APRM

Question 1

What is the purpose of the APRM?

Answer 1

Provides a continuous indication of core thermal power in power range

Initiates rod blocks and scrams when reactor power approaches a limiting safety setting.

Question 2

How many APRM channels are there? where do they receive signals from?

Answer 2

6 APRM channels.
21 LPRMs to APRM channels 1,2,&3
20 LPRMs to APRM channel 4,5,6

Question 3

What is the power supply for the APRM Channels?

APRM Channel Recorders?

Answer 3

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

Question 4

What type of logic is included in the APRM circuit for RPS Scrams?

Answer 4

1 out of 2 taken twice.

Allows one in each channel to be bypassed without scram.

Question 5

What is the purpose of the APRM Averaging Circuit

Answer 5

Produces a signal equal to the average of all LPRM inputs.

Question 6

Where is the output of the APRM Averaging Circuit sent?

Answer 6

Directly to 902-5 panel recorders
Back Panel Meters
Assigned OPRM and RBM for power references
Plant Process Computer
Trip Units

Question 7

How does APRM Averaging Circuit output relate to core power.

Answer 7

It is directly proportional to the core bulk thermal power

Question 8

What is the purpose of the APRM Count Circuit?

Answer 8

Generates a signal to indicate the number of operable LPRMs that are assigned to an APRM channel

Question 9

When TRIP does the ARPM Averaging Circuit Feed? and what are their results?

Answer 9

HI Trip - Rod Block

Downscale Trip - Rod Block

Question 10

What TRIP does the APRM Count Circuit directly feed? What is the signal and what is the result?

Answer 10

INOP Trip - <50% LPRM assigned to one APRM channel Operable

Triggers alarm and Rod Block

Question 11

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?

Answer 11

50% - Alarm comes in after the 9th because one more will remove any margin

Question 12

What is the TS requirement for LPRMs being operable and supporting APRMs?

Answer 12

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

Question 13

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?

Answer 13

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%

Question 14

What is the purpose of the APRM Flow Converter?

Answer 14

Provides flow signal for use in setting flow-biased rod block and scram trip functions.

Question 15

What are the APRM Flow Converter Setpoints (Normal Operation - Dual Loop in RUN)?

Answer 15

Rod Block Flow Bias Setpoint - 0.56W+54%
Rod Block Maximum (clamp) - 108%
Scram Flow Biased Setpoint - 0.56W +66%
Scram Maximum (Clamp) - 119%

Question 16

What are the APRM Flow Unit Setpoints for Single Loop?

Answer 16

Rod Block: 0.56W +49%
Rod Block Max (Clamp) : 108%
Scram (half) Hi-Hi: 0.56W + 61%
Scram Max (Clamp): 115%

Question 17

What are the Flow Unit Setpoints when Mode Switch is not in RUN

Answer 17

Hi - Rod Block - 11%

Hi-Hi - Half Scram - 14%

Question 18

How does the APRM/LPRM Flow Unit Logic Sequence function?

Answer 18

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

Question 19

What Trips does the Flow Unit feed?

Answer 19

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

Question 20

How does the Slope Bias Circuit Funtion?

Answer 20

Means that Rod Block and scram setpoints raised and lowered as a function of RR Pump Flow

Question 21

With no RR Flow, what are the Hi-Hi and Hi Flow Bias setpoints?

Answer 21

Hi - 54%

Hi-Hi - 66%

Question 22

How does the RPV Mode Switch Interact with APRM Trips and Setpoints?

Answer 22

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)

Question 23

What is the safety limit for core thermal power?

Answer 23

Below 685 psig limit is below 25% power

Question 24

WHat are the scram and rod block setpoint limits when not in RUN?

Answer 24

11% power - Rod Block

14% power - SCRAM

Question 25

What is the AGAF? limit?

Answer 25

It is a ratio of actual power to indicated power.

Must be within 2% nominal value per TS. <1 is conservative.

Question 26

Why is RR Loop flow used for the flow signal?

Answer 26

Used because it is steady and because core flow signal is noisy

Question 27

Where are NI Scram signals sent? Rod Block signals?

Answer 27

Scram signals to RPS

Rod Block Signals to RMCS

Question 28

What are the APRM INOP signals?

Answer 28

9 or more LPRMs Bypassed
Module Unplugged
Mode Switch out of Operate

Question 29

What is the APRM Downscale Trip?

Answer 29

6% - Rod Block - Bypassed when Mode Switch Out of Run

- Scram when companion IRM Hi-Hi

Question 30

What happens with loss of respective RPS?

Answer 30

Rod Block and 1/2 scram on loss of APRMs and flow converter

Power-plex shuts down

Question 31

What happens to APRM on loss of IB?

Answer 31

APRM channels 4,5,6 recorders blank

Question 32

What happens to APRM on loss of ESS Bus?

Answer 32

APRM channels 1,2,3 recorders blank and all APRM status lights de-=energize

Question 33

What happens to APRM on LPRM Detector Short Circuit or spike?

Answer 33

Causes increase in affected APRM and may cause Hi-Hi alarm if high enough