Irradiation test and PIEs for developing neutron absorbing and burnable poison materials

摘要

Dy_(x)Ti_(y)O_(z) and Gd_(x)Ti_(y)O_(z) have been developed as neutron absorbing and burnablepoison materials. The thermal conductivity of Dy_(x)Ti_(y)O_(z) and Gd_(x)Ti_(y)O_(z) was obtained indirectly from measurements of the thermal diffusivity, specific heat capacity and density. The thermal conductivity of Dy_(x)Ti_(y)O_(z) remains constant over a temperature with a value of 1.5 W/m-K. On the other hand, the thermal conductivity of Gd_(x)Ti_(y)O_(z) depends on the temperature with a minimum value of 1.0 W/m-K. Themo-mechanical analysis was performed to ensure the integrity of the experiments during the in-pile test. The estimated centerline temperature of the Dy_(x)Ti_(y)O_(z) and Gd_(x)Ti_(y)O_(z) was lower than the melting temperature and the stress in the cladding is much lower than the value that would produce any severe problem in the cladding. For a feasibility study of their application to the neutron and burnable absorbing material, the Dy_(x)Ti_(y)O_(z) and Gd_(x)Ti_(y)O_(z) were irradiated in the HANARO reactor located at KAERI and then their PIEs were performed to evaluate the in-pile behaviors. The irradiation test was successfully performed for 46 EFPD. The PIE results proved they maintained their geometrical and microstructural integrity during the irradiation. The EPMA measurements manifest the local non-uniformity of Gd or Dy due to the presence of the two stoichiometric phases. An inductively coupled plasma mass spectrometry (ICP-MS) confirmed a higher depletion rate in Gd_(x)Ti_(y)O_(z) than in Dy_(x)Ti_(y)O_(z). The irradiation and PIEs confirmed the applicability of Dy_(x)Ti_(y)O_(z) and Gd_(x)Ti_(y)O_(z) for neutron absorbing and burnable poison materials.