Wolsong NPP II KHNP
JASON SHINKorea Hydro & Nuclear Power co.
Wolsong NPP II KHNP
CANDU reactorsCANDU reactorsCANDU : Canada Deuterium UraniumCANDU : Canada Deuterium Uranium
(Pressurized Heavy Water Reactor)(Pressurized Heavy Water Reactor)Heavy water(D2O) coolantHeavy water(D2O) coolantHeavy water moderatorHeavy water moderatorNatural uranium fuelsNatural uranium fuels
Wolsong NPP II KHNP
Two systems containing heavy waterTwo systems containing heavy waterPrimary Heat Transport System(PHT system)Primary Heat Transport System(PHT system)
Coolant : 190 tonCoolant : 190 tonHigh temperature : 266 ~ 310 High temperature : 266 ~ 310 ooCCHigh pressure : 100 barHigh pressure : 100 barTritium concentration : Tritium concentration : ~ 2 Ci/kg~ 2 Ci/kgUsual leakage rate : ~ 10 kg/dayUsual leakage rate : ~ 10 kg/day
(Wolsong Unit 3 & 4)(Wolsong Unit 3 & 4)
Wolsong NPP II KHNP
Moderator System(MOD system)Moderator System(MOD system)Moderator : 260 tonModerator : 260 tonLow temperature : 46 ~ 69 Low temperature : 46 ~ 69 ooCCLow pressure : 0.2 barLow pressure : 0.2 barTritium concentration : Tritium concentration : ~ 40 Ci/kg~ 40 Ci/kgUsual leakage rate : ~ 1 kg/dayUsual leakage rate : ~ 1 kg/day
(Wolsong Unit 3 & 4)(Wolsong Unit 3 & 4)
Two systems containing heavy waterTwo systems containing heavy water
Wolsong NPP II KHNP
Features of a PHWRFeatures of a PHWRHigh tritium concentrations in coolant or High tritium concentrations in coolant or
moderatormoderatorInevitable leakage of coolant and Inevitable leakage of coolant and
moderator (not only at a PHWR)moderator (not only at a PHWR)High tritium concentration in air of High tritium concentration in air of
reactor buildingreactor buildingHigh concern about internal dose by High concern about internal dose by
tritiumtritium
Wolsong NPP II KHNP
What happens during sudden heavy What happens during sudden heavy water leakage?water leakage?Tritium concentration in air soars highTritium concentration in air soars highAmount of tritium release increasesAmount of tritium release increasesAmount of heavy water recovery increasesAmount of heavy water recovery increasesWide survey for leakage is neededWide survey for leakage is neededInternal dose of workers increaseInternal dose of workers increase
Wolsong NPP II KHNP
If we know which system heavy If we know which system heavy water leaks from...water leaks from...Survey time will shortenSurvey time will shortenWe can reduceWe can reduce
Heavy water leakageHeavy water leakageTritium releaseTritium releaseInternal dose of workersInternal dose of workers
Wolsong NPP II KHNP
Tritium & heavy water in airTritium & heavy water in air
Heavy water : X+YTritium : AX+BYPHT heavy water : X
PHT tritium : AX
MOD heavy water : YMOD tritium : BY
PHT system MOD system
Wolsong NPP II KHNP
System Equation for X & YSystem Equation for X & YEquations for PHT & MOD heavy waterEquations for PHT & MOD heavy water
AX + BY = TAX + BY = T X + Y = HX + Y = H
X = (T - BH) / (A - B)X = (T - BH) / (A - B) Y = (T - AH) / (B - A)Y = (T - AH) / (B - A)
where A is tritium concentration in PHT heavy water where A is tritium concentration in PHT heavy water (known)(known)
B is tritium concentration in MOD heavy water B is tritium concentration in MOD heavy water (known)(known)
T is tritium in the sample (measured)T is tritium in the sample (measured) H is heavy water in the sample (measured)H is heavy water in the sample (measured) X is PHT heavy water in the sample (unknown)X is PHT heavy water in the sample (unknown) Y is MOD heavy water in the sample (unknown)Y is MOD heavy water in the sample (unknown)
Wolsong NPP II KHNP
Contribution to the leakageContribution to the leakageX & Y show how much PHT heavy water X & Y show how much PHT heavy water
and MOD heavy water exist in the sampleand MOD heavy water exist in the sampleThese are found by comparing the ratio of These are found by comparing the ratio of
tritium (T) to heavy water (H) with the the tritium (T) to heavy water (H) with the the ratios of tritium to PHT heavy water and MOD ratios of tritium to PHT heavy water and MOD heavy water (A & B)heavy water (A & B)
