The 12 The 12 self-powered detectors fingers contain each 6 self-powered detectors
C. Aeroball system for monitoring power distribution in the reactor core. The fundamental function of that movable nuclear fixed
6.4.1. The flux map is utilized to obtain the axial distribution of the neutron power of the hot channel of each fuel assembly (3D image of
the power distribution).
the power distribution).
From the mean axial distributions, it is possible to determine the the From the mean axial distributions, it is possible to determine the the
following core parameters:
following core parameters:
Axial neutron power of the hot channel of each fuel assembly and the FQ Axial neutron power of the hot channel of each fuel assembly and the FQ
(hot point factor) maximal value of the core;
(hot point factor) maximal value of the core;
The mean axial distribution of the neutron power of the core;
The mean axial distribution of the neutron power of the core;
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The integrated power along the fuel assembly and the hot channel, which The integrated power along the fuel assembly and the hot channel, which allows to deduct the enthalpy rise of each fuel assembly and the FΔH allows to deduct the enthalpy rise of each fuel assembly and the FΔH maximal value of the reactor core, utilized to calculate the minimal maximal value of the reactor core, utilized to calculate the minimal
DNBR by combining with the operating thermal-hydraulics;
DNBR by combining with the operating thermal-hydraulics;
The power ratio between the two core quadrants.
The power ratio between the two core quadrants.
The core parameters are utilized to accomplish the following tasks:
The core parameters are utilized to accomplish the following tasks:
* Verify the conformity of the reactor core at the first start-up and during
* Verify the conformity of the reactor core at the first start-up and during the reloading;
the reloading;
* Scaling of the fixed in-core instrumentation;
* Scaling of the fixed in-core instrumentation;
* Justify the uncertainties of the measurements which are taken into
* Justify the uncertainties of the measurements which are taken into account in the surveillance system;
account in the surveillance system;
* Follow-up the burn-up of the fuel assembly;
* Follow-up the burn-up of the fuel assembly;
* Effectuate researches and establish diagnostics in case of operating in
* Effectuate researches and establish diagnostics in case of operating in particular and abnormal conditions.
particular and abnormal conditions.
THERMAL-HYDRAULIC IN NUCLEAR REACTOR
An unique in-core monitoring system referred to as the computerized An unique in-core monitoring system referred to as the computerized aeroball system is used in PWR. In the aeroball system, probes aeroball system is used in PWR. In the aeroball system, probes containing neutron sensitive isotopes are introduced into the reactor containing neutron sensitive isotopes are introduced into the reactor core and are subsequently activated. As shown in the following figure, core and are subsequently activated. As shown in the following figure, the probes are columns of 1.7 mm diameter steel balls. The ball the probes are columns of 1.7 mm diameter steel balls. The ball columns are piped into SS steel tubes incorporated in selected FA columns are piped into SS steel tubes incorporated in selected FA throughout the reactor core. The length of the columns corresponds to throughout the reactor core. The length of the columns corresponds to
the height of the core.
the height of the core.
The aeroball system permits:
The aeroball system permits:
* to take into account in the same manner the different zones of the core
* to take into account in the same manner the different zones of the core in the map of the flux (type of fuel assembly, local effects of control in the map of the flux (type of fuel assembly, local effects of control rods, radial surface). Thus when the measured fuel assembly rods, radial surface). Thus when the measured fuel assembly represent in the unique eighth of the core, nearly all the fuel assembly represent in the unique eighth of the core, nearly all the fuel assembly (except the ones located in the positions of the control rods clusters) (except the ones located in the positions of the control rods clusters)
are instrumented;
are instrumented;
* to realize the measurements in the the symmetrical fuel assemblies
* to realize the measurements in the the symmetrical fuel assemblies (with regard to the quarter of the core) in the different zones of the (with regard to the quarter of the core) in the different zones of the
core, core, ..
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to realize measurements uniformly distributed along the fissile length of to realize measurements uniformly distributed along the fissile length of
the fuel assembly.
the fuel assembly.
