Nuclear Reactor ExperimentGroup III

Reactivity and Power Reactivity and Power Distribution AnomaliesDistribution Anomalies

ProloguePrologue

Steam generator(16%) At power fuel handling systems(1%)Reactor core(13%) Control rod drive(15%)Primary coolant system(26%) Pressure control(10%)Recirculating water(7%) Moderator & Auxiliaries(2%) Reactor vessel(10%)

2002 IAEA AIRS

ProloguePrologue

Life SafekeepingFinancial Efficiency

Table of ContentsTable of ContentsRCCA accident analysisRCCA accident analysis

Accident SimulationAccident Simulation

ConclusionConclusion

RCCA Accident AnalysisRCCA Accident Analysis

Reactivity Reactivity

Power Power DistributioDistributio

nnANS Cond.II,III ANS Cond.II,III

Drop of a single control rod in CBCDrop of a single control rod in CBC

Rod bank uncontrolled inRod bank uncontrolled in

Rod bank uncontrolled out (Low Power)Rod bank uncontrolled out (Low Power)

Rod bank uncontrolled outRod bank uncontrolled out (Full Power) (Full Power)

Cold ShutdownCold Shutdown

Power Operation

Hot ShutdownHot Shutdown

Hot StandbyHot Standby

StartupStartup

Rod bank uncontrolled out (Full Power)

Rod bank uncontrolled in

Drop of a single control rod in CBC

Rod bank uncontrolled out (Low Power)

RCCA Accident AnalysisRCCA Accident Analysis

Variable ListVariable List

Net ReactivityNet Reactivity

Relative Prompt PowerRelative Prompt Power

Normalized Thermal Normalized Thermal Power Dist.Power Dist.Average Fuel Average Fuel TemperatureTemperatureCore Coolant Core Coolant TemperatureTemperatureDNBRDNBR

Power & flux relationPower & flux relation

V f dvPower ftyPowerdensi

221111212

2

1 )( ffsadx

dD

01122222

2

2 sadx

dD

22

2

212

1212

2

1 0

as

sa

dx

dD

dx

dD

M

0021 ffF

2 Group Diffusion Equation2 Group Diffusion Equation

Define

k

k

k

11

dEdVM

dEdVFk

1

Power & flux relationPower & flux relation

0)( FM

Multiplication constantMultiplication constant

ReactivityReactivity

Eigenvalue problem

Accident SimulationAccident SimulationRod bank uncontrolled out (Power 50%)Rod bank uncontrolled out (Power 50%)

Rod bank uncontrolled out (Low Power)Rod bank uncontrolled out (Low Power)

Drop of a single control rod in Drop of a single control rod in CBCCBC

Rod bank uncontrolled inRod bank uncontrolled in

Rod bank uncontr. out (Power 50%)Rod bank uncontr. out (Power 50%)

Condition to SimulateCondition to Simulate

• Operating State : Power (50%)

• Duration Time : 130 (s)

• Bank D Withdrawal

• Initial Core Condition

• Temperature(°C) : 537

• Pressure(Pa): 1.56 X 10^7

• Reactivity : 3.66 X 10^-6

• DNBR : 2.05

DD

DD

DD

DD

Rod bank uncontr. out (Power 50%)Rod bank uncontr. out (Power 50%)

Rod bank uncontr. out (Power 50%)Rod bank uncontr. out (Power 50%)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 5 10 15

Time(sec)

Frac

tion

of n

omina

l

Nuclear powerHeat flux

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 20 40 60 80

Time(sec)

Fra

ctio

n o

f nom

inal

Nuclear powerHeat flux

Rod bank uncontr. out (Hot Standby)Rod bank uncontr. out (Hot Standby)

Condition to SimulateCondition to Simulate

• Original Target : Neutron Flux Trip

• CNS : Absence of Neutron Flux detect function ->Non neutron flux trip

• Alternative proposal -Malfunction of Bank “D” at Hotstanby state -Net Reactivity, Thermal power transient -Etc., Transient features

Rod bank uncontr. out (Hot Standby)Rod bank uncontr. out (Hot Standby)

Condition to SimulateCondition to Simulate

• Operating State : Hot Standby

• Duration Time : 200 (s)

• Bank D Withdrawal

• Initial Core Condition

• Temperature (°C) : 292

• Pressure(Pa) : 1.56 X 10^7

• Reactivity : 1.7 X 10^-2

• DNBR : 10

DD

DD

DD

DD

Rod bank uncontr. out (Hot Standby)Rod bank uncontr. out (Hot Standby)

Rod bank uncontr. out (Hot Standby)Rod bank uncontr. out (Hot Standby)

DNBR=DNB Heat flux predicted applicable correlation

Reactor local heat flux

Drop of a single control rod in CBCDrop of a single control rod in CBC

Condition to SimulateCondition to Simulate

• Operating State : Full Power

• Duration Time : 200 (s)

• Single Rod Drop

• Initial Core Condition

• Temperature (°C) : 734

• Pressure (Pa) : 1.55 X 10^7

• Reactivity : 8.16 X 10^-8

• DNBR : 1.34

CC

Drop of a single control rod in CBCDrop of a single control rod in CBC

Drop of a single control rod in CBCDrop of a single control rod in CBC

Rod bank uncontrolled inRod bank uncontrolled in

Condition to SimulateCondition to Simulate

• Operating State : Full Power

• Duration Time : 400 (s)

• Bank A Drop

• Initial Core Condition

• Temperature (°C) : 734

• Pressure(Pa) : 1.55 X 10^7

• Reactivity : 8.16 X 10^-8

• DNBR : 1.34

AA

AA

AA

AA

Rod bank uncontrolled inRod bank uncontrolled in

Rod bank uncontrolled inRod bank uncontrolled in

Rod bank uncontrolled inRod bank uncontrolled in

ConclusionConclusion• Confirm equations and it’s implications relating to Reactor core

• Verify the correlation of RCCA position change and Reactor condition variables

• Safety acknowledgement through accident simulation

• Unrealistic setup which is not applicable to conservative assumption