JPH0636050B2 - Nuclear fuel rod - Google Patents

Description

TECHNICAL FIELD The present invention relates to a nuclear fuel rod, and more particularly to a nuclear fuel rod that can be accurately inserted into a predetermined nuclear fuel rod insertion hole of a graphite block.

[Prior Art and Problems to be Solved by the Invention] Currently, in a pin-in block type HTGR fuel assembly, a predetermined nuclear fuel rod is provided in a hexagonal graphite block according to the enrichment of the nuclear fuel. A nuclear fuel rod with a predetermined enrichment must be inserted into the insertion hole.

Therefore, it is necessary to take special measures to prevent nuclear fuel other than the nuclear fuel rods defined in the predetermined nuclear fuel rod insertion holes from being misloaded.

That is, the width and length of the rib for preventing rotation provided at the rear end of the nuclear fuel rod (the rear end in the insertion direction) and the rib provided in the nuclear fuel rod insertion hole into which the nuclear fuel rod must be inserted. The dimensions of the rib and the groove are designed so that the width and the length of the groove are matched with each other, and the design is made different according to the enrichment of the fuel rod, thereby inserting a specific nuclear fuel rod. This prevents misloading of nuclear fuel rods by inserting other nuclear fuel rods of enrichment not corresponding to the enrichment into the holes.

For example, a nuclear fuel rod for high enrichment has a wider width and a shorter length of ribs for preventing rotation, and a nuclear fuel rod for lower enrichment has a narrower width for ribs of anti-rotation and has a longer length. The ribs are dimensioned in stages so that the length becomes longer, and the nuclear fuel rod insertion holes corresponding to the ribs are formed so that the groove has a width and a length corresponding to the dimensions of the rib for enrichment. By designing the size of the groove, the nuclear fuel rod of a specific enrichment is mechanically controlled so that it is inserted only into the corresponding nuclear fuel rod insertion hole.

If a nuclear fuel rod is mistakenly inserted in a different position in the nuclear fuel rod insertion hole, the nuclear fuel rod will not enter the correct position in the nuclear fuel rod insertion hole, and a part of the rear end of the fuel rod will be inserted. The misloading can be found by appearance, as it either projects from the hole entrance or the rear end of the nuclear fuel rod cannot be inserted at all.

However, as the enrichment increases, the number of combinations of nuclear fuel rods and corresponding nuclear fuel rod insertion holes also increases. There is a limit to changing the width and length of the rib, and there is a problem in that the number of combinations cannot be adequately dealt with.

In addition, if the number of combinations of nuclear fuel rods and the corresponding nuclear fuel rod insertion holes increases due to various enrichment levels, the width and length of the ribs for rotation prevention will be within the current dimension range of ribs for preventing misloading. There is a problem that it may be difficult to manufacture a nuclear fuel rod having a different temperature.

An object of the present invention is to easily and accurately insert a nuclear fuel rod without misloading it into a predetermined nuclear fuel rod insertion hole provided in a graphite block even when the concentration of nuclear fuel varies. It is to provide a nuclear fuel rod that can be manufactured.

[Means and Actions for Solving the Problems] The present invention for solving the above problems is of the type (n × m) in which a graphite block is loaded and a misload preventing rib and a spacer are provided on the side surface thereof. Nuclear fuel rods (where n and m are arbitrary natural numbers). ], The width of the misload preventing rib is W _k and the length thereof is L
_{n-k + 1} [where k is an integer from _{1 to} n, W ₁ <W ₂ <... W _n-1 <W _n , and L ₁ <L ₂ <... to satisfy the relationship of _{··· L n-1 <L n} . ], The length in the insertion direction is X _j on the outer peripheral surface side at the tip of the insertion method [where j is an integer of _{1 to} m, and X ₁ <X ₂ <... X Satisfies the relationship of _m-1 <X _m ,
X ₁ may be 0. ] The length from the tip of the spacer in the insertion direction to the tip of the nuclear fuel rod in the insertion direction is Y _{m + 1-j} , where j and m have the same meanings as described above. , Y ₁ <Y ₂ <・ ・ ・ ・ ・ ・ Y _m-1 <
The relationship Y _m may be satisfied, and Y ₁ may be 0. ], A plurality of nuclear fuel rod insertion holes provided in the graphite block can be inserted into a specific nuclear fuel rod insertion hole having a groove corresponding to the misload preventing rib and a protrusion supporting the spacer. It is a nuclear fuel rod characterized in that

