Post on 14-May-2020
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 1 1
Validation of Groundwater Flow Simulation Model by the Committee
September 8-10th, 2014
Hiromitsu SAEGUSA
JAPAN ATOMIC ENERGY AGENCY
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 2
Aim & action
Aim
To validate the groundwater (GW) flow model, which has
been constructed by the committee on countermeasures for
contaminated water treatment.
Action
Additional GW flow analysis has been performed by JAEA
to estimate GW flow condition before and after
implementation of the countermeasures.
The consistency of analytical results from committee and
JAEA models has been confirmed.
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 3
Contents
Area setting for the modeling
Geological modeling
Hydrogeological modeling (Modeling the hydraulic conductivity field)
GW flow analysis (3-D steady state analysis under saturated and unsaturated conditions)
Before implementation of countermeasures
After implementation of countermeasures
Comparison between the analytical results from Committee and JAEA models
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 4
Area setting
2 km
Abukuma Mountains
Futaba Fault
Abukuma Mountains
1F
1 km
4 km
6 km
Model Focused GW flow system
Committee model Shallow GW flow
JAEA nested model*
Site model Shallow to deep GW flow
Regional model
*To confirm an influence of regional GW flow on GW flow on 1F site
Site area
Committee model
Regional area
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 5 5
Geological modeling
Geological model(Horizontal plane)
Alluvium
Terrace deposit
Sandstone stratum
Mudstone stratum
Alternate stratum
Tomioka stratum ---T2
Legend
500m
A
A’
B
B’
C C’
North-South(m)
We
st-E
ast
(m) Committee model
JAEA model (site area) Unit #1
Unit #2
Unit #3
Unit #4
Sea side
Quaternary
Pliocene/ Tomioka stratum
Geological model was constructed based on the data provided by TEPCO
Process build.
Heat incinerator
T3
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Geological modeling
A-A’ cross section through Unit #1 building
A (East) A’(West) B (East) B’ (West)
C (North) C’(South)
Sea side Sea side
C-C’ cross section
B-B’ cross section through Unit #4 building
Alluvium
Terrace deposit
Sandstone stratum
Mudstone stratum
Alternate stratum
Tomioka stratum ---T2
Legend
Quaternary
Pliocene/ Tomioka stratum
T3
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Medium-grained sandstone stratum
Fine-grained sandstone stratum
Coarse-grained sandstone stratum
Alluvium Terrace deposit
Mudstone stratum
Tomioka stratum (T2)
Geological modeling
Sea side
Sea side
A-A’ cross section through Unit #1 building
Alluvium
Terrace deposit
Sandstone stratum
Mudstone stratum
Alternate stratum
Tomioka stratum ---T2
Legend
Quaternary
Pliocene/ Tomioka stratum
T3
A (East) A’(West)
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Hydrogeological conceptual model
Medium-grained sandstone stratum (Unconfined aquifer)
Fine-grained sandstone stratum (Confined aquifer)
Coarse-grained sandstone stratum (confined aquifer)
Alluvium Terrace deposit (Unconfined aquifer)
Mudstone stratum
Tomioka stratum (T2)
Sea side
In 1F site, unconfined and confined aquifers are distributed, and divided by low permeable mudstone stratum
GW in unconfined aquifer mainly affects inflow volume into the underground facilities (UFs)
Origins of GW in unconfined and confined aquifers are estimated to be precipitation in 1F site
A (East) A’(West)
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Hydrogeological modeling
Hydrogeological model was constructed based on the geological model using integrated system for geological modelling and GW flow simulation (GEOMASS system; Ohyama and Saegusa, 2008)
Spatial discretization
Whole of the model: 50m×50m×20m
Area containing the unit 1-4 buildings(2km×3.5km): 25m×25m×20m
Ground surface to EL -30m: 1m thickness to model continuity the aquifers
Hydraulic conductivity (Log[K] (m/s))
Hydrogeological model
Number of grids: 658,092
Sea side
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Hydrogeological modeling -Hydraulic parameters-
Geological units
Hydraulic conductivity (Log[K] (m/s))
Horizontal Vertical
Terrace deposit -4.52 -4.52
Alluvium -5.00 -5.00
Medium-grained sandstone stratum -4.52 -4.52
Medium-grained sandstone stratum (south area and upper part) -6.00 -6.00
Mudstone stratum -7.96 -7.96
Medium-grained sandstone stratum (south area and lower part) -6.00 -6.00
Mudstone stratum -7.96 -7.96
Alternative stratum -5.00 -7.96
Mudstone stratum -7.96 -7.96
Fine-grained sandstone stratum -4.64 -4.64
Mudstone stratum -7.96 -7.96
Coarse-grained sandstone stratum -4.70 -4.70
Mudstone stratum -7.96 -7.96
Tomioka stratum (T2) -6.10 -6.10
Hydraulic parameters were assigned as same as Committee model
K of Tomioka stratum was assigned based on literature information
Hydraulic parameters
Same as Committee model
Major Aquifer / Impermeable stratum
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Hydrogeological modeling -underground facility-
UFs, where GW inflow are occurred, were modeled
UFs were modeled as quadrangular prism with equivalent area with actual area
Boundary conditions of walls of UFs: seepage condition
※Skin effect factor “α” was applied to be taken into account concrete wall of the UF
・K of the concrete wall (Kwall)=K of geological stratum vicinity of the UF (Krock)×α
Unit #1
Unit #2
Unit #3 Unit #4
Process build.
