24-28 Nov., 2008The 2nd RCM, IAEA CRP
KHNP-NETEC
Korea Hydro & Nuclear Power Co., Ltd. (KHNP)Nuclear Engineering & Technology Institute (NETEC)
Joo Wan Park and Chang Lak Kim
The 2nd Research Co-ordination Meeting on Behaviour of Cementitious Materials in Long Term Storage The 2nd Research Co-ordination Meeting on Behaviour of Cementitious Materials in Long Term Storage and Disposal of Radioactive Waste Bucharest, Romaniaand Disposal of Radioactive Waste Bucharest, Romania
Long-term Behavior of Cementitious Materials in the Korean Long-term Behavior of Cementitious Materials in the Korean
Repository EnvironmentRepository Environment
(Research Agreement No. 14246)(Research Agreement No. 14246)
24-28 Nov., 2008The 2nd RCM, IAEA CRP
KHNP-NETEC
Today……
Background
- Briefs on LILW Management & National Disposal Project
Objectives & Scope
Overall Implementation Plan
Research Work Done & Results
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24-28 Nov., 2008The 2nd RCM, IAEA CRP
Nuclear Energy in Korea
Under constructionIn operation ( CANDU
Seoul
Daejeon
Gori
Uljin
Wolsong &Sinwolsong
Yonggwang
Planned
(As of November 2008) Commercial operation of Gori Unit #1 began in 1978
Currently total 20 NPPs (16 PWRs and 4 CANDUs) in commercial operation
6 under construction 2 currently in planning Nuclear share of
electricity 38.6 %WolsongLILW Disposal Center
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24-28 Nov., 2008The 2nd RCM, IAEA CRP
LILW Management
Arising of LILW from: Application of RI and Operation of NPP Amount of radioactive waste storage (As of Dec.
2007):LocationLocation
Number ofReactors
Number ofReactors
KoriKori 44
YonggwangYonggwang 66
UlchinUlchin 66
WolsongWolsong 44
StorageCapacity(drums)
StorageCapacity(drums)
50,20050,200
23,30023,300
17,40017,400
9,0009,000
TOTALTOTAL 99,90099,900
Cumulativeamount(drums)
Cumulativeamount(drums)
35,56035,560
16,45416,454
12,87712,877
6,0356,035
70,92670,926
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Status of National LILW Disposal Project
Name: Wolsong LILW Disposal Center Site Location: Gyeongju (South Eastern Part of Korean Peninsula) Area: 2,096,491 m2 (2.1 Mm2) Capacity: 100, 000 drums (Phase I), 800,000 drums (Final) Disposal Type: Silo type disposal (Phase I) Project Duration: ’06. 1 ~ ’10. 6 License: Approved for Construction & Operation by MEST
(Regulatory Authority) on July 2008 Construction: Started on August 2008
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A Bird’s Eye View of Wolsong Site
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24-28 Nov., 2008The 2nd RCM, IAEA CRP
Concept of Surface Facility and Disposal Silos
6 Silos for phase 1
Vertical shaft
Entrance portal of C/O tunnels
Surface facilities
C/T
O/T
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Operational Tunnel
Construction Tunnel
Vertical Shaft
Disposal Silos
Concept of Surface Facility and Disposal Silos
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Concept of Facility Closure
Crushed Rock
Crushed Rock
Concrete Overpack
Concrete Plug
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Objectives To investigate the closure concepts and cementitious backfill materials for the facility closure. To gain practical experiences in major issues considered in closure concept of the Korean LILW repository.
Scope Characterization of concrete container and cementitious backfill materials in the Korean LILW repository Development of repository closure concept and evaluation of long-
term behavior of cementitious materials Radionuclide transport modeling considering concrete degradation in repository conditions
Objectives and Scope
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24-28 Nov., 2008The 2nd RCM, IAEA CRP
Year 1
Characterization of concrete container and cementitious backfill materials in the Korean LILW repository
Packaging consideration for disposal in silo type repository Investigation of backfill materials for repository closure Performance test for physico-chemical properties of backfill materials
Year 2(On-going)
Development of repository closure concept and evaluation of long-term behavior of cementitious materials
Establishment of closure concept for unit silo and disposal facility Evaluation of gas generation and migration in disposal silo Degradation modeling of concrete structure and/or backfill materials
Overall Implementation Plan
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Year 3
Radionuclide transport modeling considering concrete degradation in repository conditions
Development of conceptual models for intact and degraded conditions
Implementation of input parameter database and quality assurance for safety/performance assessment
Safety/performance assessment of disposal facility using a proprietary computer tool
Overall Implementation Plan
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Research Work Done & Results
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■ Laboratory Test of Cementitious Backfill Materials
■ Gas Generation & Migration Studies
■ Degradation Modeling of Concrete Structure
■ Comparison of Silo Closure Option in the Site-specific
Condition
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Lab. test of cementitious backfill materials
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Case Material Composition
I cement:fly ash:water:sand1:0.25:0.56:2.585
(used in domestic nuclear facility)
II cement: water: sand1:1.13:4
(used in Sweden SFR)
III cement: water: sand1:0.5:0.5
(porous cement mortar)
■ Composition of cement mortars
Test Item Unit Test Method
Specific gravity g/ ㎤ ASTM C 642
porosity % ASTM D 4284
Compressive strength N/ ㎟ KS L 5105
Hydraulic conductivity m/s ASTM D 5084
Gas permeability ㎡ Torrent method
Critical pressure Pa Torrent method
Bulk density g/ ㎤ KS F 2308
■ Test methods
AP
Qlmk
A
Q
PP
hPK
22
21
22
where K : gas conductivity (m/s), P1 : inlet pressure(kg/ ㎡ ),
P2 : atmospheric pressure(kg/ ㎡ ),
h: thickness of specimen (m), Q : gas flow rate( ㎥ /s), A : Area( ㎡ ), γ : gas unit mass /volume(kg/ ㎥ ).
