Neptunium losses

This element has not been found in any naturally occurring mineral but Seaborg believes it may exist in minute amounts as the result of neutron bombardment in uranium ores (63). Neptunium is not absorbed from the digestive tract of animals, but when it is injected it tends to accumulate in the bones. Subsequent loss from this site is very slow (64, 65). 

Americium and curium injected into animals are distributed to the extent of about 25 per cent in bone, but unlike neptunium and plutonium, about 70 per cent of the injected dose is found in the liver. Loss from the... 

Loss of HLW container spacing may occur in a salt repository by brine intrusion with subsequent salt dissolution. Loss of spacing could result in hundreds of HLW containers in contact. The criticality safety implications of such an event were examined using the KENO code with 16-group Hansen-Roach cross sections. Hansen-Roach crr sections were not available for neptunium, americium, or curium. Therefore, Pu was substituted for Np, since their fission cross sections and fast critical masses are essentially identical. Similarly, was substituted for americum and curium. 

Calculations of the reactivity gains In a reactor due to plutonium buildup assume Instantaneous formation of plutonium. The fact that plutonlum-239 formation Is delayed throuc the beta-decay of 2.33 day neptunium-239 makes It necessary to correct the calculated reactivity gains. This Is most conveniently done by assigning a reactivity loss for the neptunium holdup effect. The equilibrium neptunium holdup defect Is. 41 k. 

The redox potential of the Np /Np couple has been measured in alkaline media, the neptunium(vi) species in 0.1—1.5M sodium hydroxide being present as the ion Np02(OH)4 oxidation to Np is considered to involve the loss of two hydroxide groups. Neptunium(vi) is also formed in the reaction of Np with nitrate ion in aqueous nitric acid ... 

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