16. The Big Eagle open pit mines on the south
slope of Green Mountain near Jeffrey City,
Wyoming.
17.
18.
19.
20.
21.
22.
23.
24. “… it would be morally wrong to commit future
generations to the consequences of fission power
on a massive scale unless it has been
demonstrated beyond reasonable doubt that at
least one method exists for the safe isolation of
these wastes for the indefinite future.”
-Flowers Report
Speech 2
In my first presentation I spoke mainly about Nuclear Power and Radioactive Waste- what it is and how it is classified. I want to quickly remind you of what was spoken about so that we’re not completely lost today.
Nuclear power is produced by controlled (non-explosive) nuclear reactions. Commercial and utility plants currently use nuclear fission reactions to heat water to produce steam, which is then used to generate electricity.
As of 2005, nuclear power provided 6.3% of the world's energy and 16% of the world's electricity.
Annual generation of nuclear power has been on a slight downward trend since 2007, decreasing 1.8% in 2009 with nuclear power meeting 13-14% of the world's electricity demand.
Nuclear waste is the material that nuclear fuel becomes after it is used in a reactor.
It looks exactly like the fuel that was loaded into the reactor -- assemblies of metal rods enclosing stacked-up ceramic pellets. But since nuclear reactions have occurred, the contents aren’t quite the same.
Spent nuclear fuel composition varies depending on what was put into the reactor, how long the reactor operated, and how long the waste has been sitting out of the reactor. Most of the Uranium is still in the fuel when it leaves the reactor, even though its enrichment falls significantly.
Radioactive waste is classified into three categories: High level waste, intermediate level waste, and low level waste.
High-level Waste is the actual spent fuel, or the residual waste from reprocessing spent fuel. The U.S. does not reprocess its spent fuel. Therefore, all the highly radioactive isotopes remain within it, and the whole fuel assemblies are treated as high level waste. While only 3% of the volume of all radioactive waste, it holds 95% of the radioactivity. It generates a considerable amount of heat and requires cooling, as well as special shielding during handling and transport.
Intermediate-level waste contains lower amounts of radioactivity and may require special shielding. It typically comprises resins, chemical sludges and reactor components, as well as contaminated materials from reactor decommissioning. Worldwide it makes up 7% of the volume and has 4% of the radioactivity of all radioactive waste. It may be solidified in concrete or bitumen for disposal. Generally short-lived waste (mainly from reactors) is buried, but long-lived waste (from reprocessing nuclear fuel) will be disposed of deep underground.
Low-level Nuclear Waste represents about 90% of all radioactive wastes. It includes ordinary items, such as cloth, bottles, plastic, wipes, etc. that come into contact with some radiation. is not dangerous to handle, but must be disposed of more carefully than normal garbage. Usually it is buried in shallow landfill sites. To reduce its volume, it is often compacted or incinerated (in a closed container) before disposal. Worldwide it comprises 90% of the volume but only 1% of the radioactivity of all radioactive waste.
Types of Waste
As we all know, one of the greatest problems with nuclear energy is the waste produced. The waste is generally radioactive, and thus toxic. There are also a few different kinds of waste, depending on how it was produced. Nuclear waste is produced in many different ways. There are wastes produced in the reactor core, wastes created as a result of radioactive contamination, and wastes produced as a bi-product of uranium mining, refining, and enrichment.
The vast majority (99%) of radiation in nuclear waste is given off from spent fuel rods. However, fuel rods make up a relatively small percentage of the volume of waste. The largest volume of nuclear waste is composed of the leftovers from the mining process. This waste, however, doesn't give off much radiation.
So here are some types of nuclear waste…
Fission bi-products, which I discussed in detail last time, are the materials that result from the actual fission of heavy element atoms. Each time a uranium or plutonium atom splits it results in two new atoms. There are hundreds of other fission products, many of which are radioactive. Their half-lives, however, vary greatly from less than a second to many, many years.
The fission products, or fragments, usually remain within the fuel rods of the reactor. When most of the 235U in a fuel rod is spent, the rod must be removed. The radioactive fragments are what make the spent rods toxic. The fission products can be long-lived or short-lived. Here we see that most of the fission products are short lived.
