Study and Prediction of Chlorine Induced Stress Corrosion Cracking

Stainless steel dry storage canisters are used for storage of nuclear waste. Recent work has shown that these containers are susceptible to stress corrosion cracking at the weldments under the chloride containing dust and humidity conditions present underground which is a potentially catastrophic event. Understanding stress corrosion cracking (SCC) in stainless steel dry storage canisters is needed. To ensure their long-term structural health and to design monitoring procedures a good understanding of SCC in stainless steel canisters is necessary. General statement of how this problem is being addressed Understanding of the initiation and progression of chloride-induced SCC is needed to define monitoring programs that ensure safe storage of nuclear waste materials. In this SBIR project TDA will study the evolution of stress corrosion cracking and crack growth rate and develop predictive models that can be coupled with the monitoring data to provide an early alert of SCC. What is to be done in Phase I: TDA Research will study stress corrosion cracking of sensitized AISI SS304 and welded samples of AISI SS304 under the conditions that cause SCC in storage. We will conduct a multifaceted experimental study to understand and characterize sensitized SCC. We will employ prediction/analysis techniques previously used for analogous phenomena to provide a deeper understanding of the SCC process and predict crack formation and growth rate so that appropriate monitoring protocols can be designed. Specifically, we will simultaneously collect acoustic emission (AE), electrochemical noise (EN) and elongation/creep data as a function of time and corrosion conditions to determine how the signal changes as a function of the time evolution of microcracking that leads to fracture. Commercial Applications and Other Benefits The understanding of stress corrosion cracking, its early detection, and the time-failure monitoring approach developed in this project are applicable to not only nuclear waste storage containers but to the austenite stain steel used in chemical and power plants. Stress corrosion cracking can cause a disastrous failure to occur unexpectedly and with minimal overall material loss. Proper monitoring to prevent stress corrosion cracking is of great benefit to public health and safety and to the environment. Key Words: Stress corrosion cracking, nuclear waste, dry storage canisters, sensitization, crack growth rate