Radioactive components

Nuclear wastes are classified according to the level of radioactivity. Low level wastes (LLW) from reactors arise primarily from the cooling water, either because of leakage from fuel or activation of impurities by neutron absorption. Most LLW will be disposed of in near-surface faciHties at various locations around the United States. Mixed wastes are those having both a ha2ardous and a radioactive component. Transuranic (TRU) waste containing plutonium comes from chemical processes related to nuclear weapons production. These are to be placed in underground salt deposits in New Mexico (see... 

Approximately 25—30% of a reactor s fuel is removed and replaced during plaimed refueling outages, which normally occur every 12 to 18 months. Spent fuel is highly radioactive because it contains by-products from nuclear fission created during reactor operation. A characteristic of these radioactive materials is that they gradually decay, losing their radioactive properties at a set rate. Each radioactive component has a different rate of decay known as its half-life, which is the time it takes for a material to lose half of its radioactivity. The radioactive components in spent nuclear fuel include cobalt-60 (5-yr half-Hfe), cesium-137 (30-yr half-Hfe), and plutonium-239 (24,400-yr half-Hfe). 

TLC Analysis. Samples were examined by TLC using standard procedures. Rf values were determined and compared with those of authentic reference materials. Radioactive components were located by scanning (Vanguard Instrument Corp., North Haven, Conn., Model 885) or by autoradiography (Eastman Kodak, Rochester, N. Y., type AA film). The relative Rf value of DCDD on silica gel plates (Brinkmann Instruments, Inc., Westbury, N. Y., type For,4) when developed with n-hexane dioxane acetic acid, 90 10 4, V/V/V, was 0.90. The observed impurity had a relative Rf value of 0.40. On Brinkmann alumina plates, developed with n-hexane, DCDD had a relative Rf of 0.32. Neither system separated the chlorinated dibenzodioxin isomers. 

Butex A process for separating the radioactive components of spent nuclear fuel by solvent extraction from nitric acid solution, using diethylene glycol dibutyl ether (also called Butex, or dibutyl carbitol) as the solvent. Developed by the Ministry of Supply (later the UK Atomic Energy Authority) in the late 1940s. Operated at Windscale from 1952 until 1964 when it was superseded by the Purex process. 

Radioactive components of instruments used to find cracks in pipelines and aircraft... 

For a closed system, the total mass of the system is conserved. For a component that is made of nonradioactive and nonradiogenic nuclides, the concentration of the component in the whole system can increase or decrease only through chemical reactions. The mass of a radioactive component decreases with time due to decay, whereas that of a radiogenic component increases with time (nuclear reaction). On the basis of mass conservation, some relations can be derived... 

The diffusion of a radioactive component is a relatively easy problem. It is discussed here to illustrate how coupled diffusion and homogeneous reaction can be treated, and to prepare for the more difficult problem of the diffusion of a radiogenic component. The diffusion of a radiogenic component, which is dealt with in Section 3.5.2, is an important geological problem because of its application in geochronology and thermochronology. 

A radioactive component is consumed by its decay (homogeneous reaction). For example, one-dimensional diffusion of in zircon along the crystallographic axis c or along any direction in the a-b plane can be described by... 

Envirocare of Utah, Inc. (Envirocare) has commercialized the polyethylene encapsulation process developed by Brookhaven National Laboratory (BNL) as an ex situ stabilization technology for hazardous and mixed wastes (wastes with both hazardous and radioactive components). 

The ISV process uses electricity to heat and melt soil and other earthen materials contaminated with organic, inorganic, and radioactive compounds. Organic compounds undergo pyrolysis (thermal decomposition in the absence of oxygen). The pyrolyzed compounds then migrate to the surface zone, where they are collected and oxidized in a collection hood. Inorganic and radioactive components are incorporated as oxides into a leach-resistant vitrified product. 

The vendor also claims that RadAway can effectively separate mixed waste—waste containing radioactive materials and hazardous solvents. This separation allows the solvent to be disposed of separately from the radioactive component, greatly reducing disposal costs. However, RadAway does not have regulatory approval for mixed waste. 

Slope of Specific Activity vs. Size for Prompt Fallout. The relatively small slope of specific activity vs. particle size undoubtedly is a consequence of mixing of relatively inert debris from more distant soil horizons with debris which has had a more intimate mixing with the radioactive components of the fireball. In fact, particles below 100p must have originated in the stem of the cloud for the most part. They could not have fallen from the cloud itself. 

It is well established that in non-arid regions, precipitation is the primary means by which contaminating aerosols are removed from the atmosphere. Many chemical, physical, and meteorological parameters affect the micro, meso, and synoptic scale processes through which precipitation transports radioactive aerosols from atmosphere to ground. These parameters include the radioactivity component of the natural aerosols, the processes by which water vapor condenses and grows to raindrops, and the incorporation of the radioactive aerosol into the precipitation. Thus, the prediction of specific deposition from fundamental considerations has proved to be difficult because of the many uncertainties yet prevalent in these processes. Many attempts have been made to evaluate the deposition of these aerosols by empirical studies. 

TABLE 19.8. Data of Foam Separation Experiments Made in a 1 in. Dia Column on a Waste Water Containing Radioactive Components and Utilizing Several Different Surfactants... 

Again, a Fick s-law expression is obtained for the self-diffusion of the radioactive component. The self-diffusivity of component 1 in a binary system of uniform chemical composition is designated by D to distinguish it from the self-diffusivity of a pure material, D. 

K is a (3 -emitting nuclide that is the predominant radioactive component of normal foods and human tissue. Due to the 1460-keV 7 ray that accompanies the (3 decay, it is also an important source of background radiation detected by 7-ray spectrometers. The natural concentration in the body contributes about 17 mrem/y to the whole body dose. The specific activity of 40K is approximately 855 pCi/g potassium. Despite the high specific activity of 87Rb of 2400 pCi/g, the low abundance of rubidium in nature makes its contribution to the overall radioactivity of the environment small. 

One of the most popular radiometric techniques is that of radiometric titrations. In a radiometric titration, the unknown is titrated with a radioactive reagent, and the radioactivity of the product or supernate, formed by the chemical reaction of the reagent and the unknown material, is monitored as a function of titrant volume to determine the endpoint. This means that the radioactive component being followed must be isolated during the titration and its activity measured—that is, a discontinuous titration. 

SASD (Chapter 5, Section 3.2) behaves in a similar manner, except it contains an amine-reactive end that can be coupled to proteins and other molecules. Its photoreactive end can be iodinated using any of the radioiodination reagents discussed previously. Just as in the case of APDP, SASD cross-links can be cleaved by a disulfide reductant to transfer the radioactive component to a second molecule. 

The term mixed waste refers mainly to waste that contains radionuclides regulated under AEA and hazardous chemical waste regulated under RCRA. Dual regulation of mixed waste has no effect on classification, management, and disposal of the hazardous chemical component or on classification of the radioactive component. The effects of dual regulation of mixed waste on management and disposal of the radioactive component are summarized as follows ... 

Technical requirements on treatment and disposal of spent fuel, high-level waste, and transuranic waste established under AEA should be largely unaffected by the presence of waste classified as hazardous under RCRA Some of these wastes meet technology-based treatment standards for hazardous chemical waste established by EPA (e.gvitrified high-level waste is an acceptable waste form under RCRA). Alternatively, a finding that disposal of the radioactive component of the waste complies with applicable environmental standards established by EPA under AEA can serve to exempt the disposal facility from prohibitions on disposal of restricted hazardous chemical wastes under RCRA [e.g., disposal of mixed transuranic waste at the Waste Isolation Pilot Plant (WIPP)]. 

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