nuclear wastes and highly radio active waste management.

Nuclear wastes and highly radioactive waste management 


The nuclear waste originates from uranium  mining, civilian nuclear power  plants, military nuclear weapon program, hospitals, educational  institutions and research centers. Recent controversy involve four categories of wastes.

1. High -level wastes : Highly  radio active wastes created through  the reprocessing of reactor fuels. These waste are generated by both civilian and military reactor program-mes. Currently  large quantities  of high level wastes are stored in temporary containment facilities in world.

2. Transuranic  wastes :  Some of the elements in these radioactive by products of reactor fuel and military waste processing remain dangerous for extraordinary long periods. Plutonium 239, with half life of 24000 years and americium -243 with a 7300 year half life are among the tranuranics. Other more exotic transuranic elements have life exceeding 2,00,000 years.

3. Spent nuclear fuel : large quantities  of spent fuel, mostly spent fuel mostly civilian reactors are stored temporarily at  reactor sites. By 2010 more nuclear plants become operational the spent fuel expected to increase considerably .

4. Low-level wastes : any material contaminated by radiation and emitting low-level of radio activity it self belongs in this  category, while this include workers clothes, tools , and equipment and other items associated with nuclear reactor or nuclear materials . Low level wastes currently stored at repositories around world.


High level radioactive waste management.

High level  radio active waste management concern management and disposal of highly radio active  materials created during production nuclear power and military warheads. The technical issue is accomplishing  this are daunting, due to the extremely long periods radio active waste remain deadly to living organisms. Of technical concern are two long lived fission products Technetium (half life 2,20,000 years) and  iodine -129 (half life 15.7 million years ) which dominate spent fuel nuclear radio activity  after a few thousand years . The most trouble some transuranic element in spent fuel  are Neptunium -237 (half life two million years and Plutonium -239 (half life 24,000 years ). Consequently  the high level radio active waste management requires sophisticated treatment and management to successfully isolate it from bio-sphere .This   usually necessitates  treatment followed by a long term management strategy involving permanent  storage disposal or  transformation  of waste into toxic form.

Government around the world are considering a range of waste   management and disposal options usually involving deep geologic placement ,although there has been limited progress toward implementing long term waste management solutions.

The problem Is how to keep radio active in storage until it decays after hundred  of thousand years. The  geologic deposit must be absolutely reliable as the quotes of poison  are tremendous . It is very difficult to satisfy there requirements for simple reason that we have had no practical experience with a such long term project.

Hannes  Alfven noble laureate in physics identified two fundamental prerequisites for effective management of high level radio active waste 1. Stable geological formalities 2. Stable human institutions over hundred thousand years. As Al-fen suggests no known   human civilization has ever endured so long and no geologic formation of  adequate size of for a permanent radio active waste repository has yet been discovered that has been stable for a so long period.

There is debate over what should constitute an acceptable scientific and engineering foundation for proceeding with radio active waste disposal strategies . There are those who agreed on the basis of complex geo-chemical simulation models, that relinquishing control over radio active materials to Geo -hydro-logic process at respiratory closure is a acceptable risk. They maintain that so  called “ natural analogues “  inhibit subterranean nature of such processes in a solid geologic  formation unnecessary . However  existing models  of these processes are empirically  under deliver. Due to  the subterranean  nature of such process in solid geologic formalities, the accuracy of computer simulations models has not been verified by empirical observation, certainly not over a  period of time equivalent to the lethal half lives of high level radio active waste. On the other hand some insist deep geologic repositories in stable geologic formations are necessary. National management plans of various countries display  a variety of approach to resolving this dispute.

Geologic disposal

The process of selecting appropriate permanent repositories for high level waste and spent fuel is now under  way in several countries with first expected to be commissioned after 2017. The basic concept is to locate large, stable geologic formation and use mining technology to excavate a tunnel boring machines to drill shaft 500-1000 meters below the surface where  rooms or vaults can be excavated  for disposal of high radio active waste. The goal is permanently isolate nuclear waste from human environment.   

Because of some radio active species have half lives longer  than  one million years, even very low container leakage and radionuclide migration rates must be taken into account. Moreover it may require more than one half life until some nuclear materials loose enough radioactivity to no longer be lethal to living organisms. A 1983 review on Swedish radio active waste disposal program by national academy  of sciences found that countries estimate of several hundred thousand years. Perhaps up to one million years-being necessary  for waste isolation fully justified.

In order to store high level radio active waste forms in long term geologic depositions, specific wastes forms need to be used which will allow radio active, to decay away while material retain their integrity for thousand years. The materials currently used can be  broken down into few classes. Glass waste form ,ceramic waste forms and nanostructure materials.

The glass form include borosilicate glasses and phosphate glasses. Borosilicate nuclear waste glasses are currently used on industrial scale to immobilize high level radio active in many countries which are currently producers of nuclear energy or have nuclear weaponry . The glass waste form have advantage of being able to accommodate to wide variety of waste-stream composites. They are easy to scale up industrial process  and they are stable against thermal, radio active chemical perturbations. These glasses function by
Building radio active element to non-radio active glass forming elements. Phosphate glasses while not being used industrially have much lower dissolution rates than borosilicate glass which make them a more favorable action. However no single phosphate material has the ability to accommodate all radio active products so phosphate storage requirement more reprocessing to separate the waste into district fractions. Both glasses have to be processed at a elevation temperatures making them unusable for some of more volatile radio toxic elements.

The ceramic wastes form offer higher waste loadings than glass option because ceramics have crystalline structure. Also mineral analogue of ceramic waste forms provide  evidence for long term durability. Due to this fact and fact that they can be processed at lower temperature ceramic are often considered the next generation of high level radio active waste forms. Ceramic waste forms offer great potential but a lot research remains to be done.

Nanostructured materials  seems to be  frontier beyond ceramic waste forms. These vary pose size to integrate radionuclide’s  instead of specific atom sits. This allows greater chemical flexibility. Also nanostructure materials have lower  temperature processing and  can be later altered to make durable forms.

Finland ,the U.S. and Sweden are most advanced in developing a deep repositories  for high level waste disposal . Countries vary disposing used fuel directly after reprocessing with France and Japan having an extensive commitment for reprocessing.

India is having eventual deposit in deep geological repositories  on crystalline rock in Kalpak am.     .