Effect of solution concentration on ethylene propylene diene monomer (EPDM) nonmetallic components used in caustic liquid waste transfer lines

The hose-in-hose transfer lines (HIHTL) used to transfer waste at the United States Department of Energy's Hanford Site Tank Farm are fabricated from an ethylene propylene diene monomer (EPDM) synthetic rubber. During waste transport, these hoses are exposed to several stressors including caustic solutions at high temperatures and high pressures, as well as 13 and gamma radiation. The aging behavior of HIHTL and dog-bone shaped EPDM specimens were evaluated by exposure to solutions at 77 degrees C containing 0.00, 6.25, 12.50, and 25.00 % (v/v) sodium hydroxide (NaOH) for 12-months. After the exposure, the material properties of the specimens were measured and compared to the unaged samples. The material properties evaluated included the tensile strength of the EPDM dog-bone samples and the burst pressure of the HIHTL. Both the tensile strength of the EPDM dog-bone samples and the burst pressure of the HIHTL specimens exposed to the 6.25 % NaOH solution exhibited the most significant deterioration and those exposed to 25.00 % NaOH solution had the least deterioration. Examination of the HIHTL and the EPDM dog-bone specimens with scanning electron microscopy showed that the deterioration for the specimens exposed to 6.25 % NaOH solution were the most severe and the samples exposed to 25.00 % NaOH solution had the least deterioration.

Automated summary

The hose-in-hose transfer lines used to transfer waste at Hanford Site Tank Farm are made of EPDM synthetic rubber and exposed to various stressors. The aging behavior of EPDM specimens and HIHTL was evaluated by exposing them to different concentrations of NaOH solution. The specimens exposed to 6.25% NaOH solution showed the most significant deterioration, while those exposed to 25.00% NaOH solution had the least deterioration.