17%
12.5%
30 000 ppm
17.6 W/kg PuO2
G. Lebastard
President and Chief Executive Officer
COMMOX
Director International Business Reprocessing Branch
COGEMA
2 et 4 rue Paul Dautier
78140 - Velisy Villacoublay
V: 33 01 39 26 30
00 20814
J.C. GUAIS
Vice-President
COGEMA, Inc.
7401,
Wisconsin Avenue
Bethesda, Maryland
USA
V: (301) 986 85 85
ABSTRACT
Increasing interest has been shown throughout the world in the management and disposition of excess weapons plutonium. Many alternative solutions have been proposed, and the U.S. Department of Energy has begun preparation of a Programmatic Environmental Impact the high energy value of fissionable material, this presentation addresses what we consider to be the most valuable and viable alternative - the use of plutonium from weapons in mixed uranium-plutonium oxide (MOX) fuel to generate electricity in existing operating Light Water Reactors (LWRs).
The arguments that support this conclusion are related to:
This unique, extensive experience could be made available to help develop an expeditious, cost effective disposition program for excess weapons-grade plutonium.
INTRODUCTION
The end of the cold war opened a new era and radically transformed the security environment facing the world. With the conclusion of the 1991 and 1993 START I and II treaties, USA and Russia committed themselves to reduce the size of their nuclear arsenal.
But, this unprecedented disarmament decision has to be complemented by measures forbidding the possibility of misusing excess weapons fissile materials, either enriched uranium or weapons-grade plutonium. In order to prevent proliferation of such materials, the international community undertook to find the most appropriate answer regarding highly enriched uranium and weapons-grade plutonium matters.
Concerning weapons-grade plutonium, a cogent political and technical agenda which consistently addresses the disposition of surplus weapons fissile materials has been set up by countries such as the USA, Russia and France.
Among the options which have been studied, the use of plutonium from weapons in mixed uranium-plutonium oxide (MOX) fuel to generate electricity in existing operating LWRs appears as the soundest and most complete solution.
Two major international events recently endorsed and promoted the MOX option as one of the two possible routes: the October 1, 1996 Draft issued by the US DOE and the October 28-31, 1996 Paris-based G7+Russia international expert meeting on management of excess weapons fissile material.
As a matter of fact, the MOX option fully answers to three essential key considerations: non-proliferation, control of inventories, and proven technology. This paper presents these three features and gives an outlook for future evolutions.
THE NON-PROLIFERATION FACTOR
Regarding, the non-proliferation aspect, using weapons-grade plutonium in LWRs offers a real advantage over vitrification. «Moxified» plutonium undergo an important isotopic degradation during its use in reactor.
When the MOX fuel is unloaded, the percentage of its fissile plutonium (Pu239) and its non-fissile material (Pu240 and 242) are such that the recovered material is far from having the requisite qualities for military devices.
Furthermore, the commercial fuel cycle gives all the guarantees of safety and materials protection. The plutonium - before its effective integration into MOX - is stored in a safe, permanently monitored by the site operator, under the supervision of the competent national and international authorities. As is the case with all the others commercial nuclear activities, French MOX fabrication plants are under the control of the appropriate national and international authorities in particular the IAEA and Euratom.
This statement is also valid for reactor utilization as well as for all associated logistic steps. The actual credentials of safeguards on Physical Protection of the MOX industry is the most convincing demonstration today.
THE INVENTORY CONTROL FACTOR
In generating electricity, any nuclear reactor using enriched uranium produces plutonium. Conversely, any "moxed" reactor consumes plutonium. Plutonium recycled into MOX fuel plays the same role as uranium 235 does in conventional fuel. A portion of this uranium is consumed during the nuclear reaction just as a portion of the plutonium in MOX fuel will have disappeared by the time the fuel is unloaded.
