Containment Building Flashcards
Describe the Containment Building.
- Basically a big steel can. 1” thick at the top, 2” at the bottom. All penetrations are 4” thick
- Free standing structure containing a free volume of approximately 2.5 x 106 ft3
- Additional concrete poured underneath Containment to support Containment vessel up to the 23’ elev.
- Prevent an uncontrolled release of radio-nuclides to the environment during a LOCA to prevent exceeding 10CFR100 release limits.
- The reactor containment structures at St. Lucie meet the design requirements of 10CFR50 Appendix A, “General Design Criteria for Nuclear Power Plants” without loss of capability to perform their safety functions.
Criteria 2 – Design Bases for Protection Against Natural Phenomena (earthquake, flood, tornado, etc.)
Criteria 4 – Environmental and Dynamic Effects Design Bases (Temp, press, humidity & radiation during a LOCA)
Criteria 16 – Containment Design (leak tight barrier against rad release to the environment for length of event)
Describe normal Containment Conditions.
Temp: ~80-100°F
Press: U1: - 0.49 psig to + 0.5 psig
U2: - 0.420 psig to + 0.4 psig
Describe Containment Parameters.
- Design Pressure 44 psig (internal pressure)
- Design Temperature 264 F
- Minimum Service temperature 30 F
- Tech Spec Required CNMT Temperature <120 F
- Tech Spec Required CNMT Pressure Unit 1: - 0.49 psig to + 0.5 psig
Unit 2: - 0.420 psig to + 0.400 psig
Describe the Shield Building.
- Medium leakage concrete structure which surrounds the steel containment vessel
- Purposes:
a) Biological shield during normal operation and after any accident w/i CNMT vessel
b) Protects the containment vessel from external missiles
c) Provides a means of collecting radioactive fission products that may leak from the containment following a major accident - Only structural tie between Containment and Shield Building is the concrete foundation and additional concrete support.
- This allows free movement of the two buildings.
Describe the Shield Building Annulus.
- The space between the Shield Bldg & CTMT
- Provides a volume to dilute and hold leakage from the containment prior to filtering and discharge
- Free volume approx. 540,000 cu. ft
Describe the Primary Shield Wall.
- Serves as biological shield, missile shield, and support for Rx vessel
Describe the Secondary Shield Wall.
- Designed to act as Biological Shield to permit CNMT access during operation
- Protects the Containment Vessel from internally generated missiles; encloses entire RCS
Describe the Refueling Cavity.
- Lay-down area for the reactor vessel internals during refueling and provides a path for fuel transfer to the Fuel Handling Building via the fuel transfer tube.
- During power operation water that collects in the Cavity drains to the Cavity Sump via the CNMT Sump
- Designed to act as Biological Shield to permit CNMT access during operation
- Provides a watertight pool to support fuel movement; concrete lined with SS
Describe the Cavity Seal Ring.
- Seals gap between primary shield wall and Rx vessel
- Permanently installed ring with 6 hatches that are removed during normal operation
- Allows cool air to circulate in order to cool the concrete surfaces
Discuss the Reactor Cavity Sump.
- Located in the lowest level in CTMT, below the RX cavity.
Top of sump at 0’ elevation
Bottom of sump at –7’ elevation - Collection point for unidentified leakage in CTMT.
- 46 gallons / inch – can be used for leakage rate determination
Discuss the Reactor Cavity Drain Pumps.
- Pumps collected water to the Equipment Drain Tank
- Pumps are interlocked with sump isolation valves. Pumps cannot run unless the valves are open.
- Lead pump starts on Hi level / Follow pump starts on Hi-Hi level (with the isolation valves open)
- Lead pump designation swaps after each pump run. Low level float switch stops pumps
- No control of pumps from RTGB; Capacity ~ 50 gpm per pump
- Powered from A5 / B5 MCC
Discuss Reactor Cavity Sump Isolation Valves: (LCV-07-11A & LCV-07-11B).
