RU1619492C - Method of and device for reconditioning tritium fuel mixture in nuclear reactor - Google Patents

Abstract

FIELD: hydrogen isotope separation. SUBSTANCE: method involves introduction of gaseous iodine into fuel mixture, mixture condensation on cold surface at 4.2 K. Condensed mixture is exposed to temperature of 8-9 K for binding excess protium with iodine atoms; isotopes are separated in two stages; during first stage condensate is heated to 26-77 K and fuel mixture is separated from excess protium; during second stage fuel mixture is heated to 240-300 K and iodine compound are removed. Mixture thus prepared is supplied to gas mixture condensation unit. Solid matrix is exposed to 8-9 K. Process is characterized in that it dispenses with conversion to new substance and vice versa, which greatly simplifies auxiliary equipment design and does not required high-cost pieces of equipment. EFFECT: reduced power requirement, simplified process of light hydrogen isotope separation. 2 cl, 1 dwg

Description

 The invention relates to the separation of hydrogen isotopes by chemical exchange and can be used for the regeneration of deuterium-tritium fuel mixture of a thermonuclear reactor.

 The purpose of the invention is the reduction of energy consumption and simplification of the process of separation of protium.

 The essence of the method of regenerating the mixture is based, firstly, on the possibility of the formation of hydrogen isotope atoms in the condensed fuel mixture as a result of secondary processes during the decay of tritium and, secondly, on the possibility of tunneling reactions of such atoms with hydrogen isotope molecules in such a matrix.

T₂+H (5) T+DH _→ TD+H (6) D+TH _→ D+H (7) D+DH

D₂+H (8) и приводят к размещению атомов протия атомами дейтерия и трития в молекулах ТН и DH и образованию стабилизированных атомов протия.In the condensed deuterium-tritium fuel mixture, atoms are formed as a result of the interaction of β particles formed during the spontaneous radioactive decay of tritium T ₂ _ → T + T (1) D ₂ _ → D + D (2) HT _ → H + T ( 3) HD _ → H + D (4)
The formed hydrogen isotope atoms participate in those tunneling chemical reactions of the exchange of an atom with a molecule that are energetically possible at such temperatures T + TH

T ₂ + H (5) T + DH _ → TD + H (6) D + TH _ → D + H (7) D + DH

D ₂ + H (8) and lead to the placement of protium atoms by deuterium and tritium atoms in the TH and DH molecules and the formation of stabilized protium atoms.

= V_oT_o-K_т[T] ·H_o (9)

= V_oD_o-K_D[D] ·H_o (10)

= V_oH_o+(K_D[D] +K_т[T] (11) где [H] , [D] , [T] - концентрации свободных атомов соответственно протия, дейтерия и трития; V_o - скорость образования соответствующих атомов в твердой матрице изотопов водорода; H_o, D_o, T_o - концентрации связанных в молекулы атомов протия, дейтерия и трития; К_т-K_D - константы скорости реакций (5-8).The kinetic equations describing the processes of formation of hydrogen isotope atoms (reactions 1-4) and tunneling reactions of isotope exchange (5-8), which determine the rate of formation of protium in the system, have the form

= V _o T _o -K _t [T] · H _o (9)

= V _o D _o -K _D [D] · H _o (10)

= V _o H _o + (K _D [D] + K _t [T] (11) where [H], [D], [T] are the concentrations of free atoms of protium, deuterium, and tritium, respectively; V _o is the rate of formation of the corresponding atoms in the solid matrix of hydrogen isotopes; H _o , D _o , T _o are the concentrations of protium, deuterium, and tritium atoms bound to the molecules; K _t -K _D are reaction rate constants (5-8).

