In the framework of the research project focused on studies of material properties of recent and advanced zirconium alloys, which are used as nuclear fuel claddings in pressurized water reactors, the third material cluster assembly (MCA) was successfully cut off this spring 2020 during an outage of Temelín NPP Unit 1.
The international project which is implemented by our company in close cooperation with Temelin NPP, SC TVEL, ÚJV Řež, a.s., Research Centre Řež, s.r.o. (CVŘ) and Škoda Nuclear Machinery, consists of several parts. One of them is focused on the investigation of radiation-induced growth and microstructural changes of Zr-based alloys under their irradiation, and it is realized for our long-term partner, Bochvar Research Institute of Inorganic Materials (VNIINM) in Moscow. The second part focuses on the evaluation of mechanical properties and modeling of irradiated fuel cladding behavior under its performance under dry long-term storage conditions. These activities are part of the international „TIRCLAD“ project led by our company.
The separated ampoules, which were irradiated at the Temelín NPP Unit 1 reactor core for three irradiation cycles, were transported to the hot cells of ÚJV Řež for their post-irradiation material evaluation. As a part of our activities performed during an outage of Temelin NPP Unit 1, radiation-induced growth of four remaining MCAs was also measured using the methodology proposed by ALVEL. The knowledge of radiation-induced growth is crucial not only for the correct setting of the ampoules’ separation device (POMA) but also for verifying/refining the correlations of radiation-induced growth model of the materials used during operation of the Temelín NPP reactor (VVER-1000 type).
The whole operation took place according to a planned schedule. The separation of the material ampoules was performed by Temelin NPP staff using the equipment supplied in 2014 by our company.
Meanwhile, the analyses and material tests of the first two batches of ampoules and material samples, which were separated in Temelin NPP last year, have been carried out in the hot cells of ÚJV Řež and CVŘ.