Another type of nuclear waste is Transuranic waste. Most of this waste originates from nuclear weapons production facilities for defense programs. "Transuranic" refers to atoms of man-made elements that are heavier (higher in atomic number) than uranium (92). The most prominent element in most TRU waste is plutonium. I found a little animation to show what happens…
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When 238U "captures" a neutron (neutron is result of fission- capturing it kind of stops the chain reaction from running away and making a nuclear bomb effect), it is added to the original uranium nucleus, producing the radioactive isotope of uranium 239. This isotope has a half-life of 23.45 months. It decays into Neptunium 239. 239Np is also radioactive and decays into 239Pu. 239Np has a short half-life of about 2 days. 239Pu is also radioactive, and has a half-life of approximately 24,000 years. That's a long time!! A lot of 238U is turned into 239Pu through this sequence of decays. 239Pu is called a transuranic element.>>>>>>>>>>>>>>>>>>>>>>>>>>
The transuranic neutron addition products usually remain in the fuel rods, where the original 238U from which they were produced was located. This adds to the rods' toxicity, and makes it harder for them to be disposed. In general, transuranic wastes are long-lived. However, this depends on the isotope produced. The biggest transuranic waste produced is 239Pu. This is an extremely toxic and extremely long-lived compound.
There are also wastes as a result of Uranium Mining and Enrichment. When uranium is mined, it has to be separated from rock. This produces pure uranium ore and "tailings", essentially leftover rock that has had the uranium stripped from it. This rock often still contains radioactive nuclides and is somewhat dangerous. The tailings are generally long-lived, but are considered to be low-level waste. That is, the concentration of radioactive nuclei in them is small, and thus they are not extremely radioactive.
Uranium ore is only about .7% 235U. It must be enriched to bring the percentage of 235U up to about 4%. The enrichment process takes natural uranium, which contains 0.7% U-235. One output stream is Low Enriched Uranium for power reactors with 4% U-235. The other (much larger) output is mostly U-238, and is called "depleted uranium" (DU), because it has been depleted of most of its U-235. DU is about half as radioactive as natural uranium but is otherwise the same. DU is a "waste" product of enrichment, which there is a lot of. This is because for every gram of enriched uranium fuel produced, there are about 4 grams of 238U waste. 238U is radioactive and has a half-life of 4.5 billion yrs. This means that it is long-lived, but not extremely dangerous. However, some of its "daughter products" are radioactive. Thus, wastes produced as a result of enrichment must be kept in storage. By the way, a "daughter product" is an isotope that results from a decay of another, "parent", isotope. For example, when 238U decays, it produces 234Thorium, which is very radioactive and has a half-life of about 24 days
And then the last type of nuclear waste is Contaminated Stuff. A major portion of nuclear waste is comprised of spent fuel rods. These contain the fission products and transuranic wastes I mentioned before. However, a lot of other waste is produced in the reactor besides the fuel rods. This occurs as a result of radioactive contamination.
A nuclear reactor is extremely hot. This means that the particles inside the reactor are very energetic and are flying around at incredible speeds. Occasionally, an atom that is in a fuel rod can get knocked out. These atoms that get knocked out can be many different types, ranging from fission products to uranium to transuranic elements. Most are radioactive. Atoms that escape the fuel rod careen all over the inside of the reactor core. Eventually these atoms can strike something solid.
This is a lot like a bullet hitting a wall. If the wall is small, it might pass through.
However, if the wall is big enough, the bullet will smash into the wall and "stick" there. It’s the same with a nuclear reactor. Occasionally an atom can smash into a structural component of the reactor, implanting itself into it. Because many of the nuclides (which is a fancy term for atomic nucleus) careening about the core of a fission reactor are radioactive, when they smash into a structure and "stick", they make that structure appear to be radioactive. This is because there are many radioactive nuclides embedded in it, which give off radiation. Thus, many of the structural components of a reactor become radioactive over time, as they absorb radioactive nuclei into themselves.
Also, many of the pipes and other components of a reactor become radioactive. These must be replaced eventually because over time the extreme radiation inside the reactor weakens them.
Trojan Nuclear Reactor Dome: Decommissioned 1992: This is the reactor dome that was decommissioned in late 1992 because of a steam generator tube leak.
The biggest problem, however, arises when a nuclear reactor is turned off for good, or "decommissioned". Disposal of the reactor core is a huge problem because it is extremely radioactive.
