APRM Flashcards
What is the purpose of the APRM?
Provides a continuous indication of core thermal power in power range
Initiates rod blocks and scrams when reactor power approaches a limiting safety setting.
How many APRM channels are there? where do they receive signals from?
6 APRM channels.
21 LPRMs to APRM channels 1,2,&3
20 LPRMs to APRM channel 4,5,6
What is the power supply for the APRM Channels?
APRM Channel Recorders?
APRM 1,2,3 - RPS A APRM 4,5,6 - RPS B Recorder APRM 1,2,3 - ESS Recorder APRM 4,5,6 - IB Indicating lights on 5 panel apron from ESS Bus
What type of logic is included in the APRM circuit for RPS Scrams?
1 out of 2 taken twice.
Allows one in each channel to be bypassed without scram.
What is the purpose of the APRM Averaging Circuit
Produces a signal equal to the average of all LPRM inputs.
Where is the output of the APRM Averaging Circuit sent?
Directly to 902-5 panel recorders Back Panel Meters Assigned OPRM and RBM for power references Plant Process Computer Trip Units
How does APRM Averaging Circuit output relate to core power.
It is directly proportional to the core bulk thermal power
What is the purpose of the APRM Count Circuit?
Generates a signal to indicate the number of operable LPRMs that are assigned to an APRM channel
When TRIP does the ARPM Averaging Circuit Feed? and what are their results?
HI Trip - Rod Block
Downscale Trip - Rod Block
What TRIP does the APRM Count Circuit directly feed? What is the signal and what is the result?
INOP Trip - <50% LPRM assigned to one APRM channel Operable
Triggers alarm and Rod Block
The APRM INOP Trip is fed by the Count Circuit and if less than ____% LPRM are Operable for that channel an alarm comes in. How many LPRMs being inop/bypassed does it take for the alarm to come in?
50% - Alarm comes in after the 9th because one more will remove any margin
What is the TS requirement for LPRMs being operable and supporting APRMs?
Each APRM channel has to have at least 2 operable LPRMs per level (A,B,C,D) and 50% of its LPRM’s - TS Bases 3.3.1.1
On the APRM Count Circuit, what is the value of each LPRM? What is the minimum readout for APRM’s 1,2,3 to be OPERABLE?
Each LPRM is equal to 5%. APRM 1,2,&3 count readout will be 55% because they have 21 LPRMs assigned. Must have 11 available. 11 x 5% is 55%
What is the purpose of the APRM Flow Converter?
Provides flow signal for use in setting flow-biased rod block and scram trip functions.
What are the APRM Flow Converter Setpoints (Normal Operation - Dual Loop in RUN)?
Rod Block Flow Bias Setpoint - 0.56W+54% Rod Block Maximum (clamp) - 108% Scram Flow Biased Setpoint - 0.56W +66% Scram Maximum (Clamp) - 119%
What are the APRM Flow Unit Setpoints for Single Loop?
Rod Block: 0.56W +49%
Rod Block Max (Clamp) : 108%
Scram (half) Hi-Hi: 0.56W + 61%
Scram Max (Clamp): 115%
What are the Flow Unit Setpoints when Mode Switch is not in RUN
Hi - Rod Block - 11%
Hi-Hi - Half Scram - 14%
How does the APRM/LPRM Flow Unit Logic Sequence function?
Recirc loop flow element signal sent to “summer” then to 2 flow converters
Flow converter feeds Trip signals and ouputs to APRM Channels, OPRM and Rod Block Monitors
What Trips does the Flow Unit feed?
If Either of the 2 Flow Units have 110% flow - Hi Trip
The Flow Unit outputs are summed - If there is a 7.5% Mismatch - mismatch trip
Both trips result in Rod Block
How does the Slope Bias Circuit Funtion?
Means that Rod Block and scram setpoints raised and lowered as a function of RR Pump Flow
With no RR Flow, what are the Hi-Hi and Hi Flow Bias setpoints?
Hi - 54%
Hi-Hi - 66%
How does the RPV Mode Switch Interact with APRM Trips and Setpoints?
It modifies the RPS Trips and Interlocks based on mode switch position.
Mode switch interlock ensures taht Rx Power will not exceed 14% when reactor is below 785psig (safety limit)
What is the safety limit for core thermal power?
Below 685 psig limit is below 25% power
WHat are the scram and rod block setpoint limits when not in RUN?
11% power - Rod Block
14% power - SCRAM
What is the AGAF? limit?
It is a ratio of actual power to indicated power.
Must be within 2% nominal value per TS. <1 is conservative.
Why is RR Loop flow used for the flow signal?
Used because it is steady and because core flow signal is noisy
Where are NI Scram signals sent? Rod Block signals?
Scram signals to RPS
Rod Block Signals to RMCS
What are the APRM INOP signals?
9 or more LPRMs Bypassed
Module Unplugged
Mode Switch out of Operate
What is the APRM Downscale Trip?
6% - Rod Block - Bypassed when Mode Switch Out of Run
- Scram when companion IRM Hi-Hi
What happens with loss of respective RPS?
Rod Block and 1/2 scram on loss of APRMs and flow converter
Power-plex shuts down
What happens to APRM on loss of IB?
APRM channels 4,5,6 recorders blank
What happens to APRM on loss of ESS Bus?
APRM channels 1,2,3 recorders blank and all APRM status lights de-=energize
What happens to APRM on LPRM Detector Short Circuit or spike?
Causes increase in affected APRM and may cause Hi-Hi alarm if high enough
