(106f) C3 Arsine Bed Incident

In 2023, Operations steamed out the adsorbent in an MAPD Arsine Bed, resulting in an unexpected temperature increase. Operations removed the steam, purged the bed with nitrogen, and cooled the bed to ambient temperature. The bed was then flooded with water, and a strong hydrogen sulfide odor filled the air. Operations measured 50 ppm of hydrogen sulfide near the control room and reported visible emissions coming out of the bed. After hooking up a nitrogen truck to the bed and obtaining acceptable LEL/H₂S readings, contractors completed an inert unloading of the adsorbent.

A few years earlier, the site had changed the type of adsorbent in the bed to achieve longer runtimes on the arsine beds in between changeouts. The new adsorbent had lasted for about two years. The previous adsorbent had needed to be changed every three to six months. Following the incident, the site worked with the adsorbent manufacturer to investigate what caused the temperature excursion and what caused the hydrogen sulfide emissions and visible emissions.