Howard M. Prichard

Rapid Measurements of 222Rn Concentrations in Water With a Commercial Liquid Scintillation Counter

Abstract A technique is described by which concentrations of 222Rn in water as low as 10 pCi/l can be determined by a 40-min count of a 10-ml sample. Preparation time is about 1 min/sample, and no special equipment is required other than access to a commercial liquid scintillation system.

The technologically enhanced natural radiation environment.

Abstract A new category for human radiation exposure, technologically enhanced natural radiation (TENR), is proposed. The purpose of the new category is to permit clear distinction between truly natural human radiation exposure and exposure which occurs due to alteration of the natural sources by non-nuclear technology. Examples of TENR, such as radium emission from coal fired plants, radon in natural gas, radium in fertilizer, radon in water and enhanced cosmic ray exposure in high altitude aircraft are discussed. It is concluded that creation of the TENR category would be useful because (1) it would facilitate direct comparison of increments to the radiation environment due to nuclear and conventional activities, (2) it would direct research to TENR which would perhaps uncover significant human exposure and (3) it would permit regulatory authorities to control unambiguously TENR exposures without having to decide in each instance whether the exposure was natural or man-made.

An estimate of population exposures due to radon in public water supplies in the area of Houston, Texas.

An estimate of the incremental population lung exposures (WLM) attributable to the domestic use of ground waters containing z2zRn is made for the vicinity of Houston, Texas. Because of the complexity of the water distribution system, extensive water sampling was required to characterize the concentration of radon in the water in various areas. Models describing the transfer of radon from water to indoor air and the resulting indoor concentrations were developed and experimentally tested. Census data on population and housing characteristics were folded into the final model used to compute an annual population exposure of 4000 WLM (approx. 40,000 rem) to the 1.6 million inhabitants of the study area. The resulting estimates are discussed in the context of similar exposures brought about by other technological activities.

A passive diffusion 222Rn sampler based on activated carbon adsorption.

A simple passive sampler for 222Rn with up to 24-hr integration times can be constructed by using a diffusion barrier to regulate the effective sampling rate of an ambient temperature activated carbon bed. The diffusion element serves to make sampler performance relatively independent of the properties of the type of carbon used. Satisfactory results are obtained if the total effective sample volume is kept well below the equivalent air volume of the activated carbon bed. The influence of various temperature and Rn profiles on the samplers performance have been examined by experiment and by simulation. The amount of Rn adsorbed may be measured by gamma spectroscopy, by outgassing into an alpha scintillation flask, or by desorption into a liquid scintillator. In the latter case, a sensitivity of 0.2 pCi l-1 is obtainable for 24-hr exposures.

A solvent extraction technique for the measurement of 222Rn at ambient air concentrations.

The high solubility of radon in cold organic solvents is exploited to extract radon directly from a sample air stream into a hexane-based liquid scintillation solution. Up to 10 l. of air is passed through 20 ml of solvent held at -78 degrees C in a bath of dry ice and acetone. The solvent is then transferred to an ordinary glass liquid scintillation vial that has been preloaded with 2 ml of concentrated fluors. A large number of samples can be prepared in a short time with minimal equipment, making it possible for field workers to conveniently collect numerous samples prior to returning to the laboratory. After allowing an interval of at least 3 hr after processing for radon daughter ingrowth, the vials are counted on an unmodified liquid scintillation system with a narrow window set around the radon and polonium alpha peaks. The large sample volume more than compensates for the relatively high alpha background of liquid scintillators. Relevant theoretical considerations and alternate sampling strategies are discussed.

Radon in the environment

Publisher Summary This chapter focuses on radon present in the environment and describes the radiological properties of the natural radon isotopes. The isotopes of radon and their short-lived daughters are important constituents of the natural radiation environment. The causal chain relating radon concentrations in the environment to lung cancer is long and complicated. Major areas of environmental research include the identification of geological factors associated with high radon levels, the behavior of radon daughters in various aerosol distributions, and the effects of certain architectural factors on radon daughter equilibrium status. The low solubility of radon in water has a number of implications of biological and environmental significance. Surface waters contain far less radon than groundwaters because of radons relative affinity for air. Radon dissolved in the blood rapidly seeks equilibrium with ambient atmospheric radon. Radon can be adsorbed onto various solid sorbents. The lower the temperature, the more efficient the adsorption for a given sorbent. The concentrations of radon that are found in air, water, or other media are dependent on the ability of radon to escape the matrix in which it is formed.