JPS62254098A - Control rod for nuclear reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Object 1-1 of the invention] (Industrial application field) Tree, invention (Y13; Nuclear reactor a, +1 i# that controls the reactor output of the I slave reactor in 'A section) Regarding rods, 1. "1" relates to control rods for boiling water type uni 7' of long type I life type.

(Prior Art) A υ control rod for a boiling water nuclear reactor is constructed by loading a large number of neutron absorption rods into a plurality of wings formed by attaching an elongated TJ-shaped sheath to a central tie rod. The neutron absorption rod is constructed by filling a S tJ S cladding tube with boron carbide (84C) powder and arranging partitions at regular intervals within the cladding tube to prevent powder movement.

84C filled in the neutron absorption rod absorbs neutrons and C
While the neutron absorption capacity is gradually lost, during that time boron-10<"B) interacts with neutrons and settles the t1e gas, causing the pressure inside the cladding to increase by 1. The life determined by the neutral f absorption capacity The life span determined by the gas pressure inside the cladding tube is called the mechanical life.

By the way, none of the aI rods that are taken in and out of the reactor core are uniformly irradiated with neutrons; for example, the side edges and upper ends of each wing are exposed to strong neutron irradiation. For this reason, the neutron absorbing rods near the side edges of each wing of the control rod and the ends absorb a large amount of neutrons, and therefore reach their nuclear lifetime earlier than the neutron absorbing rods in other parts. As a result, the control rod had to be disposed of as radioactive waste, even though the other neutron absorption rods had a sufficient paper lifespan.

In order to solve such problems, the present applicant has developed a control rod for a nuclear reactor in which a long-life neutron absorber with a long nuclear life is placed near the side edge of the wing, which is exposed to strong neutron irradiation. This reactor trill rod is published in Japanese Patent Application Publication No. 53-74697.
@Disclosed in the official bulletin.

However, the reactor control rods disclosed in Japanese Patent Application Laid-open No. 53-74697 have a lifespan that is only twice as long as the normal type υJI [I rods, and are not necessarily satisfactory in terms of extending the lifespan of control rods. It was not something I could enjoy.

In order to address this problem of longer life, the present applicant has developed a significantly superior Nagano Life type nuclear reactor control rod. As disclosed in Japanese Patent Application Laid-Open No. 58-55887, this control rod for a nuclear reactor has a solid neutron 1 absorption plate made of a long-life neutron absorbing material in each wing of the control rod.
It's something new. In this neutron absorption plate, the II and distribution number of through holes or recesses are adjusted so that the axial distribution of the reactor shutdown margin is reduced by removing the board material in the booth, and conversely, in the region where the axial distribution of the reactor shutdown margin becomes large, a large amount of board material is removed. It has established.

(Problems that the invention has solved) However, in this #i-furnace υJail rod, the neutron absorbing material is a plate-like hafnium (Hf) metal plate. Since weight 1 is very large,
1/ which handles this &11111 bar along with the 4 value
The design of the 1-jin-pai starting mechanism needed to be changed to make it more durable, and the conventional 2. IJ Illll dynamic drive 111M could not be used as is.

On the other hand, long life is used for υ control rods for nuclear reactors! v! The weight of the hafnium metal plate, which is a neutron absorbing material, has been removed.
1! Subsequent studies confirmed that if the control rod for the reactor could be reduced by 1,111 rill by removing the excess material, the υ control rod drive mechanism could be used as is without any changes to the design.

The present invention has been made with the above-mentioned considerations in mind, and therefore it has been decided that the long-life neutron absorber will be effectively constructed.
υlta [l The purpose is to provide a luri drive rod for a life-type Ushi reactor that can be used without changing the lateral setting of the rod drive Ia.

(Structure of the Invention) (Means for Solving Problems sj, -) A control rod for a nuclear reactor according to the present invention connects a tip structural member and an end structural member by a central tie [], and A sheath is fixed to each protrusion, and a root-shaped long-life neutron absorber is inserted into the second sheath, and the neutron absorber is divided into a plurality of neutron absorbing elements in the axial direction of the central tie rod. In addition, a gap is formed between the neutron absorber 1 and the neutron 1 collecting elements facing each other in the thickness direction of the wing to guide the moderator.

