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Biomedical subjects

J R Peggie

Publications and source records attributed to J R Peggie.

6 recordsLinked to original sources
PubMed1998

Radon exhalation rates and gamma doses from ceramic tiles.

This study was carried out to assess the possible radiological hazard resulting from the use of zircon in glaze applied to tiles used in buildings. The 226Ra content of various stains and glazing compounds was measured using gamma spectroscopy and the 222Rn exhalation rates for these materials were measured using adsorption on activated charcoal. The radon exhalation rates were found to be close to or less than the minimum detectable values for the equipment used. This limit was much lower than the estimated exhalation rates, which were calculated assuming that the parameters controlling the emanation and diffusion of 222Rn in the materials studied were similar to those of soil. This implied that the 222Rn emanation coefficients and/or diffusion coefficients for most of the materials studied were very much lower than expected. Measurements on zircon powders showed that the 222Rn emanation coefficient for zircon was much lower than that for soil, indicating that only a small fraction of the 222Rn produced by the decay of 226Ra was able to escape from the zircon grains. The estimated increase in radon concentration in room air and the estimated external gamma radiation dose resulting from the use of zircon glaze are both much lower than the relevant action level and dose limit.

Adsorption↗
PubMed1995

Estimates of inhalation doses resulting from the possible use of phospho-gypsum plaster-board in Australian homes.

Current materials used as internal lining in Australian buildings are based on natural gypsum of low radium content. A study was carried out to estimate the contribution to the annual effective dose due to airborne contamination from chemical by-product gypsum plaster-board of higher radium content if it were used as an internal lining. The 226Ra content and 222Rn exhalation rate were measured for several samples of the plaster-board, and the behavior of 222Rn and its progeny (218Po, 214Pb, 214Bi, and 214Po) in a typical building was modeled numerically, using the results of the exhalation rate measurements as input. For building ventilation rates greater than approximately 0.5 air changes per hour, the contribution to the total annual effective dose from inhalation of 222Rn and its progeny exhaled from the phospho-gypsum plaster-board is estimated to be below 1 mSv. This contribution is reduced if the surface of the plaster-board is coated with paint or cardboard, or if the very fine particles are removed from the phospho-gypsum during manufacture of the plaster-board. The effective doses arising from dust generation during the installation of the plaster-board are also estimated to be below 1 mSv. The recommended action level of 200 Bq m-3 for radon in air in Australia corresponds to an annual effective dose of approximately 6 mSv. The study indicates that the suggested acceptable level of 185 Bq kg-1 for the 226Ra concentration in the plaster-board may be too restrictive under Australian conditions.

Air Pollutants, Radioactive↗
PubMed1990

Performance of a diffusion barrier charcoal adsorption 222Rn monitor under conditions of varying humidity and temperature.

An investigation of the performance of a diffusion barrier, charcoal-based 222Rn monitor under several artificial environmental conditions showed that both temperature and relative humidity levels affect 222Rn uptake. A physical model was developed adequately describing the temperature effects, while an empirical model was used to summarize the combined effects of temperature and atmospheric water concentration.

Charcoal↗
PubMed1987

An integrating thermoluminescent Rn daughter personal dosimeter.

An integrating Rn daughter dosimeter using conventional Dy-doped CaSO4 thermoluminescent (TL) material has been developed for use as a personal monitor. The dosimeter was found to have a linear response over the range 0.5 WL-h to 25 WL-h and to be insensitive to the state of equilibrium of the Rn daughters. The use of the dosimeter to monitor both 222Rn and 220Rn daughters is described. The limiting sensitivity of the dosimeter, at a sampling rate of 1 L min-1, was determined to be 0.1 WL-h for 222Rn daughters and 0.5 WL-h for 220Rn daughters. The application of the thermoluminescent dosimeter (TLD) to occupational monitoring of 222Rn and 220Rn daughters is discussed.

Air Pollutants↗
PubMed1980

An iodine-125 thyroid measurement method.

A two-probe technique has been developed to measure 125I in the thyroid. In this technique simultaneous emissions from a source are detected as coincidence events between two probes rather than as a sum peak in a single probe (the sum peak method). The background count rate when counting coincidence events between probes is substantially lower than the background in the sum peak region of a single probe. Theoretical equations which enable the activity of a source to be calculated are given. The applicability of these equations to thyroid measurements has been verified by measuring sources of various sizes, so that the geometric distribution and self-absorption of the sources were varied beyond the limits likely to be encountered in thyroid monitoring. Measurements on a simulated thyroid showed a variation in measured activity from +2% at a 5 cm source-to-detector distance to -4% at 10 cm. Measurements on a simulated thyroid containing 310 Bq (8.4 nCi) for a 500 s counting time gave a standard deviation of 21%. When the activity of the source was increased to 5500 Bq (149 nCi) the standard deviation was 6.2%.

Humans↗