What is nuclear waste, and what do they do to dispose it?
I have this assignment at school and i have to talk about nuclear power and nuclear waste and make an opinion on whether it’s worth it. Just wondering how much do any of you guys know about nuclear waste, and what is your opinion on nuclear power?
July 20th, 2010 at 3:34 am
I think people have to use proper disposing rules to dispose of it but seemingly people just dump it somewhere affecting wildlife.
July 20th, 2010 at 3:48 am
Radioactive wastes are waste types containing radioactive chemical elements that do not have a practical purpose. They are sometimes the products of nuclear processes, such as nuclear fission. However, industries not directly connected to the nuclear industry can produce large quantities of radioactive waste. It has been estimated, for instance, that the past 20 years the oil-producing endeavors of the United States have accumulated eight million tons of radioactive wastes.[1] The majority of radioactive waste is “low-level waste”, meaning it contains low levels of radioactivity per mass or volume. This type of waste often consists of used protective clothing, which is only slightly contaminated but still dangerous in case of radioactive contamination of a human body through ingestion, inhalation, absorption, or injection. In the United States alone, the Department of Energy states that there are “millions of gallons of radioactive waste” as well as “thousands of tons of spent nuclear fuel and material” and also “huge quantities of contaminated soil and water”.[2] Despite these copious quantities of waste, the DOE has a goal of cleaning all presently contaminated sites successfully by 2025.[2] The Fernald, Ohio site for example had “31 million pounds of uranium product”, “2.5 billion pounds of waste”, “2.75 million cubic yards of contaminated soil and debris”, and a “223 acre portion of the underlying Great Miami Aquifer had uranium levels above drinking standards”.[2] The United States currently has at least 108 sites it currently designates as areas that are contaminated and unusable, sometimes many thousands of acres[3][2] The DOE wishes to try and clean or mitigate many or all by 2025, however the task can be difficult and it acknowledges that some will never be completely remediated, and just in one of these 108 larger designations, Oak Ridge National Laboratory, there were for example at least “167 known contaminant release sites” in one of the three subdivisions of the 37,000-acre (150 km²) site.[2] Some of the U.S. sites were smaller in nature, however, and cleanup issues were simpler to address, and the DOE has successfully completed cleanup, or at least closure, of several sites.[2]
The issue of disposal methods for nuclear waste was one of the most pressing current problems the international nuclear industry faced when trying to establish a long term energy production plan, yet there was hope it could be safely solved. A recent research report on the Nuclear Industry perspective of the current state of scientific knowledege in predicting the extent that waste would find its way from the deep burial facility – back to soil and drinking water (such that it presents a direct threat to the health of human beings – as well as to other forms of life) is presented in a document from the IAEA (The International Atomic Energy Agency) – which was published in October 2007 This document states “The capacity to model all the effects involved in the dissolution of the waste form, in conditions similar to the disposal site, is the final goal of all the research undertaken by many research groups over many years. As we will see in this report, this kind of investigation is far from being finished” [1]. In the United States, the DOE acknowledges much progress in addressing the waste problems of the industry, and successful remediation of some contaminated sites, yet also major uncertainties and sometimes complications and setbacks in handling the issue properly, cost effectively, and in the projected time frame.[2] In other countries with lower ability or will to maintain environmental integrity the issue would be even more problematic.
Vitrification
Long-term storage of radioactive waste requires the stabilization of the waste into a form which will not react, nor degrade, for extended periods of time. One way to do this is through vitrification. Currently at Sellafield the high-level waste (PUREX first cycle raffinate) is mixed with sugar and then calcined. Calcination involves passing the waste through a heated, rotating tube. The purposes of calcination are to evaporate the water from the waste, and de-nitrate the fission products to assist the stability of the glass produced.
The ‘calcine’ generated is fed continuously into an induction heated furnace with fragmented glass[3]. The resulting glass is a new substance in which the waste products are bonded into the glass matrix when it solidifies. This product, as a molten fluid, is poured into stainless steel cylindrical containers (“cylinders”) in a batch process. When cooled, the fluid solidifies (“vitrifies”) into the glass. Such glass, after being formed, is very highly resistant to water. [4] According to the ITU, it will require about 1 million years for 10% of such glass to dissolve in water.
After filling a cylinder, a seal is welded onto the cylinder. The cylinder is then washed. After being inspected for external contamination, the steel cylinder is stored, usually in an underground repository. In this form, the waste products are expected to be immobilized for a very long period of time (many thousands of years).
The glass inside a cylinder is usually a black glossy substance. All this work (in the United Kingdom) is done using hot cell systems. The sugar is added to control the ruthenium chemistry and to stop the formation of the volatile RuO4 containing radio ruthenium. In the west, the glass is normally a borosilicate glass (similar to Pyrex), while in the former Soviet bloc it is normal to use a phosphate glass. The amount of fission products in the glass must be limited because some (palladium, the other Pt group metals, and tellurium) tend to form metallic phases which separate from the glass. In Germany a vitrification plant is in use; this is treating the waste from a small demonstration reprocessing plant which has since been closed down.
