Question

Name the process by which nuclear energy is generated. state two examples of elements which are used for nuclear energy generation. list any two reasons which make large scale use of nuclear energy prohibitive

Answer 1

Nuclear power is the use of nuclear reactionsthat release nuclear energy[5] to generate heat, which most frequently is then used in steam turbines to produce electricity in a nuclear power plant. The term includes nuclear fission, nuclear decay and nuclear fusion. While every form of nuclear energy has been found in nature, fission energy was frequently viewed as a complete product of human ingenuity, until the discovery of Natural nuclear fission reactors within the earth's geological record. Presently, the nuclear fission of elements in the actinide series of the periodic table produce the vast majority of nuclear energy in the direct service of humankind, with nuclear decay processes, primarily in the form of hot-springs/geothermal energy, and radioisotope thermoelectric generators, in niche uses making up the rest.

Fission-electricity is one of the leading low carbon power generation methods of producing electricity, and in terms of total life-cycle greenhouse gas emissions per unit of energy generated, has emission values lower than renewable energy when the latter is taken as a single energy source.[6][7] A 2014 analysis of the carbon footprint literature by the Intergovernmental Panel on Climate Change (IPCC) reported that the embodied total life-cycle emission intensity of fission electricity has a median value of 12 g CO2eq/kWh which is the lowest out of all commercial baseload energy sources.[8][9]This is contrasted with coal and fossil gas at 820 and 490 g CO2 eq/kWh.[8][9] From the beginning of fission-electric power stationcommercialization in the 1970s, nuclear power prevented the emission of about 64 billion tonnes of carbon dioxide equivalentthat would have otherwise resulted from the burning of fossil fuels in thermal power stations.[10]

There is a social debate about nuclear power.[11][12][13] Proponents, such as the World Nuclear Association and Environmentalists for Nuclear Energy, contend that nuclear power is a safe, sustainable energy source that reduces carbon emissions.[14]Opponents, such as Greenpeace International and NIRS, contend that nuclear power poses many threats to people and the environment.[15][16][17] Far-reaching fission power reactor accidents, or accidents that resulted in medium to long-lived fission product contamination of inhabited areas, have occurred in Generation I and II reactordesigns. These include the Chernobyl disasterin 1986, the Fukushima Daiichi nuclear disaster in 2011, and the more contained Three Mile Island accident in 1979.[18] There have also been some nuclear submarine accidents.[18][19][20] In terms of lives lost per unit of energy generated, analysis has determined that fission-electric reactors have caused fewer fatalities per unit of energy generated than the other major sources of energy generation. Energy production from coal, petroleum, natural gas and hydroelectricity has caused a greater number of fatalities per unit of energy generated due to air pollution and energy accidenteffects.[21][22][23][24][25][26]

As of 2017, the International Atomic Energy Agency states that 60 reactors, mostly of Generation III reactor design, are under construction around the world, with the majority in Asia.[27] Collaboration on research & developments towards greater passive nuclear safety, efficiency and recycling of spent fuel in future Generation IV reactorspresently includes Euratom and the co-operation of more than 10 permanent countries globally.[28]

Unlike other applications of fission energy, in commercial nuclear fission reactors, the system is designed and operated in an otherwise self-extinguishing state. The reactor specific physical phenomena, that is depended upon to continue the constant heat output, is the predictably delayed[29] and therefore comparatively easily controlled, transformations or movements of a vital class of fission product, or reaction ember, as they decay.[30][31] Operating in this delayed critical state,[32] with the dependence on the inherently delayed transformation or movement of fission products/embers to maintain the reaction from self-extinguishing, the process occurs slow enough to permit human feedback on the temperature control. In a similar manner to fire dampers varying the opening to control the movement of wood embers towards new fuel, control rods are comparatively varied up or down, as the nuclear fuel burns up over time.[33][34][35][36]