[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.

[mrschwabe]

Thanks for the headsup - but there's nothing wrong with some competition and not to mention getting more coverage; for example it doesn't look like they have any data near the coast of Fukushima preficture which is the most important spot. Also the monitoring does not appear in realtime and if we are getting nitpicky there are certainly a few UX issues with how the data is presented.

On a related note, I'm sure Ken Buesseler is a good guy and his site is nice and I have nothing bad to say about him; I don't know him - but you can find comments about him from people who claim he's a "nuclear shill" and so regardless as a matter of principal it would be prudent to get more independent researchers involved in gathering data.

[gh02t]

> but you can find comments about him from people who claim he's a "nuclear shill" and so regardless as a matter of principle it would be prudent to get more independent researchers involved in gathering data.

You can also find a large number of people on the Internet who claim Obama is a lizard alien (http://www.ibtimes.co.uk/polling-theory-embarrassment-453096). This comparison is hyperbole, I know, but his data and methodologies are peer-reviewed and support his claims. He's far from the only person studying the issue, it's a hot topic (pun intended) https://scholar.google.com/scholar?hl=en&q=fukushima+radiati... .

[SapphireSun]

I think the exact position of the dumping matters though. Unless the ocean is well mixed, the concentration will not be uniformly distributed. For instance, the entire stream might stay integrated as it travels along deep ocean currents (not saying that's actually the case by any means).

[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).

[mrschwabe]

Ok, thanks for clarifying. I guess that ups the challenge quite significantly.

Your research sounds interesting and vitally important - the kind of work that could help save lives even; at least warn people of nearby dangers. Do you have anything public on it?

[gh02t]

Nope, still in development. It'll be freely available once it is. My work wouldn't make a particularly good read anyway as it's intended for a specialist audience and the mathematics get pretty involved.

For radiation detection in general though, probably the most approachable introduction is this book http://www.amazon.com/Techniques-Nuclear-Particle-Physics-Ex... . You can find a free PDF copy if you google around a bit.

[mrschwabe]

Cool thanks and goodluck with your project.