(Function) The flilJ control rod for a nuclear reactor according to the present invention has a long-life neutron absorber disposed along the axial direction of the central tie 1 which connects the tip structure member and the end structure member, and the neutron absorber The absorbent body is housed within the sheath. The neutron absorber is divided into a plurality of neutron absorbing elements in the axial direction of the central tie rod in order to disperse the weight and absorb differences in elongation due to thermal expansion 1 and 6. A gap for guiding the moderator is formed between the neutron absorption elements facing each other in the thickness direction of the wing, and this gap is used as a moderator flow path to increase the reactivity. Φm is reduced.

(Example) Hereinafter, an example of a control rod for a nuclear reactor according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is an overall perspective view schematically showing a nuclear reactor ff and a control rod according to the present invention. and are integrally connected by a central tie rod 14 having a 11-shaped cross section. Each protruding leg of the central tie []Turado 4 has a deep U-shaped cross section with a high N! A sheath 15 made of stainless steel is fixed to form a wing 16. Inside the sheath 15, a root-like member typified by an octium (Hf) metal plate or the like is installed. 18 is inserted.

The neutron absorber 18 is divided into a plurality of neutron absorbing elements 18a to 18h by metal neutron absorbing plates in the direction of the axis 1 of the central tie rod 14, for example, eight neutron absorbing elements 18a to 18h as shown in FIG. Each stage of neutron absorption elements 188 to 18h is supported by a plurality of support spacers 20, respectively. As shown in FIG. 2, the support spacers 20 are fixed to the wing 16 at appropriate intervals to prevent vertical movement of the neutron absorbing M elements 18a to 18h.

Each stage of neutron absorption elements 18a to 18h is provided with a tip structure material 12.
The neutron absorption characteristics are configured such that the neutron absorption characteristics gradually decrease from 1 to 13 toward the terminal structural member 13. Specifically, when the neutron absorber 18 is divided into 8 stages of neutron absorption elements 18a to 18h, the neutron absorption characteristics of each stage are The neutron absorbers A 18a to 18h are thinned in stages from the tip structure material 12 to the end structure material 13, and this thinning causes a reactivity effect, that is, a neutron absorption effect, as shown in FIG. The absorption properties are gradually reduced.

In addition, in FIG. 3(A), an example was explained in which the neutron absorbing elements 188 to 18h of all stages were thinned stepwise in the axial direction, but as shown in FIG. A plurality of neutron absorbing elements, for example two of the same plate thickness, may be used, and as shown in FIG. The neutron absorbing elements shown in FIGS. 3(A) to 3(C) may be combined with each other.

In addition, the tip side of the first stage neutron absorbing element 18a that is 1" adjacent to the tip structural member 12 (the area within α, for example, 3 rods from the tip) is The neutron absorption characteristics may be increased to improve the scram characteristics, or the neutron absorption characteristics may be decreased to reduce the fluctuation range of the reactor output due to control rod withdrawal.
The first-stage neutron absorbing element 18a can also be formed in such a manner that the neutron absorbing property on the side end portion facing the central tie rod 14 side is increased.

By the way, long life jli′! 10 minutes for reactor control rods.

The end structural members 12, central tie rods 14, sheaths 1; 5, etc. are exposed to a very large amount of neutron irradiation, and there is a possibility that they may become brittle due to this neutron irradiation, so high eIi polished)'' stainless steel is used. This alleviates the problem of embrittlement caused by mechanical strength.In addition, the tip structural material 12, the terminal structural material 13, and the speed limiter 22 attached to this terminal structural material 13 are , the weight is reduced.

Moreover, the neutron absorber 18 inserted into the sheath 15 is
As shown in FIG. 4, 5J is made of two plate-shaped neutron absorbing elements 18a to 18a, 18b made of sea urchin hanonium metal plates.
, 18b-=18h, and 18h are installed facing each other in the thickness direction of the wing 16. bineutral T-absorbing element 18a,
18al, the spacing is maintained by support spacers 201
, the support sweeper 20 has a frame-like structure as shown in FIG. It is loosely d and fixed to the inner wall of the sheath 15 by welding or the like. The holes 2:3 formed in the neutron absorbing element 18a are formed to have a larger diameter than the supporting legs 20b, and are designed to absorb and eliminate wire drawing due to lagoon change. The neutron absorbing element 18a is supported by the sheath 1b by this support base 4120, and the neutron absorbing element 18a
, A flat gap 25 is formed in 18a to guide the moderator, and this gap 25 is formed as a moderator flow path.

As shown in FIG. 6, a plurality of water passage holes 26 that communicate with the gap 25 are formed in the sheath 15 at positions corresponding to the neutron absorbing elements 18a. The water hole 26 above is +1
1J will prevent the wing 16 from passing 41 times in a straight line.

