CVCS (Normal Letdown, Excess Letdown) Flashcards
Flow Path, set points
Safety Related Functions
2
1) The CVCS shall be capable of making and holding the core subcritical from any standby or hot operating condition.
2) The CVCS shall be capable of making the core subcritical under
credible accident conditions, w/ appropriate margins for
contingencies, and limiting and subsequent return to power such
that there will be no undue risk to the health and safety of the
public.
Purpose
5
Maintain:
1: RCS chemistry
2: RCS inventory
3: RCP seal water flow
4: Maintain boron concentration
5: Reduce quantity of Fission products/corrosion products also provides for filling and venting of the RCS
Valves that Fail Open on loss of air
5
PCV-145 HCV-121 FCV-113A CVC-310A/B CVC-303A/B/C
ThumbRule
All 3-way valves in the CVCS fail “To VCT”
Effects of loss of IA on CVCS
4 responses
- Letdown is isolated (valves fail closed) [CVC-200a/b/c and LCV-460A/B]
- Charging to loops fail open CVC-310A/B as does HCV-121
- All AOV’s in makeup control fail shut except for the boric acid to blender valve FVC-113A.
- Excess Letdown inoperable.
Letdown Stop Valves (LCV-460 A and B)
- From Loop 1 cold Leg
- Fail close loss of air, or DC power
- In auto will close at 14.4% level in PZR (does not auto reopen)
Regen heat exchanger
- Charging through tubes, should be within 50F of RCS temp.
- 547F to 290F Letdown flow temp change
- 130F to 290F Charging flow temp change
Orifice Isolation Valves (CVC-200 A,B,C)
Close on phase A, loss of air, loss of DC power or manually
Letdown orifices and flows
- A 45gpm
- B,C 60gpm
- Reduces PSIG from 2235 to 300. (Controlled by PCV-145 setpoints)
- Max Letdown flow is 120gpm to prevent channeling of demineralizer resin.
Low Pressure Letdown Relief Valves (CVC-203 A,B)
- set to 500psig and 630psig
- Relieves to the PRT (Pressurizer relief tank)
Letdown Line Isolation Stops (CVC-204 A, B)
location
- Fail closed
- Shut on Phase A
- Have needle valves in air supply lines designed to shut valves after 200s to prevent lifting the relief 203s
- In pipe ally
HCV-143
location
- RHR tie in line after 204s
- RHR heat exchanger room after Charging pump room
Non-Regen Heat Exchanger
- Letdown through tubes, CCW through shell
- TCV-144 (fails open) on CCW outlet side from TE-144 controls outlet temp between 100-115F
Temperature limit on outlet of NRHX?
Why?
Must be kept <140F to protect resin
(TCV-143)
VCT/Demin Diversion Valve
location
- 3 way valve to bypass demins
- Auto diverts at 135F, will swap back at 130F
- Fails to VCT
- 1st floor Non-regen heat exchanger room
(PCV-145)
Low Pressure Letdown Valve
Location
- Maintains 300psig upstream.
- Fails open
- First floor non-regen room.
CVC-209
Low Pressure Letdown relief Valve
- Set at 200psig
- relieves to the VCT
- between PCV-145 and TCV-143
Demin Beds
- Mixed beds (LIOH normally in service and HOH) 120gpm
- Cation bed, limited to 60gpm, reduces lithium concentration
- Deborating beds - Cooler water absorbs boron, Hotter water releases Boron from resin. 1:1 ratio as adding PW
CVC-244
Deborating Demin valve
-Fails to VCT
RCS Filter
Zinc injection skid
- removes impurities and resin fines
- Changed out at 20psid D/P, or high rad
- Zinc reduces outage dosage, in batch tank room
LCV-115A
VCT holdup tank Diversion Valve
location
- Diverts at 30-39” from LT-112
- trips to full divert at 51.6” from LT-115 (resets at 45.6”)
- Fails to VCT
- RCS filter room
VCT (gas inlets and outlets) PCV-119 PCV-118 PCV-117 PCV-199
- PCV-119 Nitrogen (used for cover gas/shutdown)
- PCV-118 Hydrogen (normally in service)
- PCV-117 to Waste Gas Compressor
- PCV-199 to Gas Analyzer
All in the RC Filter room
