Izvestiya vuzov. Yadernaya Energetika

The peer-reviewed scientific and technology journal. ISSN: 0204-3327

Generation of Hydrogen by Hydroheterogenic Compositions based on Aluminum and Alkaline Metals

3/18/2021 2021 - #01 Nuclear power plants

Askhadullin S.R. Milinchuk V.K.

DOI: https://doi.org/10.26583/npe.2021.1.05

UDC: 629.9+544(075)

The process of hydrogen formation and the associated risk of combustion and explosion is a complex problem in the hydrogen and radiation safety of nuclear reactors. Lithium, potassium and sodium hydroxides are used in VVER reactors as corrective additives to maintain the pH of the aqueous coolant with boric acid at a controlled level of 5.8 – 10.3 by removing the passivating layer of aluminum oxide Al2O3 from the surface. In this process, the most reactive are lithium hydroxides, the reactions of which with the formation of hydrogen proceed at a high rate at room temperature (in an exothermic mode). The processes of hydrogen generation in hydroheterogeneous compositions with potassium and sodium hydroxides proceed at an acceptable rate when heated to ~ 60 °C. The kinetics of hydrogen generation depends in a complex way on the boric acid content, namely, at a low concentration of 0.01 – 0.05 g/l, the yield of hydrogen is at a level of ~ 1000 ml, and at a concentration of 0.6 g/l, no hydrogen is formed. According to the quality standards of the coolant in the hot state of a VVER-1000 power unit or in the reactor state at the minimum controlled power level, the total concentration of alkali metals is about 1 mg/ dm3, i.e. two to three orders of magnitude less than in the compositions we have studied. The discovery of the influence of alkali metal hydroxides on the formation of hydrogen with the participation of structural materials using the example of aluminum suggests that the hydroxides of these metals present in a coolant in a small amount can also take part in the hydroheterogeneous process of the formation of small amounts of hydrogen. The possibility of generating hydrogen along this path must be taken into account in the long-term operation of nuclear reactors, accidents and incidents at nuclear power plants.

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water hydrogen aluminum aluminum oxide boric acid lithium hydroxide potassium hydroxide sodium hydroxide hydroheterogeneous composition hydrogen and radiation safety of nuclear reactors