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Status of MOX Fuel Fabrication, Utilization, XA0201760 Design and Performance in Lwrs

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Status of MOX Fuel Fabrication, Utilization, XA0201760 Design and Performance in Lwrs Status of MOX fuel fabrication, utilization, XA0201760 design and performance in LWRs V. Onoufriev International Atomic Energy Agency, Vienna Abstract. The overview looks at the present status of Pu recycle as MOX fuel in thermal power reactors as presented mainly at the IAEA Symposium on MOX Fuel Cycle Technologies for Medium and Long Term Deployment held in Vienna in May 1999, and some other international meetings. Present status in MOX fuel fabrication, performance and utilization technologies are discussed. Recycling of plutonium as MOX fuel in LWRs has become a mature industry. The technology is well understood and the facilities, institutions and procedures are in place (capacity extensions being planned) to meet the anticipated arisings of separated plutonium from the production of nuclear power. MOX fuel performance and its modelling are discussed in comparison with those of UO2 fuel. 1. INTRODUCTION Today the plutonium recycling with LWRs has evolved to industrial level in some countries relying on the recycling policy. This happened mainly because of the worldwide delays in development of fast reactor's programmes. More than 30 years of reactor experience using MOX fuel as well as the fabrication of 2 000 MOX assemblies with the use of 85 t of Pu separated from spent fuel from power reactors and good performance records indicate now that the recycling of plutonium as MOX fuel in LWRs has become a mature industry. The technology is well understood and the facilities, institutions and procedures are in place to meet the anticipated arisings of separated plutonium from the production of nuclear power. The number of countries engaged on plutonium recycling could be increasing in the near future, aiming the reduction of stockpiles of separated plutonium from earlier and existing reprocessing contracts. Economic and strategic considerations being the main factors on which to base such decision to use MOX. The reactor-based weapons-grade plutonium disposition approaches proposed by the US and Russia are build upon proven commercial MOX fuel technologies and may further contribute to optimization of Pu recycling technologies. An International Symposium on MOX Fuel Cycle Technologies for Medium and Long Term Deployment, organized by the IAEA in co-operaton with OECD/NEA and held in Vienna in May 1999, was a milestone to look in past, present and future of Pu recycling in nuclear power reactors [2]. 2. MOX FUEL FABRICATION Currently, six plants for MOX fuel fabrication are in operation in Belgium, France, Japan, UK and India (see Table I, [1]). Worldwide MOX fuel fabrication capacity at the end of 1998 amounts about 220 tHM per year. In the UK, a large scale MOX fabrication plant (SMP) has been constructed and is awaiting consent to start operation. In Russia, the first pilot plant (with a capacity of 101 HM/y) for fabricating MOX fuel is under construction inside the RT-1 plant. A new MOX plant (Complex 300) is planned to commence operation in 2010 [3,4]. There are plans for the construction of a new MOX plant in Japan and of a demonstration facility in China. The available MOX fabrication capacities worldwide are projected to be over 600 tHM/y in the coming decade owing to deployment of new facilities and expansion of capacities of existing facilities, where it is anticipated that some 25 to 30 t of plutonium will be recycled per/year. 155 Fuel fabrication records as of 31 December 1998 for LWRs and FBRs [5] have shown that more than 550,000 LWR fuel rods for more than 3 300 fuel assemblies were produced in facilities outside the United States [5]. FBR MOX production totals about 680 000 rods for more than 3 900 assemblies [5]. TABLE I. MOX fuel fabrication capacity (tHM/y), as of end 1998 [1] Country Site Plant 1998 2000 2005 2010 Belgium Dessel P0 35 40 40 40 France Cadarache CFC 35 40 40 40 Marcoule MELOX 120 200a 200a 250a India Tarapur AFFF 5 10 10 10 Japan Tokai PFPF 15b 15b 5C 5C Rokkasho- MOX FFF - - 100 100 mura Russian Fed. Chelyabinsk inside RT-1 - - 10 10 Chelyabinsk Mayak, Complex 300 40 UK Sellafield MDF 8 8 8 8 Sellafield SMP - 120 120 120 Total 218 433 533 623 a date not fixed. b forATRFugenandFBRMonju. c forFBRMonju. As MOX fabrication has progressed from its initial stages several process improvements have been made, especially in the area of powder production. The objectives of these improvements included producing a powder product with improved characteristics for pelletizing and improved fuel performance, especially related to fission gas release. [6-10]. Reduction of the