RU2068203C1 - Nuclear reactor for vehicles - Google Patents

Abstract

FIELD: nuclear engineering; spacecraft nuclear reactors. SUBSTANCE: reactor core is divided into two subcores which are mounted in tandem on reactor longitudinal axis; one of subcores is subcritical and spaced from other subcore at distance ranging within values of which maximum is chosen from inequality

, where Dcore is diameter of cores, sq.m; π is pi number equal to 3.14; Fact. is multiplication factor of neutrons in critical subcore; Pn is return probability of neutrons formed in critical subcore and those returned to subcritical subcore; minimum value is chosen from set of inequalities

, where S is neutron density at end of critical subcore in power condition (m^-3s^-1); K_∞ is subcritical subcore multiplication factor; P is leakage probability of neutrons produced in critical subcore through gap between subcores; Q.h.r. is permissible power of heat-removal system in subcritical subcore in power condition, W; Fact. is effective multiplication factor of critical subcore in shutdown state; Σ^k is material neutron absorption macrosection between ends of subcores, (m^-1); Σ_fuel is fissionable material absorption macrosection in subcritical subcore, (m^-1); ΔK_s.s. is safety system efficiency in reactor subcritical subcore; Σ_a is subcritical subcore absorption macrosection, (m^-1); γ_fuel is nuclear concentration of fissionable material in subcritical subcore, (m^-3). EFFECT: reduced cost of reactor and facilitated manufacture along with reduced size and mass of reactor and vehicle as a whole; facilitated transfer from one operating condition of vehicle to other and provision for operation in two modes; reduced effect of high temperatures and vacuum on reactor components. 7 cl, 1 dwg

Description

 The invention relates to nuclear engineering, and in particular to nuclear reactors of transport installations, for example, for space purposes.

 A nuclear reactor is known that contains in a strong casing an active zone divided into two parts, a cooling system and regulatory bodies (see USSR author's certificate N 786619, class G 21C 1/28, 1979).

 The disadvantages of this solution arise mainly due to the fact that parts of the zone in the reactor have a concentric arrangement and, as a result of this, the active zone in this reactor has a much larger side surface than in the "single-zone" reactor. This leads to an increase in neutron leakage and to the need to increase both the size of the zone itself and the entire reactor as a whole. In addition, with such a geometry, for regulating the central part of the zone, it is necessary to use the CPS bodies of the rod type, because of which the vertical dimension of the reactor is doubled. In addition, neutron fluxes and spectra established in concentrically located parts of the zone are strongly dependent on each other. This does not allow creating subbands with various neutron-physical characteristics that could work in different modes. It should also be noted that in the event of a muffling of one of the parts of the zone (especially peripheral) due to the strong influence of these parts on each other in the unmuffled part of the zone, the reactivity margin should be excessive.

 The closest in its technical essence and the achieved result to the proposed one is a nuclear reactor of a transport installation, containing an active zone located in a strong casing with fuel elements, around which control drums are installed, and equipped with cooling systems and a working fluid (see Space engines. M. Mir , 1988, p. 338, 339, Fig. 4.44).

 The active zone of the nuclear reactor of the transport apparatus must be operational in both energy and motor modes. However, the implementation of this requirement is not easy to ensure, as in the motor mode, operating temperatures in individual parts of the zone reach 3000 K. Therefore, despite the relatively small fraction of the operating time of the core in the motor mode, it is natural that the design decisions and selection of materials in the core should be determined by the maximum temperature values, although it is obvious it is economically unprofitable to create a zone that will operate at the maximum mode of only 3-4 hours out of the 5-7 years assigned to it. In addition, the operation of fuel cells in vacuum and high temperatures leads to technological problems associated with the need for special coatings to prevent diffusion entrainment of fuel and the introduction of refractory metal carbides in the fuel composition. This is not only expensive and technologically difficult, but also entails an increase in the mass of fuel elements loaded into the active zone, which, ultimately, leads to an increase in the weight and size characteristics of both the active zone and the reactor as a whole and in many cases, especially for transport installations, it is completely unacceptable. It should also be noted that increasing the dimensions of the reactor leads to a decrease in the efficiency of the control drums, and therefore requires the use of an additional control system in the form of, for example, absorbing rods, which again leads to an increase in capital costs and overall dimensions of the reactor.

 It is also disadvantageous to provide propulsion and energy regimes with the help of several nuclear reactors. And first of all, this is due to an excessive increase in the mass and size of the transport apparatus.

