The sequence was merciless. By 18:00 on March 11, the falling water level in Reactor 1 reached the fuel rods. Operators attempted to restart the emergency cooling system at 18:18 -- it did not function. At 15:36 the next afternoon, a hydrogen explosion blew apart the Unit 1 reactor building, injuring five workers and destroying the mobile generator and cabling that crews had just connected to Unit 2. TEPCO headquarters ordered plant director Masao Yoshida to stop seawater injection into Reactor 1 at 19:25 that evening; Yoshida refused and ordered his workers to continue. On March 14 at 11:01, a second hydrogen explosion destroyed the Unit 3 reactor building, injuring 11 more workers. By the morning of March 15, a third explosion had damaged Unit 4, and a majority of the fuel in Reactor 2 had dropped to the bottom of its pressure vessel. Radiation readings spiked to 400 millisieverts per hour near Unit 3.

With the reactor buildings shattered and cooling systems destroyed beyond repair, the response became improvisational. On March 17, Self-Defense Force helicopters made four water drops onto the spent fuel pools of Units 3 and 4, measuring a radiation field of 3.75 sieverts per hour above Unit 3. Police and fire trucks attempted to spray water with high-pressure hoses. The Tokyo Fire Department dispatched 30 fire engines and 139 firefighters, including a truck with a 22-meter water tower. Russia flew in two 95-ton concrete boom pumps aboard Antonov An-124 cargo planes from Atlanta and Los Angeles; TEPCO purchased each for two million dollars, and they could be operated by remote control from two miles away. A 62-meter pumping truck donated by Chinese manufacturer SANY joined the effort. Fresh water arrived by barge from the US Navy's Yokosuka base, towed to Fukushima by the Japan Maritime Self-Defense Force.

The true extent of the damage emerged over weeks and months. On May 12, TEPCO confirmed that a full meltdown had occurred in Reactor 1, with fuel having fallen to the bottom of the containment vessel. On May 24 -- the eve of an IAEA delegation's arrival in Tokyo -- the company admitted that reactors 2 and 3 had also melted down. Reactor 3 took roughly 60 hours to melt; Reactor 2 about 80. Plutonium was detected in soil samples collected March 21-22, and by early April, iodine-131 levels in seawater near the plant had reached 7.5 million times the legal limit. On April 11, authorities raised the rating to Level 7 on the International Nuclear and Radiological Event Scale, recognizing that by March 15 the plant had already released the equivalent of 190,000 terabecquerels of radioactive iodine into the atmosphere.

The crisis did not end with cold shutdown, declared on December 16, 2011. It shifted underground. In July 2013, the Japanese government admitted that radioactive water had likely been leaking from the plant into groundwater and the ocean since the initial meltdowns. Caesium levels in monitoring wells spiked 90-fold in a matter of days. In August 2013, 300 tonnes of highly contaminated water leaked from a storage tank, prompting regulators to raise the incident to INES Level 3. TEPCO coated 70,000 square meters of ocean seabed with concrete in 2012 and another 180,000 square meters in 2014 to contain contaminated sediments. A 780-meter underground ice wall was completed in 2015 to redirect groundwater flow. Trade minister Toshimitsu Motegi eventually took charge of the water situation, declaring that TEPCO had 'essentially turned it into a game of Whack-a-Mole.'

The innermost reaches of the damaged reactors remained too radioactive for human access for years. In April 2015, a robot sent into Reactor 1 to locate melted fuel covered 14 of 18 survey locations before ceasing to function and being abandoned. In February 2017, TEPCO measured 530 sieverts per hour inside the Reactor 2 containment -- a lethal dose in seconds -- and discovered a two-meter hole in the metal grating beneath the pressure vessel. In July 2017, a remotely operated vehicle captured the first images of Reactor 3's melted core: material hanging from the control rod mechanism and piles of rocky debris on the containment floor. In February 2018, a two-fingered robot made first physical contact with fuel debris in Reactor 2, successfully nudging loose material at seven of ten test points. The full retrieval of melted fuel is not expected to begin until the 2020s, with decommissioning projected to continue through approximately 2052.