Chemcomex (Czechia)

During the years 1970–80’ in the satellite countries of the former Soviet Union more than 24 new reactor builds were started. In the former Czechoslovakia, the new builds were realized with a high degree of input from the local engineers and the local industry. This territory up to today has an indigenous nuclear industry, machinery and nuclear engineering background. Starting with the year 1972, on the territory of Czechoslovakia (now on the territory of the Czech and Slovak Republic) 12 new units of the VVER-440 type of reactors were started to build. Nowadays the 2 oldest units were already shutdown in Slovakia, 4+4 units are still operating in both countries, and 2 units of VVER-440 model V213 are still under construction in Slovakia. The reactors designed lifetime in original configuration are 30 years. During these units’ operation period, wide range of modifications and upgrades were performed to strengthen the nuclear safety and the reactors operability. In 2015/16, activities related to the unit operation licenses extension were carried out in both of countries. In scope of strengthening the reactor’s core monitoring and surveillance, at Dukovany NPP (CZ, 1998) and at Bohunice NPP (SK, 2001) the original Russian VK3 computation system was completely replaced with an alternative advanced Core Monitoring and Surveillance System (CMS) SCORPIO-VVER. In Hungary, a locally developed “Verona”, and on the units under construction in Slovakia the Russian “Kruiz” CMS is used. Nowadays the SCORPIO-VVER CMS presents a nuclear fuel type and fuel vendor independent, advanced computer based reactor core monitoring system with an open and flexible framework, including the latest achievements in the fields of N/F and T/H for reliable and safe reactor operation with high efficiency of fuel cycle. The system’s framework governing the know-how and knowledge of 5 European institutes with proven experiences with reactor operation, fuel pattern and fuel campaign design and with utilizing the existing unit’s project reserves to increase the reactor operation and fuel campaign efficiency. Since the first installation the SCORPIO-VVER CMS system has a remarkable operating history and experience. More than 18 years of experiences at 6 units of VVER-440 type of reactors in two different countries helps to put the system to a very high level of usability and reliability. Even if the SCORPIO-VVER is installed only on VVER-440 reactors, it could be adapted to the needs of other VVER type of reactors and to needs of education and training centers too.

Stabilization/solidification is used for liquid waste processing. For the purpose of liquid and solid phase separation the experimental vibration separatory apparatus is designed. It can be used with common cement mixer and easily transported by means of the car trailer. The device is equipped with vibration motor and it is designed as hand-operated.

The pseudobinary Zr1Nb–O phase diagram was recently estimated at the Czech research institute UJP using a new experimental procedure. It is based on the oxygen distribution measurement inside fuel claddings previously exposed to high-temperature steam environments, assuming equilibrium conditions being fulfilled at the phase boundaries. The experimental results agreed satisfactorily with the CALPHAD approach, and a further experimental program followed to affirm the phase diagram. This paper is concerned with additional measurements of the oxygen concentrations using wavelength-dispersive spectrometry, secondary ion mass spectrometry, and inert gas fusion techniques and examination of the microstructure in the Zr1Nb cladding wall after high-temperature oxidation. The main goal was to check the validity of the recently proposed Zr1Nb–O phase diagram, or to refine it. The new results of the oxygen concentration measurements confirmed the phase diagram. After that, a new diffusion model, the Jakub Krejci oxidation model, was created using the Zr1Nb–O phase diagram describing the double-sided high-temperature oxidation of the Zr1Nb fuel cladding including the (α + β)-Zr layer. The numerical calculations were compared to the experimental results with satisfactory agreement. It could be concluded that the proposed experimental procedure provided a good estimation of the Zr1Nb–O phase diagram. Moreover, it can be used for alloys containing a greater amount of hydrogen. The Zr1Nb–O phase diagram may be applicable for oxygen diffusion models predicting the oxidation behavior of Zr1Nb fuel claddings upon high-temperature oxidation.