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Systems > IRM > Flashcards

IRM Flashcards

1
Q

What is the purpose of IRMs?

A

Monitor and record core neutron flux levels between startup range and power range during startup and shutdown.

Provides trips to protect against rapid reactor power increase that can cause fuel damage from single operator error or equipment malfunction

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2
Q

What is the IRM Detector?

A

Ionization Range Fission Chamber (Ion Chamber)

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3
Q

How Many IRMs are there? Per Channel? What system do they feed?

A

8 total - 4 per channel - 11-14 feed RPS A; 15-18 feed RPS B

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4
Q

What is the IRM detector coating? Fill Gas? Operating Voltage?

A

1.25mg of Uranium Oxide
17.7 psia of Argon Gas
100Vdc

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5
Q

What is the power supply for the IRM Drive Unit?
Rod Matrix?
HV Supply?

A

Drive Unit - A - 28-1; B - 29-1
Rod Matrix (same as SRM) - IB
HV Supply - 24/48vdc - 2A - 11-14 ; 2B - 15-18

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6
Q

What is the IRM Voltage Pre-amplifier?

A

Amplifies low level signal from detector to overcome noise to pass only portions of detector signal necessary for proper operation

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7
Q

How many IRM detector ranges are there and what frequencies do they operate at?

A

10:
1-6 at 8-16kHz
7-10 at 300 - 600kHz

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8
Q

What caution must be taken when switching from IRM range 6 to 7?

A

There is a deadband between the two ranges - may cause a half scram - some operators bypass the halfscram during this switch from 6 to 7

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9
Q

What is the IRM attenuator?

A

Adjusts the gain of the IRM channel according to the range set by the range switch. Resistors set the gain of the voltage divider. Receives signal from the calibrate and diode logic matrix to adjust the gain.

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10
Q

What is the IRM Calibration and Diode Logic Unit?

A

Receives signal from range switches to relay information to other components - ranges from range switches are linear (SRMs are logarithmic)

Sends signal to voltage pre-amplifier to allow pre-amp to select proper frequency ranges
Sends signal to attenuator to adjust gain properly
aids in calibration of IRMs with mode switch operation

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11
Q

What is the IRM Inverter?

A

Inverts the signal from the attenuator - produces a signal of the same size, but inverse from the input signal
Allows for Mean square circuitry to work because it can only square positive signals.
Positive signals bypass inverter. Inverted negative signal and positive signal superposition at the mean square analog circuit.

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12
Q

What is the IRM Mean Square Analog Circuit?

A

USED TO make gamma signals negligible so only Neutron flux is counted

Produces a signal proportional to only the core neutron flux
2 input signals: 1) from attenuator (positive signals) 2) inverted negative signals from inverter - superimposes them
Squares only the positive portions of both to provide input signal
By squaring, smaller gamma inputs are essentially eliminated

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13
Q

What is the Output Amplifier?

A

Converts current output from mean square analog circuit to voltage to be used for meters and trip units

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14
Q

What are the scales of the Output Meters and Recorder ranges? Which range uses which scale?

A

0-40 scale used by odd ranges (1,3,5,7,9)

0-125 scale used by even ranges (2,4,6,8,10)

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15
Q

Which two IRM ranges provide a direct relationship of MWth?

A

7&8 read it straight -
a reading of 20 on 7 is 20MWth
a reading of 60 on 8 is 60 MWth

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16
Q

How do the odd and even IRM ranges relate to the next higher odd/even range?

A

Between each odd/even range and the next highest odd/even range there is a factor of 10 difference

17
Q

How is IRM Range 10 calibrated?

A

reading of 100 equals 1000MWth (33.3% power)

18
Q

How do the odd and next sequential even IRM range relate?

A

An odd and next sequential even range (1 and 2, 3 and 4, etc.) have the same range/amplification, but output is displayed on a different scale:
0-40 vs 0-125

19
Q

What are the power suppllies for the IRMs?

A

11-14 - powerd by 24/48VDC A - feed to RPS A

15-18 powered by 24/48 VDC B - feed into RPS B

20
Q

What are the IRM recorders powered by?

A

11-14 recorders - ESS

15-18 recorders - IB

21
Q

What happens on a loss of power to IRM?

A

causes Half-scram

22
Q

What are the alarms/Trip signals for IRMs?

A 
IRM HI
IRM INOP
IRM Downscale
Detector Wrong Position
IRM HI-HI
23
Q

What signal causes IRM INOP? what is result?

A

Function switch not in operate
HV Low
Module Unplugged

Bypassed when Rx in RUN
Causes Rod Block - can by bypassed with INOP INHIBIT Switch
Causes Scram signal - can be bypassed by INOP INHIBIT Switch

24
Q

What is the IRM Downscale Signal and Result?

A

Setpoint of 8/125 - Rod out block - bypassed on range 1 or Rx in RUN

25
Q

What is IRM HI Signal and Result?

A

Setpoint of 105/125 - Rod Block - Bypassed when Rx in Run

26
Q

What is IRM HI-HI Signal and Result?

A

117/125 - SCRAM - Bypassed when Rx in RUN AND companion APRM not downscale

27
Q

What is IRM Retract Permit (Detector Wrong Position) signal and result?

A

IRM not fully inserted OR
Rx mode switch not in Run

Rod Out Block if one of these not met

28
Q

What happens to IRM with loss of 24/48vdc?

A

Division local indication fail to zero
Division status lights off
RPS Division 1/2 scram
Division Rod Block

Division meters and recorders go downscale

29
Q

What happens to IRM with loss of ESS?

A

11 - 14 recorders lose power

Meters have no effect, recorders fail as-is

30
Q

What is IRM impact of loss of IB?

A 
15-18 
Recorders lose power
Detector drive select matrix control lost
Meters not impacted
Recorders Fail as is
31
Q

What is IRM effect of lost Div. MCC (28-1/29-1)?

A

Lost power to move division detector

32
Q

What is impact of IRM detector short circuit?

A

Max current through circuit - meters and recorders fail upscale

33
Q

What is IRM impact of range switch misposition?

A

May cause downscale alarm or upscale HI or HI-HI alarm depending on direction of switch operation

34
Q

What happens on a complete loss of IRM system?

A

ROd blocks and FULL SCRAM if not in RUN - bypassed if in RUN

35
Q

How many IRMs are REQUIRED (how many may be bypassed) per RPS Subsystem?

A

3 are required - 1 may be bypassed (DEPENDING ON MODE)

36
Q

What impact do radios have on IRMs/SRMS?

A

cabinet on DW Mezz is radio sensitive and may cause spurious scram

37
Q

Where is the IRM reset switch for seal in trip lights?

A

on front of IRM drawer.

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