RE: [escepticos] re: Resumen sobre la jornada de Cambio Climático (II)

[Rodolfo del Moral]

 Hola,

 Me ha parecido gracioso en ocasiones, pero un poco demagógico en
ocasiones, por lo que puede generar el efecto contrario al deseado.

  Un saludo,

                               Rodolfo del Moral

-----Mensaje original-----
De: escepticos-bounces en dis.ulpgc.es
[mailto:escepticos-bounces en dis.ulpgc.es] En nombre de Ramón Ordiales
Enviado el: 04 September 2006 13:16
Para: escepticos en dis.ulpgc.es
Asunto: [escepticos] re: Resumen sobre la jornada de Cambio Climático
(II)



 Para echar más leña al fuego:

 http://www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html



> Una central térmica es más radiactiva que una nuclear... (o eso
> afirman... )
>
> ----------
>
>
>
>
> ver the past few decades, the American public has become increasingly 
> wary of nuclear power because of concern about radiation releases from

> normal plant operations, plant accidents, and nuclear waste. Except 
> for Chernobyl and other nuclear accidents, releases have been found to

> be almost undetectable in comparison with natural background 
> radiation. Another concern has been the cost of producing electricity 
> at nuclear plants. It has increased largely for two reasons: 
> compliance with stringent government regulations that restrict 
> releases of radioactive substances from nuclear facilities into the 
> environment and construction delays as a result of public opposition.
>
>
>
>
> Partly because of these concerns about radioactivity and the cost of 
> containing it, the American public and electric utilities have 
> preferred coal combustion as a power source. Today 52% of the capacity

> for generating electricity in the United States is fueled by coal, 
> compared with 14.8% for
> nuclear energy. Although there are economic justifications for this
> preference, it is surprising for two reasons. First, coal combustion
> produces carbon dioxide and other greenhouse gases that are suspected
to
> cause climatic warming, and it is a source of sulfur oxides and
nitrogen
> oxides, which are harmful to human health and may be largely
responsible 
> for
> acid rain. Second, although not as well known, releases from coal 
> combustion
> contain naturally occurring radioactive materials--mainly, uranium and
> thorium.
>
> Former ORNL researchers J. P. McBride, R. E. Moore, J. P. Witherspoon,

> and R. E. Blanco made this point in their article "Radiological Impact

> of Airborne Effluents of Coal and Nuclear Plants" in the December 8, 
> 1978, issue of Science magazine. They concluded that Americans living 
> near coal-fired power plants are exposed to higher radiation doses 
> than those living near nuclear power plants that meet government 
> regulations. This ironic situation remains true today and is addressed

> in this article.
>
> The fact that coal-fired power plants throughout the world are the 
> major sources of radioactive materials released to the environment has

> several implications. It suggests that coal combustion is more 
> hazardous to health than nuclear power and that it adds to the 
> background radiation burden even more than does nuclear power. It also

> suggests that if radiation emissions from coal plants were regulated, 
> their capital and operating costs would increase, making coal-fired 
> power less economically competitive.
>
> Finally, radioactive elements released in coal ash and exhaust 
> produced by coal combustion contain fissionable fuels and much larger 
> quantities of fertile materials that can be bred into fuels by 
> absorption of neutrons, including those generated in the air by 
> bombardment of oxygen, nitrogen, and other nuclei with cosmic rays; 
> such fissionable and fertile materials can be
> recovered from coal ash using known technologies. These nuclear
materials
> have growing value to private concerns and governments that may want
to
> market them for fueling nuclear power plants. However, they are also
> available to those interested in accumulating material for nuclear 
> weapons.
> A solution to this potential problem may be to encourage electric 
> utilities
> to process coal ash and use new trapping technologies on coal
combustion
> exhaust to isolate and collect valuable metals, such as iron and
aluminum,
> and available nuclear fuels.
>
> Makeup of Coal and Ash
>
> Coal is one of the most impure of fuels. Its impurities range from 
> trace quantities of many metals, including uranium and thorium, to 
> much larger quantities of aluminum and iron to still larger quantities