Heat incinerator
Underground facility (Atmospheric
condition) Reduction of K
Sea side
Reduction of K
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 12 12
Boundary conditions
Side boundaries (land area); constant head from result of GW
flow analysis on regional area
Bottom boundary; No-flow
Top and side boundaries (sea area); constant head (Head: 0m)
Head dist. from GW flow analysis on regional area
Recharge rate: 55% of annual precipitation (1,545mm/year)
Top boundary (land area); constant recharge rate
(850mm/year)
Different condition from Committee model
Same condition as Committee model
Sea side
Sea side
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 13
GW flow analysis after implementation of countermeasures
GW flow analysis before implementation of countermeasures
Procedure for GW flow analysis
Adjusting of the skin effect factors
Comparison between measured and modeled
inflow rate into UFs
Assignment of hydraulic parameters
GW flow analysis
Comparison between measured and modeled
GW level ★
Re-assignment of hydraulic parameters and boundary
conditions taking into account the countermeasures
GW flow analysis
Good
Good
N.G.
N.G.
Calculation of inflow rate into UFs
Calculation of inflow rate into UFs with countermeasures
Estimation of effectiveness of the countermeasures★
★ Items for model comparison
UF Inflow
GW table
UF
Inflow
GW table
GW table is to be calculated based on the K field and water balance among recharge, discharge and inflow into UFs
Wall
Before
After
Image of GW flow analysis
Assignment of boundary conditions
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 14
Comparison items
GW flow analysis before implementation of countermeasures
GW table:
To validate the hydrogeological model (K field) and boundary conditions
GW flow analysis after implementation of countermeasures
Rate of reduction of inflow rate into UFs:
To validate result of estimation of effectiveness of the countermeasures
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 15
313
88
401
320
85
406
0 0
400
0
50
100
150
200
250
300
350
400
450
500
Units #1- #4 Others Total
Infl
ow
rat
e (
m3
/day)
Committee model
JAEA model
Measured
Results of GW flow analysis (before)
“Others” contains Heat incinerator and Process building
Inflow rate into UFs
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 16
Results of GW flow analysis (before)
JAEA model could simulate GW table distribution before implementation of countermeasures
Measured vs modeled GW levels Committee model vs JAEA model
Results from Committee and JAEA models are consistent
0
5
10
15
20
25
30
35
40
0 5 10 15 20 25 30 35 40
Mo
de
led
GW
leve
l (m
)
Measured GW level (m)
Unconfined GW table (Medium-grained sandstone layer)
Confined GW table (Alternative layer)
0
5
10
15
20
25
30
35
40
0 5 10 15 20 25 30 35 40
GW
leve
l fro
m J
AEA
mo
del
(m
)
GW level from Committee model (m)
Unconfined GW table (Medium-grained sandstone layer)
Confined GW table (Alternative layer)
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 17 17
Results of GW flow analysis (before)
全水頭(m)
全水頭(m)Sea side
Sea side
Head distribution (ground surface)
Head distribution (EL-10m)
500m
N-S(m)
E-W
(m)
Area around reactor and turbine buildings
Sea side
500m
N-S(m)
E-W
(m)
Area around reactor and turbine buildings
N-S(m)
E-W
(m)
200m
Unit #1 Process build.
