# Modeling of the Passive State of Construction Materials in Small Modular Reactor Primary Chemistry—Effect of Dissolved Zn

## TL;DR

This paper uses a model to study how adding dissolved zinc affects corrosion in materials used in small modular reactor coolants.

## Contribution

A quantitative model is applied to interpret corrosion behavior of reactor materials with zinc addition in coolant.

## Key findings

- The Mixed-Conduction Model explains oxide film behavior on reactor materials with dissolved zinc.
- Zinc addition influences film growth and cation release in boron-free coolant.
- Model parameters are derived from electrochemical and surface analytical data.

## Abstract

The Mixed-Conduction Model for oxide films is used to quantitatively interpret in situ electrochemical and ex situ surface analytical results on the corrosion of AISI 316L (an internal reactor material) and Alloy 690 (a steam generator tube material) in small modular reactor primary coolant with the addition of soluble Zn. The model parameters of alloy oxidation and corrosion release are estimated with the time of exposure up to 168 h and anodic polarization potential (up to −0.25 V vs. standard hydrogen electrode) using fitting of the transfer function to experimental impedance spectra. Model parameters of individual alloy constituents are estimated by fitting of the model equations to the atomic fraction profiles of respective elements in the formed oxide obtained by Glow-Discharge Optical Emission Spectroscopy (GDOES). Conclusions on the effect of Zn addition on film growth and cation release processes in boron-free SMR coolant are drawn and future research directions are outlined.