PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY
Series: Nuclear and Reactor Constants

since 1971

Русский (РФ)

ISSN 2414-1038 (online)

BROND-3.1

ISSUES

2024 Issue 3

STUDY OF THE EFFECTIVENESS OF LITHIUM HYDROXIDE USING FOR HIGH TEMPERATURE pHT CONTROL AT THE SUPERCRITICAL COOLANT

STUDY OF THE EFFECTIVENESS OF LITHIUM HYDROXIDE USING FOR HIGH TEMPERATURE pHT CONTROL AT THE SUPERCRITICAL COOLANT

EDN: EEZIMU

Authors & Affiliations

Kharitonova N.L.
National Research Nuclear University Moscow Engineering Physics Institute, Moscow, Russia

Kharitonova N.L. – Leading Researcher, Cand. Sci. (Tech.). Contacts: 31, Kashirskoe shosse, Moscow, 115409. Tel.: +7 (499) 324-77-77; е-mail: This email address is being protected from spambots. You need JavaScript enabled to view it..

Abstract

The article is devoted to the calculation of the high-temperature pHt in aqueous solutions of lithium hydroxide under conditions of supercritical parameters of pressure and temperature. The concept of maintaining the water-chemical regime of the primary coolant of “classical” VVER/PWR power units involves operating in alkaline conditions by dosing potassium/lithium hydroxide depending on changes in the concentration of boric acid in order to minimize corrosion and the transfer of corrosion products. Using the example of lithium hydroxide (LiOH), the article examines the possibility of properly regulating the acid-base properties of the coolant by dosing alkali in near- and supercritical regions for VVER-SCP nuclear power plants. The pHT values of dilute aqueous solutions of LiOHaq are calculated at a pressure of 25 MPa depending on the density of H2O in the temperature range from 100 to 600 °C, and LiOHaq concentrations from 10–6 to 1–3 mol/kg. For these conditions, the degree of LiOHaq dissociation was also calculated depending on the H2O density. The values of the dissociation constant of LiOHaq at elevated temperatures and pressures are taken based on an analysis of published experimental and evaluated calculation data. It was found that at a H2O density below 80 kg/m3 (temperature above 540 °C at 25 MPa) for LiOHaq concentrations from 10–6 to 10–3 mol/kg, the pHT values in the LiOH–H20 system and in pure H2O are practically the same, and LiOHaq is almost completely in an associated state. Therefore, under these conditions, due to weak dissociation of LiOHaq, pHT control is practically impossible. Dosing LiOH into the coolant will ensure the pHt control at temperatures below ≈ 400 °C for 25 MPa. The results obtained are in good agreement with the conclusions of previously published work.

Keywords
supercritical water cooled reactor, safety, water coolant, VVER-SCP, high-temperature hydrogen index pHt, ion product of water, water chemistry, lithium hydroxide, concentration, experimental data, electrolytic dissociation, physical and chemical properties of water coolant

Article Text (PDF, in Russian)

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Problems of Atomic Science and Technology. Series: Nuclear and Reactor Constants, 2024, no. 3, 3:12