Nuke waste Essay Example For Students

Nuke waste Essay Radioactive wastes, must for the protection of mankind bestored or disposed in such a manner that isolation from thebiosphere is assured until they have decayed to innocuouslevels. If this is not done, the world could face severephysical problems to living species living on this planet. Some atoms can disintegrate spontaneously. As they do,they emit ionizing radiation. Atoms having this property arecalled radioactive. By far the greatest number of uses forradioactivity in Canada relate not to the fission, but tothe decay of radioactive materials radioisotopes. Theseare unstable atoms that emit energy for a period of timethat varies with the isotope. During this active period,while the atoms are decaying to a stable state theirenergies can be used according to the kind of energy theyemit. Since the mid 1900s radioactive wastes have beenstored in different manners, but since several years newways of disposing and storing these wastes have beendeveloped so they may no longer be harmful . A veryadvantageous way of storing radioactive wastes is by aprocess called vitrification. Vitrification is a semi-continuous process thatenables the following operations to be carried out with thesame equipment: evaporation of the waste solution mixed withthe 1) borosilicate: any of several salts derived from bothboric acid and silicic acid and found in certain mineralssuch as tourmaline. additives necesary for the production of borosilicate glass, calcination and elaboration of the glass. These operationsarecarried out in a metallic pot that is heated in an induction furnace. The vitrification of one load of wastes comprisesof the following stages. The first step is Feeding. Inthis step the vitrification receives a constant flow ofmixture of wastes and of additives until it is 80% full ofcalcine. The feeding rate and heating power are adjusted sothat an aqueous phase of several litres is permanentlymaintained at the surface of the pot. The second step is theCalcination and glass evaporation. In this step when thepot is practically full of calcine, the temperature isprogressively increased up to 1100 to 1500 C and then ismaintained for several hours so to allow the glass toelaborate. The third step is Glass casting. The glass iscast in a special container. The heating of the output ofthe vitrification pot causes the glass plug to melt, thusallowing the glass to flow i nto containers which are thentransferred into the storage. Although part of the waste istransformed into a solid product there is still treatment ofgaseous and liquid wastes. The gases that escape from thepot during feeding and calcination are collected and sent toruthenium filters, condensers and scrubbing columns. Theruthenium filters consist of a bed of 2) condensacate: product of condensation. glass pellets coated with ferrous oxide and maintained at a temperature of 500 C. In the treatment of liquid wastes, the condensates collected contain about 15% ruthenium. This is then concentrated in an evaporator where nitric acid isdestroyed by formaldehyde so as to maintain low acidity. Theconcentration is then neutralized and enters thevitrification pot. Once the vitrification process is finished, thecontainers are stored in a storage pit. This pit has beendesigned so that the number of containers that may be storedis equivalent to nine years of production. Powerfulventilators provide air circulation to cool down glass.The glass produced has the advantage of being stored assolid rather than liquid. The advantages of the solids arethat they have almost complete insolubility, chemicalinertias, absence of volatile products and good radiationresistance. The ruthenium that escapes is absorbed by afilter. The amount of ruthenium likely to be released intothe environment is minimal. Another method that is being used today to get rid ofradioactive waste is the placement and self processing radioactive wastes in deep underground cavities. This isthe disposing of toxic wastes by incorporating them intomolten silicate rock, with low permeability. By this method,liquid wastes are injected into a deep underground cavity withmineral treatment and allowed to self-boil. The resulting steam is processed at ground level and recycled in a closedsystem. When waste addition is terminated, the chimney isallowed to boil dry. The heat generated by the radioactivewastes then melts the s urrounding rock, thus dissolving thewastes. When waste and water addition stop, the cavitytemperature would rise to the melting point of the rock. Asthe molten rock mass increases in size, so does the surfacearea. This results in a higher rate of conductive heat lossto the surrounding rock. Concurrently the heat productionrate of radioactivity diminishes because of decay. When theheat loss rate exceeds that of input, the molten rock willbegin to cool and solidify. Finally the rock refreezes,trapping the radioactivity in an insoluble rock matrix deepunderground. The heat surrounding the radioactivity wouldprevent the intrusion of ground water. After all, the steamand vapour are no longer released. The outlet hole would besealed. To go a little deeper into this concept, thetreatment of the wastes before injection is very important. Technology In Agriculture, And Its Application To EssayDuring operation of mixed bed columns, cation and anionexchangers are mixed to ensure that the acis formed aftercontact with the H-form cation resins immediatelyneutralized by the OH-form anion resin. The monobed or mixedbed systems are normally more economical to process wastesolutions. Against background of growing concern over the exposureof the population or any portion of it to any level of radiation, however small, the methods which have beensuccessfully used in the past to dispose of radioactivewastes must be reexamined. There are two commonly usedmethods, the storage of highly active liquid wastes and thedisposal of low activity liquid wastes to a naturalenvironment: sea, river or ground. In the case of thestorage of highly active wastes, no absolute guarantee canever be given. This is because of a possible vesseldeterioration or catastrophe which would cause a release ofradioactivity. The only alternative to dilution a nd dispersion is that of concentration and storage. This isimplied for the low activity wastes disposed into theenvironment. The alternative may be to evaporate off thebulk of the waste to obtain a small concentrated volume. Theaim is to develop more efficient types of evaporators. Atthe same time the decontamination factors obtained inevaporation must be high to ensure that the activity of thecondensate is negligible, though there remains the problemof accidental dispersion. Much effort is current in manycountries on the establishment of the ultimate disposalmethods. These are defined to those who fix the fissionproduct activity in a non-leakable solid state, so that thegeneral dispersion can never occur. The most promisingoutlines in the near future are; the absorbtion ofmontmorillonite clay which is comprised of natural claysthat have a good capacity for chemical exchange of cationsand can store radioactive wastes, fused salt calcinationwhich will neutralize the wastes and high t emperatureprocessing. Even though man has made many breakthroughs inthe processing, storage and disintegration of radioactivewastes, there is still much work ahead to render the wastesabsolutely harmless.