University Ghent Reactortheory: Partim I The nuclear fuel cycle Uranium ore Reactor Reprocessing

University Ghent Reactortheory: Partim I 2 Fresh fuel (not irradiated) Spent fuel in hotcell (irradiated and highly radioactive) Examples of nuclear material: Nuclear Material is precious nuclear material radioactive material U natural U enriched in U-235 Th (Th-232) Pu Am … U-233 Co source (Co-60) Fission products I, Tc, Sr, Xe, Nd, Sm, Pr, … Ra, Po, …

University Ghent Reactortheory: Partim I Reactor core evolution: change in isotopic composition change 9kg U-235 used 4 kg Pu produced 25kg U-235 used 7 kg Pu produced Burn Up (BU)  energy eff. supplied by 1 ton fuel BU  Enrichment * MWd /ton

University Ghent Reactortheory: Partim I Front End 3 months 6 months 4 yr + 15 yr storage € /kg 10% 5-8 € /kg U 1.5% € /SWU 23.5% € /kg 15% 2 c € /kWh 50% Fuel fabrication UO 2, MOX Enrichment Mining Conversion 950 tons natural U 110 ton enriched U 840 tons depleted U Reactor

University Ghent Reactortheory: Partim I Enrichment LWR/WWER: UO 2 : cycle of 12 months, fuel with % U-235 LWR: MOX: cycle of 18 months, 91.3–95.6% UO 2 with 3.8–4.2 % U % PuO 2 RBMK: UO 2 : continuous refueling, fuel with % U-235 Concentration factor Value change by enrichment :  u : SWU/kg Enrichment : F=P+W Fx F =Px P +Wx W Feed F x F U-235 Product P with x P U-235 Waste W with x W U-235

University Ghent Reactortheory: Partim I Enrichment operations: ultra-centrifuge Urenco depleted waste stream enriched product stream vacuum feed casing Electric motor

University Ghent Reactortheory: Partim I Enrichment operation: ultra-centrifuge Centrigual force separates light (U-234 and U-235) and heavy (U-236, U-238) atoms Cascades are necessary for the desired enrichment grade - Cascade in series: For larger enrichment grade - Cascade in parallel: For larger throughput Enrichment Gain per centrifuge Urenco

University Ghent Reactortheory: Partim I Enrichment operation: gaseous diffusion Depleted waste stream = feed to preceding gas diffuser end collector depleted stream External diameter 1 m, height 8 m Membrane pipes F W P collector enriched stream Feed Enriched product stream = feed of next gas diffuser membrane

University Ghent Reactortheory: Partim I Enrichment operation: gaseous diffusion Eurodif Selective diffusion through membrane yields separation of light (U-234 and U- 235) and heavy (U-236, U-238) atoms Enrichment gain per gas diffuser The diffusion mechanism follows Graham’s law:

University Ghent Reactortheory: Partim I Fuel fabrication: example of mass balance areas Input: UF 6 Output: - pellets - F.A.

University Ghent Reactortheory: Partim I Back End 2 yr 50 yr 2 c € /kWh 50% € /kg 40% € /kg 10% Reprocessing Purex U, Pu Conditioning + interim storage 4 yr + 15 yr storage Reactor Fuel fabrication UO 2, MOX Enrichment Conversion Final disposal 110 ton S.F. 1 ton Pu 105 ton U 18 m 3 HLW 130 m 3 MLW 600 m 3 LLW

University Ghent Reactortheory: Partim I Spent Fuel Reprocessing Originally: 1940 (military) : separation by precipitation Now : separation by liquid-liquid-extraction Most important process: PUREX process (over 50 yr experience) Steps: 1. Chopping of fuel pins in the fuel assemblies gaseous fission products: removed via holdup filters 2. Dissolution of fuel in 3-5 molar HNO 3 addition of Gd for criticality safety reasons 3. Filtration metal parts and scrap are filtered out as waste solid fission products are chemically removed 4. Separation of U+Pu+M.A. 5. Separation of Pu and U 6. Product formation: powders U-oxide and Pu-oxide 7. Waste conditioning (in vitrification facility)

University Ghent Reactortheory: Partim I Step 1 of reprocessing 1. Continuous dissolving oplossen Input Accountancy Tank

University Ghent Reactortheory: Partim I Reprocessing : core activity Separation by liquid-liquid-extraction with PUREX process - with nitric acid HNO 3 - with TBP: tributyl phosphate PO(C 4 H 9 O) 3 Mixing and separation of U+Pu+Minor Actinides by (i) mixer-settler (late split) of (ii) pulse column (early split) P C4H9OC4H9O C4H9OC4H9O C4H9OC4H9O O

University Ghent Reactortheory: Partim I Reprocessing plant: material balance areas Input: Spent fuel from different reactors Output: Product 1 Product 2 Product 3 MBA = MBA1 + (Input for fuel) MBA2 + (to dissolve in the input accountancy tank) MBA3 (Separation of purified products)

