Source Range Monitors (SRM) - .5

Question 1

Number of SRMs

Answer 1

4

Question 2

Proportional U3O8 fission chamber detector…

Answer 2

pressurized w/ 220psia Argon. Operates at 350 VDC.
- Gammas filter w/ Pulse Height Discriminator.

Question 3

Detector motion.

Answer 3

• Detectors move at 3ft/min and travel a full range of 120”. (From 30” below BAF to 15” above core midplane)
• Approximately 3.3 minutes to insert.

Question 4

Installed sources…

Answer 4

generate enough neutrons to ensure > 3CPS during S/U and S/D ops.

Question 5

How are SRMs operated?

Answer 5

Insert / Withdraw pushbuttons for detectors(retract permit light only indicates counts above 100cps – this DOES NOT prevent you from retracting):
a) Insert PB fully inserts w/ one press.
b) Withdraw must be held.
c) Ensure Power on

Question 6

SRM Scram

Answer 6

SRM Upscale (> 2 x 10^5 cps)

Bypassed by:
- Shorting links installed
- Joystick

Question 7

When does SRM cause a Rod Block?
(Upscale)

Answer 7

-SRM INOP
-Module Unplugged
-Switch out of operate
-High Volts Lost (Low-24V)*
-SRM Upscale Alarm (> 1 x 10^5 cps)

Bypassed by:
- Joystick OR
- MSS in RUN OR
- IRM’s Range 8 or above

Question 8

SRM Rod Block
(Downscale)

Answer 8

• SRM Downscale (< 3 cps)
• SRM Detector Wrong Position
• Detector not fully inserted AND (< 100 cps)

Bypassed by:
- Joystick OR
- MSS in RUN OR
- IRM’s Range 3 or above

Question 9

SRM Alarm

Answer 9

Short Period (< 50 sec)

Question 10

What failures does High Volts Lost (Low-24V)* cause?

Answer 10

*24VDC supplies the high voltage power supply, the drive power is from 10Y202 AC power (loss of 24 VDC does not affect drive power)
- Loss of +24v causes to fail downscale
- Loss of -24v causes tohr fail upscale

Question 11

what occurs when shorting links are removed?

Answer 11

It makes any trip signal single coincidence for the SRMs and IRMs