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 and Department of nuclear reactors Faculty of Nuclear Sciences and Physical Engineering Czech Technical University in Prague 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. Outline Motivation – MSR and AHTR Program EROS Experimentalsetup MCNP simulationsofthe salt channel Achievedresults Conclusion 2

3. AHTR and MSR • Molten salts have good heat-transfer properties • Demands on molten salts concerning their composition and properties differ in the way of their application • MSR (Molten Salt Reactor) uses in the primary circuit molten salts containing fissile 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 without fissionable material • PB-AHTR (Pebble Bed Advanced High-Temperature Reactor) uses modular or integral design with high-temperature fuel pebbles filled with TRISO particles in graphite coating

4. Program EROS • EROS = Experimental zeRO power Salt reactor SR-0 • Program serves for experimental verification of insertion zones of MSR type demonstration unit in reactor LR-0 • Within the frame of the project SPHINX at Nuclear Research Institute (NRI) overall 5 experiments were carried out with modules denoted EROS 1 to EROS 5 inserted into the core of reactor LR-0 • Modules differed in number and configuration of various blocks, in amount of salt and graphite contained in the core and in number and enrichment of fuel assemblies • Distribution of flux density and neutron spectrum in the driving zone and in salt channels were examined by 3 methods: neutron activation analysis, gama scanning method of fuel rods and thermoluminiscence detectors • Simulated setup is most similar to the experiment EROS 2

5. MCNP simulations of the salt channel • Salt channel 600 mm high surrounded with 6 shortened WWER-1000 fuel assemblies enriched with 4.4 % 235U • Salt channel consists of 7 sections made of aluminum • The sections are filled with mixture of LiF-NaF salt with the composition 60-40 molar % and the density of 1.7 g/cm3 • LiF salt first with natural composition 92.5 % 7Li, 7.5 % 6Li, then changed to enriched 7LiF salt with 99.995 % 7Li • 25 experimental channels with diameter of 10 mm • Experimental aluminium probes with diameter of 8 mm and 3 positions for activation foils (bottom, middle, top) at height of 150, 300 and 450 mm above the bottom of the salt channel • Activation foils made of various activation materials with diameter of 6 mm and 50 µm thin

6. Simulationof salt channel in MCNP Salt channelwithfuelassemblies – horizontalandverticalsectionofthesetup

7. Simulationresults (1/10)meshtallies (1/4)salt channelfilledwithLiF-NaF – horizontalsection 0 – 0.5 eV 0.5 eV – 0.5 keV 0.5 keV – 10 keV +60 cm 0 -60 cm 0 +60 cm 100 keV – 1 MeV 10 keV – 100 keV 1 MeV – 20 MeV

8. Simulation results (2/10)mesh tallies (2/4)salt channel filled with 7LiF-NaF – horizontal section 0 – 0.5 eV 0.5 eV – 0.5 keV 0.5 keV – 10 keV +60 cm 0 -60 cm 0 +60 cm 100 keV – 1 MeV 10 keV – 100 keV 1 MeV – 20 MeV

9. Simulation results (3/10)mesh tallies (3/4)salt channel filled with LiF-NaF – vertical section 0 – 0.5 eV 0.5 eV – 0.5 keV 0.5 keV – 10 keV +60 cm 0 -60 cm 0 +60 cm 100 keV – 1 MeV 10 keV – 100 keV 1 MeV – 20 MeV

10. Simulation results (4/10)mesh tallies (4/4)salt channel filled with 7LiF-NaF – vertical section 0 – 0.5 eV 0.5 eV – 0.5 keV 0.5 keV – 10 keV +60 cm 0 -60 cm 0 +60 cm 100 keV – 1 MeV 10 keV – 100 keV 1 MeV – 20 MeV

11. Simulation results (5/10)neutron spectra (1/2)salt channel filled with LiF-NaF – activation foils in middle positions of aluminium probes in experimental channels channel 2 channel 4 channel 3 channel 1

12. Simulation results (6/10)neutron spectra (2/2)salt channel filled with LiF-NaF – activation foils in middle positions of aluminium probes in experimental channels channel 7 channel 5 channel 8 channel 6

13. Activation detectors

14. Simulation results (7/10)reaction yields of activation materials in 7LiF-NaF – (n,g) reactions upper position lower position middle position

15. Simulation results (8/10)reaction yields of activation materials in 7LiF-NaF – (n,p) reactions upper position lower position middle position

16. Simulation results (9/10)reaction yields of activation materials in LiF-NaF – (n,g) reactions upper position lower position middle position 16

17. Simulation results (10/10)reaction yields of activation materials in LiF-NaF – (n,p) reactions upper position lower position middle position 17

18. Summary Simulationsweremade as part ofresearchprojectanddiploma thesis Experimentalsetupsimilar to EROS 2 wassimulated in MCNP Simulationsweremadeforbothnaturaland7Li enrichedcompositionofLiF-NaF salt 9 differentactivationmaterialswerechosenforevaluatingactivationreactionyields Achievedresults: neutron fielddistribution in the salt channel, neutron spectraandactivationreactionyields in 24 positionsforactivationfoils 18

19. Thank you for your attention