- Manually operated AOV’s. No auto open signals
- {Both outside CNMT} [one in, one out]
- Fail closed on Loss of Air
- Auto close on:
a) SIAS
b) CIAS - ARP for Rx cavity sump high level requires operator to open valves which will allow sump pump to start
- Tank Level Indication - Bubbler type level transmitter that uses instrument air
- Level Indication Fails Low on Loss of IA (0-48”) (no alarm)
- Level indication is lost post CIAS due to loss of IA to CNMT
Discuss the Contaiment Sump.
- Provides suction for ECCS pumps post RAS; drains to Rx Cavity sump
- Rx Drain Tank is located inside the CNMT Sump
- Bottom of CNMT Sump Elevation: +7.5’
- Sump debris removal through:
a) {Unit 1 uses 21 Independent strainer modules at different elevations. Pipes route the water to a common suction manifold. Unit 1 ECCS pumps take a suction from this common plenum}
b) [Unit 2 uses a series of ‘stacked’ strainers in the Containment Sump to ensure the ECCS water is unrestricted. The outlet of the strainers is a common plenum. The ECCS pumps are supplied from this plenum.]
Discuss Containment Monitoring.
- Instrumentation provided to measure:
a) Reactor Cavity Sump Level Detection
b) Reactor Cavity Leakage Flow Detection
c) Containment Water Level
d) Containment Pressure
e) Containment Temperature
f) Seismic Monitoring
a) Rx Cavity Sump Level
* Bubbler type level detector. Fails low on loss of air. Air isolates on a CIAS
b) Rx Cavity Sump Level indicators: {LI-07-6} / [LIS-07-6}:
* Reads out on RTGB {105} [205]
* 46 gallons / inch
* Level Switch (LS-06-2) feeds “Rx Cavity Sump Hi & Hi-Hi” alarms. This is the alarm operators use to indicate the need to pump down the sump.
c) Rx Cavity Leakage Detection
* Rx Cavity Leakage & CTMT Radiation Monitors are inputs into the RCS Leakage Monitoring T/S
* Detection of water in the Rx cavity sump indicates possible reactor coolant leakage
* All drains that enter the Rx Cavity Sump do so through the Weir Tank
* A triangular notch is machined into side of tank
* If inlet flow into the Weir Tank increases the level in the tank rises and outlet flow increases
* We use this level rise to indicate what leakage flow is.
* Weir Tank level indication is provided via an air bubbler. Output from this level indicator inputs into a flow transmitter, therefore essentially the flow transmitter is being driven by an air bubbler.
* Flow indication (FT-07-3) fails low on Loss of Air
* The Flow transmitter (FT-07-3) indicator then provides input to:
a) {Unit 1: A flow recorder & “RX Cavity Leakage High” Alarm (N-35) @ ≥ 1 gpm}
b) [Unit 2: A flow recorder only]
* {A separate ball float level switch (LS-07-12) provides input to a “RX Cavity Leakage High” Alarm (N-46) @ a level equivalent to a leakrate of ≥ 1 gpm}.
* {This can be used as independent and diverse means of monitoring for TS Unidentified Leakage violation}
Discuss Containment Level Indication.
One Narrow Range Instrument (LT-07-14A)
* Narrow Range Monitors elevation (-7’ to 0’) in Rx Cavity Sump
* Indication provided on:
a) Level indicator & Level Recorder
b) {Located on CRAC panel at Unit 1}
c) [Located on PACB-2 at Unit 2]
d) Also inputs to ERDADS computer
* Unit 1 - Uses Magnetically Operated Reed Switches operated by 1 Float Assembly
* Unit 2 - Uses Heated RTDs (13) at discrete points
Two Wide Range Instruments(LT-07-13A & 13B)
* Wide Range Monitors elevation (-1’ to 26’) CNMT Level.
* Wide range instruments cover from bottom of containment to elevation equivalent to 600,000 gals.
* Same equipment as NR except the WR instruments use {4 floats/reed assemblies} [16 RTDs]
* NPSH for Safeguards pumps:
a) Minimum level of 21’5” required post RAS for adequate NPSH for ECCS pumps
b) Expected level > 25’
* Indication provided on:
a) Level indicators & Level Recorders
b) {Located on CRAC panel at Unit 1}
c) [Located on PACB-2 at Unit 2]
