Characterization of Tritium Transport in the FLiBe-Graphite System

Transcription

1 Characterizatin f Tritium Transprt in the FLiBe-Graphite System Huali Wu Michael Yung, Nisarg Patel, Jayeesh Bakshi, Raluca Scarlat Nuclear Engineering, UW Madisn huali@wisc.edu ǁ HEATandMASS.ep.wisc.edu Huali Wu ǁ HEATandMASS.ep.wisc.edu 1

2 Mtivatin! Overview f FHR Technlgy! Tritium Inventry in Mlten Salt Reactr and FHR Tritium Prductin Tritium in Graphite Tritium in Mlten Salt! Graphite as a ptential tritium sink in FHR MSRE experience FHR uniqueness Irradiatin Effect Salt infiltratin! Summary! Current/Future Wrk 2

3 Overview f FHR technlgy UNIQUENESS Large Carbn Surface Area Fuel pebbles and inert graphite pebbles 1945 m 2 Inner and uter graphite reflectr 54 m 2 Carbn filter cartridges (if needed) in CTAH 2300 m 2 Nuclear Air-Braytn Cmbined Circle CONCERNS Large tritium prductin rate Salt chemical cntrl affects tritium species (T 2, TF, HT, etc.) Tritium Leakage thrugh CTAH and ther metal structures DHX Wells Defueling Machine Cntrl Rds Fuel Pebbles Graphite Pebbles Outer Reflectr Central Reflectr Ht Salt Extractin Ht Salt Manifld Pipe Ciled Tube Bundle Cled Salt Manifld Pipe Remvable Vessel Head Heated Air Outlet Duct CTAH Pressure Vessel with Internal Insulatin Warm Air Inlet Duct Miter Bend Turning Vans Thermal Pwer 236 MWth 68.3% Fuel Cre Sphere Cmpsitin Cre Inlet Temperature 600 C 31.7% Graphite Cre Outlet Temperature 700 C Residence Time f Pebbles 2.1 Mnth Fuel Pebble Quantity Pebble Circulatin Rate Pebbles/day Inert Graphite Pebble Quantity

4 Tritium Inventry TRITIUM PRODUCTION! Tritium Surce 6 Li, 7 Li, 9 Be Initial Li-6 enrichment 60ppm Tritium prductin rate 0.11ml/EFPD Equilibrium Li-6 cncentratin 4 ppm Tritium prductin rate 0.023ml/EFPD! Tritium Emissin Limit 0.1pCi/L fr air effluent, and 1µCi/L fr water effluent Estimated Tritum Prductin Rate in the Mk1 PB-FHR Cre Type g/yr/gwe Ci/yr/Gwe(*10^6) Tritium Prductin Rate (Ci/ EFPY) Effective Full Pwer Years (ml T/EFPD) PB-FHR PWR CANDU HTGR PBMR MSR FHR DESIGN GOAL 99.9% f tritium prduced in FHR shuld be recvered 4

5 Tritium Inventry TRITIUM SOURCES AND SINKS 5

6 Tritium Inventry TRITIUM IN GRAPHITE! Pre diffusin Mlecule diffusin Physisrptin and chemisrptin Lw energy! Bulk diffusin Atm diffusin Chemisrptin dminated Depending n trapping sites energy Trapping-detrapping prcess IN FHR D pre = 650 C & D bulk = 750 C Trap site 1 is hard fr tritium t 700 C Pre Pre IG-110 (Ultrasnic Cleaned) A3 (Plished and Ultrasnic Cleaned) 6

7 Tritium Inventry TRITIUM IN MOLTEN SALT! Tritium is prduced in the frm f T +, and exists in salt as TF, T 2, HT, etc. depending n Flibe prperty! TF is a cndensable, crrsive gas! T2 r HF is ready t diffuse thrugh metal structural 600 C t 700 C! Tritium will leak frm tubes in CTAH Aluminum xide cating can reduce tritium leakage Cld trap Inert gas sparging WHY SO IMPORTANT?! Via mass cnvectin in Flibe, tritium will eventually reach surface f fuel pebbles and get absrbed r diffuse in graphite D T2 ~ 3E-09 m C Saturatin vs. rate-limiting 7

