Term
PZR Pressure Instrumentation Purpose: |
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Definition
Pressurizer Pressure Control System
§Maintain Reactor Coolant System pressure
§Limit pressure changes during transients
§Prevent RCS from exceeding design pressure of 2485 psig
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Term
| PZR Pressure Design Basis: |
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Definition
Pressure Control System Design Criteria:
§The pressure control system is designed to prevent Rx trips under the following conditions:
§Ramp load change at +/- 5%/min, assuming automatic rod control
§Step load change of +/- 10%, between 15% and 100% power, assuming automatic rod control
§50% load rejection, assuming automatic rod control (10%) and steam dumps (40%)
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Term
| PZR Pressure Instrumentation Outputs: |
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Definition
Outputs:
§OT/DT (4) (122% minus penalty)
§PZR Low Press SI (3) (1765)
§PZR Low Press SI Block / Unblock (3) (P-11) (1915)
§High Press Rx Trip (4) (2385)
§Low Press Rx Trip (4) (1865*)
* Rate Sensitive
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Term
Components, Purpose and Setpoints:
PZR Heaters |
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Definition
Establish and maintain saturation temperature
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§Variable – 415 KW , PWR GP 460 AC
§#21 BU – 415 KW , GP 460AV, emergency C VB
§#22 BU – 969 KW, EP 460 AC, emergency A VB
Variable:
Controlled by Master Pressure Controller
<17% PZR level cutoff and OH E-36 “PZR HTR OFF LVL LO”
MPC 16% (2220psig) heaters- full on, start to modulate as pressure rises.
MPC 34% (2250psig) heaters off.
Back Up:
§MPC Output 9% (2210psig), breakers for 21 and 22 group will close in Auto.
•OHA “PZR HTR ON PRESS LO” also energizes
§MPC Output of 14% (2218psig) the breakers will open if in Auto.
17% PZR Level will trip heaters off (same as Variable Group and same OHA)
Low Level Trip is bypassed when on Emergency Power
Heaters also energize on a PZR level increase 5% above programmed level.
OHA E-20 PZR HTR ON LVL HI
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Term
Components, Purpose and Setpoints:
PZR Spray |
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Definition
Reduce pressure by spraying water from cold legs into the PZR vapor space.
400 gpm each
Bypass lines minimize thermal shock and maintain PZR/ RCS B-conc.
Bypass flow is set by adjusting the valves until PZR spray line temperature is stable between 495 – 505oF.
320oF DT limit between spray line temp and PZR Vapor Temp.
Automatic:
Controlled from Master Pressure Controller
Start to open: 41% (2260psig)
Fully open: 72% (2310psig)
Manual Control is available
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Term
Components, Purpose and Setpoints:
PORVS |
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Definition
PR1 and PR2
210,000 lbm/hr @ 2335 psig full open (always available even with POPs I/S, close 2315 psig
- Limit system pressure to prevent high pressure reactor trip (2385 psig) and prevent undesirable safety valve operation by relieving at 2335 psig.
- Opening setpoint lowered to 375 psig when POPS is armed to provide Brittle Fracture relief protection when RCS is < 312oF
Channels II & IV – PR2 (Logic 2/2 to prevent inadvertent opening of PORV)
Channels I & III – PR1 (Logic 2/2 to prevent inadvertent opening of PORV)
Limits pressure to prevent high pressure trip for up to a 50% load rejection (auto rods and steam dumps)
Each PORV has an associated Block Valve used for isolation in
case of leakage past the PORV
PR-6 powered from 230V MCC A
PR-7 powered from 230V MCC B
Block valves will auto open when POPs is i/s
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Term
Components Purpose and Setpoints:
Safety Valves |
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Definition
Safety Valves (PR3, PR4 & PR5)
Max Flow is 420,000 lbm/hr each
Setpoint: 2485 psig
Designed to prevent RCS from exceeding 110% of design pressure limit (2735 psig)
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Term
PZR Pressure Instrument Failures
CONTROLLING PT FAILS HIGH: |
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Definition
RC PRESS DEVIATION HI Bezel Alarm
OHA D-8, RC PRESS HI
OHA E-42, PR1 1/2 TRIP
PZR Heaters Off
Sprays Full Open
Actual PZR Pressure Dropping
Rx Trip on Low PZR Press before 1865 psig (since Sprays still open) OR OT∆T if >70% RTP
SI at 1765 psig
OHA E-12, PZR PRESS LO
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Term
PZR Pressure Instrument Failures
CONTROLLING PT FAILS LOW: |
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Definition
OHA D-16, RC PRESS LO
OHA E-28, PZR HTR ON PRESS LO
PZR Heaters all on
Actual PZR pressure Rising
Pressure will cycle 2315-2335 psig on PR2 only
Prevents AUTO opening of PR1.
