Validation of Groundwater Flow Simulation Model by the ... · IAEA Technical Meeting on Surface...

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.


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


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


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


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


Legend

Quaternary


T3


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


Legend

Quaternary


T3

A (East) A’(West)


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


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)


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


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


Alternative stratum -5.00 -7.96


Fine-grained sandstone stratum -4.64 -4.64


Coarse-grained sandstone stratum -4.70 -4.70


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


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


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


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


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


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



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)



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


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)


Unit #4Unit #1

E-W

(m)

200m


Heat incinerator

Unit #2

Unit #3

Unit #4

N-S(m)

E-W

(m)

200m


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)


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


Sea side


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 ○ ○ ○ ○


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


91

-10

69

86

-13

65

-20

0

20

40

60

80

100


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


Ra

te o

f re

du

cti

on

of

infl

ow

ra

te in

to U

F

(%)

Committee model

JAEA model


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


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.


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

Validation of Groundwater Flow Simulation Model by the ... · IAEA Technical Meeting on Surface...

Documents

Transcript of Validation of Groundwater Flow Simulation Model by the ... · IAEA Technical Meeting on Surface...