[edit] Ion exchange
It is common for medium active wastes in the nuclear industry to be treated with ion exchange or other means to concentrate the radioactivity into a small volume. The much less radioactive bulk (after treatment) is often then discharged. For instance, it is possible to use a ferric hydroxide floc to remove radioactive metals from aqueous mixtures [5]. After the radioisotopes are absorbed onto the ferric hydroxide, the resulting sludge can be placed in a metal drum before being mixed with cement to form a solid waste form.[12] In order to get better long-term performance (mechanical stability) from such forms, they may be made from a mixture of fly ash, or blast furnace slag, and portland cement, instead of normal concrete (made with portland cement, gravel and sand).
[edit] Synroc
The Australian Synroc (synthetic rock) is a more sophisticated way to immobilize such waste, and this process may eventually come into commercial use for civil wastes (it is currently being developed for U.S. military wastes). Synroc was invented by the late Prof Ted Ringwood (a geochemist) at the Australian National University.[13] The Synroc contains pyrochlore and cryptomelane type minerals. The original form of Synroc (Synroc C) was designed for the liquid high level waste (PUREX raffinate) from a light water reactor. The main minerals in this Synroc are hollandite (BaAl2Ti6O16), zirconolite (CaZrTi2O7) and perovskite (CaTiO3). The zirconolite and perovskite are hosts for the actinides. The strontium and barium will be fixed in the perovskite. The caesium will be fixed in the hollandite.
[edit] Long term management of waste
[edit] Storage
High-level radioactive waste is stored temporarily in spent fuel pools and in dry cask storage facilities. This allows the shorter-lived isotopes to decay before further handling.
In 1997, in the 20 countries which account for most of the world’s nuclear power generation, spent fuel storage capacity at the reactors was 148,000 tonnes, with 59% of this utilized. However, a number of nuclear power plants in countries that do not reprocess had nearly filled their spent fuel pools, and resorted to Away-from-reactor storage (AFRS). AFRS capacity in 1997 was 78,000 tonnes, with 44% utilized, and annual additions of about 12,000 tonnes. AFRS cannot be expanded forever, and the lead times for final disposal sites have proven to be unpredictable (see below).
In 1989 and 1992, France commissioned commercial plants to vitrify HLW left over from reprocessing oxide fuel, although there are adequate facilities elsewhere, notably in the United Kingdom and Belgium. The capacity of these western European plants is 2,500 canisters (1000 t) a year, and some have been operating for 18 years.
[edit] Geological disposal
The process of selecting appropriate deep final repositories for high level waste and spent fuel is now under way in several countries with the first expected to be commissioned some time after 2010. However, many people remain uncomfortable with the immediate stewardship cessation of this management system. In Switzerland, the Grimsel Test Site is an international research facility investigating the open questions in radioactive waste disposal ([6]). Sweden is well advanced with plans for direct disposal of spent fuel, since its Parliament decided that this is acceptably safe, using the KBS-3 technology. In Germany, there is a political discussion about the search for an Endlager (final repository) for radioactive waste, accompanied by loud protests especially in the Gorleben village in the Wendland area, which was seen ideal for the final repository until 1990 because of its location next to the border to the former German Democratic Republic. Gorleben is presently being used to store radioactive waste non-permanently, with a decision on final disposal to be made at some future time. The U.S. has
July 20th, 2010 at 4:26 am
Nuclear waste is the end result of nuclear fission. This is usually stored in specialized areas or underground although as of now I know of only a few sites that are meant to be opened (Yuka mountain). The other option is recycling but this does not reduce the quantity of waste. It simply increases the amount of nuclear fuel you can use. Despite it’s fallacies nuclear energy is a viable source of energy since there is so much of it. Also compared to all the other forms of energy it’s the most efficient (89 % I think). The only problem is the waste however this is a very delicate topic.
July 20th, 2010 at 5:17 am
On a related issue is that currently in the United States coal burning power plants are the majority makers of electricity. coal does have a radio active content that is either put into the air or put in large mounds to dispose of.
It is probably easier to control the waste product of nuclear waste than to disperse it to the winds like coal plants do.
The most dangerous element of nuclear energy production is the human element, most of the accidents that we are aware of were caused by short sited and really dumb people, from scientist to janitors!
On the whole there is no better alternative that nuclear power.
right now.
Good Luck on your assignment!
July 20th, 2010 at 5:33 am
Well i will try and keep it kinda simple here so everyone can understand. While it really seems very complex it really isn’t.
Nuclear waste can be generally classified a either “low level” radioactive waste or “high level” radioactive waste. Low level nuclear waste usually includes material used to handle the highly radioactive parts of nuclear reactors (i.e. cooling water pipes and radiation suits) and waste from medical procedures involving radioactive treatments or x-rays. Low level waste is comparatively easy to dispose of. The level of radioactivity and the half life of the radioactive isotopes in low level waste is relatively small. Storing the waste for a period of 10 to 50 years will allow most of the radioactive isotopes in low level waste to decay, at which point the waste can be disposed of as normal refuse.
High level radioactive waste is generally material from the core of the nuclear reactor or nuclear weapon. This waste includes uranium, plutonium, and other highly radioactive elements made during fission. Most of the radioactive isotopes in high level waste emit large amounts of radiation and have extremely long half-lives (some longer than 100,000 years) creating long time periods before the waste will settle to safe levels of radioactivity.
As for my opinion on nuclear power, well while i believe that there are other ways that we could be producing cleaner, more renewable energy, ( which i would be happy to get into if you or anyone is very interested ) I do believe that while there are some very serious issues with nuclear power; however i also believe that as long as it is treated with the respect and care that is warranted it is a sufficient temporary alternative.
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