B is much bigger than AB is much bigger than AIf T/H is very close to A, most of heavy water If T/H is very close to A, most of heavy water
and tritium must come from PHT systemand tritium must come from PHT systemIf T/H is a little close to A, most of heavy water If T/H is a little close to A, most of heavy water
comes from PHT system but most of tritium comes from PHT system but most of tritium comes from MOD systemcomes from MOD system
Wolsong NPP II KHNP
Wolsong Power Plant II’s experience 1Wolsong Power Plant II’s experience 1(Unit 3, Dec. 2008)(Unit 3, Dec. 2008)
Tritium concentration in air in the reactor Tritium concentration in air in the reactor building suddenly rosebuilding suddenly rose
Wolsong NPP II KHNP
Wolsong Power Plant II’s experience 1 Wolsong Power Plant II’s experience 1 (Unit 3, Dec. 2008)(Unit 3, Dec. 2008)
Water vapor sampling from the air in the Water vapor sampling from the air in the reactor building using gas washing bottle reactor building using gas washing bottle Tritium in 1g (T) = 25.9 kBqTritium in 1g (T) = 25.9 kBqHeavy water in 1g (H) = 26.4 mgHeavy water in 1g (H) = 26.4 mgHeavy water compensated forHeavy water compensated for
natural deuterium in 1g (H) = 9.7 mgnatural deuterium in 1g (H) = 9.7 mg
※※Tritium concentration in PHT (A) = 1.714 Ci/kgTritium concentration in PHT (A) = 1.714 Ci/kg
Tritium concentration in MOD (B) = 37.92 Ci/kgTritium concentration in MOD (B) = 37.92 Ci/kg
Sampling & analysisSampling & analysis
Wolsong NPP II KHNP
Calculation resultCalculation result85% of leaked heavy water was from PHT 85% of leaked heavy water was from PHT
system,system,
and 15% from MOD systemand 15% from MOD system
20% of tritium in air was from PHT system,20% of tritium in air was from PHT system,
and 80% from MOD systemand 80% from MOD system
※ ※ Ordinarily, more than 90% of tritium in air Ordinarily, more than 90% of tritium in air hadhad
been from PHT systembeen from PHT system
Wolsong Power Plant II’s experience 1 Wolsong Power Plant II’s experience 1 (Unit 3, Dec. 2008)(Unit 3, Dec. 2008)
Wolsong NPP II KHNP
Follow-up actionsFollow-up actions
Wolsong Power Plant II’s experience 1 Wolsong Power Plant II’s experience 1 (Unit 3, Dec. 2008)(Unit 3, Dec. 2008)
An intensive survey on MOD systemAn intensive survey on MOD systemFinding out the leakage point at a junction Finding out the leakage point at a junction
near a pressure instrument of the MOD near a pressure instrument of the MOD systemsystem
Delay Delay TankTank
Callandria
To MOD Purification To MOD Purification SystemSystem
PumpPump
Wolsong NPP II KHNP
Follow-up actionsFollow-up actions
Wolsong Power Plant II’s experience 1 Wolsong Power Plant II’s experience 1 (Unit 3, Dec. 2008)(Unit 3, Dec. 2008)
The tritium concentration in air in the The tritium concentration in air in the reactor building decreased after repairreactor building decreased after repair
Wolsong NPP II KHNP
Wolsong Power Plant II’s experience 2Wolsong Power Plant II’s experience 2(Unit 4, Apr. 2009)(Unit 4, Apr. 2009)
Tritium concentration in air in the reactor Tritium concentration in air in the reactor building jumpedbuilding jumped
Wolsong NPP II KHNP
Water vapor sampling from the air in the Water vapor sampling from the air in the reactor building using gas washing bottle reactor building using gas washing bottle Tritium in 1g (T) = 50.3 kBqTritium in 1g (T) = 50.3 kBqHeavy water compensated forHeavy water compensated for
natural deuterium in 1g (H) = 93.0 mgnatural deuterium in 1g (H) = 93.0 mg
※※Tritium concentration in PHT (A) = 1.513 Ci/kgTritium concentration in PHT (A) = 1.513 Ci/kg
Tritium concentration in MOD (B) = 36.99 Ci/kgTritium concentration in MOD (B) = 36.99 Ci/kg
Sampling & analysisSampling & analysis
Wolsong Power Plant II’s experience 2 Wolsong Power Plant II’s experience 2 (Unit 4, Apr. 2009)(Unit 4, Apr. 2009)
Wolsong NPP II KHNP
Calculation resultCalculation result100.14% of leaked heavy water was from PHT 100.14% of leaked heavy water was from PHT
system,system,
and -0.14% from MOD systemand -0.14% from MOD system
