Department of Nuclear Engineering & Radiation Health Physics
Phenomena 15: Behavior of Core Make-up Tanks
4th Research Coordination Meeting of the IAEA CRP on Natural Circulation Phenomena, Modeling and Reliability of Passive Systems that Utilize Natural Circulation
Brian G. Woods Roy K Nelson Jose N. Reyes, Jr. September 10-13, 2007 IAEA, Vienna, Austria
4th RCM Natural Circulation 1
Department of Nuclear Engineering & Radiation Health Physics
Outline
• The AP600/AP1000 Passive Safety System Designs • CMT System Design • CMT Models • CMT Tests • Conclusions
4th RCM Natural Circulation 2
Department of Nuclear Engineering & Radiation Health Physics
AP600/AP1000 Passive Safety Systems
• Passive Residual Heat Removal (PRHR) System Core Make-up Tanks (CMTs) Automatic Depressurization System (ADS) Accumulator Tanks In-containment Refueling Water Storage Tank, (IRWST) Lower Containment Sump
• •
• •
•
4th RCM Natural Circulation 3
Department of Nuclear Engineering & Radiation Health Physics
Passive Safety Injection
Sump Screen
4th RCM Natural Circulation 4
Department of Nuclear Engineering & Radiation Health Physics
CMT Operation
• The CMT is filled with cold borated water and connected at the top and bottom by balance lines.
– Always at primary pressure – Natural circulation is established when valves are open – Cold borated water enters reactor and hot primary water flows to CMT head.
4th RCM Natural Circulation 5
Department of Nuclear Engineering & Radiation Health Physics
CMT Gravity Drain Model
Mass Conservation:
ρ l ATank
2 E
dL & = − minj dt
2 E
PFS
Darcy Formula:
Density ρ l
L(t) AE
v v ⎛ fl ⎞ hl = Π FE ⎜ +K⎟ = 2g ⎝ d ⎠E 2g
Bernoulli Equation:
& m inj
PE
z=0
2 2 PFS vFS PE vE + z FS + = + zE + + hl ρl g 2 g ρl g 2g
4th RCM Natural Circulation 6
Department of Nuclear Engineering & Radiation Health Physics
CMT Gravity Drain Model
Time Dependent Liquid Level:
ρ l ATank
⎡ ΔP + ρ l gL ⎤ dL & = − mo ⎢ ⎥ ΔPo + ρ l gLo ⎦ dt ⎣
1
2
PFS
Density ρ l
L(t) AE
Initial Mass Flow Rate:
⎧ 2 ρ (ΔPo + ρ l gLo ) ⎫ & o = AE ⎨ l m ⎬ 1 + Π FE ⎩ ⎭
1
& m inj
PE
2
z=0
4th RCM Natural Circulation 7
Department of Nuclear Engineering & Radiation Health Physics
CMT Gravity Drain Model
Governing Differential Equation: Dimensionless Equation:
ρ l ATank
⎧ 2 gL ⎫ dL = − ρ l AE ⎨ ⎬ 1 + Π FE ⎭ dt ⎩
1
2
dL+ = − L+ dt +
where:
( )
1
2
Initial Conditions:
Mo Lo = ρl ATank
⎧ 2 gLo ⎫ & mo = ρ l AE ⎨ ⎬ 1 + Π FE ⎭ ⎩
1 2
L L = Lo & m + & m = & mo
+
t+ =
t
τ
=
(M o
t
& mo )
4th RCM Natural Circulation 8
Dimensionless Curves for Gravity Drain Tanks*
1
0.8
⎛ t+ ⎞ + L = ⎜1 − ⎟ ⎜ 2⎟ ⎝ ⎠
2
⎛ t+ ⎞ & m = ⎜1 − ⎟ ⎜ 2⎟ ⎝ ⎠
+
L and m
0.6
0 ≤ L+ ≤ 1
m+
+
0 ≤ t+ ≤ 2 & 0 ≤ m+ ≤ 1
+
0.4 L+ 0.2
0 0 0.2 0.4 0.6 0.8 1 tl+ 1.2 1.4 1.6 1.8 2
*Constant Tank Cross-Sectional Area, Incompressible Fluid, Form Loss Dominated at Exit.
