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Wow, 20 years after Chernobly

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Originally posted by: BoomerD
Originally posted by: quentinterintino
Nuclear has such a bad stigma, mostly due to the ignorance of the public. I can't blame them, it is complicated, and it doesn't help when the press only points out the negatives, and provides blatant misinformation.

I can only recall 3 or so deaths associated from the entire nuclear complex here in the United States; but back in January 13 people died in West Virginia mining for coal, and nobody really batted an eye. Can you imagine if 13 people died as a result of a nuclear plant? Would it get the same press coverage, or would the entire industry be under scrutiny from FOX, CNN, etc?
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People have died mininu Uranium and other radioactive isotopes for over 50 yrs. Mining is a hazardous job, regardless if it's uranium, coal, or gold, but the underground mining tends to have more "disasterous" deaths, than strip or open pit mines, by the very nature of the mine...
Let's not compare apples and watermelons, and call it a fair comparison...Also, just for argument sake, when is the last time that a coal-fired power plant had a release of steam that had the potential to kill or cause birth defects of children up wind?
I'm NOT anti-nuke, but I DO believe that it needs to be done RIGHT to justify using it, because of the terrible consequences of accidents...Also, the spent fuel is nasty for THOUSANDS of years...If we're going to use nuk-u-ler power, then we need a way to deal with those wastes besides burying them in some out of the way place, and/or encasing them in concrete...that always seemed pretty short-sighted...
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Remember when I was talking about the un-informed public...:disgust:
 
Originally posted by: Heisenberg
Indeed. Chernobyl is an example of how to do everything wrong when designing a nuclear power plant.
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It's not really that bad of a design, as long as you dont have some tool running it.

doesn't need heavy water, can run on natural (or close to it) uranium, and can be used for Pu production..

pretty good from an economic standpoint. It had a few flaws, but had the engineers not disabled all the saftey features it wouldn't have been an issue.

not to mention that the remaning RBMK's have been made safer.. they run more enriched uranium now, with faster scram and whatever else they did.. forget now..

Here is some more photos of pripyat.
I have a buddy born there, he moved before the accident though. his dad works on a RBMK in lithuania now.
 
Originally posted by: CitizenDoug
Originally posted by: Sraaz
What exactly does "nuclear melt down" mean?
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I think it refers to what happens when safety amd cooling mechanisms fail and hot nuclear fuel is allowed to melt the reactor it is in.
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Its when the radiation around the wasted fuel starts to break down the core... making a Chernobly or almost Three Mile Island.
 
Come on guys, research a little a bit about nuclear energy before you actually post drivel.

A few websites to look at are:
Nuclear Energy Agency
International Atomic Energy Agency
Nuclear Regulatory Commission
Chernobyl

Not to forgot most of the national labs have websites.

Key topics to search for:
Afci (Advanced fuel cycle initiative, Gen IV reactors(molten salt, sodium cooled, VHTR, GFR), nuclear battery, transmutation and partitioning, sub-critical reactors (usually part of accelerator driven systems), double strata, Chernobyl........

What to do with the spent fuel has been researched since the 50's. Theoretically we know how to store, treat it and re use it. Applyig these methods is the problem. Politics is the biggest hurdle as people in charge are not technical. Our leaders care more about their short term political careers than how to plan for the future.

BTW, Three Mile Island was the best thing to happen to the nuclear industry in the US, considering no one was injured. Look up the exposure rate from the NRC's website if you want the exact numbers. It showed us that problems can occur and the safety implementations afterwards have probably saved many reactors from having major problems. Egggh...i need to get back to my paper.
 
been avoiding the slideshow.....it's powerfull

so sad 🙁

i think i would go insane living there, i could not handle all the pain that sorrounds them. also saw a special on abc news.
 
Originally posted by: Sraaz
What exactly does "nuclear melt down" mean?
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It means that the fuel for the reactor (e.g. uranium encased in metal rods) melts due to overheating.