where K : gas conductivity (m/s), P1 : inlet pressure(kg/ ㎡ ),
P2 : atmospheric pressure(kg/ ㎡ ),
h: thickness of specimen (m), Q : gas flow rate( ㎥ /s), A : Area( ㎡ ), γ : gas unit mass /volume(kg/ ㎥ ).
where k : hydraulic conductivity (m/s), Q : flux per unit time( ㎥ /s), A:cross-sectional area of specimen( ㎡ ), P : water pressure(kg/ ㎡ ), l : thickness of specimen (m), m : unit mass of water ( ㎏ / ㎥ ).
where k : hydraulic conductivity (m/s), Q : flux per unit time( ㎥ /s), A:cross-sectional area of specimen( ㎡ ), P : water pressure(kg/ ㎡ ), l : thickness of specimen (m), m : unit mass of water ( ㎏ / ㎥ ).
Hydraulic conductivity
Gas permeability
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24-28 Nov., 2008The 2nd RCM, IAEA CRP
mixing condition
of domestic NPP mixing condition
of swedish
disposal facility
bubbled cement
mortar
1.E- 12
1.E- 11
1.E- 10
1.E- 09
1.E- 08
hyd
raulic c
onductivi
ty[m
/s]
■ Test results
CaseDry density
(g/ ㎤ )Porosity(-) )×10-2
Compressive strength(N/ ㎟ )
Hydraulic conductivity( ㎝ /s)×10-9
Gas permeability( ㎡ )×10-16
I 1.871 6.89 83.4 0.6763 1.421
II 1.923 27.54 8.9 2.6987 7.068
III 0.802 24.66 7.7 269.82 180.256
Hydraulic conductivity of various mixing conditions of cement mortar Hydraulic conductivity of various mixing conditions of cement mortar
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Gas Generation in a Silo Metal corrosion, Microbial degradation : GAMMON (UKAEA) Radiolysis : MAXH2 (KHNP) DAW, 200 L Steel Drum, 16700 Drums in a Silo
Most of gas generation comes from metal corrosion in the form of H2.
After 1,000 yrs, H2 gas generation is about 9.0×104 m3 .
Gas generation is rapidly increased immediately after closure.
Gas generation due to microbial degradationGas generation rate due to metal corrosion
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24-28 Nov., 2008The 2nd RCM, IAEA CRP
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Spatial distribution of gas pressure in the model domain after 1000 years of hydrogen gas generation from the radioactive waste
Vertical cross section and mesh of the model domain and seven monitoring points used in the numerical simulations
TOUGH-II simulation Sensitivity analysis - gas gen. rate, material(concrete, host rock) properties
Temporal change of mass fraction of gas dissolved in groundwater at the seven monitoring points in the model domain
Gas Migration Study (On-going)
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Gas Migration Study (On-going) Sensitivity Analysis Results
Spatial distribution of mass fraction of gas dissolved in groundwater in the model domain after 1000 years of hydrogen gas generation: (a) Case 1: gas gen. rate x 2 (b) Case 2: hyd. cond. of concrete x 0.1, (c) Case 3: hyd. cond. of host rock x 2, (d) Case 4 : case1 + case.
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24-28 Nov., 2008The 2nd RCM, IAEA CRP
■ Concrete degradation factors considered
Sulfate and Mg Attack => Expansive Force, Crack and Spalling
Ca(OH)2 Leaching => reduce the pH, promote the corrosion of reinforcing steel
Alkali-Aggregate Reaction => Crack formation in concrete
Chloride Attack & Carbonation => Oxidation due to Cl ion penetration, Neutralization (pH 12 8), Enhancement of Ca(OH)2 leaching in low pH condition
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Degradation Modeling of Concrete Structure
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4th step
3rd step
2nd step
1st step
Concrete Neutralization
Corrosion
Cracking of Concrete
Depassivation
Carbonation
Chloride attack
Volume increase
Porosity and hydraulic
permeability increase
Above threshold
level
Phase 1Initiation period
Phase 2Propagation period
Corrosion of Reinforcing Steel
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24-28 Nov., 2008The 2nd RCM, IAEA CRP
Service Life Models
Diffusion Model => Migration of chemical species only by diffusion in concrete
Empirical Model => Empirical mathematical models (US DOE)
Reactive-Transport Model => Migration of chemical species by advection and dispersion
=> Complex chemical reaction models and thermodynamic data
KHNP-NETEC
Diffusion model and empirical model are considered in this stage.
