SO WHAT’S THE BIG RADIATION PROBLEM?

Quote: “Thorium-232 do not produce any gamma rays, but it’s daughter radionuclides do produce the dangerous penetrating gamma rays” Unquote

Pure freshly separated Thorium-232 has only a slight alpha activity. There is no beta radiation and only a slight amount of gamma radiation (from the 0.09-MeV gamma rays which emanate from Th-228 decay).

However, the activity from the Th-228 side of the chain is quickly re-established. A first equilibrium state is reached in about 36 days (10 half-lives of Ra-224).

Activity then declines, as Th-228 decays faster than it is replenished by decaying Ac-228. About 3 years after separation, the activity is lower than at any other time except just after isolation.

Activity then increases until the second equilibrium state is reached in about 60 years or so.

Thorium-232 with all its daughter radionuclides

Total alpha energy = 36.2 MeV per nuclear decay
Total Gamma energy = 3.40 MeV per nuclear decay
Total Beta energy = 5.95 MeV per nuclear decay

Since the Lynas waste has 6 Bq/gm of activity, 1 KILOGRAM would have 6,000 Bq and that will produce 20,400 MeV of gamma ray energy from all the daughter radionuclides at equilibrium.

20,400 MeV from 1 kg of Lynas waste = 0.0000000007808 calories or 0.000000003268 joules.

This amount of gamma ray energy from 1 KILOGRAM of Lynas waste is not enough to tickle the backside of even a tiny little newborn caterpillar!

The total alpha energy is much larger i.e. 36.2 MeV but since alpha radiation does not pose an external threat and Thorium in clay soil is not absorbed, and since inhalation only affects miners, it is not a problem either for the Kuantan folks. But it may be a problem for those poor Australian miners in Mount Weld in Western Australia.

So, the Australians are the ones getting the wrong side of the deal!

Dust particles can get deep into the lungs only if they are very small i.e. much less than 10 micron. The particles that are less than 5 microns are the ones which can get deep into the alveoli of the lungs. Larger ones are trapped by the mucus in the nose and upper respiratory tract and are coughed out or sneezed out.

Particles of less than 5 microns can only be found in the Thorium and Uranium mines where powerful machines are used or where there is combustion.

Since alpha radiation cannot go far (the 4.0 MeV alpha particle from Thorium-232 decay can travel only 27.8 microns in water), even if you have a huge pile of Lynas waste, the external radiation would not increase by much because only the tiny percentage of thorium-232 atoms directly on the surface of the pile will be able to radiate out their alpha particles.

Those just below the surface will remain inside the pile and be converted to simple helium gas and those on the surface will travel only 2.54 cm into the air, picks up 2 electrons and become the harmless Helium for you to fill up your balloon.

The beta particles which are electrons (electricity = flow of electrons) do not pose an external threat either. There are lots more high voltage electrons on your clothing as static electricity when you stay in a dry air-condition room than from the waste.

Only gamma rays from your mountain of Lynas waste from less than 45 cm deep (depending on the type of soil and the water content) are able to see the light of day, as those deeper than that will be blocked by the layer of soil from getting out. And as shown above the amount of gamma rays are insignificant.

When the mother radionuclide has an extremely long half life and the daughters have very short half life, there is very little accumulation of the short half life daughters.

For instance, I did a quick calculation and found that the concentration of the daughter radionuclides is negligible e.g. there is only 1 atom of Radium 224 for every 1.4 trillion atoms of Thorium-232 at equilibrium (I stand to be corrected).

As far as radon gas is concerned, it must be remembered that Radon-220 from the decay chain of Thorium-232 has a very short half life of only 55 seconds!

As such only a tiny amount of Radon-220 (a.k.a. Thoron) within a few centimetres of the surface of a huge pile of waste will be able to live long enough to escape from the pile and see the light of day!

A lot of people have mistaken Radon-220 from Thorium-232 decay series with the more notorious Radon-222 which has a much longer half life of 3.8 days. Radon-222 comes from Uranium-238 decay series.

Because of its much longer half life, Radon-222 can and do accumulate in the cellars and poorly ventilated areas of domestic dwellings. Radon-222 is the gas that has been linked to lung cancers in especially non-smokers.

So please do not blame poor Thorium-232. It does not produce any Radon-222 and as such is not guilty of radon induced lung cancers.