DE1153467B - Method and device for regulating the reactivity of a nuclear reactor - Google Patents

Description

GERMAN

PATENT OFFICE

C 18287 Vmc / 21g

REGISTRATION DATE: JANUARY 26, 1959

NOTICE
OER REGISTRATION
AND ISSUE OF THE

LAUNCHED: AUGUST 29, 1963

The invention relates to a method for regulating the reactivity of a nuclear reactor by means of relative movements between at least one control element that determines the reactivity depending on the Element impinging flux of active neutrons changes, and at least two within the reactor core formed zones with differently large flux densities of active neutrons. The invention relates to furthermore a device for carrying out the new control method.

The regulation or control of a nuclear reactor, i.e. the regular monitoring of energy generation, the change of the power level and the securing of the proper reactor operation - the is a vital task - generally done through manipulation the neutron flux in the reactor core; a certain level of performance is z. B. by hiring a achieved the neutron fiow proportional to the respective power level.

One acts on the neutron flux in the reactor core mostly by the fact that one absorbs the neutrons Draws substance deeper into or out of the core. The organs used for this purpose are generally called "control rods". The movements of such control rods make the effective one Multiplication factor of neutron generation, d. H. the "reactivity" of the reactor, changed.

When working out a design for the control devices of a nuclear reactor, numerous emerged Difficulties when you meet the imperative requirements of the actual regulation or control adapt the reactor to the further technical requirements for the design of the nuclear reactor got to. In this regard, only the following points should be pointed out: Accommodation and appropriate arrangement a larger number of control rods that have to be adapted to the operational conditions; Consideration of the space required for the control rods when they are pulled out of the reactor core are; Ensure that the protective covers are completely impervious and that they are suitably designed of bushings for the movement mechanisms of the control rods; the arrangement and accommodation of safety devices, etc.

In a nuclear reactor in which thermal neutrons are active, the reactivity is regulated of the reactor usually by means of neutrons absorbing rods whose displacement path in the the same order of magnitude as the dimensions of that area of the reactor core in which the Multiplication of the neutrons takes place. This requires the method and the device

to regulate reactivity

of a nuclear reactor

Applicant:

Commissariat a l'Energie Atomique,
Paris

Representative: Dipl.-Ing. R. Beetz, patent attorney,
Munich 22, Steinsdorfstr. 10

Claimed priority:
France of January 29, 1958 (No. 756 980)

Jacky Weill, Saint-Could, Seine-et-Oise

(France),
has been named as the inventor

in nuclear reactors that are under overpressure and are housed in a pressure-tight container, often a movement space that is available within the standing space in the pressure vessel can only be accommodated with great difficulty; Further Difficulties arise with regard to the design of the seals and radiation protection.

In order to overcome these difficulties, one already has the neutron absorbing control organs as swiveling disks, arms or "sabers" are formed, which when swiveled into the interior of the reactor core are moved in or out of it. Such regulating organs require the presence relatively extensive slots in the reactor core that increase the mechanical strength of the reactor core structure affect in an undesirable manner. To the regulating organs or their active parts To be able to remove or pivot it out of the reactor core as completely as possible is still possible requires a larger space within the reactor pressure vessel; the necessary tax movements of the regulating organs have a relatively large amplitude.

309 669/229

3 4

According to a proposal that has not been previously published, the absorbent material is used for further cleavage reactions

if the regulation of a nuclear reactor follows through at least it would be completely lost.

At least one arranged within the reactor core in a reactor in which the triggering of the

Control element whose relative movements compared to fission processes are carried out by fast neutrons, and at least two formed within the reactor core- 5 the control elements consist of nuclear fuel, both

In the case of zones with different flux densities, e.g. from uranium 235, the reactivity is changed

tive neutrons the reactor reactivity in dependence of the reactor by adding one more or less

of the river hitting the element, a large mass of "black" fissile material

active neutrons changes. as a shield from the nuclear fuel of the standard

Which brings the rule element corresponding to this older proposal.

