1. INGSM 15 The application of laser granulometer on carbon powder characterization for quality control and optimization of nuclear graphite products Qian Zheng 1, Jing Zhang 1, Yuzhen Mao 1, Junguo Zhao 1, Dai Huang 1, Houzheng Wu 1,2*

2. INGSM 15 Background Laser granolumeter Test conditions Outline Application

3. INGSM 15 Background A strict control of particle size and size distribution of powders of carbon power is required Graphite powerNuclear fuel pellets high temperature gas-cooled reactors Graphite Coke powder Mixing powder Ultrafine powder

4. INGSM 15 Why laser grnulometer Vibrating screeningAirflow screening Laser granulometer Grain size measuring means

5. INGSM 15 Vibrating screening Advantage: easy to operate and achieve Disadvantage: a ） Measurement of size distribution is discrete b) Agglomerated particles can’t go through the sieve – suitable for large particulates, rather than fine ones.

6. INGSM 15 Airflow screening Advantage: The scope, efficiency, precision and repeatability of airflow screening are better than vibration Disadvantage: a) Only one sieving can be used for separation each time, leading to a complex operation required. b)The detailed size distribution is hard to be provided.

7. INGSM 15 Laser granulometer Grain size measuring means Advantage: A small amount of power is enough to have details on size distribution quick and convenience, good repeatability, Cover wide range of particle sizes. Disadvantage: Risk of error for a lack of representativeness

8. INGSM 15 Test conditions Instrument: laser granulometer (S3500), US Microtrac corp. Samples: graphite powder, coke powder, mixed powder of coke and binder, ultrafine powder, i.e. D50<5µm) Surfactant used: Triton X-100(octyl phenoxy poly ethoxy -US Fisher Scientific)

9. INGSM 15 Results Suspension concentration The affect of suspension concentration on different material excessive appropriate small √√ √

10. INGSM 15 Results (cont.) Repeatability test with different suspension concentration of mixing power Repeatability is poor for a sample lack of representativeness √ √ Best choice Risk on instrument maintenance

11. INGSM 15 Results (cont.) using surfactant Before After √

12. INGSM 15 Results (cont.) The affect of surfactant on different materials √

13. INGSM 15 Results (cont.) The affect of ultrasonication on different material √ √√

14. INGSM 15 Results (cont.) Repeatability test results of different materials under optimum disperse conditions D50:CV-2.03% D50:CV-0.87% D50:CV-3.21% D50:CV-4.04%

15. INGSM 15 Application model Laser granolometer measurements are used as the fundamental inputs of modelling, for achieving the best possible particle sizes and size distribution through a combination of powders with different ones, with models developed via theoretical prediction. New particle population =  A+  B+  C+… WE chose A,B,C three types of powder having different size distribution, and had the  :  :  in different ratios, such as 3:1:3 ， 2:1:2 ， 3:1:2

16. INGSM 15 Application (cont.) The comparison between theoretical prediction and experimental measurement Theoretical result Test result Test result Theoretical result Test result Theoretical result

17. INGSM 15 Application (cont.) Relation between CS and SSA CS: Specific surface area that was calculated by size distribution data with a hypothesis that particles are all spherical solid. SSA: Specific surface area measured with BET based on the N 2 adsorption We chose different raw materials, 1 and 2, which is milled with same equipment but different conditions to get five powders with different size distribution.

18. INGSM 15 Application Relation between CS and SSA CSSSA SSA/ CS R I 0.3234.714.6 0.97 0.34.715.7 0.3314.6714.1 0.3385.0815.0 0.5637.713.7 II 0.2621.234.7 0.99 0.2731.34.8 0.2791.34.7 0.3461.684.9 0.3561.684.7 SSA=k*CS

19. INGSM 15 Application Relation between CS and SSA CSSSA 5min 4h k Need more experiments to build the model

20. INGSM 15 Summary  To achieve better dispersion suitable for laser ganulometer, appropriate suspension concentration, surfactant, and ultrasonication are necessary  It is approved possible and controllable to achieve a powder with expected particle population through combining powders with different particle population, based on a theoretical model.  If the powder production technology is relatively stable and consistent, it is possible to establish relationship between normalized specific surface area measured with laser granulometer and that with BET based on the N 2 adsorption. It will offer foundation on estimating the SSA by laser granulometer.

21. INGSM 15 Thank you for your attention!