> of impurities such as sulfur. Products of coal combustion include the 
> oxides of carbon, nitrogen, and sulfur; carcinogenic and mutagenic 
> substances; and recoverable minerals of commercial value, including 
> nuclear fuels naturally occurring in
> coal.
>
>
>
>
> Coal ash is composed primarily of oxides of silicon, aluminum, iron, 
> calcium, magnesium, titanium, sodium, potassium, arsenic, mercury, and

> sulfur plus small quantities of uranium and thorium. Fly ash is 
> primarily composed of non-combustible silicon compounds (glass) melted

> during combustion. Tiny glass spheres form the bulk of the fly ash.
>
> Since the 1960s particulate precipitators have been used by U.S.
> coal-fired
> power plants to retain significant amounts of fly ash rather than
letting 
> it
> escape to the atmosphere. When functioning properly, these
precipitators 
> are
> approximately 99.5% efficient. Utilities also collect furnace ash, 
> cinders,
> and slag, which are kept in cinder piles or deposited in ash ponds on
> coal-plant sites along with the captured fly ash.
>
> Trace quantities of uranium in coal range from less than 1 part per
> million
> (ppm) in some samples to around 10 ppm in others. Generally, the
amount of
> thorium contained in coal is about 2.5 times greater than the amount
of
> uranium. For a large number of coal samples, according to
Environmental
> Protection Agency figures released in 1984, average values of uranium
and
> thorium content have been determined to be 1.3 ppm and 3.2 ppm,
> respectively. Using these values along with reported consumption and
> projected consumption of coal by utilities provides a means of
calculating
> the amounts of potentially recoverable breedable and fissionable
elements
> (see sidebar). The concentration of fissionable uranium-235 (the
current
> fuel for nuclear power plants) has been established to be 0.71% of
uranium
> content.
>
> Uranium and Thorium in Coal and Coal Ash
>
> As population increases worldwide, coal combustion continues to be the

> dominant fuel source for electricity. Fossil fuels' share has 
> decreased from 76.5% in 1970 to 66.3% in 1990, while nuclear energy's 
> share in the worldwide electricity pie has climbed from 1.6% in 1970 
> to 17.4% in 1990. Although U.S. population growth is slower than 
> worldwide growth, per capita
> consumption of energy in this country is among the world's highest. To

> meet
> the growing demand for electricity, the U.S. utility industry has
> continually expanded generating capacity. Thirty years ago, nuclear
power
> appeared to be a viable replacement for fossil power, but today it
> represents less than 15% of U.S. generating capacity. However, as a
result
> of low public support during recent decades and a reduction in the
rate of
> expected power demand, no increase in nuclear power generation is
expected
> in the foreseeable future. As current nuclear power plants age, many 
> plants
> may be retired during the first quarter of the 21st century, although
some
> may have their operation extended through license renewal. As a
result, 
> many
> nuclear plants are likely to be replaced with coal-fired plants unless
it 
> is
> considered feasible to replace them with fuel sources such as natural
gas
> and solar energy.
>
>
>
> As the world's population increases, the demands for all resources, 
> particularly fuel for electricity, is expected to increase. To meet 
> the demand for electric power, the world population is expected to 
> rely increasingly on combustion of fossil fuels, primarily coal. The 
> world has about 1500 years of known coal resources at the current use 
> rate. The graph above shows the growth in U.S. and world coal 
> combustion for the 50 years preceding 1988, along with projections 
> beyond the year 2040. Using the concentration of uranium and thorium 
> indicated above, the graph below illustrates the historical release 
> quantities of these elements and the releases that can be expected 
> during the first half of the next century, given the predicted growth 
> trends. Using these data, both U.S. and worldwide
> fissionable uranium-235 and fertile nuclear material releases from
coal
> combustion can be calculated.
>
>
>
> Because existing coal-fired power plants vary in size and electrical
> output,
> to calculate the annual coal consumption of these facilities, assume
that
> the typical plant has an electrical output of 1000 megawatts. Existing
> coal-fired plants of this capacity annually burn about 4 million tons
of
> coal each year. Further, considering that in 1982 about 616 million
short
> tons (2000 pounds per ton) of coal was burned in the United States
(from 
> 833
> million short tons mined, or 74%), the number of typical coal-fired
plants
> necessary to consume this quantity of coal is 154.
>
> Using these data, the releases of radioactive materials per typical 
> plant can be calculated for any year. For the year 1982, assuming coal

