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Gamze GENÇ*, Nesrin DEMİR, Gülşah ÖZIŞIK and Hüseyin YAPICI

LONG-LIVED FISSION PRODUCT TRANSMUTATION AND FISSILE BREEDING POTENTIALS OF A LEAD-BISMUTH EUTECTIC COOLED ACCELERATOR-DRIVEN SUB-CRITICAL SYSTEM. Gamze GENÇ*, Nesrin DEMİR, Gülşah ÖZIŞIK and Hüseyin YAPICI * Erciyes University, Faculty of Engineering,

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Gamze GENÇ*, Nesrin DEMİR, Gülşah ÖZIŞIK and Hüseyin YAPICI

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  1. LONG-LIVED FISSION PRODUCT TRANSMUTATION AND FISSILE BREEDING POTENTIALS OF A LEAD-BISMUTH EUTECTIC COOLED ACCELERATOR-DRIVEN SUB-CRITICAL SYSTEM Gamze GENÇ*, Nesrin DEMİR, Gülşah ÖZIŞIK and Hüseyin YAPICI * Erciyes University, Faculty of Engineering, Department of Mechanical EngineeringKAYSERİ, TURKEY gamzegenc@erciyes.edu.tr The Fifth Eurasian Conference Nuclear Science and Its Application 14-17 October 2008, Ankara, TURKEY

  2. High Level Wastes Undesired high-level waste (HLW) that is the most environmental safety issue and it mainly includes: (1) Transuranic Elements ● Plutonium ● Minor Actinides (MAs: isotopes of Np, Am and Cm) (2) Long-lived fission products (LLFPs: 129I, 99Tc, 135Cs etc.) The Fifth Eurasian Conference Nuclear Science and Its Application 14-17 October 2008, Ankara, TURKEY

  3. High Level Wastes Most countries’ preferred option for isolation of nuclear waste from the public and the environment is to bury it underground in a deep geological repository. However, the solutions to this problem are still debatable both technically and ethically because of their very long half lives (thousands of years to millions of years). Therefore, in the recent years, an alternative innovative approach is to burn and/or transmute HLW by using high-energetic neutron source. In order to transmute efficiently HLW, the high intensity neutron source is needed, such as: fusion-driven transmuter (FDT) and accelerator-driven system (ADS). The Fifth Eurasian Conference Nuclear Science and Its Application 14-17 October 2008, Ankara, TURKEY

  4. Accelerator Driven Systems The ADS is a subcritical reactor driven by an external neutron source and an ADS is a hybrid system which mainly consists of three parts: • proton accelerator, • spallation neutron target (SNT) • sub-critical fuel region (often called blanket) which surrounds the SNT. A high intensity continuous wave proton beam with an energy of around 1 GeV and a current of several tens milliamperes is injected into a target of heavy metal. This results in a spallation reaction that a few tens of emits neutrons per incident proton and sub-critical fuel region is driven by these spallation neutrons to induce further nuclear reactions. The Fifth Eurasian Conference Nuclear Science and Its Application 14-17 October 2008, Ankara, TURKEY

  5. The purpose of thisstudy Investigation of the high-level waste (HLW) transmutation and fissile breeding potentials of a lead-bismuth eutectic (LBE) cooled accelerator-driven system (ADS) under sub-critical condition. The long-lived fission products (LLFPs: 99Tc, 129I and 135Cs nuclides) and the uranium mono carbide (UC) ceramic fuel are the HLW and the fissile fuel, respectively. The Fifth Eurasian Conference Nuclear Science and Its Application 14-17 October 2008, Ankara, TURKEY

  6. i) The spallation neutron target (SNT): Lead (Pb)-bismuth (Bi) eutectic (LBE, 44.5% Pb + 55.5% Bi) is selected.ii) The sub-critical core: This zone contains the UC ceramic fuel rods cladded with silicon carbide composite (SiC/SiC) and cooled with the LBE. The fissile fuel can be bred via fertile-fissile reactions, as well as the fission energy production. At the same time, the spallation neutrons are multiplied by fission reactions. iii) The transmutation zone: This zone having a radial thickness of 10 cm is filled heavy water (D2O), and the LLFP rods cladded with carbon/carbon composite (C/C) are located in this D2O liquid as hexagonal arrays having a constant pitch length of 1.5 cm. This D2O would supply a more effective transmutation of the LLFP nuclides by thermalizing neutrons entering this zone. iv) The reflector zone: This zone is made of graphite (carbon) ADS DESIGN The Fifth Eurasian Conference Nuclear Science and Its Application 14-17 October 2008, Ankara, TURKEY

  7. MODELLING • It is assumed that a radially uniform proton source of 1000 MeV impacts on the target material with a source radius of 1 cm. • In order to investigate the effects of the fuel volume fraction (VFF) and fissile fraction (FF) on the transmutation and fissile breeding potentials, the analyses have been performed individually for various VFFs (10, 12, 15 and 20%) and for different FFs (10 to 24% by stepping 2%). • The ADS facilities are designed to keep the effective neutron multiplication factor (keff) much lower than unity during all operating conditions (keff < 1.0). The Fifth Eurasian Conference Nuclear Science and Its Application 14-17 October 2008, Ankara, TURKEY

  8. CALCULATIONAL METHOD • The neutronic calculations have been performed per the incident proton (1000 MeV) with the high-energy Monte Carlo code MCNPX in coupled neutron and proton mode using the LA150 library. • LA150 library consists of evaluated reaction cross sections and emission spectra up to 150 MeV for incident neutrons and protons, for over 40 target isotopes important in spallation targets, structural materials, and shielding. • The intranuclear cascade of spallation reactions is simulated using Bertini INC model. The Fifth Eurasian Conference Nuclear Science and Its Application 14-17 October 2008, Ankara, TURKEY

  9. NUMERICAL RESULTS The Fifth Eurasian Conference Nuclear Science and Its Application 14-17 October 2008, Ankara, TURKEY

  10. The number of produced neutrons (PN) can be determined by summing number of captured neutrons (CN) and number of leaking neutrons (LN). Furthermore, the leakage to production ratio (LPR) is defined as the ratio of the LN to the PN. The Fifth Eurasian Conference Nuclear Science and Its Application 14-17 October 2008, Ankara, TURKEY

  11. ENERGY GAIN In an ADS, one of the main parameters is the energy amplification, called also as energy gain (G). The Fifth Eurasian Conference Nuclear Science and Its Application 14-17 October 2008, Ankara, TURKEY

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  14. The Fifth Eurasian Conference Nuclear Science and Its Application 14-17 October 2008, Ankara, TURKEY

  15. CONCLUSIONS • The transmutation and fissile breeding potentials of the cylindrical ADS have been investigated. • The main conclusions derived from these analyses : • The PN can reaches 1044 n/p in the case of VFF = 10% and FF = 24%. • The energy gain can obtained as 74.5 in the case of VFF = 10% and FF = 23%. • The fissile breeding density (RCD values of 238U) can be increased approximate ten times by increasing the FF (from 10 to 24%). • The transmutation densities of the LLFP nuclides increase in a considerable ratio with the FF. • Consequently, the investigated ADS has a high neutronic performance from the LLFP transmutation and fissile breeding points of view. The Fifth Eurasian Conference Nuclear Science and Its Application 14-17 October 2008, Ankara, TURKEY

  16. THANK YOU ERCIYES UNIVERSITY KAYSERİ, TURKEY The Fifth Eurasian Conference Nuclear Science and Its Application 14-17 October 2008, Ankara, TURKEY

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