In a nuclear reactor the heat is generated inside the fuel rods, which are immersed in a coolant (usually water). The rods then heat the coolant. It's the same principle in which the heating element in your kettle transfers heat to the water.

(The difference is that the reactor is much more powerful. A typical kettle holds 2 litres of water, and the heating element releases heat at a rate of about 2 kW - inside a nuclear reactor, in each 2 litres of water, the fuel rods will be releasing heat at about 200 kW).

If, for any reason, the rods fail to be completely covered with coolant - then they will overheat and melt. (If you turn on an empty kettle, the element will get red hot in a few seconds - imagine what might happen to the fuel rods producing heat 100x as quickly).

There is another catch - used fuel rods are intensely radioactive. Radioactive decay produces heat. So, even if the reactor is shut down - the fuel rods keep producing heat, and they need to be immersed in coolant. For the first hour after shut down, the rods produce decay heat at about 10% of full reactor power. (That's still 10x as powerful as your kettle).

When the reactor at 3 mile island melted down - it had already been shut down for several hours. However, due to a series of technical problems and human errors - cooling water was drained from the reactor uncovering some of the fuel rods. These promptly melted.

The big concern with melt down is that the molten fuel might flow into places where the reaction cannot be controlled. Within the reactor core, there is provision for 'control rods' to be inserted which prevent the nuclear reaction from taking place. However, if molten fuel collected at the bottom of the reactor, where control rods can't reach, an uncontrolled nuclear reaction could take place.

In the case of TMI, only part of the fuel melted - and the damaged fuel didn't collect in abnormal places sufficiently to cause an uncontrolled reaction.

In the case of Chernobyl - the reactor failed because of a massive power surge (the reactor temporarily spiked to 10,000% power - unsurprisingly, the cooling water in the reactor boiled rapidly and tore the reactor apart). The fuel that remained in the reactor promptly melted down and fell to the bottom of the reactor. For various reasons, a nuclear reaction couldn't continue on the floor of the reactor - but, decay heat kept the fuel molten and due to its continuous production of heat it slowly began to melt its way through the bottom of the reactor.

Underneath the chernobyl reactor were some water tanks. The concern was that if the molten fuel managed to reach the water - the water would act as a catalyst and allow an uncontrolled nuclear reaction to take place. While, this would probably not have been as dramatic as a nuclear weapon - the results could have been very serious indeed. In the end, volunteers were sent in to dive into the tanks and manually open drain plugs in the bottom to avoid this possiblity. The tanks were emptied, and later investigation found that the fuel had indeed melted through the reactor floor and had finally solidifed in a lump of slag on the bottom of the water tank.

 
They say that after the Chernobyl explosion, the reactor glowed a bright blue light. Does anyone know if pictures of this exist?

The tanks were emptied, and later investigation found that the fuel had indeed melted through the reactor floor and had finally solidifed in a lump of slag on the bottom of the water tank.

I believe those tanks were then pumped with cement to sure-up the foundation, to make sure radioactive material didn't sink into the ground/water table. All of those divers/miners dead shortly after.
 
Originally posted by: GTaudiophile
They say that after the Chernobyl explosion, the reactor glowed a bright blue light. Does anyone know if pictures of this exist?

The tanks were emptied, and later investigation found that the fuel had indeed melted through the reactor floor and had finally solidifed in a lump of slag on the bottom of the water tank.

I believe those tanks were then pumped with cement to sure-up the foundation, to make sure radioactive material didn't sink into the ground/water table. All of those divers/miners dead shortly after.
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The blue glow associated with nuclear reactors (and spent fuel pools) is Cherenkov radiation.

I recall watching a program, Nova I think, where they located where the slag had stopped in one of the basement levels.
 
Originally posted by: K1052

The blue glow associated with nuclear reactors (and spent fuel pools) is Cherenkov radiation.
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The blue glow in water is Cerenkov radiation. It is also seen (and used to quantify the activity of) in the storage ponds where spent nuclear fuel is kept.

