RU2714122C1 - Container for transportation and storage of spent fuel assemblies of vver-type reactor - Google Patents

Abstract

FIELD: packaging and storage.

SUBSTANCE: invention relates to designs of containers from high-strength cast iron with spherical graphite for transportation and storage of spent fuel assemblies of VVER-1000/1200 type reactor. Container for transportation and storage of spent fuel assemblies of VVER-type reactor comprises central support tube arranged on support and sections with vertical hexagonal holes installed coaxially to pipe. Each section is made of high-strength cast iron with globular graphite alloyed with gadolinium in the form of solid cast cylinder with central hole and thickness of walls between hexagonal holes of 50–55 mm.

EFFECT: invention allows arrangement of maximum number of fuel assemblies.

1 cl, 2 dwg

Description

The invention relates to the construction of containers of ductile iron with spherical graphite for transportation and storage of spent fuel assemblies of the reactor type VVER-1000/1200.

A well-known container for transporting and storing spent nuclear fuel comprising a cast iron housing with spherical graphite with molded profile metal tubes made of boron steel ChS82, placed around a central pipe on a support.

(RU 187096, G21F 5/00, published 02/19/2019)

A disadvantage of the known technical solution is the lack of heat transfer and neutron protection, which requires the inclusion of additional inserts in the device and the formation of thermal bridges, which increases the complexity of manufacturing and operating the known device.

The closest in technical essence is a container for transporting and storing fuel assemblies, including a central supporting pipe made of corrosion-resistant steel, connected to a support, on which coaxially mounted pipes are secured to each other along the height of the section, each of which is made of two racks separated from the racks of steel with hexagonal holes placed between them, formed by aluminum pipes, which are equipped with plates of a boron composite inside. In this case, the hexagonal holes of various sections are combined with each other, and in the upper part of the carrier pipe is equipped with a head for a load gripping device. Known technical solution allows you to place the maximum number of fuel assemblies of reactors of the type VVER-1000/1200 in a container case.

(RU 2642853, G21F 5/00, published 01/29/2018)

The disadvantage of this container is a very complex welded-prefabricated structure of dissimilar metal materials and, accordingly, the high complexity of manufacturing, operation and repair.

The objective and technical result of the invention is to ensure that the container contains the maximum number of fuel assemblies of WWER reactors, as well as the ease of manufacture of the container with a high level of neutron protection and heat removal.

The technical result is achieved by the fact that the container for transporting and storing spent fuel assemblies of the WWER type reactor contains a central support pipe placed on a support and sections mounted with a coaxial pipe with vertical hexagonal holes, each section being made of gadolinium alloyed high-strength cast iron with spherical graphite in the form of solid a cylinder with a central hole and with a wall thickness between the hexagonal holes of 50-55 mm.

The technical result is also achieved by the fact that in the upper part of the carrier pipe is equipped with a head under the load gripping device

According to the invention, the new container design has the following advantages:

- due to the cast structure of the sections provides a more efficient removal of thermal energy from the fuel assemblies to the housing and to the surrounding space;

- the use of solid cast iron sections with spherical graphite instead of welded prefabricated from dissimilar materials significantly simplifies the design of the container as a whole and its operational reliability;

- solid sections of gadolinium alloyed cast iron with spherical graphite with a wall thickness of 50-55 mm provide a high neutron-absorbing capacity of the container.

In FIG. 1 shows the design of a container for accommodating spent fuel assemblies of a VVER-1000/1200 reactor; in FIG. 2 - solid section of the container.

The container is a structure containing a central bearing pipe (1) made of stainless steel, placed on a support (2), solid-cast sections (3) made of gadolinium alloyed cast iron in spherical graphite, equipped with one central hole and vertical hexagonal holes (4) to accommodate spent fuel assemblies. At the same time, sections (3) are mounted on the support (2) of a coaxially supporting pipe with a combination of hexagonal holes along the entire height of the container. In the upper part, the support pipe (1) is equipped with a head (5) for a load gripping device.

Each section is a cylindrical casting (Fig. 2) with cast hexagonal holes with a wall thickness between holes of 50-55 mm, providing after assembly the placement of fuel assemblies in them with the necessary gaps. The optimal wall thickness between the holes a = 50-55 mm provides both a high level of absorption of neutron radiation from the assemblies and the highest possible level of heat transfer from the assemblies to the container body.

For section casting, it is possible to use the known radiation-resistant nodular cast iron containing carbon, silicon, manganese, nickel, copper, chromium, vanadium, magnesium, calcium, cerium, boron, barium, gadolinium, sulfur, phosphorus, cobalt and iron with the following component ratios wt. %: carbon 2.5-3.5; silicon 1.8-2.6; manganese 1.5-2.5; nickel 9.4-11.0; copper 6.0-7.0; chrome 0.06-0.10; vanadium 0.06-0.10; magnesium 0.03-0.05; calcium 0.01-0.03; cerium 0.01-0.03; boron 0.006-0.10; barium 0.01-0.15; gadolinium 0.6-3.0; sulfur 0.004-0.01; phosphorus 0.004-0.04; cobalt 0.002-0.12, the rest is iron.

However, the most appropriate is the use of high-strength cast iron with spherical graphite, providing more accurate casting of the hexagonal holes of the section. The specified high-strength nodular cast iron contains carbon, silicon, manganese, nickel, magnesium, gadolinium, phosphorus, sulfur and iron in the following ratio, wt. %: carbon 3.6-3.9; silicon 2.0-2.4; manganese 0.15-0.35; nickel 0.5-1.0; magnesium 0.05-0.09; gadolinium 0.25-0.50; phosphorus 0.01-0.03; sulfur 0.010-0.015; iron the rest.

Iron smelting and casting are carried out by standard methods. After casting, the sections are subjected to the necessary machining with the formation of threaded elements between themselves and the support.

Assembly of the container is as follows.

The one-piece machined cylindrical sections are successively installed from bottom to top on top of each other on a support (2) of a coaxially supporting pipe (1) with a combination of hexagonal holes of the sections along the entire height of the container. The sections are fastened together with studs made of stainless steel (not shown) or otherwise. The container assembled as described above is placed in the cavity of the container cover with a predetermined radial clearance to provide the required heat-conducting contact between the outer surface of the container and the inner surface of the container cover in a loaded state.

Claims (2)

1. A container for transporting and storing spent fuel assemblies of a WWER type reactor, comprising a central support pipe mounted on a support and coaxially mounted sections with vertical hexagonal holes, characterized in that each section is made of gadolinium alloyed high-strength cast iron with spherical graphite in the form of a solid cylinder with a central hole and with a wall thickness between hexagonal holes of 50-55 mm. 2. The container according to claim 1, characterized in that in the upper part of the carrier pipe is equipped with a head under the load gripping device.

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