Stress Corrosion Cracking in Zinc-Dosed Primary Water for Rolls-Royce SMR
Case study
Rolls-Royce SMR is designing a Small Modular Reactor (SMR) to deliver a market driven, affordable and low carbon power generation capability. The developed design is based on optimized and enhanced use of proven technologies that presents a class leading safety outlook and attractive market offering with minimum regulatory risk.
The challenge
The design of primary water safety classified components must be robust against potential degradation mechanisms, including Stress Corrosion Cracking (SCC). Therefore, Rolls-Royce SMR is developing a technical justification to demonstrate that SCC in primary water of Rolls-Royce SMR components is minimized so far as is reasonably practicable.
What we delivered
Lucideon worked with Rolls-Royce SMR to determine the influence of zinc in the primary coolant chemistry regime, with the aim to demonstrate that the addition of zinc to Rolls-Royce SMR primary coolant does not accelerate crack propagation when compared to the same chemistry without zinc. Zinc is added to reactor water to minimize the shutdown dose rate.
Lucideon completed two environmentally assisted crack growth rate tests in simulated Rolls-Royce SMR primary water, where an initial crack growth rate without zinc addition was compared to the response after zinc addition. The environment consisted of hydrogenated, high-temperature water with potassium hydroxide (KOH) as an alkalizing agent and no soluble boron. Zinc was added to the water at a concentration which is bounding of anticipated Rolls-Royce SMR operating limits.
One Lucideon test evaluated Environmentally Assisted Fatigue Crack Growth (EAFCG) that involves continuous cyclic loading, with the aim of promoting both stable crack growth and zinc penetration to the crack tip.
A second Lucideon test evaluated the SCC growth rate at constant stress intensity factor (no cycling). Both the SCC and EAF tests were followed by characterization of the zinc level in the oxide of the crack and at the crack tip by X-ray Photoelectron Spectroscopy (XPS). This analysis verifies the incorporation of zinc into the crack-tip oxide and hence evaluates the mechanism by which zinc influences crack growth.
The project concluded that there was no detrimental effect to propagation of environmentally assisted cracking through adding zinc to the chemistry even up to 150 ppb zinc.
Value to the client
Lucideon has extensive state-of-the-art facilities including high design flexibility and that operate at a range of temperatures and pressures.
Lucideon has over 40 autoclave systems with world leading expertise in high temperature water SCC crack growth, SCC initiation, EAF growth rate, tension-compression EAF endurance, JR fracture resistance, and more.