The plate-shaped neutron absorbing elements 188 to 18h in each stage are, for example, 0.5M to 2.0M. Figure 3 (
Δ) - 1.5M to 2 on the tip structure material 12 side
．． 0M, 0°5g+-1,0s+ on the terminal structural material 13 side
The thickness of the plate is set at the intermediate portion as appropriate.

Next, the action of the 1II1 ill rod for nuclear reactors will be explained.

In a boiling water reactor, the axial fission nuclide concentration distribution curve of the reactor core after combustion has progressed to a certain extent is typically expressed as shown in FIG. Since the combustion control of the reactor core is divided into four equal parts in the @h direction of the reactor core, it is convenient to divide the reactor control rod 10 into four equal parts.

At one end of the reactor core, the progress of combustion is delayed during combustion, so the fission nuclear + IS concentration value is large.
From the top to the top, the neutron spectrum hardens due to the generation of voids. The beams promote the plu-1-nium production reaction (neutron absorption reaction), and the thermal neutron flux decreases due to the generated voids, and this decrease causes combustion H. As a result, the fission nuclide concentration distribution is Represented as shown in the figure.

When the nuclear fission nuclide temperature shown in FIG. 7 exists in the core of the nuclear reactor, the neutron multiplication factor at the time of reactor shutdown takes the form of distribution curve B, which is large in the upper part in the axial direction, as shown in FIG. 8. The larger the value of the neutron multiplication factor, the smaller the reactor shutdown margin and the shallower the subcriticality. In addition, the 8th
The figure shows that the neutron multiplication factor decreases at the lower and upper ends of the reactor core, a phenomenon caused by neutron leakage.

FIG. 9 is a neutron irradiation distribution curve C in the @h direction of the nuclear reactor control rod 10 when the nuclear reactor υ1111 rod 10 according to the present invention is used. From this 9711 curve C,
The 1i11 ffO rod 10 for a nuclear reactor has a very limited r1 castle (normally 30t from the tip: xi culm degree) at the upper end, and there is a part where the middle t'1 child irradiation suspension suddenly becomes 10H. The other portions decrease continuously and smoothly toward the lower end of the nuclear reactor a, lj gift 10.

The U-control rod 10 for a nuclear reactor according to the present invention has a satisfactory neutron multiplication factor characteristic shown in FIG. 8 and a neutron irradiation vvI characteristic shown in FIG. The control effect is (ii).
41-, for example, the neutron multiplication factor rises (if tj', the stopping margin becomes small) and the neutral irradiation product becomes low, resulting in a low stopping margin. Dealing with easy things.

Further, as shown in FIGS. 3(A) to 3(C), the neutron absorbing element becomes thicker at λ9 from the tip structural member 12 toward the distal structural member 13, and the neutron absorbing effect gradually increases to 11. J going down the street, sea urchins are turning. In particular, the neutron absorption characteristics in the 1/4 L region from the lower end of the reactor control rod 10 (the upper end of the notice material 13) are slightly smaller than those between 1/41 and 2/41-mag. ing. This means that in terms of neutron irradiation, as shown in Figure 9, the lower region from the bottom to 1/4L is the adjacent 16th order region (1/41.- to 2/41.,
), the neutron multiplication factor is 8th.
This is because it is relatively thick as shown in the figure.

In addition, FIG. 10 shows each wing 16 of the reactor control rod 10.
This shows the typical neutron radiation QJffi distribution curve in the width direction of ing. From this, the neutron absorber 18 can improve the reactivity by changing the neutral T absorption characteristics in the width direction of the wing 16. ! !
r: can be set as shown in FIG.

At that time, in the nuclear reactor control rod 10 of the present invention, each neutron absorbing element 188 to 18 of the bamboo absorber 18 is intended to have a root-like long rod.
h is formed by a thin plate, and Q flat In is formed between the neutron absorption elements.
Since the gap 2b is formed and the lff1 gap 25 is used as a moderator flow path, the number of individual neutron absorbers 18 housed in the wings 16 can be significantly reduced compared to conventional neutron absorbers that do not form gaps. Can be done. Therefore, i11 of the entire reactor control rod 10! Can reduce hanging,
The existing control rod drive mechanism can be used as is without any modification.

Next, other embodiments of the υj rod for nuclear reactors will be described.

12 to 15 show various modifications of the wing used in the control rod for a nuclear reactor according to the present invention.

