Radiation decomposition

Properties of T2O. Some important physical properties of T2O are Hsted in Table 2. Tritium oxide [14940-65-9] can be prepared by catalytic oxidation of T2 or by reduction of copper oxide using tritium gas. T2O, even of low (2—19% T) isotopic abundance, undergoes radiation decomposition to form HT and O2. Decomposition continues, even at 77 K, when the water is fro2en. Pure tritiated water irradiates itself at the rate of 10 MGy/d (10 rad/d). A stationary concentration of tritium peroxide, T2O2, is always present (9). AH of these factors must be taken into account in evaluating the physical constants of a particular sample of T2O. 

Chain reactions such as those described above, in which atomic species or radicals play a rate-determining part in a series of sequential reactions, are nearly always present in processes for the preparation of thin films by die decomposition of gaseous molecules. This may be achieved by thermal dissociation, by radiation decomposition (photochemical decomposition), or by electron bombardment, either by beams of elecuons or in plasmas. The molecules involved cover a wide range from simple diatomic molecules which dissociate to atoms, to organometallic species with complex dissociation patterns. The... 

The radiation decomposition in 10-3 M polonium solution ( 1 curic/ml) causes a visible evolution of gas (5, 34). The radiolysis products are strongly oxidizing, which adds difficulty to the study of the element in its lower, bipositive, state. Peroxide formation appears to be the factor which prevents a study of solutions of the element in the sexapositive state (13), at any rate on the milligram scale. 

There have been some unsuccessful attempts to prepare a volatile hexafluoride from fluorine and polonium-210 26, 104), but recently such a fluoride has been prepared in this way from polonium-208 plated on platinum 132). The product appears to be stable while in the vapor phase, but on cooling a nonvolatile compound is formed, probably polonium tetrafluoride resulting from radiation decomposition of the hexafluoride. Analytical data are not recorded for any polonium fluoride, largely owing to the difficulty of determining fluoride ion accurately at the microgram level. 

Its solutions in dilute hydrobromic acid are a carmine-red (0.025 M PoBr4) and in more dilute solution (10 3 M), orange red. The tetrabromide is soluble in ethanol, acetone and some other ketones, and is sparingly soluble in liquid bromine. It is hygroscopic and is easily hydrolyzed to a white, basic bromide of variable composition. It forms a yellow ammine in ammonia gas and this yields polonium dibromide and polonium metal on standing, presumably because of radiation decomposition of the ammonia and subsequent hydrogen reduction of the tetrabromide (7). 

This is a white crystalline solid made by treating polonium(IV) hydroxide or chloride with aqueous hydrocyanic acid. It blackens rapidly on standing owing to radiation decomposition. Its solubility in aqueous potassium cyanide is low, increasing from 0.089 mg (of Po210)/liter in 0.05 M solution to 1.19 mg/liter in 1.5 M solution, so that cyanide complex ions may be formed (11). 

Polonium tetrachloride is very soluble in 2 N tartaric acid, giving a colorless solution which slowly darkens owing to radiation decomposition. Electrolysis leads to deposition of about 12% of the polonium on the cathode and 65% on the anode (11). 

A separate problem is presented by the possible radiation decomposition of THIO. Thus it is reported that the main radioly-tic products of THIO solution are sulphate, sulphur and sulphite with respective G values of 0.8 0.55 and 0.16 and overall G decomposition value (-THI0) of 2.95 (16). A contradicting report... 

The intense primary y radiation due to nuclear fission, the secondary y radiation emitted by the fission and activation products and the radiation from the fission products give rise to radiation-induced chemical reactions. The most important reaction is the radiation decomposition of water in water-cooled reactors, leading to the formation of H2, H2O2 and O2. Many substances dissolved in the water influence the formation of H2 (Fig. 11.18). In most closed coolant systems equipment for... 

In a parallel set of discoveries, a reflectance band in the visible, similar to that for solid 02, was seen at low latitudes on Ganymede. In addition, a UV feature associated with O3 was seen on Ganymede and on the icy satellites of Saturn. Coupled with these observations was the much earlier discovery of a band indicative of SO2 in ice at Europa and Callisto and the recent discovery of CO2 trapped in the icy surfaces. The SO2 was initially assumed to be due to sulfur ions originating at lo implanted into the ice at Europa, " but the SO2 is also a radiation decomposition product like the O2, as discussed below. " The CO2 source is probably internal as carbon ions have not yet been seen in the plasma. 

