Induced nuclear reactions: processes – systems – and elements – With control of reactor – By coolant flow
Reexamination Certificate
2001-04-09
2003-08-12
Carone, Michael J. (Department: 3641)
Induced nuclear reactions: processes, systems, and elements
With control of reactor
By coolant flow
C376S211000
Reexamination Certificate
active
06606366
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates to a nuclear power plant, and more specifically to a nuclear power plant capable of adjusting the position of a turbine by-pass valve based on the steam pressure generated in a nuclear reactor.
2. Description of the Related Art
FIG. 1
is a diagram showing a main steam system and a turbine by-pass system of a nuclear power plant.
A main steam supply system
01
is constituted such that steam generated in a nuclear reactor
1
is supplied to a steam turbine
8
via a main steam header
4
, a main steam stop valve
5
, and a main steam control valve (CV)
6
, respectively.
Specifically, steam from the nuclear reactor
1
is supplied to the main steam header
4
disposed outside a primary containment vessel
3
. The steam thus supplied to main steam header
4
then flows to the steam turbine
8
via the main steam stop valve
5
and the main steam control valve
6
. The main steam stop valve
5
isolates steam in the steam turbine
8
in case of stopping operation thereof, and the main steam control valve
6
adjusts the flow rate of steam to the steam turbine
8
. The steam from the nuclear reactor
1
rotates the steam turbine
8
, and a generator
9
connected directly to the steam turbine
8
generates electric power.
Steam that passes through the steam turbine
8
is then guided to a condenser
10
. Cooling water such as seawater enters the condenser
10
, and a heat exchange is made between the cooling water and the steam. Steam thus cooled is condensed to water and is circulated back to the nuclear reactor
1
.
A turbine by-pass steam supply system
02
, independent from the main steam system
01
, branches from the main steam header
4
. The turbine by-pass system
02
guides steam from the main steam header
4
to the condenser
10
via the turbine by-pass valve.
In a regular operation mode of the nuclear power plant, steam pressure generated in the nuclear reactor
1
, which is specifically pressure on the main steam header
4
detected by a main steam pressure detector
2
or pressure detected by a reactor dome pressure detector
11
, is adjusted by the main steam control valve
6
in order to meet a predetermined pressure value. The turbine by-pass valve
7
is fully opened in this situation. Meanwhile, when the nuclear power plant is in a starting or a stopping mode, or when an accident happens to a power supply system, the position of the main steam control valve
6
restricted. In this situation, the turbine by-pass valve
7
adjusts the main steam pressure
2
in the main steam header
4
.
Further, when a load is deprived, such as load isolation of the generator
9
and turbine trip, turbine-trip, or the like, both the main steam stop valve
5
and the main steam control valve
6
are closed rapidly, stopping the steam flow to the steam turbine
8
. This causes an increase in the pressure in the nuclear reactor
1
and of the main steam. To relax this pressure, the turbine by-pass valve
7
rapidly opens and the main steam is bypassed to the condenser
10
.
A conventional turbine controller for the nuclear power plant is explained referring to
FIG. 2. A
regulating controller in the steam turbine controller
12
controls the position of the main steam control valve
5
and the turbine by-pass valve
7
.
Main steam pressure signals are output signals from the main steam pressure detector
2
connected to the main steam header
4
and enter the steam turbine controller
12
. The signals thus entered are compared to the predetermined pressure value in a main steam pressure setter
23
, and a pressure deviation signal
29
is carried out by a first pressure deviation calculating unit
24
. Here, the pressure deviation signal
29
is entered into a pressure control calculating unit
25
, and a pressure control signal
30
, which is proportional to the pressure deviation signal
29
, is input into a first low value selector
18
as a pressure control signal
30
.
In the first low value selector
18
, the pressure control signal
30
is compared to a velocity/load control signal from a speed/load control calculating unit
15
, a load limit signal from a load limiter
16
, and a maximum flow rate limit signal from a maximum discharge restriction unit
17
, respectively. After the comparison, the first low value selector
18
chooses a minimum signal from among those signals and outputs the minimum signal as a valve position demand signal
26
of the main steam control valve
6
.
Further, the pressure control signal
30
carried out by the pressure control calculating unit
25
and the valve position demand signal
26
of the main steam control valve
6
obtained by the first low value selector
18
are input into a first deviation calculating unit
20
, and a deviation signal is calculated. The maximum discharge restriction signal carried out by the maximum discharge restriction unit
17
and the valve position demand signal
26
of the main steam control valve
6
obtained by the first low value selector
18
are input into a second deviation calculating unit
21
, and a deviation signal is calculated.
The deviation signals from the first deviation calculating unit
20
and the second deviation calculating unit
21
are input into a second low value selector
22
. These deviations are then compared therein, and the lower signal is chosen as a valve position demand signal
31
of the turbine by-pass valve
7
.
The turbine by-pass valve position demand signal
31
output from the regulating controller
13
and the valve position demand signal
26
are entered into a valve position control unit
32
having an amplifier, and a deviation signal carried out by the valve position control unit
32
is entered into a servo valve
33
. The servo valve
33
controls the valve position of the turbine by-pass valve
7
to a value required by the steam turbine controller
12
, by adjusting the amount of oil in an oil cylinder
38
that operates turbine by-pass valve
7
.
The oil cylinder
38
connects a fast acting solenoid valve
37
; the fast acting solenoid valve
37
accepts a fast open acting demand to turbine by-pass valve
36
and makes turbine by-pass valve
7
realize a rapid valve-opening operation in an emergency as well as in a performance test. In the regular operation mode, the fast open acting demand to turbine by-pass valve
36
is not generated, and therefore, the oil cylinder
38
is controlled only by turbine by-pass valve
7
. However, if the fast open acting demand to turbine by-pass valve
36
is generated due to detection of a power load unbalance such as a load isolation, the turbine by-pass valve
7
is fully opened regardless of the control signal from the servo valve
33
. Usually, a plurality of turbine by-pass valves
7
are equipped in a plant, however, only the valve which accepted the fast open acting demand to turbine by-pass valve
36
can be fully opened.
For reliability reasons, the main steam pressure detector
2
, the regulating controller
13
and the like are multiplexed. Therefore,
FIG. 2
shows the case where the triplex main steam pressure detectors
2
and the triplex regulating controller
13
are arranged. The medium value among the output signal from the triplex main steam pressure detectors
2
are chosen by the first medium value selector
27
, and each of the triplex regulating controllers
13
operates the pressure control signal
30
and the valve position control unit
32
for the plant control.
Further, the number of turbine by-pass valves
7
varies from each nuclear power plant. The valve position control unit
32
, the servo valve
33
, the fast acting solenoid valve
37
, and the oil cylinder
38
are identical in each turbine by-pass valve
7
, and therefore, only one turbine by-pass valve
7
and the peripherals are illustrated in FIG.
2
.
In a nuclear power plant having multiplexed regulating controllers
13
, if one regulating controller
13
has a problem or an unusual condition in its regular operating mode, the other regulating controllers can compens
Koiwai Masatoshi
Yokota Yutaka
Carone Michael J.
Foley & Lardner
Matz Daniel
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