Low Radon Cleanroom for Underground Laboratories

Abstract

Aim of a low radon cleanroom technology is to minimize at the same time radon, radon decay products concentration and aerosol concentration and to minimize deposition of radon decay products on the surfaces. The technology placed in a deep underground laboratory such as LSM Modane with suppressed muon flux and shielded against external gamma radiation and neutrons provides “Zero dose” space for basic research in radiobiology (validity of the LNT hypothesis for very low doses) and for the fabrication of nanoelectronic circuits to avoid undesirable “single event effects.” Two prototypes of a low radon cleanroom were built with the aim to achieve radon concentration lower than 100 mBq·m3 in an interior space where only radon-free air is delivered into the cleanroom technology from a radon trapping facility. The first prototype, built in the laboratory of SÚRO Prague, is equipped with a standard filter-ventilation system on the top of the cleanroom with improved leakproofness. In an experiment, radon concentration of some 50 mBq·m−3 was achieved with the filter-ventilation system switched out. However, it was not possible to seal the system of pipes and fans against negative-pressure air leakage into the cleanroom during a high volume ventilation with the rate of 3,500 m3·h−1. From that reason more sophisticated second prototype of the cleanroom designed in the LSM Modane uses the filter-ventilation system which is completely covered in a further improved leakproof sealed metal box placed on the top of the cleanroom. Preliminary experiments carried out in the SÚRO cleanroom with a high radon activity injection and intensive filter-ventilation (corresponding to room filtration rate every 13 s) showed extremely low radon decay products equilibrium factor of 0.002, the majority of activity being in the form of an “unattached fraction” (nanoparticles) of 218Po and a surface deposition rate of some 0.05 mBq·m−2·s−1 per Bq·m−3. Radon exhalation from persons may affect the radon concentration in a low radon interior space. Balance and time course of the radon exhalation from the human body is therefore discussed for persons that are about to enter the cleanroom.

First transcriptome profiling of D. melanogaster after development in a deep underground low radiation background laboratory

“…The complete elimination of the radon component from natural background radiation can be achieved in the future with special experimental setups for deep underground biological studies such as low radon cleanrooms with special air filtration systems etc. [ 37 ].…”

Urine metabolomics analysis of sleep quality in deep-underground miners: A pilot study

“…In recent years, the study of the biological impact of deepunderground laboratories has received increasing attention from international research teams (9,25,(36)(37)(38)(39). This study attempts to reveal the potential effects related to sleep quality a DUvsG refers to the group "Deep-underground vs. ground, " GSQvsPSQ refers to the group "Good sleep quality vs. poor sleep quality".…”

“…In previous questionnaire surveys of miners in deep-underground wells, we noticed that 68-76% of miners complained about sleep disorders (23,24), which was notably related to complicated underground environmental factors. The underground environmental traits include low background radiation, high temperature, high humidity, high atmospheric pressure, high carbon dioxide concentration, distinctive rock composition (high radon concentration) (1,2,25), and lower oxygen concentration (26), and may also involve environmental microorganisms (27,28) or other unknown features. Other reports about sleep disorders in miners also confirmed our findings (29)(30)(31).…”

A new ultra low-level HPGe activity counting setup in the Felsenkeller shallow-underground laboratory

“…In order to minimize the impact [14,25] of the remaining radon on the background rate of TU1, an airtight antiradon box has been installed. The box is constructed from acrylic glass and flushed with radon-free nitrogen from the boil-off of the HPGe dewar, monitored by a bubbler.…”