 Therefore, the technical result, which the invention is intended to achieve, is to reduce the cost of a nuclear reactor and increase the manufacturability of its manufacture while minimizing the weight and size characteristics of both the nuclear reactor itself and the entire transport apparatus as a whole, and increase the efficiency of transitions from one operating mode of the transport installation to another mode and in ensuring the possibility of simultaneously creating two modes, in reducing the effects of high temperatures and vacuum to elements of a nuclear reactor.

, где D_а.з диаметр активных зон (м); π число p, равное 3,14; К_эф коэффициент размножения нейтронов в критичной подзоне; P_п вероятность возвращения нейтронов, образовавшихся в критичной подзоне и попавших в подкритичную подзону обратно, а минимальное значение выбрано из системы неравенств

где S плотность нейтронов на торце критической подзоны в энергетическом режиме (м^-3c^-1);
K_∞ коэффициент размножения подкритичной зоны;
P вероятность утечки нейтронов, образовавшихся в критичной подзоне, через зазор между подзонами;
Q_тс допустимая мощность системы теплосъема в подкритичной подзоне в энергетическом режиме (Вт);
K_эф эффективный коэффициент размножения критичной подзоны в заглушенном состоянии;
Σ $\genfrac{}{}{0ex}{}{\text{к}}{\text{а}}$ макросечение поглощения нейтронов материалом, находящимся между торцами подзон, (м^-1);
Σ_а.топ макросечение поглощения делящегося материала в подкритичной подзоне (м^-1);
ΔK_суз эффективность СУЗ подкритичной подзоны реактора;
Σ_a макросечение поглощения подкритичной подзоны (м_-1);
γ_топ ядерная концентрация делящегося материала подкритичной подзоны (м^-3),
Указанный технический результат достигается также за счет того, что тепловыделяющие элементы критичной подзоны снаряжены топливом, изготовленным на основе высокоплотных по урану сплавов, таких как, например, нитриды или карбонитриды урана, а подкритичная подзона загружена высокотемпературными тепловыделяющими элементами, и, кроме того, за счет того, что подзоны выполнены из блоков твердого замедлителя, между которыми с зазором установлены технологические каналы, заполненные сборками с тепловыделяющими элементами, при этом во входных частях технологических каналов установлены дросселирующие элементы, а на выходах из технологических каналов подкритичной подзоны с высокотемпературными тепловыделяющими элементами установлены сопла Лаваля.The specified technical result is achieved due to the fact that in the nuclear reactor of the transport installation containing an active zone located in a strong body with fuel elements around which control drums are installed, and equipped with cooling systems and a working fluid, the subzones are mounted one after the other one after the other of the subzones is subcritical and located at a distance from the other subzone, the value of which lies in a range whose maximum value is selected from the inequality

where D _a.z diameter of the active zones (m); π is a number p equal to 3.14; To _ef the neutron multiplication coefficient in the critical subband; P _{p the} probability of the return of neutrons formed in the critical subband and back into the subcritical subband, and the minimum value is selected from the system of inequalities

where S is the neutron density at the end of the critical subband in the energy mode (m ^-3 s ^-1 );
K _∞ multiplication factor of the subcritical zone;
P is the probability of leakage of neutrons formed in the critical subband through the gap between the subbands;
Q _tf permissible power of the heat removal system in the subcritical subzone in the energy mode (W);
K _eff effective multiplication factor of the critical subzone in the muffled state;
Σ $\genfrac{}{}{0ex}{}{\text{to}}{\text{a}}$ macro-section of neutron absorption by the material located between the ends of the subbands, (m ^-1 );
Σ a. _Top macroscopic absorption of fissile material in the subcritical subzone (m ^-1 );
ΔK _CPS CPS efficiency subband subcritical reactor;
Σ _a macro section of the absorption of the subcritical subzone (m _-1 );
γ _top nuclear concentration of fissile material of the subcritical subzone (m ^-3 ),
The specified technical result is also achieved due to the fact that the fuel elements of the critical subzone are equipped with fuel made on the basis of high-density uranium alloys, such as, for example, nitrides or carbonitrides of uranium, and the subcritical subzone is loaded with high-temperature fuel elements, and, in addition, due to the fact that the subzones are made of blocks of solid moderator, between which technological channels are installed with a gap, filled with assemblies with fuel elements, while in the input throttle elements are installed in parts of the technological channels, and Laval nozzles are installed at the exits from the technological channels of the subcritical subzone with high-temperature fuel elements.

