os argumentos são o que são... e essa é a verdade que sei.
não vale a pena mentir....
a radiação é boa? pá, se implicar uma lareira e uma míuda, o espectro infravermelho é completamente bem vindo...
estamos a trocar um pouco das nossas emissões de co2 por radioactividade, sim...
o problema é que o nosso fundo de carbono estima-se que vá atingir cerca de 40.000.000€, quando o necessário para pagar as nossas emissões é 1.100.000.000€.
podemos troca-la antes por radiação é bem mais saudável.
radiação saudável não é, a não ser no contexto médico... mas como já disse aí para trás, o arsénico, urânio, chumbo, mercúrio, enxofre e por aí fora existentes no carvão, também não são muito saudáveis... e esses ficam para sempre, mesmo.
é um mal menor....
over 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.
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.
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.