Heat incinerator
Unit #2
Unit #3
Unit #4
E-W
(m)
200m
Unit #1 Process build.
Heat incinerator
Unit #2
Unit #3
Unit #4
Head (m) GW flow is affected by detail topographic
undulation
GW flow is affected by regional topography (from west to east)
N-S(m)
Sea side Sea side
Sea side
Head (m)
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 18 18
Unit #4Unit #1
E-W
(m)
200m
Unit #1 Process build.
Heat incinerator
Unit #2
Unit #3
Unit #4
N-S(m)
E-W
(m)
200m
Unit #1 Process build.
Heat incinerator
Unit #2
Unit #3
Unit #4
Horizontal plane
全水頭(m)
Cross section
Sea side
Sea side
(Black line shows boundary of geological stratum)
Results of GW flow analysis (before)
Sea side
Sea side
Head (m)
Head distribution (ground surface)
Head distribution (EL-10m)
N-S(m)
Major GW flowing through around UFs recharges at terrace located west of UFs and discharges at coastal line
Medium-grained sandstone stratum(Aquifer)
Fine-grained sandstone stratum
Coarse-grained sandstone stratum
Alluvium Terrace deposit (Aquifer)
Mudstone stratum
Tomioka stratum (T2)
Sea side
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 19
JAEA model cases
Case ID for JAEA
model
Land-side frozen soil impermeable walls
around buildings (Units #1 to #4)
Sea-side impermeable walls
Pumping up GW from wells near
buildings (sub-drain)
Pumping up GW on the mountain side
of the buildings (GW bypassing)
Case A - - - -
Case B-1 ○ - - -
Case B-2 ○ ○ ○ ○
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 20
JAEA modeling method for the countermeasures
Countermeasures Modeling method
Land-side frozen soil impermeable walls around buildings
Installing walls from ground-surface to EL.-25m (covering aquifers) log[K(m/s)]=-20 (No-flow)
Sea-side impermeable walls Installing walls from ground-surface to EL.-25m (covering aquifers) log[K(m/s)]=-7
Pumping up GW from wells near buildings (sub-drain)
Constant head boundary at 51 sub-drains Head = bottom of sub-drain
Pumping up GW on the mountain side of the buildings (GW bypassing)
Constant head boundary at 12 wells Head = bottom of wells
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 21
91
-10
69
86
-13
65
-20
0
20
40
60
80
100
Units #1- #4 Others Total
Rate
of
red
ucti
on
of
infl
ow
ra
te in
to U
F
(%)
Committee model
JAEA model
Cas
e B
-1
Cas
e B
-2
Effectiveness of the countermeasures
“Others” contains Heat incinerator and Process building
Increasing inflow into the building outside of land-side impermeable walls
100
16
81
98
23
82
0
20
40
60
80
100
Units #1- #4 Others Total
Ra
te o
f re
du
cti
on
of
infl
ow
ra
te in
to U
F
(%)
Committee model
JAEA model
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 22
1号機Unit #1
Land-side
wall
1号機Unit #1Sea-side
wall
Land-side
wall
Unit #1
Results of GW flow analysis (after)
Case A Case B-1
Case B-2
全水頭(m)Head (m)
GW flow around buildings is much inhibited by land-side wall
GW flow direction is changed to upward inside of land-side wall (possibility of contaminated shallow GW flowing downward is not to be considered)
After installing sea-side wall, GW flowing toward sea is inhibited and GW flows upward around coastal line
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 23
Conclusion
The analytical results from Committee model are consistent with JAEA’s results, although…
larger region is considered to implement an alternative boundary conditions and,
different numerical modeling and solving method is applied.
The confidence of Committee’s analytical results can be presented.
IAEA Technical Meeting on Surface Water and Groundwater Contamination Following the Accident at the Fukushima Daiichi Nuclear Power Plant 24
JAEA’s additional contribution
1 km
GW flow
Sea Water Flow inside Port
UF
Inflow
GW table
Sea water flow inside port
GW flow
GW discharge distribution, which is output from GW flow analysis, is to be input to numerical analysis of sea water flow inside port
Example of GW discharge distribution
Development of methodology for sequential flow modeling from GW to sea water
GW discharge