[Operation] According to the above configuration, when the nuclear fuel rods are properly loaded into the predetermined nuclear fuel rod insertion holes provided in the graphite block, for example, as shown in FIG. Direction) each dimension of the misloading prevention rib 2 provided at the rear end (width of the misloading prevention rib 2, length of the misloading prevention rib 2, and notch of the misloading prevention rib 2) Of the spacer 3 in the nuclear fuel rod 1 corresponds to the respective dimensions of the groove of the nuclear fuel rod insertion hole.
From the lower end to the lower end of the nuclear fuel rod corresponding to the position of the protruding portion 4a supporting the spacer 3 in the nuclear fuel rod insertion hole, with the nuclear fuel rod 1 loaded in the nuclear fuel rod insertion hole of the graphite block 4. However, the rear end portion of the nuclear fuel rod 1 does not project from the flat end surface of the graphite block 4, and the nuclear fuel rod 1 is correctly loaded on the graphite block 4.

On the other hand, when a nuclear fuel rod is erroneously loaded into a predetermined nuclear fuel rod insertion hole provided in the graphite block, the state in which the nuclear fuel rod is loaded in the nuclear fuel rod insertion hole of the graphite block is as follows.
~ The state corresponds to at least one of the states d.

Here, the width of the misloading prevention rib in the predetermined nuclear fuel rod to be loaded is W, the length of the misloading prevention rib in the predetermined nuclear fuel rod to be loaded is L, and the width of the predetermined nuclear fuel rod to be loaded is Let X be the length in the insertion direction of the notch of the rib for preventing misloading, and Y be the length from the tip in the insertion direction of the spacer to the tip in the insertion direction of the nuclear fuel rod in the prescribed nuclear fuel rod to be loaded.

-State a- The width of the misload preventing rib in the misloaded nuclear fuel rod is W.
The length is smaller and the length of the misload preventing rib in the misloaded nuclear fuel rod is larger than L. Therefore, for example, as shown in FIG. 4, the misload preventing rib 2 cannot completely enter the groove in the nuclear fuel rod insertion hole, and the rear end portion of the nuclear fuel rod 1 protrudes from the flat end surface of the graphite block 4. It becomes a state.

-State b- The width of the misload preventing rib in the misloaded nuclear fuel rod is W.
The length of the misload preventing rib in the misloaded nuclear fuel rod is smaller than L. Therefore, for example, as shown in FIG. 5, the misload preventing rib 2 cannot enter the groove in the nuclear fuel rod insertion hole at all, and the rear end portion (misload preventing rib 2) of the nuclear fuel rod 1 is entirely made of graphite. The block 4 is projected from the flat end surface.

-State c- From the tip of the misloaded nuclear fuel rod in the insertion direction of the spacer to the tip of the misloaded nuclear fuel rod in the insertion direction of the misloaded nuclear fuel rod in which the length in the insertion direction of the notch is smaller than X. Is greater than Y. Therefore, for example, as shown in FIG. 6, the rear end of the notch of the misload preventing rib 2 comes into contact with the protrusion 4b corresponding to the notch in the groove of the nuclear fuel rod insertion hole, and the nuclear fuel rod 1 is completely removed. Can not enter, the rear end of nuclear fuel rod 1 is graphite block 4
It is in a state of protruding from the flat end surface of.

-State d- From the tip of the misloaded nuclear fuel rod in the insertion direction of the spacer to the tip of the misloaded nuclear fuel rod in the insertion direction of the misloaded nuclear fuel rod in which the length in the insertion direction of the notch is greater than X. Is smaller than Y. Therefore, for example, as shown in FIG. 7, when the tip of the spacer 3 hits the protrusion 4a supporting the spacer 3 in the nuclear fuel rod insertion hole, the nuclear fuel rod 1 cannot completely enter,
The rear end of the nuclear fuel rod 1 is projected from the flat end surface of the graphite block 4.

[Examples] The present invention will be described in more detail below by showing Examples of the present invention.

1 and 2 are explanatory views showing an example of the structure of the nuclear fuel rod of the present invention.

The nuclear fuel rod of the present invention is provided with a misload preventing rib 2 and a spacer 3 as shown in FIGS. 1 and 2, for example.

The misload preventing rib 2 usually has a function as a rotation preventing rib, and is provided on the outer peripheral surface at the rear end portion in the insertion direction of the nuclear fuel rod 1 having a substantially circular cross section, and is attached to the graphite block 4. When inserted into a predetermined nuclear fuel rod insertion hole provided, it is fitted into the groove of the nuclear fuel rod insertion hole.

Further, the misloading prevention rib 2 has a notch on the outer peripheral surface side at the tip end portion in the insertion direction of the misloading prevention rib 2.

The spacer 3 is provided on the outer peripheral surface of the nuclear fuel rod 1, and when inserted into a predetermined nuclear fuel rod insertion section provided in the graphite block 4, the spacer 3 is supported by the protrusion 4 a of the nuclear fuel rod insertion hole that supports the spacer 3. Be accepted and accepted.

In the nuclear fuel rod of the present invention, the width W of the misloading prevention rib 2, the length L of the misloading prevention rib 2 and the insertion direction of the notch of the misloading prevention rib 2 are determined according to the enrichment of the nuclear fuel. Four types of parameters, which are the length X and the length Y from the tip of the spacer 3 in the insertion direction to the tip of the nuclear fuel rod in the insertion direction, are changed.

The changes in the four parameters are defined as follows.

In the predetermined nuclear fuel rod of the present invention, the width W of the misload preventing rib 2 is W _k, and the length L of the misload preventing rib 2 is L.
_{n-k + 1} , the length X of the notch portion of the misload preventing rib 2 in the insertion direction is X _j, and the length Y from the tip of the spacer 3 in the insertion direction to the tip of the nuclear fuel rod in the insertion direction is Y. _{Let m + 1-j} .

The width W _k of the misload preventing rib 2 and the length L _{n-k + 1 of the} misload preventing rib 2 are integers of ₁ to n, where n is an arbitrary natural number, and W ₁ < The relations W ₂ <... W _n-1 <W _n and L ₁ <L ₂ <... L _n-1 <L _n are satisfied.

The length X _j of the notch portion of the misload preventing rib 2 in the insertion direction and the length Y _{m + 1-j} from the tip of the spacer 3 in the insertion direction to the tip of the nuclear fuel rod in the insertion direction are j 1 to j. is an integer of m,
m is an arbitrary natural number, and the relations of X ₁ <X ₂ <... X _m-1 <X _m , and Y ₁ <Y ₂ <... Y _m-1 <Y _m To be satisfied. Note that X ₁ may be 0 and Y ₁ may be 0. When X ₁ is 0, the misloading preventing rib 2 having a length of X ₁ in the insertion direction of the cutout portion does not substantially have the cutout portion.

Such a nuclear fuel rod is inserted into a specific nuclear fuel rod insertion hole having a plurality of nuclear fuel rod insertion holes formed in the graphite block, the groove corresponding to the rib for preventing misloading, and the protrusion supporting the spacer. It

When inserting the nuclear fuel rod into the nuclear fuel rod insertion hole, there may be a tolerance between the nuclear fuel rod and the nuclear fuel rod insertion hole for allowing the nuclear fuel rod to be smoothly inserted into the nuclear fuel rod insertion hole. .

