JP3025199B2 - Installation structure of neutron absorbing member for annular tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a neutron shielding structure for an annular tank for safely storing a radioactive liquid containing a fissile substance and the like, and more particularly to a mounting structure for a neutron absorbing member such as a cadmium plate.

[0002]

2. Description of the Related Art A tank for containing a liquid containing a fissile material such as nuclear fuel is formed as an annular tank (critical shape control storage tank) so as not to become critical, and cadmium as a neutron absorbing member is formed along the inner wall surface. A board is attached. The cadmium plate absorbs neutrons emitted radially inward from the fissile material in the annular chamber and prevents a critical reaction.
A conventional cadmium plate mounting structure for this purpose will be described with reference to FIGS. 6 to 8. A cylindrical storage pallet 3 is mounted on a receiving base 2 welded to the bottom of an annular tank 1, and the upper end thereof is placed at the upper end thereof. It is fixed with the holding metal 4. A plurality of receiving frames 5 and 6 are integrally formed in a shelf shape on the outer peripheral surface and the inner peripheral surface of the storage pallet 3, and the annular cadmium plates 7 and 8 are provided in the receiving frames 5 and 6. 9 is inserted and fixed.
In addition, a cylindrical neutron moderating member a is provided upright on the radially inner side of the annular tank 1.

[0003]

In the above-mentioned conventional structure, the cadmium plates 7, 8, and 9 are formed as band members having a predetermined width, so that the cadmium plates themselves are excellent in manufacturability and handleability. However, since the inner cadmium plates 8, 9 and the outer cadmium plates 7 are alternately arranged, there is a physical space between them. For this reason, there is a problem that neutrons are transmitted by streaming or the like, and the neutron shielding effect is reduced. In addition, since a storage pallet having a shelf-shaped receiving frame on the inner and outer peripheral surfaces is used, there is a problem that the width in the radial direction becomes large and the entire apparatus becomes large. Accordingly, an object of the present invention is to provide a neutron absorbing member mounting structure for an annular tank having a simple structure, a compact structure, and a high neutron shielding effect.

[0004]

In order to achieve the above-mentioned object, a neutron absorbing member mounting structure for an annular tank according to the present invention comprises a pair of upper and lower surfaces of an annular tank containing a radioactive liquid. A plurality of sets of upper mounting hooks and lower mounting hooks arranged at intervals in the circumferential direction, a holding member fixed to the upper mounting hooks and supported by hanging along an inner peripheral surface of the annular tank; A sheet-shaped neutron absorbing member extending along the inner wall surface of the annular tank and having a cylindrical shape, a captive bolt having a tip inserted through the upper and lower ends of the neutron absorbing member screwed into the mounting hook, and The holding member is formed of a holding bolt which is screwed through the holding member and whose tip abuts on the inner surface of the neutron absorbing member.

[0005]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Referring to FIGS. 1 and 2, an annular tank 11 having an annular cross section stores a liquid containing a fissile substance therein, and has eight upper circumferential surfaces at equal circumferential intervals. An upper mounting hook 13 is provided. A lower mounting hook 15 is provided on the bottom surface of the annular tank 11 corresponding to the upper mounting hook 13. As shown in an enlarged manner in FIG. 3, the holding member 17 welded and fixed to the inner protrusion of the upper attachment hook 13 hangs down along the inner wall surface of the annular tank 11, and is fixed to the lower attachment hook 15. ing. The holding member 17 has an L-shape in a horizontal section so as to have a predetermined rigidity and to support a reaction force applied to a holding bolt described later. Incidentally, the number of sets of the mounting hooks 13 and 15 is appropriately changed according to the size of the annular tank 11 and the like.

A cadmium plate 21, which is a thin sheet-like neutron absorbing member, extends along the inner wall surface of the annular tank 11 and is formed in a cylindrical shape as a whole. This is because the tips of the holding bolts 23 that have penetrated therethrough are pressed against the inner wall surface. More specifically, the holding bolt 23 is screwed into the holding nut 25 as shown in FIG.
Are fixed to the holding member 17 by welding, the holding bolt 23 extends through the bolt hole of the holding member 17 aligned with the screw hole of the holding nut 25, and the tip thereof is the cadmium plate 21.
Is pressed against the surface. Of course, a screw hole may be directly formed in the holding member 17 and the holding bolt 23 may be screwed into this. Then an appropriate locking is applied.

[0007] The upper edge of the cadmium plate 21 is also held down as in the case of the holding bolt 23 by a mounting bolt 27 threaded through the upper mounting hook 13 as shown in FIGS. In addition, upper mounting hook 1
The tip of a drop-prevention bolt 29 threaded through 3 is inserted into the hole at the upper edge to support the cadmium plate 21 to prevent drop-off. Similarly, the lower end of the cadmium plate 21 is also screwed into the lower mounting hook 15 to prevent the falling-off bolt 19
(See FIG. 2). Note that a member a is provided upright on the inside surrounded by the annular tank 11 and the cadmium plate 21.

In order to form the neutron absorbing member mounting structure having the above structure, the upper mounting hook 13 and the holding member 17 which are welded and joined are first mounted at predetermined positions, and then the cadmium plate 21 is cylindrically mounted at the predetermined position. And the upper end is supported by a falling-off prevention bolt 29, and is pressed and fixed by a mounting bolt 27. And arrange the lower mounting hook 15,
The lower end of the cadmium plate 21 may be supported by the falling-off prevention bolt 19, and finally the cadmium plate 21 may be pressed and fixed to the inner wall surface of the annular tank 11 over the entire surface by the holding bolt 23.

[0009]

As described above, according to the present invention, a continuous sheet-like neutron absorbing member is attached to the inner wall surface of the annular tank, so that there is no gap between the neutron absorbing members as in the prior art. In addition, neutrons flowing inward from the annular tank can be effectively absorbed to prevent criticality. Further, since the inner wall surface of the annular tank is used as one supporting member, and the neutron absorbing member is pressed and supported by adding only the holding bolt and the holding member, the structure is simplified and the device is compact.

[Brief description of the drawings]

FIG. 1 is an overall plan view of an embodiment of the present invention.

FIG. 2 is a vertical sectional view taken along line II-II of FIG.

FIG. 3 is a partially enlarged sectional view of a part III in FIG. 2;

4 is a partially enlarged cross-sectional view of a portion IV in FIG.

FIG. 5 is a partially enlarged elevation view as viewed in the direction of the line VV in FIG. 1;

FIG. 6 is a plan view of a conventional device.

FIG. 7 is a conceptual vertical sectional view of a conventional device.

FIG. 8 is a partially cutaway enlarged perspective view of a conventional device.

[Description of Signs] 11 Annular tank 13 Upper mounting hook 15 Lower mounting hook 17 Holding member 19 Captive bolt 21 Cadmium plate 23 Holding bolt 29 Captive bolt

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-17595 (JP, A) JP-A-5-215890 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G21C 19/40 G21F 9/22

Claims (1)

(57) [Claims] 1. A plurality of sets of upper and lower mounting hooks paired with each other on the upper and lower surfaces of an annular tank containing a radioactive liquid and spaced circumferentially,
A holding member fixed to the upper mounting hook and suspended downward along the inner peripheral surface of the annular tank, a sheet-shaped neutron absorbing member extending along the inner wall surface of the annular tank and forming a cylindrical shape;
A captive bolt screwed into the mounting hook and penetrated at both ends of the neutron absorbing member with a tip inserted therein, and a holding bolt screwed into the holding member and having a tip abutting on the inner surface of the neutron absorbing member A neutron absorbing member mounting structure for an annular tank, comprising: