[tptacek]

There are 187000000000000 million gallons of water in the Pacific Ocean, meaning that "radioactive waste" is 2.1 x 10^-10% of the body of water itself.

The waste we're talking about is HTO --- tritiated water --- which is a low-energy beta emitter that has intrinsically low bioavailability, because it is literally just water and is eliminated quickly.

Before developing an opinion about how terrifying this radiation leak is, a good number to have handy --- exercise for the reader --- is over the 12 year half life of tritium, assuming 400 gallons pumped into the ocean every day, for 4384 days, what percentage of the background radiation of the Pacific ocean are we talking about elevating it to?

Another number, which will not make you feel better about the world, is what elevation to background radiation is produced by the coal plants it would take to offset all the power produced by nukes.

Finally: if you believe that HTO leaks from TEPCO are, or are going to be, responsible for mass die-offs of marine life, you're going to have to account for the fact that we basically carpet-bombed the oceans with HTO during the insane nuclear weapons testing of the 1960s; nothing TEPCO is doing will come close.

[mrschwabe]

In an attempt to grasp how toxic the water is, wouldn't it be more effective to measure levels of cesium 137 instead of overall background radiation? I don't care what background radiation the entire Pacific has, I care if the sushi I'm eating has ionized, cancer-causing particles in it.

"Michio Aoyama’s initial findings were more startling than most. As a senior scientist at the Japanese government’s Meteorological Research Institute, he said levels of radioactive cesium 137 in the surface water of the Pacific Ocean could be 10,000 times as high as contamination after Chernobyl..."

http://www.nytimes.com/2014/03/17/world/asia/concerns-over-m...

[tptacek]

Your analysis might confuse two different phenomena.

When you mention TEPCO pouring "400 million gallons" into the Pacific, what you're talking about is them dumping contaminated cooling water from tanks into the ocean. The scale of that dumping is caused by (a) the ongoing need to pump water into the compromised reactor to cool it and (b) the large amounts of water they've already stored. However: that water is also filtered, to remove the (actually dangerous) Sr-90. What's being dumped into the ocean is HTO, not Sr-90 or Cs-137.

On the other hand, the meltdown at Fukushima contaminated the entire area with Cs-137, most of which is in the soil, sediment, and sand. The Cs-137 contamination is much worse than the HTO contamination. However, it is also not ongoing; in fact, increase in cesium detected around the plant has fallen dramatically in the last two years.

[mrschwabe]

Fair enough - though I'm not sure if I will just take your word for it that the potential for new releases of new cesium 137 is not an ongoing threat from Fukushima Daiichi. The only way we can know for sure I suppose, is through the efforts of independent researchers brave enough to get close to the facility.

In the spirit of HN, it would be neat to see an open technology solution for the purposes of monitoring. Ie:

  if(waterSample.cesium137 > 0.001) return ALARM(waterSample)

[gh02t]

> it would be neat to see an open technology solution for the purposes of monitoring

It's trivial to do so. Decay of Cs-137 releases a 662 keV gamma ray that is easily measured and the count rate is proportional to the source activity (or ultimately the total amount of Cs-137 present). You can calibrate an inexpensive NaI detector such that it will tell you how much Cs-137 is in a given volume of water. If you place it next to a pipe that has a constant flow rate, you can infer the average amount of Cs-137 in the liquid flowing through the pipe. It's something that you can build in an afternoon if you know what you're doing and have the equipment.

This is pretty much how they monitor liquids for contamination in a real plant, except they use more detailed spectral measurements to monitor multiple isotopes. If you ever have the rare opportunity to go into a reactor control room, there will be a display somewhere that reads out this exact measurement.

[mrschwabe]

Good info!

If the technology is cheap, as you point out, then the next logical step might be a collaborative project to get a network of inexpensive, miniature, buoyant craft's out to sea - for the purpose of actively measuring levels of cesium 137; sharing these results for everyone to see, to graph, and to check on at any given time of the day.

One-time results from a fish is useful data but to have a whole swarm of devices actively monitoring levels in various locations would be ideal.

Thinking ahead, the next hurdle could be the logistics of internet connection - maybe they could connect to each other in a mesh-network that daizy-chains back to an internet connection closer to shore. Oh, and power (solar panel maybe?). Navigation. Yeah - some challenges for sure, but it all seems within reason.

[slapshot]

Somebody did this. Before the experiment, they expected a background level of Cesium 137 of between 1 and 2 bq/M^3 (caused by 1950s nuclear testing, which released a ton of it). They found actual levels between 1 and 2 bq/M^3 across the Pacific with some small variation above and below: http://ourradioactiveocean.org/results.html

Think about it this way. Worst-case estimates are that 2-4 kilos of Cesium 137 were released. If it all ends up in the ocean, the total Pacific Ocean weighs on the order of 638,000,000,000,000,000,000 kilos. The total new Cesium 137 is: 0.000000000000000000627% of the ocean. At a 30 year half-life, that's one decay event per 70 liters per hour.

[gh02t]

Not going to happen, nor is there much reason to do so. For one, the NaI detectors are relatively inexpensive, but still you're talking about $10K each minimum for such a setup. There are other detectors that would work for this (EJ-309 for instance, you need a detector capable of energy spectroscopy), but they're even more expensive and often extremely toxic. What I was describing is a setup to measure contamination of the water while it's still at the plant.

These sorts of statistics are monitored and the data is available ( http://www.biogeosciences.net/10/6045/2013/bg-10-6045-2013.p... ), but the contamination levels are so low that you have to use a very different method. Basically they go out and collect a bunch of sea water (linked report uses 100 liters), then filter it through a microfilter and the filter, which traps all of the cesium, is measured back in a laboratory using a very sensitive HPGe detector (which cost $100K+ and require cryogenic cooling at all times).

The measured activity levels in that report were in the range of about 1-15 Bq/m^3 of sea water. That's 1-15 atoms disintegrating per second (there's ~10^29 atoms in a cubic meter of water). Those levels are far too low to reasonably measure at sea, end of discussion. Even the highest observed dispersal of about 140Bq/m^3 (which was actually Cs-134 and was in a small area immediately after the disaster) would be very tough to measure in real time like you suggest.

Much more practical is to monitor the rate of dispersal at the outlet (i.e., the pipes pumping water into the ocean at Fukushima) and simulate the fluid dynamics to calculate the dispersal. These results you then validate by comparing to spot measurements taken in the manner described in the linked paper. In fact, this is again exactly what they do. This work is widely published and openly available, but not well known to the general public because it's rather technical. My own research work is on a related subject, but different application (finding the position of a concentrated radioactive source in an urban environment).