JPS61120083A - 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 The present invention relates to nuclear reactors, and more particularly to nuclear reactors having a neutron reflector surrounding the reactor core to minimize neutron losses.

In order to reduce the leakage of neutrons from the reactor core, a structure consisting of a core baffle and its mounting plate called a 7t-ma has conventionally been provided around the reactor core, but recently it has become necessary to increase the fuel cycle cost. (Aiming to reduce the number of factors, there is a growing movement to adopt neutron reflectors instead of such structures.

The neutron reflectors include a reflective material inside the shroud, and are installed in large numbers adjacent to the inner surface of the core tank to surround the reactor core. Because there is a gap between the core and the fuel assemblies around the core, the coolant not only flows through the fuel assemblies;
A part of it flows through the FA 111 mentioned above. Therefore, if 10,000-
If a critical pressure differential develops between the flow through the gap and the flow through the fuel assembly, there is potential for damage to the fuel rods from the noet flow of coolant.

It is therefore an object of the present invention to eliminate the potential for such fuel rod damage in nuclear reactors with neutron reflectors.

For this purpose, the nuclear reactor of the present invention is provided with pressure drop adjustment grooves formed on the outer surface of the neutron reflector at the same height as the support grid members arranged at intervals in the longitudinal direction of the nuclear fuel assembly. It is characterized by the following. Because the pressure drop adjustment groove exists, the pressure drop of the coolant flowing through the gap between the neutron reflectors and the gap between the neutron reflector and the fuel assembly around the core is substantially equal to the pressure drop of the coolant flowing through the core. , and the coolant pressure distribution in the radial direction of the core is flattened.

Next, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a cross-sectional view of a nuclear reactor in which the present invention is implemented. The nuclear reactor vessel 51 is comprised of a hemispherical upper lid 5 that is detachably attached.

A core tank 2 is vertically disposed concentrically within the vessel body 1a, and the outer peripheral surface of the core vessel 2 cooperates with the vessel body 1a to define an annular coolant descending region 16 between the two. do. A lower core plate 10 in which a number of coolant flow holes 10a (Fig. 3) are bored is attached to the bottom of the core tank 2, and the lower core plate 10 cooperates with the hemispherical bottom of the vessel body 1a. The lower plenum 11 is formed by forming the lower plenum 11. On the lower core plate 10 and between the upper core plate 9 and the upper core plate 9, a plurality of nuclear fuel assemblies 3 (only two of which are shown in FIG. 1) constituting the reactor core are erected side by side. There is.

This upper core plate 9 located directly above the bottom part of the fuel assembly 3, the inner fii 18 that suspends and supports it, and a large number of II + rod assembly guides #J15 vertically inside the inner cylinder 8. constitutes an upper core tank body.A control rod drive shaft guide structure 14 that defines a coolant outlet Matsunai plenum 12 is disposed in the upper part of the upper core structure body.1 body 5 A control drive device 13 is attached to the control rod assembly 13, and the control rod assembly connected to a drive shaft (not shown) has a control rod drive length W11.
3 is driven up and down through the control rod assembly guide tvI15 to control the reactivity of the core described above in a known manner.

A large number of radial neutron reflectors 4 are erected on the inner surface of the reactor core barrel 2 at positions surrounding the reactor core.

Showing one quadrant of the core barrel inner cross section along A-AM in Figure 1! As is clear from jS2UjJ, each neutron reflector 4
are attached to the reactor core [2 by ports 17, and the inner and outer walls of these neutron reflectors 4 define a storage space for the fuel assembly 3. As shown in FIG. 4, the neutron reflector 4 is formed of a shroud 18 and a reflective material 19 contained within the shroud 18 and made of a material having a large scattering δL cross-section and a relatively small absorption cross-section. It has a box-shaped structure.

As shown in FIG. 3, the fuel assembly 3 includes a plurality of support grid members 22 arranged at intervals along its longitudinal direction.
As is well known to those skilled in the art, a number of fuel rods 21 are received and supported in openings (not shown) in the support grid member 22. As shown in FIGS. 3 and 5, a pressure adjustment groove 20 is provided on the outer surface of the shrouding plate 18 of the above-mentioned neutron reflector 4 at the same height as the supporting grid member 2Z. There is. In the embodiment, there are two grooves 20 with a channel-shaped cross section corresponding to each support grid member, but the number of grooves can be changed if the coolant differential pressure in the reactor radial direction can be reduced as desired. , shape, etc. may be arbitrary.

