1. Development dynamic compartment models
to predict behavior of radionuclides
in rice paddy field
Tomoyuki TAKAHASHI
Kyoto University Research Reactor Institute
Osaka, Japan

2. My main experiences on development of dynamic compartment models
BIOMOVS II uranium mill tailings scenario (U-238 chain)
with Dr. Homma and Dr. Togawa (JAEA)
Transfer of tritium by river network at Toki site
with Dr. Yamanishi (NIFS)
Dr. Momoshima and Dr. Sugihara (Kyushu Univ.)
Behavior of radionuclides in rice paddy field
- Iodine, Cesium and Strontium
- Carbon-14 (EMRAS I)
with Dr. Uchida, Dr. Tagami, Dr. Ishii and Dr. Takeda (NIRS)
Dr. Yamamoto (Y first Inc.)
Dr. Tomita and Dr. Hayashi (V.I.C. Inc.)

3. BIOMOVS II uranium mill tailings scenario
(U-238 chain)
Source term:
- Groundwater release (leaching from tailings pile)
- Atmospheric release (dust and gas from tailings pile)
Dynamic compartment:
Vegetable land and pasture land
Deterministic analysis
-Time dependent annual total dose (each nuclides and total)
Probabilistic analysis
- Cumulative distribution functions of peak total dose
- Time dependent 90% confidence interval
- Statistical coefficients between variable parameters and peak total dose

4. River and sampling points of river waters in Toki area
Meeting point

5. Network of rivers assumed in the analysis
Basin
Toki river
C-2
B-1
B-1
C-1
Basin
B-3
Basin
F-3
F-1
A-2
A-1
F-2
A-3
Ikuta river
Tsumaki river
Downstream

6. Compartment models for basin and meeting point
(a) Basin
Rainfall
Evaporation
River water
of downstream
River water
Surface flow
Groundwater
Infiltration
A migration prediction code "MOGRA" was used
(b) Meeting point
River water of upstream
River water
of downstream
River water
River water of upstream

7. Measured and estimated tritium concentration
in river water and groundwater
Estimated concentration in groundwater at B-1 point
Estimated concentration in river water at B-1 point
Measured concentration in groundwater
Measured concentration at B-2 point
Measured concentration at B-1 point
Measured concentration at B-3 point

8. Behavior of radionuclides in rice paddy field Background and objectives
Reasonable dose assessment caused by nuclear facilities
Appropriate estimation of internal dose by the pathway of ingestion of rice which is a staple food in Asian countries
Prediction of behavior of radionuclides in rice paddy field
Development of dynamic compartment models for some
important radionuclides

9. Structure of compartment model for I, Cs and Sr
Air
Rain
Harvest
Outside
Deposition
Ear
Hull
Bran
Rice
Plowing
Translocation
Translocation
Leaf & stem
Leaf & stem
surface
Leaf & stem
internal
Leaf & stem
through
Outside
Weathering
Root uptake
Water
Volatilization
　　　　　　　　　　　　Surface water　　　　　　　　　　　
Outflow
Outside
Irrigation
Sorption & desorption
Sorption & desorption
Change
Soil (fast)
Soil (slow)
Plowing
Deeper zone
Infiltration
Infiltration

10. Growing curve of rice plant
Ishizuka & Tanaka (1953)
Total
Leaf & stem
WTotal
WLeaf =WTotal-WEar
Estimated parameters
Ear
K(d-1)
T1/2(d)
Wmax(g)
Total
0.06 54
12.3
Ear
0.09 66
7.1
WEar
Leaf & stem = Total - Ear
Growing curve

11. Development of a Dynamic Compartment Model for Prediction of Transfer of Carbon-14 to Rice Grains
14C is one of the most critical radionuclide for the safety assessment
- Nuclear fuel reprocessing plant
- Radioactive waste disposal plant
Developed a dynamic compartment model to predict 14C behavior
in rice paddy field and its concentration in rice grains
First step
The source term was considered as 14CO2
released into the atmosphere
Second step
The source term was considered as 14C
with the irrigation water

12. Structure of compartment model for 14C from the atmosphere
Inflow
Respiration
Air
Leaf & stem
organic
Ear
organic
Translocation
Respiration
Photosynthesis
Photosynthesis
Absorption
Plant inorganic
Exchange
Uptake
Release
Translocation
Revise to more appropriate
parameter values
Soil
Translocation
Outflow

13. Scheme of compartment model for 14C from the irrigation water
Respiration
Air nearby
rice plant
Respiration
Leaf & stem organic
Ear organic
Translocation
Photosynthesis
Photosynthesis
Absorption
Plant inorganic
Exchange
Source
Sink
Root uptake
Irrigation
Outflow
Exchange
Uptake
Irrigated water
Release
Volatilization
Exchange
Exchange
Exchange
Exchange
Soil 1
Soil 2
Mixture
Infiltration
Infiltration
Mixture
Outside
Air
Sink

14. Scheme of compartment model for 14C from the irrigation water
Respiration
Air nearby
rice plant
Respiration
Leaf & stem organic
Ear organic
Estimation of parameter values from batch experiment
with Dr. Uchida, Dr. Tagami, Dr. Ishii and Dr. Yamamoto
Translocation
Photosynthesis
Photosynthesis
Absorption
Plant inorganic
Exchange
Source
Sink
Root uptake
Irrigation
Outflow
Important pathway
Exchange
Uptake
Irrigated water
Release
Volatilization
Exchange
Exchange
Exchange
Exchange
Soil 1
Soil 2
Mixture
Infiltration
Infiltration
Outside
Sink

15. Estimation of transfer parameters between soil, water and air
Gas
Water
Soil
Soil/water
Distribution in each phase (%)
Conc. in soil / Conc. in water (mL/g)
days