DE1281049B - Heterogeneous pressure vessel reactor - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

G21d

German class: 21g-21/24

Number: 1 281049

File number: P 12 81 049.0-33 (S 92534)

Filing date: August 8, 1964

Opening day: October 24, 1968

The present invention relates to a heterogeneous pressure vessel reactor with in its Core arranged like a grid of fuel rods, moderated and cooled with water of supercritical pressure , provides steam at supercritical temperature and pressure values, and through both rods and also regulated by an adjustable valve of a cooling water supply line ending at the pressure vessel jacket will.

It is aimed at in reactor technology, with water-cooled and moderated nuclear reactors ever higher pressures and temperatures of the generated steam and thus higher efficiencies to reach. It is considered to operate such reactors with water in the supercritical state. Such supercritical water reactors are generally planned as so-called pressure tube reactors, d. H. as reactors in which the high-pressure coolant is guided in tubes, which separate the coolant from the generally pressureless moderator.

However, there are also proposals for nuclear reactors of the pressure vessel type with supercritical water Pressure and supercritical temperature become known (see French patent specification 1 138 847). The task on which this proposal is based was that of boiling water reactors Avoid vapor bubbles that may cause instability.

Proceeding from this prior art, the object of the present invention consists in Creation of a more even flow distribution within the reactor core as well as a better one Stabilization of the operating behavior.

To solve this problem, according to the invention, a second valve is provided with an adjustable valve Water supply with a grid-like flow between the fuel rods and parallel to them arranged tubes connected, which penetrate the core and fixed at the outlet opening Restrictions included.

The coolant flows through the reactor core according to the countercurrent principle: The partial flow flowing through the tubes arranged between the fuel rods acts first of the coolant as a moderator. After exiting the pipes, this partial flow is diverted, mixes with the remaining coolant flow fed into the reactor core and now flows in the opposite direction along the fuel rods. The coolant flow heats up in the process by the heterogeneous pressure vessel reactor carried over by the fuel rods

Applicant:

Siemens Aktiengesellschaft, Berlin and Munich, 8520 Erlangen, Werner-von-Siemens-Str. 50

Named as inventor:

Dr. rer. nat. Wolfgang Braun,

Dipl.-Ing. Franz Winkler, 8520 Erlangen

gene heat, with that of the coolant in turn passing through the pipes to the moderator Coolant partial flow transferred heat is able to change its density. The pipes are therefore nothing more than light guide tubes without any thermal insulation. In terms of pressure, they only get through the resulting flow resistances claimed. As will be explained in more detail later, this has a fundamental effect Structure of the reactor core, the self-regulation and self-stabilization of the entire reactor.

With reference to FIGS. 1 to 5, this is the present one Reactor structure underlying principle explained in more detail.

In Fig. 1 a and 1 b the basic structure of the reactor core is shown schematically. The clarity For the sake of this, only one tube and two fuel rods are shown, which of course contain them a real reactor core has a multitude of such components.

Inside the pressure vessel 1 is the reactor core, which consists of tubes 2, hereinafter moderator tubes called, and fuel rods 3 is constructed. The coolant 4 flows under a pressure of 250 up to 300 at via lines 41 and 43 into the reactor pressure vessel. This is in line 43 Control valve 44 installed, which controls the inflow of the coolant component, which is initially intended to act as a moderator, controls; The control valve 42 is installed in the line 41, which controls the inflow of that coolant component, the is fed directly to the fuel assemblies, regulates. The coolant from line 43 initially flows into the moderator tube 2 and leaves it at the other end of the same and flows together with it the coolant from the line 41 up along the fuel rods 3 and exits via the line 5 the reactor pressure vessel. According to Fig. Ib is the arrangement of fuel rods and moderator tubes

809 628/1404

spatially reversed, the flow path of the cooling principle arranged moderator pipes by means of or the moderator is in principle the same. With both variants, i.e. the Reakwie in Fig. la. tork core made of individual moderator tubes and combustion

