Safety analysis of graphite core in molten salt test reactor

1. Safety analysis of graphite core in molten salt test reactor Derek Tsang SINAP 16.09.2013

2. Introduction • The Chinese Academy of Sciences (CAS) has launched a Thorium Molten Salt Reactor (TMSR) research project in 2011. • 350M USD for 5 years • To develop generation IV molten salt reactors. • Multipurpose applications of high temperature nuclear energy. • To build two molten salt test reactors between 2015 and 2017. • A CAS center for TMSR research has been set up at the Shanghai Institute of Applied Physics (SINAP) to lead the project.

4. SINAP has a light source: Shanghai Synchrotron Radiation Facility (SSRF) • 150 MeV Linear accelerator. • 3.5 GeV Booster, 180m circumference • 3.5 GeV Storage Ring, 432m circumference • Number of Cells = 20

5. Introduction • Two types of molten salt reactors: • Molten salt and molten salt-cooled reactor. • Molten salt reactors use salt as fuel and coolant • Molten salt-cooled reactors use TRISO fuel and salt as coolant only. • Molten salt reactors may have a fully closed fuel cycle, however, online reprocessing is challenging. • Molten salt-cooled reactors have a once-through fuel cycle, however, have high temperature and efficiency.

6. Molten salt coolant • Coolant salt has • Good thermal conductivity • High boiling point • Nuclear system can operate at much lower pressure than high temperature gas cooled reactor • High melting point • Trap fission products in an accident • Large heat capacity • During accident the temperature of the core rises slowly

7. 10MW salt-cooled test reactor • TMSR SF1 • Built around 2015~2016 • Aims: • To gain experiences on design, construction and operation • To validate models, analyses and codes • To test the equipment and safety features • To accumulate operation data for larger-size reactors design and licensing

8. 10MW salt-cooled test reactor • TRISO is used as nuclear fuel • 6cm diameter fuel pebbles • Graphite is used as moderator and reflector • Primary coolant is FLiBe salt • Operating temperature is between 600C and 650 C • Core dimensions is 2.6m(dia.) x 3.0m(h)

9. 10MW salt-cooled test reactor

10. Challenges for the 10MW test reactor • Reactor licensing • No molten salt-cooled or molten salt reactor has been licensed in China before • The regulators in China have limited exposure to either molten salt-cooled or molten salt reactor. • Stress analysis • Material properties • Irradiation data

11. Graphite stress analysis • Density of graphite: 1.77g/cm3 • Density of molten salt: 1.99g/cm3 • Buoyant force acts on graphite bricks! • Graphite bricks must be constrained within the core! • Solid liquid interaction

12. Graphite problems • Molten salt may penetrate into graphite. • Modify graphite material properties?!? • How to measure Young’s modulus with molten salt at high temperature: • Dynamic method • Static method

13. Graphite Irradiation program • Measure irradiated graphite material properties • Young’s modulus • CTE • Dimensional change • Thermal conductivity • Tensile strength • Compressivestrength • With and without molten salt.

14. Graphite experiments • Shaking table 2m x 2m • Seismic test on graphite component

15. Thank you!