Vaclav Dostal

Design of Experimental Loop With Supercritical Carbon Dioxide

Supercritical carbon dioxide (S-CO2) cycles are recently very perspective and are researched all around the world. For successful deployment of these cycles experimental research is necessary. This paper describes the design and research program of S-CO2 experimental loop that was performed in collaboration of the Czech Technical University in Prague (CTU) and the Research Centre Rez i.n.c.. The loop will be constructed at the premises of the Research Centre Rez i.n.c a part of the project SUSEN. This paper particularly focuses on the design of components, their thermotechnical calculations, construction and arrangement of the experimental loop. It also deals with the preparation of experimental measurements to be implemented. The loop is envisioned for the research of the heat transfer for various operating conditions, testing of the material in the environment of S-CO2 and sampling of gas from the loop.Copyright

Study Plan for Material Corrosion Test in Lead and Bismuth Eutectic at High Temperature

A concept of steam lift pump type lead-bismuth cooled fast reactor (SLPLFR) is proposed as high temperature and high efficiency Pb-Bi cooled fast reactors. Fe-Al alloy-surface treated steels and ceramics of SiC, Si3 N4 and SiC/SiC composites have been chosen as candidates of cladding and structural materials, respectively. A corrosion test plan is proposed, where compatibility of steels applied with Al-Fe alloy-surface treatment and the ceramics will be tested in high temperature Pb-Bi flow. A conceptual design of a test apparatus for the corrosion test is provided.Copyright

Study on Liquid Lithium Target System for Boron Neutron Capture Therapy (BNCT)

The concept of the liquid lithium target system for the boron neutron capture therapy (BNCT) using an accelerator was formulated. A lithium flow loop was designed and fabricated for development of lithium jet nozzles that provide a stable lithium plane jet. A water flow loop was designed, fabricated and used for development of lithium jet nozzles. Experiment of water plane jet was conducted to investigate the stability of high velocity plane jets. A large amount of droplets were entrained from the jet surface when the jet was unstable. The jet was observed by being illuminated with a stroboscope. It was found that a stable plane jet was realized by using a nozzle with the gap of 0.5mm and the length of 70mm. It was concluded that a fully developed flow without inlet disturbances at the outlet of the nozzle was required for the stability of the high velocity plane jet.Copyright

QUENCH FRONT PROPAGATION IN THE ANNULAR CHANNEL

Understanding the quench front propagation during bottom core reflooding is crucial for the effective cooling during the LOCA accident. The results presented in this paper were obtained on an experimental loop with an annular test section. The test section consists of a vertical electrically heated stainless steel tube with outer diameter 9 mm and length of 1.7 m. The heated tube is placed inside a glass tube with the inner diameter 14.5 mm. Water mass flux during the reflooding is in the range from 100 kg.m −2 .s −1 up to 140 kg.m −2 .s −1 and the initial wall temperature of the stainless steel tube is in the range from 250 °C up to 800 °C. The presented results show the influence of the initial conditions on the quench front propagation and the complexity of the phenomenon.

Performance test of the air cooled finned-tube supercritical CO2 sink heat exchanger

This technical paper presents results of an air-cooled supercritical CO2 (sCO2) finnedtube sink heat exchanger (HX) performance test comprising wide range of variable parameters (26-166 C, 7-10 MPa, 0.1-0.32 kg/s). The measurement covered both supercritical and subcritical pressures including transition of pseudocritical region in the last stages of the sink HX. The test was performed in a newly built sCO2 experimental loop which was constructed within Sustainable Energy (SUSEN) project at Research Centre Rez (CVR). The experimental setup along with the boundary conditions are described in detail; hence, the gained data set can be used for benchmarking of system thermal hydraulic codes. Such benchmarking was performed on the open source Modelica-based code ClaRa. Both steady-state and transient thermal hydraulic analyses were performed using the simulation environment DYMOLA 2018 on a state of the art PC. The results of calculated averaged overall heat transfer coefficients (using Gnielinski correlation for sCO2 and IPPE or VDI for the air) and experimentally determined alues shows reasonably low error ofp25% and - 10%. Hence, using the correlations for the estimation of the heat transfer in the sink HX with a similar design and similar conditions gives a fair error and thus is recommended.

STUDY OF IDENTIFICATION OF TWO-PHASE FLOW PARAMETERS BY PRESSURE FLUCTUATION ANALYSIS

This paper deals with identification of parameters of simple pool boiling in a vertical rectangular channel by analysis of pressure fluctuation. In this work is introduced a small experimental facility about 9 kW power, which was used for simulation of pool boiling phenomena and creation of steam-water volume. Several pressure fluctuations measurements and differential pressure fluctuations measurements at warious were carried out. Main changed parameters were power of heaters and hydraulics resistance of channel internals. Measured pressure data was statistically analysed and compared with goal to find dependencies between parameters of two-phase flow and statistical properties of pressure fluctuation. At the end of this paper are summarized final results and applicability of this method for parameters determination of two phase flow for pool boiling conditions at ambient pressure.

Accident at Fukushima Dai-Ichi Nuclear Power Plant: Lessons Learned for the Czech Republic

Accident at Fukushima Dai-Ichi nuclear power plant significantly affected the nuclear industry at time when everybody was expecting the so called nuclear renaissance. There is no question that the accident has at least slowed it down. Research into this accident is taking place all over the world. In this paper we present the findings of research on Fukushima nuclear power plant accident in relation to the Czech Republic. The paper focuses on the analysis of human performance during the accident. Lessons learned from the accident and main human errors are presented. First the brief factors affecting the human performance are discussed. They are followed by the short description of activities on units 1–3. The key human errors in the accident mitigation are then identified. On unit 1 the main error is wrong understanding and operation of isolation condenser. On unit 2 the main errors were unsuccessful depressurization with subsequent delay of coolant injection. On unit 3 the main error is the shutdown of high pressure cooling injection system without first confirming that different means of cooling are available. These errors lead to fuel damage. On unit 1 the fuel damage was probably impossible to prevent, however on unit 2 and 3 it could be probably prevented. The lessons learned for the Czech Republic were presented. They can be summarizes as follows: be sure that plant personnel can and knows how to monitor and operate the crucial plant components, be sure that the procedures on how to fulfill the critical safety functions are available in the symptomatic manner for situations when there is no power available at the plant, train personnel for these situations and have sufficient human resource available for these situations.Copyright