A fundamental contemporary theory, the Leishear explosion theory, explains major explosions at Three Mile Island and Fukushima Daiichi. Focusing on the Fukushima Daiichi explosions as well as many small nuclear power plant explosions, auto-ignited explosions hammered the largest seismic response at Unit 1 on Mar. 12, 2011. At Unit 3 on Mar. 14, a visibly larger explosion ignited with an observed fireball and smoke cloud but lower seismic forces. On Mar. 15, a Unit 2 reactor system explosion ignited hydrogen in the Unit 4 reactor building to cause damages following ignition, and seismic responses were negligible. Note that a Unit 2 reactor building explosion did not occur, and this fact is questionably attributed to the destructive removal of one of the walls of Unit 2 due to the earlier Unit 1 explosion. All of these explosions were ignited by fluid transients that exploded flammable hydrogen that was created during nuclear reactor core meltdowns, which were initiated by loss of power due to a tsunami. The conclusions presented here build upon earlier publications, where fluid transients auto-ignite hydrogen to explode buildings. In addition, research from Argonne National Laboratory provides background to explain this common cause for nuclear power plant explosions. Although different than the Argonne report conclusions, conclusions here are consistent with observations provided by the Argonne report. New ideas challenge existing beliefs, but the stakes are high since nuclear reactor safety is important to prevent loss of life and catastrophic environmental damages. The next nuclear power plant explosion can be stopped!