The reactor control rod 10Δ shown in FIG.
An example is shown in which it is divided into two parts in the radial direction (radial direction) into inner and outer parts. Each stage neutron absorption element 18Aa, 18△a: 18△b518
Δb is arranged to face the wing 16 in the thickening direction, and a gap 25 for guiding the moderator is formed between them. So, the outer middle 1'l child absorption element 18
Since Ab is η whitened, the width changes stepwise in the width direction of the wing 16.

Reactor control rod 108μ wing 1 shown in Figure 13
An example is shown in which each neutron absorbing element 18Ba of the neutron absorber 18B is continuously thinned from the side end of the neutron absorber 18B toward the central tie rod 14.
Neutron absorption of the neutron absorbers 18G accommodated in each wing 16 Engagement stepped portion 28
and this engagement stage n128 is connected to the inner neutron absorbing element 1
Try to match it to 8Ca, -6 is good. At that time, engagement stages PJI may be formed on the joint surfaces of the inner and outer neutron absorbing elements, respectively. By fitting the inner and outer neutron absorbing elements 18Ca and 18Cb in phase N, it is possible to prevent neutrons from leaking from this overlapping portion.

FIG. 15 shows three neutron absorbing elements 18Da, 18Db, and 18De as neutron absorbers 18D placed at intervals in the thickness direction of the wing 16 in each mounting 16 of the reactor aill W rod 10 (). each neutron absorbing element 18
Da, 18Db, and 18Dc are maintained at intervals by a support suberly 200.

FIG. 16 shows still another modification of the nuclear reactor control rod according to the present invention.

Nuclear reactor υ control rod 10hi (71,
Neutron absorbing elements 18Ea, 18Eb, 18 of each adjacent stage of the neutron absorber 18F housed in each wing 16
[Ec... are arranged so that they overlap η. For example, the engagement stage as 29 overlaps the neutron absorption element 1.8 E a of the upper stage Id on the tip structure member 12 side and the neutron absorption element 18Eb of the next stage.

30 and the second stage neutron absorbing element 18
Eb and the third stage neutron absorption element 18 [C means wall thickness I+
'4, for example, the engagement step 31 is provided only on one side.
is formed. In addition, the shape of the engaging stepped portion can be varied in various ways.

In addition, FIG. 17 J3 and FIG. 18 are polygons with an auxiliary handle and a control 10F for the IJ reactor.

In explaining this il, ll 1211 cup 101,
1 control rod 10 for a nuclear reactor shown in FIGS. 1 and 2
The same part + A is given a button, the same part - and the explanation is omitted M. In this original r-furnace a, II fit cup 10F, a gap 3ζ3 is formed at the lower part of the front pane member 12, and this gap 33
is configured as an auxiliary handle. The auxiliary handle 33 is the part that requires the most neutron absorbing material due to the neutron absorption performance of the neutron absorber 181, and the gap 33 of the auxiliary handle further reduces the neutron absorption performance of the reactor rod 10 by +7. be done.

-lj, it has been experimentally determined that the high-speed neutron irradiation m of the upper part of the auxiliary handle is 1/3 to 1/5 culm degree or less than the high-speed neutron irradiation height of the handle 11L portion. From this, the embrittlement due to neutron irradiation of the auxiliary handle part 33 is 1/3 to 115 times the embrittlement of the handle part, so if the auxiliary handle part 33 is provided, This is a very healthy handle backup function.

Although various modifications have been described for the fill I'll rod for a nuclear reactor according to the present invention, various modifications can be made without departing from the spirit of the invention.

(Effects of the Invention) As described above, in the control rod for a one-quantum reactor according to the present invention, the neutron absorber is divided into a plurality of neutron absorbing elements at least in the axial direction of the central rod and the rod, and
Since the gap for guiding the moderator is formed between the neutron absorbing elements facing each other in the thickness direction of the wing, the weight of the V1 absorber can be reduced by at least the amount of this gap. Therefore, it is possible to reliably and effectively reduce the weight of nuclear reactor control rods, and without having to change the design of the existing υJ gosho drive I
You can do it.

By guiding the moderator into the gap in the neutron absorber, the neutron absorber is moved in the direction 1. :The number of neutrons collected can be reduced accordingly. Roughly,
Since the neutron absorbing element of the neutron absorber can be effectively placed at a position where the shutdown margin is small, the reactivity is effectively increased by 1, and the shutdown margin of the reactor is improved.