mechanismius overlaps one another. The great advantage of the present procedure movable absorber or moderator elements, compared to the previously known control method the change in position of an adjustment of the reactivity consists in the fact that it is practically all by changing the absorption, the moderation reactor types can be applied and those for the Regeoder which allows leakage losses. For example, the required zones are of different sizes wise as regulating organs two telescoping flux density directly through the nuclear fuel of the Sorber tubes provided, which are created with cutouts ver the reactor itself, which only look like this are, which must be ordered or designed during axial displacement so that it is suitable for the ac- or twisting the tubes against each other checkerboard neutrons, d. H. the fission processes in the reactor cover like a more or less, so that the thus triggering neutrons is largely impermeable. Passage of the neutrons or their outflow to A device for carrying out the control outside is more or less hindered. The Ab method according to the invention is therefore in cover the individual absorber or moderator essential characterized in that the or surfaces can also be used by rotating the shielding elements in the reactor core pipes provided with cutouts can be achieved using nuclear fuel. The shielding element the. Thorium is used as an absorber material, or it can be subdivided into uranium to improve its cooling 238 used, so that by the captured particular leaf-shaped split. As already Neutrons in these substances, new fissile material mentioned above, can be the control element, for example can be procreated. Instead of cylindrical reactors with thermal neutrons from one Sorber elements can also be plate-like material that absorbs the active neutrons against one another movable elements are used. stand; in reactors with fast neutrons

With such a design of the control organs, the control element itself can be made of nuclear fuel,

relatively small amplitudes of movement are sufficient to achieve a through the arrangement of numerous, with small

To achieve control effect, so that shields arranged next to one another outside the Re spacing

actuator core does not require a large amount of space and is made of "black" nuclear fuel and a corresponding

the actuators in turn can also be subdivided into the regulating element

can get small dimensions. for controlling the reactor reactivity

The present invention also makes use of the order of a few centimeters for the necessary movement amplitudes to carry out the control of the reactivity, so that relative movements between at least one 40 the required small control paths with the help of control element, the reactivity depending on actuating devices with relative small size of the flow of active solutions impinging on the element, for example with deformable membranes, changes neutrons, and can control at least two within the or hydraulic cylinders. The reactor core formed zones with different constructions become simple. One can also use high flux density of active neutrons; In accordance with the invention, however, any other mechanical actuation will preferably use the zone or zones with small directions which, due to the low density of neutrons through the shielding, can easily provide a solution by means of at least one of the correspondingly arranged problems of sealing the spatial elements made of black «Permit nuclear fuel order and adequate protection,
create. 50 For a more detailed explanation of the invention are in

Under "black" nuclear fuel, according to the drawing, there are some examples from after

common usage of nuclear fuel to control devices operating in new processes

stand, which basically illustrates the cleavage processes in a very schematic form; it shows

takes part inside the reactor, but either because of FIG. 1, a first embodiment of the arrangement

its thickness or because of its density prevents 55 of the shields and the effective parts of a

that active neutrons penetrate through it. Control element in the axial longitudinal section, in which the

In a reactor in which thermal neutrons absorb neutrons compared to which the fission processes trigger, the control elements can be shifted to fixed nuclear fuel, made of an absorber material, ie made of non-fissile materials, the neutrons - preference - 60 form in which the regulation by means of a pivoting way of absorbing thermal neutrons, as is the case with cad movement of regulating elements,
mium and boron, possibly also from thorium. In this way, a swivel does not show any cleavage reactions. In the illustration of FIG. 1, fuel

According to the present method, the active 65 elements 1, 2, 3 and 4 in the form of pipes or

did the reactor changed by means of rings made of uranium at regular axial intervals

the shield made of nuclear fuel more or less over the entire height of the (not shown)

niger intercepts neutrons that are shown distributed in the "active" reactor zone when they hit

a multiplication of the neutrons takes place, whereby the distances between the individual fuel elements lie in the direction in which all of the fuel rods extend.

By a shift, the greatest path length of which is equal to the clear distance between the uranium elements 1, 2, 3 and 4, the absorbent material, also in individual, can be axially spaced Cylindrical elements 5, 6, 7 and 8 arranged from one another or in a "grape shape" are accommodated is, from a position in which its effectiveness is almost zero (in the position within the Uranium elements) can be moved to a position in which its effectiveness reaches a maximum (Intermediate position between the uranium elements).

