-initiate action to restore one source range channel to operable status-immediately
LCO 3.2.1: Linear Heat Rate
LCO 3.2.1: LHR shall be within the limits specified in the COLR, and the incore alarm system or excore monitoring system shall be operable to monitor LHR
APP: Mode 1 with thermal power >25% RTP
A. LHR, as detected by the auto incore alarm system, not within limits specified in COLR, as indicated on 4 or more coincident incore channels ORLHR, as detected by the excore monitoring system, not within COLR limits OR
LHR, as detected by manual incore detector readings, not within limits specified in the COLR
-Restore LHR to within limits-1 hour
Function and operation of the PR NI comparator/averager?
Accepts buffered output from the summer circuit in each PR channel, averages it with the signals from the other 3 units.
Output is returned to each channel drawer and compared to each channel signal via 2 deviation comparators
Determines deviation between the channel and the average
Serves as indication of Quadrant Power Tilt Ratio
Outputs to a bistable causing "Channel Deviation Alarm" at:
-5% or 10% on front of the NI drawer
-alarm on C-06 EK-06-03/04 RACK C
LCO 3.3.9: Neutron Flux Monitoring Channels
LCO 3.3.9: 2 channels of neutron flux monitoring instrumentation shall be operable
APP: Modes 3,4,5
1 or more required channels inoperable
-suspend all operations involving positive reactivity additions-Immediately
EK0917 "Rod Withdrawal Prohibit"
2/4 VHP pre-trip
-variable 1.5% below VHPT setpoint(or 13.5% above last power level that the VHPT was reset)
1/4 High PWR rate pre-trip
-1.5 DPM when reactor power is > 10-4%RTP and <15%
Removal/Failure of RPS bistable high power rate pre-trip/trip below 15% RTP
What ranges of power do SR/WR/PR NIs cover?
SR covers 6 decades from 0.1 to 105 cps (10-10 to 10-4% power)
WR covers 10 1/3 decades, from 10-8 to 200% power
PR covers 0-125% power
Which NIs supply which RPS channels?
WR channel NI-03
-RPS channels A and C
WR channel NI-04
-RPS channels B and D
SR/WR NI power supplies?
What must be done if the SPI/HOST system is inoperable in Mode 1 > 25% RTP?
PO-3 "Alternate Incore and Excore application" must be performed and actions of T.S. and ORM
Power supplies for PR NIs?
EK-0971 "SPI trouble"
Brought in by the watchdog timer
Check PPC page 900 "PPC network system status"
What is cold leg shadowing?
As T decreases, density increases therefore it reflects more neutrons back into the core therefore indicated power goes down
Typically 0.5% power/degree F
Compensate by periodic excore calibration
How many incore NIs do we have? What are they used for?
-5 detectors each string
-incores can be used as a backup to PR NIs for quadrant power tilt
-determines target AO, which is used to develop target ASI
-allowable power level
-ASI measured by the PR NIs is calculated with the AO determined by the incores
PR NI summer
Sums output of the upper and lower amplifier
-control rod drop detection circuit
--compares immediate signal level with a time delay (8 sec) signal level
--8% drop in under 8 seconds-dropped rod alarm
-15% bistable trip unit
Consequences of incorrectly performing CL-35, neutron monitors system checklist?
Can result in NI channels remaining inoperable, which can reduce redundancy of protective channels and cause entry into tech specs
When must SOP-35 ATT 1 "Heat Balance Verification" be performed?
If heat balance differs by more than 2% from
-any indicated nuclear power channel on the C-27 digital meters or the TMM "status" screen OR-any indicated delta T power channel on any TMM "Primary" screen
EK-06C8 "NI Channel Trouble"
-PR detector high voltage </= 675V
-SR/WR-deviation of 15VDC from setpoint or </= 410VDC
-HS-0102E in AHSP position
Check detector voltage NI-5/6/7/8 > 650VDC
Check "non-oper" light is lit on neutron flux monitor
Purpose of Excore Nuclear Instruments?
8 channels of instrumentation
-2 SR, 2 WR, 4 PR
Monitors neutron flux from the source range through 125% power
Provides signals used to process a reactor trip if any core safety limit is approached
-SUR directly to RPS
-VHPT via TMM to RPS
-TM/LP via TMM to RPS
Effects of loss of Y-10/Y-20 between 10-4%-15% power?