> contains uranium and thorium concentrations of 1.3 ppm and 3.2 ppm, 
> respectively, each typical plant released 5.2 tons of uranium 
> (containing 74 pounds of
> uranium-235) and 12.8 tons of thorium that year. Total U.S. releases
in 
> 1982
> (from 154 typical plants) amounted to 801 tons of uranium (containing 
> 11,371
> pounds of uranium-235) and 1971 tons of thorium. These figures account
for
> only 74% of releases from combustion of coal from all sources.
Releases in
> 1982 from worldwide combustion of 2800 million tons of coal totaled
3640
> tons of uranium (containing 51,700 pounds of uranium-235) and 8960
tons of
> thorium.
>
> Based on the predicted combustion of 2516 million tons of coal in the
> United
> States and 12,580 million tons worldwide during the year 2040,
cumulative
> releases for the 100 years of coal combustion following 1937 are
predicted
> to be:
>
>
>  U.S. release (from combustion of 111,716 million tons):
>  Uranium: 145,230 tons (containing 1031 tons of uranium-235)
>
>  Thorium: 357,491 tons
>
>  Worldwide release (from combustion of 637,409 million tons):
>
>  Uranium: 828,632 tons (containing 5883 tons of uranium-235)
>
>  Thorium: 2,039,709 tons
>
>
> Radioactivity from Coal Combustion
> The main sources of radiation released from coal combustion include 
> not
> only
> uranium and thorium but also daughter products produced by the decay
of
> these isotopes, such as radium, radon, polonium, bismuth, and lead. 
> Although
> not a decay product, naturally occurring radioactive potassium-40 is
also 
> a
> significant contributor.
>
>
>
> According to the National Council on Radiation Protection and 
> Measurements (NCRP), the average radioactivity per short ton of coal 
> is 17,100 millicuries/4,000,000 tons, or 0.00427 millicuries/ton. This

> figure can be used to calculate the average expected radioactivity 
> release from coal combustion. For 1982 the total release of 
> radioactivity from 154 typical coal plants in the United States was, 
> therefore, 2,630,230 millicuries.
>
> Thus, by combining U.S. coal combustion from 1937 (440 million tons)
> through
> 1987 (661 million tons) with an estimated total in the year 2040 (2516
> million tons), the total expected U.S. radioactivity release to the
> environment by 2040 can be determined. That total comes from the
expected
> combustion of 111,716 million tons of coal with the release of
477,027,320
> millicuries in the United States. Global releases of radioactivity
from 
> the
> predicted combustion of 637,409 million tons of coal would be 
> 2,721,736,430
> millicuries.
>
> For comparison, according to NCRP Reports No. 92 and No. 95, 
> population exposure from operation of 1000-MWe nuclear and coal-fired 
> power plants amounts to 490 person-rem/year for coal plants and 4.8 
> person-rem/year for nuclear plants. Thus, the population effective 
> dose equivalent from coal plants is 100 times that from nuclear 
> plants. For the complete nuclear fuel cycle, from mining to reactor 
> operation to waste disposal, the radiation dose is cited as 136 
> person-rem/year; the equivalent dose for coal use, from
> mining to power plant operation to waste disposal, is not listed in
this
> report and is probably unknown.
>
> During combustion, the volume of coal is reduced by over 85%, which 
> increases the concentration of the metals originally in the coal. 
> Although significant quantities of ash are retained by precipitators, 
> heavy metals such as uranium tend to concentrate on the tiny glass 
> spheres that make up the bulk of fly ash. This uranium is released to 
> the atmosphere with the escaping fly ash, at about 1.0% of the 
> original amount, according to NCRP data. The retained ash is enriched 
> in uranium several times over the original uranium concentration in 
> the coal because the uranium, and thorium, content is not decreased as

> the volume of coal is reduced.
>
> All studies of potential health hazards associated with the release of

