Plutonium processing control limits

Data from critical experiments w required on the criticality of plutonium-uranium nitrate solutions to accurately establish criticality control limits for use in pro-cesang and handling of breeder-ty fueb. Since the flid must be processed both safely and economically, it b necessary that criticality considerations be based on accurate experimental data. Previous expieriments have been reported on plutonium ranium solutions with plutonium weight ratios extending up to some 38 wt% [plutonium weight... 

Ions of different valences of a metal behave like different elements with respect to extract-ability. The difference between Ce and Ce in Table 4.2 is one example. Another is afforded by Pu and Pu 02, which are readily extracted by TBP in kerosene, whereas Pu has a very low distribution coefficient [G31. Consequently, by adjusting the oxidation-reduction potential of the aqueous phase to control the proportion of an element in different valence states, it is possible to vary its distribution coefficient between wide limits. This is the mearts by which plutonium is stripped from aqueous solutions containing plutonium and uranium in sections C and D of Fig. 4.5 illustrating the Purex process. Addition of a reducing... 

Criticality. The process plant is designed on the principle of safe geometry under all conditions (e.g., the use of HARP tanks). Continuous monitoring is provided by an approved criticality detection and alarm system. Where additional operational control is required to maintain safe conditions, this is specified in the appropriate nuclear safety assessments and Criticality Clearance Certificate. The latter specifies limits and conditions that need to be complied with during operations for example, in respect of limited tap density, moisture content, isotopic inventory and mass. It identifies any systems or instrumentation that demonstrate that compliance is maintained during operation. In addition key points of the plant are monitored by neutron monitors to give early warning of the unanticipated build-up of solid plutonium which could lead to the development of unsafe conditions. 

First, it is time to limit the processing of weapon-usable material (separated plutonium and high-enriched uranium) in civilian nuclear programmes, as well as the production of new material through reprocessing and enrichment, by agreeing to restrict these operations exclusively to facilities under multinational control. ... 

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