Neutron Activity in Recycled Fuel

Additional biological hazard in the handling of plutonium recovered from irradiated uranium or of uranium from irradiated thorium arises from fast neutrons produced by (o, n) reaction. Alpha particles from actinide decay react with light elements—lithium, beryllium, carbon, oxygen, etc.—to produce energetic neutrons such as 

The fast neutrons are very penetrating and may require some hydrogenous shielding for protection of operating personnel. Also, techniques to ensure low concentration of light-element contaminants in the recycled actinide material may be required. 

The rate of neutron generation from (a, n) reactions in a fuel containing alpha-emitting actinides and various light elements is predicted from 

Element Average energy of emitted neutron, MeV Neutron flux required to give 100 mrem in 40 h, l tlKctV -s) Neutron emission rate due to contaminant, to give 1000 mrem/40-h wk exposure at surface of 1-kg sphere of uranium or plutonium metal, n/min per gram of metal 

Neutrons per lO alpha disintegrations/ppin of contaminant element 

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