JPS6193998A - Method of overhauling nuclear reactor container made of prestressed concrete - 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 "Field of Industrial Application" The present invention relates to a method for dismantling a reactor containment vessel made of prestressed concrete.

``Prestressed concrete'' compensates for concrete's low tensile strength by pre-applying compressive stress to the concrete wall using high-tensile steel (hereinafter referred to as PCI material). This technology increases the mechanical strength of various structures by preventing tensile stress from occurring in concrete walls, and is also being applied to the walls of nuclear reactor containment vessels, which require high internal pressure strength.

By the way, when dismantling a reactor containment vessel constructed from such prestressed concrete after its useful life has elapsed, for example, using a concrete crusher, etc.
It is conceivable that applying impact, vibration, etc. to a concrete wall can cause cracks to occur and cause it to break.

``Problems to be Solved by the Invention'' However, with this type of demolition method, it is not easy to generate tensile stress that exceeds the compressive stress caused by prestress and can cause cracks in the conecrete wall, leading to fracture. The problem is that it requires a lot of effort and takes a long time. In particular, if radioactive materials remain in the reactor containment vessel, there is a risk of an increase in radiation exposure during demolition work.

The present invention effectively solves the above problems, and facilitates the generation of tensile stress in prestressed concrete walls, reducing the force required for destruction, improving the efficiency of demolition work, and shortening the work time. The purpose is to

"Means for Solving the Problems" The present invention releases the tension of the PCM material applying prestress to make it easy to generate tensile stress in the concrete wall, and then prestresses the concrete wall. This creates a tensile stress in the opposite direction to the direction in which it was acting, causing it to break.

"Example" Hereinafter, one embodiment of the present invention will be described based on the drawings.

First, an example of a nuclear reactor containment vessel to which the method of the present invention is applied will be described. The walls of the reactor containment vessel are constructed by arranging prestressing steel materials 2 vertically and horizontally on the foundation 1 with 7-spring pipes 3 inserted, thereby creating a dome-shaped steel wall 4 as shown in Fig. 1. The steel wall 4 is constructed in advance, and formwork (as shown in the diagram) is installed on both sides of the steel wall 4.
After pouring and hardening concrete while placing
As shown in FIGS. 2 and 3, each PCA material 2 is tensioned and its both ends are fixed to a concrete wall 6 with fixing fittings 5 using screws or wedges, etc.
The space between the A material 2 and the north pipe 3 is filled with grout 7, and by creating compressive stress along the PCA material 2 in the concrete wall 6, it is possible to prevent any damage inside the reactor containment vessel. This ensures high internal pressure strength against accidents.

Next, a method for dismantling such a reactor containment vessel will be explained.

First, by removing the fixing fittings 5 and releasing the tension in each 20w4 material 2, the prestress that was acting along the PC steel material 2, that is, the compressive stress, is removed from the concrete wall 6, and at the same time, using gloss etc. PCA material 2 as appropriate
Pull it out from the north pipe 3.

Then, as shown in FIG. 4, an internal pressure p is applied to the reactor containment vessel due to, for example, water pressure. When the prestress is released, a stress in the opposite direction to the direction in which the prestress was applied, that is, a tensile stress p1, is applied to the concrete wall 6, whose strength has been reduced due to the release of the prestress, along the hole after the prestressed steel material 2 is pulled out. The tensile stress p1 causes a crank C to form in the Hungkurito wall 6, leading to its destruction. In addition, the work to apply internal pressure to the reactor containment vessel is carried out in the reactor containment vessel, which has a structure in which cooling water is permanently stored in a part called a sub-reconchamber in case of an accident during reactor operation. In such cases, internal pressure can be efficiently applied by adding water to the cooling water.

In addition, by leaving a part of the PC steel material 2 in the concrete wall 6 after releasing the tension, the concrete wall 6 can be destroyed while connected by the PCA material 2, and debris etc. can be effectively prevented from scattering. can be suppressed. It is also possible to destroy the conocrete wall 6 using auxiliary means such as locally applying impact, vibration, etc. using a concrete crusher or the like.

"Effects of the Invention" As explained above, according to the method for dismantling a reactor containment vessel made of prestressed conocret of the present invention, pca
By relaxing the tension in the PCM material and releasing the prestress acting along the PCM material, the concrete wall was in a state where it was easy to generate tensile stress, and then the prestress was applied to the concrete wall. By generating tensile stress in the opposite direction to the fracture, the force required for the fracture can be reduced, and the efficiency of disassembly work can be improved and the working time can be shortened.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention. Fig. 1 is a perspective view showing an example of the arrangement of PC&Il materials in a reactor containment vessel to which the present invention is applied, and Fig. 2 is a cross-sectional view of the wall of the reactor containment vessel. Fig. 3 is an enlarged view of the part indicated by the chain line ■ in Fig. 2, and Fig. 4 is a partially omitted cross-sectional view of the wall of the reactor containment vessel shown to explain the action at the time of destruction. . 1. Basics, 2. 4'CMH13 north tube, 4
Steel wall, 5...Fixing metal fittings, 6 Concrete wall, 7
... Grout, C... Crack. Applicant Ishikawajima Harima Heavy Industries Co., Ltd. Figure 1

Claims (1)

[Claims] In a method for dismantling a reactor containment vessel made of prestressed concrete, after releasing the tension of the high-tensile steel material that applies prestress to the concrete wall, the concrete wall is pulled in the opposite direction to the direction in which the prestress was acting. A method for dismantling a reactor containment vessel made of prestressed concrete, characterized by generating stress and destroying it.