Summary On March 28, 1979, the Unit 2 reactor at Three Mile Island in Pennsylvania suffered what would become the most serious accident in U.S. commercial nuclear history — a partial core meltdown. It began with something that looked routine: a secondary cooling pump tripped. But a small mechanical fault — a pressure relief valve that stuck open — allowed coolant to escape. In the control room, operators were faced with confusing, incomplete data. They believed the system had

Stuff goes wrong—missed hand-offs, fuzzy briefs, tech hiccups. We don’t hide it; we learn from it. ICAM gives us a clean way to do that without blame. We collect the facts (timeline, artefacts, short interviews) and map them to four buckets: Absent/Failed Defences (A/FD):  What barrier was missing or didn’t work? Individual/Team Actions (I/TA):  What people did, saw, or assumed in the moment. Task/Environmental (T/EC):  Conditions, tools, constraints that shaped the work. Org