Let us illustrate this using the example of an installed nuclear generating capacity of 50,000MWe:
More accurately, whereas an enriched uranium reactor produces 250 kg of plutonium per year, a 30% MOX-loaded reactor produces none, and a 100% MOX reactor, that is a completely loaded MOX fuel reactor, burns approximately 60 kg of Pu per TWh generated. However, stabilizing plutonium production is only the beginning. Tomorrow, the system will be complete with the development of 50 or 100% MOX reactor offering the decisive advantage of burning more plutonium than it produces.
Today, the given the current state of technology, the 30% MOX reactor, exists and operates smoothly in many countries. In Europe, up to 20 reactors are loaded with MOX fuel and up to 50should be in the near future. In France, 10 reactors are loaded, 6 additional are licensed for this purpose and 12 additional reactors will be licensed by the turn of the century. In Germany, 7reactors are loaded, 10 reactors are licensed for the purpose, and 3 additional reactors will be licensed in the years to come. Switzerland and Belgium operate each 2 MOX-loaded reactors, and this number of MOX reactors will increase to 4 in Switzerland.
THE INDUSTRIAL FACTOR
MOX fuel is produced from a mixture of uranium and plutonium oxides and has been used in Europe for over twenty years. The MOX industrial manufacturing process uses techniques which have been tested and qualified in the COGEMA Cadarache plant, close to Aix en Provence in France. This is a really mature industry with proven reliability of operation and quality of products. The three plants whose production is managed by COMMOX (COGEMA Group) are :
COGEMA Cadarache, created in 1961, where nearly 30 tons of plutonium have already been recycled. The various stages of the process are: powder preparation, pressing, sintering, grinding, pellet inspection, pellet control, cladding and inspection of fuel rods.
To avoid any risk of contaminating the environment, the three barriers formed by the glove boxes, the hot cells and the containment building are maintained at progressively lower underpressures. A dedicated department is responsible for continuous quality assurance and product certification.
Today, COGEMA Cadarache is capable of an annual production of 40 tons of MOX fuel and 10 tons of fuel for fast-breeder reactors.
The need for high levels of industrial performance and the overriding concern to provide optimum staff working conditions have led to the choice of a largely automated control system for MELOX. A real time computer system keeps track of the products, monitors compliance with specifications and manages the nuclear material currently on the site.
The design of the MELOX plant, and its operation, are subject to extremely strict security requirements, in particular with respect to product confinement, fire and earthquake protection.
The fabrication process principles implemented in the MELOX plant are basically identical to those of UO2, and are therefore broadly experienced and qualified. However, handling and blending of the powders necessitate specific procedures, dry grinding (instead of wet grinding) of the fuel pellets, and enhanced controls.
In addition, MOX fuels must be suited for in-reactor performance, thus its fabrication process involves micronizing and mixing the plutonium oxide with uranium oxide by means of the A-MIMAS (Advanced MIcronized MASter blend) fabrication process. This process, directly derived from the current process of Dessel and Cadarache, ensures isotopic homogeneity on large batches of fuel, and adequate pellet fabrication performance.
The powder-processing machinery is arranged around a central raw material distribution line, known as the Handling and Storage Tunnel. The «powder preparation» and «pelletizing» functions are connected to the tunnel. Products are transferred automatically with the appropriate confinement conditions.
320 pellets are fed into each rod. MELOX has today the capacity to produce 110 000 pellets per day, ie 350 rods, which is equivalent to a little more than one 500 kg fuel assembly per day. Melox characteristics are given below :
17%
12.5%
30 000 ppm
17.6 W/kg PuO2
About 10 tons of plutonium will have been processed in MELOX early 1997.
With the Cadarache and MELOX plants, French MOX industry has thus undoubtedly achieved its industrial maturity.
It should be noted that each one of these plants is or will be soon adapted to both PWR and BWR assemblies fabrication.
Record of operation of the fabrication plant is excellent : over 600 MOX fuel assemblies or about 300 tHM produced early 1997 to high quality standards, and deliveries in Western Europe and very soon in Japan.
One should note that today our existing experience covers about 60 tons of plutonium as PuO2. Difficult to argue that this reference is not directly applicable to weapons plutonium whose quantity are to the same order of magnitude.
