Introduction
In the framework of the Nuclear Security Summit in Washington, Hillary Clinton, the U.S. State Secretary, and Sergey Lavrov, the Russian Foreign Minister, signed the agreement on bilateral disposal of excess weapons-grade Plutonium (Pu). In accordance with this document, the destruction of Pu is one of the important achievements in nuclear disarmament. The US and Russia committed themselves to destruct 34 tons of this weapon material matter.

Another outcome of the meeting in Washington was that President Dmitry Medvedev announced the decision to close before the end of the year the last Russian reactor producing weapons-grade Plutonium in Zheleznogorsk.

However, destruction of the weapon grade Plutonium requires still a significant research over possible technical options and development of optimal strategy and technical means.

The International Science and Technology Center (ISTC) is one of the few organizations that addressed these difficult technical problems already in 1990’s and provided answers concerning possible options for weapon Pu disposition. Moreover, through the research and development projects in a broad international cooperative way, ISTC contributed well to establishing a common understanding of possible options for Pu disposition.

ISTC Activities
Above 90 ISTC projects have been funded since 1994 related to weapon Plutonium disposition ranging from Pu incineration in fast and thermal reactors, in High Temperature Gas Cooled Reactors (HTGR) to transmutation of Pu and other Minor Actinides in Accelerator Driven Systems (ADS). Different options for reprocessing, long-term storage and other solutions have been investigated. The total support for weapon Pu disposition and transmutation projects mounted up to $33M in Russia and $5M for projects in Kazakhstan.

The key institutes working on Pu-disposition and transmutation options were: Russian Research Center - Kurchatov Institute, Bochvar Institute (All-Russian Scientific Research Institute of Non-Organic Materials – VNIINM), Institute of Physics and Power Engineering – Obninsk (IPPE), All-Russia Science Research and Design Institute of Power Engineering Technology (VNIPIET), AtomEnergoProjekt (AEP), Research Institute of Atomic Reactors - NIIAR, Research and Design Institute of Power Engineering - NIKIET, Khlopin Radium Institute, All-Russian Research Institute of Theoretical Physics - VNIITF, All-Russian Research Institute of Experimental and Theoretical Physics - VNIIEF, Special Design Bureau of Machine Building - OKBM, GosAtomNadzor - GAN, Moscow Engineering Physics Institute – MEPhI and others.

Moreover, two dedicated ISTC Contact Expert Groups (CEG) have been established on order to coordinate international efforts in Pu disposition R&D. The ISTC projects are related to different aspects of Plutonium disposition: CEG – MOX (Mixed Oxide fuel) and CEG-P&T(Partitioning and Transmutation) 

The CEG-MOX coordinated 15 different ISTC projects that included about 100 experts involved in Pu-disposition activities. Those 100 experts represented more than 20 Russian institutes and Agencies as well as foreign organisations including the European Commission, US Department of Energy (DOE), Japan Atomic Energy Research Institute (JAERI), French Commissariat Energy Atomic (CEA), European Joint Research Centers, US national labs and others. 

There were three groups of ISTC projects related to Pu disposition: 

1. Strategy for Plutonium utilization.
Main Results:
a) specification and selection of the most realistic options of plutonium utilization balancing national and international constraints 
b) development of optimal Nuclear Fuel Cycle (NFC) in Russia including plutonium recirculation as MOX-fuel 
c) Detail analysis of all stages of the NFC with Pu-recirculation, including assessments of economics, transportation, storage, environmental safety and non-proliferation aspects, demonstration of feasibility of weapons and civil plutonium utilization in Russia. 

Three possible scenarios of reducing the stocks of weapons and civil plutonium were developed: successive,parallel and combinedutilization ofweapons and civil plutoniumin thermal and fast reactors.

2. Physics and Nuclear Safety of Pu-disposition.

Main Results:
a) Analysis of nuclear safety parameters, data and modeling of plutonium-fuelled reactors; 
b) Experiments on critical facilities in Russia aiming to justify use of MOX fuel at the Russian VVER-type reactors.

3. Fuel Technology.

Main Results:
a) Development of technology of Plutonium-content fuel production: MOX, ROX, vibro-packed, dispersion-type, oxides, carbides, nitrides, inert-matrix, etc. 


The CEG-P&T coordinated a large number of projects related to new options of a closed Nuclear Fuel Cycle with Plutonium or/and Minor Actinides transmutation (disposition) using novel concept of accelerator-driven sub-critical blankets (ADS) instead of regular reactors.

Results of Projects: 
Principal components of ADS-based Plutonium burners were analysed, such as accelerator (linear, cyclotron, proton, etc.), blanket (solid fuels, molten salts etc.), target (solid, liquid, heavy metals, windowed, windowless). A large set of measurements and evaluations of nuclear data were carried out leading to upgraded, better quality nuclear data libraries made available to the international community. 

Large-scale demonstration stands and experiments were performed: Lead-Bismuth target complex of IPPE, Obninsk shipped to the University of Nevada, Las Vegas, YALINA subcritical experiment in Minsk-Sosny, molten salt loop at VNIITF, Snezhinsk investigating Pu containing molten-salt fuel for Pu-utilization, ASTRA facility at Kurvhatov Institute performing critical experiments for High Temperature Gas Cooled Reactor options. Finally, a series of important critical experiments at BFS-facility at IPPE, Obninsk, and in-reactor tests in NIIAR, Dimitrovgrad contributed to much better understanding of Pu as nuclear fuel. 


ISTC projects contributed to decommissioning of Pu-production reactors.
Main results:
a) Preparation of a general plan for decommissioning of BN-350 reactor in Kazakhstan including detail analysis of sodium coolant disposition;
b) Sodium disposition methods for BR-10 (IPPE, Obninsk);
c) Reactor graphite contamination and disposition concepts for Ozersk reactors. These results are equally valid for reactor in Zheleznogorsk.



ISTC in the Future:
Weapon grade Pu disposition requires R&D efforts conducted with international cooperation in order to ensure acceptable, cost-effective technological solutions and a transparent and verifiable process. Such technological solutions do not exist today. A broad international effort is required to fulfill the obligations of the US and Russia agreement on weapon Pu disposition. 

Concluding remarks
The international community faces important challenges when it comes to ensuring worldwide non-proliferation and the effective destruction of excess nuclear weapon materials. R&D is a significant component of such efforts. ISTC has proved to be an effective and transparent framework for these activities and an unique tool that builds internationally cooperative non-proliferation relationships. ISTC is well positioned to contribute this framework and its operational experience of 15 years toward the realization of the historic bilateral agreement signed in Washington.