= V_oH_o+2K_D[D] H_o= V_oH_o+2V_oD_o= V_o(H_o+2D_o) ≈ 2V_oD_o (13)
Чтобы процесс химической фиксации атомов протия прошел эффективно за время экспозиции t необходимо выполнение условия [H] >>[D] или, так как [H] = 2V_oD_ot, а [D] = V_oD_o/K_DH_o, то
2V_oD_ot ≥ V_oD_o/K_DH_o. (14)
Из (14) следует условие для скорости реакции обмена
K_D

=

(15)
Экспериментально определено, что скорость туннельных реакций обмена лимитируется процессами диффузии атомов в низкотемпературных матрицах и зависимость константы скорости от температуры при Т≥ 4,2 К для атомов протия определяется выражением
K_D(T) = K_D(4,2) ˙ exp(E_a/T). (16) где E_a = 103∓5K - энергия активации процесса диффузии. Температуру проведения процесса определяем из условия (15) для t = 1 c;
K_D(T) = 25 с^-1. (17)
Учитывая, что K_D(4,2) = 2,3˙ 10^-3 см³/ /моль^-1˙ с^-1 и соответствует скорости процесса 10^-4 ˙ с^-1, получаем
К_D(T)/K_D(4,2)≥ 2,5˙ 10⁵. (18)
С другой стороны, из (16) получаем
K_D(T)/K_D(4,2) = exp

-

/exp

-

. (19)
Из соотношений (18) и (19) находим область изменения температуры проведения процесса регенерации Т = 8-9 К. Нижний предел соответствует Е_а = 108 К, верхний Е_а = 98 К. Снижение температуры выдержки ниже 8 К приводит к снижению эффективности образования атомов протия в реакциях обмена, а следовательно, и к снижению эффективности регенерации топливной смеси. Повышение температуры за верхний предел приводит к увеличению рекомбинации атомов изотопов водорода в системе, что также снижает эффективность регенерации смеси.Under the condition of quasistationarity for the atoms T and D from (9) and (10), taking into account the fact that in the fuel mixture T _o = d _o , and the exchange constants are almost equal, i.e., K _t = K _D , we obtain the values the concentrations of these atoms
[T] = [D] = V _o D _o / K _D ˙H _o (12)
Then the number of protium atoms appearing in the solid matrix can be estimated from (11) and (12) as

= V _o H _o + 2K _D [D] H _o = V _o H _o + 2V _o D _o = V _o (H _o + 2D _o ) ≈ 2V _o D _o (13)
For the process of chemical fixation of protium atoms to be effective during the exposure time t, it is necessary to fulfill the conditions [H] >> [D] or, since [H] = 2V _o D _o t, and [D] = V _o D _o / K _D H _o then
2V _o D _o t ≥ V _o D _o / K _D H _o . (14)
From (14) follows the condition for the rate of exchange reaction
K _D

=

(fifteen)
It was experimentally determined that the rate of tunneling exchange reactions is limited by the processes of atom diffusion in low-temperature matrices and the dependence of the rate constant on temperature at T≥ 4.2 K for protium atoms is determined by the expression
K _D (T) = K _D (4,2) ˙ exp (E _a / T). (16) where E _a = 103∓5K is the activation energy of the diffusion process. The temperature of the process is determined from condition (15) for t = 1 s;
K _D (T) = 25 s ^-1 . (17)
Considering that K _D (4,2) = 2,3˙ 10 ^-3 cm ³ / / mol ^-1 ˙ s ^-1 and corresponds to a process speed of 10 ^-4 ˙ s ^-1 , we get
K _D (T) / K _D (4,2) ≥ 2.5˙ 10 ⁵ . (eighteen)
On the other hand, from (16) we obtain
K _D (T) / K _D (4,2) = exp

-

/ exp

-

. (nineteen)
From relations (18) and (19) we find the region of variation in the temperature of the regeneration process T = 8–9 K. The lower limit corresponds to E _a = 108 K, the upper E _a = 98 K. A decrease in the holding temperature below 8 K leads to a decrease in the formation efficiency protium atoms in exchange reactions, and, consequently, to a decrease in the efficiency of regeneration of the fuel mixture. An increase in temperature beyond the upper limit leads to an increase in the recombination of hydrogen isotope atoms in the system, which also reduces the efficiency of the mixture regeneration.