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0
0.2
0.4
0.6
0.8
1
0 500 1000 1500 2000 2500 3000
Time (yr)
Ct/C
o
α=0.3
α=0.45
α=0.6
tD
xerfCtxC s
21),( Analytical solution of diffusion
equation
oo t
tDtD )(
Power function Phase I
■ Effect of α value on chloride diffusion in diffusion model
Evaluation of Concrete Degradation
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■ Corrosion Rate of Reinforcing Steel in diffusion model
Evaluation of Concrete Degradation
xd
tCDsremaining gwi
2
4.941100%
Corrosion rate of reinforcing
steel Phase II
99.99988
99.99992
99.99996
100.00000
100.00004
0 200 400 600 800 1000 1200 1400
Time (yr)
Reb
ar r
emai
ning
(%)
DO Conc.: 0.24 mg/L,
DO diffusion coeff.: 2×10-8 cm2/yr
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Evaluation of Concrete Degradation
■ Effect of w/c ratio in empirical model
0
2000
4000
6000
8000
10000
0 5 10 15 20 25 30 35 40 45
Concrete Thickness (cm)
Tim
e t
o O
nse
t o
f C
orr
osio
n (
yr)
w/c=0.5 w/c=0.45
w/c=0.3 w/c=0.15
42.0
22.1
])[/(54.2
129)(
Clcw
x
yrt
c
c
Corrosion onset time (Phase I)
10-5 m/yrCorrosion time (Phase II)
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24-28 Nov., 2008The 2nd RCM, IAEA CRP
Comparison of Silo Closure Option
■ 5 Option for a Silo Closure
■ Groundwater Flow Analysis – Regional & Local Models
■ Radionuclide Transport Assessment
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Silo Closure Option
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Crushed Rock
Cement MortarCrushed Rock
Bentonite
Crushed Rock Crushed Rock
Host Rock Host Rock
Host Rock Host Rock
Crushed Rock
Radioactive waste +
Crushed rock
Radioactive waste +
Crushed rock
Radioactive waste +
Crushed rock
Crushed Rock
Radioactive waste +
Crushed rock
CASE1-M1 CASE1-M2
CASE2-M1 CASE2-M3
Concrete Concrete
ConcreteConcrete
Bentonite(10%)+Sand(90%)
Host Rock
Crushed Rock
Radioactive waste +
Crushed rock
CASE2-M2
Concrete
24-28 Nov., 2008The 2nd RCM, IAEA CRP
Groundwater Flow Modeling - Regional
A A’
A A’
0.7
km
SILO
River boundary
General head Boundary
1.6
2k
m
2.18km
41.0m
48.2m
32.5m
25.5m41.5m
36.5m
19.3m
25.6m
Visual Modflow 3D
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Visual Modflow 3DVisual Modflow 3D
Concrete (width : 0.6~1.2m)
Inner (width: 0.2m)
Outer (width: 1.2m)
Radioactive waste + Crushed Rock (24mx24mx35m)
Crushed Rock (24mx24mx15m)
A A’
200m
200m
A A’
155m
Groundwater Flow Modeling - Local
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CASE1- M12.45E- 01
CASE1- M21.91E- 01
CASE2- M12.34E- 01
CASE2- M21.33E- 01
CASE2- M31.22E- 02
0.00E+00
5.00E- 02
1.00E- 01
1.50E- 01
2.00E- 01
2.50E- 01
3.00E- 01
CASE
Dar
cy V
elo
city
(m/y
ear)
CASE1- M11.06E- 03
CASE1- M28.18E- 04
CASE2- M11.61E- 04
CASE2- M21.10E- 03
CASE2- M34.95E- 05
0.00E+00
2.00E- 04
4.00E- 04
6.00E- 04
8.00E- 04
1.00E- 03
1.20E- 03
1.40E- 03
CASE
Dar
cy V
elo
city
(m/y
ear)
Intact ConcreteIntact Concrete After Fully DegradedAfter Fully Degraded
Option Intact Concrete After Fully Degraded
Case1_M1 1 1
Case1_M2 7.72E-01 7.81E-01
Case2_M1 1.50E-01 9.56E-01
Case2_M2 1.04E+00 5.41E-01
Case2_M3 4.33E-02 4.96E-02
Groundwater Infiltration into a Silo
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Radionuclide Transport Assessment
■ Reference Scenario
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■ Conceptual Model
■ Mathematical Modeling : Compartment model
■ Assessment Tool : MOSAIC developed by KHNP &
MSCI
The connection symbol “” denotes advective mass transfer, while the symbol “↔” denotes diffusive/dispersive mass transfer from one compartment to another compartment, respectively
Radionuclide Transport Assessment
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Comparison of NF Release Rate
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Thank you for your attention !