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Safe U and Pu Storage

#0332


A Safe Method for Storing Large Masses of Plutonium and Uranium after Dismount of Nuclear Weapons.

Tech Area / Field

  • FIR-FUE/Reactor Fuels and Fuel Engineering/Fission Reactors

Status
8 Project completed

Registration date
05.01.1995

Completion date
31.12.1996

Senior Project Manager
Tyurin I A

Leading Institute
VNIIEF, Russia, N. Novgorod reg., Sarov

Supporting institutes

  • All-Russian Scientific Research Institute of Non-Organic Materials named after A. Bochvar, Russia, Moscow

Collaborators

  • Forschungszentrum Karlsruhe Technik und Umwelt / Institut für Nukleare Entsorgungstechnik, Germany, Karlsruhe

Project summary

The goal of this Project is experimental refinement of techniques for weapon-grade plutonium and uranium reprocessing into material non-interacting with oxygen, free of critical mass and suitable for a safest and most convenient storage of large masses (up to 10-50 tons) of reprocessed plutonium and uranium.

The works to study behavior of developed materials at storage and computational estimations for the questions arising at the storage (preliminary selection of repository option, thermal conditions at storage, behavior in an emergency, etc.) will be simultaneously conducted.

Phase I Project Results

As a result of the Project Phase I performance two scientific-technical reports (interim and final) were issued and a meeting with foreign collaborators was held.

In reports analysis of problem of excess weapon-grade plutonium storage and the role in this problem of suggested plutonium storage technique in the form of inert critical-mass-free composition is done.

One of this analysis results is justification of importance and actuality of the problem of choosing safe handling excess plutonium and highly-enriched uranium released due to nuclear weapons reduction. These materials are not only of high radiation risk but also of high ecological danger because in the case of persion or elemental calamities (fire, flood, etc.) substantial contamination of air and water basins is possible due to their high toxicity.

Phase I investigation and discussion with foreign collaborators showed the necessity of experimental works with neutron absorbers such as Hf, Gd which are more resistant to water influence. Experimental works with hafnium compounds are included into the work plan. In addition the work plan assumes investigation of heterogeneous plutonium compositions with neutron absorbers. The necessity of such works also follows from Phase 1 investigations with collaborators.

It is shown also that the technique developed under the Project provides more safe and compact long-term plutonium storage as compared to other well-known techniques under relatively simple measures on monitoring, account and control. Preserved materials after appropriate reprocessing may be used in fuel elements of nuclear-power plants.

As a result of Phase implementation an efficiency of cooperation of two participating in this Project institutions, VNIIEF and VNIINM, has been verified and the schedule of the Project Phase II has been prepared.

Phase II Project Summary

In the proposed technique plutonium or uranium is first transferred into the state of powdered oxides (PuO2, UO2), then mixed with oxides or other compounds of materials effectively absorbing neutrons within a wide energy range (from thermal to several MeV). The mixtures are pressed and annealed in a furnace at temperatures securing production of ceramic or vitrified granules. At a certain weight fraction of absorbers their mixture with Pu02 is free of critical mass. Various composite material compaction techniques are feasible. The laboratory study of some of them is the objective of this Project. Geterogeneous plutonium-absorber system options are also possible.

The theoretical and computational works provided for by the Project include:

- Development of requirements for plutonium and neutron absorber base composite material with due regard for the first experimental results (on the homogeneity degree, stationary storage conditions, behavior in an emergency).

- Computations of criticity parameters of produced test compositions.

- Studying various plutonium storage scenarios. Estimations and computations of parameters characterizing storage (thermal, radiation conditions).

- Feasibility Study of critical-mass-free storage of plutonium in the form of a geterogeneous plutonium-neutron absorber system.

The compact material manufacture techniques under study involve:

- production of compact samples of powders with conventional ceramic production methods: cold pressing, vibration compaction, compression and sintering;

- production of homogeneous moulding mass with subsequent hardening (cementing, bituminizing) or annealing with conditioning into clay.

For the neutron absorber compounds of lithium enriched in 6Li isotope up to 90% and natural isotopic composition hafnium compounds are mainly used.

It is suggested that 5 to 7 makeups of compositions should be produced and studied, f disassembled munitions.

When using the suggested technique, in one surface or underground (e.g., in a deep H = 300 m underground borehole) compact storage facility 10-50 tons of Pu can be contained provided a relatively simple complex of monitoring, accounting and control measures are taken. Presence of additional physical and chemical barriers secures a higher safety in terms of theft and ill-intentioned unathorized utilization, precludes clandestine rapid plutonium utilization for military purposes by a state controlling the storage facility, but do not in principle rule out the possibility of plutonium retrieval and utilization in the future for energetics or other purposes common to all mankind.

The Project involves experts of two institutes: VNIIEF and VNIINM.

At both the institutes the works will involve experts who have gained extensive experience of plutonium handling. It is suggested that the experience of works on reactor fuel production accumulated at VNIINM, as well as the neutron computation techniques and needed data available at VNIIEF should be used. The work under the Project will be carried out by high-level nuclear weapons experts.

Expected Results:

The Project implementation will result in development of a laboratory technology for production of several composite materials containing plutonium and neutron absorbers. The composition makeup (the plutonium-absorber ratio) will secure absence of the chain reaction at any composition mass.

It is suggested that this Project should involve feasibility study for production of plutonium compositions in the form of plutonium dioxide with neutron absorbers, i.e. lithium and hafnium base compounds.


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