Radioactive gases

Figure 10. The Cross Sectional Profiles of the Reactor Gases Radioactivity (Using Kr-85 In Fuel Gas) at Reactor Port Locations (HAF Data)...

Pulmonary disease. Xenon is one of the noble gases. Radioactive xenon-133 may be inhaled by the patient. The radioactive isotope will be transported from the lungs and distributed through the circulatory system. Monitoring the distribution, as well as the reverse process, the removal of the isotope from the body (exhalation), can provide evidence of obstructive pulmonary disease, such as cancer or emphysema. 

The radioactivity of the atmosphere is due particularly to radioactive aerosols and gases the characteristics of these correspond to those of non-radioactive aerosols and gases. Radioactive substances may form solid or liquid particles either directly or by sorption on the surface of non-radioactive particles. It is possible to tell very simply that aerosols may be affected by the wide range of various characteristics of components of particular particles, whereas the behaviour of gases is given by the simple characteristics of atoms and molecules present in their free state. 

Of the noble gases, radioactive xenon has completely decayed after 1 y cooling, but krypton contains Kr with 10.7 y half-life. This isotope is produced in appreciable amounts, and though commonly it has been released to the atmosphere, this is no longer acceptable. Many processes have been devised for krypton removal. Krypton in dry, clean air is effectively trapped on a charcoal filter at cryogenic temperature however, because of explosion risk (due to reaction between radiolytically formed ozone and carbon), the favored process is condensation by liquid N2 (kiypton boils at -153 C) followed by fractional distillation. This removes >99% of %r. The krypton can be stored in pressurized cylinders until Kr has decayed (>100 years). 

The identification number, effective November 1, 1981, on either an orange display panel (see Section 172.332) or on the DOT placard" (but not a POISON GAS, RADIOACTIVE or EXPLOSIVES placard) as described in Section 172.334."... 

A cargo tank must also be marked with the appropriate indentification number on each side and the rear end. As with a portable tank, the identification number must also be placed on orange display placards, DOT placards (except POISON GAS, RADIOACTIVE or EXPLOSIVES placards), or a white square-on-point configuration with the same dimensions as a placard. Identification numbers are not required, however—... 

Within the primary circuit radioactive coolant is protected against air by the steel barriers and cover argon gas. Radioactive sodium of the primary circuit is separated from non-radioactive sodium of the secondary circuit by the steel tubes of the intermediate heat exchangers. 

An investigation was made of diffusion into intrinsic n-type crystals which were doped with P to 5 x lO /cm, and into B pre-diffused extrinsic p-type crystals, by using a closed-tube diffusion technique. Profiles were determined by means of neutron activation and Ga radioactive tracer and sectioning techniques. The overall results for 900 to 1050C could be described by ... 

If the materials meets the PHMSA definition of an explosive, fiammable (gas and hqiiids), flammable solid, oxidizer, poison (sohd and gas), radioactive material, or corrosive, then the company, driver, and vehicle are subject to the PHMSA regulations, as well as the FMCSA safety regidations. 

Combustible Flammable Corrosive Oxidizer Air Reactive Water Reactive Pressurized Gas Radioactive Infectious Explosive Poison... 

The method is based on the international standard ISO 4053/IV. A small amount of the radioactive tracer is injected instantaneously into the flare gas flow through e.g. a valve, representing the only physical interference with the process. Radiation detectors are mounted outside the pipe and the variation of tracer concentration with time is recorded as the tracer moves with the gas stream and passes by the detectors. A control, supply and data registration unit including PC is used for on site data treatment... 

The method implies injection of a mixture of 3 radioactive tracers each being distributed into one of the 3 phases. The tracers must show such differences in the emitting y-radiation energy spectra that they can be simultaneously detected by on line y-spectrometry. Candidate tracers are Br-82 as bromobenzene for oil, Na-24 or La-140 for water, and Kr-85 for gas. The tracers are injected simultaneously at a constant rate into the flow in the pressurised pipe, and the concentration is detected as series of instantaneous measurements taken downstream as illustrated in figure 2. 

Cerium is a component of misch metal, which is extensively used in the manufacture of pyrophoric alloys for cigarette lighters. While cerium is not radioactive, the impure commercial grade may contain traces of thorium, which is radioactive. The oxide is an important constituent of incandescent gas mantles and is emerging as a hydrocarbon catalyst in self cleaning ovens. In this application it can be incorporated into oven walls to prevent the collection of cooking residues. 

An instrument for counting radioactive particles based on their ability to ionize an inert gas such as Ar. 

From the radioactive decay constants and measurement of the amount of argon in a rock sample, the length of time since formation of the rock can be estimated. Essentially, the dating method requires fusion of a rock sample under high vacuum to release the argon gas that has collected through radioactive decay of potassium. The amount of argon is determined mass spectrometrically,... 

Nuclear Waste Management. Separation of radioactive wastes provides a number of relatively small scale but vitally important uses of gas-phase purification appHcations of adsorption. Such appHcations often require extremely high degrees of purification because of the high toxicity of... 

Radon-222 [14859-67-7] Rn, is a naturally occuriing, iaert, radioactive gas formed from the decay of radium-226 [13982-63-3] Ra. Because Ra is a ubiquitous, water-soluble component of the earth s cmst, its daughter product, Rn, is found everywhere. A major health concern is radon s radioactive decay products. Radon has a half-life of 4 days, decayiag to polonium-218 [15422-74-9] Po, with the emission of an a particle. It is Po, an a-emitter having a half-life of 3 min, and polonium-214 [15735-67-8] Po, an a-emitter having a half-life of 1.6 x lO " s, that are of most concern. Polonium-218 decays to lead-214 [15067-28A] a p-emitter haviag = 27 min, which decays to bismuth-214 [14733-03-0], a p-emitter haviag... 

Tracer Type. A discrete quantity of a foreign substance is injected momentarily into the flow stream and the time interval for this substance to reach a detection point, or pass between detection points, is measured. From this time, the average velocity can be computed. Among the tracers that have historically been used are salt, anhydrous ammonia, nitrous oxide, dyes, and radioactive isotopes. The most common appHcation area for tracer methods is in gas pipelines where tracers are used to check existing metered sections and to spot-check unmetered sections. 

The radioactive isotopes available for use as precursors for radioactive tracer manufacturing include barium [ C]-carbonate [1882-53-7], tritium gas, p2p] phosphoric acid or pP]-phosphoric acid [15364-02-0], p S]-sulfuric acid [13770-01 -9], and sodium [ I]-iodide [24359-64-6]. It is from these chemical forms that the corresponding radioactive tracer chemicals are synthesized. [ C]-Carbon dioxide, [ C]-benzene, and [ C]-methyl iodide require vacuum-line handling in weU-ventilated fume hoods. Tritium gas, pH]-methyl iodide, sodium borotritide, and [ I]-iodine, which are the most difficult forms of these isotopes to contain, must be handled in specialized closed systems. Sodium p S]-sulfate and sodium [ I]-iodide must be handled similarly in closed systems to avoid the Uberation of volatile p S]-sulfur oxides and [ I]-iodine. Adequate shielding must be provided when handling P P]-phosphoric acid to minimize exposure to external radiation. 

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