103.7% of tritium in air was from PHT system,103.7% of tritium in air was from PHT system,
and -3.7% from MOD systemand -3.7% from MOD system
※ ※ This irrational result was thought as due to anThis irrational result was thought as due to an experimental error but such results were experimental error but such results were
repeatedrepeated in more samplesin more samples
Wolsong Power Plant II’s experience 2 Wolsong Power Plant II’s experience 2 (Unit 4, Apr. 2009)(Unit 4, Apr. 2009)
Wolsong NPP II KHNP
Further InvestigationFurther InvestigationThe ratio of tritium to heavy water in the The ratio of tritium to heavy water in the
water vapor samplewater vapor samplewas supposed to be between the tritium was supposed to be between the tritium
concentrations in the PHT heavy water and concentrations in the PHT heavy water and MOD heavy water, that is, between 1.513 Ci/kg MOD heavy water, that is, between 1.513 Ci/kg and 36.99 Ci/kgand 36.99 Ci/kg
but, was measured as 1.46 Ci/kg.but, was measured as 1.46 Ci/kg.We started to think about the possibility of We started to think about the possibility of
leaking of another heavy water which has leaking of another heavy water which has lower tritium concentration.lower tritium concentration.
Wolsong Power Plant II’s experience 2 Wolsong Power Plant II’s experience 2 (Unit 4, Apr. 2009)(Unit 4, Apr. 2009)
Wolsong NPP II KHNP
Further InvestigationFurther InvestigationStagnant heavy water in the PHT systemStagnant heavy water in the PHT system
isolated for a long time from circulating coolantisolated for a long time from circulating coolanthad a little less tritium concentration than main had a little less tritium concentration than main
PHT heavy waterPHT heavy waterlike one in Coolant Storage Tank and more like one in Coolant Storage Tank and more
Tritium concentration of heavy water in Coolant Tritium concentration of heavy water in Coolant Storage Tank was measured as 1.40 Ci/kgStorage Tank was measured as 1.40 Ci/kg
This result could explain the ratio of tritium to This result could explain the ratio of tritium to heavy water in the water vapor sample from the heavy water in the water vapor sample from the reactor building, 1.46 Ci/kgreactor building, 1.46 Ci/kg
Wolsong Power Plant II’s experience 2 Wolsong Power Plant II’s experience 2 (Unit 4, Apr. 2009)(Unit 4, Apr. 2009)
Wolsong NPP II KHNP
Follow-up actionsFollow-up actionsA careful survey on isolated systemsA careful survey on isolated systemsFinding out the leakage point on Degas Finding out the leakage point on Degas
Condenser Tank, a semi-isolated systemCondenser Tank, a semi-isolated system
Wolsong Power Plant II’s experience 2 Wolsong Power Plant II’s experience 2 (Unit 4, Apr. 2009)(Unit 4, Apr. 2009)
Heavy Heavy Water Water
Storage Storage TankTank
Degas Degas CondenseCondense
r Tankr Tank PressurizerPressurizer
Main PHT SystemMain PHT System
Wolsong NPP II KHNP
Follow-up actionsFollow-up actionsThe tritium concentration in air in the The tritium concentration in air in the
reactor building decreased after repairreactor building decreased after repair
Wolsong Power Plant II’s experience 2 Wolsong Power Plant II’s experience 2 (Unit 4, Apr. 2009)(Unit 4, Apr. 2009)
Wolsong NPP II KHNP
ConclusionsConclusionsYou can discriminate which system heavy You can discriminate which system heavy
water leaks from, the PHT system or the water leaks from, the PHT system or the MOD system.MOD system.
You can also know how much one of these You can also know how much one of these systems contributes the heavy water leakage systems contributes the heavy water leakage or the increased tritium concentration in air or the increased tritium concentration in air in the reactor building.in the reactor building.
Using this information, you can locate the Using this information, you can locate the leakage point more quickly.leakage point more quickly.
If it works, you can reduce the inner dose of If it works, you can reduce the inner dose of the workers.the workers.
Wolsong NPP II KHNP
Thanks for your Thanks for your attention.attention.
Do you have any Do you have any questions?questions?