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How was the Fukushima accident similar in severity to the Chernobyl disaster?

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earthquake damage, Honshu, Japan, 2011 — Japan earthquake and tsunami of 2011 Aerial view of damage to a portion of the northeastern coast of Honshu, Japan, following the offshore earthquake and resultant tsunami there on March 11, 2011.

The Fukushima accident and the Chernobyl disaster are both classified as Level 7 "major accidents" on the International Nuclear and Radiological Event Scale (INES), the highest level on the scale. This classification indicates that both events involved a major release of radioactive material with widespread health and environmental consequences, necessitating the implementation of planned and extended countermeasures.123

While they share this severity rating, the circumstances of the disasters differed significantly. The Chernobyl disaster in 1986 was largely attributed to human error and design flaws during a reactor experiment, which led to a massive explosion and fire that released radioactive material directly into the atmosphere. In contrast, the 2011 Fukushima accident was triggered by a massive earthquake and subsequent tsunami, which disabled the plant's power supply and cooling systems, resulting in partial meltdowns. Despite these different origins, both sites required the establishment of nuclear exclusion zones due to the ongoing dangers of radiation.45623