In a special edition of Elements journal that covered the one-year anniversary of the Fukushima Daiichi nuclear accident, CISAC Stanton Nuclear Security Fellow Edward Blandford and Joonhong Ahn outline the factors that led to the meltdown: site selection, hazard assessment and site preparation, approaches to managing risk, and reactor design. The paper analyzes how the earthquake and tsunami unleashed a chain of events that eventually led to the meltdown and release of radioactive material.