This is the same quote that I used in my last presentation- the reason I’m using it today is because it goes along great with this part of the presentation.
The major problem of nuclear waste is what to do with it. In fact, one of the biggest (and perhaps the single biggest) expenses of the nuclear power industry could eventually be the storage of nuclear waste. Currently there are several ways in which nuclear waste is stored. Most of these methods are temporary. In most cases a viable long-term solution for waste storage has yet to be found. This is because the time period for storage is so incredibly long.
So, a little bit about the temporary storage of fuel rods:
The spent fuel rods from a nuclear reactor are the most radioactive of all nuclear wastes. When all the radiation given off by nuclear waste is tallied, the fuel rods give off 99% of it, in spite of having relatively small volume. There is, as of now, no permanent storage site of spent fuel rods. Temporary storage is being used while a permanent site is searched for and prepared.
When the spent fuel rods are removed from the reactor core, they are extremely hot and must be cooled down. Most nuclear power plants have a temporary storage pool next to the reactor. The spent rods are placed in the pool, where they can cool down. The pool is not filled with ordinary water but with boric acid, which helps to absorb some of the radiation given off by the radioactive nuclei inside the spent rods. The spent fuel rods are supposed to stay in the pool for only about 6 months, but, because there is no permanent storage site, they often stay there for years.
Many power plants have had to enlarge their pools to make room for more rods. As pools fill, there are major problems. If the rods are placed too close together, the remaining nuclear fuel could go critical, starting a nuclear chain reaction. Thus, the rods must be monitored and it is very important that the pools do not become too crowded. Also, as an additional safety measure, neutron-absorbing materials similar to those used in control rods are placed amongst the fuel rods.
Permanent disposal of the spent fuel is becoming more important as the pools become more and more crowded.
Another method of temporary storage is now used because of the overcrowding of pools. This is called dry storage (as opposed to "wet" storage that I just mentioned). Basically, this entails taking the waste and putting it in reinforced casks or entombing it in concrete bunkers. This is after the waste has already spent about 5 years cooling in a pool. The casks are also usually located close to the reactor site.
So what about Permanent Fuel Storage and Disposal?
There are many ideas about what to do with nuclear waste. The low-level (not extremely radioactive) waste can often be buried near the surface of the earth. It is not very dangerous and usually will have lost most of its radioactivity in a couple hundred years. The high-level waste, comprised mostly of spent fuel rods, is harder to get rid of. There are still plans for its disposal, however. Some of these include burying the waste under the ocean floor, storing it underground, and shooting it into space.
The most promising option so far is burying the waste in the ground. This is called "deep geological disposal". Because a spent fuel rod contains material that takes thousands of years to become stable (and non-radioactive), it must be contained for a very long time. If it is not contained, it could come in contact with human population centers and wildlife, posing a great danger to them. Therefore, the waste must be sealed up tightly.
Also, if the waste is being stored underground, it must be stored in an area where there is little groundwater flowing through. If ground water does flow through a waste storage site, it could erode the containment canisters and carry waste away into the environment. Additionally, a disposal site must be found with little geological activity. We don't want to put a waste disposal site on top of a fault line, where 1000 years in the future an earthquake will occur, releasing the buried waste into the environment.
The waste will probably be encapsulated in large casks designed to withstand corrosion, impacts, radiation, and temperature extremes. Special casks will also have to be used to transfer fuel rods from their holding pools and dry storage areas next to the reactor to the permanent geological storage site.
In the US a permanent storage site was selected at Yucca Mountain, Nevada in the ‘90s. Yucca Mountain is in an extremely dry area of Nevada. This minimized the possibility of water seeping through the rock and corroding the casks. Additionally, if the casks did get corroded, there is not much water flow to carry the nuclear wastes away. The casks would be buried about 1500 feet underground, further preventing the waste from escaping. It is also far from the nearest population center in Las Vegas. While Yucca Mountain is near of a fault line, the fault is believed to be inactive. There are several volcanoes in the vicinity, but scientists believe that they have been dormant for almost a million years and think it unlikely that they will erupt in the next 10,000 years.