= 1,6·10⁴c ≈ 4,4 ч
Образовавшиеся в тунельных реакциях атомы протия связываются в молекулы HJ в реакции
H+J _→ HJ (20)
Очищенную от протия порцию дейтерий-тритиевой смеси, пригодной для использования в термоядерный реактор (ТЯР), отделяют от молекулярных соединений йода путем нагрева реакционного сосуда до 26-77 К. После этого система готова для очистки новой порции смеси. Удаление оставшихся соединений йода проводят после завершения очистки всей смеси откачкой сосуда при повышении температуры его стенок до 240-300 К.The time required to convert all bound H atoms into free ones is
τ = H _o / (d [H] / dt =

= 1.6 · 10 ⁴ s ≈ 4.4 h
Protium atoms formed in tunneling reactions bind to HJ molecules in the reaction
H + J _ → HJ (20)
A portion of the deuterium-tritium mixture purified from protium, suitable for use in a thermonuclear reactor (TNR), is separated from the molecular compounds of iodine by heating the reaction vessel to 26-77 K. After this, the system is ready to clean a new portion of the mixture. Removal of the remaining iodine compounds is carried out after completion of the entire mixture purification by pumping the vessel with an increase in its wall temperature to 240-300 K.

 The regeneration of the deuterium-tritium fuel mixture of the TNR is carried out in the device, the circuit diagram of which is shown in the drawing.

The device includes a helium cryostat 1 with a node 2 for condensing the fuel mixture, a system 3 of preliminary preparation and supply of the mixture. The cryostat 1 has a vacuum casing 4, a nitrogen tank 5 with a screen 6, an adsorbent 7 and directly a helium bath 8 for filling with liquid helium. The node 2 for condensation of the fuel mixture is made in the form of a cylindrical steel vessel 9 with a heater 10 and two sealed jackets 11 and 12 located coaxially to the vessel 9. To prevent condensation of the fuel mixture in the upper part of the node 2, the mixture is supplied through a tube 13 having a vacuum jacket 14 and at the lower end of the hole, necessary for deposition of the gas fuel mixture on the cooled surface of the vessel 9. The system 3 for the preliminary preparation and supply of the fuel mixture includes a mixing chamber 15 with a node 16 Ivanov and gas pressure gauge 17 provided with a supply 18 and outlet nozzles 19 and a valve 20 connected to the container 21 for storing admixed J _2, and valves 22 and 23 to node 2 for condensing and maintaining the mixture. For evacuating the system 3 and the elements of the assembly 2, there is a fore-vacuum pump 24. The temperature of the assembly 2 is controlled by heat exchange with liquid helium from the bath 8 or liquid nitrogen, poured into the jacket 11 through the valve 25, and the heater 10. It is possible to vacuum through the valves 26, 27 and 28 and filling with helium from the cylinder 29 through valves 30, 27 and 28 of the airtight jackets 11 and 12 surrounding the vessel 9. The device includes a valve 31 for returning the regenerated mixture to the working chamber, as well as a collection of 32 separated protium with valve 33. Mix te a chamber 15 through a valve 34 connected to the working chamber TNR.

 The device operates as follows.

Vacuum the system 3 and the node 2 to 10 ^-3 mm RT. Art. Pour liquid nitrogen into the tank 5, fill the shirts 11, 12 and the bath 8 with helium gas from the cylinder 29 through valves 30, 27, 28 and 23. After cooling to the liquid nitrogen temperature of the unit 2 and cryostat 1, pour liquid helium into the bath 8 for condensation and holding the fuel mixture at a temperature of liquid helium (4.2 K) in node 2.

 The fuel mixture is prepared as follows.