University Ghent Reactortheory: Partim I Belgian management of nuclear fuel 110 ton/yr enriched U 3.8% 105 ton/yr resid. U (1%) 1 ton/yr Pu, 4 ton/yr FP GWh/yr MiningConversionEnrichment Reprocessing Fuel fabrication Final disposal Interim conditioned storage

University Ghent Reactortheory: Partim I Possibilities for a nuclear fuel cycle 1. With MOX fuel fabrication 61% 84% 16% 2. With fuel for fast reactors 3. With recycling of fuel for fast reactors Fast reactor

University Ghent Reactortheory: Partim I Nuclear explosive devices Pu bom (Nagasaki) U bom (Hiroshima)

University Ghent Reactortheory: Partim I Mixture of nuclear material: critical mass Criticality experiment (LANL, 1945): a sphere of Pu surrounded by neutron-reflector (W-C) Critical mass of fissionable material depends on: - on nuclear material: nuclear properties, physico-chemical properties (density, purety) - geometry (shape) - composition: surrounded by neutron reflector, interrupted by absorber (Monte Carlo simulations)

University Ghent Reactortheory: Partim I 20 The size of a homogeneous critical mixture is determined by: the critical length r such that the neutron, emitted by the fission in the mixture, induces another fission before leaking out of the mixture r ~ inversely proportional with material density smallest geometry is a sphere with  critical mass is therefore: Remark: Power reactors: have the volume to scatter and thermalize the neutrons Critical mixture: determined by critical length V = r 3

University Ghent Reactortheory: Partim I Critical mass of U metal sphere in Be reflector Ref: Monte Carlo simulation (Glaser, 2005) U metal Be 5cm HEU with U-235  20% U mass differentiated for strategic value (1955, Weinberg) LEU can not be used because of too large critical mass and corresponding n emission rate At enrichment levels 15-20% Pu production is sufficiently suppressed

University Ghent Reactortheory: Partim I 22 Critical mass of Pu metal sphere in natural U reflector Ref: Monte Carlo simulation (De Volpi, 1979) Pu metal Nat.U 10cm 7%  Pu-240 < 18% Fuel Grade 8 kg needed 3%  Pu-240 < 7% Weapons Grade 4-8 kg needed Pu-240  3% Super (Ivory) Grade 3 kg needed Differentiation between reactor grade, fuel grade, weapons grade and super grade (Pellaud, 2002)

University Ghent Reactortheory: Partim I 23 With nuclear material, containing sufficiently fissile material, there are two possible designs for a nuclear device: 1. If the nuclear material is Uranium enriched in U-235 (25 kg): 2. If the nuclear material is Plutonium (8 kg Pu-239 with not too much presence of Pu-240 and in stable  metal form) Two path ways to make a nuclear device

University Ghent Reactortheory: Partim I Independent verification of nuclear inventory Continuity of Knowledge: (freezing of verified situation, confirmation of declaration/ absence of non-declared actions) 3 safeguards goals: - Quantity Q nuclear material M - Timeliness: T -Probablity: P Analyse by means of samples:

University Ghent Reactortheory: Partim I Non-Proliferation Treaty (Euratom in EU) (3227/76) NPT Watchdog: IAEA - declared nuclear weaponstate - suspect nuclear weapon programme - non-declared weaponstate - repelled nuclear weapon programme - Abstaining state - States from former Soviet Union

University Ghent Reactortheory: Partim I Non Proliferation Test Ban Avoid the proliferation of nuclear Material Ban explosion testsStop production of WG Nuclear Materials Comprehensive Test Ban Treaty (CTBT) Fissile Material Cut-off Treaty (FMCT) Nuclear materials & technologies Nuclear weapons Fissile materials WG-materials Dismantling of WMD EURATOM-NPT Safeguards Agreements Strengthening of Safeguards System Protocol Dual Use Export/Import Control Physical Protection Convention Illicit Trafficking NWSNNWS NWS NWS ( NNWS) MIL. CL. MIL. NPT Trilateral Agreements RF/IAEA/US Bilateral Agreements RF/US START Nuclear non-proliferation and related treaties MIL. CIV.

University Ghent Reactortheory: Partim I 27 Safeguards Security Safety

University Ghent Reactortheory: Partim I 28 Inspection of all facilities in the fuel cycle Nuclear safeguards: inspections

University Ghent Reactortheory: Partim I Safeguards

University Ghent Reactortheory: Partim I Steps towards disarmament Neutron counter & Gamma- spectrometer for a restricted verification (filtering out sensitive military information)

University Ghent Reactortheory: Partim I Additional control methods in the civil cycle Satellite images Doel area IRS-1C, PAN sensor, GSD 5.8 m SPIN, KVR-1000 GSD 2 m

University Ghent Reactortheory: Partim I 32 Nuclear safeguards: satellite imagery

University Ghent Reactortheory: Partim I Nuclear safeguards: satellite imagery

University Ghent Reactortheory: Partim I Nuclear safeguards: satellite imagery