Reactor #1 now leaking into the Pacific
Quotes Japan's Nuclear Regulatory Agency as saying that Reactor #1 is now probably leaking into the Pacific. The measured radioactivity is 90,000 times above the "safe" level.
More than 60 different radioactive substances are being leaked, including Cs-137.
Here's a little more info beyond what the article provides:
--1 Becquerel (Bq) is just one radioactive decay per second. The article should have stated this. TEPCO measured Reactor #1's water this month (July 2013) to be 900,000 Bq/liter. If you held up a 1 liter bottle of this water, this would be "clicking" a Geiger Counter nearly a million times a second if the Geiger counter recorded all of these decays. (it wouldn't because of positioning and efficiency, but even 10,000 clicks/sec would make a pretty loud scream)
--Cs-137 has a half life of 30 years, meaning that once it gets into the environment it will be over 100 years before it is 90% gone. It is also chemically reactive and the "salts" that it forms dissolve in water, making it difficult to remove. From Wikipedia
Caesium-137 is not widely-used for industrial radiography because it is quite chemically reactive, and hence, difficult to handle. Also the salts of caesium are very soluble in water, and this complicates the safe handling of caesium.
I wish the article provided links to each of the TEPCO and NRA reports. Hopefully these can be found at TEPCO's English website: http://www.tepco.co.jp/en/index-e.html