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Transmutation of Long-lived Nuclear Wastes

June 1-6, 2014 ARIS2014. Transmutation of Long-lived Nuclear Wastes. Hiroyuki Oigawa Office of Strategic Planning (Nuclear Science and Engineering Directorate, and J-PARC Center) Japan Atomic Energy Agency. Background. Concern to radioactive waste management has been increasing in Japan.

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Transmutation of Long-lived Nuclear Wastes

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  1. June 1-6, 2014 ARIS2014 Transmutation of Long-lived Nuclear Wastes Hiroyuki Oigawa Officeof Strategic Planning (Nuclear Science and Engineering Directorate, and J-PARC Center) Japan Atomic Energy Agency

  2. Background • Concern to radioactive waste management has been increasing in Japan. •  Transmutation technology for long-lived nuclides is drawing the attention from public, media and politicians. • JAEA (former JAERI and PNC/JNC) has been studying this technology for more than 20 years. • The Ministry of Education, Culture, Sports Science and Technology (MEXT) in Japan has launched a Working Party to review Partitioning and Transmutation Technology in August, 2013, and issued an interim report in November, 2013.

  3. Major Long-lived Nuclides in Spent Nuclear Fuel Fission products (FP) Trans-uranic elements (TRU) Actinides Minor actinides (MA) Dose Coefficient: Committed dose (Sv) per unit intake (Bq), indicating the magnitude of influence of radioactivity to human body. α-activity is more influential than β,γ-activity.

  4. Partitioning and Transmutation (P&T) Spent fuel Reprocessing Recycle U、Pu Geological disposal (Glass waste form) FP、MA Conventional scheme P&T technology MA(Np, Am, Cm) Transmutation by ADS and/or FR PGM(Ru, Rh, Pd) Utilization and/or disposal Partitioning(Example) Geological disposal after cooling and/or utilization (Calcined waste form) Heat generator (Sr, Cs) Geological disposal (high-density glass waste form) Remaining elements MA: Minor Actinides FP: Fission Products PGM: Platinum Group Metal FR: Fast Reactor ADS: Accelerator Driven System

  5. Reduction of Radiological Toxicity by P&T Radiological Toxicity: Amountof radioactivity weighted by dose coefficient of each nuclide. • Normalized by 1t of spent fuel. • 9t of natural uranium (NU) is raw material of 1t of low-enriched uranium including daughter nuclides. Spent fuel (1t) High-level waste MA transmutation Natural uranium (9t) Radiological toxicity (Sv) • Time period to decay below the NU level: • Spent fuel 100,000y　　↓ • High-level waste 5,000y　　↓ • MA transmutation 300y Reduction Reduction Time after reprocessing (Year)

  6. Howto Transmute MA and LLFP Mo-102 (T1/2=11min.) Tc-102 (T1/2=5s) Ru-102 (stable) Example of fission reaction of MA β-ray β -ray Np-237 (T1/2=2.14M yr.) Fission reaction (n, f) Neutron Note: 10% or less of FPs are Long-lived ones. Fast neutrons (> 1MeV) High energy neutrons (> 10MeV) Neutron β -ray β -ray I-133 (T1/2=21hr.) Xe-133 (T1/2=5d) Cs-133 (stable) Thermal neutrons T1/2:Half life Example of (n, 2n) reaction of LLFP Example of capture reaction of LLFP Te-125 (stable) Sb-125 (T1/2=2.8yr.) Sn-125 (T1/2=9.6d) Sn-126 (T1/2=230k yr.) Xe-130 (stable) I-130 (T1/2=12hr.) I-129 (T1/2=15.7M yr.) Capture reaction (n, γ) (n, 2n) reaction Neutron Neutron Β-ray Β-ray Β-ray

  7. Cross Sections of Neutron-induced Reaction : Am-241 Total Scattering Capture Fission inelastic • Chain reactions of fission by fast neutrons are advantageous for transmutation of MA.

  8. Examples of “Reduced Half-life” “Reduced Half-life” can be written as T1/2 ＝ ln2 / (φ·σ ) , if there isno competitive reaction nor production reaction, where φ is neutron flux and σ is reaction cross section. Condition of realistic transmutation: φ·σ >1015(barn/cm2/s)

  9. Accelerator Driven System (ADS) for MA Transmutation Proton beam Max.30MW Super-conducting LINAC 100MW To accelerator 800MW 170MW Fission energy To grid Spallation target (LBE) 270MW MA: Minor Actinides LBE: Lead-Bismuth Eutectic Power generation Transmutation by ADS MA-fueled LBE-cooled subcritical core Utilizing chain reactions in subcritical state Proton Spallation target Fission neutrons Fast neutrons • Characteristics of ADS: • Chain reactions stop when the accelerator is turned off. • LBE is chemically stable. •  High safety can be expected. • High MA-bearing fuel can be used.MA from 10 LWRs can be transmuted. Short-lived or stable nuclides Long-lived nuclides (MA)

  10. ADS Proposed by JAEA • Proton beam : 1.5GeV • Spallation target : Pb-Bi • Coolant : Pb-Bi • Max. keff= 0.97 • Thermal output : 800MWt • MA initial inventory : 2.5t • Fuel composition : • (MA +Pu)Nitride + ZrN • Transmutation rate : • 10%MA / Year • 600EFPD, 1 batch Conceptual view of 800 MWth LBE-cooled ADS