size of Pu agglomerates is an important task in powder technology optimization^, 11-13]. Enlargement of UO2 grain size and diminishing Pu/U diffusion coefficients might be obtained through the use of small quantities (500-2000 ppm) of oxide (Ti, Cr and some others) additives [10,12]. Process improvements have also been made with respect to reducing powder dispersion, thereby improving hold-up and personnel radiation protection [5, 11, 12]. Waste handling and scrap recycle have also been improved [5, 10, 11]. These are both important with respect to cost and safeguards. Several aqueous [14, 15] and pyrochemical [16] processes of conversion of weapons-grade plutonium to MOX are under investigation in Russia. Ammonium co-precipitation of Pu and U with parallel involvement of surface active substances (SAS) is identified as the most promising (GRANAT, Combine "Majak"). A pyrochemical technology of the conversion of metallic Pu into MOX FBR fuel in molten salts has been developed in NIAR, Dimitrovgrad [16]. Vibro-pack method is used instead of pelletizing process. The letter is under development now to fabricate MOX fuel rods for WWER reactors. IAEA/EURATOM safeguards monitoring in MOX fabrication facilities is well organized [5, 17-19]. An unattended NDA measurement system recently deployed at Belgonucleaire was described and the savings in cost and personnel time resulting from use of the system were presented. The IAEA's Tank Monitoring System (TAMS) and the benefits of its use with respect to timely (every 15 seconds) and accurate data collection was noticed. The safeguards 156 will be strengthened with the enforcement of the IAEA's 93+2 Programme, resulting in additional constraints. 3. MOX FUEL UTILIZATION Today, more than 30 thermal reactors have used MOX-fuel complying with a partial core loading pattern [20]. The main part of the NPP using MOX are 33 PWRs (19 in France [12], 9 in Germany, 2 in Belgium and 3 in Switzerland), but 2 BWRs use also MOX (in Germany). Table 2 lists the current status of MOX fuel utilization in thermal reactors worldwide. The commercial application of MOX fuel in LWRs has been started in the mid 1980s when some modification or withdrawal of fast reactor programmes was enforced. The developed technologies of recycling and fuel fabrication were applied for Pu-recycling in LWR fuel, in the mean time focusing on stabilisation of the separated plutonium inventory. Currently, the use of MOX fuel has been established on an industrial scale in a number of countries. In Belgium, France, Germany, Japan and Switzerland, a considerable number of thermal power reactors (PWRs and BWRs) are either licensed (i.e. 40, of which 34 have MOX fuel loaded) or have applied for a license (about 13) to use MOX fuel at levels of up to 30% of the reactor core. Up to now, more than 2000 FAs have been loaded in LWRs in Europe [20, 21]. In France, since 1987 about 1200 MOX assemblies have been loaded in 19 PWRs (900 MWe - 17x17), and about 600 FAs achieved 3 cycles, and a few FAs were authorized for 4 and 5 cycles for experimental purposes [12]. In Germany, since 1985, about 800 MOX FAs have been loaded in 9 PWRs (16x16 and 18x18) and 2 BWRs : Gundremmingen B and C (1344 MWe-9x9). In Switzerland, about 160 MOX FAs have been loaded in PWRs : since 1978 in Beznau 1 and 2 (PWR 350MWe - 14x14) and recently in Gosgen (PWR lOOOMWe - 15x15). In Belgium, since 1995 about 70 MOX FAs have been loaded in Doel 3 and Tihange 2 (PWR lOOOMWe - 17x17). Loading of MOX FAs are postponed in Japan after falsification of MOX pellets by BNFL. Experience with MOX reloads in BWRs and PWRs from 1981 to 1988 is given in Table 3 [20,21]. TABLE II. Present Status of large scale MOX fuel utilisation in thermal reactorsa Number ofThermal Reactors Operating Licensed to use Loaded with Applied for reactors MOX FAs MOX FAs MOX license Belgium 7 2 2 France 57 20 19 8b Germany 19 12 11 4 Japan 52 3 1 1 Switzerland 5 3 3 Total 130 40 36 13 a There are a number of reactors, notably in Europe and India, not included in this Table, which are licensed to use MOX fuel on an experimental basis; b Technically capable reactors planned to be licensed. Highest MOX fuel burnup (42-60 MWd/kg HM) was reached in Switzerland, Beznau 1 and 2 [20]. In Germany, mean MOX FA discharge exposure is about 40 GWd/t, maximum MOX FA exposure is about 48 GWd/t in commercial operation. The trend in this field is increasing and now many of the MOX FAs under irradiation will reach mean discharge exposure around 48 GWd/t. In France, the average burnup rate per MOX reload is maintained at around 157 37 MWd/kg HM and the maximum assembly burn-up rate at 41 MWd/kg HM, compared with the 50 MWd/kg HM reached by UO2 assemblies obtained in annual cycle (3 cycles for MOX and 4 cycles for UO2).
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