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Abstract—This paper investigates the issue of leading edge for EAST tungsten divertor monoblock which is also concerned in ITER project. Besides the positive effects like reduced risk of cracking, the castellation will lead to the increased probability of melting of the castellated divertor due to local power load on leading edge of the gap. That may introduce unacceptable amount of impurity into plasma and cause damage to the plasma facing components. The chamfering on monoblock is applied in order to avoid melting due to the local heating at leading edge. The previous research [1] had calculated the temperature distribution by employing finite element method and proposed an optimized chamfering geometry for the W monoblock in EAST, which can effectively reduce the maximum temperature under 10 MW/m2 heat load. In this work the stress of monoblock under the thermal load is further analyzed by means of finite element software ANSYS in order to evaluate the integrality and lifetime of monoblock. Both of the steady state and transient (e.g. ELM) thermal load are considered in the numerical calculation. According to the results of recent researches[2-4] the cosine law is applied in the calculation for steady state thermal load, and the ion orbit model is used for ELM condition. The behaviour of crack initialization is analyzed by using damage parameter curve which is obtained under creep and fatigue load. Moreover, crack propagation rate model is employed in the fatigue and creep lifetime evaluation for both shaped and unshaped monoblock. The result shows that the shaping for monoblock will lead to movement of the location of highest temperature toward the central region of top surface of monoblock. That will increase the gradient of temperature, so as to enhance the stress at W/Cu interface. The shaping for monoblock can reduce the risk of melting due overheating on leading edge. However, the life time of monoblock could be shortened due to increased stress.
Keywords—W/Cu monoblock, leading edge, stress, lifetime
REFERENCE
[1] Xiahua Chen, et al. Numerical optimization of tungsten monoblock tile in EAST divertor Fusion Engineering and Design, Vol.108, pp98-103, 2016,
[2] R. A. Pitts, et al. Numerical evaluation of heat flux and surface temperature on a misaligned
JET divertor W lamella during ELMs, Journal of Nuclear Materials, 2011, Vol.415 Issue 1, pp S957-S964.
[3] R. Dejarnac, et al. Physics basis and design of the ITER plasma-facing components, Nuclear Fusion, Vol.54, pp 123011, 2014
[4] R. A. Pitts, et al. Physics conclusions in support of ITER W divertor monoblock shaping, 22th International Conference on Plasma Physics Surface Interactions in Controlled Fusion Devices, 2016
| Eligible for student paper award? | No |
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