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Title: A radon progeny deposition model

Abstract

The next generation low-background detectors operating underground aim for unprecedented low levels of radioactive backgrounds. Although the radioactive decays of airborne radon (particularly {sup 222}Rn) and its subsequent progeny present in an experiment are potential backgrounds, also problematic is the deposition of radon progeny on detector materials. Exposure to radon at any stage of assembly of an experiment can result in surface contamination by progeny supported by the long half life (22 y) of {sup 210}Pb on sensitive locations of a detector. An understanding of the potential surface contamination from deposition will enable requirements of radon-reduced air and clean room environments for the assembly of low background experiments. It is known that there are a number of environmental factors that govern the deposition of progeny onto surfaces. However, existing models have not explored the impact of some environmental factors important for low background experiments. A test stand has been constructed to deposit radon progeny on various surfaces under a controlled environment in order to develop a deposition model. Results from this test stand and the resulting deposition model are presented.

Authors:
 [1];  [1];  [1];  [1];  [2]
  1. Los Alamos National Laboratory
  2. MIT
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1042977
Report Number(s):
LA-UR-10-07980; LA-UR-10-7980
TRN: US1202974
DOE Contract Number:
AC52-06NA25396
Resource Type:
Journal Article
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; AIR; BACKGROUND RADIATION; CLEAN ROOMS; DEPOSITION; HALF-LIFE; PROGENY; RADIATION DETECTORS; RADON; SIMULATION; SURFACE CONTAMINATION; SURFACES

