State of Green

With all of the discussion regarding the tritium leaks at Vermont Yankee of late, I found myself wondering what the substance is, exactly.  I assumed it was radioactive, but how harmful is it, in fact?  What are the regulatory limits that define how much is too much?  What exactly happens when it enters our groundwater?

Naturally, I started with Wikipedia, where I quickly found the following information:

The legal limits for tritium in drinking water vary from country-to-country and from continent-to-continent. Some figures are given below.

• Canada: 7,000 becquerel per liter (Bq/L).
• United States: 740 Bq/L or 20,000 picocurie per liter (pCi/L) (Safe Drinking Water Act)
• World Health Organization: 10,000 Bq/L.
• European Union: “investigative” limit of 100 Bq/L.

(A becquerel and a curie, it turns out, are both units of radioactivity, named after Henri Becquerel and Marie and Pierre Curie respectively.  “pico” denotes a factor of 10^-2).

What first jumps out at me is that the limits vary heavily.  And the US standard is extremely far below the WHO limit.  For some reason this surprises me.

So what levels were found at Vermont Yankee?  The Burlington Free Press reports that the most recent find was “1,024 picocuries per liter of tritium” according to VY, and 9,000 picocuries in the previous contaminated well find.  If we compare that to the regulatory limits, we see that as far as picocuries go, the levels don’t seem that high.  Indeed, they are far below “the one with much higher levels — in the millions of picocuries per liter — reported a year ago outside the advanced off-gas building.”

How, exactly, a picocurie compares to a becquerel is a little beyond my limited knowledge of nuclear physics and rudimentary browsing skills – on Wikipedia, of all places, the validity of which is often debated.  I’m also not certain whether the levels found in the wells that are being tested at VY have any correlation to drinking water per se.  Maybe it is “okay” to have high levels in the ground as long as it is dispersed enough before entering the actual drinking water system?  Clearly it is alarming to find anything radioactive in our ground whatsoever.  But while it is a radiation hazard if ingested, Wikipedia, for what it is worth, goes on to state that tritium has “a short biological half life in the human body of seven to 14 days, which both reduces the total effects of single-incident ingestion and precludes long-term bioaccumulation of [tritiated water] from the environment.”

Sure would be nice to have a layman’s explanation for what these tritium findings really mean to the environment and human bodies.  Post a comment if you have any leads.