JPH0419595A - Moderator adjusting control rod driving device for nuclear reactor - Google Patents

Abstract

PURPOSE:To shorten the time of installation and operation for an orifice device outside a top cap by cutting off a flow guide passage by a valve body arranged in the valve chamber of the flow guide passage in the case of the breakage of a water feed and discharge line where differential pressure is applied across the flow guide passage. CONSTITUTION:The moderator adjusting control rod driving device (h) for the nuclear reactor is constituted by providing a piston (j) in a housing (k) where the top cap l having the flow guide passage l1 to piping (water feed and discharge line) m is provided at the upper end. The piston (j) receives the differential pressure between the pressure of a high-pressure primary cooling material from the opening part (n) of the device (h) in the nuclear reactor container and the pressure in the piping (m) and lifts a connected moderator material adjusting control rod (i). At this time, the spherical valve body 2 is provided in the valve chamber 1 which has a valve seat 1a in the flow guide passage l1. In normal operation, the valve body 2 floats slightly, but the valve body 2 is pressed against the valve seat 1a with the differential pressure across the cap l in the case of the breakage of the piping (m) to close or cut off the flow guide passage l1. Thus, the orifice device (q) can be provided on the down stream side of the piping (m).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pressurized water nuclear reactor, and particularly to a moderator adjustment control rod drive device used in the reactor.

[Prior Art] Fig. 4 shows an example of a typical conventional pressurized water reactor, in which inside the reactor vessel a, there are a plurality of fuel assemblies (only two (representatively shown) b, an in-core instrumentation guide pipe C that guides a detector (not shown) disposed below to measure the situation inside the reactor to the inside of the fuel assembly, and a fuel assembly. Control rod cluster guide tubes d and the like are provided in a row above the body to guide the vertical movement of control rods (not shown) that control the number of nuclear fission.

Further, above the control rod cluster guide tube d, there is provided a control rod drive device mounting adapter f that protrudes to the outside of the lid body e of the reactor vessel a, and the control rod drive device mounting adapter f includes: A control rod drive device g that holds the aforementioned control rods and moves them up and down, and a moderator adjustment control rod drive device g are attached.

As can be understood from Fig. 5, the moderator adjustment control rod drive device includes a piston j that grips the moderator adjustment control rod i at its lower end, an inner pipe k as a housing or cylinder tube, and a piston j that is held at its upper part. a latch mechanism for
and a top cap 1 forming a pressure boundary.

The pipe m pulled out from the top cap l is connected to the switching valve (
(not shown), and if the supply and drainage line of the moderator adjustment control rod drive device is opened to the atmosphere by operating the switching valve, the piston j will be connected to the moderator adjustment control rod located inside the reactor vessel a. The moderator adjustment control rod i is pulled up because it is pushed up by the differential pressure between the pressure of the high-pressure primary coolant flowing in from the opening n of the rod drive device and the pressure of the water supply and drainage line.

Furthermore, as shown in FIGS. 2 and 3, a pair of filter devices, that is, a wire mesh Q, and an orifice device q between the wire mesh Q are installed at the entrance/exit portion of the tip of the pipe m on the top cap L side. The sludge in the fluid is removed using a wire mesh Q, and the orifice device Q having a multistage orifice plate P narrows the passage cross-sectional area of the fluid to increase flow resistance and reduce the discharge flow rate of the fluid, thereby controlling the moderator adjustment. Care has been taken to ensure that the rod i is pulled up slowly.

In this way, in the conventional moderator adjustment control rod drive device, when the water supply and drainage line is ruptured, the water supply and drainage line is opened to the atmosphere, and the moderator adjustment control rod i is carelessly and rapidly pulled up, causing damage to the reactor. The primary coolant in container a is piston j
A multistage orifice device q is embedded in the top cap l in order to suppress a drop in the pressure inside the reactor vessel a due to a slight outflow from the seal portion of the reactor vessel a.

[Problems to be Solved by the Invention] However, with the configuration in which the orifice device is embedded in the top cap as described above, it is necessary to replace the orifice device q due to clogging of the wire mesh Q at the entrance and exit of the orifice device q. If this occurs, it is necessary to cut the weld between the top cap and the water supply and drainage line, replace the orifice device, and re-weld the top cap and the water supply and drainage line in a crowded place with various structures. First, it poses problems such as the complexity of preparing special tools, lengthening of working time, and increased radiation exposure for workers, so improvements have been desired.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a moderator adjustment control rod drive system that is improved so as to eliminate the above-mentioned problems.

[Means for Solving the Problems] In order to achieve this object, the present invention provides a housing having a top cap at the upper end having a channel communicating with a water supply and drainage line, and connected to a moderator adjustment control rod. moderator adjustment of a nuclear reactor, the piston is adapted to withdraw a moderator adjustment control rod in response to a differential pressure between the pressure of the primary coolant in the reactor vessel and the pressure of the water supply and drainage line. In the control rod drive device, a valve body formed in the diversion path and housed in a valve chamber having a valve seat, and an orifice detachably provided outside the top cap in a water supply and drainage line communicating with the diversion path. The invention is characterized in that it comprises a device.

