Studies validating a sodium purification system for fast reactors

Abstract

The sources of impurities entering the sodium in fast reactors were investigated. The analysis showed that oxygen and hydrogen can be removed from the sodium by using cold traps in all operating regimes of a nuclear power plant as well as hot traps. An operating regime preventing hydrogen accumulation in the first-loop cold trap is proposed for a system purifying the first two loops. A computer code for calculating the impurity mass transfer is perfected. Test calculations showed that the procedure developed and the code are both serviceable. The deviation of the computational results from the experimental data is about 30% on average. For a built-in purification system, it is essential to develop a cold trap with a large impurity capacity. It is shown on the basis of experiments that such cold traps can in principle be developed. Thermohydraulic and mass-transfer codes must be developed in order to realize this possibility.Sodium-coolant purification systems in nuclear power plants with fast reactors must provide the required purity in all operating regimes taking account of all sources of impurities and must have the capacity required to handle the impurities accumulating in the purification system (it is permissible to replace the elements of the system during purification but the number of such replacements must be minimal). When significant contamination is present (routine maintenance, refueling, and accidental contamination), their capacity must ensure that impurities will be removed from the coolant as quickly as possible before the power reaches the operating level and the accumulation of suspensions in the first loop must be prevented.At the present stage of development of nuclear power, considering that safety, cost-effectiveness, and environmental compatibility must be improved, the requirements for the equipment in a nuclear power facility have been raised. Specifically, it has been decided that all systems with radioactive sodium be placed inside the reactor tank. This limits the dimensions of the first-loop systems. Therefore, the positive experience gained in placing purification systems outside the reactor tank cannot be fully utilized.For optimization, the purification characteristics were analyzed for the first loop. The analysis is based on evaluating the possible sources of impurities: their composition, amount, and rate of flow into the coolant in all possible operating regimes of a nuclear power plant. The relationship between the first-and second-loop purification systems and their effect on the distribution of impurities and the possibility and desirability of using not only cold traps but also other methods of purification, for example, hot traps, the structural implementation of the purification system, and the operation regime were all examined.The sources of impurities in systems with sodium coolant are oxygen, hydrogen (determining amount by mass and volume), products of corrosion of the structural materials, tritium, cesium if fuel-elements become depressurized, gaseous fission prod...

Conceptual issues of the cold filter trap development for the sodium coolant purification in fast-neutron reactors

“…A computational model has been proposed for the thermal hydraulics and mass transport of impurities in the cold trap which is based on approximating the incompressible multi-component environment and makes it possible to simulate global spatial distributions of the coolant velocity fields, the temperatures of the coolant and structural components, and the transported impurity concentration distribution. The TURBOFLOW (Kozlov et al 2012, Kalyakin et al 2014 and MASKA-LM (Sorokin and Trufanov 2017, Alekseev et al 2015a, 2015b) codes were used. At the present time, the first 3D code version has been built for the mathematical simulation of the intrap processes (Alekseev et al 2017).…”

“…The goal is to improve the trap in terms of safety, cost effectiveness and environmental friendliness. The first versions of such traps have been developed (Kozlov et al 2012, Alekseev et al 2013, Kalyakin et al 2014. For the initial consideration, argon has been selected as the coolant for the trap cooling.…”

Development of a transfer model for the design and the operation of sodium purification systems for fast breeder reactors

“…Moreover, these pollutants, at very high contents, could also deposit as sodium hydride and oxide on the cold walls of the circuit, which may lead to the plugging of the narrowed sections or the reduction of heat transfer coefficient in heat exchangers. Recently, Kozlov et al quantified the source of impurities entering the sodium in a fast reactor in all operating regimes of a nuclear plant. Thus, by decreasing oxygen and hydrogen content in sodium coolant, a cold trap appears as a major component in a Sodium Fast Reactor.…”