Kinetics of Radiation-induced Cr(II) and Cr(III) Redox Chemistry in Molten LiCl-KCl Eutectic

Journal Article · Sun Mar 03 23:00:00 EST 2024 · Physical Chemistry Chemical Physics. PCCP

DOI:https://doi.org/10.1039/d4cp04190a· OSTI ID:2529388

Iwamatsu, Kazuhiro ^[1]; Holmbeck, Gregory ^[2]; Ramos-Ballesteros, Alejandro ^[2]; Castro Baldivieso, Stephanie ^[2]; Conrad, Jacy K. ^[2]; Woods, Michael E. ^[2]; Phillips, William C. ^[2]; Laverne, Jay A. ^[3]; Pimblott, Simon M. ^[2]; Wishart, James F. ^[2]

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1. City University of New York (CUNY), NY (United States). Hunter College; Brookhaven National Laboratory (BNL), Upton, NY (United States)
2. Brookhaven National Laboratory (BNL), Upton, NY (United States)
3. University of Notre Dame, IN (United States). Notre Dame Radiation Laboratory (NDRL)

Chromium (Cr) is a frequent constituent of the metal alloys proposed for molten salt nuclear reactor (MSR) applications, and is typically the least noble metal ion present. Consequently, chromium is preferentially corroded into molten salt solutions. Here, the redox poise and redox cycling of chromium ions in the salt can greatly influence its corrosivity towards structural alloys, ultimately impacting the longevity of MSR systems. Radiation-induced chemistry is expected to play a significant role in determining the chromium oxidation state distribution during MSR operations. In the present research, electron pulse radiolysis techniques were employed to characterize the reactivity of Cr(II) and Cr(III) ions with primary radiolysis products in molten lithium chloride–potassium chloride (LiCl–KCl) eutectic over a temperature range of 400–600 °C. Both chromium oxidation states were found to rapidly react with the primary products of molten chloride salt radiolysis, i.e., the solvated electron (e_S^-) and the dichlorine radical anion (Cl₂˙^-). For reactions with the e_S^-, second-order rate coefficients (k) of k = (4.1 ± 0.2) and (6.1 ± 0.3) × 10¹⁰ M^-1 s^-1 at 400 °C for Cr(II) and Cr(III), respectively, were determined. Temperature-dependent measurements allowed for the derivation of activation parameters for electron capture by Cr(II) and Cr(III). Both chromium ions also react with Cl₂˙^-, k = (7.2 ± 0.3) and (1.4 ± 0.1) × 10⁹ M^-1 s^-1 at 400 °C for Cr(II) and Cr(III), respectively.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division (CSGB)
• Grant/Contract Number: SC0012704; AC07-05ID14517
• OSTI ID: 2529388
• Report Number(s): BNL--227628-2025-JAAM
• Journal Information: Physical Chemistry Chemical Physics. PCCP, Journal Name: Physical Chemistry Chemical Physics. PCCP; ISSN 1463-9076
• Publisher: Royal Society of Chemistry
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
Molten salts
radiation chemistry