Radon exposure assessment at CIEMAT

Between 2018 and 2020, CIEMAT carried out a campaign to measure the average annual concentration of radon  in ground floors and basements of the buildings at Madrid-Moncloa site. The experimental study was divided in two phases: a previous one of short duration (1 week) of all ground floor and basements locations (1087 rooms in 50 buildings where radon concentration was measured), and another focused on determining the average annual concentration in the rooms with the highest concentrations of radon activity obtained in the short one. At the end of 2020, the average radon annual concentration had been determined  in 235 dependencies. The measurements were carried out using passive detectors based on electrostatic ionization chambers processed with the E-PERM^® system, validated by comparing them with other types of detectors.

To assess the exposure, in addition to the experimental measurements of the average concentration of radon in air, it was necessary to establish the number of people and the time spent by each one at  the workplace, in order to decide whether remedial actions and their type (constructive and/or administrative) were necessary. This set of tasks made it necessary to involve different services of the CIEMAT organization according to so-called “radon protocol”.

The exposure assessment was carried out by applying  two reference levels: 600 Bq m^-3 averaged annual  radon concentration established in IS-33, below which no type of control should be applied (only optimization) and that of 300 Bq m^-3 established in the European Directive which gives priority to optimization above this level and recommends its application even if it is below it.

The results of the measurements together with the occupancy factors at workplace have made it possible to carry out an evaluation of the exposure to radon, identifying the technical and administrative actions to reduce the exposure in the workplace and guarantee compliance with the legislation on exposure to radon.