[Function] During normal operation, the valve body is slightly lifted up, but in the event of a break in the water supply and drainage line, etc., the valve body is pressed against the valve seat by the large pressure difference before and after the top cap, and the flow guide path is It is blocked or shut off to prevent the moderator adjustment control rod from being pulled out and prevent fluid from ejecting.

By providing the valve valve and valve chamber in the flow channel in this way,
The orifice device, which was conventionally provided in the top cap, can now be provided downstream of the water supply and drainage line.

If provided at such a position, there is no need to cut or re-weld the welded portion when replacing the orifice.

[Embodiment] Next, a preferred embodiment of the moderator adjustment control rod drive device according to the present invention will be described in detail with reference to the accompanying drawings, in which the same reference numerals indicate the same or corresponding parts. shall be.

FIG. 1 is an enlarged sectional view showing the vicinity of the top cap l of the moderator adjustment control rod drive device according to the present invention.
1, and the portions below the portions shown in FIG. 1 may be the same as the conventional one shown in FIG. 5, and are therefore omitted from illustration.

In FIG. 1, reference numeral 1 denotes a space as a valve chamber formed at the lower end of the flow guide path r1 of the top cap l that communicates with piping m (water supply and drainage line), and reference numeral 2 denotes a space accommodated in the same space 1. The spherical valve body, reference numeral 3, is a lid for preventing the valve body 2 from falling off, and has an opening 3a. The outer diameter of the valve body 2 is the opening 3a.
, but smaller than the radial dimension of the channel 11. In addition, the radial dimension of the space 1 is the guide path 11
The annular shoulder or valve M1a is formed between the two. Shoulder part 1a
It is preferable that the shape is a curved surface that follows the outer shape of the valve body 2.

Also, there is a top cap for piping m! A filter device, which may be the same as the conventional filter device shown in FIG. 3, ie, a wire mesh Q and an orifice device q are removably disposed at a position above the filter with a pipe joint or nipple interposed therebetween.

During normal operation, the valve body 2 is designed to float slightly and allow a small amount of primary coolant to flow out, but if the water supply and drainage line breaks, the moderator adjustment control rod drive Due to the large pressure inside the valve (acting in the direction shown by the arrow in the figure), the valve body 2 rises and is pressed against the shoulder 1a as shown by the chain line, blocking the flow guide path r1 and removing the moderator. This prevents the adjustment control rod i (see FIG. 5) from being pulled out and fluid from flowing out from a break in the water supply and drainage line (not shown).

Further, even if the water supply and drainage line is opened to the atmosphere when the orifice device q provided in the pipe m is replaced as described above, the valve body 2 rises to the position shown by the chain line and operates as described above.

[Effects of the Invention] As described above, according to the present invention, a valve chamber is formed in the flow guide path of the top cap, and a valve body is disposed within the valve chamber, thereby creating a large difference between both ends of the flow guide path. The valve body shuts off the flow guide path in the event of a rupture in the water supply and drainage line under pressure, so the orifice device, which was conventionally buried in the top cap, can now be installed outside the top cap, where it can be easily replaced. When replacing the orifice, not only does it eliminate the need to cut and re-weld the weld between the top cap and the water supply and drainage line, but it also eliminates the need for special tools, reduces work time, and reduces worker radiation exposure. reduction can also be achieved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the main parts of a moderator adjustment control rod drive device according to the present invention, FIG. 2 is a cross-sectional view showing the main parts of a conventional moderator adjustment control rod drive device, and FIG. Fig. 2 is an enlarged cross-sectional view of the area surrounded by a circle ■, Fig. 4 is a schematic cross-sectional view of a typical pressurized water reactor having a moderator adjustment control rod drive device, and Fig. 5 is a conventional pressurized water reactor. FIG. 2 is a cross-sectional view showing the overall structure of the moderator adjustment control rod drive device in a longitudinally shortened form. 1... Valve chamber 2... Valve body 1a... Valve seat a... Reactor vessel h... Moderator adjustment control rod drive device i... Moderator adjustment control rod j... Piston k...Housing! ...
Top cap 11... Channel m... Piping (supply and drainage line) Mitsubishi Heavy Industries, Ltd. Mitsubishi Atomic Crab Industry Co., Ltd. Figure 4

Claims (1)

[Claims] A piston connected to a moderator adjustment control rod is provided in a housing having a top cap at its upper end having a diversion passage communicating with a water supply and drainage line, the piston being connected to the pressure of the primary coolant in the reactor vessel and the pressure of the primary coolant in the reactor vessel. In a moderator adjustment control rod drive device for a nuclear reactor, which is configured to extract the moderator adjustment control rod in response to a pressure difference between the pressure of the water supply and drainage line, the valve chamber is formed in the flow guide path and has a valve seat. A moderator adjustment control rod drive device for a nuclear reactor, comprising a housed valve body and an orifice device detachably provided outside the top cap in the water supply and drainage line communicating with the flow guide path.