Induced nuclear reactions: processes – systems – and elements – Reactor protection or damage prevention – Pressure suppression and relief
Reexamination Certificate
1999-03-31
2001-01-09
Jordan, Charles T. (Department: 3641)
Induced nuclear reactions: processes, systems, and elements
Reactor protection or damage prevention
Pressure suppression and relief
C376S293000, C376S461000
Reexamination Certificate
active
06173027
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a primary containment vessel particularly of a boiling water reactor.
In conventional boiling water reactors (BWR), an advanced boiling water reactor (ABWR) has been well known as a latest reactor. A reinforced concrete primary containment vessel (RCCV) of the ABWR will be described below with reference to the accompanying drawings.
FIG. 15
is a schematically sectional view showing a conventional ABWR. As shown in
FIG. 15
, a primary containment vessel
1
is provided with a reactor pressure vessel
4
which is supported on a support skirt portion
3
by means of a substantially hollow cylindrical reactor pressure vessel (RPV) pedestal
2
at the middle portion in the primary containment vessel. An outer peripheral side of the reactor pressure vessel
4
is surrounded with a hollow cylindrical outer peripheral concrete wall
5
. Each lower end portion of the outer peripheral concrete wall
5
and the RPV pedestal
2
is supported on a mat concrete wall
6
. The outer peripheral concrete wall
5
and the RPV pedestal
2
are joined together by means of a horizontal wall
7
at the substantially central position in a vertical direction in an illustrated state of the RPV pedestal
2
.
In the reactor pressure vessel
4
, an upper side from the support skirt portion
3
is surrounded by an upper dry well
8
which is a space defined (surrounded) by the outer peripheral concrete wall
5
, the horizontal wall
7
and the RPV pedestal
2
. On the other hand, in the reactor pressure vessel
4
, a lower side from the support skirt portion
3
is surrounded with a lower dry well
9
which is a space defined (surrounded) by the mat concrete wall
6
and the RPV pedestal
2
. The lower dry well
9
includes a reactor water recirculation pump and a control rod drive mechanism, which are not shown. Further, the lower dry well
9
is provided with a wet well
10
which is a space surrounded by the outer peripheral concrete wall
5
, the mat concrete wall
6
, the horizontal wall
7
and the RPV pedestal
2
, at the outer peripheral side thereof. The wet well
10
is provided with a suppression pool or chamber
11
in which water is stored, at a half of the lower side.
The RPV pedestal
2
is provided with a communicating hole
12
. The communicating hole
12
functions as a gas passageway between the upper dry well
8
and the lower dry well
9
, and extends from the lower dry well
9
so as to communicate a heat exchanger cooling pipe of a reactor water recirculation pump, an electric cable of the control rod drive mechanism, an air conditioning duct, which are included in the lower dry well
9
and are not shown, with the upper dry well
8
. These pipe, electric cable duct and the like are connected to the outside of the primary containment vessel via a penetration member (not shown) from the upper dry well
8
.
Further, the RPV pedestal
2
is provided with a vertical vent pipe
13
, which is opened to the lower dry well
9
side, at a half portion on the lower side thereof. The vertical vent pipe
13
is connected to a plurality of horizontal vent pipes
14
at the lower end side thereof. These horizontal vent pipes
14
are opened to water of the suppression pool
11
. The suppression pool
11
is stored with water capable of safely absorbing a thermal energy radiated from the reactor pressure vessel
4
when an assumed accident such as a main steam pipe breakdown accident happens.
The primary containment vessel
1
is provided with a passageway which penetrates through the outer peripheral concrete wall
5
, the wet well
10
and the RPV pedestal
2
, and communicates the outside of the primary containment vessel
1
with the lower dry well
9
. The passageway includes an equipment carrying in and out passageway
15
for carrying in and out equipments included in the lower dry well
9
, and a personnel passageway
16
for workers for coming in the lower dry well
9
from the outside of the primary containment vessel
1
so that the workers (personnel) do work in the lower dry well
9
. These equipment carrying in and out passageway
15
and personnel passageway
16
are provided with a scram pipe of the control rod drive mechanism (not shown) from the lower dry well
9
.
FIG. 16
is a cross sectional view taken along the line XVI—XVI of FIG.
15
. As shown in
FIG. 16
, the primary containment vessel
1
is provided with the upper dry well
8
inside the outer peripheral concrete wall
5
having an ring shape in its cross section. The upper dry well
8
becomes a state of being filled with an inert gas such as nitrogen in order to prevent an explosion of a fuel assembly when a main steam pipe breakdown accident or the like happens. An inner peripheral side of the outer peripheral concrete wall
5
is provided with the RPV pedestal
2
which is surrounded by the upper dry well
8
and has a ring shape in its cross section. Ten (10), in total, communicating holes
12
are formed along the outer periphery of the RPV pedestal
2
.
FIG. 17
is a cross sectional view taken along the line XVII—XVII of FIG.
15
. As shown in
FIG. 17
, the primary containment vessel
1
is provided with the wet well
10
inside the outer peripheral concrete wall
5
having an ring shape in its cross section. An inner peripheral side of the outer peripheral concrete wall
5
is provided with the RPV pedestal
2
which is surrounded by the wet well
10
and has a ring shape in its cross section. The RPV pedestal
2
is formed with the totaled ten (10) vertical vent pipes
13
having a circular shape in a cross section thereof. The lower dry well
9
is formed inside of the RPV pedestal
2
.
Further, the primary containment vessel
1
is provided with an equipment carrying in and out passageway
15
which communicates with the outside of the primary containment vessel
1
and the lower dry well
9
and carries in and out equipments included in the lower dry well
9
, and a personnel passageway
16
which is a passageway for coming in the lower dry well
9
so that the workers do work in the lower dry well
9
.
In the conventional primary containment vessel constructed as described above, in the case where an accident such as a main pipe breakdown accident happens in the upper dry well
8
, the upper dry well
8
and the lower dry well
9
communicate with each other, and for this reason, a steam pressure of the upper dry well
8
and the lower dry well
9
rises up. Then, when the steam pressure becomes a predetermined pressure or more, a high pressure steam is jetted into the water stored in the suppression pool
11
via the vertical vent pipe
13
communicating with the lower dry well
9
and the horizontal vent pipes
14
. The jetted high pressure steam is condensed by the water stored in the suppression pool
11
, so that an atmospheric pressure of the upper dry well
8
and the lower dry well
9
can be reduced.
Moreover, in the case where an accident such as a small-diameter pipe breakdown accident happens in the lower dry well
9
, the upper dry well
8
and the lower dry well
9
communicate with each other. Because of this reason, a steam pressure of the upper dry well
8
and the lower dry well
9
rises up. Then, when the steam pressure becomes a predetermined pressure or more, a high pressure steam is jetted into the water stored in the suppression pool
11
via the vertical vent pipe
13
communicating with the lower dry well
9
and the horizontal vent pipes
14
. The jetted high pressure steam is condensed by the water stored in the suppression pool
11
, so that an atmospheric pressure of the upper dry well
8
and the lower dry well
9
can be reduced.
An inner-diameter dimension of the primary containment vessel
1
is determined in view of an outer diameter of the reactor pressure vessel
4
, an arrangement space of a main steam pipe isolation valve (not shown) connecting to the reactor pressure vessel
4
, etc.
Further, a height dimension of the reactor container
1
is determined in view of a height dimension of the reactor pressu
Asano Akiro
Hirono Shuji
Saito Takashi
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Jordan Charles T.
Kabushiki Kaisha Toshiba
Mun Kyongtaek K.
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