In case of having the above-mentioned tolerance, the value of (W _p −W _p−1 ), (L _p
-L _p-1 ) value, (X _q -X _q-1 ) value, and (Y _q
The value of -Y _q-1 ) is usually set larger than the value of its tolerance. However, p is an integer of 2 to n and q is an integer of 2 to m.

There are n types of nuclear fuel rods having different widths and lengths of the misload prevention ribs, and the length of the misload prevention rib in the insertion direction of the notch and the insertion of the nuclear fuel rod from the tip in the insertion direction of the spacer. There are m types of nuclear fuel rods having different lengths in the direction.

Therefore, (width and length of rib for preventing misloading) and / or (length in the insertion direction of the notch of the rib for preventing misloading), and the tip in the insertion direction of the nuclear fuel rod from the tip in the insertion direction of the spacer. The number of nuclear fuel rods with different lengths is (n × m).

In this embodiment, the width W of the misload preventing rib 2 and the length L of the misload preventing rib 2 are determined according to the enrichment of the nuclear fuel.
By changing four types of parameters, a length X in the insertion direction of the notch of the misload preventing rib 2 and a length Y from the tip of the spacer 3 in the insertion direction to the tip of the nuclear fuel rod in the insertion direction are changed, The four types of parameters are associated with the nuclear fuel enrichment.

The corresponding combinations are shown in Table 1.

In the combinations shown in Table 1, for example, enrichment C _{1 · 2}
The nuclear fuel rods to be used, when erroneous loading nuclear fuel insertion hole of the graphite blocks for inserting the nuclear fuel rods for use in the enrichment C _{2 · 2,} the length of the erroneous loading prevention ribs in nuclear fuel rods for use in the enrichment C _{2 · 2} than is (L _n-1), the length of the erroneous loading prevention ribs in nuclear fuel rods for use in the enrichment C _{1 · 2} (L _n) is large, loaded nuclear fuel rod insertion holes of the graphite blocks erroneously nuclear fuel rods In this state, for example, as shown in FIG. 4, the misload preventing rib 2 cannot completely enter the groove in the nuclear fuel rod insertion hole, and the rear end portion of the nuclear fuel rod 1 is separated from the flat end surface of the graphite block 4. It will be in a protruding state. Therefore, the false loading can be easily found by the appearance of this state.

In the combinations shown in Table 1, for example, enrichment C _{3 · 2}
The nuclear fuel rods to be used, when erroneous loading nuclear fuel insertion hole of the graphite blocks for inserting the nuclear fuel rods for use in the enrichment C _{2 · 2,} enrichment C _{2 · 2} mis loading prevention rib width in nuclear fuel rods to be used for Since the width (W ₃ ) of the rib for preventing misloading in the nuclear fuel used for the enrichment C _{3 · 2} is larger than (W ₂ ), the state in which the nuclear fuel rod is misloaded in the nuclear fuel rod insertion hole of this graphite block is For example, as shown in FIG. 5, the misload preventing rib 2 cannot enter the groove of the nuclear fuel rod insertion hole at all, and the rear end portion (misload preventing rib 2) of the nuclear fuel rod 1 is entirely graphite block 4. It is in a state of protruding from the flat end surface of. Therefore, the false loading can be easily found by the appearance of this state.

In the combinations shown in Table 1, for example, enrichment C _{2 · 1}
The nuclear fuel rods to be used, when erroneous loading nuclear fuel rod insertion holes of the graphite blocks for inserting the nuclear fuel rods for use in the enrichment C _{2 · 2,} enrichment C _{2 · 2} to erroneous loading prevention ribs in nuclear fuel rods to be used length of the insertion direction of the notch (X ₂₎ than the length in the insertion direction of the notch of the erroneous loading prevention ribs in nuclear fuel rods for use in the enrichment C _{2 · 1} (X ₁₎ is small, the graphite When a nuclear fuel rod is incorrectly loaded in the nuclear fuel rod insertion hole of the block, for example, as shown in FIG. 6, the rear end of the notch of the misload preventing rib 2 is the notch in the groove of the nuclear fuel rod insertion hole. The nuclear fuel rod 1 cannot completely enter the protruding portion 4b corresponding to, and the rear end portion of the nuclear fuel rod 1 projects from the flat end surface of the graphite block 4. Therefore,
The false load can be easily detected by the appearance of this state.

