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Processing of Weapon Plutonium into MOX-fuel

#2092


Processing Compact Weapon Plutonium into MOX-fuel by Anhydrous (Thermochemical and Thermoelectrochemical) Methods for Thermal and Fast Reactors

Tech Area / Field

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

Status
3 Approved without Funding

Registration date
02.02.2001

Leading Institute
VNIIKhT (Chemical Technology), Russia, Moscow

Supporting institutes

  • NIIAR (Atomic Reactors), Russia, Ulianovsk reg., Dimitrovgrad\nVNIITF, Russia, Chelyabinsk reg., Snezhinsk

Collaborators

  • British Nuclear Fuels Ltd (BNFL), UK, Chesire, Risley Warrington\nPacific Northwest National Laboratory, USA, WA, Richland\nArgonne National Laboratory (ANL) / West, USA, ID, Idaho Falls\nBelgonucléaire, Belgium, Brussels

Project summary

In accordance with reduction of nuclear arms the significant amount of redundant plutonium has been formed. The occurrence of surplus weapon plutonium puts problems of both ecological and political character, as it is directly bound up with a non-proliferation of nuclear weapons. According to the Concept of the use of plutonium of a former military origin, a part of it should be proclaimed as "excesses" and utilized under the international control. From the point of view of Russia it seems a most rational to utilize surplus plutonium as fuel for nuclear reactors. Inevitably, arises a problem of proper choice and development of technology for process plutonium parts of nuclear charges into fuel. For today in world practice there are no ready-made techniques for industrial reprocess metal plutonium into compounds suitable for manufacturing of nuclear fuel.

Reprocess plutonium is possible by so called "aqueous" methods that are well developed at combines-producers of plutonium: dissolution of metal plutonium in acids (mixtures HNO3/HF or HNO3/HCOOH or HCl) followed by refining of a nitrate solution. Using the refined nitrate it is possible to receive PuO2: through oxalate precipitation, or through ammonium precipitation of mixed oxide (U, Pu)O2, or by plasma de-nitration.

Difficulties in practical realization of "aqueous" methods includes providing processes of dissolution of relatively big quantities of plutonium (few kilograms) with chemical and nuclear safety. The high aggressiveness of solutions put strict restrictions on construction materials. The main problem of aqueous technologies was and still is a formation of huge amounts of high-toxic radioactive waste.

Much more progressive methods of processing metal plutonium into compounds suitable for manufacturing of fuel for nuclear reactors are "non-aqueous" – thermochemical technologies. Together with high effectiveness of production they have the minimum negative influence upon the environment. During thermochemical process plutonium it is generated thousand times less radioactive waste as compared with aqueous technologies. Thermochemical technologies are more transparent from the point of view of control over irrevocability of dismantling of exuberant nuclear charges and control over non-distribution of nuclear arms.

The goal of the project is development the technology of reprocessing weapon-grade plutonium using thermochemical (non-aqueous) methods into fuel for nuclear reactors.

The essence of thermochemical methods is obtaining different compounds in non-aqueous mediums under conditions of high temperatures. As applied to obtaining plutonium compounds the interest to the development of thermochemical methods has considerably increased during the last years because of the necessity of irrevocable conversion of significant amounts of exuberant weapon plutonium and in connection with the worsened ecological situation around plutonium productions.

The greatest progress in this field is reached in USA, where in national labs LANL and LLNL – within the frame of the state program АRIЕS – the developmental industrial technology is designed and the equipment for conversion of plutonium through hydride into dioxide of plutonium is created. The examinations of properties and suitability of dioxide of plutonium for manufacturing of MOX - fuel are conducted.

In 1995 in VNIITF together with the specialists from ARRICT (Moscow) with financial support of ISTC (project №017-94) the experiments on conversion of metal plutonium into different compounds started. The metal plutonium (dozens of grams) was refined into plutonium dioxide (also through hydride) and then into plutonium trifluoride – a fuel additive for a molten salt nuclear reactor. The results of these operations are partially published, some processes were recognized original and are protected by the patents of Russian Federation. Specialists of VNIITF have long-term practical experience of operations with different compounds of uranium and plutonium. Specialists of ARRICT have large technological experience in the field of thermochemical synthesis of oxides, fluorides and other compounds of different elements and in creating equipment for such technologies.