Vanadium is added to the balls as a neutron flux indicator through 225 s Vanadium is added to the balls as a neutron flux indicator through 225 s
half-life
half-life 5252V activity induced by neutron capture in V activity induced by neutron capture in 5151V. The activation V. The activation of 51V and its characteristics are summarized in the above table.
of 51V and its characteristics are summarized in the above table.
The activity of the probes is measured, following removal from the core, The activity of the probes is measured, following removal from the core, by using a set of silicon detectors. The count rate from each silicon by using a set of silicon detectors. The count rate from each silicon detector is proportional to the relative integrated thermal neutron flux detector is proportional to the relative integrated thermal neutron flux at the point where the corresponding aeroball was located during the at the point where the corresponding aeroball was located during the activation process. From many such measurements, the power density activation process. From many such measurements, the power density
distribution of the reactor core can be determined.
distribution of the reactor core can be determined.
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Figure XVIII.2C.1 : AMS system location Figure XVIII.2C.1 : AMS system location
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Figure XVIII.2C.2 : Instrumentation Lance & Nozzle arrangement Figure XVIII.2C.2 : Instrumentation Lance & Nozzle arrangement
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Figure XVIII.2C.3: Aeroball system for continous activation Figure XVIII.2C.3: Aeroball system for continous activation
measurements of the neutron distribution in a reactor core.
measurements of the neutron distribution in a reactor core.
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Figure XVIII.2C.4: Aeroball system for continous activation Figure XVIII.2C.4: Aeroball system for continous activation
measurements & pneumatic system measurements & pneumatic system
THERMAL-HYDRAULIC IN NUCLEAR REACTOR
Figure XVIII.2C.5: Aeroball system for continous activation Figure XVIII.2C.5: Aeroball system for continous activation
measurements & pneumatic system measurements & pneumatic system
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Figure XVIII.C.6: Aeroball system for continous activation measurements Figure XVIII.C.6: Aeroball system for continous activation measurements
& pneumatic system
& pneumatic system
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Figure XVIII.2C.7: Measuring ranges of ex-core instrumentation Figure XVIII.2C.7: Measuring ranges of ex-core instrumentation
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Figure XVIII.2C.8: Aeroball system.
Figure XVIII.2C.8: Aeroball system.
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Figure XVIII.2C.9: Detail aeroball system & SPND probes.
Figure XVIII.2C.9: Detail aeroball system & SPND probes.
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Figure XVIII.2C.10: Boron measurement system Figure XVIII.2C.10: Boron measurement system
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Figure XVIII.2C.11: Boron on line measurement Figure XVIII.2C.11: Boron on line measurement
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Figure XVIII.2C.12: Reactor pressure vessel level measurement Figure XVIII.2C.12: Reactor pressure vessel level measurement
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Figure XVIII.2C.13: Axial locations of SPNDs Figure XVIII.2C.13: Axial locations of SPNDs
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Figure XVIII.2C.14: Schematic of SNPDs detector Figure XVIII.2C.14: Schematic of SNPDs detector
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Figure XVIII.2C.14: Details of Aeroball & SNPDs detector Figure XVIII.2C.14: Details of Aeroball & SNPDs detector
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Figure XVIII.2C.15: Time schedule of AMS measuring process Figure XVIII.2C.15: Time schedule of AMS measuring process
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Figure XVIII.2C.16: AMS measurement table Figure XVIII.2C.16: AMS measurement table
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Figure XVIII.2C.17: AMS measurement table used in KONVOI NPP.
Figure XVIII.2C.17: AMS measurement table used in KONVOI NPP.
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XIX. Protection chains ΔTe & ΔTOP XIX. Protection chains ΔTe & ΔTOP
The protection systems must activate the scram since the core The protection systems must activate the scram since the core
parameters are out of the protection diagramm preveously defined.
parameters are out of the protection diagramm preveously defined.
This leads to the two chains of protections:
This leads to the two chains of protections:
- the chain of
- the chain of ΔΔTte high temperature;Tte high temperature;
- the chain of
- the chain of ΔΔTop (over-power) Top (over-power)
On which the thresholds are elaborated from primary parameters. The On which the thresholds are elaborated from primary parameters. The determination of these chains has been done in five successive determination of these chains has been done in five successive
stages:
stages: