SU977384A1 - Method of determining tritium in lithium-containing materials - Google Patents

Description

The invention relates to analytical chemistry, in particular, to methods for determining tritium, and to be used in controlling the accumulation of tritium in heat transfer fluids of atomic power plants, as well as in wastes going to landfill for the purpose of the environment. A known method for determining tritium in metallic lithium is by thermal separation of tritium dissolved in it into a hydrogen atmosphere, followed by separating the hydrogen-tritium mixture on palladium filters and measuring its beta activity by proportional-gas gas meters for internal filling of Cl. However, this method allows to determine high tritium contents (provided that hydrogen is highly purified. The closest to the technical essence and the achieved result to the proposed method is the method for determining tritium in lithium carbonate, including sample dissolution, precipitation of lithium hydrofluoric acid, addition to the liquid phase of the scintillator and the subsequent quantitative registration of tritium by scintillation j. effect 2. However, the known method is unsuitable for determining tritium in metallic lithium because the uncontrollable part of tritium in the form of Tj is lost to the atmosphere. The purpose of the invention is to analyze lithium metal samples. phase of the scintillator and the subsequent quantitative registration of tritium, the dissolution of the sample is carried out by heating in an autoclave in which the solvent (hydrogen peroxide) is pre-frozen and injected t sample, cooled to the freezing point of hydrogen peroxide. As a result of the interaction of lithium with water and hydrogen peroxide, an alkaline LiOH solution is formed, in which hydrogen peroxide decomposes according to the IOCh NO scheme; O- +

and part of the tritium, which is in the atomic state or in the form of molecules, reacts with OH radicals

Tj, + but iiHTO-t-T; T + HjO HTO + H H + T iHT; НО + НТ i НТО + Н НТ + НО Н, 2О + Т; T + BUT5 ± NTO.

As a result of the above processes, tritium quantitatively passes into the liquid phase in the form of predominantly .NTO, which is facilitated by high pressure (10 MPa) arising in the autoclave depending on the weight of metallic lithium and, accordingly, hydrogen peroxide, and effect in the interaction of metallic lithium with water and hydrogen peroxide

2Li + 2H2O- 2Ui OH + H-i 2L, i + ЗН jO, - - 2LiOH + 2H2p + 0

In order for these reactions not to proceed before the autoclave is sealed, lithium and hydrogen peroxide solution are cooled to a freezing point of 30% hydrogen peroxide solution or less. For under these conditions, there is no noticeable oxidation by atmospheric oxygen and its interaction with air water vapor, as well as with the solvent, hydrogen peroxide.

. Example. 1.4 ml of a 30% hydrogen peroxide solution is placed in an autoclave, which is an egg-shaped reaction zone with an additional shell capable of withstanding a pressure of 10 MPa and a device for vacuumization. The autoclave is placed in a cylindrical stove, capable of heating it at a rate of 10 degrees / m to / V, and pour a small amount of liquid nitrogen until the hydrogen peroxide hardens. A portion of lithium metal (0.0505 g |) irradiated at the reactor is placed in liquid nitrogen for several seconds and loaded into an autoclave, the latter is sealed, air and liquid nitrogen residues are pumped out with a vacuum pump.

and heated for 30 minutes, after which the autoclave is cooled and opened. The resulting solution is transferred to a polyethylene bottle, a stoichiometric amount of hydrofluoric acid is added, the scintillator and centrifuged. Tritium is determined by measuring the scintillation effect on a SL-30l three-channel spectrometer. To monitor the memory for tritium, after each measurement, the autoclave is filled with distilled water, sealed, and heated for 30 minutes. Water is analyzed for tritium. Distilled water activity shows a slight deviation from

background, which is -10% of changes. variable value.

The proposed method for determining tritium allows the determination of tritium.

in metallic lithium liquid

scintillation method with a sufficiently high reproducibility and accuracy.

Claims (2)

Invention Formula Method for determining tritium in lithium-containing materials, including sample dissolution, lithium osterification hydrofluoric acid, adding a scintillator to the liquid phase and the subsequent quantitative registration of tritium, characterized in that, in order to analyze the samples metal-lithium, the dissolution of the sample is carried out by heating in an autoclave, in which the solvent {hydrogen peroxide} is pre-frozen, and the sample is cooled to the freezing point of hydrogen peroxide. Sources of information taken into account during the examination 1. Kuznetsov V.V. The formation of tritium in lead and aluminum under the action of protons, deuterons, and high-energy alpha particles. - Journal of Experimental and Theoretical Physics. V. 40, 1968, p. five. 2. NucJear Iristruments.and methods, U „102, 1973, 2, p. 397.