THE HYDROGEN (H2) ECONOMY REQUIRES THE PRODUCTION, STORAGE, AND DELIVERY OF H2 ON DEMAND TO CONSUMERS. DELIVERY CAN BE IN VARIOUS MODES, SUCH AS TANKER TRUCKS, RAIL, AND PIPELINES. PIPELINES ARE OFTEN THE MOST ECONOMICAL AND PROVIDE THE OPPORTUNITY TO DELIVER LARGE QUANTITIES SAFELY. COMPARED TO NATURAL GAS (NG) TRANSPORTATION, H2 POSES NUMEROUS CHALLENGES. FIRST, HIGHER VOLUMES ARE NEEDED FOR THE SAME AMOUNT OF ENERGY—THE VOLUMETRIC ENERGY DENSITY OF H2 IS ABOUT THREE TIMES LESS THAN METHANE (THE PRIMARY CONSTITUENT OF NG). ADDITIONALLY, H2 MAY LEAK MORE EASILY THROUGH PIPE JOINTS AND OTHER CONNECTIONS, CAUSING POTENTIAL SAFETY ISSUES. FURTHERMORE, ADSORBED HYDROGEN INTO PIPES AND PIPELINE COMPONENTS MAY ALSO DETERIORATE MATERIALS AND INCREASE THE LIKELIHOOD OF FAILURE COMPARED TO NG. ONE WAY TO OVERCOME THESE CHALLENGES MAY BE TRANSPORTING H2 WITH A BLEND OF NG IN EXISTING PIPELINE INFRASTRUCTURE, AS IDENTIFIED IN THE U.S. NATIONAL CLEAN HYDROGEN STRATEGY AND ROADMAP. HOWEVER, THIS ''BLEND'' STRATEGY POSES NEW CHALLENGES, INCLUDING FURTHER QUESTIONS OF FLOW OPERATION AND MATERIAL DURABILITY IN PIPELINE SYSTEMS. SUBSTANTIAL RESEARCH EFFORTS ARE ADDRESSING THESE CHALLENGES AND QUESTIONS, INCLUDING DOE'S HYBLEND INITIATIVE, LAUNCHED IN 2020, AND DOE'S HYDROGEN MATERIALS COMPATIBILITY CONSORTIUM (H-MAT), LAUNCHED IN 2018. TO DATE, MORE RESEARCH HAS FOCUSED ON STEELS, WHICH ARE TYPICALLY FOUND IN TRANSMISSION PIPELINES. HOWEVER, ABOUT HALF OF THE PIPELINE MILES IN THE COUNTRY ARE POLYETHYLENE (PE), TYPICALLY USED IN DISTRIBUTION PIPELINE SYSTEMS IN POPULATED AREAS WHERE FAILURES MAY BE MORE CATASTROPHIC. FROM THE BODY OF RESEARCH, THERE ARE NUMEROUS OPEN QUESTIONS ABOUT THE FLOW OF BLENDED NG+H2 AND THE SUBSEQUENT MATERIAL DURABILITY OF PE FOR PIPELINE SYSTEMS. THIS PROJECT WILL ADDRESS THREE OVERALL RESEARCH QUESTIONS. TO THE KNOWLEDGE OF THE INVESTIGATION TEAM, THIS PROJECT WILL BE THE FIRST TO WORK WITH LIVE/DYNAMIC FLOW OF NG+H2 BLENDS TO STUDY FLOW BEHAVIOR AND MATERIAL DURABILITY (IN CONTRAST WITH STATIC/CLOSED VESSELS). ADDITIONALLY, IT WILL BE THE FIRST TO INVESTIGATE THE DURABILITY OF HEAT FUSION JOINTS IN PE PIPELINES FOR DISTRIBUTION IN POPULATED AREAS. 1. CONSIDERING THE EFFECTS OF FLUID ACCELERATION, HOW DOES THE FLOW OF MIXTURES OF NG+H2 BLENDS INFLUENCE FLOW BEHAVIOR AND OVERALL TRANSPORTABILITY? 2. WHAT HAPPENS TO PE WHEN EXPOSED TO H2 AND NG+H2, AND WHY DOES THE BLEND OF NG+H2 ATTACK THE PE FASTER THAN 100% H2 FOR DIFFERENT RESIN FORMULATIONS (FIGURE 1)? 3. WHAT IS DIFFERENT ABOUT THE CHEMICAL COMPOSITION (INCLUDING OXIDATION), MOLECULAR BONDING, AMORPHOUS/CRYSTAL STRUCTURE, AND MECHANICAL BEHAVIOR OF PE IN A HEAT FUSION JOINT VERSUS PIPE BULK BEFORE AND AFTER EXPOSURE TO NG+H2 AND H2?