Approximately in the same time in SSC NIIAR (Dimitrovgrad) the examinations for substantiation of the opportunity of conversion of metal plutonium into reactor fuel by thermoelectrochemical method started. SSC NIIAR takes a leading position in the world on making technologies of electrochemical regeneration of spent fuel and production of fuel composits on the basis of oxides of uranium and plutonium by electrolysis of saline systems.

Now there is no industrial production of РuO2 by thermochemical methods in any country of the world. However similar examinations are conducted in USA, France, Japan and in some other countries.

There are various approaches to processing metal weapon plutonium: the processes of hydrogenation, nitration, oxidizing and thermohydrolysis will be used.

As a result of realization of the project the following technological problems will be resolved:

– The technology and equipment for process metal weapon plutonium into dioxide of plutonium by thermochemical methods are designed.

– The optimal technological plan of synthesis of РuO2 meeting the demands of its usage in MOX-fuel is retrieved.

– The purification processes of plutonium (dioxide of plutonium) from undesirable for MOX-fuel waste elements, first of all from gallium a thermoelectrochemical method.

– For РuO2 powders obtained from weapon plutonium on non-aqueous technology the conditions of pressing and sintering will be retrieved while obtaining MOX-fuel from them. The physical-mechanical characteristics of powders РuO2 and UO2 are studied.

– The batches of MOX-fuel for reactor trials with usage of samples of PuO2 obtained from weapon plutonium on thermochemical technology, are prepared.

– Samples of РuO2 from an alloy of weapon plutonium by thermoelectrochemical method are prepared.

– The project-technical documentation on modular facility – a prototype of the industrial one on process plutonium by thermochemical method is designed.

– The system of registration and control of a motion of nuclear materials during the process plutonium is worked out.

– The initial data about technical-economical substantiation of industrial development of thermochemical technologies are prepared for specialized organization (SSPI, Moscow).

On the whole the realization of the project will be an important landmark on the way of rational usage of weapon plutonium in the peace purposes with minimum negative influence on environment.

Within the bounds of the project it is supposed to work out two "non-aqueous" ways of process plutonium into reactor fuel:

– thermoelectrochemical – dissolution of metal plutonium in a melt of chlorides (NaСl+КСl) with the following precipitation crystallization of РuО2 in one electrolytic cell;


– thermochemical – hydrogenation of metal plutonium with the following oxidizing up to РuO2 in one reactive vessel.

The improvement of a thermoelectrochemical method of process plutonium into dioxide of plutonium and examination of its suitability for manufacturing of MOX-fuel will run in SSC NIIAR. There will be also manufactured experimental TVEL and experimental FA for reactor trials from dioxide of plutonium received by thermochemical (VNIITF) and thermoelectrochemical (NIIAR) methods.

In RFNC-VNIITF the thermochemical method of obtaining dioxide of plutonium is completed, its characteristics and suitability for manufacturing of MOX-fuel are explored.

ARRICT will carry out scientific-methodical accompaniment of process plutonium through hydride, of technology of manufacturing of cores of TVEL from MOX-fuel, and also will elaborate equipment for thermochemical process plutonium.

The project "Process weapon plutonium by non-aqueous methods into MOX-fuel" will meet ISTC goals and objectives, because:

– its realization will give scientific employees and engineers on manufacturing nuclear weapon from VNIITF (Chelyabinsk-70), NIIAR and ARRICT a unique opportunity to redirect their abilities to conversion activity in the field of obtaining MOX-fuel;


– the former unique military experimental facilities for examination of plutonium and uranium will be redirected to conversion activity;
– the realization of the project could gradually develop into the long-term large-scale international project, that would lead to the integration of Russian scientists to the international scientific community.


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