The external circuit of the coolant is in rods and the reactor core is made up of individual fuel F i g. 2 a for the open circuit, i.e. for the 5 element units, this is of course the case direct feed into the turbine, in Fig.2b for the same coolant flow principle, so that the closed circuit, i.e. with the same operating characteristics in between, are to be expected, circuit of heat exchangers recorded. Ab- These operating characteristics result from

shielding devices, thermal shields, etc. have the following phenomena. The water that first are not shown for reasons of clarity. io serves as moderator, comes from line 43, In contrast to the conventional water flows into the upper collecting space of the reactor pressure-cooled Reactors in which the increase of the storage vessel 1 and flows from there into the at the top cifical enthalpy of the coolant in the reactor only holding plate attached moderator tubes. It will is about up to 50 kcal / kg, the increase in the moderating water in the specific enthalpy in one with supercritical 15 pipes through the water outside these pipes operated reactor is set about ten times the flowing, cooling purposes hot because the coolant heats water in one pass. That from the moderator pipes Warmer water exiting through the reactor core to its final temperature mixes with the is brought. The coolant throughput is accordingly reduced through the holes in the lower retaining plate less. In order to still have a colder one that is only used for cooling purposes for a good 20 kicking Heat transfer sufficient flow rate water, which via line 41 into the reactor of the coolant has reached the pressure vessel along the fuel rods. Achieve that with the moderator, the cooling channel cross-section must be proportionate- water mixed cooling water that has a temperature be kept moderately small. In addition to that, in has from about 280 to 300 ° C, is now with the turn the supercritical temperature and thus the 25 flows of the fuel rods are heated to around 500 ° C, low density of the cooling water inside the core a subdivision of the water space into one end of the fuel rods in the radial direction hot coolant and a neutron-physically an annular collecting space is introduced, which with cheaper colder moderator is necessary to verbunein the outlet nozzle of the reactor vessel optimal volume ratio between water and 30 den.

Uranium as well as a high specific liter output in these flow conditions are also in one

Reach reactor core. These two fuel assembly requirements, as shown in FIG. 4 clippings will be made is represented by the flow mode already shown. Such a one away of the coolant through the parallel to the fuel assembly contains in addition to the fashion rods arranged tubes, the size of the transverse 35 rator tubes 2 and fuel rods 3 spacers 31 Section of the water-filled core space and support elements 32 to the upper and lower outside of the tubes 2 as well as those in Fig. 3a, 3b and rod holding plates to be attached as well as an outer 3 c shown grid cross-sections with the focal baffle 33. In this representation is also on unstäben 3 and moderator pipes 2 met. The throttle 21 closes at the first end of the moderator tubes identify themselves for the hexagonal grid and the octagonal 40.

grid according to Fig. 3c and 3d smallest possible values The self-regulating behavior of such a

the quotient of the total cross-section of the reactor built with can be calculated as follows clarify filled core space outside of the. The one flowing through the moderator pipes Pipes 2 through the total cross-section of the water pressure water is due to the over the pipe wallunin the tubes 2 at a predetermined value of the heat transferred from the hotter cooling quotient From the latter cross-section, the more water is heated, the lower the pressure cross-section of the assembly of the fuel rods 3. The water flow rate is. Will the pressurized water flow The value of the latter quotient should be set in such a way that the mean pressure water temperature is known Way is in the order of magnitude of 1 temperature in the vicinity of the critical temperature, lie. So every change in throughput causes a relatively large one

At this point it should be noted that there is a change in density, since it is in the critical range the reactor core from a uniform grid temperature changes the density of the water very strongly, Such fuel rods and moderator tubes together. However, such a large decrease in density causes a mensetzt that at corresponding upper and lower reinforced under-moderation, which is a shift Retaining plates, like those from the usual reactor technology of the neutron spectrum and thus a reactivinics are known ago, can be attached. Caused to decrease in performance. A decrease in the mutual reaction Spacers can in themselves cause activity but lower reactor performance, known components are used. It goes without saying that the temperature of the will decrease again Of course, it is also possible to facilitate moderators and an increase in the density of the same, The interchangeability of individual fuel rods means that one is always isolated by the control valve 44 Reactor core in fuel assemblies can be adjusted to a state that can be set up. These parts the per se known from the previous phenomena are reinforced by fixed one-reactor technology common geometric external molded throttle points 21 in the moderator pipes, men can have. In the event that the react- your mode of action is the following: Gate core made up of individual fuel assemblies. 65 Rises in the fuel rods of a fuel assembly is built, it should be noted that this fuel or only in part of the rods the power density element units from a large number of, the coolant temperature increases in the cooling fuel rods and in between, like a grid, to the canal and thus also to the moderator pipes

