this happens.
But the Fukushima one got to much water and this did happen.



www.youtube.com/eastangliauk

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This a comedy, right? It's just unbelievable that they actually spent money in this crap. I think the problem isn't only the actors, the true horror lies within the script. And the answer to why are we still talking about this 3 years old movie, is because we find it so amusing and they're still re-running this show all over the world. That's why.

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I think that it's interesting that they went with the 'spent fuel rod pond' angle, as post-Fukushima we now know that this can actually cause an explosion.

But mainly, it seams to me, that if you want to make a disaster movie about a nuclear power station being damaged by tornados, then the FIRST thing you should do is find out how nuclear power stations, and twisters behave.

Now, the acting wasn't all that hot, but how much of that was down to bad writing, or bad editing/pacing? There were times that just left me thinking "Get on with it!", and only a couple of periods of genuine tension.

On the whole I'd say that this is a disaster movie in every sense of the word.
If you want a better tornado movie, watch 'Twister' (1996).
If you want a better nuclear plant movie, watch 'The China Syndrome' (1979), or 'Red Alert' (1977) which I prefer, although almost everyone else seems to hate it.
And finally, for a genuinely funny disaster movie comedy, you can't go wrong with 'Airplane!' (1980).

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