> radioactive elements from coal combustion conclude that the 
> perturbation of natural background dose levels is almost negligible. 
> However, because the half-lives of radioactive potassium-40, uranium, 
> and thorium are practically
> infinite in terms of human lifetimes, the accumulation of these
species in
> the biosphere is directly proportional to the length of time that a 
> quantity
> of coal is burned.
>
> Although trace quantities of radioactive heavy metals are not nearly 
> as likely to produce adverse health effects as the vast array of 
> chemical by-products from coal combustion, the accumulated quantities 
> of these isotopes over 150 or 250 years could pose a significant 
> future ecological burden and potentially produce adverse health 
> effects, especially if they are locally accumulated. Because coal is 
> predicted to be the primary energy source for electric power 
> production in the foreseeable future, the potential impact of 
> long-term accumulation of by-products in the biosphere should be 
> considered.
>
>
>
>
> Energy Content: Coal vs Nuclear
>
> An average value for the thermal energy of coal is approximately 6150 
> kilowatt-hours(kWh)/ton. Thus, the expected cumulative thermal energy 
> release from U.S. coal combustion over this period totals about 6.87 x

> 10E14 kilowatt-hours. The thermal energy released in nuclear fission 
> produces about 2 x 10E9 kWh/ton. Consequently, the thermal energy from

> fission of uranium-235 released in coal combustion amounts to 2.1 x 
> 10E12 kWh. If uranium-238 is bred to plutonium-239, using these data 
> and assuming a "use factor" of 10%, the thermal energy from fission of

> this isotope alone constitutes about 2.9 x 10E14 kWh, or about half 
> the anticipated energy of all the utility coal burned in this country 
> through the year 2040. If the thorium-232 is bred to uranium-233 and 
> fissioned with a similar "use factor", the thermal energy capacity of 
> this isotope is approximately 7.2 x
> 10E14 kWh, or 105% of the thermal energy released from U.S. coal 
> combustion
> for a century. Assuming 10% usage, the total of the thermal energy
> capacities from each of these three fissionable isotopes is about 10.1
x
> 10E14 kWh, 1.5 times more than the total from coal. World combustion
of 
> coal
> has the same ratio, similarly indicating that coal combustion wastes
more
> energy than it produces.
>
>
>
> Consequently, the energy content of nuclear fuel released in coal
> combustion
> is more than that of the coal consumed! Clearly, coal-fired power
plants 
> are
> not only generating electricity but are also releasing nuclear fuels
whose
> commercial value for electricity production by nuclear power plants is

> over
> $7 trillion, more than the U.S. national debt. This figure is based on
> current nuclear utility fuel costs of 7 mils per kWh, which is about
half
> the cost for coal. Consequently, significant quantities of nuclear 
> materials
> are being treated as coal waste, which might become the cleanup
nightmare 
> of
> the future, and their value is hardly recognized at all.
>
> How does the amount of nuclear material released by coal combustion
> compare
> to the amount consumed as fuel by the U.S. nuclear power industry? 
> According
> to 1982 figures, 111 American nuclear plants consumed about 540 tons
of
> nuclear fuel, generating almost 1.1 x 10E12 kWh of electricity. During
the
> same year, about 801 tons of uranium alone were released from American
> coal-fired plants. Add 1971 tons of thorium, and the release of
nuclear
> components from coal combustion far exceeds the entire U.S.
consumption of
> nuclear fuels. The same conclusion applies for worldwide nuclear fuel
and
> coal combustion.
>
> Another unrecognized problem is the gradual production of 
> plutonium-239 through the exposure of uranium-238 in coal waste to 
> neutrons from the air. These neutrons are produced primarily by 
> bombardment of oxygen and nitrogen
> nuclei in the atmosphere by cosmic rays and from spontaneous fission
of
> natural isotopes in soil. Because plutonium-239 is reportedly toxic in
> minute quantities, this process, however slow, is potentially
worrisome. 
> The
> radiotoxicity of plutonium-239 is 3.4 x 10E11 times that of
uranium-238.
> Consequently, for 801 tons of uranium released in 1982, only 2.2 
> milligrams
> of plutonium-239 bred by natural processes, if those processes exist,
is
> necessary to double the radiotoxicity estimated to be released into
the
> biosphere that year. Only 0.075 times that amount in plutonium-240
doubles
> the radiotoxicity. Natural processes to produce both plutonium-239 and
> plutonium-240 appear to exist.
>
> Conclusions
>
> For the 100 years following 1937, U.S. and world use of coal as a heat

