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Radioactivity and coal part II

OK I am back, I might have shocked some of you today when I explained how coal is not just a global warming threat but also a radioactive threat. I looked in the literature to support the fact which I read as a preteen and now plucked from my memory. The first paper which caught my eye was a Turkish paper on coal fly ash.

Some of the coal ash was very radioactive, by UK rules it would be regarded as nuclear waste if it was made at a nuclear site.

For the uninitiated fly ash from burning coal is a wonderful material which can be used to make a “low carbon cement”, the problem with Portland cement is that while it does not emit carbon dioxide when it sets (if anything it absorbs a little) but it requires a lot of fuel to heat up the furnace in which it is made.

Portland cement is made by heating a mixture of clay and limestone in a big slowly turning steel pipe, the fuel use makes Portland cement a rather ungreen building material. A better cement is the geopolymer type which is made from sodium silicate and gently heated kaolin clay. The reduction in the use of fuel at the cement factory makes the geopolymer a more green cement.

The fly ash after it comes out of the coal fired power station is perfectly ready for mixing with Portland cement, thisPortland/ fly ash mixture is perfect for many applications. As no further fuel is needed to process the fly ash by reheating after it comes out of the bag house of the power station makes the fly ask /Portland mixture more green.

One of the disadvantages with this is if the fly ash is contaminated with either toxic heavy metals or radioactivity. If radioactive fly ash cement is used to make houses then it can lead to people being exposed to harmful levels of gamma radiation and/or radon-222. Both the gamma rays (external threat) and the radon (internal threat) can be bad for your health.

Before you get into a panic over radioactive cement it is important to understand that not all fly ash is radioactive, but it is clear to me that we need to take care with the use of fly ash as a building material. I propose that radioactive cements should be used in places where they can contribute only a little to human radiation exposure.

Such places would include

  1. Radioactive waste stores
  2. Nuclear power plants and other buildings in the radiological industry
  3. As a base layer in road building

Also when high radium cements are used some special precautions should be used to protect both workers and the public, paint films and layers of plastic sheet stop the migration of the dangerous radon gas. If a building uses high radium cement in the basement, then a plastic sheet (radon impervious membrane) should be laid over it before a layer of low radium concrete is poured on top. The Swedes had a problem some years ago with a concrete which was radium rich, this is known as “blue concrete”. The blue concrete has the radium in the aggregate rather than the cement but it is still a threat to public health.

But back to cement, it is important to understand the difference in a power generation system between the carbon dioxide emissions from the stack and all the emissions which have occurred during the building and installation of the generator. Next time anyone suggests to you that a wind farm is environmentally friendly and good for the earth’s climate ask them if they have considered all the cement used to make the bases for the wind turbines and all the fuel used to run the furnaces used to make the metal parts.

I do not want to tell you what to think, but I do view it as my duty to inform you about some of the questions you should ask or consider. I would rather that the public did not accept sound bites about how green a technology is, do yourself and the earth a favour! Ask the industry “experts” and NGO experts from Greenpeace/Friends of the Earth/other organisations why they make their claims and try to ‘take the lid off the box and look inside’ by asking questions like…….

“How much fossil fuel is used to make this green electricity generator ?”

“How long will the green electricity generator last ?”

“How much more electric power will we get over the lifetime of the green machine than if we burnt all the fuel used to make it in a furnace and got heat / electric power the simple way ?”

“How much fuel/pollution is needed to recycle this aluminium can (transport and melting) compared with the amount of fuel/pollution needed to dig aluminium ore from the ground and make aluminium can from this ‘primary’ aluminium?”

N.B. The recycling of aluminium is a very green activity; I have been told by a trustworthy source that it saves a lot of fuel and pollution.


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