Citation Formats

Rielage, Keith, Elliott, Steven R, Hime, Andrew, Guiseppe, Vincente E, and Westerdale, S. A radon progeny deposition model. United States: N. p., 2010. Web.
Rielage, Keith, Elliott, Steven R, Hime, Andrew, Guiseppe, Vincente E, & Westerdale, S. A radon progeny deposition model. United States.
Rielage, Keith, Elliott, Steven R, Hime, Andrew, Guiseppe, Vincente E, and Westerdale, S. 2010. "A radon progeny deposition model". United States. doi:. https://www.osti.gov/servlets/purl/1042977.
@article{osti_1042977,
title = {A radon progeny deposition model},
author = {Rielage, Keith and Elliott, Steven R and Hime, Andrew and Guiseppe, Vincente E and Westerdale, S.},
abstractNote = {The next generation low-background detectors operating underground aim for unprecedented low levels of radioactive backgrounds. Although the radioactive decays of airborne radon (particularly {sup 222}Rn) and its subsequent progeny present in an experiment are potential backgrounds, also problematic is the deposition of radon progeny on detector materials. Exposure to radon at any stage of assembly of an experiment can result in surface contamination by progeny supported by the long half life (22 y) of {sup 210}Pb on sensitive locations of a detector. An understanding of the potential surface contamination from deposition will enable requirements of radon-reduced air and clean room environments for the assembly of low background experiments. It is known that there are a number of environmental factors that govern the deposition of progeny onto surfaces. However, existing models have not explored the impact of some environmental factors important for low background experiments. A test stand has been constructed to deposit radon progeny on various surfaces under a controlled environment in order to develop a deposition model. Results from this test stand and the resulting deposition model are presented.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2010,
month =
}
  • The next generation low-background detectors operating underground aim for unprecedented low levels of radioactive backgrounds. Although the radioactive decays of airborne radon (particularly {sup 222}Rn) and its subsequent progeny present in an experiment are potential backgrounds, also problematic is the deposition of radon progeny on detector materials. Exposure to radon at any stage of assembly of an experiment can result in surface contamination by progeny supported by the long half life (22 y) of {sup 210}Pb on sensitive locations of a detector. An understanding of the potential surface contamination from deposition will enable requirements of radon-reduced air and clean roommore » environments for the assembly of low background experiments. It is known that there are a number of environmental factors that govern the deposition of progeny onto surfaces. However, existing models have not explored the impact of some environmental factors important for low background experiments. A test stand has been constructed to deposit radon progeny on various surfaces under a controlled environment in order to develop a deposition model. Results from this test stand and the resulting deposition model are presented.« less
  • In evaluating the hazards from indoor {sup 222}Rn, it is imperative that the behavior of the four short-lived particulate progeny are fully understood since they are the radioisotopes that deliver most of the radiobiological damage to occupants. One known characteristic of these radon progeny is that they deposit (plate out) onto macroscopic surfaces. Some of these plated-out atoms become resuspended when they disintegrate and decay to the next progeny, in particular, {sup 218}Po. Both of these mechanisms, plateout and resuspension, affect the airborne population of the individual daughters and their impact on the radiation energy delivered to the human respiratorymore » system. There are two specific and separate areas of concern, One is that monitoring {sup 222} Rn levels alone, such as with charcoal canisters, is obviously not sufficient to determine the radiation dose since the daughters are never in absolute equilibrium with {sup 222}Rn. Further, from an internal dose standpoint, the {open_quotes}unattached{close_quotes} fraction (free ions) of the daughters are believed, by virtue of their deeper tissue depositions in the tracheo-bronchial tract, to deliver the greatest dose in the body. Currently, there are virtually no data on the measurements of both plateout rates and resuspension factors for specific individual residential material surfaces. This report presents experimental data of plateout rates in an indoor house for typical indoor materials. Results of measurements of resuspension factors for some of the materials are provided.« less
  • Indoor air contamination by radon and its decay products is currently the focus of considerable attention and is considered by many to be the greatest potential cause of lung cancer in the human environment next to smoking. The bifurcations of the human respiratory tract are regions in which enhanced local deposition of particles (hot spots) can occur. These hot spots are important in estimating the risk from radon exposure but existing mathematical models do not characterize them accurately. In this study, radon progeny in the molecular size range were sampled through an aluminum model of a lung bifurcation. The parentmore » and secondary tube diameters used correspond to the third and fourth generations in Weibel`s lung model. Steady state, nominally laminar flows were used in the study. Deposition was measured along the inside, outside, top, and bottom walls of the secondary tubes. Experimental results indicate that the deposition along the inside wall is noticeably higher than that along the other walls. The results also show that along the inside, top, and bottom walls the deposition has its overall maximum at the carina. Other maxima are also observed along the secondary tubes downstream from the carina. 44 refs., 4 figs., 2 tabs.« less
  • Energy deposition and cellular radiation effects arising from the interaction of single {sup 218}Po and {sup 214}Po alpha particles with basal and secretory cell nuclei were simulated for different target cell depths in the bronchial epithelium of human airway generations 2, 4, 6, and 10. To relate the random chord lengths of alpha particle tracks through spherical cell nuclei to the resulting biological endpoints, probabilities per unit track length for different cellular radiation effects as functions of LET were derived from in vitro experiments. The radiobiological data employed in the present study were inactivation and mutation (mutant frequency at themore » HPRT gen) in V70 Chinese hamster cells and inactivation and transformation in C3H 10T1/2 cells. Based on computed LET spectra and relative frequencies of target cells, probabilities for transformation, mutation, and cell killing in basal and secretory cells were computed for a lifetime exposure of 20 WLM. While predicted transformation probabilities were about two orders of magnitude higher than mutation probabilities, they were still about two orders of magnitude lower than inactivation probabilities. Furthermore, transformation probabilities for basal cells are generally higher than those for secretory cells, and {sup 214}Po alpha particles are primarily responsible for transformation in bronchial target cells.« less
  • Measurements of radon progeny in the attached-to-aerosol and unattached-to-aerosol states were made in central New Mexico. Simultaneous measurements of attached and unattached progeny at 0.2 and 2 m were carried out over a range of meteorological and terrain conditions. The ratio of the average progeny concentrations at 2.2 to 0.2 m was 1.06 for total progeny and 1.35 for unattached progeny, indicating a net downward flux, with the unattached progeny dominating removal to the Earth`s surface. Progeny/parent activity ratios greater than 1 were clearly detected (for example, at 0.2 m, the average {sup 214}Pb/{sup 218}Po ratio was 1.43 {+-} 0.10),more » providing partial support for some previous observations. A two-particle-size model for radon progeny is able to account for the observed gradients, progeny/parent activity ratios greater than 1, and some trends in the experimental measurements as a function of meteorological conditions. 32 refs., 7 figs., 4 tabs.« less