> source for electric power generation will result in the distribution 
> of a variety of radioactive elements into the environment. This 
> prospect raises several questions about the risks and benefits of coal

> combustion, the leading source of electricity production.
>
> First, the potential health effects of released naturally occurring 
> radioactive elements are a long-term issue that has not been fully 
> addressed. Even with improved efficiency in retaining stack emissions,

> the removal of coal from its shielding overburden in the earth and 
> subsequent combustion releases large quantities of radioactive 
> materials to the surface of the earth. The emissions by coal-fired 
> power plants of greenhouse gases,
> a vast array of chemical by-products, and naturally occurring
radioactive
> elements make coal much less desirable as an energy source than is 
> generally
> accepted.
>
> Second, coal ash is rich in minerals, including large quantities of
> aluminum
> and iron. These and other products of commercial value have not been
> exploited.
>
> Third, large quantities of uranium and thorium and other radioactive
> species
> in coal ash are not being treated as radioactive waste. These products

> emit
> low-level radiation, but because of regulatory differences, coal-fired

> power
> plants are allowed to release quantities of radioactive material that 
> would
> provoke enormous public outcry if such amounts were released from
nuclear
> facilities. Nuclear waste products from coal combustion are allowed to
be
> dispersed throughout the biosphere in an unregulated manner. Collected
> nuclear wastes that accumulate on electric utility sites are not
protected
> from weathering, thus exposing people to increasing quantities of
> radioactive isotopes through air and water movement and the food
chain.
>
> Fourth, by collecting the uranium residue from coal combustion,
> significant
> quantities of fissionable material can be accumulated. In a few year's

> time,
> the recovery of the uranium-235 released by coal combustion from a
typical
> utility anywhere in the world could provide the equivalent of several 
> World
> War II-type uranium-fueled weapons. Consequently, fissionable nuclear
fuel
> is available to any country that either buys coal from outside sources
or
> has its own reserves. The material is potentially employable as weapon

> fuel
> by any organization so inclined. Although technically complex, 
> purification
> and enrichment technologies can provide high-purity, weapons-grade
> uranium-235. Fortunately, even though the technology is well known,
the
> enrichment of uranium is an expensive and time-consuming process.
>
> Because electric utilities are not high-profile facilities, collection

> and processing of coal ash for recovery of minerals, including uranium

> for weapons or reactor fuel, can proceed without attracting outside 
> attention, concern, or intervention. Any country with coal-fired 
> plants could collect combustion by-products and amass sufficient 
> nuclear weapons material to build up a very powerful arsenal, if it 
> has or develops the technology to do so. Of far greater potential are 
> the much larger quantities of thorium-232 and uranium-238 from coal 
> combustion that can be used to breed fissionable isotopes. Chemical 
> separation and purification of uranium-233 from thorium and 
> plutonium-239 from uranium require far less effort than enrichment of 
> isotopes. Only small fractions of these fertile elements in coal 
> combustion residue are needed for clandestine breeding of fissionable 
> fuels and weapons
> material by those nations that have nuclear reactor technology and the
> inclination to carry out this difficult task.
>
> Fifth, the fact that large quantities of uranium and thorium are 
> released from coal-fired plants without restriction raises a 
> paradoxical question. Considering that the U.S. nuclear power industry

> has been required to invest in expensive measures to greatly reduce 
> releases of radioactivity from nuclear fuel and fission products to 
> the environment, should coal-fired power plants be allowed to do so 
> without constraints?
>
>
>
> This question has significant economic repercussions. Today nuclear 
> power plants are not as economical to construct as coal-fired plants, 
> largely because of the high cost of complying with regulations to 
> restrict emissions of radioactivity. If coal-fired power plants were 
> regulated in a similar manner, the added cost of handling nuclear 
> waste from coal combustion would
> be significant and would, perhaps, make it difficult for coal-burning 
> plants
> to compete economically with nuclear power.
>
> Because of increasing public concern about nuclear power and 
> radioactivity in the environment, reduction of releases of nuclear 
> materials from all sources has become a national priority known as "as

> low as reasonably achievable" (ALARA). If increased regulation of 
> nuclear power plants is demanded, can we expect a significant 
> redirection of national policy so that radioactive emissions from coal

