JPS6153591A - Control rod - 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 [Technical Field of the Invention] The present invention relates to a control rod on the output side of a nuclear reactor using a gas such as helium as a coolant.

[Technical background of the invention and its problems] Generally, in a nuclear reactor, the nuclear fission reactivity of the reactor core is controlled by inserting and removing control rods filled with neutron absorbers into and from the reactor core.

By the way, there are various types of control rods, but for example, in the J3 gas-cooled nuclear reactor, a large number of control rod elements 1 are connected in the 111 line direction to form one life. There is one in which the control rod guide tube 3 and the insertion hole 5 of the reactor core 4 are vented.

In the case of this type of control rod, since the control rod is given flexibility, the degree of freedom of insertion is large even against bending of the control rod guide tube 3 and misalignment 1- of the insertion hole 5. There are advantages.

However, conventionally, the control rod of this scale has each a: I T in J3.
As shown in FIG. 5, the h1l cable 1 is an outer tube portion 6 of a cladding tube 6 formed into a 21i cylindrical shape by welding.
and inner tube part 6. A neutron absorber 7 is accommodated between the neutron absorber 7 and the neutron absorber 7, and a neutron absorber 7 is supported by a spine 9 provided at the upper part of the inner tube part 6b and extending in the axial direction via a spider 8. Therefore, if a control rod consisting of these control rod elements is rapidly fully inserted into the insertion hole of the reactor core during J3 during a scram for the purpose of emergency shutdown of the reactor, the receiving hole will be removed from the wall of the insertion hole. The outer tube portion 68 is strongly heated due to high-temperature thermal radiation and heat conduction via the cold W material, and the inner tube portion 6. The temperature difference between the inner and outer tube parts becomes large, and thermal stress based on the difference in heat 11i311[: is generated in the connecting part between the inner tube part and the outer tube part, and excessive plastic strain may occur in the cladding tube 6. Moreover,
Such rapid insertion of control rods may be performed frequently during the operating period of the nuclear reactor, and there are problems such as the life of the control rods themselves being shortened due to plastic strain of the cladding tube 6 that occurs each time.

[Purpose of the invention]

In view of the above points, the present invention can reduce the thermal stress generated in the cladding tube even if the cladding tube is rapidly inserted into the reactor core.
The objective is to obtain a control rod that can extend its life.

(Summary of the Invention) The present invention provides a control rod formed by connecting a plurality of control rod elements each having a neutron absorber housed between an inner tube portion and an outer tube portion of a cladding tube having a cylindrical shape. In this step, engaging pieces extending in the circumferential direction are provided protrudingly on the inner circumferential surface portions of both upper and lower ends of the outer tube portion, and the engaging pieces are respectively engaged with the outer circumferential outer end edges of the upper and lower main 11 throat portions of the cladding tube. 1°, which allows the relative elongation of the outer tube section with respect to the inner tube section during rapid insertion of control rods, and reduces the heat caused by the difference in thermal expansion. This is designed to reduce stress generation.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 3.

In the figure, reference numeral 10 denotes a control rod element, and this control rod element 10 is similar to the conventional control rod described in +) 1.
A plurality of the rods are connected by a spine 11 on a metal rod, which is placed in the center of the rod, and are moved up and down through a control rod guide tube (not shown) and an insertion hole in the reactor core (not shown).

By the way, the control I4i element 10 has an outer tube portion 12 a
J) and inner tube part 12. The double cylindrical shape formed from <
It has an 'E1 cladding tube 12, and a cylindrical pellet-shaped neutron absorber 13 is housed between the inner and outer tube portions of the cladding tube 12. That is, donut-shaped upper caps 14 are provided at both upper and lower ends of the inner tube part '12b of the cladding tube 12, respectively.
and the inner peripheral part of the lower cap 14b is welded,
Its upper main 11 knob 14 a J) and lower cap 1
4. Notch step portions 158 and 15 extending in the circumferential direction are formed at the outer periphery of the outer edge and the edge thereof, respectively. On the other hand, engagement pieces 16 extending in the circumferential direction are provided on the inner peripheral portions of both upper and lower ends of the outer tube portion 128, respectively. 16. is provided protrudingly, and its retaining piece 16,
16. are the corresponding upper and lower V knobs 14.14b
is engaged with the notch stepped portions 150, 15, thereby forming a double cylindrical covering material 12. Then, the engagement piece 16. 16. and the notch stepped portions 15 , a 15 , the inner tube portion 12 . Relative movement of the outer tube portion 12a in the axial and radial directions due to the thermal eye difference is allowed.