THE WEAPONS-GRADE PLUTONIUM MOX FABRICATION OPTION: AN APPRAISAL
As previously underlined, moxification of weapons-grade plutonium proves to be technically mature. The unique, extensive European MOX experience could easily be made available to help develop an expeditious, cost effective disposition program for in- excess weapons-grade plutonium.
Although very analogous to civilian one, military plutonium differs from it essentially by its isotopic content, which is characterized by a higher proportion of Pu239 and a lower content of Pu240.
Regarding transposition from commercial plutonium to weapons plutonium, we
don't foresee any major difficulty either at the fabrication step or in-core.
For instance, at the MOX fabrication level, weapons-grade plutonium is easier to
handle than the reactor-grade plutonium already in use : specific thermal power
is 7 to 10 times less, radioactivity is also seriously reduced (
,
,
and neutrons).
However criticality considerations would lead to the need for some specific adaptations of the civilian MOX technology for example, smaller size equipment in the first part of the facility. This is not perceived as a difficulty. In fact the exact adaptation would depend on the form under which weapons plutonium is released to the commercial cycle.
Some aspects of the isotopic difference can be considered as drawbacks for core operation : such are the in-core lower yield of delayed neutrons, the increased initial assembly reactivity and the reduced boron and control rod worth. These features can easily be dealt with by optimizing loading pattern and boron concentration.
Besides the possibility of a prompt implementation, weapons plutonium disposition through MOX fuel demonstrates two additional advantages related to economics, and waste management.
The use of 50 tons of excess inventory plutonium in LWRs would yield a 350 billion kWh electricity production which is comparable to the French annual consumption. Available cost comparisons show that the money saved in this recycling scenario, compared to other alternatives, would range between $10 and $20 per gram plutonium.
This is not in opposition with the economic assessments of MOX fuel use in the civilian nuclear fuel cycle. The French utility's forecasts show not only the competitiveness of MOX fuel recycling but, as the burn-up grows, an actual contribution to the cost-effectiveness of the nuclear generated electricity compared to other sources.
Moreover, compared with other disposal alternatives, the overall generation of high level waste would be reduced significantly due to the decrease of initial quantities of plutonium by moxification.
On the other hand, the fuel cycle back-end industry, dealing with spent fuel, high level waste and plutonium, has clearly demonstrated its capacity to handle these materials with a high degree of safety and environmental protection. Impressive achievements concerning solid waste volume, activity releases and occupational exposure are now a matter of record.
The COGEMA Group is really prepared to support any MOX solution decision in USA or Russia for disposal of excess weapon material. If a few data were needed for confirmation, fabrication of several MOX rods with WPu would be feasible immediately and irradiation either in a French commercial reactor or an US test reactor would provide the necessary data within a very short time. Fabrication of Lead Test Assemblies for a demonstration program in the USA could also be implemented on a very short notice to allow loading in 1998. Fabrication in France of the first reloads for commercial reactors in the USA, for a quick start of this disposition program, would also be feasible to allow burning in US LWR reactors from 2000. Such a quick start program would be a very strong and clear demonstration of the political will to get rid of the former weapons materials and would allow an efficient support to similar and parallel decision in Russia. Such a quick start program would also leave time for preparing the decision on MOX fabrication on the larger term, either building a dedicated facility in the USA, which COGEMA can obviously support and contribute efficiently, or relying on overseas facilities.
CONCLUSION
Weapons-plutonium moxification in existing LWRs is the only disposition alternative taking full advantage first, of the huge energetic content of plutonium, and second of the outstanding experience available today in the civilian nuclear industry.
A substantial MOX program in the U.S., perhaps 10 large reactors using one-third MOX fuel reloads, could reduce the excess plutonium to zero within two decades. Thus, this option can begin destruction of weapons plutonium earlier, cost-effectively and in a more environmentally friendly way.
For reaching the overall objective of global disarmament such a decision for a significant share of the material to be disposed of would have an extremely important political consequence in terms of efficiency, as a very symmetric program for the option to be selected could be implemented in Russia about at the same time and with full international support.