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Abstract
Results of study of the neutron irradiation effect on pure copper at 340°C are presented. Neutron irradiation, resulting in accumulation of 2 appm of helium (experimentally measured) is shown to cause an appreciable reduction of high-temperature ductility of pure copper at testing temperatures up to 300°C. The SEM and optical microscopy studies of the fracture surface showed that copper embrittlement was accompanied by a transition to grain boundary fracture.
The mechanism of copper embrittlement is analyzed. The comparison with the results of cyclotron injection of helium shows that helium embrittlement under neutron irradiation at 340°C is considerably more pronounced than in case of cyclotron injection of approximately the same helium concentrations. A disastrous embrittlement of pure copper is attributed to an effective helium accumulation on the grain boundaries (due to entertainment) during a accumulating recrystallization under irradiation.
The conclusion is made that fast helium accumulation and intensive helium embrittlement of pure copper will appreciably reduce the material life time under the thermonuclear reactor ITER operating conditions.