Polonium removal

Lead-bismuth purification from polonium. Some studies in this field have been carried out at the IPPE (Obninsk, Russian Federation). In particular, the possibility of polonium alkaline extraction from lead-bismuth was studied, coolant flow rate of-0.1% being sufficient to decrease polonium activity in the circuit by over 4 orders and transform extracted polonium into non-volatile compounds. Periodic polonium removal from the circuit is possible for instance before scheduled repair. 

Polonium removal. The behavior of Po in the FPS and FPN removal processes described above is not clear. Chemically, it is more noble than Bi and should not form an intermetallic compound with Zn, indicating that it should always remain with the Bi. In preliminary equilibration experiments with chloride salt mixtures, it was found that about 1% of the Po transferred to the salt, but whether this was due to chemical oxidation or volatilization is not presently known. 

Polonium can be mixed or alloyed with beryllium to provide a source of neutrons. The element has been used in devices for eliminating static charges in textile mills, etc. however, beta sources are both more commonly used and less dangerous. It is also used on brushes for removing dust from photographic films. The polonium for these is carefully sealed and controlled, minimizing hazards to the user. 

Marie Sklodowska Curie (1867—1934) and Pierre Curie (1859—1906) are credited with discovering polonium as they sought the source of radiation in pitchblende after they removed the uranium from its ore. Their discovery in 1898 led to the modern concepts of the nucleus of the atom, its structure, and how it reacts. 

They knew there must be another radioactive element in the pitchblende after the uranium was removed. Marie Curie painstakingly processed a ton of pitchblende to recover only a small amount of uranium. Even so, there was still something radioactive in all that processed pitchblende. As it turned out, there were two radioactive elements that she was able to isolate. One was radium, and the other polonium. They were identified by using piezoelectricity, discovered by her husband Pierre Curie, which could measure the strength of radiation given off by the radioactive elements with which Marie Curie was working. 

Polonium is used to eliminate static electricity in industrial processes, such as rolhng out paper, wire, or sheet metal in mills. Polonium is also sometimes used in brushes to remove dust from photographic film and in the manufacturing of spark plugs that make ignition systems in automobiles more efficient, particularly in extremely cold temperatures. It can also be used as a portable, low-level power source and, since polonium is fissionable, used in nuclear weapons and nuclear electric power plants. 

After neutron irradiation bismuth (canned in aluminum jackets) is dissolved in a mixture of hydrochloric and nitric acids and excess NO3 is removed by adding a reducing agent, such as, urea or formic acid. If bismuth is used as an anode, the reducing agent is dissolved in HCl. Various methods are applied for concentration of polonium in the acid mixture and its subsequent separation from bismuth. Such processes include spontaneous deposition of polonium over a less electropositive metal and coprecipitation with tellurium. In the latter method, a Te + or Te + salt is added to the extract, followed by addition of stannous chloride, which reduces both the tellurium and polonium to their metallic state, coprecipitating them from bismuth in the extract mixture. 

Another method to separate polonium from bismuth involves heating at 650°C to convert the metals into their oxides. This is followed by further heating to about 800° C at reduced pressure in which polonium metal is removed by volatilization. 

Fredenc and Irene Joliot-Cune found in 1933 that boron, magnesium, or aluminum, when bombarded with a-particles from polonium, emit neutrons, proton, and positrons, and that when the source of bombarding particles was removed, the emission of protons and neutrons ceased, but that of positrons continued. The targets remained radioactive, and the emission of radiation fell off exponentially just as it would for a naturally occurring radioclcmcnl. The results of this work may be stated in two equations as follows ... 

Polonium has a few commercial uses. For example, it is used to remove static electrical charges in certain industrial operations. The element is highly toxic. 

Polonium (ii) The radioisotopes of polonium (usually Po) have been difficult to analyze with accuracy using the conventional methods. The procedure outlined here is, however, simple, rapid, and accurate. With the sample in solution, add 3 to 5 mL of concentrated phosphoric acid and evaporate to remove other acids. Transfer this phosphoric acid solution to a small equilibration vessel using 3 to 5 mL of water. Add 1 mL of 0.1 M HCl. Add a measured volume, 1.2 to 1.5 mL, of a solution of TOPO, 0.1 to 0.2 M, in toluene and equilibrate. This is a highly selective separation of polonium from other radionuclides with the possible exception of the beta/gamma emitting bismuths. Quantitative stripping and transfer of the polonium to a plate is difficult but the use of an extractive scintillator and counting on a PERALS spectrometer is rapid and simple and the results are quite accurate. Because of the minimal chemical manipulations required, the accuracy of this determination can easily be better than 1%. 

However, minute amounts of radium-226 remain. Because the radioactive elements that would be needed to make the polonimn-210 are mostly removed, the amormt of polonimn-210 decreases as the pigment ages. The ratio between the amoimts of the radium-226 and the polonium-210 is used to establish the age of paintings. A low ratio of radium to polonium indicates a recent painting. 

As can be seen in Figure 1, radon itself and its polonium daughter products are alpha emitting nuclides, while the isotopes of lead and bismuth produced are beta/ gamma emitters. The short half-lives of the daughter products prior to Pb (Table 2) result in the rapid production of a mixture of airborne radioactive materials which may attain equilibrium concentrations within a relatively short time. The half-life of °Pb is 22 years and at this point in the decay chain any activity inhaled is largely removed from airways in which it is deposited before any appreciable decay occurs. 

Polonium is a strong emitter of a-particles approximately 1 gram of °Po emits 140 watts of heat energy. For this reason, it is used as a source of thermoelectric power in satellites. It is also utilized as a source of neutrons (when mixed with beryllium), as an antistatic device in industrial equipment, and in brushes that remove dust from photographic film, see also Curie, Marie Sklodowska Halogens Radioactivity Radium Uranium. 

Nystrom, C.W. Test of tourmahne filters for removal of polonium-210 from cigarette smoke RDM, 1964, No. 65, June 16, see www.ijrtdocs.com 501009890 -9894. 

The major reason for its radiation danger is the formation of radioactive polonium aerosols when hot LBC contacts with air. It could happen under conditions of emergency tightness loss of the primary circuit and coolant spillage. In this case, as the RI operation experience at the NS has displayed, the yield of Po aerosols and air radioactivity (according to the thermodynamics laws) reduce quickly with temperature decreasing and spilled alloy solidifying. Fast solidification of spilled LBC restricts the area of radioactive contamination and simplifies its removal in the form of solid radioactive wastes. 

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