5 6

heat transferred to the moderator, as already I. a power control of the reactor as well as a described. Within the moderator relief of the control rods in a power pipe, this leads to an increase in the moderator temperature change,

and thus to an increase in the specific volume 2. a compensation of the excess reactivities, mens of the moderator. The greater specific Vo- 5 _{3 <dne} reduction in the number of required

lumen of this moderator results in a higher borrowed control rods

Flow velocity and thus also a. . _Tr .., '

higher pressure loss at the throttle. The 4th a change in the conversion rate of the

Throttle caused a decrease in throughput in the mode reactor and

ratorrohr follows the relationship io 5. an automatic flattening of the radial and

axial power density distribution and the Abi / lg / l /> construction of local power peaks in the reactor GF- I / ~ l ~~~ core, in particular by means of the ratorrohren in the Moder arranged throttle bodies

etc. where G = the pressurized water throughput, F of 15 either at the end of the moderator tubes or

Narrowest flow cross-section of the throttle point, g which is ^{also used in} places with a low moderator density

Acceleration due to gravity, Ap the driving pressure difference amplification of the response sensitivity

(given by the coolant pump), ξ of which are contradicted.

The static coefficient of the throttle and ν the specific Vo- Beyond these measures lumen of the water flowing through the throttle point is a further equalization of the temperature is. The decrease in throughput caused by the temperature difference between the individual cooling water increases of the specific volume is created and flows over the cross section of the reactor core is described by this formula is effected by arranging a mixing chamber further increase of the pressurized water temperature range, which extends over the whole core cross-section and thus an additional decrease in moderator »5 extends.

density in the fuel assembly. Such an additional facility is in If the moderator density were to decrease, the new F i g. 5 shown, again in a schematic electron flow and thus the power density in the cross section of a single fuel assembly. These Fuel assembly and in adjacent fuel sits with its upper retaining plate on a flange assembly away. The thus automatically acting 30 ring of the reactor vessel and engages with the Control circuit: fuel rod output-cooling water temperature, pipe socket 39 on the lower retaining plate - moderator water temperature - throughput drop - the partition wall 38 of the lower coolant collecting moderator density - neutron flux density - power space ascending feed pipe stub. As density leads to a new state of equilibrium, described, this mixes through this pipe which the originally locally elevated 35 clip flowing in cooling water with the from the Power density of the power density of adjacent moderator pipes 2 flowing out, already heating zones aligns. The still existing control deviation moderator water then rises along the distillery and the stability of the control loop are very rods 3 upwards and thereby reached the over-strong due to the design of the moderator throttle critical condition. In the room above the and from the position of the working point of the mode 40 fuel rods 3, a mixing of the Einratortemperatur In relation to the critical temperatures, supercritical cooling water flows take place, temperature determined. which is then through the upper openings

The built-in chokes therefore act in addition to the support device 32 for the lower holding plate and the reduction of local power peaks above all along the superheater fuel rods 35 in the through Things also a river flattening. This superheater channel 36, which is automatically formed 45 after the baffle 33 The achieved flattening of the power density distribution move down and through the boiler nozzle 13 as seen across the reactor cross-section, working fluid can still be fed to the turbine. Of the be reinforced by that of the expected cross-section of such a fuel assembly Lower power density can be less throttled z. Be square, with the superheaters and At points of high power density, stronger channels with the superheater fuel rods 35 into the is throttled. In this context, corners should come to rest on it. Because of the higher tempo, The superheater fuel rods 35 must not only have radial flow temperatures Flattening through this new reactor shape enables circumstances to be made of other materials, but that due to the temperature and the, as the fuel rods 3.

Density distribution in the moderator water in an axial 55 It is obvious that such a reactor Direction of the greatest density at the two reactors during start-up and shutdown due to the large density ends prevails, so that an axial change in the flow of the water is an extraordinarily large one flattening is achieved. This extensive leveling experience changes in reactivity, which is caused by the rule of the radial and axial power density distribution alone might not be compensated also benefit the resilience of the fuel rods, 60 den. It is therefore suggested that the Kühida different fuel rod performances in particular water in a known manner during the start-up and at the above-mentioned high coolant temperatures to shutdown a liquid absorbent such. B. Big differences in temperature at the ends of the acid. Since that with the absorbent Could lead cooling channels. loaded coolant is not relaxed in the turbine

In summary, changing the 65 should be made possible during startup and shutdown Moderator water throughput circulated with the help of the external via an auxiliary cooler 6. To the surrounding area The control valve and the use of the throttling of the flow path serve the purposes shown in FIG. 2 put valves 51 and 74 in the moderator pipes