In the combinations shown in Table 1, for example, the enrichment C _{2 · 3}
Nuclear fuel rods, the erroneous loading nuclear fuel insertion hole of the graphite blocks for inserting the nuclear fuel rods for use in the enrichment C _{2 · 2,} the insertion direction of the distal end of the spacer in a nuclear fuel rod for use in the enrichment C _{2 · 2} for use in Rather than the length (Y _m-1 ) to the tip in the insertion direction of the nuclear fuel rod, the length from the tip in the insertion direction of the spacer to the tip in the insertion direction of the nuclear fuel rod in the nuclear fuel rod used for enrichment C _2.3 Y _m-2 ) is small, the state in which the nuclear fuel rods are mistakenly loaded in the nuclear fuel rod insertion holes of this graphite block is, for example, as shown in FIG. The nuclear fuel rod 1 cannot completely enter the projecting portion 4a supporting the 3
The rear end of the nuclear fuel rod 1 is projected from the flat end surface of the graphite block 4. Therefore, the false loading can be easily found by the appearance of this state.

[Advantages of the Invention] According to the present invention, (1) it is possible to easily find a wrong loading into a predetermined nuclear fuel rod insertion hole provided in a graphite block, so that a nuclear fuel rod can be inserted accurately without causing a false loading. (2) Since many types of nuclear fuel rods can be obtained, even if the enrichment of nuclear fuel varies, the nuclear fuel rods can be inserted accurately without misloading, and (3) It is possible to provide a nuclear fuel rod having advantages such as easy manufacturing.

[Brief description of drawings]

1 and 2 are explanatory views showing an example of the structure of the nuclear fuel rod of the present invention. FIG. 3 is an explanatory view showing an example of a state in which the nuclear fuel rod of the present invention is correctly loaded into a predetermined nuclear fuel rod insertion hole provided in the graphite block.
4 to 7 are explanatory views showing an example of a state where the nuclear fuel rod of the present invention is erroneously loaded into a predetermined nuclear fuel rod insertion hole provided in the graphite block. 1 ... Nuclear fuel rod, 2 ... Ribs for preventing misloading, 3 ... Spacer, 4 ... Graphite block.

Claims (1)

[Claims] 1. A nuclear fuel rod of (n × m) type loaded on a graphite block and provided with ribs and spacers for preventing misloading on its side surface (where n and m are arbitrary natural numbers). ], The width of the misload preventing rib is W
_k and its length is L _{n-k + 1} [where k
Is an integer of ₁ to n, and W ₁ <W ₂ <... Wn _-1 <W
_n and L ₁ <L ₂ <... Ln _-1 <L _n . ], The length in the insertion direction is X _j on the outer peripheral surface side at the tip in the insertion direction [where j is 1 to 1].
is an integer of _m , and satisfies the relationship of X ₁ <X ₂ <... X _m-1 <X _m ,
X ₁ may be 0. ] The length from the tip of the spacer in the insertion direction to the tip of the nuclear fuel rod in the insertion direction is Y _{m + 1-j} , where j and m have the same meanings as described above. , Y ₁ <Y ₂ <・ ・ ・ ・ ・ ・ Y _m-1 <
The relationship Y _m may be satisfied, and Y ₁ may be 0. ], A plurality of nuclear fuel rod insertion holes provided in the graphite block can be inserted into a specific nuclear fuel rod insertion hole having a groove corresponding to the misload preventing rib and a protrusion supporting the spacer. A nuclear fuel rod, characterized in that