|Fig. 1: Safecast DIY radiation detector kit. (Image Source: T. English)|
Measurement of radiation levels is critical in order to evaluate health risks and to enable stakeholders to make informed decisions following a nuclear accident. [1,2] However, access to measurement data may be limited, for example, due to loss of infrastructure from a natural disaster, evacuation, or limited resources. The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident which began on March 11, 2011 provides a recent case study in the adoption of do-it-yourself (DIY) and crowdsourced radiation monitoring. This article explores potential benefits and limitations of crowdsourced radiation measurements which can provide a platform for rapid, local, and independent measurement of radiation levels following a nuclear accident.
Sparse reporting of radiation levels have ignited debate about how best to interpret individual radiation measurements when large sample sizes and information about measurement conditions are unavailable. For example, following the Fukushima disaster, a 20 km exclusion zone was established surrounding the FDNPP. On March 30th 2011, the International Atomic Energy Agency (IAEA) reported a radiation measurement in the village of Iitate 40 km from the power plant which reached 20 MBq/m2. While this level exceeded one of the IAEA's criteria for evacuation by a factor of 2, additional measurements in Iitate fell to 7 MBq/m2 within 2 days. [3,4] The IAEA measurements suggested that a wider evacuation area may have been warranted immediately following the FDNPP accident, however, a more comprehensive spatial and temporal survey of radiation levels was not available.
In another event on August 31st, 2013 more than 29 months after the initial accident, radiation levels of 1800 mSv/h were reported at water storage containers at the FDNPP.  The Tokyo Electric Power Company indicated that radiation levels dropped to 15 mSv/h at a distance of roughly 50 centimeters from a storage tank. However, the details of how the measurements were performed as well as independent measurements of gamma and beta levels were not reported.
These examples highlight the challenges in interpreting radiation measurements in the aftermath of a disaster, especially when the context of the measurement site and instrument details are unavailable. In contrast, DIY and crowdsourced measurements can provide several benefits, especially for initial surveys before 1st responders arrive and long-term measurements after they've left.
For example, measurements of radiation levels immediately following an accident are important to detect peak concentration levels which may include radionuclides with a short half-life. While exposure to radioiodine (I-131) is an important cancer risk factor due to the accumulation of iodine in the thyroid, the half-life of I-131 is 8 hours and response time is important in order to assess exposure and health risks.  Long-term measurements are important to evaluate the evolution of fallout and possible additional releases of radioactive material as cleanup efforts at the FDNPP continue. Furthermore, by crowdsourcing many independent measurements, DIY hardware can decrease the dependence on any one data source while providing wide geographic coverage and redundancy.
Following the nuclear disaster at the FDNPP, several projects were initiated by local communities in Japan to independently measure radiation levels using both scintillation and Geiger-Mueller detectors.  Safecast is one example of a project that leveraged DIY and open source hardware. On June 19th, 2012, a refined version of an open source Geiger counter initially deployed in Japan and capable of measuring alpha, beta and gamma radiation was successfully launched on the crowdfunding website kickstarter. The hardware is based on a LND7317 pancake Geiger tube and is calibrated to Cs137 with a sensitivity of 3340 CPM per mR/hr. The hardware and software designs are free and open source, allowing anyone to build, modify, and improve the design. A typical measurement contains the radioactivity counts per minute, UTC timestamp, location and altitude data from GPS, as well as other metadata.
One potential concern with crowdsourcing is the quality and attribution of user submitted data. While Safecast requires that each data point be associated with a user ID, the user can remain anonymous. Futhermore, tracking the type of tube used for each measurement allows filtering of the data by detector type. One potential benefit of this structure is that data contributed by different hardware and users can be filtered and compared against other crowdsourced measurements, helping to identify erroneous equipment and actors.
In summary, DIY and crowdsourced radiation measurements can provide independent and rapid assessment of radiation levels following a nuclear incident. However, there are still many questions regarding how crowdsourced data can be used most effectively to complement other radiation surveys. Erroneous readings without a large sample size present their own risk if acted upon. Additionally, it may be difficult to assure data integrity and proper operation of DIY hardware in the immediate aftermath of a disaster. In the case of open access and crowdsourced data like Safecast, individuals can evaluate raw data and draw their own conclusions or perform their own measurements to enable informed decision-making following a nuclear accident.
© Tim English. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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