8 Graphite as A Ptential Tritium Sink SUMMARY OF MSRE EXPERIENCE! MSRE verview 8 MW th reactr with fuel salt Operated at 700 C The reactr cre is made f nuclear graphite blck FHR UNIQUENESS! Fluride salt withut fuel! Higher pwer, higher neutrn flux! Larger carbn surface area! Matrix graphite cmprises ~40% in fuel pebble H. G. MacPhersn, Mlten-Salt Reactr Prgram Quarterly Prgress Reprt, fr perid ending July 31, 1960, Oak Ridge Natinal Lab, ORNL-3014, (1960) APPLICATION OF MSRE DATA Fuel pebble The nly data set generated fr Fluride-salt-graphite system 15% f tritium was absrbed by graphite and abut half was within the first 1/16 th inch layer 8

9 Graphite as A Ptential Tritium Sink NUCLEAR GRAPHITE AND MATRIX GRAPHITE Raw material Heat treatment temperature Micrstructure Degree f graphitizatin Prsity Grain size Etc. Graphitizatin Prcess ( 9

10 Graphite as A Ptential Tritium Sink MATRIX GRAPHITE NUCLEAR GRAPHITE 10

11 Graphite as A Ptential Tritium Sink IRRADIATION EFFECT! Irradiatin effect n diffusin cefficient highly depends n neutrn fluence H. Atsumi, T. Tanabe, et al., Hydrgen behavir in carbn and graphite befre and after neutrn irradiatin Trapping, diffusin and the simulatin f bulk retentin, J. Nucl. Mater., vl. 417, n. 1 3, pp , (2011)! Increase the cncentratin f Trap 2 and Trap 1 Irradiatin has large effect n Trap 2 than Trap1 at lw neutrn fluence Trap 2 is mre useful fr tritium retentin in graphite due t its lw activatin energy H. Atsumi, A. Muhaimin, et al., Hydrgen trapping in neutrn-irradiated graphite, J. Nucl. Mater., vl , pp , (2009) 11

12 Graphite as A Ptential Tritium Sink SALT INFILTRATION R. B. Briggs, Mlten-Salt Reactr Prgram Semianual Prgress Reprt Fr Perid Ending July 31, 1964, Oak Ridge Natinal Lab, ORNL-3708, (1964) Salt Salt will diffuse int graphite, n disslved carbn in salt bserved frm MSRE experiment Impregnated salt in graphite tends t blck r ccupy pres r tritium diffuse paths 12

13 Summary SUMMARY! Tritium is prduced in FLiBe by neutrn irradiatin f 6 Li, 7 Li and 6 Be! Large carbn surface area and cntinuusly refueling in FHR culd prvide a perfect sink fr tritium! Graphite prperty (graphitizatin, prsity, grain size, etc) will affect tritium retentin! Neutrn irradiatin has a psitive effect n tritium retentin in graphite due t the increase f tapping sites! Salt tends t penetrate int graphite and culd play a negative rle fr tritium recvery with graphite 13

14 Current/Future Wrk CURRENT/FUTURE WORK 1. Matrix Graphite Characterizatin Virgin graphite characterizatin Pst-irradiatin measurement 2. Cntact Angle measurement Tp surface withut Insulatin Argn Silica Glass shield with Insulatin Graphite Sample Plate 14

15 3. Flibe-Intrusin Experiment Vertical Furnace Graphite Crucible Sample Hlder Crucible lid Pressure Release Hle 4. Hydrgen behavir in Flibe-Graphite System Hydrgen & graphite Hydrgen & Flibe-graphite system 15

16 Questins? 16