[Brief explanation of drawings]

Figure 1 shows an embodiment of a control rod for a nuclear reactor according to the present invention.
An overall perspective view, Figure 2 is a diagram showing the arrangement of the neutron absorbers incorporated in the reactor control rod, and Figures 3 (△) to (
C) shows the relationship between the height direction of the reactor control rod and the reaction 1u effect (neutron absorption characteristics), and Figure 4 is the IV of Figure 2.
- A partial plan cross-sectional view taken along line IV; FIG.
Figure 14 is a plan cross-sectional view along the Vl-Vl line in Figure 1, and Figure 7 shows the distribution of fission nuclides in the axial direction of the reactor core.
8 shows the neutron multiplication factor distribution in J3 in the axial direction of the reactor core, and FIG. 9 shows the neutron irradiation 61 distribution in the axial direction of the control rod for a nuclear reactor according to the present invention. 10
The figure shows the neutron irradiation distribution in the wing width direction of the 1j JIIll rod for the above reactor, and Figure 11 shows the neutron irradiation distribution for the above reactor υj
Control rod wing width direction reaction! , Figure 1 shows the effect of
2 to 15 are plan sectional views showing modified examples of each wing used in the V control rod for a nuclear reactor according to the present invention, and FIG. Partial longitudinal section showing a modified example, 1st
FIG. 7 and FIG. 18 are views showing a nuclear reactor control shaft according to the present invention, which is equipped with an auxiliary handle. 10, IOA, IOB, IOC, 10D, 10E, 10
F...Reactor control rod, 12...Tip 1 pickling material, 13
...End @ construction material, 14...Central tie rod, 15.
...Sheath, 16...Wing, 1B, to '18. 18F3.18C, 18D, 18E, 18F...neutron absorber, 18 a, ~18 h, 18 A
a, 18△b, 18Ba, 18Ca, 18Cb, 1
81. ) a. 181)b, 18Dc, 18Ea, 18Eb, 18Ec
, 18 a ~ 18 F d-... neutron absorption element, 2
0.201)--Support slippage, 25...Gap, 2
6...Water hole, 33...Auxiliary handle part. Outgoing person agent Ha Ta Def Long time l
Mushi i, y,
2. To 2] Hand 7 Figure 6 Figure 9 Figure $IO Figure Sheep lf Figure 73 Figure 15 Figure 16 Fan $ 17 Figure f6 Figure

Claims (1)

[Claims] 1. The tip structural member and the terminal structural member are connected by a central tie rod, a sheath is fixed to each protrusion of the central tie rod, and a plate-shaped long-life neutron absorber is provided within the sheath. In the control rod for a nuclear reactor, the neutron absorber is divided into a plurality of neutron absorbing elements at least in the axial direction of the central tie rod, and the neutron absorber is divided into a plurality of neutron absorbing elements facing each other in the thickness direction of the wing. A control rod for a nuclear reactor, characterized in that a gap for guiding a moderator is formed between the rods. 2. The control rod for a nuclear reactor according to claim 1, wherein the neutron absorption element is configured such that its neutron absorption characteristics gradually decrease from the tip structural member to the terminal structural member. 3. The control rod for a nuclear reactor according to claim 1 or 2, wherein the neutron absorption element is gradually thinned from the tip structural member to the terminal structural member. 4. The control rod for a nuclear reactor according to claim 1 or 2, wherein the neutron absorption element has a greater neutron absorption characteristic at the outer end of the wing than at other parts. 5. The control rod for a nuclear reactor according to claim 1, wherein support spacers are disposed within the sheath at intervals in the axial direction, and each support spacer engages and supports a neutron absorption element. 6. The control rod for a nuclear reactor according to claim 1, wherein the neutron absorbing element adjacent to the tip structure member is provided with an auxiliary handle adjacent to the neutron tie rod. 7. The control rod for a nuclear reactor according to claim 1, wherein the sheath and the neutron absorption element within the sheath are provided with water holes communicating with the moderator guide gap at corresponding locations. 8. The neutron absorbing element is composed of a plurality of metal neutron absorbing plates such as hafnium metal plates that are housed oppositely in the thickness direction of the inner wing of the sheath, and the opposing metal neutron absorbing plates are maintained at a distance by a support spacer. The control rod for a nuclear reactor according to claim 1, wherein a moderator flow path gap is formed between the metal neutron absorption plates. 9. The control rod for a nuclear reactor according to claim 1, wherein the neutron absorption element has a portion that overlaps with an adjacent neutron absorption element.