Nuclear Energy (1712 words) Essay Example For Students

Nuclear Energy (1712 words) Essay Nuclear EnergyRadioactive wastes, must for the protection of mankind be stored or disposed insuch a manner that isolation from the biosphere is assured until they havedecayed to innocuous levels. If this is not done, the world could face severephysical problems to living species living on this planet. Some atoms candisintegrate spontaneously. As they do, they emit ionizing radiation. Atomshaving this property are called radioactive. By far the greatest number of usesfor radioactivity in Canada relate not to the fission, but to the decay ofradioactive materials radioisotopes. These are unstable atoms that emit energyfor a period of time that varies with the isotope. During this active period,while the atoms are decaying to a stable state their energies can be usedaccording to the kind of energy they emit. Since the mid 1900s radioactivewastes have been stored in different manners, but since several years new waysof disposing and storing these wastes have been developed so they may no longerbe harmful. A very advantageous 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 the same equipment:evaporation of the waste solution mixed with the borosilicate: any of severalsalts derived from both boric acid and silicic acid and found in certainminerals such as tourmaline. additives necesary for the production ofborosilicate glass, calcination and elaboration of the glass. These operationsare carried out in a metallic pot that is heated in an induction furnace. Thevitrification of one load of wastes comprises of the following stages. The firststep is Feeding. In this step the vitrification receives a constant flow ofmixture of wastes and of additives until it is 80% full of calcine. The feedingrate and heating power are adjusted so that an aqueous phase of several litresis permanently maintained at the surface of the pot. The second step is the Calc inationand glass evaporation. In this step when the pot is practically full of calcine,the temperature is progressively increased up to 1100 to 1500 C and then ismaintained for several hours so to allow the glass to elaborate. The third stepis Glass casting. The glass is cast in a special container. The heating of theoutput of the vitrification pot causes the glass plug to melt, thus allowing theglass to flow into containers which are then transferred into the storage. Although part of the waste is transformed into a solid product there is stilltreatment of gaseous and liquid wastes. The gases that escape from the potduring feeding and calcination are collected and sent to ruthenium filters,condensers and scrubbing columns. The ruthenium filters consist of a bed ofcondensacate: product of condensation. glass pellets coated with ferrous oxideand maintained at a temperature of 500 C. In the treatment of liquid wastes, thecondensates collected contain about 15% ruthenium. This is then concentrated inan evaporator where nitric acid is destroyed by formaldehyde so as to maintainlow acidity. The concentration is then neutralized and enters the vitrificationpot. Once the vitrification process is finished, the containers are stored in astorage pit. This pit has been designed so that the number of containers thatmay be stored is equivalent to nine years of production. Powerful ventilatorsprovide air circulation to cool down glass. The glass produced has the advantageof being stored as solid rather than liquid. The advantages of the solids arethat they have almost complete insolubility, chemical inertias, absence ofvolatile products and good radiation resistance. The ruthenium that escapes isabsorbed by a filter. The amount of ruthenium likely to be released into theenvironment is minimal. Another method that is being used today to get rid ofradioactive waste is the placement and self processing radioactive wastes indeep underground cavities. This is the disposing of toxic wastes byincorporating them into molten silicate rock, with low permeability. By thismethod, liquid wastes are injected into a deep underground cavity with mineraltreatment and allowed to self-boil. The resulting steam is processed at groundlevel and recycled in a closed system. When waste addition is terminated, thechimney is allowed to boil dry. The heat generated by the radioactive wastesthen melts the surrounding rock, thus dissolving the wastes. When waste andwa ter addition stop, the cavity temperature would rise to the melting point ofthe rock. As the molten rock mass increases in size, so does the surface area. King Henry Viii EssayThis is implied for the low activity wastes disposed into the environment. Thealternative may be to evaporate off the bulk of the waste to obtain a smallconcentrated volume. The aim is to develop more efficient types of evaporators. At the same time the decontamination factors obtained in evaporation must behigh to ensure that the activity of the condensate is negligible, though thereremains the problem of accidental dispersion. Much effort is current in manycountries on the establishment of the ultimate disposal methods. These aredefined to those who fix the fission product activity in a non-leakable solidstate, so that the general dispersion can never occur. The most promisingoutlines in the near future are; the absorbtion of montmorillonite clay whichis comprised of natural clays that have a good capacity for chemical exchange ofcations and can store radioactive wastes, fused salt calcination which willneutralize the wastes and high temperature processing. Even though man hasmade many breakthroughs in the processing, storage and disintegration ofradioactive wastes, there is still much work ahead to render the wastesabsolutely harmless.