Sandia doesn’t write codes and standards for the coming hydrogen economy, but if Carmen Mendez has anything to say about it, the Labs will help make those codes better. She and her colleagues will do it using a systematic risk assessment process to address the challenges posed by the new fuel.
“We need to develop a scientific basis for hydrogen risk quantification and use a risk-informed strategy to provide recommendations to code writers,” says Carmen (6861). “We are trying to demonstrate to the codes and standards community that risk-informed decisions can be made.”
“Part of the challenge for us is to get something that the codes and standards writers will treat as realistic,” says Mark Allen, manager of Sandia’s Risk and Reliability Dept. 6861. “It must be a practical alternative if we want our risk approach to influence designs. The codes and standards community doesn’t have to listen, but they will if we have technical answers to their questions.”
“We hypothesize what can cause an accident at the scale of a hydrogen refueling station, but we need to identify the risk drivers,” says Chris Moen (8775), co-manager of the hydrogen codes and standards project at Sandia. “We can identify, quantify, and prioritize the risk drivers using the risk assessment approach. Then we can also address the mitigation strategies for those most likely events.”
“When people go to a gas station, they normally don’t think about the risks,” says Carmen. “However, others have thought of those risks and have put safety measures in effect to protect product users. We want hydrogen to be at least as safe as fueling products that are available now. We want to get to that level with hydrogen refueling. But, instead of doing it as we go along learning from experience, we are trying to understand how to reduce risks before they occur.”
Carmen, who joined Sandia last fall, receives input from an industrial working group, formed by representatives from energy companies and auto manufacturers that provide guidance to DOE on matters of technical interest. Additional industry experts have been brought together to help think through the assumptions being made in creating a risk approach, provide data, and ultimately put the assessment into practice.
The first steps involve studying failure modes (with information provided by industry), understanding the behaviors of the users, and gathering data on the materials and components involved. Data gathering is done in a variety of ways, including comparisons with other available products, such as compressed natural gas, liquefied natural gas, propane, and butane. Because there is not always enough scientific literature on these products, other means are used. “There is always some uncertainty in risk assessment, so we use expert judgment and other quantification alternatives,” says Carmen.
Another source is data from Sandia’s experimental element of the codes and standards project (see “Setting the standards for hydrogen” on page one). “It really comes down to looking at everything that’s available,” says Carmen.