LPRM

Question 1

What is the purpose of LPRMs?

Answer 1

to Continuously monitor local thermal neutron flux and initiate alarms on excessive flux conditions.
Assist in the evaluation of the local heat flux conditions to ensure thermal limits (MCPR) are not exceeded.
Provide local power indication inputs to APRMs, RBM, and process computer

Question 2

What other systems do LPRMs provide input to?

Answer 2

APRM, RBM, and Process Computer

Question 3

How many LPRM groups are there?
How many per group?
what are the power supplies?

Answer 3

There are two groups, 1 and 2
There are 21 LPRMs in Group 1 and 20 in Group 2
Group 1 is powered by RPS A; Group 2 by RPS B

Question 4

What voltage is supplied to the LPRM detector?

Answer 4

100vdc

Question 5

What kind of Detector is used for LPRMs?

Answer 5

Fission chamber without Gamma compensation

Question 6

Why is Gamma COmpensation not needed for LPRMs?

Answer 6

signal to noise ratio is high and gamma flux is proportional to power at normal operating (not low power) conditions.

Question 7

How many Detectors are part of each LPRM and how many LPRMs are there total?

Answer 7

There are 4 detectors (A,B,C,D) per LPRM. 41 total LPRM

164 total detectors

Question 8

How are the LPRMs laid out in the Core?

Answer 8

They are symmetrical about the core center. They are laid out so that every core location, or it’s symmetrical counterpart in the core (opposite quadrant), is monitored.

Question 9

Where are the LPRM detectors located relative to the Core?

Answer 9

A is 18” above bottom of fuel. Each successive one is 36” away.
B is 36” above A
C is 36” above B
D is 36” above C - which is 18” below TAF

Question 10

What are the major components of the LPRM circuit?

Answer 10

Detector - conditioned by the flux amplifier - to a single gain circuit - buffer amplifier - and to the RBM matrix

Question 11

What is the LPRM Flux Amplifier?

Answer 11

It is used to convert the detector signal to a voltage signal large enough to drive the trip units, corresponding to a heat flux of 0 - 125watt/cm^2 -

Question 12

What does the LPRM Flux Amplifier provide output to?

Answer 12

APRM Averaging circuits
OPRMs
Process Computer
RBM

Question 13

How many amplification ranges doe the LPRM Flux Amplifier have and why?

Answer 13

3 - to compensate for detector depletion or production of Uranium in the detector

Question 14

What is the purpose of the LPRM Functional Switch and what positions can it be in?

Answer 14

Allows for calibration of LPRM Amplifier and bypassing Inoperable LPRM
OPerate ; Calibrate : BYpass

Question 15

How many indicating lights are there in the back panel for LPRMs?
What are they? What is their condition when the alarm clears?

Answer 15

3 for each LPRM - 
BIG DUMB UGLY
Bypass (white)
Downscale (White)
Upscale (Amber

The back panel lights for downscale and upscale seal in. The -5 panel auto resets.

Question 16

What happens with a loss of power to an LPRM?

Answer 16

Output of detector drops to zero, resulting in LPRM low alarm

Question 17

What happens with a loss of power to the LPRM Cabinets?

Answer 17

All LPRMs in cabinet fail to zero

Question 18

Where on the front panel do the LPRMs display and whey do they display?

Answer 18

They display when the CR they surround is selected.

They display on the edgewise meters on -5 panel at the 4 rod display

Question 19

What powers the “reflected light” for the LPRM -5 panel display?

Answer 19

Instrument Bus

Question 20

What are the LPRM Alarms?

Answer 20

Downscale Trip
Trip Inhibit
Upscale Trip

Question 21

What is the LPRM Downscale Alarm?

Answer 21

2.75 to 3.25 w/cm^2

Question 22

What is the LPRM Upscale Alarm?

Answer 22

100w/cm^2