JPS5819237B2 - Reactor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nuclear reactor, and in particular to a radial blanket fuel assembly loaded in a fast breeder reactor, in response to an increase in output over time of a so-called radial blanket fuel assembly (hereinafter simply referred to as a radial blanket). The present invention relates to a nuclear reactor in which the flow rate of coolant flowing through a blanket can be adjusted.

□Generally, by changing the diameter of the orifice provided in the inlet nozzle of the diameter blanket in a nuclear reactor, the flow rate of the coolant flowing through the diameter blanket can be adjusted for each individual.

For diameter blankets whose calorific value changes over time, the orifice diameter is set to match the assumed maximum calorific value.

However, in fast breeder reactors, the plutonium produced during reactor operation contributes to combustion, so when the diameter blanket stays in the reactor for a long time, the calorific value of the diameter blanket immediately after loading and just before unloading increases. There is a very big difference.

Moreover, in order to reduce heating costs, it is better to make the residence time of the diameter blanket in the furnace for a long period of time, for example, 5 to 10 years, so the change in heat generation of the diameter blanket over time becomes larger and larger. With a diameter blanket in which the orifice diameter is fixed, there is a risk that there will be excess or deficiency in the flow of coolant, resulting in a decrease in heat exchange efficiency.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a nuclear reactor in which the flow rate of coolant flowing through a diameter blanket can be adjusted in accordance with the increase in output of the diameter blanket over time.

According to the present invention, an extension rod that passes through a shielding plug of a reactor vessel to a grip head at the upper end of each diameter blanket, a thermocouple attached to the tip of the extension rod, and a thermocouple attached to the tip of the extension rod are provided. A temperature sensor that detects the coolant temperature of each diameter blanket through a pair of wires, a rod drive device that operates each extension rod from outside the shielding plug, and a flow rate adjustment consisting of the grip head and the tip of the extension rod. A device is attached to the device, and the rod driving device adjusts the opening degree of the coolant flow path in the flow rate adjusting device via the extension rod according to the temperature of the coolant detected by the thermocouple and the temperature sensor. This is achieved by

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 indicates a nuclear reactor vessel, and in the center of this reactor vessel 1, a reactor core, which is indicated as a whole by reference numeral 2, is installed.

The reactor core 2 has a large number of diameter blankets 4, 4 arranged in a row on a core structure 3.

Above each diameter blanket 4, an extension rod 6 is provided coaxially with the diameter blanket 4, passing through a shielding plug 5 covering the upper opening of the reactor vessel 1 and reaching a grip head at the upper end of the diameter blanket.

This extension rod 6 is driven by a short distance in the axial direction by a rod drive device 7 provided on the shielding plug 5, as required.

The rod driving device 7 as described above is constructed by, for example, installing a parallel rack on the axis of the extension rod 5 on the side surface of the extension rod 5 on the shielding plug 7, and connecting a pinion that meshes with the rack to the output shaft of the motor. It can be configured as follows.

Furthermore, a thermocouple 8 is attached to the tip (inner end) of the extension rod 5, as shown in FIG.

The output of the thermocouple 8 is supplied to a temperature sensor (not shown) by a conductive wire drawn out along the central axis of the extension rod 6.

On the other hand, as shown in FIG. 2, the grip head 9 provided at the upper end of the diameter blanket 4 and the tip of the extension rod 6 constitute a coolant flow rate adjustment device 11.

That is, the inner cylindrical portion of the grip head 9 is formed in a funnel shape, and the small diameter end portion 12 of the extension rod 6 is loosely inserted into the grip head 9.

As shown in FIGS. 2 and 3, a plurality of recesses 13 (four in the figure) are formed in the boundary step 10 between the extension rod 6 and the small diameter portion 12 at its tip. It is formed.

This concave portion 13 is provided to allow the coolant to flow through this joint even when the boundary step portion 10 is joined to the top surface of the grip head 90 without a gap.

In the nuclear reactor according to the present invention configured as described above, immediately after loading the diameter blanket that generates less heat, the small diameter portion 12 at the end of the extension rod is deeply inserted into the grip head 9, as shown in FIG. Either the boundary step 10 contacts the top surface of the grip head 90, or only a small gap exists between them.

In this case, the funnel-shaped inner cylinder part of the grip head 9,
Since the annular gap between the extension rod and the small-diameter stepped portion 12 is small, and the gap near the boundary step 10 is also small, the coolant flows inside the diameter blanket 4 and flows out along the arrow in FIG. is subject to large resistance and therefore low flow rate.

As the residence time in the furnace becomes longer (as the calorific value of the diameter blanket 40 increases), the coolant temperature detected by the thermocouple 8 and a temperature sensor (not shown) increases.

At that time, the rod driving device 7 is operated to pull out the extension rod 6 slightly upwardly so that the coolant temperature becomes constant.

