Transmutation. Janne Wallenius Professor Reactor Physics, KTH. ACSEPT workshop, Lisbon

Transcription

1 Transmutation Janne Wallenius Professor Reactor Physics, KTH

2 Why would one want to transmute high level nuclear waste? Partitioning and transmutation of Pu, Am & Cm reduces the radio-toxic inventory of long lived high level waste reduces the heat load of geological repositories reduces the inter-generational liabilities of nuclear power permits to start fast spectrum Gen-IV reactors forms the basis for a transition to sustainable nuclear power Is good for society!

3 Why would one not transmute high level nuclear waste? Partitioning and transmutation of Pu, Am & Cm increases inventory of short and medium term radio-toxicity increases medium level waste production increases short term risks increases costs of nuclear power might not be a socially robust technology Features some issues which should be addressed.

4 What shall we do with the nuclear waste? Partition & Transmute! LWR LWR-CORAIL 65% 90% Spent fuel Spent fuel Pu Fission products Fission products Reprocessing TRU U Repository Reprocessing Repository Am + Cm Spent fuel Spent fuel 35% Generation IV fast reactors Fast Reactor 10% ADS Accelerator Driven Systems

5 Fast versus thermal spectrum In order to reduced radio-toxic inventory of spent nuclear fuel, both Pu, Am & Cm must be recycled! In a thermal spectrum, fission probability of even neutron number nuclides ~ Radiotoxic inventory [Sv/g] 240 Pu 239 Pu 238 Pu 243 Am 242 Pu U nat 237 Np TRU 241 Am t [y] Build-up of the strong neutron emitter Cf-252 is 2 3 orders of magnitude higher in a thermal spectrum than in a fast spectrum! If curium separation is not implemented (GANEX), a fast spectrum is mandatory! Sodium, lead or gas! 238 Pu 239 Pu 240 Pu 241 Pu 242 Pu 241 Am 243 Am 244 Cm 245 Cm 246 Cm 247 Cm Fissionprobability

6 Sodium cooled fast reactor

7 Pros and Cons of the Sodium Fast Reactor + Based on coolant technology proven on industrial scale + Large demonstration facility may be ready within a decade + Good breeding performance Costs for prevention of sodium-water interaction Safety issues related to coolant boiling Phénix Marcoule France

8 Lead cooled fast reactor

9 Pros and Cons of the Lead Fast Reactor + No chemical interaction with water (no intermediate heat exchanger) + High boiling temperature low probability for coolant voiding K745 Soviet submarine + High fraction of natural circulation passive heat removal Coolant technology proven only in military submarines Costs for corrosion control & surface protection Erosion of pump blade surfaces

10 Gas cooled fast reactor

11 Pros and Cons of the Gas Fast Reactor + No need for secondary coolant (direct turbine cycle) + Visual inspection of core possible + Chemical interaction with structural materials only from impurities No operational experience High pressure system Decay heat removal under loss of pressure requires active system Lack of validated materials for cladding and heat exchanger

12 Fast spectrum systems: common issues Fast neutron recoils lead to radiation damage Swelling of austenitic (fcc) steels Embrittlement of ferritic-martensitic (bcc) steels Possible solution: Oxide dispersion strengthened ferritic steels (ODS). Before After Ability to accept legacy americium from LWRs in critical reactors is limited by safety considerations and depends on design, including choice of fuel and coolant.

13 Impact of americium on fast reactor safety MOX fuel temperature [K] UTOP, 5% Am UTOP, 1% Am ULOF, 5% Am Introduction of americium into the fuel of fast reactors leads to Reduction of Doppler feedback Increase of coolant temperature coefficient Reduction of delayed neutron fractions Time [s] Transients in SFR with MOX fuel Zhang & Wallenius, Ann. Nucl. Energy, In Press Power density should be reduced in proportion to Am fraction Power penalty of 6% per percent americium in fuel of sodium cooled fast reactors

14 Accelerator Driven Systems European Facility for Industrial Transmutation EFIT 400 MWth lead cooled ADS with inert matrix (Pu0.45,MA0.55)O1.9-MgO fuel Conceptual design completed within EUROTRANS project Minor Actinide burning rate: 42 kg/twhth Plutonium production rate: ~0! From 2nd recycle: Fed exclusively by LWR stock of minor actinides!

15 European Sustainable Nuclear Industrial Initiative ESNII MWe ESFR project ~100 MWth CDT project ~100 MWe LEADER project ~60 MWth GOFASTR project

16 ASTRID Advanced Sodium Test Reactor for Industrial Demonstration EU-project ESFR: Funded with 6 M MOX driver fuel Test assemblies with americium containing MOX fuel, Am originating from decay of 241 Pu. Major design item: Application of ODS steels or not? Location: Next to Phénix 2010: Choice of power 2012: Decision to build

17 LEADER Lead Cooled Advanced Experimental Reactor EU-project starting April 2nd EC-contribution: 3 M Objective: Design of 100 MWe Technology Demonstration Plant Major material issues: Validation of GESA technique for surface alloying (FeCrAlY) Material for pumps: MAXTAL?

18 MYRRHA Lead-bismuth cooled materials test reactor to be built in Mol, Belgium. Sub-critical and critical core configurations with MOX fuel Pilot assemblies with americium bearing fuels Estimated total cost: 1.0 G Belgian government has allocated 40% of costs Design performed in context of CDT project

19 GENIUS project Generation IV research in Swedish Universities (KTH, Chalmers & UU) 3.6 M funding from VR for three years Major activities: Fabrication of (U,Pu,Am)N & (Pu,Zr)N fuels Radiation damage modelling & characterisation, Corrosion of advanced alloys in lead Fuel-coolant interaction, nuclear data, thermalhydraulics of lead, transient analysis, fast neutron detector development, safe-guards.

20 Concluding remarks Partitioning and Transmutation of high level waste may reduce intergenerational liabilities and pave the way for sustainable nuclear power. A fast neutron spectrum is required if curium is not separated Generation IV reactors and ADS may perform the task SFR prototype and alternative coolant demonstration facilities could be in operation years from now. Need for associated fuel cycle facilities (partitioning of minor actinides, MOX and MA bearing fuel fabrication) Choice of socially and economically robust options to be made!

21 Choice of steels for fast neutron reactors: ODS? Austenitic steels (15 15Ti) qualified for application in Gen-IV reactors up to doses of ~120 dpa at T < 900 K. Ferritic-Martensitic steels are more radiation resistant, but have poor creep strength at high temperature. Oxide dispersion strengthened (ODS) steels may perform better Oxides oxides Example of ODS steel «!particle Halo!» before irradiation 480 C - 80 dpa (Phénix) halo of fine oxides around the biggest oxides Fe-14Cr-1Ti-0.3Mo-0.25Y2O3 FP7 project GETMAT

22 Dose limits for austenitic steels Best available austenitic steel applicable for doses up to about 120 dpa Corresponds to three year lifetime of fuel cladding at dose rate of 40 dpa/year Dose rate dependence significant lower dose rate reduces swelling threshold! Ferritic-Martensitic steels swells considerably less