Category ENERGY

Теплогенерация на Украине

В 2016 году частные потребители тепла в Украине получают тепло из следующих источников:

1. Наиболее распространенный – от электричества, электрокотлы, электрокамины, электрообогреватели… Источником без подробностей в большинстве случаев является “энергия воды” – гидроэлектростанции… Возможно источник: атомная энергетика, ТЭЦ… Для большинства конечных потребителей источник – ЖКХ или компания “область_город_энерго”...

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Closing Remarks

The question for humanity, then, is not whether humans and our civilizations will

survive, but rather what kind of a planet we will inhabit.

Shellenberger and Nordhaus 2011

Science works. From initial empirical insights to theoretical explorations and finally to implemented designs we have managed to create a standard of living (for some) that was inconceivable a few decades ago. As John O’M. Bockis states in the fore­word to the book Future Energy, “we have grown fat and happy on carbon.” Process efficiencies have increased steadily; with continuing advancements in nanotechnol­ogy and analytical and computational methods. it is likely that they will continue to do so as the depth of our understanding of atomic level processes grows...

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And what about fusion? At this stage (and into the foreseeable future), it is far from commercially attainable, but there is enormous interest and activity in laying the groundwork for future fusion energy generation. A long sought-after goal, energy from nuclear fusion is attractive for its ability to maximize the power output while minimizing the generation of nuclear waste. The source of energy is the fusion of deuterium and tritium to form helium (Equation 9.18):

?H + 3H ^ *He + 0 n (+17.5 Mev) (9.18)

The amount of energy released from this reaction is 3.5 MeV/nucleon (compared to 0.5 MeV/nucleon for a typical fission reaction (Irvine 2011)). There is no genera­tion of carbon dioxide or other greenhouse gases and no possibility of an uncon­trolled reaction...

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9.4.1 Generation IV Reactors

It should be apparent that an overwhelming concern with respect to nuclear power is the generation of waste. If only we could consume almost all of the troublesome nuclei, then we would not have to concern ourselves with hazardous and expensive reprocessing technologies. Generation IV reactors address this issue along with sev­eral other key aspects:

• Improved “burn-up” of nuclear fuel to result in less hazardous waste and a closed fuel cycle

• Improved safety features

• Transmutation of hazardous fission products

• Hydrogen cogeneration from excess process heat leading to improved efficiencies

In general, Generation IV reactors are fast neutron (or fast-flux) reactors: as opposed to their Generation II and III counterparts, the neutrons are not t...

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Reprocessing Technologies

Of particular interest for sustainability in nuclear energy is reprocessing of spent (or depleted) nuclear fuel. There are three main reasons to reprocess spent nuclear fuel: (1) to recycle the plutonium and uranium and reuse them in a nuclear reactor that can handle this type of mixed oxide fuel (MOX), thus increasing the efficiency of fuel consumption, (2) to decrease the volume of high-level waste, and (3) to sepa­rate out the minor actinides. As noted above, the minor actinides Np-237, Am-241, and Cm-244 are the most hazardous in terms of long-term radiotoxicity. Using the radiotoxicity of naturally occurring uranium as a baseline, it takes around 350,000 years for spent fuel to return to the same level as natural uranium ore...

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Depleted Uranium

There are several sources of waste in the nuclear fuel cycle, from the initial mining to the treatment of spent fuel. For example, after naturally occurring uranium sources have been mined, crushed, and leached out of the ore, the remainder (the tailings) still contains radioactive uranium. There is also the spent fuel from the reactor: fuel rods are replaced on a regular basis, rotating out partially depleted fuel rods and replacing them with fresh fuel. Some of the U-235 undergoes neutron capture instead of fission and, ultimately, only about 75% of the U-235 is consumed in the fuel rod. Hence, the spent fuel contains uranium isotopes, Pu-239, other radioactive fission products, and minor actinides, as shown in Figure 9.5...

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Fuel Reprocessing and Waste Handling

Crucial to the concept of sustainable nuclear energy is a closed fuel cycle, that is, recycling the radioactive fuel and fission products to as full an extent as possible. The once-through mindset of conventional nuclear power cannot continue if we are to achieve any sense of sustainability with respect to nuclear power. That said, a closed fuel cycle requires extensive reprocessing of nuclear waste. The once-through
nuclear fuel cycle is inherently unsustainable, but it is certainly legitimate to weigh the safety issues of excessive handling of radioactive waste (as in reprocessing) against the safety concerns of “disposing” of the waste for thousands of years.

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Uranium Enrichment

The very low concentration of U-235 (the fissile isotope) is problematic because most conventional nuclear reactors require a higher proportion of fissile material. Most commercial reactor fuel is enriched to between 3% and 5% U-235, a product known as reactor-grade uranium. (Nuclear weapons require uranium enriched to greater than 90% U-235 (World Nuclear Association 2013a).) How is the U-235 iso­tope enriched? The methods of enrichment must take advantage of the sole differ­ence between the two isotopes: the fact that U-235 has 92 protons and 143 neutrons while U-238 has 92 protons and 146 neutrons. Even with a difference of only three neutrons, these two isotopes can be separated and the proportion of U-235 increased.

The first step in the enrichment process is the conversion of urani...

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