Generates a rod withdrawal prohibit alarm due to the reciept of one of four RPS channel high power rate pre trip bistables
What instrumentation is normally used to monitor core Linear Heat Rate (LHR)?
SPI node in conjunction with the host computer for the PPC (incores)
Effect of a loss of a preferred AC bus on the excore NIs?
Loss of a bus will disable 1 PR channel
Loss of Y-30 or Y-40 will disable 1 SR/WR channel
LCO 3.2.4: Axial Shape Index (ASI)
LCO 3.2.4: The ASI shall be within the limits specified in the COLR
APP: Mode 1 with thermal power >25%
NO </= 1 HOUR ACTIONS
EK-06C3 "Channel Deviation Level 1 5%"
Quadrant power tilt of 5% at 100% power
How is gamma discrimination accomplished in SR/WR? What is campbelling mode?
Both use a pulse height discriminator
Campbelling used for WR at and above approximately 106cps(5X10-3% power)
-measures the amount of current
-will see a step up or step down between .05% to.10% indicated power
Purpose of Incore Nuclear Instrumentation?
Provides measured data that may be used in evaluating the neutron flux distribution in the RX core
Contains thermocouples, 16 of which are post-LOCA environmentally qualified
Data may be used to evaluate thermal margins and to estimate local fuel burnup
Used to calibrate excores with respect to ASI/LHR
How many Excore NIs do we have?
Relationship between SR and WR NIs?
When SR is approximately 3 cps, WR should read approximately 1X10-7%
Advantages/disadvantages of rhodium detectors (incores)?
-can be read manually
-reads precise flux throughout the core for an accurate LHR
-slow response time(nearly 4 minutes to respond)
-t1/2 for Rh-104 is approximately 42 seconds
Effects of a loss of Y-30 or Y-40 between 10-4-15% power?
Also Rx trip on high power rate due to the loss of NI-1/3 or 2/4
Above 15%, only loss of Y-40 generates a RWP alarm
-PR NI-8 generates the signal that bypasses the high power rate (SUR) channel pre-trip at 15% power. If Y-40 is lost you lose this removal therefore the high power rate trip and pre-trip will activate the RWP alarm
PR NI 15% bistable trip unit does?
Enables/bypasses the wide range channel high power rate trip below/above 15% full power
Enables/bypasses the loss of load trip above/below 15% full power
Loss of load trip not needed <15% and rate trip not needed below 10-4% or when in the power range where coefficients limit the rate
Resets low power block to allow ASI alarm in the TMM >15% RTP
Enables low power block to defeat the ASI alarm <14.5% RTP
Generator coastdown trip
-enabled when both NI-5 and NI-6 15% bistables are >15% RTP
How long must you wait before resetting RPS?
30 second lockout
-prevents ratcheting damage
-ensures rods remain free to drop
What is the purpose of the reactor protective system?
Designed to initiate a Rx trip whenever any one of several monitored parameters or conditions deviates from a pre-selected operating range.
-the monitored parameters and conditions, and their allowable operating ranges ensure that the tech spec safety limits are not exceeded
-thus, RPS protects the reactor from damage that could occur if a tech spec safety limit was exceeded
What is the design feature that prevents more than one trip unit for a monitored parameter from being placed in bypass at the same time?
1 keyswitch for each trip which is captured when you place the bypass switch in bypass
EK-06B4 "Hi pressure pressurizer channel trip" and pre-trip?
PZR pressure 2235 psia
2/4 logic give you a reactor trip
Pre-trip at 2185 psia
When should ATWS be bypassed?
With 1 PCS pressure sensor failed high, the ATWS trip shall be bypassed
What are the ATWS power supplies?
Pressure switches are powered from Y-10-40
ATWS matrix relays powered from lighting panels L58 and L59
2/4 logic matrix actuation and relay ATWS1 are powered from Y-230, which is fed from battery D-204
How many aux trip units are there per RPS channel?
EK-06A1 "Variable high power level channel trip"
Minimum 30% reactor power
Variable-15% above power level at which the trip was reset
Maximum of 106.5%
2/4 gives a reactor trip
Maintains margin to DNB
What effect will a single ground have on the RPS?
EK-06D6 "Rate trip channel enabled"
WR NI above 10-4% and PR NI <15% power
Rate trip auto enabled when WR NI >10-4% RTP
Rate trip is automatically bypassed when PR NI power rises to >15%
What type of trip unit only accepts a trip or not-tripped signal?