Several methodologies for radon concentration measurements have been used for monitoring
radon in homes and workplaces to minimize health hazards due to indoor radon
exposure. One of them is the Nuclear Track Methodology (NTM), commonly used for passive
long-term measurements. The LR-115 type II (cellulose nitrate), as an NTM’s detector,
is often located inside a diffusion chamber. The set formed by the detector and the chamber
hereinafter will be called a monitor. Commercial monitors, e.g., RadOUT , Radosys, NRPB,
are routinely used for radon measurements; they are calibrated in Certified and/or Accredited
Laboratories. However, many laboratories have developed their own monitors, varying some
characteristics as geometric shapes, dimensions, and material properties. They also do not
have access to calibrate them in Certified and/or Accredited Laboratories. In the present
thesis, we studied the detector response given the characteristics of the diffusion chamber that
we use, and to know how these characteristics influence radon measurements. The results of
this study can provide a fast-calibration of the detector that can be compared to calibrations
in Certified and/or Accredited Laboratories. This study is based on Monte Carlo methods
that imitate the experimental procedure commonly-used in estimating the calibration factor.
This calibration method is more accesible than calibrations performed in Certified and/or
Accredited Laboratories due to its low cost, feasibility and applicability. For these purposes,
a monitor (LR-115 + a non-commercial diffusion chamber made of polypropylene -usually
used as cosmetic pot-) was used in this research. LR-115 detector response in this set-up is
reported by taking into account the geometric shape, dimensions and material (conductive
or non-conductive) of the chamber, the transmission factor (the ratio of final steady state
concentration of radon or thoron at the entrance of the chamber to the concentration of radon
or thoron just inside this entrance), radon exposure level, and etching and reading process.
Regarding the level of radon exposure, it was possible to correct the track overlap effect
for high exposure levels, as can occur in radon measurements in soil pores, by applying a
mathematical model. Mainly, these researches show that a non-commercial monitor can
work as well as commercial ones. Besides, using an LR-115 in bare mode exposed by
unconventional exposition results in concentric ring-shaped tracks, caused by UV natural
radiation. The repeatability and reproducibility of the observed phenomenon were experimentally demonstrated. We also studied the ability of the LR-115 detector to register alpha
particles from nuclear (n,α) reactions, or radon/thoron progeny. This study is also based
on Monte Carlo methods and can provide an estimation of the efficiency of the detector to
neutron or radon/thoron progeny.
| Identifer | oai:union.ndltd.org:PUCP/oai:tesis.pucp.edu.pe:20.500.12404/21205 |
| Date | 17 December 2021 |
| Creators | Bertin Andrés, Pérez Ancaya |
| Contributors | López Herrera, María Elena |
| Publisher | Pontificia Universidad Católica del Perú, PE |
| Source Sets | Pontificia Universidad Católica del Perú |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess, http://creativecommons.org/licenses/by-nc/2.5/pe/ |
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