What types of radioactive material was in the water in Japan after the nuclear power plant explosion thingy?

Question:

What types of radioactive material was in the water? (e.g. Was it radioactive metals, gases, or liquids? Did it have gamma rays, alpha rays, or that other kind of rays?)

Answer:

About 80% iodine-131 (half life of eight days) and about 20% cesium-137 (half-life 30 years). These are radioactive elements. (the terms metal, gas, and liquid don't really apply). Unlike Chernobyl, no actual fuel was released from the reactors because of the better design of the Fukushima reactors.

The explosions were caused by vented hydrogen (e.g. they were not nuclear explosions--a nuclear power plant can't explode in the atomic bomb sense). These explosions occurred outside the containment vessel so they only damaged the buildings' outer walls, which are not part of the containment system.

Radiation consists of various rays (alpha, beta, gamma, etc.). Note that the radiation level has been trending down (not that there was all that much to begin with). The biggest amount of radiation leakage came from the dumping of the low contaminated water:

"According to the TEPCO Press Release of 4 April, approximately 10 000 T of water from the radioactive waste treatment plant and 1 500 T of subsurface waters stored in the sub drain pits of Unit 5 and 6 are being discharged to the sea to provide room to store water with higher levels of radioactivity in a safer manner. TEPCO has estimated that these discharges would increase the effective dose to a member of the public by 0.6 mSv, if he/she were to eat seaweed and seafood from 1 km from the discharge point every day for a year. It should be noted however that the movements of all ships, including fishing boats, are restricted within a 30km zone from the NPP." --IAEA

0.6 mSv is the same amount of radiation you would get from 7.5 round-trip flights from New York to LA.

Here is an informative article describing the situation:
http://bravenewclimate.com/2011/03/13/fu…

And here is where you find current, factual status information:
http://www.iaea.org/newscenter/news/tsun…
Historical status:
http://www.iaea.org/newscenter/news/2011…

And a slide presentation that describes the effects:
http://www.slideshare.net/iaea/fukushima…

And here is a chart that helps make sense of the numbers:
http://www.xkcd.com/radiation/