 The invention is illustrated by the drawing, which shows a longitudinal section of a nuclear reactor, consisting of a housing 1, which houses the active zone, divided into two parts of the subzone 2 and 3, located one after another with a gap on the same longitudinal axis. Subzones 2 and 3 are surrounded by side 4 and 5 and end 6 and 7 reflectors. In addition, the subzone 2 from the side closest to the subzone 3 of the end is limited by an intermediate reflector 8. In the nuclear reactor there are three collector systems: the upper 9, lower 10 and intermediate 11. Thermal protection 12 is installed above the upper system 9, and shadow radiation is installed under the lower system 10 protection 13, on which the drives of the 14 systems of regulating active subzones 2 and 3 are fixed. In subzones 2 and 3 there are blocks of a solid moderator 15, with a gap between which technological channels are installed 16. A fuel assembly is placed in channels 16 17 with fuel elements 18. At the inlet of the technological channels 16 throttling devices 19 are installed 19. In addition, the technological channels 16 of the subzone 3 at the outlet are equipped with Laval nozzles 20. In the side reflectors 4 there are executive bodies of reactivity control systems for the subzones 2 and 3 (for example, drum type), while the reflectors 4 are pierced by channels 22 of the cooling path. Each drum has a segment of neutron-absorbing material and is capable of independent rotation around its axis, i.e., equipped with its own drive (not shown in the drawing). The system of upper collectors 9 includes a distributing collector 23 for cooling nozzles 20 and technological channels 16 of subzone 3 and a distributing collector 24 for cooling the upper reflector 7 and retarder blocks 15. The system of intermediate collectors 11, located in the gap between subzones 2 and 3, includes a collecting manifold 25 cooling the reflector 7 and the moderator blocks of the subzone 3, the collecting manifold 26 for cooling the fuel assemblies 17 of the subzone 3, the distributing collector 27 for supplying the working fluid to the fuel assembly 17 of the subzone 3, the distributing collector 28 for supplying the working fluid to the fuel assemblies 17 of subzone 2, distributing the collector 29 for cooling the fuel assemblies 17 of subzone 2, connected by bypass 30 to the collecting collector 25 (collects the coolant cooling blocks of the moderator 15 of subzone 2). The system of lower collectors 10 includes a distributing collector 31 for cooling the lower 6 and intermediate 8 end reflectors and retarder blocks 15 of subzone 2, a collecting manifold 32 for cooling the technological channels 16 of subzone 2, a collecting manifold 33 for cooling fuel assemblies 17 of subzone 2. A collecting manifold 33 with a pipe 34, which has a shut-off valve 35 connected to the distributing manifold 27. The lower manifold system 10 is located in a cavity 36 formed between the subzone 2 and the radiation shield 13. The collecting manifold 26 is connected to the nozzles and 37 with a distributing collector 28. Behind the shadow protection 13 there is a TEMP thermal electric machine converter (not shown in the drawing) connected to the supply pipelines 38, 39 and outlet 40 of the coolant circuit.

 The operation of the proposed reactor can be demonstrated by the example of its use in a spacecraft.

 When the space complex is deployed in a reference orbit, the nuclear reactor is initially brought to the energy mode of operation.

 For this, the coolant from TEMP is supplied through pipe 38 to the distributing collectors 24 and 31. From the distributing collector 24, the coolant is sent to the gaps between the retarder blocks 15 of the subzone 3. Then, the coolant enters the collecting manifold 25, and from there by the bypass 30 into the collection and distribution manifold 29 .

 The coolant entering the distribution manifold 31 is sent to cool the end 6 and intermediate 8 reflectors made, for example, of beryllium-containing materials with high inhibitory properties, as well as to cool the retarder blocks 15 of subzone 2, and enter the collector 29, where it is mixed with previously the specified flow of coolant, thus fulfilling the function of cooling the main structural elements of both parts of the active zone. The main coolant stream supplied from the TEMP through the pipeline 39 also enters the collector 29.

 The combined stream enters cooling by convection through the walls of the technological channels 16 of the subzone 2 of the fuel elements 18. To simplify the manufacture, reduce the number of structural materials in the subzone 2 and reduce its dimensions, the fuel elements 18 of this part of the active zone can be made without a special coating (shell) and based on fuel uranium-intensive compositions (for example, based on uranium mononitride). From subzone 2, the coolant is collected in the collector 32 and returned through the pipeline 40 to the TEMP.