  11. Components of Double-strata Fuel Cycle Concept U [752t/y] Pu [8t/y] Scope of P&T Partitioningprocess Fission Products (FP) [39t/y]Minor Actinides (MA) [1t/y] Reprocessing Spent fuel [800t/y] Dedicated transmutation fuel Fuel fabricationprocess Minor actinides (MA) Remaining elements PGM Sr-Cs [1t/y] [8t/y] [4t/y] [5t/y] AcceleratorDriven System(ADS) [30t/y] Transmutation cycle [7t/y] Optimization by utilization / Disposal after cooling Recovered actinides Spent fuel [1t/y] Reprocessing Fission products Final disposal [8t/y] PGM: Platinum Group Metal

  12. Technical Issues for ADS J-PARC: Japan Proton Accelerator Research Complex TEF-P: Transmutation Physics Experimental Facility TEF-T: ADS Target Test Facility SC-LINAC: Superconducting LINAC • Accelerator • R&D of SC-LINAC • Reliability Assessment • Construction and operation of J-PARC accelerator • R&D of Pb-Bi technology Construction of TEF-T in J-PARC • Structure • Spallation Target, Material • Operation of Pb-Bi system • Design study on reactor vessel, beam duct, quake-proof structure, etc. • Experiments in existing facilities and analyses Construction of TEF-P in J-PARC • Fuel • Fabrication, irradiation and reprocessing tests • Reactor Physics • Control of Subcritical System

  13. Reliability of Accelerator Number of beam trips per year (7,200 hours) • We are comparing the trip rate estimated from data of existing accelerators and the maximum acceptable trips to keep the integrity of the ADS components. • Short beam trip (<10s) can meet the criteria. • Longer beam trip should be decreased by: • Reducing the frequency of trips and • Reducing the beam trip duration Acceptable trip rate Beam trip rate (times/year) Estimation from experiences 0-10s 10s – 5min. >5min. Beam trip duration

  14. Design of Beam Window Temperature Outer surface Temperature Of beam window • Beam window is subjected to severe conditions: • High temperature • Corrosion and erosion by LBE • Pressure difference between vacuum and LBE (~0.8MPa) • Irradiation by protons and neutrons • Temperature at the outer surface of the window can be less than 500ºC. • Buckling failure can be avoided by a factor of safety (FS)=3. • The life time of the beam window should be evaluated from viewpoints of corrosion and irradiation.  necessity of irradiation data base.

  15. Accuracy of Neutronics Design Benchmark calculation for 800MWt ADS for BOC and EOC.(Left: Comparison between JENDL-4.0 and JENDL-3.3, Right: Nuclide-wise contribution for differences in k-eff) • There is 2% difference in k-eff between JENDL-4.0 and JENDL-3.2, which is too large to design ADS. necessity of integral validation of nuclear data

  16. Japan Proton Accelerator Research Complex:J-PARC Hadron Experimental Facility Jan. 28, 2008 50 GeV Synchrotron Materials and Life Science Experimental Facility To neutrino detector 3 GeV Synchrotron Site for Transmutation Experimental Facility LINAC

  17. Transmutation Experimental Facility (TEF) of J-PARC Transmutation Physics Experimental Facility: TEF-P ADS Target Test Facility：TEF-T Purpose: To investigate physics properties of subcritical reactor with low power, and to accumulate operation experiences of ADS. Licensing: Nuclear reactor: (Critical assembly) Proton beam: 400MeV-10W Thermal power: <500W Purpose: To research and develop a spallation target and related materials with high-power proton beam. Licensing: Particle accelerator Proton beam: 400MeV-250kW Target: Lead-Bismuth Eutectic (LBE, Pb-Bi) Multi-purpose Irradiation Area Critical Assembly 10W Pb-Bi Target 250kW Proton Beam

  18. International Collaboration with MYRRHA ADS without MA fuel（LBE coolant, Accelerator, Operation of ADS） Power ADS Transmutation plant 30MW-beam,800MWth 　・Transmute 250kg of MA annually Experimental ADSMYRRHA ~2.4MW-beam, 50~100MWth 　・Engineering feasibility of ADS and fuel irradiation Reactor physics of MA transmutation system and material development for spallation target material Advanced material for beam window TEF in J-PARC250kW-beam 　・LBE target technology 　・Reactor physics of transmutation system Basic research (LBE loop test, KUCA experiments) year 2050 2010 2020 2030

  19. Working Party to Review Partitioning and Transmutation Technology • The Ministry ofEducation, Culture, Sports Science and Technology (MEXT) in Japan has launched a Working Party to review Partitioning and Transmutation Technology in August, 2013. • An interim report was issued in November, 2013. • Key Descriptions: • To reduce the burden of HLW management, it is expected that flexibility in future political decision is extended by showing possibilities of new concepts of back-end with high social receptivity. • The ADS Target Test Facility (TEF-T) is being proposed under J-PARC to verify the feasibility of the beam window. It is appropriate to shift the R&D of the facility to the next stage. • The Transmutation Physics Experimental Facility (TEF-P) is being proposed under J-PARC to overcome difficulties in reactor physics issues such as for a subcritical core and an MA-loaded one. Since this facility is proposed as a nuclear reactor, the safety review by the new regulation is to be applied. With taking care of this point, it is appropriate to shift the R&D of the facility to the next stage. • For MYRRHA Program, it is appropriate to proceed with negotiation about JAEA’s participation at a reasonable level and mutual collaboration with Belgium and other relevant countries. • Progress of the development should be checked according to its stage.

  20. Concluding Remarks • ADS provides us a possibility to flexibly cope with the waste management in various situations of nuclear power. • R&D on ADS and its compact fuel cycle are under way in JAEA, and we are proposing the Transmutation Experimental Facility as the Phase-II of J-PARC. • To overcome various technical challenges for this technology, the international collaborationis of great importance.

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