Graphite Component Assessment for TMSR

1. Graphite Component Assessment for TMSR Samantha Yong, Derek Tsang, Maoyuan Cai

2. Contents • Introduction of ASME and KTA-3232 • The numerical result from ASME and KTA-3232 • Effect of maximum grain size on probability of failure finally

3. TMSR graphite core • 16 graphite components • Top and bottom reflector • Side reflector • Dowel • Key • To show the designs are safe • There are two standards • ASME USA • KTA-3232 German

4. Introduction of ASME and KTA-3232

5. Probability of Failure flow chart in ASME stress limit

6. In process , equivalent stress is calculated as Xi is the index of Weibull distribution calculated as

7. probability of failure procedure in KTA-3232 main difference between ASME HHA and KTA-3232 is as follows: componentsare grouped in ASME, do not need to be grouped in KTA-3232

8. The difference between ASME and KTA-3232 • Probability models • ASME：Weibull three parameter model • KTA-3232： Weibull two parameter model • Calculate method • ASME：group the integration points, Group Conditions： • The group volume is bigger than (10×mgs)3 • In the group , max(Xi) is greater than min(Xi) 7% • KTA-3232：do not group the components

9. ASME HHA POF Limits • KTA-3232 POF Limits The POF limits of ASME HHA and KTA-3232 are same .

10. 2. The calculate result of ASME and KTA-3232 Finite element model Boundary conditions: a. The model is symmetry by the XY, XZ plane, ¼ model is to be calculated. • Calculation software :ABAQUS, element type C3D20, element number 11786. the irradiation distribution under normal operation as shown in Figure 1.

11. The stress of component after 20 years Table 1. POF of 2 different model The POF of ASME is more conservative Model 1 keyway root radius=2mm Model 2 keyway root radius=5mm

12. 3. Effect of maximum grain size(MGS) on probability of failure • Maximum grain size: the maximum filler particle grain size that is used in the graphite formulation. • Each graphite has different MGS, however MGS is one of the most important factors to affect POF, so we have analyzed the effect of MGS on POF. Table 1. different MGS for different graphite [1]A modified weibull theory for the strength of granular brittle material [2] A numerical stress based approach for predicting failure in NBG-18 nuclear graphite components with verification problems

13. The POF of Graphite component of NBG-18 In order to analysis the effect of MGS, NBG-18 is chosen to calculate POF. Table 1. Parameter of three parameters Weibull distribution Table 2. POF of same model for different MGS • MGSis one of grouping criterion in ASME. • The grouping criterionis based on experiment of NBG-18. • The grouping criterion is suitable for the graphite has the same or similar MGS. • The method to calculate POF maybe conservative (or too conservative) if the MGS is small when assess the fine grade graphite. • The group criterion should be remark for the fine coarse graphite.

14. Conclusions • Described the differences between ASME and KTA-3232, compared the POF of the two standards, The POF of ASME is more conservative. • The effect of MGS on POF has been analyzed, ASME standard is based on coarse grain graphite, for fine grain graphite the grouping criterion should be modified for the fine grain graphite. 14

15. Thank you