 In the muffled state, the regulatory bodies of 21 subzones 2 and 3, their sectors, on which the absorber layer is applied, are directed towards the subzones 2 and 3, respectively, therefore, to bring the reactor core to the energy level of power, after the coolant circulates through the cooling system, the regulation bodies of the 21 subzones are turned 2 so as to increase the distance between the absorber and subzone 2. In subzone 2, a chain reaction of neutron fission begins, the power of which begins to decrease as the absorber moves away from subzone 2 asti.

 When the power level in subzone 2 reaches the calculated value, it (i.e., the power level) is maintained using the same regulatory bodies of subzone 2, changing the angle of rotation of the sector with the absorber relative to this subzone, and the heat generated in subzone 2 is used in the TEMP operating Brighton thermodynamic cycle for the production of electrical energy.

где S плотность нейтронов на торце критичной подзоны в энергетическом режиме (м^-3c^-1);
K_∞ коэффициент размножения подкритичной зоны;
P вероятность утечки нейтронов, образовавшихся в критичной подзоне, через зазор между подзонами;
Q_тс допустимая мощность системы теплосъема в подкритичной подзоне в энергетическом режиме (Вт);
K_эф эффективный коэффициент размножения критичной подзоны в заглушенном состоянии;
Σ $\genfrac{}{}{0ex}{}{\text{к}}{\text{а}}$ макросечение поглощения нейтронов материалом, находящимся между торцами подзон, (м^-1);
Σ_а.топ макросечение поглощения делящегося материала в подкритичной подзоне (м^-1);
ΔK_суз эффективность СУЗ подкритичной подзоны реактора;
Σ_a макросечение поглощения подкритичной подзоны (м^-1);
_топ ядерная концентрация делящегося материала подкритичной подзоны (м^-3),
cвязь по нейтронному потоку подзоны 2 и в находящейся в заглушенном состоянии подзоны 3 настолько слабая, что это позволяет эксплуатировать подзону 2 отдельно от подзоны 3.Since subzones 2 and 3 are installed on the longitudinal axis of the reactor one above the other at a distance that is not less than the value chosen from the system of inequalities

where S is the neutron density at the end of the critical subband in the energy mode (m ^-3 s ^-1 );
K _∞ multiplication factor of the subcritical zone;
P is the probability of leakage of neutrons formed in the critical subband through the gap between the subbands;
Q _tf permissible power of the heat removal system in the subcritical subzone in the energy mode (W);
K _eff effective multiplication factor of the critical subzone in the muffled state;
Σ $\genfrac{}{}{0ex}{}{\text{to}}{\text{a}}$ macro-section of neutron absorption by the material located between the ends of the subbands, (m ^-1 );
Σ a. _Top macroscopic absorption of fissile material in the subcritical subzone (m ^-1 );
ΔK _CPS CPS efficiency subband subcritical reactor;
Σ _a macro section of the absorption of the subcritical subzone (m ^-1 );
_top nuclear concentration of fissile material of the subcritical subzone (m ^-3 ),
The neutron flux coupling of subzone 2 and the subzone 3 in the muffled state is so weak that it allows the operation of subzone 2 separately from subzone 3.

 The transition of the reactor from energy to motor mode is carried out in the following steps "steps."

 The working fluid (for example, hydrogen) from a special supply system, for example tanks (not shown in the drawing), through the radiation protection enters the cavity 36, from where it passes through the channels 22 first into the space between the side reflectors 4 of the two parts of the active zone, and then into the distribution collector 23. From the distributing collector 23, the RT is sent to collect the body by convection through the walls of the technological channels 16 from the fuel elements 18 and enters the collecting manifold 26, from which it enters the collector 28 through the nozzles 37 and passing through the core The rural elements 19, which ensure uniform consumption of the RT, are distributed through the technological channels 16, cooling the fuel assemblies 17 of the subzone 2. Then, after passing the channels, the RT is collected in the collector 33. From the collector 33 of the RT through pipelines 34, opening valve 35 under the action of overpressure, to the collector 27, after which it passes through the throttle elements 19 of the technological channels 16 of the subzone 3 to its fuel assemblies 17, filled with, for example, high-temperature fuel elements 18. Here, the working fluid is on the engine IU can be heated to a temperature of about 3000 K. From the subband working body 3 through the Laval nozzle 20 thrown outwards and creates the reactive thrust conveying installation.

 To bring the reactor core to a power level corresponding to the propulsion mode of the transport unit, the regulators of the subzone 3 are rotated by the absorbing layer at a certain angle from the subzone 3 and give it the positive reactivity necessary to raise the power to an intermediate level. Because of this, excessive reactivity arises in subzone 2, which, with the help of regulators 21 of subzone 2, is compensated by turning the regulators with an absorbing layer in the direction of this part of the active zone. Moreover, the number of such steps is determined by the necessary speed of transition to motor mode and nuclear safety requirements.

