MCREC (Z41) Flashcards
What are the MCREC Air Handler power supplies?
What are the MCR exhaust fan power supplies?
What is ventilation control power?
What is logic power supply?
1Z41-B003A 1A HVAC: 1R24-S002
from 600 C
1Z41-B003B 1B HVAC: 1R24-S003
from 600 D (1B can supply either unit)
1Z41-B003C 1C HVAC: 1R24-S029
from 1R24-S003 600 D or 1R24-S002 600 C alt
A and C normally in RUN, B in STBY. The 2 AHUs running must be on separate power supplies to be considered operable.
MCR Exhaust Fan A: 1R24-S002 from 600V 1C
MCR Exhaust Fan B: 1R24-S003 from 600V 1D
MCR Exhaust normally secured
Vent Control Power - Critical Instrument Buses 1R25-S066 (A) & 1R25-S067 (B/C)
Logic - 24/48 VDC R25-S015 & R25-S016
What is the design purpose of MCREC?
What pressure is the MCR maintained at?
Designed to ensure habitability after the following radiological DBAs:
Loss of coolant accident
Fuel handling accident
Main steam line break
Control rod drop accident
3.7.4 T.S. Bases: The MCREC System is designed to maintain a habitable environment in the CRE for a 30 day continuous occupancy after a DBA without exceeding 5 rem total effective dose equivalent (TEDE).
MCR is maintained at a positive pressure of ≥ 0.1” WG relative to the Turbine Bldg
What are the initiation signals for the PRESSURIZATION mode of MCREC?
Initiation signals - Pressurization is only AUTO mode
LOCA signal from U1 OR U2
1. 85 psig - 101”
Refuel Floor Area High Radiation from U1 OR U2
ARM 1D21K601B OR 1D21K601D – 15 mR/hr
ARM 2D21K601A OR 2D21K601M – 15 mR/hr
MSL high flow from U1 OR U2
169 (136) psid
MCR intake radiation monitor downscale (N015A/B)
0.017 mR/hr
Required by Tech Specs:
MCR air intake high Radiation (N015A/B) (located
just downstream of roll filter and before filter trains)
0.9 mR/hr
Loss of Power:
U2/U1: RPS A or B, INST A
U1 only: 24/48 VDC A or B
What is the purpose of ISOLATE mode?
How long is the MCR habitable for is placed is ISOLATE?
Eliminate outside air makeup in case of a toxic environment outside of the MCR.
14 people for at least 50 hours
MANUAL only
What are the Air Handling Unit trips for loss of ventilation control power?
Can AHU be restarted?
Ventilation control power comes from Critical Instrument Buses
1Z41-B003A trips on loss of 1R25-S066
1Z41-B003B does NOT trip on loss of either critical instrument bus (R25-S066/S067)
1Z41-B003C trips on loss 1R25-S067
Critical Instrument Bus A
1Z41B003A will trip if operating
If not operating, it cannot be started unless control switch is taken to EMERGENCY RUN
1Z41B003B will auto start on a trip/shutdown of 1Z41B003A
Critical Instrument Bus B
1Z41B003C will trip if operating
If not operating, it cannot be started unless control switch is taken to EMERGENCY RUN
1Z41B003B will NOT auto-start, but can be manually started by taking its control switch to either RUN or EMERGENCY RUN
If operating with control switch in RUN, it will remain operating
What is the purpose of PURGE mode?
Where does the purged air discharge to?
Purge mode used to remove smoke or contaminants (from fire) from the MCR.
MANUAL only
Air enters through one unit and is discharged through the exhaust of the other to remove toxic gases or contaminants.
1 Train of MCREC MUST be declared INOP in Purge Mode.
Discharge to Rx Bldg vent plenum (stack)
What system provides cooling water to MCREC Chiller Units?
Cooling water to each of the condensers is supplied from U1 or U2 PSW w/ both normally aligned to the condensers
PSW system operating @ higher pressure supplies the actual cooling – done via check valves
1Z41B008A is supplied by U1 Div-1 & U2 Div-2 PSW thru 1P41F420A
1Z41B008C is supplied by U1 Div-2 & U2 Div-1 PSW thru 1P41F422B
1Z41B008B is supplied cooling from either the cooling supply to B008A or B008C via cross-connect valves
What air system controls the AOVs in MCREC?
What design feature enables reliability?
U1 instrument air (NIEIA) supplies all the AOVs in MCREC system.
F013 = individual filter train isolation dampers F015 = roll filter bypass damper F016 = roll filter discharge damper
F013A, F013B, F015, and F016 have a special air supply design, using a check valve, followed by an accumulator (A001A/B/C/D) for each valve.
Allows continued ops of these valves if instrument air header broke upstream of the check valve. Remaining AOVs would fail to their designed position on a loss of air.
Which dampers reposition when PRESSURIZATION mode actuates?
Roll filter Byp (F015) Opens
Fltr trn Byp (F011 & 12) Shut
Filter trains
Unisolate (F013A/B) Open and Fans (C012A/B) start
MCR Exh Fans (C011A/B) trip
Restroom dampers shut
Cable Spread Supply and
Exhaust Fans Trip
What will trip the MCREC fans?
What trip(s) are enabled in EMERGENCY RUN?
Fan will trip on thermal overload, low flow in its line, or companion compressor trip
Compressor will trip on thermal overload, high or low (2 different trips) refrigerant pressure, low oil pressure, or companion fan trips
Dampers associated with the air handling unit will automatically close when the fan stops
If the switch is placed in EMERGENCY RUN the fan will start immediately and only trip on thermal overload
