Except for the nuclear waste and possible leaks at nuclear power stations, which is a concern, nuclear Is as green as it gets.

Coal is polluting, from pit to ash dump. One does better by using integrated gasification combined cycle (IGCC) with coal, which is considered a clean coal technology. Unfortunately this gets on the expensive side and nuclear probably makes more economic sense. Another clean coal (better than mining) is underground coal gasification, but has only been implemented on limited scale.

One just need to look at the enormous ash dumps at coal power stations and the destruction of the environment at collieries, not to mention nasties such as mercury and arsenic released into the environment, to realize how bad coal is. The bottom line is, we cannot indefinitely keep pumping CO2 into our atmosphere at ever increasing rates.

I think the ultimate combination will be PWR nuclear working concurrently with pebble bed Thorium-based reactors. The U238 and Plutonium wastes are used as neutron source to fire up the Thorium reactors, which leaves one with much more manageable nuclear wastes (80 yr half life, if I recall correctly) Have a look at http://www.thorium100.com/ for info on Th-based pebble bed reactors.

Thorium + traditional nuclear will have to do until we master fusion

It is an undeniable reality that energy production and their sustained growth constitute indispensable elements to ensure the economic and social progress of any country. For this reason, the possible use of all types of energy sources available in the country should be in the mind of politicians and experts during the elaboration of the best possible energy mix for the country. The purpose of this effort is to ensure the maximum economic and social development of the country under the prevailing economic and political international conditions.

However, there are certain factors that need to be considered by the competent authorities of a country during the selection of the most efficient and economic combination of energy sources for the generation of electricity. For instance, the use of fossil fuels is a major and growing contributor to the emission of CO2, and, for this reason, any increase in the use of this type of energy source for this specific purpose will increase the emission of CO2; nuclear energy and renewable energy sources are almost carbon dioxide free but a nuclear accident could have devastator consequences for the environment and the population, not only in the surround area of the plant site, but for the environment and the population living far away from this site; the prices of the different fossil fuels are increasing and the reserves decreasing; and some renewable energy sources are not yet ready to be used for the generation of electricity in large scale and inexpensively, at least during the coming years.

Considering the different energy sources available in the world that can be used now to meet the foreseeable increase in energy demand during the coming years, there should be no doubt that, at least for the next decades, there are only a few realistic options available to reduce further the CO2 emissions as a result of the electricity generation. These options are, among others, the following:

•Increase efficiency in electricity generation and use;

•Expand use of all available renewable energy sources such as hydro, wind, solar,

biomass and geothermal;

•Massive introduction of new advanced technology like the capture carbon dioxide emissions technology at fossil-fueled (especially coal) electric generating plants, in order to permanently sequester the carbon produced by these plants;

• Increase use of new types of nuclear power reactors that are inherently safe and proliferation risk-free (Generation III, III+ and IV);

•Increase energy saving (Morales Pedraza, 2010).

The amount of total electricity produced and used per capita is increasing in several countries, particularly in emerging countries such as China, India, Brazil, South Africa, the

Republic of Korea, and Russia. Due to the increase in the demand of energy, the world total energy requirements increased from 6 181 TW per year in 1970 to 21 431 TW per year in 2010; this represents an increase of 246 %.

According to estimates made by the World Energy Council and the International Institute for Applied Systems, among other international organizations, the demand of electricity probably triple from now until 2050.

The following are, among others, the main reasons for this significantly increase:

•Increase in the world population;

•Increase in the percentage of the world population living in big cities, which increase the demand of electricity;

•Improve the quality of life of the world population bringing as consequence an

increase in the demand of electricity;

•Increase in the demand of electricity in the most advanced developing countries such as India, China, Brazil, South Africa, and the Republic of Korea, among others, due to their fast economic and social development.

The problem that the world is now facing is how to meet the foreseeable increase in the demand of energy using all available energy sources in the most efficient and economic manner and without increasing the emission of CO2 to the atmosphere.

Undoubtedly, one of the available types of energy sources that have probed in the past that can be effectively used for the generation of electricity is nuclear energy. Can be stated that nuclear energy could be safely used for electricity generation in the future despite the serious accidents occurred in nuclear power plants since 1979? The answer to this question is yes, nuclear energy can play again an important role in the energy balance of several countries from almost all regions, as it did in the 1960s, 1970s and 1980s, if important additional safety measures are introduced in all nuclear power reactors currently in operation in all countries without exception. These additional measures will reduce to the minimum the

possibility of having a new serious nuclear accident similar to the ones occurred in the USA in 1979, Ukraine in 1986, and in Japan in 2011.

The International Energy Outlook for 2011 (IEO 2011) indicated that electricity

generation from nuclear power worldwide is expected to increase from 2.6 trillion kWh in 2008 to 4.9 trillion kWh in 2035, an increase of 88 %. However, there is a great concern about building new nuclear capacity due to construction costs, energy security and greenhouse gas emissions.

Undoubtedly, higher fossil fuel prices allow nuclear power to become economically competitive for the generation of electricity in comparison to coal, natural gas and liquids, despite the relatively high initial capital and maintenance costs associated with the construction and operation of nuclear power plants. Moreover, higher capacity utilization rates have been reported for many existing nuclear power plants. According to the IAEA, in 1990 the world average annual capacity factor for nuclear power plants was 67.7 %. In 2005, this figure increases up to 81.4 %, which is the equivalent to the construction of some 74 new nuclear power units.

However, it is important to highlight that the current level of the capacity factor of the

nuclear power reactors in operation in the world and the number of nuclear power reactors under construction is not enough to meet the foreseeable increase in the demand of electricity in the coming years in almost all regions. If the governments of the different countries where power operate wish to increase the role of nuclear energy in the energy mix of these countries, then they should play a stronger role in facilitating private investment, especially in liberalized markets and if concerns about plant safety, nuclear waste disposal, and the risk of proliferation can be solved to the satisfaction of the public.