Environmental radioactivity monitoring networks

In our country, the control of environmental radioactivity is regulated by Legislative Decree no. 101/2020 and subsequent amendments. The Ministry of the Environment and Energy Security exercises control over environmental radioactivity, while the Ministry of Health exercises control over food and beverages for human and animal consumption.

The complex of controls is divided into national and regional surveillance networks. The regional networks are managed by the individual Regions. The national networks are the National RADIOACTIVITY SURVEILLANCE NETWORK – RESORAD, the automatic networks with ISIN emergency alarm functions (REMRAD and GAMMA) and the alarm network managed by the Ministry of the Interior. To these must be added the local surveillance networks of environmental radioactivity of nuclear plants, managed by the operators of the plants themselves, over which ISIN carries out the institutional control function.

RESORAD uses the radiometric surveys and measurements of the regional and provincial agencies for environmental protection (ARPA/APPA) and other suitably equipped bodies, institutes and organizations such as the Experimental Zooprophylactic Institutes.

ISIN performs the technical coordination functions of RESORAD, provides for the collection and dissemination of the results of the measurements carried out, manages the new SINRAD web portal (National Information System on Radioactivity) which includes a specific section containing the data on environmental radioactivity produced by RESORAD, which are annually transmitted to the European Commission in compliance with current legislation and the Euratom Treaty.

The main objective of the network is to monitor the space-time trend of radioactivity in the matrices of the various environmental and food sectors according to Guidelines that take into account the European Commission Recommendation 2000/473/Euratom.

In June 1998, the Italian national network was able to detect, through the recording of an anomalous presence of radioactivity in the air, an accident at the Spanish foundry in Algeciras, where a source of Cesium-137 was melted. In March 2011, RESORAD detected the first traces of radioactivity in the environment, Iodine-131 in atmospheric particulate matter, following the accident at the Fukushima nuclear power plant (Figure 2) and was the only one, due to analytical sensitivity, able to provide data in environmental and food matrices in the days following the event.

In order to ensure the homogeneity of the detections, sampling and measurement methods, the RESORAD Network Manual was developed, which collects all the information on the structure, sampling plans, sampling and measurement methods and the data flow of the network itself. In addition to the manual, further reference documents, survey results and guidelines are available on issues concerning the protection of the population from exposure to ionising radiation.

Figure 2 - Trend of the concentration of Iodine-131 activity in atmospheric particulate matter following the accident at the Fukushima nuclear power plant

The GAMMA network, currently undergoing technological renewal and updating, consists of 64 stations for determining the environmental dose equivalent rate, located throughout the country. These stations continuously measure radioactivity in the air, providing a radiological value averaged over ten minutes and over the hour, which is transmitted, displayed and saved in real time on the ISIN Control Center. About half of the stations have spectrometric as well as dosimetric capabilities, integrating an inorganic scintillator of the CeBr3 or LaBr3 type and reaching sensitivities of less than 10 nSv/h (Figure 3). Each station is equipped with a rain reading system, in order to correlate any radiometric anomalies to natural variations in the environmental background. The high sensitivity combined with the speed of response and the radionuclide identification capabilities make these stations a valid tool to support decision-making choices in the first phase of any radiological and nuclear emergencies.

I dati della rete GAMMA sono anche condivisi con la Commissione Europea ed inviati alla piattaforma di scambio dati EURDEP (European Union Radiological Data Exchange Platform).

Figure 3 - Example of dosimetric (left) and spectrometric (right) probe of the GAMMA network

The REMRAD network, also undergoing technological modernization, consists of 6 stations installed in strategic points of the national territory and ensures air monitoring through the deposition of gaseous particulate matter that is aspirated onto a large filter. The filter measurement is carried out in two different phases. The first phase consists of a measurement in "continuous" mode, during air sampling, by means of a scintillation detector and the second phase consists of a measurement in "delayed" mode 24 hours after the end of sampling, in order to minimize the contribution of natural radionuclides, by means of a hyperpure germanium detector of the BEGe (Broad Energy Germanium) type. The very high sensitivity is guaranteed by the high sampling rate, about 500 m3 h-1, for a sampling time of 24 hours and allows to report every minimal radiometric anomaly present within the air masses that cross our country.

These stations, taking up the configuration already used by the CTBTO (Comprehensive Nuclear-Test-Ban Treaty Organization) within its monitoring network, have an innovative feature consisting precisely in the measurement system in "continuous" mode that was designed on the basis of an industrial invention patent developed entirely within the ISIN.

Another peculiarity of these stations is that in case of emergency it is possible to remotely change the configuration of the measurement procedure to have rapid results that are essential to direct decision-making choices in the first moments of the emergency situation.

Figure 4 - REMRAD Station

ISIN annually publishes a report on the national networks for monitoring environmental radioactivity.