Alpha radiation from radon

Lind and Bardwell have summarized the effects of radio-active materials on methane oxidation. Under the influence of the alpha radiation from radon the oxidation of methane proceeded completely to carbon dioxide and water. The oxidation took place in one step, and from the numerical relation between the number of gaseous ions produced and the methane molecules oxidized, the formation of triplet ion clusters was postulated as shown ... 

As much as 75 per cent of the theoretical oxidation based on the radiation was obtained. Selenium diethyl was found to accelerate the oxidation under the influence of alpha radiation from radon. 

Lind and Bardwell14 found that in the initial stages of the reaction between ethane and oxygen under the action of alpha radiation from radon the rate of reaction was nearly double that between oxygen and methane tinder comparable conditions, but that the velocity of reaction decreased sharply when the reaction was about 70 per cent complete. As in the case of methane, the yield of oxidation products was 75 per cent of the maximum theoretically possible on the basis of number of ions present. 

Alpha radiation from radon and its radioactive progeny accumulated in enclosed or poorly ventilated areas and associated with high concentrations of dust in the air spaces. These areas with high concentrations of radon and high levels of dustiness pose a high risk to the health of workers. 

Assess worker exposure to external gamma radiation, the inhaled and ingested radioactive dust, and alpha radiation from radon and estimate the total dose of ionizing radiation to which workers may be exposed. 

A solid-state nuclear track detector is a piece of special plastic which is exposed as the sensitive element in a radon monitor. The alpha radiation from Rn and RnD, which penetrates the surface of the plastic, causes radiation damage along the entrance path, as shown in the schematic in Fig. 9.26. Chemical etching of the plastic after exposure... 

Two types of track-etch monitor occur, open and closed types. In the open type, the SSNTD is not contained in a volume and is exposed to the air as a bare foil. This detector will register the alpha radiation from the Rn and RnD in the air, and the track density on the foil represents the sum of these activities. However, the Rn signal will be much larger than the signal from the RnD, except at very high levels of RnD (high F factor), and the track density has to be interpreted in terms of this ratio, which is typically unknown. In close monitors the SSNTD is enclosed in a closed container into which Rn diffuses through a filter. This prevents the entry of RnD and dust particles into the chamber, and the foil is then sensitive only to the alpha radiation from Rn and RnD formed in the container. There is a repeatable equilibrium between the isotopes in the container, and calibration provides the relationship between the Rn concentration and the track density on the foil. A typical track-etch radon monitor of the closed type is shown in Fig. 9.27. 

The oxidation of butane and propane under the influence of radiation from radon did not go to completion as indicated by the appearance of liquid products other than water.7 Prolonged exposure to the alpha radiation, however, gave complete oxidation in the case of propane. 

The size distribution of Rn decay product aerosols in ambient air exerts a marked effect on the calculated dose to lung tissue following inhalation of radon-contaminated air because of the alpha radiation from its decay products ( Po, " Po). 

Ttie major hazard from radon stems from its radiation of alpha particles, even though alpha particles (helium nuclei) can be stopped by a sheet of cardboard. When Rn-222 is inhaled, it decays into lead-210, which is also radioactive, and because it not easily exhaled, it remains in the lungs for long periods, causing lung cancer. It is estimated that about 10% of all lung cancers are cause by radon. 

L.A. Braby (Pacific Northwest Laboratories) is studying the malignant transformation of mammalian cells exposed to alpha particles that pass through the cell nuclei in an attempt to elucidate the mechanisms of action of radiation. The mechanisms of cell killing by alpha particles (M. Raju, Los Alamos Laboratories), cell neoplastic transformation from alpha particles (S.B. Curtis, Lawrence Berkeley Laboratory), and pulmonary tissue injury from radon/radon daughter exposure (T.M. Seed, Argonne National Laboratory) are also under investigation. 

Extremely minute quantities of uranium occur widely in many types of rock and soil, and radon is found in all 50 states. The real risk from radon is derived from its products of natural radioactive decay, as damaging ionizing radiation in the form of alpha particles and other daughter products can be emitted. 

The alpha radiation of the eight alpha-emitting nuclides contained in the U-238 series and, to a lesser degree, of the seven alpha emitters in the U-235 series presents a radiation hazard on ingestion or inhalation of uranium ore (i.e., dust) and radon, while gamma radiation, mainly from Pb-214 and Bi-214, together with beta radiation of Th-234, Pa-234m, Pb-214, Bi-214, and Bi-210, presents an external radiation hazard. 

The hazards associated with breathing radon-222 come not only from the alpha radiation emitted as the radon decays but also from the daughter products of that decay. None of these decay products are gases, but all are radioactive. Because they are not gases, they are not easily exhaled and can become lodged in the lungs, where their radiation can cause serious damage. 

Alpha decay carries away positive charge and electrons are stripped from the parent atom by its recoil. Therefore, the decay products are formed as positive ions. Air is ionised by radiation from the naturally occurring radionuclides in the air and on the ground and by cosmic rays. Production of one ion pair requires 32.5 eV if ionisation is caused by fast electrons, 35.6 eV if by alpha particles. The total energy dissipated in air per decay of Rn depends on the equilibrium ratio of the radon decay products. 

It has been reported for many years that condensation nuclei can be produced by ionizing radiation. Recent studies have improved the measurement of the activity size distribution of these ultrafine particles produced by radon and its daughters (Reineking, et al., 1985 Knutson, et al., 1985). It seems that the Po-218 ion is formed by the radon decay, is neutralized within a few tens of milliseconds, and then attached to an ultrafine particle formed by the radiolysis generated by the polonium ion recoil. Although there will be radiolysis along the alpha track, those reactions will be very far away (several centimeters) from the polonium nucleus when it reaches thermal velocity. The recoil path radiolysis therefore seems to be the more likely source of the ultrafine particles near enough to the polonium atom to rapidly incorporate it. 

Use nuclear power, medical X-rays, medical diagnostics, scientific research, cancer treatment, cathode ray tube displays Source radon, X-rays, radioactive materials produce alpha, beta, and gamma radiation, cosmic rays from the sun and space Recommended daily intake none (not essential)... 

---