From the cylinder 21 through the valve 20 make an inlet into the mixing chamber 15 J ₂ to a pressure of 0.2 mm RT. Art. The spent fuel mixture of composition T ₂ : D ₂ : H ₂ = 50: 50: 2 is injected from the TNR working chamber through the valve 34 to a total pressure of 10.4 mm Hg in the mixing chamber. Art. Node 16 produce gas mixing. The prepared fuel mixture through the valves 22 and 23 is served in the node 2 condensation of the mixture. In this case, the fuel mixture through the tube 13 continuously or in portions enters the bottom of the vessel 9, on the cooled surface of which it is condensed in the form of a solid matrix. The solid matrix is kept at 8 K for 4.4 hours. During the exposure, processes occur that lead to the binding of protium to iodine atoms. At the end of the exposure, the purified mixture is returned to the TNR working chamber. To do this, shirts 11 and 12 are pumped out to a pressure of 10 ^-4 mm Hg. Art. pump 24 through valves 26, 27 and 28. Then, valve 28 is closed and liquid nitrogen is supplied to jacket 11 through valve 25 and the temperature of vessel 9 is increased to 77 K, and through the tube 13 and through valves 23 and 31, the mixture is fed into the TNR working chamber. To clean the condensation unit from iodine compounds, shutting off valves 23 and 25, remove liquid nitrogen from the jacket 11, pumping it out through valves 26 and 27 with pump 24. Then turn on the heater 10, raise the temperature of the vessel 9 to 300 K and remove the remaining iodine compounds through the tube 13 and further through the valves 23 and 33 to the collector 32. After that, the device is ready for a new cycle of regeneration of the fuel mixture.

PRI me R. In the spent gas fuel mixture of the TNR composition T ₂ : D ₂ : H ₂ = 50: 50: 2, supplied from the reactor to the mixing chamber to a pressure of 10.2 mm RT. Art. gaseous iodine is introduced to a partial pressure of 0.2 mm Hg. Art. After mixing, the gas mixture is frozen on the cooled surface of unit 2. The frozen mixture is kept at 8 K for 4.4 hours. Atoms are formed in the solid matrix as a result of interaction with β particles emitted during tritium decay with the molecules of the initial fuel mixture, and tunneling chemical reactions of isotope exchange occur, leading to the replacement of protium atoms in TH and DH molecules by deuterium and tritium atoms, and to the formation of stabilized H atoms. A portion of deuterium-tritium purified from excess protium second mixture is recycled into the process chamber heating unit 2 fusion reactor to 77 C. The remaining on the walls of the iodine compounds are removed by evacuation of the vessel wall by heating it to 300 K.

As shown by calculations and experiments conducted at the Institute of Chemical Physics and Technology of the Academy of Sciences of the USSR, the implementation of the method and device allows, compared with the prototype, to reduce energy consumption from 10 ² eV / atom to 10 eV / atom of protium. In this case, the elimination of the stage of conversion of hydrogen isotopes into complex chemical compounds and vice versa, necessary for the separation of isotopes by hydrogen sulfide and laser methods, greatly simplifies the process of separation of protium, and also reduces energy consumption. (56) U.S. Patent No. 4,381,938, CL. B 01 D 59/00, 1983.

Claims (2)

 1. A method of regenerating a deuterium-tritium fuel mixture of a fusion reactor, comprising condensing the fuel mixture on a cold surface and separating isotopes, characterized in that, in order to reduce energy consumption and simplify the process of separating protium, iodine gas is introduced into the fuel mixture first, the condensed mixture is held at 8–9 K to bind excess protium with iodine atoms, and the separation of isotopes is carried out in two stages; at the first stage, the condensate is heated to 26–77 K and the purified excess protium fuel mixture; in the second stage, the mixture is heated to 240-300 K, removing compounds of iodine with protium.  2. A device for the regeneration of a deuterium-tritium fuel mixture of a fusion reactor containing a helium cryostat with a node for condensing the mixture and a liquid nitrogen and helium supply system, a preliminary preparation and supply system for the mixture and an isotope separation unit, characterized in that, in order to reduce energy consumption and simplification of the protium separation process, the mixture condensation unit is made in the form of a sealed cylindrical vessel, and the isotope separation unit is made in the form of two sealed shirts, installed nnyh coaxially with the cylindrical vessel and a heater mounted on a bottom of the cylindrical vessel.