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Reference irradiation of crowd-monitoring area dose-rate measurement systems

20.12.2019

Within the scope of Preparedness, an EMPIR project, the usability of dose‑rate data made available by non‑governmental open‑access networks has been analyzed. On the websites of such networks, measurement data recorded by individuals by means of simple electronic systems or mobile telephones (the latter devices have simple additional modules in some cases) is sometimes published in real time.

Since the Fukushima nuclear disaster in Japan, the field of so‑called non‑governmental tracking of ionizing radiation has grown rapidly around the world and may continue to grow with the expansion of personal interconnected electronic devices. If a dangerous amount of radioactive material is released due to (for example) an accident in a nuclear power plant or a terrorist attack, the dose‑rate information disseminated widely by a large number of civilians must be considered from two points of view: On the one hand, the availability of large quantities of data can be useful for radiation protection when deciding on and coordinating appropriate countermeasures. On the other hand, metrologically unreliable data from simple, privately operated electronic devices provided to the public and the media by non‑state networks can set off unfounded panic and undermine the trustworthiness of state institutions. For society at large, the psychological side effects of this may potentially be serious and damaging. An intercomparison measurement conducted at PTB with over 64 representative dose‑rate measuring devices shows that these instruments can track small changes in the dose rate under natural ambient radiation. However, because the values measured by most devices are too low, an analysis using additional testing data is planned in order to determine whether this shortcoming can be overcome by means of suitable calibration.

Fig.: Measurement setup for testing dose‑rate measuring instruments used in networks of non‑governmental monitoring of ionizing radiation. The gamma‑photon source is located in the middle of a circle at a height of approx. 1 m above the ground. The testing devices are arranged in a circle with a radius of 5 m. The different sources (137Cs, 60Co, 226Ra) extend automatically, allowing dose rates of different radiation quality to be generated over an adjustable period of time at the exposure‑rate measurement devices' location. In this way, the passage of a corresponding radioactive cloud is simulated.