When the extension rod is pulled out, the small diameter portion 12 at the tip of the extension rod
Since the coolant flow path around the tube is enlarged, the coolant flow rate increases, so that the coolant temperature, which once increased, returns to its original value.

If the extension rod 6 is pulled out in accordance with the increase in the calorific value of the diameter blanket 40 in this manner, the state shown in FIG. 4 will be reached at the end of the stay of the diameter blanket 4 in the furnace.

5 to 7 show a modified embodiment of the present invention, in which the coolant flow rate is adjusted by rotating the extension rod about its axis.

That is, as shown in FIG. 5, the grip head 9 includes a large inner diameter portion 15 having a plurality of first flow holes 14 14 opened on the side surface, and a large inner diameter portion 15 that is integrally connected below the large inner diameter portion 15 . The small inner diameter portion 16 is

On the other hand, the tip of the extension rod 6 is formed with a cylindrical portion 17 that is loosely inserted into the small inner diameter portion 16,
A plurality of second communication holes 18,
18 is open.

Immediately after the diameter blanket 4 is loaded, as shown in FIG. 6, the degree of alignment between the first and second flow holes 14 and 18 is reduced to increase the flow resistance of the coolant and thereby increase the flow rate of the coolant. When the amount of heat generated is large just before taking out the diameter plunget 4, the first and second flow holes 14 and 18 are aligned to increase the coolant flow rate, as shown in FIG. It is designed to be able to be absorbed into

It goes without saying that when it is necessary to rotate the shielding plug 5 during fuel exchange, the extension rod 6 is completely pulled out from the grip head 9.

As is clear from the above description, the present invention expands the flow path of the flow rate adjustment device 11 and increases the flow rate of the coolant in accordance with the increase in the calorific value of the diameter blankets 4 over time. As a result, the outlet temperature of the entire core is flattened and thermal efficiency is improved.

Further, since the diameter blankets 4, 4 can be loaded in the furnace for a long period of time, fuel costs can be reduced.

Furthermore, since the coolant is not overheated, various effects can be achieved, such as the thermal stress in the upper structure of the reactor core being alleviated.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a nuclear reactor according to an embodiment of the present invention, in which only one extension rod is shown for clarity, and FIG. 2 shows a flow control device immediately after loading the diameter blanket. 3 is an enlarged cross-sectional view along line 21 mm, FIG. 4 is a sectional view similar to FIG. 2 immediately before taking out the diameter blanket, and FIG. 5 is another embodiment of the present invention. FIGS. 6 and 7 are a longitudinal cross-sectional view of the flow rate adjusting device, respectively, showing the flow rate adjusting device immediately after loading the diameter blanket and immediately before taking it out. 1...Reactor vessel, 2...Reactor core, 3.
... Core structure, 4 ... Diameter blanket fuel assembly, 5 ... Shielding plug, 6 ...
・・Extension rod, 7・・Rod drive device, 8・
...Thermocouple, 9...Grip head, 1
DESCRIPTION OF SYMBOLS 1...Flow rate adjustment device, 12...Tip small diameter part, 14...First circulation hole, 15...
Large inner diameter part, 16... Small inner diameter part, 17...
-Tip cylindrical part, 18...second flow hole.

Claims (1)

[Scope of Claims] 1. A reactor core in which a large number of diameter blanket fuel assemblies are arranged and held on a core structure, a reactor vessel that houses this reactor core, and a shielding plug that closes an upper opening of this reactor vessel. and a coolant for cooling the reactor core, and a coolant circulation device for circulating the coolant, an extension rond penetrating the shielding plug and reaching a grip head at the upper end of each diameter blanket, and this extension. A thermocouple installed at the tip of the rond, a temperature detector that detects the coolant temperature of each diameter blanket fuel assembly via this thermocouple, and a rond drive device that drives each extension rond from outside the shielding plug. and a flow rate adjustment device consisting of the grip head and the tip of the four extensions, and according to the temperature of the coolant detected by the thermocouple and the temperature sensor, the Rondo drive device: A nuclear reactor characterized in that the opening degree of a coolant flow path in a flow rate adjustment device is adjusted via an extension iron, thereby adjusting the flow rate of coolant in a diameter blanket fuel assembly. 2. The flow rate adjustment device consists of a grip head having a funnel-shaped inner cylinder part and a small diameter portion at the tip of an extension iron that is loosely inserted into the grip head, and by moving the extension iron in the axial direction □, 2. The nuclear reactor according to claim 1, wherein the annular gap between the small-diameter cylindrical portion and the inner cylindrical portion of the grip head is varied. 3. The flow rate adjustment device includes a grip head having a large inner diameter portion with a first flow hole opened on the side surface and a small inner diameter portion connected below the large inner diameter portion, and a grip head with a second flow hole opened on the side surface. It consists of a cylindrical end portion of an extension iron that is loosely inserted into the small inner diameter part of the head, and by rotating the extension iron around its axis, the degree of alignment between the first and second flow holes can be changed. characterized by
A nuclear reactor according to claim 1.