DE8614813U1 - Component for wet disassembly of a reactor pressure vessel - Google Patents

Description

Kraftwerk Union Aktiengesellschaft VPA 86 G 6037 DE

<_J3construction element for wet disassembly of a reactor pressure vessel 5

The innovation concerns a component for the wet disassembly of a reactor pressure vessel.

The dismantling and crushing of a reactor pressure vessel in nuclear power plants is made more difficult by contamination and activation as a result of neutron bombardment. The resulting radiation exposure of the personnel can be kept to a minimum by shortening the time the personnel spend in the area, by providing good shielding against radiation and by remotely controlling the equipment.

When removing radioactive components, all three of the above criteria are combined accordingly. The removal and crushing of a reactor pressure vessel can be carried out dry in air or with water cover.

During remote-controlled dry dismantling, which is carried out under appropriate shielding measures using thick shielding plates, difficulties arise in removing the radioactive parts due to the poor accessibility. Furthermore, if there are disruptions during dismantling, additional difficulties arise due to the poor accessibility.

Wet dismantling makes use of the good shielding effect of water. The reactor pit is sealed and flooded. Problems can arise from leaks in the concrete and, if present, the liner.

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After many years of operation, cracks in the concrete or biological shield are possible, which can lead to the spread of contamination and thus a greatly increased amount of radioactive waste. 5

The innovation is based on the task of specifying a component for dismantling a reactor pressure vessel that enables wet dismantling using simple means while avoiding the spread of contamination into the biological shield.

This object is achieved according to the invention in that the component is designed as an enclosing pipe in order to arrange it between the reactor pressure vessel and the concrete wall of the reactor pit as a flood basin. The outer diameter of the enclosing pipe is preferably sized so that the air gap to the reactor pit is as small as possible.

The innovation is shown in the drawing. It shows:

Fig. 1 a sectional view of an arrangement for wet dismantling of a reactor pressure vessel, Fig. 2 a reactor pressure vessel before dismantling

with replacement support and sealing base already attached,
Fig. 3 an arrangement for a reactor pit formed by an enclosing pipe, which serves as a flood basin and

Fig. 4 shows a section through another reactor pressure vessel with a containment pipe, which is tightly connected to the lower reactor area.
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VPA 86 G 60 3 7 l£ In Fig. i, a reactor pressure vessel 1 is arranged within a biological shield 2, which forms the reactor pit (concrete shielding). Below the reactor pressure vessel, at the bottom of the shield 2, there is a base plate 3, e.g. made of steel.

For wet dismantling of the reactor pressure vessel 1, it is provided with replacement supports 4 at the bottom. The upper supports and all parts, in particular lines Ic (Fig. 2)j that lead into the reactor pressure vessel 1,

&pgr; oj. uci &igr; ei &igr; ui Ci Ii &igr;» , cucniaiia uxc &igr; J. oyi\uiist i unbxi/iicii J. &igr;&khgr;&igr;&igr;&igr; upper region of the reactor pressure vessel 1. Between the reactor pressure vessel 1 and the biological shield 2, an enclosing pipe 5 is then pulled in (Fig. 1), the diameter of which is adapted to the diameter of a base plate 3 introduced into the reactor pit, which can also be designed as a tub. After the enclosing pipe 5, which is provided with a manhole 5b, has been introduced, it is tightly connected to the base plate 3 installed below the reactor pressure vessel 1, for example by a weld seam 3a. At the top, the enclosing pipe 5 is connected via the flange 5a to the flood basin 6 by means of a seal 7.

By flooding the containment tube 5, the reactor pressure vessel is also under water from the outside and can thus be separated into suitable cutting pieces.