In Fig. 2, another example is shown in which the neutron absorbing control element from cylindrical sector-shaped plates 9 and 10, the pivoted about an axis 11 lying parallel to the general arrangement of the fuel elements can be. The axis 11 coincides approximately with the axis of two semi-cylindrical fuel plates 12 and 13 together, which consist of nuclear fuel, which is completely absorbing to thermal neutrons works and is called "black" fuel.

With this arrangement, a simple pivoting of the control element by 45 ° results in a change the effective neutron absorption of the control material from a minimum to a maximum.

In the third embodiment illustrated by FIG. 3, the fuel is "black" in turn movable with respect to the neutron absorbing material. The figure shows that the Control rod consists of a fixed cylinder 14, the axis of which is parallel to the general arrangement the fuel elements of the nuclear reactor lies. The nuclear fuel is each in four cylinder segments 15, 16, 17 and 18, of which the first two are fixed and the latter two are movable or are pivotably mounted about the axis of the entire arrangement. In this way it has a pivoting movement the segments 17 and 18 from the position shown in Fig. 3 has the effect that the absorbent Material is gradually exposed to a certain degree and its neutron absorption increases from a minimum where it is almost zero to a maximum.

The present invention can also be used for regulating or controlling on the action of snow Neutron based nuclear reactors are used when the neutron absorbing elements of the examples explained above can be replaced by elements made of nuclear fuel, depending on their respective Able to be more or less involved in the cleavage reactions.

Finally, the problem of cooling the elements consisting of "black" nuclear fuel, can be solved in a very simple manner by splitting or subdividing these elements in order to to improve their heat exchange with the cooling medium of the nuclear reactor.

Claims (11)

PATENT CLAIMS: 1. A method for regulating the reactivity of a nuclear reactor by relative movements between at least one regulating element, which changes the reactivity depending on the flow of active neutrons hitting the element, and at least two zones formed within the reactor core with different flux densities of active neutrons, marked thereby that the zone or zones with a smaller neutron flux through the shield via at least one correspondingly positioned element are created from black nuclear fuel .. 2. Device for performing the method according to claim 1, characterized in that that the shielding element consists of nuclear fuel used in the reactor core. 3. Apparatus according to claim 2, characterized in that the shielding element for improvement its cooling is divided. 4. Apparatus according to claim 3, characterized in that the shielding element is sheet-shaped is split. 5. Device according to one or more of claims 2 to 4, characterized in that the control element consists of a material which absorbs the active neutrons. 6. Device according to one or more of claims 2 to 4, characterized in that the control element consists of nuclear fuel. 7. Device according to one or more of claims 2 to 6, characterized in that the devices for relative movement between control element and shielding element for small Relative movements are designed. 8. Device according to one or more of claims 2 to 7, characterized in that the control element from coaxially arranged, each with certain axial distances from one another arranged cylinders consists that the shielding element consists of a number of equiaxed, arranged coaxially with the cylinders and at the same axial intervals as these from one another Pipe sections consists, and that the cylinder in the axial direction within the pipe sections are movable relative to these. 9. Device according to one or more of claims 2 to 7, characterized in that the shielding element consists of two cylindrically curved plates, the concave sides of which facing each other and their associated cylinder axes are parallel to each other, and that each of the two opposing edges of the plates longitudinally directed through openings limit for plate-shaped, curved parts of the control element. 10. The device according to claim 9, characterized in that that the control element consists of two plates which sit on two swivel arms, which in turn around a parallel to the Axes of the shielding plates are pivotable axis. 11. The device according to one or more of claims 2 to 7, characterized in that the control element is a fixed cylinder, while the shielding element consists of two each other opposite cylindrical solid curved with respect to the common axis Plates and two more, also opposite each other and in relation to the common one Axis curved, but pivotable about this axis plates, which consist of a 7 8 mentation, in which she explains the space between the “Proceedings of the International Conference on Shielding the edges of the solid plates, in a "The Peaceful Uses of Atomic Energy", Vol. 2, 1956, further position are movable in which they these p. 467 and 468; Release gaps. "The Engineer", Vol. 200, 1955, pp. 190 and 191. Documents considered: ¹ ^ Older patents considered: Austrian Patent No. 166 668; German Patent No. 1049 014. 1 sheet of drawings © 309 669/229 8.63