The
gripping drama that unfolded during this month last year filled headlines and
news hours all across the world. On March 11th last year, a huge earthquake and tsunami left more than 20,000 people
dead or missing in eastern Japan. Amidst
widespread destruction, the tsunami slammed into the Fukushima Daiichi Nuclear
Power Station, disabling cooling systems and leading to fuel meltdowns in three
of the six nuclear units. As invariably
occurs, after a few months the media coverage moved on, even though countless
problems remain unresolved.
So why hasn’t
the radiation washed away or faded into neutrality? This same query has plagued eastern Europeans
for over 25 years as they continue to deal with heightened radiation levels
stemming from the Chernobyl disaster. The answer is that radioactive materials
released into the environment in both of these catastrophes are extremely finely
dispersed and will last for decades. In
fact, just controlling the spread of radiation has become higher priority than
cleaning up the mess in many cases.
In a nutshell,
radioactive elements are unstable atoms. They seek stability by giving off
particles and energy—ionizing radiation—until the radioisotope becomes stable.
This process occurs within the nucleus of the radioisotope, and the shedding of
these particles and energy is commonly referred to as ‘‘nuclear
disintegration.’’ During their disintegration, most radioactive elements
morph into yet other radioactive elements on their journey to becoming lighter,
stable atoms. Some of the morphed-into elements are much more dangerous than
the original radioisotope, and the decay chain can take a very long time1. This
is the reason that radioactive contamination has a variable lifespan, depending
on the composition of the radioactive material. For more information on this
topic, see this post on radioactive lifespans.
The most common contamination
radionuclides in the Japanese crisis are cesium-134 (with a half-life of 2
years) and cesium-137 (with a half-life of 30 years). Radiological risk assessment expert John Till,
president of the U.S.-based Risk Assessment Corporation, says the fallout will
probably be gone from the surface of plants within a few years, but attach
strongly, through ion exchange, to soil — in particular to the clay soils
common throughout Fukushima2. From there, the rate and risk level at which cesium
will move into plants is still unclear.
And the oceans are a different matter: sediment levels and changing
currents make radioactive duration almost impossible to estimate.
 |
| Japanese soldiers collect contaminated leaves near the Fukushima nuclear power plant in December. source |
All of this
information adds up to the need for sustained radiation observation. In particular, on-going dose rate
measurements are essential to avoid overexposure to people, animals, and crops. Since much of the radiation is mobile, weather
changes can cause radiation levels to rapidly fluctuate. This is a common occurrence in Japan, where
after a rain storm brings down radioactive particles, the sun and wind can
produce radioactive dust clouds that travel in unpredictable ways. The mobility of these radioactive particles
requires constant monitoring to warn people and keep them indoors on increased
risk days.
Not only do these
detectors need to consistently and accurately make measurements, they also need
to efficiently relay information to analysis locations. A self-healing mesh network is ideal for this
kind of seamless measurement and communication.
This kind of network routes around disabled detectors and can
incorporate new detectors at any location in the network. The Rad-DX, D-tect’s newest addition, operates
on the D-tect SensorNet – a mesh network with these capabilities. To learn more about the SensorNet, visit this page.
Although the
cleanup in Japan may take decades, conditions are steadily improving. With careful and constant radiation
monitoring and improvements to safety standards, future risks may be mitigated.
____________________________________________________________________________
D-tect Systems is a
supplier of advanced radiation and chemical detection equipment sold around the
world. www.dtectsystems.com. 
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