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Term
PZR Pressure Instrument Failures:
ALARM CHANNEL PT FAILS HIGH: |
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Definition
RC PRESS HI Bezel Alarm
OHA D-8, RC PRESS HI
OHA E-43, PR2 1/2 TRIP
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Term
PZR Pressure Instrument Failure:
ALARM CHANNEL PT FAILS LOW:
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Definition
OHA E-12, PZR PRESS LO
OHA D-16, RC PRESS LO
Interlock prevents AUTO opening of PR2
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Term
| PZR Level Instrumentation Purpose: |
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Definition
- Provides a means of maintaining a constant mass during temperature changes, thus reducing the load on the Chemical and Volume Control system and the Waste Disposal system
- Controls charging pump or valves to maintain program level
- Provides protection for: PZR heaters and Isolation of Letdown
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Term
| PZR Level Instrumentation Design Basis: |
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Definition
- Liquid and vapor volumes are sufficient to provide smooth pressure response to programmed RCS volume change
- Liquid volume is sufficient to prevent the heaters from being uncovered during a step load increase of 10 percent power
- Steam volume is large enough to accommodate the surge resulting from a 50% reduction of load, utilizing automatic rod control and steam dump, without the water level reaching the high–level reactor trip setpoint (92%)
- Sufficient steam volume to prevent water relief through the PZR Safety valves, in the event of a complete loss of load, assuming the increasing water level initiates a high PZR level reactor trip (92%)
- The PZR will not empty following a reactor trip, assuming a Reactor Trip causes a turbine trip
- A safety injection signal will not be activated following a reactor trip, assuming a Reactor Trip causes a turbine trip
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Term
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Definition
- 92% Lvl, Rx Trip >P7
- 70% Hi Lvl Alarm
- 57.8%, 100% Power Reference Lvl
- 22.3%, 0% Power Reference Lvl
- 17% Lo Lvl (causes LTDN Isoln Vlvs Close (CV2/277, Orafice vlvs CV3,4,5 close, PZR Htrs Off)
- +5% Deviation BU Htrs Full On, and OHA E-20
- -5% Deviation Bezel Alarm
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Term
| Scenarios and Indicated PZR Levels |
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Definition
- Containment Temp Increases- PZR Lvl Increases
- Reference Leg Leaks- PZR Lvl Increases
- DP Cell Failure- PZR Lvl Increases
- Variable Leg Loss (actual RCS Leak)- PZR Lvl Decreases
NOTE: If leak in vapor space-actual level will increase due to RCS voids |
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Term
PZR Level Instrument Failures:
CONTROLLING LT FAILS HIGH: |
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Definition
OHA E-20, PZR HTR ON LVL HI
Charging Flow Demand goes to Minimum
PZR Heaters come on (+5% Dev)
Actual PZR Level is Dropping, at 17%:
- Orifice Isol Vlvs Close(CV3, 4, 5)
- All PZR Heaters off
- CV277 Closes
Actual Level now rises (min Chg, No L/D)
PZR LVL HI Bezel Alarm
OHA E-4, PZR LVL HI
Rx Trip at 92% (if > P-7)
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Term
PZR Level Instrument Failure
CONTROLLING LT FAILS LOW: |
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Definition
PZR LVL LO Bezel alarm
Chg Flow Demand Rises
Letdown Isolates (CV 2, 3, 4, 5)
All PZR Heaters Off
Actual level is Rising
OHA E-4, PZR LVL HI
Rx Trip at 92% (if > P-7)
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Term
PZR Level Instrument Failures:
ALARM CHANNEL LT FAILS HIGH:
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Definition
PZR LVL HI Bezel Alarm
OHA E-4, PZR LVL HI
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Term
PZR Level Instrument Failures:
ALARM CHANNEL LT FAILS LOW:
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Definition
Letdown Isolates (CV277, 3, 4, 5)
PZR Heaters Off
OHA E-36, PZR HTR OFF LVL LO
PZR Pressure Dropping (Htrs Off)
Actual PZR Level Rising (Min Chg, No L/D)
OHA E-4, PZR LVL HI
Rx Trip at 92% (if > P-7) ** Only Alarm Channel which will yield a Rx Trip**
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