Induced nuclear reactions: processes – systems – and elements – Testing – sensing – measuring – or detecting a fission reactor... – Flux monitoring
Reexamination Certificate
2002-03-27
2004-12-28
Carone, Michael J. (Department: 3641)
Induced nuclear reactions: processes, systems, and elements
Testing, sensing, measuring, or detecting a fission reactor...
Flux monitoring
C376S245000, C376S254000, C376S259000, C250S336100, C250S339020, C250S374000, C250S388000
Reexamination Certificate
active
06836523
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2001-93306 filed on Mar. 28, 2001, and No. 2002-46788 filed on Feb. 22, 2002, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a device and a method for radiation measurement, applied to monitor the radiation in an extensive range for improving resistance to noises in a digital signal processing.
2. Description of the Related Art
As far as radiation measurement is concerned, if wide range radiation is measured, then the pulse measurement method and the Campbell measurement method are often used together.
Generally, the pulse measurement method counts the pulse number of a pulse signal from a radiation sensor, but if the pulses overlap and it cannot count by the pulse measurement method, the Campbell measurement method is performed.
For example, from six to ten start-up range neutron monitor sensors (SRNM sensors) and from one hundred to two hundred local power range monitor sensors (LPRM sensors) are installed inside of a reactor pressure vessel containing nuclear reactor core to monitor nuclear reactor power. A start-up range neutron monitor and a power range neutron monitor measure outputs of the SRNM sensors and the LPRM sensors, respectively, to monitor the nuclear reactor power in a monitoring range of about eleven figures.
In this composition, the start-up range neutron monitor is used to count the pulse number of an output signal of the SRNM sensor in order to monitor relatively low reactor output, that is, the output is in from 10
−9
% to 10
−4
% of effective full power of the reactor. This is henceforth called the pulse measurement method.
On the other hand, the Campbell measurement method, that is, the measuring of fluctuation power generated due to overlapping of the pulse outputted from the sensor, is used in order to monitor relatively high reactor output, that is, the output is in from 10
−5
% to 10% of the effective full power of the reactor.
Hereafter, a conventional technical example of the pulse measurement method and the Campbell measurement method in a nuclear reactor start-up monitoring system, which is disclosed in Japanese Patent Disclosure (koukai) No. 2000-162366, which is equivalent to U.S. Pat. No. 6,181,761, is explained with reference to FIG.
18
.
The nuclear reactor start-up monitoring system shown in
FIG. 18
is composed of an SRNM sensor
1
for outputting an electric signal containing pulse components corresponding to the number of neutrons in response to neutrons generated in the nuclear reactor, an analog preamplifier
2
, an A/D (analog-to-digital) converter
3
, and a pulse counter
23
, an integration counter
24
, a power calculator
25
, an arithmetic average calculator
26
, and a reactor power monitoring system
27
. The analog preamplifier
2
amplifies the electric signal having pulse components outputted from the SRNM sensor
1
to regularize the electric signal, and the A/D converter
3
converts an analog signal outputted from the preamplifier
2
to digital data sampled at intervals which are shorter than a pulse width of the pulse included in electric signal outputted from the SRNM sensor
1
. The pulse counter (PC)
23
counts a number of pulses in the sampled data outputted from the A/D converter
3
and converts the number of the pulse to an output level value contained in relatively low range power of the nuclear reactor, and the integration counter
24
adds the sampled valve outputted from the A/D converter
3
to raise the measurement accuracy. The power calculator
25
calculates a power by squaring the added value of the integration counter
24
, and the arithmetic average calculator
26
averages the power calculated by the power calculator
25
. The reactor power monitoring system
27
continuously monitors the output at the start-up of the nuclear reactor based on the counter result of the pulse counter
23
and the calculation result of the arithmetic average calculator
26
.
In the digital reactor start-up monitoring system of such a composition, the preamplifier
2
amplifies and regularizes a shape of a pulse included in the electric signal outputted from SRNM sensor
1
, and the A/D converter
3
samples the amplified and regularized pulse at high speed and calculates the pulse by using one or more logical operations. Also, the pulse counter
23
counts the calculation results outputted from the A/D converter
3
as an output pulse of the sensor if each calculation result outputted from the A/D converter
3
is in a corresponding predetermined range, respectively.
On the other hand, the same sampled value is added in the integration counter
24
to lower into a level of a sampling rating required for the Campbell measurement method and to earn a dynamic range for improving the number of equivalent bits. The power calculator
25
adds square values of the results after performing band-pass-filter process for the results, and the arithmetic average calculator
26
averages the results calculated by the power calculator
25
and computes the Campbell output value. The pulse enumerated data and the Campbell output value are estimated by the nuclear reactor output evaluation unit
27
and are displayed as a nuclear reactor output.
In this composition, calculation limited to the sensor-outputting pulse can be carried out with excluding noises having long pulse widths by discrimination based on information of not only a pulse height of a pulse but a pulse width by the pulse calculator
23
.
That is, in the reactor start-up monitoring system of
FIG. 18
, for example, the output signal of the SRNM sensor
1
containing a pulse with the pulse width of 100 nanoseconds is sampled at intervals of 25 nanoseconds.
Four sampled-data, from data No. k-
3
to data No. k, denoted as S(k-
3
), S(k-
2
), S(k-
1
), and S(k) in order, respectively, which correspond to a pulse width, are used to calculation described below, as S(k-
3
) is a sampled value at a rise point of a pulse, S(k) is a sampled value at a fall point of the pulse, and two sampled data S(k-
1
), S(k-
2
) are in between S(k-
3
) and S(k). It considers a result Out(k) of this calculation as an index of pulse discrimination, and as a result, the pulse is counted as a neutron pulse if it is in a range of predetermined level.
Out(
k
)={
b*S
(
k
-
2
)+
c*S
(
k
-
1
)}−{
a*S
(
k
-
3
)+
d*S
(
k
)} (1),
where a, b, c and d are non-zero constants.
By this calculation, it becomes possible to calculate only signals having almost similar pulse widths as that of the output pulse of the SRNM sensor
1
. That is, even if a large surge-like noise becomes overlapped on a signal pulse, it can count measured value exactly by deducting the ground level of the pulse.
In addition, by setting two or more indices such as the Out(k) for detecting a case corresponding to such a sensor pulse form as mentioned above and using AND logic among these indices, this discrimination performance can be improved further.
Thus, even if a surge-like noise with a pulse width of several microseconds overlaps, and is supposed to be guided into a pulse in an electric signal outputted from the SRNM sensor most easily, the surge-like noise can be removed nearly completely and a limited calculation of sensor pulses with a pulse width of about 100 nanoseconds can be performed.
On the other hand, in the Campbell measurement method, the power calculator
25
restricts a frequency band and calculates an average of square values of the sampled data. In this composition, since the frequency band can be set up by software programming, if a noise is in a certain frequency equivalent to a measurement band, changing the measurement band on the software programming can reduce guidance of the noise.
However, there are several subjects described below in the nuclear reactor start-up monitoring system acco
Izumi Mikio
Maekawa Tatsuyuki
Tarumi Teruji
Yamada Masafumi
Carone Michael J.
Foley & Lardner LLP
Kabushiki Kaisha Toshiba
Richardson John
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