MCNP simulation of salt channel in LR-0 reactor

1. MCNP simulation of salt channel in LR-0 reactor Martin Suchopár Nuclear Physics Institute Academy of Sciences of Czech Republic 12th session of the AER Working Group F - "Spent FuelTransmutations" and 3rd meeting of INPRO Project RMI - "Meeting energy needs in the period of raw materials insufficiency during the 21st century" Liblice, Czech Republic, April 6 – 9, 2010

2. AHTR and MSBR • Demands on molten salts concerning their composition and properties differ in the way of their application • MSBR (Molten Salt Breeder Reactor) uses in the primary circuit molten salts containing fissile and fertile material, which serve as fuel and coolant at the same time • AHTR (Advanced High-Temperature Reactor) uses graphite-matrix high-temperature fuel like in helium-cooled reactors, but provides cooling with high-temperature fluoride salt (~900 °C) without fissionable material

3. Project SPHINX • SPHINX = SPentHotfuelIncinerator by Neutron fluX • Demonstrationnucleartransmutorwithliquidfuelbased on molten fluoride salts • Incinerationoftransuranicelementsandlong-livedfissionproducts • Elementary module designed as subcriticalfuelchannelsurrounded by graphiteblocksequippedwithtubes in whichflowmoltenfluoridesoflong-livedradionuclides • Systemcanbeeithercriticalorsubcriticalwhichiskept in stationarystateandwhospowerisdriven by anexternal neutron sourceor by drivingzonesurroundingthesubcriticalassembly

4. Project SPHINX Elementary module ofthe SPHINX concept

5. Program EROS • EROS = ExperimentalzeROpower Salt reactor SR-0 • Program servesforexperimentalverificationofinsertionzonesof MSR type demonstration unit in reactor LR-0 • Withintheframeoftheproject SPHINX 5 experimentswerecarriedoutwithmodulesdenoted EROS 1 to EROS 5 insertedintothecoreofreactor LR-0 • Modulesdiffered in numberandconfigurationofvariousblocks, in amountof salt andgraphitecontained in thecoreand in numberandenrichmentoffuelassemblies • Distributionoffluxdensityand neutron spectrum in thedrivingzoneand in salt channelswereexamined by 3 methods: neutron activationanalysis, gama scanningmethodoffuelrodsandthermoluminiscencedetectors

6. Simulationof salt channel in MCNPX Simulated arrangement of salt channelsurrounded by 6 fuelassemblies

7. MCNPX simulationsofthe salt channel • Salt channel 600 mm highsurroundedwith 6 shortened WWER-1000 fuelassembliesenrichedwith 4.4 % 235U • Salt channelconsistsof 7 sectionsmadeofaluminum • Thesections are filledwithmixtureofLiF-NaF salt withthecomposition 60-40 molar % andthedensityof 1.7 g/cm3 • LiF salt firstwithnaturalcomposition 92.5 % 7Li, 7.5 % 6Li, then changed to enriched7LiF salt with 99.995 % 7Li • 25 experimentalchannelswithdiameterof 10 mm • Experimental aluminium probeswithdiameterof 8 mm and 3 positionsforactivationfoils (bottom, middle, top) atheightof 150, 300 and 450 mm abovethebottomofthe salt channel • Activationfoilsmadeofvariousactivationmaterialswithdiameterof 6 mm and 50 µm thin

8. Simulationof salt channel in MCNPX Salt channelwithfuelassemblies – horizontalandverticalsectionofthe arrangement

9. MCNPX simulationsofthe salt channel • The simulations were made in MCNPX version 2.6 • The source neutrons were generated by kcode routine with 4.109 source particles • The cross-sections for kcode were taken from standard libraries for neutrons ENDF/B-VII.0 and JEFF 3.1.1 • Maximum energy of neutrons was limited to 20 MeV (sufficient for reactor spectrum) • The energy range 0 – 20 MeV was divided into: • 6 logarithmic intervals for mesh tallies in salt channel • 50 logarithmic intervals for spectra in activation foils

10. Simulationresultsmeshtalliessalt channelfilledwithLiF-NaF – horizontalsection 0 – 0.5 eV 0.5 eV – 0.5 keV 0.5 keV – 10 keV 100 keV – 1 MeV 10 keV – 100 keV 1 MeV – 20 MeV

11. Simulationresultsmeshtalliessalt channelfilledwith7LiF-NaF – horizontalsection 0 – 0.5 eV 0.5 eV – 0.5 keV 0.5 keV – 10 keV 100 keV – 1 MeV 10 keV – 100 keV 1 MeV – 20 MeV

12. Simulationresultsmeshtalliessalt channelfilledwithLiF-NaF – verticalsection 0 – 0.5 eV 0.5 eV – 0.5 keV 0.5 keV – 10 keV 100 keV – 1 MeV 10 keV – 100 keV 1 MeV – 20 MeV

13. Simulationresultsmeshtalliessalt channelfilledwith7LiF-NaF – verticalsection 0 – 0.5 eV 0.5 eV – 0.5 keV 0.5 keV – 10 keV 100 keV – 1 MeV 10 keV – 100 keV 1 MeV – 20 MeV

14. Simulationresultsneutron spectrasalt channelfilledwithLiF-NaF – activationfoils in middlepositionsof aluminium probes in experimentalchannels channel 2 channel 4 channel 3 channel 1

15. Simulationresultsneutron spectrasalt channelfilledwithLiF-NaF – activationfoils in middlepositionsof aluminium probes in experimentalchannels channel 7 channel 5 channel 8 channel 6

16. Aktivační detektory

17. Simulationresultsreactionyieldsofactivationmaterials – (n,g) reactions upper position lower position middle position

18. Simulationresultsreactionyieldsofactivationmaterials – (n,p) reactions upper position lower position middle position

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