15
Chapter 9.1 Excore Core Neutron Monitoring System
Chapter 9.1
Excore Core Neutron Monitoring System
p
Objectives
1.List the purposes of the excore nuclear instrumentation system.
2.Explain the basic operation of the following excore neutron detectors and state the detectorexcore neutron detectors and state the detector type used in each range of the excore neutron monitoring system:
a. B10 proportional counter
b. Fission chamber
c. Uncompensated Ion chamber
Objectives (Continued)
3. Describe the following excore nuclear instrumentation system interfaces and interlocks:
a. Wide range logarithmic channel high voltage interlock
b. Wide range logarithmic channel and linear power g g prange safety channel overlap.
c. Wide range channel and linear power range safety channel reactor protection system (RPS) inputs.
d. Non-safety related linear power range safety channel interfaces.
Objectives (Continued)
4. Explain how the excore nuclear instrumenta-tion is capable of detecting both radial andaxial power distributions.
5 E plain ho the linear po er range safet5. Explain how the linear power range safetychannel is calibrated to indicate reactorthermal power.
6. List the power range linear control channeloutputs.
Purposes1. To monitor neutron flux from the source level to 200% of full power.
2. To provide indication in the control room of neutron power and the rate of change of neutron power.
3. To provide power level signals to the reactor regulating system (RRS)(RRS).
4. To provide power level signals and the rate of change of power signals to the reactor protection system (RPS).
5. To provide information on axial power distribution to the control room and the RPS.
WIDE RANGELOGARITHMIC
CHANNELS
CAMPBELLING CIRCUITLOG COUNT RATE CIRCUIT
% POWERCPS
B10 / FISSION CHAMBERSWITCH OVER
Figure 9.1-1 Typical Channel Flux Coverage With Detectors
B10 PROPORTIONALCOUNTER
FISSION CHAMBER
10 Channels4 Wide Range4 Linear Range2 Control Range
10-9
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
1 10 100
1 101
102
103
104
105
106
107
108
109
CHANNELS
LINEAR POWERRANGE SAFETY
ANDCONTROL CHANNELS
UIC
CONTINUOUSDISCHARGE
GEIGERMUELLER
LIMITEDPROPORTIONAL
PA
IRS
CO
LLE
CT
ED
RECOMBINATION
Figure 9.1-2 Ion Pairs Versus Applied Voltage
IONIZATION
APPLIED VOLTAGE
I II III IV V VI
ION
P
GAS AMPLIFICATION CURVE
PROPORTIONALCOUNTER
IONIZATIONCHAMBER
12A TC 11A TC
CHANNEL B
11 TH12 TH
Figure 9.1-3 Excore Detector Location
5
61
2 43
CHANNEL A
11B TC
98
CHANNEL C
WIDE RANGE LOG CHANNELS 3,5,9,11LINEAR POWER RANGE SAFETY CHANNELS 2,6,8,12
LINEAR POWER RANGE CONTROL CHANNELS4,7SPARE LOCATIONS1,10
12B TC
CHANNEL D
12
11
10
7
FILLING TUBEKOVAR-GLASS SEALS
BORON COATING
HV CONNECTOR
+
AFTER SEALING ANODE (0.001" TUNGSTON WIRE)
CATHODE (ALUMINUM SHELL)
+ B10 Li
7+
4+ Energy
-
TRIAXIAL CABLE
DETECTOR HOUSING(TRIAXIAL SHIELD)
18.0"
DETECTOR CANLined with 90% U-235
NEGATIVEELECTRODE
POSITIVEELECTRODECOAXIAL CABLE
INSULATION TRANSITIONFROM TRIAXIAL CABLE
TO COAXIAL CABLE
Argon/Nitrogen Gas Filled
Pa
gge 3
0
3 12"
INSULATORSALUMINUMHOUSING
SIGNAL ELECTRODESECTION NO. 2
HVELECTRODE
SIGNAL ELECTRODESECTION NO. 1CABLE SUPPORT
PLATEHN COAXIALCONNECTORS
SIG. 1
SIG. 2
N. V.
1.38"
144.0"
68.75"SENSITIVE LENGTH
68.75"SENSITIVE LENGTH
3.12"
CABLE LENGTH(25' TYPICAL)
B10 Lined ( reaction
