Escape Of Radon Research Articles

Beta dose rates derived from gamma spectroscopy and low beta anticoincident system of various environmental materials, mainly of archeoglogical origin

Beta dose-rates (BDR) have been derived from tephras, pumices and pottery of archaeological origin. The BDRs were obtained from two counting systems: (1) gamma spectrometry through appropriate conversion of gamma activity to U, Th, 40K concentration values, and (2) by counting total beta, using a gas-flow sample detector in an anticoincidence mode of counting. Assuming radioactive equilibrium in the U and Th series, the two methods of obtaining BDRs are compared. The degree of disequilibrium, the calibration, and radon escape will be critically considered. The employment of either methods to swift BDR measurements for the TL dating will be discussed. The radioactivity measurements of tephras were used also to provenance those, as Santorini volcano might had not been the only eruption in the Aegean in the 2nd mill. B.C., it might have experienced more than one eruptive phase. BDRs in the samples ranged from 13 to about 470 mrads/year and the agreement between the two methods were in general satisfactory.

Age Dependent Hit Probabilities for Lung Cancer Induction Following Exhalation of Ingested Radon

Abstract Previous calculations of the risk following ingestion of 222Rn (radon) in drinking water have been concerned primarily with the solubilization of the radon in body tissues, followed by in situ decay. Much less attention has been directed towards the escape of radon from lung tissue and blood into the alveolar air, which should lead to doses to lung tissue as the newly formed progeny deposit in lung passages prior to exhalation. The present report details the calculation of hit probabilities to the basal cells of the bronchial epithelium and alveolar cells in various age groups following ingestion of radon in drinking water. Results are compared with those obtained for the in situ decay of radon within the lung mass.

An improved alpha scintillation counting method for determination of Th, U, Ra-226, Th-230 excess, and Pa-231 excess in marine sediments

In a previous paper it was shown that thick-source α counting is a simple means for determining Th, U, Th-230 excess, and Pa-231 excess concentrations, and hence sedimentation rates, for deep-sea sediments. Here it is shown that radon escape can lead to inaccurate results if powdered samples are used and that this problem can be overcome by preparing samples as a borate glass before measurement. Glassed samples also permit a novel measurement of the Ra-226 content by measurement of the post-fusion buildup of Rn-222, a determination shown to be necessary for near-surface sediments that have a deficit of Ra-226. It is also shown that Po-210 is lost during the fusion and that this loss can be allowed for in the calculations.The above observations are found on comparisons of measured and calculated α count rates for several Th and U standards and on comparisons with α spectrometry results from four sets of deep-sea core samples.

Determination of U and Ra in rock samples by gamma-spectrometric method

A gamma-spectrometric method independent of radon escape for the determination of U and Ra in rock samples based on the 63 keV and 1001 keV as well as 185 keV lines is described and discussed. A simple experimental procedure is given for the determination of the self-absorption factor. The method has been applied for the determination of uranium and radium in rock samples from Morocco containing uranium between 17.5 wt.% and 0.026 wt.%. The limits of determination, at 95% confidence level and 10% standard deviation, for the 63 keV and 1001 keV lines were found to be 0.075 wt.% and 0.62 wt.%, respectively, using samples of 6 g and chosing 1 h measuring time.

EMANATION FROM LUNAR SOIL

The emanation characteristics of eight bulk lunar fines samples with 0.5 to 10.0 grams plus one small sample of Kreep glass were analysed by alpha cintillation counting techniques. The objective was to investigate the problem of radon mobility on the lunar surface and its possible contribution to the lead isotopic fractionation and redistribution, particularly its contribution to the anomalous U 238 /Pb 206 isotopic ratios. The samples were de-emanated at room temperature and a pressure of one atmosphere. An uniformily low radon escape rates and losses were observed in the analysed material. Three terrestrial analogues (obsidian, tektite and W-l) were analysed for comparison purposes. The observed data suggest that very little Rn 222 is escaping from the soil at the lunar surface and therefore it has a small direct contribution to the excess of isotopic lead.