> combustion are also regulated?
>
> Although adverse health effects from increased natural background 
> radioactivity may seem unlikely for the near term, long-term 
> accumulation of radioactive materials from continued worldwide 
> combustion of coal could pose
> serious health hazards. Because coal combustion is projected to
increase
> throughout the world during the next century, the increasing
accumulation 
> of
> coal combustion by-products, including radioactive components, should
be
> discussed in the formulation of energy policy and plans for future
energy
> use.
>
> One potential solution is improved technology for trapping the exhaust

> (gaseous emissions up the stack) from coal combustion. If and when 
> such technology is developed, electric utilities may then be able both

> to recover useful elements, such as nuclear fuels, iron, and aluminum,

> and to trap greenhouse gas emissions. Encouraging utilities to enter 
> mineral markets that have been previously unavailable may or may not 
> be desirable, but doing
> so appears to have the potential of expanding their economic base,
thus
> offsetting some portion of their operating costs, which ultimately
could
> reduce consumer costs for electricity.
>
> Both the benefits and hazards of coal combustion are more far-reaching
> than
> are generally recognized. Technologies exist to remove, store, and 
> generate
> energy from the radioactive isotopes released to the environment by
coal
> combustion. When considering the nuclear consequences of coal
combustion,
> policymakers should look at the data and recognize that the amount of
> uranium-235 alone dispersed by coal combustion is the equivalent of
dozens
> of nuclear reactor fuel loadings. They should also recognize that the
> nuclear fuel potential of the fertile isotopes of thorium-232 and
> uranium-238, which can be converted in reactors to fissionable
elements by
> breeding, yields a virtually unlimited source of nuclear energy that
is
> frequently overlooked as a natural resource.
>
>
>
> In short, naturally occurring radioactive species released by coal 
> combustion are accumulating in the environment along with minerals 
> such as mercury, arsenic, silicon, calcium, chlorine, and lead, 
> sodium, as well as metals such as aluminum, iron, lead, magnesium, 
> titanium, boron, chromium, and others that are continually dispersed 
> in millions of tons of coal combustion by-products. The potential 
> benefits and threats of these released materials will someday be of 
> such significance that they should not now be ignored.--Alex Gabbard 
> of the Metals and Ceramics Division
>
> References and Suggested Reading
>
> J. F. Ahearne, "The Future of Nuclear Power," American Scientist, 
> Jan.-Feb
> 1993: 24-35.
>
> E. Brown and R. B. Firestone, Table of Radioactive Isotopes, Wiley 
> Interscience, 1986.
>
> J. O. Corbett, "The Radiation Dose From Coal Burning: A Review of 
> Pathways and Data," Radiation Protection Dosimetry, 4 (1): 5-19.
>
> R. R. Judkins and W. Fulkerson, "The Dilemma of Fossil Fuel Use and 
> Global Climate Change," Energy & Fuels, 7 (1993) 14-22.
>
> National Council on Radiation Protection, Public Radiation Exposure 
> From Nuclear Power Generation in the U.S., Report No. 92, 1987, 
> 72-112.
>
> National Council on Radiation Protection, Exposure of the Population 
> in
> the
> United States and Canada from Natural Background Radiation, Report No.
94,
> 1987, 90-128.
>
> National Council on Radiation Protection, Radiation Exposure of the 
> U.S. Population from Consumer Products and Miscellaneous Sources, 
> Report No. 95, 1987, 32-36 and 62-64.
>
> Serge A. Korff, "Fast Cosmic Ray Neutrons in the Atmosphere," 
> Proceedings
> of
> International Conference on Cosmic Rays, Volume 5: High Energy 
> Interactions,
> Jaipur, December 1963.
>
> C. B. A. McCusker, "Extensive Air Shower Studies in Australia,"
> Proceedings
> of International Conference on Cosmic Rays, Volume 4: Extensive Air 
> Showers,
> Jaipur, December 1963.
>
> T. L. Thoem, et al., Coal Fired Power Plant Trace Element Study, 
> Volume 1:
> A
> Three Station Comparison, Radian Corp. for USEPA, Sept. 1975.
>
> W. Torrey, "Coal Ash Utilization: Fly Ash, Bottom Ash and Slag," 
> Pollution Technology Review, 48 (1978) 136.
>
>
>
> 

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