201.22 ESF Systems Flashcards
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Function of Engineered Safety Features System
Protect the public by controlling the release of fission products and limiting the release of fission products and radiation IAW federal regulations.
Methods Used:
Design core in conjunction with reactor protection system to insure fuel rod integrity
Retain fission products in Reactor Coolant System (RCS)
Retain fission products in Containment
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List accidents for which ESFs are designed
Loss of Coolant Accident (LOCA)
Steam Break
Fuel Handling Accident
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ESF design bases
Seismic Category I - Classification assigned to those structures, systems, and components that are safety-related and designed to withstand the effects of the safe shutdown earthquake and remain functional.
Redundant – Use of multiple trains and instrumentation channels
Independent – ESF trains stand alone
Separate – Physically and electrically separated
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Single Failure Criteria
Fluid and electric systems are considered to be designed against an assumed single failure if neither:
a single failure of any active component (assuming passive components function properly)
NOR
a single failure of a passive component (assuming active components function properly)
results in a loss of the capability of the system to perform its safety function.
An occurrence which results in the loss of capability of a component to perform its intended function.
Multiple failures resulting from a single occurrence are considered to be a single failure.
Train “A” ECW Pump fails to start on SI signal so the associated D/G cannot perform its function.
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10 CFR 50.67 Site Criteria
- An individual located at any point on the boundary of the exclusion area for any 2-hour period following the onset of the postulated fission product release, would not receive a radiation dose in excess of 25 rem total effective dose equivalent (TEDE).
- An individual located at any point on the outer boundary of the low population zone, who is exposed to the radioactive cloud resulting from the postulated fission product release (during the entire period of its passage), would not receive a radiation dose in excess of 25 rem total effective dose equivalent (TEDE).
- Adequate radiation protection is provided to permit access to and occupancy of the control room under accident conditions without personnel receiving radiation exposures in excess of 5 rem total effective dose equivalent (TEDE) for the duration of the accident.
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Difference between an active and passive failure
Active failure - failure of a powered component to perform it’s function (e.g. pump fails to start, valve fails to re-position)
Passive failure - failure of a static component (e.g. a pump seal fails, pipe leak)
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Which systems make up the Engineered Safety Features System?
Emergency Core Cooling (ECCS) - HHSI (1560 psig), LHSI(300 psig), SI Accumulators (600-650 psig)
Containment Isolation
Containment Heat Removal - Containment Spray, RCFCs
Containment Combustible Gas Control - Recombiners, Supplementary Purge
Electrical Aux. Bldg. and Control Room Envelope HVAC
Fuel Handling Building Exhaust HVAC
Auxiliary Feedwater
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What are the Engineered Safety Features support systems?
Ultimate Heat Sink (ECW Pond)
ECW
CCW
Standby D/Gs
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ESF general loading sequence for Mode I actuation
MODE I - SI ONLY
Offsite power available
All equipment operating prior to the MODE I actuation remains in service (load shed signal not generated)
Diesel generators start, but do not connect to the buses
Sequencers start non-operating equipment as required
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ESF general loading sequence for Mode II actuation
MODE II - Loss of Offsite Power (LOOP)
All equipment operating prior to the MODE II actuation is terminated by load shed signal
Diesel generators start and connect to the buses within 10 seconds to restore power
Sequencer starts loads
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ESF general loading sequence for Mode III actuation
MODE III - SI and LOOP
All equipment operating prior to the MODE III actuation is terminated by load shed signal
Diesel generators start and connect to the buses within 10 seconds to restore power
Mode III sequence is the same as Mode I after the load center breakers are sequenced on at 1 second.
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What will cause an SI?
Low PZR Pressure - 1857 psig 2/4
- 2 switches on CP-005 can block if PZR < 1985 psig, both req.*
- Reset with 1 switch or > 1985 psig*
Containment pressure Hi-1 - 3.0 psig 2/3
Low Compensated Steam Line Pressure - 735 psig 2/3 in 1/4 steam lines
- 2 switches on CP-005 can block if PZR < 1985 psig, both req.*
- Reset with 1 switch or > 1985 psig*
- Blocking enables MS Isolation on rate decrease > 100 psig / 50 sec*
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What causes an SI Auto Recirc?
SI present and Lo Lo RWST Level (75,000 gal)
- HHSI and LHSI Miniflow valves close*
- Once 1 valve in each pair is closed, containment sump to SI suction header opens for that train*
- RWST to SI suction header valves must be manually closed by control room operator*