Naturally, the people in Nevada were opposed to the creation of a nuclear waste repository. They express the common reaction, NIMBY (Not In My Backyard!!). This is because that although most evidence indicates that Yucca Mountain is a suitable place for storage, no one can guarantee that waste will not leak. However, quite a bit of research was conducted around the Yucca site. Also, work on tunneling into the mountain was started. The Yucca Mountain Deep Geological Repository was projected to be ready by the year 2010.
As of 2007, the United States had accumulated more than 50,000 metric tons of spent nuclear fuel from nuclear reactors. Permanent storage underground in U.S. had been proposed at the Yucca Mountain nuclear waste repository, but that project has now been effectively cancelled - the permanent disposal of the U.S.'s high-level waste is an as-yet unresolved political problem.
Yucca Mountain's cancellation has led to renewed interest in spent fuel reprocessing.
Although not a new technology, reprocessing can be part of the solution to nuclear waste. When nuclear power was first developed, it was assumed that spent nuclear fuel would go through this process. Commercial reprocessing plants use the well-proven PUREX (plutonium uranium extraction) process. This involves dissolving the fuel elements in concentrated nitric acid. Solvent extraction steps then undertake chemical separation of uranium and plutonium. The Pu and U can be returned to the input side of the fuel cycle – the uranium to the conversion plant prior to re-enrichment and the plutonium straight to MOX fuel fabrication (MOX fuel is an alternative to low enriched uranium fuel used in the light water reactors that predominate nuclear power generation).
The advantages of this process are somewhat obvious: The volume of waste is lessened and more fuel is created for nuclear reactors. However, as with all things, politics can get in the way. In the US plutonium reprocessing was banned because the recovered 239Pu is weapons grade material. If, after reprocessing, the fuel is stolen, it could be used by anyone to construct a nuclear weapon.
Link
As of 1981, the ban against reprocessing in the US was lifted, but there are still no operating reprocessing plants in the US because of the heavy regulations and the anti-nuclear sentiment of the general public. There are a few countries that do reprocess, however. France, for instance, regularly reprocesses its spent fuel.
Now it’s weird because everywhere that I read about reprocessing it said that it’s a solution and so on. But when I was on the website of the Union of Concerned Scientists, their page for reprocessing says that the reprocessing of spent nuclear fuel would increase, not decrease, the total volume of nuclear waste. They say that reprocessing is not a sensible answer to the nuclear waste problem.
Anyway, I think it is important to mention a process called Transmutation. Transmutation is the transformation of one element into another. The goal of transmutation, in radioactive waste disposal, is to transform long half-life, highly radioactive elements, into shorter half-life, less-radioactive elements. There are two methods currently proposed for the transmutation of high level radioactive waste: fast nuclear reactors, and hybrid reactors.
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Fast nuclear reactors take the plutonium created by nuclear reactors as byproduct, or as fuel for nuclear weapons and "consume" it. This process leaves uranium and other less dangerous radioactive waste.
Hybrid nuclear reactors promise near complete transmutation of almost any high level radioactive waste. The general process is to produce a sub-critical nuclear reactor and bombard the reactor fuel with neutrons. The neutrons break apart the large radioactive elements, releasing energy. This energy is used to power the neutron source needed to start the fission reaction. There will be some high level radioactive waste produced (generally parts of the neutron source) but in comparison to the amount of radioactive waste consumed, this will be minimal. This high level waste would need to be place into long term storage.
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Also I think its important to tell you guys, since we do have the trip to Indian Point, that I came across an article online that says that Indian Point in 2008 dumped 500,000 gallons of the water from one of their spent fuel pools into the Hudson River. When I decided to research it a little more I found that a lot of angry people wrote a lot of hate articles regarding this “dump.” I also found a statement by Neil Sheehan of the NRC, the governmental Nuclear Regulatory Commission saying…
“As far as the liquid that was in the pool, the water that was in the pool, it involved about 459,000 gallons. What they did was filter that water through a series of 7 filters to make sure that there was no contamination that would have been above federal limits for release to the River. They also had sampled it before they even put it through the filters so they knew that they had water that had very low levels, very low concentrations of radioactivity. In any case, they ran it through this series of 7 filters, and then released it to the River.”
I don’t know whom to believe really, because there are extremists who blow everything way out of proportion and there are also governmental agencies that straight up lie to the people. But I think that if this dumped water was so radioactive that it would do us harm this story would have been much more widespread and measures would’ve been taken care of.
