Radiolysis Of Water Solutions Research Articles

Radiation-chemical removal of corrosion hydrogen from VVER first-loop coolant

Room-temperature γ radiolysis of water solutions of ammonia in the presence of hydrogen peroxide is studied. It is found that in de-aerated solutions the yield of hydrogen peroxide decomposition is 3.8–5.5 mol/100 eV depending on its initial concentration. In the absence of hydrogen peroxide, the yield of the decomposition of ammonia is 0.34–0.39 particles/100 eV; adding hydrogen peroxide to the solution increases the rate of decomposition of ammonia and saturation of the solution with hydrogen decreases it. The data obtained are used for mathematical simulation of the influence of hydrogen peroxide on the composition of the first-loop coolant of a hypothetical ship reactor facility with VVER where equipment corrodes with hydrogen being formed. It is shown that adding hydrogen peroxide to the coolant in molar concentration equal to that of corrosion hydrogen decreases the stationary concentration of hydrogen and ammonia to the level characteristic for the case where there is no equipment corrosion with hydrogen being formed in the loop.

“Protoka” Experimental Stand for Studying High-Temperature Radiolysis of Water by Accelerated Protons

The experimental stand “Protoka,” put into operation in 2000 at the Russian Science Center Kurchatov Institute, for studying high-temperature radiolysis of water under the action of accelerated protons is described. The principles of simulation of radiolytic effects under the action of nuclear reactor radiation on water, using the results of experiments on radiolysis of water by accelerated protons, are discussed. The “Protoka” data on the radiolysis of water solutions of hydrazine and a mixture of molecular hydrogen and hydrogen peroxide are presented.

Change in the stationary oxygen concentration in RBMK-1000 reactor water accompanying variation of the oxygen concentration in the feed water

UDC 541.15 The neutral water regime with oxygen dosing at a nuclear power plant with a RBMK-1000 reactor has been under discussion now for a long time [1, 2]. A central point of this discussion is estimation of the a priori possible increase in the oxygen concentration in reactor water accompanying the addition of a small, measured quantity of oxygen into the feed water. In [2-4] an attempt was made to solve this problem empirically by examining the oxygen balance in the first loop of the reactor. Although the radiation-chemical process was mentioned as a source of oxygen in reactor water, nothing was said about the mechanisms of the process. At the same time, in our opinion, the problem can be solved by applying the general laws of the radiation chemistry of water to the formation of the products of radiolysis of water in RBMK-1000. From the standpoint of the radiation chemistry of water, an estimate of the change in the stationary concentration of oxygen formed by radiolysis of water accompanying a change in the initial concentration of oxygen can be formulated as follows. Let the reactor feed water contain the regulated concentration of oxygen [O2]feed R. When such water is fed into the multiple forced circulation loop (MFCL), it is mixed with the circulation water, and its concentration at the entrance into the core becomes equal to [O2]iniR. In accordance with this concentration, on passage through the core a stationary hydrogen concentration [H2]st R and oxygen concentration [O2]st R is established in the coolant. If the oxygen concentration in the feed water is increased up to [O2]feea s, then the oxygen concentration in the water at the entrance into the core (we denote it by [O2]iniS ) and the stationary concentration of hydrogen and oxygen in the coolant after passage through the core (we denote them by [H2]st s and [O2]st s) will change. The problem is to determine the extent to which or by how many times the stationary oxgyen concentration in the reactor water will change when its concentration in the feed water fluctuates. To solve this problem we employ the experimental data on the mechanisms leading to the establishment of a stationary concentration of the products of radiolysis of water solutions of oxygen, data on single measurements of the parameters of the water-chemical regime of RBMK reactors and other boiling-water reactors, and the fundamental laws of the radiation chemistry of water. It is known that the stationary concentration of hydrogen, oxgyen, and hydrogen peroxide during -t-radiolysis of water is proportional to the initial concentration of oxygen dissolved in the water prior to irradiation:

Formation of hydrated electrons upon dissolution of crystals containingF centres

The hydrated electron (symbol e~q) joined definitively itself to the family of chemical reagents during the last decade. Its discovery will be remembered without any doubt among the most brilliant results achieved in the chemical field ia these years. The hydrated electron is formed by an electron surrounded by four oriented molecules of water, in other words c~ is an electron trapped in a cage of water molecules. I ts fundamental chemical characteristic is an unusually high electron donor capacity which makes its reactivity very high and therefore its mean life very short in all media. Hydrated electrons can be produced in several manners (1), for instance by metal dissolution in water, by electrochemical reduction, by photolysis, etc., but the principal method for producing e~Q is the radiolysis of water solutions. Indeed the most important contributions to the discovery and chemical characterization of hydrated electron came and are coming from the radiation chemistry, particularly from pulsed radiolysis. Sometimes the individuation of the chemical reactivity of e~ towards certain substances is made difficult by the fact that many other radicals are produced together with e~q by radiolysis. Therefore a method capable to produce only, or almost only, e~q without any serious chemical complications, as for instance those connected with the method of alkali-metal dissolution in water, should be interesting. The dissolution in water of crystals containing E centres seemed to us a potential source of hydrated electrons having the properties mentioned above. I t is well known that an _~ centre results when an electron is trapped at the site of a missing anion. When crystals conta in ing/~ centres are dissolved in water the cation cage which traps the electron is destroyed and the electron should be freed into the solution giving rise to e~. As the concentration of F centres in alkali halides can at tain values as high as 101 F centres/em 3 (that is 5.1017 _F centres/g) and the solubility for instance of NaC1 in water is ~ 330 g/l, the potential amount of e:~ which can be generated upon crystal dissolution reaches values of the order of a few 10-dg equiv/l. The F centres in alkali halides can be produced by Xor y-ray irradiation or by incorporating an excess of alkali metal in the crystal. The alkali excess occupies normal