New Internationalist

DU: From waste to weapon

Issue 406

1 Natural uranium consists of three main isotopes – U235 (0.720%), U238 (99.275%) and U234 (0.005%). Isotopes of an element behave in the same way chemically but vary in the amounts and types of radiation they produce.

Frans Lemmens / STILL PICTURES
Frans Lemmens / STILL PICTURES

2 After uranium has been mined and refined, it is converted into uranium hexafluoride (UF6). This is a solid at normal temperatures but is highly toxic, reacts violently with water and is corrosive to most metals. It is sent to enrichment plants to concentrate the fissionable isotope U235 to between three and five per cent. After this enrichment, the uranium is reactor-ready and can be used for power generation.

http://tinyurl.com/3c7wwb
Chemical forms of uranium during conversion: yellowcake, uranyl nitrate solution [UO2(NO3)2], and solid ammonium diuranate [(NH4)2U2O7]. http://tinyurl.com/3c7wwb

3 After enrichment, the leftover ‘depleted’ uranium is either fed back via reprocessing into the enrichment cycle or stored as waste uranium hexafluoride in large steel cylinders in outdoor yards. This ‘Hex’ is highly corrosive and can eat through and leak out of containers. Currently the world has stockpiles of more than a million tonnes of this waste.

http://tinyurl.com/3dtnch
http://tinyurl.com/3dtnch

4 After enrichment, the leftover ‘depleted’ uranium is either fed back via reprocessing into the enrichment cycle or stored as waste uranium hexafluoride in large steel cylinders in outdoor yards. This ‘Hex’ is highly corrosive and can eat through and leak out of containers. Currently the world has stockpiles of more than a million tonnes of this waste.

http://tinyurl.com/yqzkp7
http://tinyurl.com/yqzkp7

5 DU is 40 per cent less radioactive than natural uranium, but it exists in a far more concentrated form. It has a half-life of 4.5 billion years. This means that, as it decays, many different radioactive elements are created before 50 per cent of it turns into lead 4.5 billion years later.

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