However, typical nuclear reactions and radioactive decay don't have sufficient energy to generate Cerenkov radiation in air.

The blue glow seen above the Chernobyl reactor when it blew up was probably direct ionization of the air by the radiation (gamma rays, neutrons and alpha/beta particles). That these 2 different effects have a similar appearance is the cause of much confusion.

Only very high energy cosmic rays have sufficient energy to produce Cerenkov radiation in air.
 
As for the Water, wouldn't it evaporate at an alarming rate if it is used to cool such a hot element?

Don't they use high pressure on the water tanks to stop the water from going to vapor from liquid.
 
Originally posted by: Molondo
As for the Water, wouldn't it evaporate at an alarming rate if it is used to cool such a hot element?

Don't they use high pressure on the water tanks to stop the water from going to vapor from liquid.
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There are 2 main types of reactor design:

Boiling water reactors - cold water is pumped into the reactor core, where it is boiled by the heat. The steam that evaporates off is used to turn a turbine generator. The steam then goes to a condensor where it is cooled and turned back to water, and then pumped back into the reactor.

The reactor can evaporate about 400-500 gallons of water per second.

Pressurised water reactors - the reactor is kept at very high pressure which stops the water from boiling (about 22500 psi and 300 degrees C). Water is pumped through the core at about 5000 - 6000 gallons per sec. The hot water then flows through pipes in a heat exchanger. Low pressure water in the other circuit of the heat exchanger is heated by the hot pipes, the low pressure water boils and the steam goes to the turbines.

This design has the advantage that the steam and water in the main plant are seperate from the water in the reactor. This ensures all radioactivity is kept in the main reactor building. In the BWR design, the steam driving the turbines has come directly from the reactor (so is slightly radioactive) meaning that radiation protection measures (concrete shielding around pipes, staff monitoring and logs, etc.) must apply to the entire plant.

 
Originally posted by: HomerSapien
Come on guys, research a little a bit about nuclear energy before you actually post drivel.

A few websites to look at are:
Nuclear Energy Agency
International Atomic Energy Agency
Nuclear Regulatory Commission
Chernobyl

Not to forgot most of the national labs have websites.

Key topics to search for:
Afci (Advanced fuel cycle initiative, Gen IV reactors(molten salt, sodium cooled, VHTR, GFR), nuclear battery, transmutation and partitioning, sub-critical reactors (usually part of accelerator driven systems), double strata, Chernobyl........

What to do with the spent fuel has been researched since the 50's. Theoretically we know how to store, treat it and re use it. Applyig these methods is the problem. Politics is the biggest hurdle as people in charge are not technical. Our leaders care more about their short term political careers than how to plan for the future.

BTW, Three Mile Island was the best thing to happen to the nuclear industry in the US, considering no one was injured. Look up the exposure rate from the NRC's website if you want the exact numbers. It showed us that problems can occur and the safety implementations afterwards have probably saved many reactors from having major problems. Egggh...i need to get back to my paper.
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Wow, an intelligent post - thank you!
 
I used to work at a nuclear power plant in Pottstown, PA. I was just a computer guy, but it was very impressive walking around the plant. The power lines above you crackled from all the electricity.
 
Originally posted by: phantom309
Originally posted by: Jaskalas
Pandora?s Box will never be sealed, until we manage some magical process to get rid of radioactive material.

Then if we manage the intellect to outlaw the entire nuclear technology.
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Let's talk again when gas is $9/gallon and it costs $1200/mo to heat your house in the winter.
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Less than 3% of the nations electricity comes from oil, increasing or decreasing the amount of nuclear plants will have virtually no effect on the price of gas or heating oil. Most of our electricity comes from coal, which we have ridiculous amounts of.
 
I grew up a few miles from Calvert Cliffs nuclear plant, so at some point they held a pig assemby to talk about the emergency evacuation plan and what would possibly happen. According to that, nuclear reactors today are triple hulled, and in the case of an accident, it would take days for the radiation to get through all of the hulls.
 
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