What happens in a nuclear disaster?

Answer 1

A nuclear disaster could take several forms. The most obvious would be a meltdown at a nuclear reactor plant. Though the plant could not explode, the results of such a disaster would very likely be the release of massive amounts of radiation and radioactive material into the environment. And it would take hundreds of years to decay to anything near "safe" levels. Cleaning it up is out of the question, as exemplified by the Chernobyl disaster. In the Ukraine event, the reactor actually caught fire and burned. Prypiat is a ghost town. In the case of Three Mile Island, the meltdown was contained within the reactor vessel and the containment building, but there were some large releases of steam that was heavily laced with the radioactive debris of spent fuel fission fragments. These radioactive materials, which would normally be contained inside fuel elements, were released into the primary coolant when a loss-of-coolant accident overcame the plant.

There is a move underway to transport spent nuclear fuel to the spent fuel storage facility in the Yucca Mountain Repository in Nevada. This will be done by rail, and rail cars are vulnerable to accident. Though the rail cars that carry spent fuel will be specially engineered for the task, they are not indestructable. They can survive the mechanical damage from a "head on crash" from a vehicle (a locomotive is run into the cars to test the design), if an accident results in a conflagration of sorts due to, say, nearby petroleum cars catching fire, then that casket in which the spent fuel is cooking will fail. That could easily result in the airborne distribution of a large quantity of highly radioactive material over a wide area. Like in a nuclear power plant disaster, cleanup would not be possible.

It is possible that some kind of terrorist attack could result in the release of a large quantity of highly radioactive material, but that is unlikely. Certainly power plant spent fuel is vulnerable to assault, but the "effectiveness" of such a venture is probably not "high enough" to warrant the investment of the resources it would take to make it happen. It is extremely difficult to hoist a bunch of spent fuel out of holding tanks and drag it out into the open and blow it up or incinerate it completely enough to disperse large amounts of the radioactive materials. (Certainly the "local mess" requires that all efforts be made to secure nuclear plant sites and provide for rapid response teams to any facility.)

Accidents involving nuclear weapons and nuclear materials in labs usually don't result in the release of large quantities of highly radioactive materials, though some deaths occur as a result of these events. Criticality accidents in laboratory situations have killeded people on several occasions. But so has overdosing (with radiation) in a number of medical cases where patients were given incorrect doses of radiation during physician supervised medical treatments.

Answer 2

Skimming: As the name suggests, skimming involves the removal of the oil spillage with the help of tools and equipment's from the surface of the water. The most important aspect to be noted that only lighter oils can be separated and removed from the water in this method of cleaning up oil spills. This is because the density of oil will tend to be lighter than the density of water.

Answer 3

There is no real way to clean up a nuclear disaster. The only thing that keeps it contained is a large amount of cement. The nuclear rods will continue to burn down into the earth until they reach the molten part. This is especially dangerous when nuclear power plants are built over large supplies of underground water flows.

Answer 4

depends if you live. In short you don't, however if somehow you manage to avoid the initial blast, nuclear fallout and the radiation sickness. You're going to want a very very deep bunker surrounded with a lot of concrete and lead. Your also going to want around 3000 years worth of food oxygen and water, so you might want bring some of the opposite sex along because its going to be a long wait before you can go outside again.

Answer 5

(This needs review and revision by someone with more than US nuclear plant knowledge, so that aspects of other designs, such as heavy water moderated designs, can be included in the answer. Thank you.)

A nuclear disaster involves the uncontrolled release of nuclear fuel and mixed fission byproducts into the environment. The standard event, or design basis accident (DBA), involves a loss of coolant accident (LOCA) which deprives the core of its cooling pathway. This usually occurs due to a loss of pressurization, a coolant line break causing the coolant (usually water) to flash to steam.

At that point, one of two things happens...

If the neutron flux in the core is moderated by the coolant, such as in most US reactor designs, including Three Mile Island, the core goes sub-critical, and the nuclear fission process stops.

If the neutron flux is not moderated by the coolant, such as in the graphite reactor design at Chernobyl, the core stays critical, and the fission process continues. (Unless, of course, the control rods are inserted, taking the core sub-critical, which did not occur with Chernobyl.)

The next step involves temperature. Without coolant, the core gets hotter, because, even if the fission process stops, there are mixed fission byproducts that generate heat by their decay chain alone. If fission continues, the rate of increase of temperature is even greater.

Additionally, the design of the core affects the reactivity response to temperature - the US design makes reactivity be inversely dependent on temperature - where the graphite design makes reactivity directly proportional to temperature.

If fission increases without bounds, then the reactivity changes character. At some point, reactivity becomes dependent only on thermal neutrons, a positive coefficient, and the negative effects of other things disappear. If this happens, the core becomes prompt critical, prompt meaning dependent on thermal neutrons alone. This leads to a runaway reaction.

In a bomb, we actually go super prompt critical, and the core quickly consumes itself and detonates. In a normal reactor, without the containing force keeping the core at constant volume, the core quickly becomes "larger", an effect known as prompt dispersal, and reactivity stops. Still, the effects are devastating, with fuel leaving the rods and intruding into the vessel, and primary (and secondary) containment. (In Chernobyl, there was more than just prompt criticality that caused the explosion, such as a steam explosion when they attempted to inject water, water when cold actually increasing reactivity.)