Bridging line 73 leads via a separation system 72, which has the task of starting up to clean the coolant from the added absorber medium as the temperature rises, so that when the turbine 8 is switched on, i.e. when the valves 51 and 74 are switched over, there is no longer any boric acid in the Coolant is present. From this point on, the self-regulation is also fully effective. In the Fig. 2 drawn line 7 with the feed valve 71 serves to feed the to absorber into the coolant circuit during shutdown. This bypass line 73 with the auxiliary cooler 6 can of course also be used to cool the reactor in the Use in the event of a turbine emergency shutdown and to dissipate the decay heat from the reactor Find. Feeding the absorber via line 7 also enables shutdown of the reactor if the built-in control rods fail or are insufficient.

In addition to the above-mentioned options for regulating the reactor, control rods can also be used will. These can, in a manner known per se, in intermediate spaces between the fuel assembly units be arranged, but also z. B. immerse in moderator pipes and thus next to the normal absorption effect cause an additional choke effect, which in turn again in already as described reduces the neutron flux at the point in question. Control rods can can of course also be used at fuel rod positions, with the said reactor core structure especially the use of finger control rods - the absorber fingers can do this be arranged in both fuel rod and moderator tube positions - may be appropriate. In most cases, the moderator or cooling liquid flowing past can be used for cooling the absorber rods can also be used. Finally, it should be noted that as a coolant preferably light water comes into question, but cases are also conceivable in which heavy Water or a mixture of heavy and light water with the appropriate geometric Design of the reactor core would be useful.

Claims (10)

45 claims: 1. Heterogeneous pressure vessel reactor with fuel rods arranged in a grid-like manner in its core, which is moderated and cooled with water of supercritical pressure, steam with supercritical Provides temperature and pressure values and both through rods and through an adjustable valve a cooling water supply line ending at the pressure vessel jacket is regulated, characterized in that that a second water supply line (43) provided with an adjustable valve (44) in terms of flow with a grid-like between the fuel rods and pipes (2) arranged parallel to them, which the Pass through the core and contain fixed throttle points (21) at the outflow opening. 2. Heterogeneous pressure vessel reactor according to claim 1, characterized in that the flow direction of the moderating cooling water in the tubes (2) in the direction of the cooling water flowing along the fuel rods (3) is directed in the opposite direction. 3. Heterogeneous pressure vessel reactor according to claim 1 or 2, characterized in that the Fuel rods (3) and the tubes (2) through which the moderating cooling water flows in such a way Grid arrangement over the whole space of the reactor core are distributed that geometrically seen the quotient from the total cross-section of the core space filled with water outside of the pipes (2) due to the total cross-section of the water in the pipes (2) the smallest possible Value and the quotient of the total cross-section of the water in the pipes (2) the cross-section of the entirety of the fuel rods (3) has a value greater than 1. 4. Heterogeneous pressure vessel reactor according to claim 1, characterized in that the Fuel rods (3) and tubes (2) to form fuel assembly units of known geometric shapes are summarized. 5. Heterogeneous pressure vessel reactor according to claim 1, characterized in that the control rods are arranged in spaces between fuel assemblies. 6. Heterogeneous pressure vessel reactor according to claim 1, characterized in that the Control rods are guided inside the tubes (2). 7. Heterogeneous pressure vessel reactor according to claim 1, characterized in that the control rods are arranged in grid positions of the fuel rods (3). 8. Heterogeneous pressure vessel reactor according to one of claims 1 to 7, characterized in that that on the coolant outlet side of the fuel rods (3) one extends over the entire cross section the reactor core extending mixing and collecting space is provided, from which further, Superheater channels (36) containing superheater fuel rods (35) to steam outlet openings (13) of the pressure vessel (1). 9. Heterogeneous pressure vessel reactor according to claim 1, characterized in that the circuit of the coolant mixed with a liquid absorber at the start of operation outside of the Reactor pressure vessel (1) until switching to the turbines (8) via an intercooler (6) and a separation system (72) for the absorber medium runs and that a feed valve (71) is provided for the liquid absorber. 10. Heterogeneous pressure vessel reactor according to claim 1 or 9, characterized in that the intercooler (6) arranged in a bypass line (73) of the turbine (8) for discharge the decay heat of the reactor is used. Considered publications:
French Patent No. 1138 847. For this purpose 2 sheets of drawings 809 628/1404 10.68 0 Bundesdruckerei Berlin