In addition, the inner tube portion 12 of the cladding tube 12. A spider is fixed on the upper inner surface of the spider 17, and an insertion hole 17. is formed in the center of the spider 17. The spine 11 is movably inserted through the spine 11, and the control rod element 10 is supported by engaging the support member 18 fixed to the spine 11 with the lower surface of the spider 17. In addition, the reference numeral 19 in the figure is a guide ring that prevents the control rod element 10 from rolling relative to the spine 11, and the reference numeral 20 is a plurality of guide rings fixed to the outer tube portion 12 of the cladding tube 12 in a conformal manner. These guide fins prevent the outer tube portion 12 from coming into direct contact with the insertion hole of the reactor core and ensure a flow path for the coolant.

However, the control rod configured in this way becomes a control rod drive (not shown)! I! The IJ device is adjusted to its inserted position relative to the reactor core, and the output of the reactor is controlled.

Therefore, in an emergency such as a scram, the control iλl is fully inserted into the reactor core and the reactor operation is stopped.

By the way, in such a control rod rapid insertion port 1, each control rod element 10 receives high temperature heat radiation from the wall surface of the insertion hole of the reactor core, and also receives heat radiation through the cold IJI shrine.
The outer tube part 12. is larger than the inner tube portion 12b (
thermally expands. This thermal expansion difference appears prominently in the longitudinal direction, that is, the axial direction, of the rFi tube 12, but it also occurs in the radial direction, and the outer tube portion 12aG has a relative expansion in the axial and radial directions with respect to the inner tube portion 12b. is born. In other words, in this embodiment, L13 includes engagement pieces 16 . 16b is the upper key I knob 14. and lower key knob 14. Notch step 15 on the outer edge of the outer periphery of
．． 15b, respectively, so that the engaging portions of the outer tube portion 12 and the inner tube portion 12. Relative elongation to Sonoki is allowed. Therefore, the thermal expansion 11
Thermal stress due to the 1u difference is applied to the outer tube portion 12. Inner tube part 12
．． The generation of plastic strain is significantly reduced, and the life of the control rod is prevented from being shortened.

〔Effect of the invention〕

As explained above, in the present invention, engagement pieces extending in the circumferential direction are provided protrudingly on the inner periphery of both upper and lower ends of the outer tube, and the engagement pieces are attached to the outer periphery of the upper and lower ends of the cladding tube. Since the outer tube section is engaged with the inner tube section, the extension of the outer tube section with respect to the inner tube section is allowed, and even if the control rod is rapidly inserted into the core at J5 at the scram port 1st class, the inner tube section, the outer tube section, and the 4j It is possible to reduce the occurrence of thermal stress caused by the heat of the U5 cap, and the occurrence of plastic strain.1 Therefore, it is possible to prevent a decrease in the life of the control rods, improve the operating rate of the reactor, and improve the reactor safety can be improved.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of a control rod element in J3 of the control rod of the present invention, Fig. 2 is an enlarged view of the control rod element in Fig. 1 with some parts omitted, and Fig. 3 is an enlarged view when the outer tube section is extended. Fig. 4 is a schematic composition diagram of the control rod insertion part of a gas-cooled nuclear reactor, and Fig. 5 is a longitudinal cross-sectional view of the part corresponding to Fig. 2.
It is a board flJi side view of the l dedication element. 10... Control rod element, 11... Spine, 12...
- Cladding tube, 12a... outer tube part, 12. ...Inner tube part,
13... Neutron absorber, 148... Upper cap,
14... Lower cap, 15. 15b... Notch step, 16. 16b...Engagement piece. Demoto Jg! Human boar crotch h1 1st 64th

Claims (1)

[Scope of Claims] A control rod formed by connecting a plurality of control rod elements configured by housing a neutron absorber between an inner tube part and an outer tube part of a cladding tube having a single or double cylindrical shape. In this case, engagement pieces extending in the circumferential direction are provided protrudingly on the inner periphery of both the upper and lower ends of the outer tube part, and the engagement pieces are respectively engaged with the outer periphery outer ends of both the upper and lower cap parts of the cladding tube. A control rod characterized by: 2. The control rod according to claim 1, wherein the engaging piece is engaged with a circumferential notch step formed on the outer edge of the cap portion. .