A prototype device has been designed and manufactured for the detection of radon gas, a radioactive gas of natural origin that can be found in the interior spaces of buildings. The new device connects to a wireless network and automatically monitors radon levels in its building environment.
This detection system contains inside a silicon sensor manufactured in the Clean Room of the Barcelona Institute of Microelectronics (IMB), attached to the National Microelectronics Center (CNM), of the Spanish Higher Council for Scientific Research (CSIC).
The prototype, still in the standardization phase, is the result of the Care project, an initiative that has been led by the company Alibava Systems and has had the participation of two public research centers, the IMB and the Galician Institute of High Energy Physics. (IGFAE) of the University of Santiago de Compostela, which has been responsible for carrying out the calibration and validation tests, both in its experimental facilities and in real environments. In addition, three companies participate in CARE, ATI Sistemas SL, Radiansa Consulting SL, Sensing & Control Systems SL.
It is a portable detector, which is plugged into the current and which provides real and periodic measurement through the wireless network to which it is connected. The team has developed a semiconductor sensor for the detection of radioactive elements generated during the decay of radon and a control system capable of providing gas concentration measurements with frequencies lower than half an hour. This is the main novelty. “What most commercial detectors do is average the radon concentration recorded in the preceding 24/48 hours,” says Dolores Cortina, a researcher at the IGFAE. “For this, the implementation of an algorithm adapted to the high capacities of the sensor developed has been key, allowing to combine speed and reliability in the measurement”, he adds.
Silicon wafers manufactured at the Barcelona Institute of Microelectronics. (Photo: IMB-CNM-CSIC)
The IMB has actively participated in the development of the semiconductor sensor that contains the CARE prototype, whose sensitive area has been set at 800 mm2. For optimum sensitivity, it has been covered with 30 silicon sensors with dimensions of 27 mm2. These tablets have been manufactured in the White Room of Micro and Nanofabrication of the IMB, a singular technical scientific infrastructure (ICTS) of the CSIC dedicated to the development and application of innovative technologies in the field of microelectronics.
“The biggest challenge has been integrating the silicon into the heart of the radon detector; the final characteristics of the system depend on its quality, stability and repeatability ”, indicates Salvador Hidalgo, principal investigator of the IMB in the project. “Modular structures consisting of ten silicon detectors have been manufactured, of which three have been used for this prototype, positioned in a novel way. This solution allows us to have a very flexible system, with a quick and easy adaptation depending on the application ”, he adds.
The device will be applied both in public and private buildings once it is approved, both in the domestic sector and in the industrial sector. “It will be marketed in different countries around the world where building regulations require a monitoring system or active control of radon concentration,” says Juan Herranz, director of Alibava Systems and coordinator of the project. “In addition to the possibility of storing data in the cloud, the final device will have communication protocols to communicate with the most widely used intelligent ventilation systems in buildings,” he points out.
Radon is a naturally occurring radioactive gas that can be found in the interior spaces of buildings. It is also the largest source of natural radiation exposure in humans. The World Health Organization (WHO) estimates that 3-14% of lung cancer cases can be attributed to radon based on its concentration. According to a cartography by the Nuclear Safety Council, the geology of places like Galicia, Extremadura or the provinces of Barcelona and Girona means that they have high levels of radon, although the gas can be found in all buildings.
“The radon detectors on the market read passively, but this prototype allows automating the data collection process and the execution of corrective actions”, compares Celeste Fleta, IMB researcher in the project. “The concentration readings are processed in the sensor unit and the results are sent wirelessly to a control center that executes the established security procedures,” he adds about the prototype, which has shown an efficiency “10% higher than current systems ”in the validation phase.
The device provides the ability to have a distributed detection network within the area to be controlled, precisely identifying possible risk areas to be able to take corrective measures in the spaces where it is necessary. It is a real-time monitoring, so the security level is increased.
The Care project (Development of an automatic control system for radon concentration in buildings) has been funded by the Ministry of Science and Innovation of the Spanish Government in the 2016 Call for Collaboration Challenges (RTC-2016-5627-1) . It is an industrial research project to facilitate collaboration and knowledge transfer between public institutions and the company. (Source: Sabela Rey, IMB / CSIC Comunicación)