How did the nuclear power plant in Japan explode?

Answer 1

The reactors in Japan did a marvelous job holding up to the earthquake that shook the area. As far as we can determine, the reactors did withstand the earthquake and went into a "SCRAM" mode immediately after the event. Shutting down any device that makes this much energy though is not an instant event. Large amounts of heat were still present and water was being used to cool the systems down when the second (unexpected in pre planning) event occurred. A large wall of sea water some 23 to 30 feet tall came and washed out all standby electrical equipment and made cooling the reactors impossible. This event caused the reactors to become very hot and the explosion reduction equipment did not have power to operate.

Nuclear reactors have three containment areas. The first is a center shell that seals the reactor and (normally) all radiation in this dome. This contains the center core of the reactor.

The second chamber is a large cement dome that would normally contain any radiation and prevent an explosion from the outside, from reaching this core. This unit also appears to have withstood the earthquake.

The outer chamber contains a larger area that should capture small amounts of anything that breeches the first two dome. This section also contains little spark plug like units on the ceiling. These help prevent hydrogen, a natural byproduct of the reactor, from building up too much on this ceiling (Hydrogen is lighter than air). These "spark plugs" regularly snap to create a small hydrogen reaction and prevent enough hydrogen from building up and creating a big bang. These units failed to spark due to a lack of electric power.

The lack of power created no way to reduce the heat in the chamber, which in turn produced more hydrogen. The hydrogen built up until a major explosion occurred. The outer containment section was destroyed in these blasts. It is possible (and likely) that the second containment domes were also breached in some of these explosions. This would cause some leakage of the steam inside the reactor which is trying to help cool the reaction. Venting of the dome is also possible to prevent the dome from exploding or cracking. This is a controlled vent, which is different from a leak, as it is needed to prevent a Chernobyl style event.

Currently, two reactors have been restarted. These reactors are being used to drive pumps which are adding seawater to the damaged reactors. We hope this will reduce the core temperatures enough to prevent further venting of the reactors. Time will tell.

There are three absolute failures in the design of the reactors here.

1. No reactors should EVER be built on (or even near) a fault line.

2. Reactors should never be operated near populated areas.

(Indian point reactor in New York City is 30 miles from downtown Manhattan)

3. Standby generators should be placed underground in blast proof areas, like in the U.S.A.

Answer 2

The reactors blew up because of your mom