A sequence of work steps for dismantling and crushing the reactor pressure vessel can be carried out, for example, in the following order (fuel elements and core internals are removed, the reactor and the flood chamber are flooded):

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A) Lowering the water level until it is just below the lower edge of the flange 5a of the reactor pressure vessel (Fig. 2);

B) Attaching a seal Ib (Fig. 1) to the inside of the coolant inlet and outlet nozzles and other auxiliary lines from the inside of the reactor pressure vessel 1;

C) Inserting and completing the base plate 3 beneath the reactor pressure vessel 1, installing the replacement supports 4 at the bottom of the reactor pit;

D) Removal of the seal IG (Fig. 2) between the flange of the reactor pressure vessel 1 and the flood chamber lining;

E) Separation of all reactor pressure vessel parts that hinder the installation of the containment tube (e.g. upper supports If and pipe nozzles lc);

F) Separating the non-highly radioactive reactor pressure vessel flange Ie (Fig. 2) in a dry state, e.g. by milling or arc sawing and lifting and removing;

G) Installation of the containment pipe 5 (Fig. 1);

H) Sealing the enclosing pipe 5 with the base plate 3, e.g. by welding;

I) possibly sealing the enclosing pipe 5 with the flood basin 6 by arranging a seal 7;

K) Flooding the containment pipe 5 up to near the upper end and

L) annular separation of the wall parts 8 of the reactor pressure vessel along the separation lines 9 and crushing and also of any thermal insulation still present 15 on the outside of the reactor.

The containment pipe 5 is used as a sealing element for the reactor pit 6 and has the following functions: 35

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a) Collection of water around the reactor pressure vessel. The water is used to shield the reactor pressure vessel and its cut parts and the biological shield (liner, reinforcing iron) from radiation.

5 used at the top;

b) collecting the secondary waste (impurities etc. which are filtered out) which is produced when the reactor pressure vessel is separated by the separation devices located in the bypass pipe;

10 c) Use as buffer storage for the reactor pressure

(d) support for the separation equipment necessary for dismantling the reactor pressure vessel;

e) The water serves as a coolant for the separating devices; 15 f) Avoidance of contamination in the

biological shield and

g) Shielding of the radiation from the reactor pit concrete (bio-(logical shield) in the event of the installation of a new

i;' reactor pressure vessel.

f Disconnecting the inlet and outlet nozzles as well as the

% reactor flange and reactor pressure vessel brackets

and the insertion of the enclosing pipe eyelet 5 is carried out from ;! locations which have only a low radiation dose.

I. Instead of the steel base plate 3, after installation

■! bring an enclosing pipe 5 with manhole 5b also

\ a tub-shaped base plate 3 in the form of a plastic

J Fabric lining 11, e.g. epoxy resin with glass fibre laminate

f 30 nat, are applied to the bottom of the reactor pit (Fig. 3). The plastic lining 11 is pulled up slightly at the lower end of the containment pipe 5 in order to achieve an appropriate seal.

35 Another possibility is shown in Fig. 4, which shows a boiling water reactor supported by a frame

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is carried. Here, the containment pipe 5 is arranged between the biological shield 2 | and the pressure vessel 1 after separating all parts that would hinder the installation of the containment pipe | 5. The containment pipe 5 | is tightly connected to the bottom Id | of the reactor pressure vessel 1 by welding or casting with sealing compound | 13, in particular rubber compound. The reactor pressure vessel 1 can then be dismantled mechanically or by using an arc saw underwater down to the bottom Id

The soil Id itself can be dry
be further dismantled because the activation is low.

This variant is possible wherever the container |

floor ld is supported. It is advisable to connect |

de.s containment tube 5 with the reactor pressure vessel 1 |

just above the pressure vessel support (frame 12)

assign. 1

The enclosing pipe can be shortened at the top after installation
of a new reactor will remain in the reactor pit.

5 Right to protection
4 figures

Claims (1)

r« ng ■·· t &bull; ro · · · * 7 yPfC'86 U'6&1 DE Protection claims 1. Component for wet separation of a reactor pressure vessel, from which the connections are removed and which is provided with supports at the bottom, characterized by an enclosing pipe (5) to be arranged between the reactor pressure vessel (1) and the reactor pit (6). 2. Component according to one of the preceding claims, characterized in that it has a flange (la) in order to connect it tightly at the top to the reactor pit (6). 3. Construction element according to claim 1, characterized in that it has a manhole (5b). I Il Ii It IMIl 14 ti· II«« I 111* i · i M * ' 1 * * llllll I i I