Intermediate Range Monitors (IRM) - .5

Question 1

Number of IRMs

Answer 1

• Total of 8 IRMs.
• Two channels each with 4 IRMs.

Question 2

70% enriched U3O8 fission chamber Ionization detector…

Answer 2

pressurized with 18 psia Argon. Operates at 100VDC.

Question 3

IRM meter scaling.

Answer 3

3. Meters have 2 scales. Moving from even to odd upward increases scale by a factor of 10:
   a) 1,3,5,7 – 0-40% of scale*
   b) 2,4,6,8 – 0-125% of scale*
   c) Change range light – 25% and 75% of scale.
   *Going from the odd ranges to the even ranges expands the scale from (0-40) to (0-125). Then going from the even to the odd ranges will change the magnitude of the scale by a factor of 10 (Increase if going down, decrease if going up). Ranging changes which voltage pre-amps and attenuators are placed in service

Question 4

IRM meter scaling.

Answer 4

Meters have 2 scales. Moving from even to odd upward increases scale by a factor of 10:
a) 1,3,5,7 – 0-40% of scale*
b) 2,4,6,8 – 0-125% of scale*
c) Change range light – 25% and 75% of scale.
*Going from the odd ranges to the even ranges expands the scale from (0-40) to (0-125). Then going from the even to the odd ranges will change the magnitude of the scale by a factor of 10 (Increase if going down, decrease if going up). Ranging changes which voltage pre-amps and attenuators are placed in service

Question 5

IRM gamma compensation.

Answer 5

Gamma compensates with a “Means Square Analog Unit”. Number of events occurring over time is proportional to square root of the change in the mean over the same time period. (Campbelling) Makes gamma count incredibly small (negligible).

Question 6

IRM vs. RMCS channels

Answer 6

• IRM’s A,B,E,F = RMCS A - IRMS C,D,G,H = RMCS B

Question 7

IRM vs. RPS channels

Answer 7

• IRM’s A,C,E,G = RPS A
• IRMS B,D,F,H = RPS B

Question 8

IRM Upscale (120/125 Scale)

Answer 8

• 38.4/40
• Half Scram

Bypass:
- Joystick OR
- MSS in RUN

Question 9

IRM Upscale

Answer 9

• 108/125
• 34.5/40
• Rod Block

Bypass:
- Joystick OR
- MSS in RUN

Question 10

IRM INOP
Module Unplugged
Switch out of operate
High Volts Lost(Low 24V)

Answer 10

• Rod Block AND
  Half Scram.

Bypass:
- Joystick OR
- MSS in RUN

Question 11

IRM Downscale (5/125 Scale)

Answer 11

• (1.6/40)
• Rod Block

Bypass:
- Joystick OR
- MSS in RUN OR
- IRM’s Range 1

Question 12

Detector Not Full in

Answer 12

• Rod Block

Bypass:
- Joystick OR
- MSS in RUN

Question 13

High Volts Lost(Low 24V)*

Answer 13

*IRMs are powered from 24 VDC. They will fail downscale and INOP on a loss of the 24 VDC signal.