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USE OF VVER SPENT FUELS IN A THORIUM FAST BREEDER P. Vértes, KFKI Atomic Energy Research Institute, Budapest, Hungary 17 th AER Symposium Yalta, 24-28 September, 2007

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The BN800 reactor Cylinder, halved vertical cross section 1 - zone of core with low Pu content (24.4%) 2 - zone of core with median Pu content (27.3%) 3 - zone of core with high Pu content (32.9%) 4 - radial breeding blanket 5 - axial breeding blanket 6 - reflector

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Thorium fast breeder reactor model Thorium fast breeder reactor model (Based on BN800 fast reactor) Core: Th+Pu+(uranium)=11228.5 kg Core: Th+Pu+(uranium)=11228.5 kg Axial breeding blankets: Th=9351.8 kg (4675.9 kg in the 3rd case) Axial breeding blankets: Th=9351.8 kg (4675.9 kg in the 3rd case) Radial breeding blanket: Th=25682.2 kg Radial breeding blanket: Th=25682.2 kg The heavy metal in the core is consisted of The heavy metal in the core is consisted of –Pu+MA as come from a 39.6 MWday/kg burned and 3 years cooled VVER-440 assembly –uranium (U232, U233, U234, U235) breeded in earlier cycles either in the core or in the blankets –thorium The Pu+MA component is distributed among the zone of core as 0.288, 0.323 and 0.389

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Condition of operation Power: 2100MWth, Power: 2100MWth, Burnup cycle: 165 days Burnup cycle: 165 days A burnup cycle is divided up to 10 burnup steps A burnup cycle is divided up to 10 burnup steps The initial composition of each B.C is chosen that the keff only after the last burnup step becomes less than 1 The initial composition of each B.C is chosen that the keff only after the last burnup step becomes less than 1 The irradiated thorium is cooled 165 days (to let the Pa decay to uranium) The irradiated thorium is cooled 165 days (to let the Pa decay to uranium) Uranium isotopes are extracted from blankets and are placed into the core together with new Pu+MA fuels and the cycle starts again. Uranium isotopes are extracted from blankets and are placed into the core together with new Pu+MA fuels and the cycle starts again.

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Case 1: Thorium blankets are on both axial sides, reactor is cooled with sodium No Pu+MA required after 11 th cycle! After 15 cycles: Total amount of Pu+MA required: 10311 kg Total amount of Pu+MA required: 10311 kg Total amount of Pu+MA left: 8480 kg Total amount of Pu+MA left: 8480 kg Total number of spent VVER assembly: 7389 Total number of spent VVER assembly: 7389 Total amount of required Thorium: 54962 kg Total amount of required Thorium: 54962 kg Amount of spared: 127kg Amount of spared: 127kg

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Case 2: Pb-Bi coolant No Pu+MA required after 10 th cycle After 15 cycles: Total amount of Pu+MA: 10311.1 kg Total amount of Pu+MA: 10311.1 kg Total amount of Pu+MA left: 8340 kg Total amount of Pu+MA left: 8340 kg Total number of spent VVER assembly: 7389 Total number of spent VVER assembly: 7389 Total amount of required Thorium: 54962 kg Total amount of required Thorium: 54962 kg Amount of spared: 243kg Amount of spared: 243kg

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Case 3: Axial thorium blanket are only bottom, reactor is cooled with sodium After 43 cycles: Total amount of Pu+MA: 27682 kg, Total amount of Pu+MA: 27682 kg, Total amount of Pu+MA left: 25200 kg Total amount of Pu+MA left: 25200 kg Total number of spent VVER assembly: 19917 Total number of spent VVER assembly: 19917 Total amount of required Thorium: 52399.5 kg Total amount of required Thorium: 52399.5 kg Amount of spared: 0kg Amount of spared: 0kg

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Proliferation problem About 80% U-233 and U-235 in the rest uranium About 80% U-233 and U-235 in the rest uranium About 20 kg critical mass About 20 kg critical mass 6 A-bomb in the 1 st case, 12 A-bomb in the 2 nd case 6 A-bomb in the 1 st case, 12 A-bomb in the 2 nd case Th-fast breeder fleet is not an acceptable solution for countries signed the non-proliferation treaty Th-fast breeder fleet is not an acceptable solution for countries signed the non-proliferation treaty Other countries may use this solution and may fabricate fuels mixing the breeded uranium with the depleted one Other countries may use this solution and may fabricate fuels mixing the breeded uranium with the depleted one

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Method of calculation The NOTRADAT system: NJOY ⇨BBC⇨TRANSX ⇩ ⇖ DANTSYS⇨TIBSO

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The special features of NOTRADAT system ► nuclear data: each isotope in separate file having standardized name ► NJOY processing in batch: generic input is used ► TRANSX: composition data may be separated from other control input items ► Total power can be calculated not only fission power ► Flux, calculated by DANTSYS multigroup SN code normed to required power and used for burnup calculation by TIBSO code ► Fuel manipulation can be accomplished by means of TIBSO ► New material composition obtained from burnup and possibly from fuel manipulation can be directly used in TRANSX due to an output option of TIBSO ► Burnup libraries which may differ in different part of reactor zone can be modified after each burnup cycle In our calculations a 30 group system has been used

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References [1] Dekusar V.M., et. al., Feasibility Studies of BN-800 Type Reactor with (Pu- Th)O2 Fuel for Effective Incineration of Minor Actinides, Technical Meeting of the CRP on «Studies of Advanced Reactor Technology Options for Effective Incineration of Radioactive Waste, 22-26 November 2004, Hefei, China [2] P. Vertes, NOTRADAT – a program package for neutronic calculations of nuclear systems, unpublished [3] R. E. MacFarlane, D.W. Muir, NJOY Nuclear Data Processing System, LA- 12740, 1994 [4] R. E. MacFarlane, TRANSX 2: A Code for Interfacing MATXS Cross- Section Libraries to Nuclear Transport Codes, LA-12312-MS (July 1992) [5] R. E. Alcouffe, R. S. Baker, F.W. Brinkley, D.R. Marr, R. D. O’Dell, and W. F. Walters, “DANTSYS: A Diffusion Accelerated Neutral Particle Transport Code System,” LA-12969-M (June 1995) [6] Vértes P. Multinodal treatment of production, decay and spreading of radioactive isotopes, Nuclear Technology 1999;128:124-130.

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Thank You

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