RADON ESCAPE FROM POTTERY: EFFECT OF WETNESS

ABSTRACTSRadon and subsequent members of the uranium‐238 decay chain are responsible for an appreciable fraction of the radiation dosage received by pottery. Consequently in thermoluminescent dating calculations it is necessary to make an estimate of the degree to which this gas was escaping during burial. Direct measurement of the radon accumulated from pottery fragments indicates that wet conditions do not drastically inhibit the escape of radon, contrary to what has usually been assumed in thermoluminescent dating up till now.

Studies on the Elimination Rate and the Radiation Exposure Following Ingestion of 222Rn Rich Water

Abstract Radon-222 and its daughters in drinking water causes a radiation dose to the stomach of the order of Maximum Permissible Dose if water containing 100 nCi 222Rn/l. is consumed regularly. To evaluate the radiation dose in real conditions two types of experiment were performed with a whole-body counter. In the first series of measurements the elimination of 214Bi from the body was followed in test subjects who had ingested radon-rich water in a single intake. A one-component exponential function with a biological half life varying from 30 to 50 min was found to describe the elimination of radon. Special attention was paid to the escape of radon from the water and its effect on the state of disequilibrium between radon and its daughters after intake. In the second series of measurements a group of persons who had consumed radon-rich water daily was studied. The daily radon intake of these persons was estimated at 60 nCi, obtained in two or three portions. From the results of the experiments the dose equivalent of 240–440 mrem μCi 222Rn was derived and the maximum daily intake was set at 0.1 μCi for 222Rn in drinking water.

Model for radon diffusion through the lunar regolith

A model for radon diffusion through the lunar regolith is proposed in which the atom migrates by random walk. The regolith is represented by a system of randomly oriented baffles in which the mean distanced which the atom travels between two collisions takes on the role of a mean free path. The effective mean time between two collisions depends on two entities: the actual mean time-of-flight and the mean sticking time on grain surfaces for one collision. The latter depends strongly on the temperature and the heat of adsorption of radon on regolith materials. Bothd (mean free path) as well asQ (heat of adsorption) are either poorly known or unknown for the lunar regolith; hence these quantities are treated as free parameters. Because of the greatly different mean lifetimes against radioactive decay of219Rn,220Rn, and222Rn, the regolith acts as a powerful ‘filter’ for these species.222Rn escape is significant (32%) even ford = 1µ,Q = 7.0 kcal/mole and a regolith depth of 4 m. Calculations of radon escape from a 4 m thick regolith, usingd = 1, 10 and 80µ andQ = 4.0, 5.2 and 7.0 kcal/mole show that the222Rn/220Rn escape ratio can be as small as 7.7 and as large as, or larger than 47. The small value of 7.7 is of particular interest, because it is nearly equal to the escape ratio inferred by Turkevichet al. from their Surveyor 5 results.

Radium Content of Rainwater

ATMOSPHERIC radioactivity is generally attributed to the following: (1) escape of radon and thoron into the air from radioactive material in the surface of the Earth; (2) spallation products of atmospheric gases produced by cosmic radiation; (3) radioactive fall-out as a consequence of nuclear detonations.

Radon Escape from Bone Mineral

It has been known for a long time that when Ra226 is deposited in bone the first daughter, radon, born in the a-decay of radium, escapes readily from the animal. In the human being who has carried radium for many years, about 70% of the radon atoms formed are found to escape (1); in a dog this value ranges from 90 % in the case of a short-term burden to 70% after several years (1, 2). Since the half-life of radon is 3.84 days, there is apparently sufficient time available before it decays to escape from the body via the lungs after it reaches the blood stream. Norris (personal communication, 1953) has postulated that radon is freed from its parent crystal by its recoil after the a-decay of radium. To investigate this hypothesis, we have attempted to produce changes in vitro in the structure of bone which would alter the escape of radon, and to see whether or not the recoil hypothesis is consistent with these results. As a consequence of these measurements the problem of dosimetry of radiumburdened bone by a-track autoradiography has been clarified considerably, since the retention of the a-emitting daughters of radon, both in living bone and in sections prepared for autoradiography, must be known to evaluate properly the significance of the number of a-tracks recorded in the emulsion. These measurements have been made and are described below.