Radiation damage Superconductivity of bombarded metals Variations of thin film properties Simulation of radiation damage e.g. in nuclear power plants Radiation Chemistry Ion sputtering Ion reflection Radiation decomposition of gases... 

In the last section of the chapter on radiation chemistry we shall mention briefly the radiation decomposition of surface compounds due to the sputtering effect (Sect. 2.5). There are several reasons why this effect is of interest. 

The conclusion was that Cr(CO)g had been formed during a reaction between the implanted Cr and the target molecules or their fragments arising from the radiation decomposition. 

It is not necessary that these three types of influence be exerted through point defects in the intrinsic crystal lattice of the catalyst. Species adsorbed on the surface or more permanently attached as terminating groups of the lattice may in their original state or after radiation-decomposition provide suitable electronic or geometrical conditions for adsorption or catalysis (E). Irradiation may then destroy or create catalytic sites in the adsorbed layer, and these sites have to be considered in fixing the responsibility for an observed radiation effect. At least conceptually, they can operate in any of the three ways just described and, in addition, can block active surface sites on the intrinsic lattice. 

Figure 3 is the same plot for alanine. The curves are all initially linear and the G values were calculated from this initial linear portion. Low deviations on the ammonia curves at the highest absorbed dose may reflect high decomposition of original amino acid. Amino acids with higher specific activities were used to determine G(C02) at lower absorbed doses. These values are significantly lower as shown in Figure 4. The problem of impurity introduced by the radiation decomposition of the original material and its effect on measured G values confronts all workers in this area. For consistency and since these values have a much more reliable analytical basis, the high dose values will be used throughout. The results of interest are the relative G values in any case since absolute values are acknowledged to depend on dose.

The lower G(C02) values at very low radiation levels (Figures 2, 3, and 4) are difficult to explain. Decarboxylation by radical-radical reactions suggested by comparison with saturation of EPR signals is a possibility. Recent work by Tolbert and Krinks (20) on the decarboxylation of phenylalanine in vacuo and in H2S shows no change in G values and does not indicate such a mechanism. Another possible explanation for higher G(C02) values at higher doses is radiation decarboxylation of intermediate species produced by the radiation decomposition process. 

The radiation decomposition in water cooled and/or moderated reactors is considerable. About 2% of the total ergy of the 7- and n-radiation is deposited in the water. We have seen in 7.6 that this produces H2, O2, and reactive radicals. In a 1 GW, BWR the oxygen production is about 1 1 min but it is considerably less in a PWR. Because of the explosion risk from H2 + O2, the two are recombined catalytically to H2O in all water reactors. 

The specifications for purified uranium and plutonium to be recycled are summarized in Table 21.7. Comparing these data with those presented before sliows diat at t 1 y the fission product activity must be reduced by a factor of 10 and the uranium contrait in plutonium by a factor of 2 X 10. The large number of chemical elem its involved (FPs, actinides and corrosion products) make the separation a difficult task. Additional complications arise from radiation decomposition and criticality risks and from the necessity to conduct all processes remotely in heavily shielded enclosures under extensive health protection measures. As a result reprocessing is one of the most complicated chemical processes ever endeavored on an industrial scale. 

As noted in the introduction, the small band gap azides of lead, silver, and thallium exhibit many similar properties which differentiate them from the large band gap azides. Barium azide may be an intermediate case since with irradiation it shows properties similar to both groups of materials. The small band gap azides in question detonate while barium azide deflagrates but will not sustain detonation. When the small band gap azides, barium azide, and silver and lead halides are exposed to radiation, decomposition appears to take place in both the metal and anion sublattices. Apparently, colloidal metal is formed from the metal sublattice [7,8,81-84] and, in addition, nitrogen [85,86] or halogen gas [87,88] is liberated from the anion sublattice. The relationship... 

Anan ev, V.A. and Seliverstov, M. N. 2006. The radiation decomposition of crystalline alkali nitrates. The 2nd International Congress on Radiation Physics, High Current Electronics, arul Modification of Materials, Tomsk, Russia, September 10-15, pp 85-88. 

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