Department of Nuclear Engineering & Radiation Health Physics
Experiments Involving CMTs
Experiment PACTEL VTT Energy, Finland [3-4] Test Number and Types 5- SBLOCA Codes APROS 4.02. CATHARE RELAP5-MOD3.3 RELAP5/MOD3.3
APEX AP600 Oregon State University, USA, [1] APEX-1000 Oregon State University, USA, [5] SPES-2 Esperienze Termoidrauliche (SIET) laboratories in Piacenza, Italy, [6] ROSA-V, AP600 Japan Atomic Energy Research Institute (JAERI) Japan, [7]
30 NRC Tests and 30 DOE/W Tests SBLOCA, DEDVI, Station Blackout, Inadvertent ADS 11 NRC Tests and 11 DOE/W Tests SBLOCA, DEDVI, Station Blackout 13 DOE/W Tests – SBLOCA, DEDVI 24 NRC Tests – SBLOCA, DEDVI
RELAP5/MOD3.3
RELAP5/MOD3.3
RELAP5/MOD3.3
4th RCM Natural Circulation 10
Department of Nuclear Engineering & Radiation Health Physics
APEX Test Facility at Oregon State University
4th RCM Natural Circulation 11
Department of Nuclear Engineering & Radiation Health Physics
APEX Facility Description
• Complete 2x4 Loop Primary System:
– 1:4 Length Scale, 1:2 Time Scale, 1:192 Volume Scale, Stainless Steel Construction. – 2 Hot Legs, 4 Cold Legs, 2 Steam Generators, Pressurizer, Reactor Vessel with an Electrically Heated Rod Bundle and Upper Plenum Internals.
•
Passive Safety Systems:
– 2 Core Makeup Tanks (CMTs) , 2 Accumulators, a Passive Residual Heat Removal (PRHR) Heat Exchanger, IRWST, and a 4-Stage ADS System.
• •
Operating Conditions:
– Core Power ~ 1 MW, Steam Generator Shell Side Pressure (20 Bar), Pressurizer Pressure (25.5 Bar)
Testing Capabilities:
– Hot & Cold Leg SBLOCAs, MSLB, Inadvertent ADS, Double-Ended DVI Line Break, Station Blackout and Long Term Recirculation.
4th RCM Natural Circulation 12
Department of Nuclear Engineering & Radiation Health Physics
CMT in APEX Test Facility
•
APEX CMT showing balance line connection to the cold leg
Core Makeup Tank (1 of 2)
4th RCM Natural Circulation 13
Department of Nuclear Engineering & Radiation Health Physics
Core Makeup Tank Behaviour (AP600 SBLOCA Testing in SPES and APEX)
• Counterpart SBLOCA Test conducted in SPES-2 and APEX-600 Both facilities show that CMT liquid draining rate was continuous.
– Draining rate was affected by interaction with the accumulator injection flow (~1000s)
Comparison of SPES-2 and APEX-600 CMT Levels for 5 cm SBLOCA
4th RCM Natural Circulation 14
•
Department of Nuclear Engineering & Radiation Health Physics
Core Makeup Tank Behaviour (AP600 SBLOCA Testing in SPES and APEX)
• Counterpart SBLOCA Test conducted in SPES-2 and APEX-600 CMT flow rates decrease for a brief period when Accumulators inject.
•
Comparison of SPES-2 and APEX-600 CMT Flow Rates for 5 cm SBLOCA
4th RCM Natural Circulation 15
Department of Nuclear Engineering & Radiation Health Physics
Conclusions
• CMT behavior
– – – Single-phase natural circulation is reasonably well understood Gravity draining rate model works well Predicting the onset of CMT draining (i.e., interruption of natural circulation) is challenging
• • • Fluid flashing in the balance lines in CMT head Uncovering of balance line inlet System depressurization rate
–
Numerous experiments conducted in support of AP600 and AP1000 certification
• Most data is not available - Westinghouse proprietary
4th RCM Natural Circulation 16