, где D_а.з диаметр активной зоны (м); π число p, равное 3,14; К_эф - коэффициент размножения нейтронов в критичной подзоне; P_п вероятность возвращения нейтронов, образовавшихся в критичной подзоне и попавших в подкритичную подзону обратно.Since subzone 3 is intended solely to ensure the propulsion mode and functions only in conjunction with subzone 2, it is subcritical and contains less fuel than is necessary to create a critical mass and a reserve of uranium for it to burn out. This makes it possible to reduce the weight and size characteristics of subzone 3. In this case, for the interaction of neutron fluxes of the active subzones 2 and 3 of the reactor and the achievement of the critical state in the core as a whole, they are placed with a gap whose value does not exceed the value obtained from the inequality

where D _a.z diameter of the core (m); π is a number p equal to 3.14; To _ef is the neutron multiplication coefficient in the critical subband; P _{p the} probability of the return of neutrons formed in the critical subband and falling back into the subcritical subband.

 The transition from the motor to the energy mode is carried out in similar "steps", but in the "opposite" direction: the regulatory authorities 21 report negative reactivity to subzone 3 and, after removing residual heat from it, turn off the supply system of the working fluid.

 It should be noted that this invention allows to simultaneously obtain two different power values necessary for the electrification of a transport installation and for its movement in space, to quickly switch from one operating mode to another mode and from one power level to another power level due to the autonomy of the working fluid system and cooling systems and the weak effect of poisoning of subzone 3 on the functioning of the reactor as a whole.

 In addition, since subzone 3, in which a very rigid neutron spectrum is created in the motor mode, is separated from the command compartment of the transport apparatus, in addition to shadow protection 13, subzone 2 can reduce the thickness of the biological protection in front of the command compartment and, thereby, further reduce the overall dimensions of the entire apparatus generally.

 The silencing of the reactor from any mode is carried out by the joint installation of the absorbing layers of the regulatory bodies 21 opposite to the subzones 2 and 3.

Claims (7)

1. A nuclear reactor of a transport installation, comprising an active zone located in a strong casing with heat-generating elements, around which control drums are installed, and equipped with cooling systems and a working fluid, characterized in that the active zone is divided into two slides installed on the longitudinal axis of the reactor one after the other another, one of the subzones is subcritical and is located at a distance from the other subzone, the value of which lies in a range whose maximum value is chosen from the inequality

where D _a.z. diameter of active zones, m;
To _ef the neutron multiplication coefficient in the critical subband;
P _{n the} probability of the return of neutrons formed in the critical subband and falling back into the subcritical subband,
and the minimum value is selected from the system of inequalities

where S is the neutron density at the end of the critical subband in the energy mode, m ^-3 s ^-1 ;
K _∞ multiplication factor of the subcritical zone;
P is the probability of leakage of neutrons formed in the critical subband through the gap between the subbands;
Q _t.s. permissible power of the heat removal system in the subcritical subzone in the energy mode, W;
K _{eff is the} effective multiplication factor of the critical subzone in the muffled state;
Σ $\genfrac{}{}{0ex}{}{\text{to}}{\text{a}}$ macro-section of neutron absorption by the material located between the ends of the subbands, m ^-1 ;
Σ _{a, top} macroscopic absorption of fissile material in the subcritical subzone, m ^-1 ;
ΔK _CPS CPS efficiency subband subcritical reactor;
Σ _a macro section of the absorption of the subcritical subzone, m ^-1 ;
γ _top nuclear concentration of fissile material of the subcritical subzone, m ^-3 .  2. The reactor according to claim 1, characterized in that the fuel elements of the critical subzone are equipped with fuel made on the basis of high-density uranium alloys.  3. The reactor according to claim 1, characterized in that the subcritical zone is equipped with high-temperature fuel elements.  4. The reactor according to paragraphs. 1 and 2, characterized in that uranium nitrides or carbonitrides are used as fuel in the critical subzone.  5. The reactor according to paragraphs. 1 to 4, characterized in that the subzones are made of blocks of solid moderator, between which technological channels are installed with a gap, filled with assemblies with fuel elements.  6. The reactor according to paragraphs. 1 and 5, characterized in that in the inlet parts of the technological channels throttling elements are installed.  7. The reactor according to paragraphs. 1, 5 and 6, characterized in that at the exits from the technological channels of the subcritical subzone with high-temperature fuel elements, Laval nozzles are installed.