During operation of the reactor, coolant enters the reactor vessel 1 through the inlet/slip 6 at the top of the vessel body 1a and flows downwardly as indicated by the arrows through the annular descending region 16 and into the lower plenum 1.
Reach 1. The coolant changes its flow direction upward in the lower plenum 11 and flows into the core region through coolant flow holes 10a (see FIG. 3) in the lower core plate 10.

Most of the coolant flows upward through the fuel assembly 3 of the core, and the remaining -66 flows as a bypass flow l! It flows upward through the gap IJ] 23 between the tangential neutron reflectors 4 (FIG. 2) and the gap 24 between the neutron reflectors 4 and the outermost fuel assembly 3. Thereafter, the coolant heated through the fuel assembly 3 passes through the coolant flow hole 9a in the upper core plate 9, the control control collection guide 1iIl15, the outlet Matsunai plenum 12, etc. as shown by the arrow. From the outlet/spool 7, it is supplied, for example, to an external steam generator (not shown) as a primary coolant.

In the core region, the flow of coolant through the fuel assemblies is
The pressure drops due to the frictional resistance of the fuel rods 21 and the pressure loss at the support grid member 22. On the other hand, the flow through the gaps 23 and 24 defined by the neutron reflector 4 is
Pressure drops due to frictional resistance on the outer surface of groove 8 and pressure loss at groove 2σ. At this time, since the grooves 20 are provided at the same height position as the support grid member 22, the pressure loss due to the expansion and contraction flow of the coolant when passing through the grooves 20 is the same as the pressure loss of the coolant at the support grid member Z2. It can be done to a certain extent.

As described above, according to the present invention, pressure loss adjustment grooves are formed on the outer surface of the neutron reflector at the same height as the support grid members disposed at intervals W1 in the longitudinal direction of the nuclear fuel assembly. This prevents the generation of pressure differentials in the radial direction of the core in the upward flow of coolant along the fuel assemblies and neutron reflectors, reducing the potential for damage to fuel rods due to noet flow of coolant due to differential pressure. This can eliminate concerns and make nuclear reactors more reliable.

[Brief explanation of the drawing]

Figure tI & 1 is a cross-sectional view of the nuclear reactor in which the present invention is implemented,
The figure is a cross-sectional view showing one quadrant of the inside cross section of the core barrel taken along line A-A in Figure 1, and Figure 3 is a pressure loss r in the neutron reflector.
A partial cross-sectional view showing the positional relationship between the I411ji groove and the support grid member of the fuel assembly, FIG. 4 is a cross section taken along line B-B in FIG. 3, and FIG. 5 is an enlarged view of section C in FIG. 3. It is. 1... Single atomic f container, 1 &... Container body, 2... Core tank, 3... Fuel assembly, 4... Neutron reflector, 5
... Upper lid body, 8 ... Inner cylinder, 9 ... Upper core plate,
9a... Coolant flow hole, 10... Lower core plate, 10
m... Coolant flow hole, 11... Lower plenum, 12
...Exit Matsunai plenum, 13...Control rod drive device, 1
4... Control rod drive shaft guide structure, 15... Control rod assembly guide section, 16... Annular descending region, 17... Bolt, 18... Turning plate, 19... Reflection Material, 20...
Pressure drop adjustment groove, 21...Nuclear fuel assembly, 22...Fuel rod. Continuing from page 1, 1, 3, 4, horse 5, ward Y1 Inventor: Katsutoshi Shimizu Otemachi-style company, Chiyoda-ku, Tokyo Inventor: Eiji Yoshikawa Wadazaki-chosha, Hyogo-ku, Kobe City Kobe Inside the shipyard

Claims (1)

[Scope of Claims] A nuclear reactor vessel having a removable upper lid, a reactor barrel suspended within a body of the vessel and cooperating with the body to define an annular descending area for coolant, and a reactor core. a lower core plate installed at the bottom of the tank and having a large number of coolant flow holes; a plurality of nuclear fuel assemblies standing in line on the lower core plate to constitute the core; An upper core structure including an upper core plate located directly above the head, an inner cylinder that suspends and supports the upper core plate, and a number of control rod assembly guide cylinders; A nuclear reactor having: a control rod drive shaft guide structure defining an exit turning plenum; a large number of neutron reflectors standing adjacent to an inner surface of the reactor core barrel and surrounding the reactor core, comprising: an outer surface of the neutron reflector; has an opening for receiving and supporting a large number of nuclear fuel rods of the nuclear fuel assembly, and has a pressure drop adjusting groove at the same height as the support grid members arranged at intervals in the longitudinal direction of the nuclear fuel assembly. A nuclear reactor characterized by the formation of