Even if the core goes sub-critical, decay heat from the mixed fission byproducts is a serious problem. The temperature of the core rises, and it overheats. The core could melt, causing the nuclear fuel to flow out. If the melted fuel collects into a critical mass, it could restart the fission process, and go even further out of control. The is the theoretical basis of the "China Syndrome", where the fuel melts through the containment, into the ground, so to speak all the way to China, but contaminating everything in its way. This is why we go to extremes, with multiple redundant and layered systems to prevent the core from overheating.

In the US design, the primary protection boundary is the fuel rod itself. The rod is designed to handle enormous temperature and pressure. Also, if it were to leak, the probability of non-gaseous release is small - most releases should be isotopes of noble gases such as krypton and xenon, and iodines. The primary and secondary containment then hold that volume as long as possible, giving the more dangerous isotopes time to decay. Additionally, charcoal and other filtration systems collect iodines and particulates, reducing their concentration in containment. By the time pressure in containment is high enough to require release, most short lived nuclides have decayed and the plant operator has time to pick an environmentally best time to make the release. In fact, this is what happened at Three Mile Island - most of the release was Krypton-85 - and the environmental impact was minimal.

Answer 6

Well, by the time it is classified as a "disaster" it is pretty much out of control.

Most disasters involving nuclear material consist of run-away reactions or leakage.

A leakage is as simple as cleaning it up as quickly as possible. But for a run-away reaction, it is much more complex.

In a full reaction, one would want to attempt to regain control of the reaction and slow it down. This must be done by encompassing the critical material with something that has the ability to absorb the neutrons that cause the nuclear material to fissile, without actually fissiling themselves. This is usually done with control rods and water (though, if we are having a run-away reaction, it is likely that these would not be functioning, rather than someone just wasn't paying attention to the monitor).

Control rods may have to be manually entered and water manually entered as well, but the water would also have to be cycled to prevent it from boiling over and causing a steam explosion. These actions would cause great risk to those who would go in to manually to stop the reaction.

In a nuclear disaster, people exposed would have varying degrees of radiation burns and/or radiation poisoning. Depending on how the disaster occurs and the type of exposure to people. Some could die instantly, in moments from organ failure, over an extended period of time from cancer or a devastated immune system, or possibly recover from their poising.

the largest "disaster" that happened in the US was TMI* (three mile island) in the late seventies. This resulted in no deaths and no confirmed cases of cancer or other effects. Chernobyl, in 1986, is widely regarded as the worst nuclear disaster in human history. The steam explosion scattered vast amounts of radioactive material into the air, where the wind carried it over the Ukraine. It is estimated that approximately 4,000 people suffered from cancer and immune deficiencies over the years after the effect, there was also a spike in birth defects in the following year. 57 people died in the initial disaster.

*TMI is often viewed as a success story in regards to its safety equipment. When engineers believed that the reactor was going to meltdown (get so hot that it melts through its container), they evacuated the power plant. The automatic safety system managed to safely bring the reaction back under control, although some radiation did escape.

Answer 7

A nuclear disaster is a phrase that describes any disaster to human resources affected by fallout or leakage from nuclear fission.

1. During WWII, the US tested nuclear energy and small bombs on animal and human test subjects in western states (Nevada and Arizona, I believe). Some uninhabited islands were also used for testing grounds. Animals died or suffered radiation effects and later died. I believe human subjects also suffered radiation poisoning and became ill. You didn't recover from radiation effects; you still would not recover today.
2. The US dropped a nuclear bomb on Japan just before the end of WWII. Millions instantly died or were suffered horrific nuclear burns--and later died. The photos of victims right after the blast---horrific images! Millions were exposed to nuclear fallout. Hiroshima was practically pulverized for miles around the drop zone. *This was the huge lesson for all nuclear world powers. Humans realized that no country would win a nuclear war if we shot off nuclear bombs or rockets. Nuclear radiation would kill both sides, making this weaponry less attractive. However, nuclear fission held promise to produce energy. Thus countries began building nuclear plants, despite protests from citizens. Current generations are seemingly unaware of the dangers lurking at nuclear plants-- plants are just accepted parts of the landscape now! But... they remain a huge threat to life. And--after several decades near and after WWII, the US now pleads for countries to reduce their nuclear arms. In the wrong hands, one person could effectively start WW3 -- or kill a large percentage of the world's population!
3. During an impending threat of core meltdown and disaster at Three Mile Island in Pennsylvania, authorities in the early 1970s feared an overheating core would bore through the basement of the containment area, as well as release radioactive matter into the air. This disaster was averted---barely--but the immediate threat lasted for many days! Millions of Pennsylvanians still recall the fear, and worrying about unknowns.
4. In the 2000s, an earthquake and resulting tsunami made cracks in the containment of an overseas nuclear reactor. Men, who stayed inside the reactor building to try to keep the reactor cooled, were injured or killed. Nearby villages were evacuated because both the soil and water were contaminated. No one is permitted to go to those acres now; it will be inhabitable for...a very long, long time. When scientists or reporters are allowed access into that area, they must wear a radioactive measuring monitor and their visits must be very brief. Longer exposure, even when wearing protective suits and breathing via mask, will cause injury or death. A huge worry that resulted from containment being breached during the natural disasters (earthquake and tsunami within hours of each other) is that radioactive waste, normally contained separate from the environment, leaked into the ocean waters. No one knows what will be the long term effects to marine life and humans.
   
5. We can only hope and pray that our countries never face a nuclear bomb or containment breach. One thing to keep in mind is, just like winds carry volcanic ash around the world, winds will also carry radiation after any nuclear disaster. In terms of potential danger, a blast could affect half of Europe; half the US and Canada; or totally annihilate any small country or island.

Answer 8

Nothing would happen as nuclear waste are completely protected against fire.