Transcript Slide 1

RESEARCH AND DEVELOPMENT OF
ENVIRONMENTAL TRITIUM MODELLING
Dan Galeriu, Anca Melintescu
TRITIUM 2010, 24-29 October 2010, Nara, Japan
Time past and time future
What might have been and what has been
Point to one end, which is always present
T.S. Eliot: Burnt Norton (I), Four Quartets (1943)
WHY?
CANDU Reactors in Romania
The future Fusion Reactor
TRITIUM - LOW risk, but how low?
Dose coefficients and
radio toxicity → tritium is good
The AIKEN list (1990) →
Tritium is not well handled
THE CONTEXT ON INCREASED INTEREST FOR
TRITIUM
•
Greenpeace actions in Canada, UK, Romania, Japan
•
Groundwater tritium near nuclear reactors (USA, Canada)
•
The need to preserve public trust in nuclear energy
•
EU Scientific Seminar “Emerging Issues on Tritium and Low Energy
Beta Emitters” (Luxemburg, 13 November 2007)
•
Canadian Nuclear Safety Commission: Tritium Studies Project (20072010) → Environmental Fate of Tritium in Soil and Vegetation
•
Autorite de Surete Nucleaire (France) → Livre Blanc TRITIUM (20082010)
•
International Atomic Energy Agency- EMRAS program , Phase I and II
Environmental Modelling for Radiation Safety
•
Working Group 2 - Modelling of Tritium and Carbon-14 transfer to biota and
man working group
•
Working Group 7 – "Tritium" Accidents (on going)
TRITIUM and the ENVIRONMENT
SOURCES MEASUREMENT and TRANSFER
Ph GUETAT, CEA
Thanks for their help to C Douche, JC Hubinois, N. Baglan ,
D Galeriu, Ph. Davis, W Raskob
*************************************
The levels specified for tritium in CODEX Alimentarius levels for radionuclides
in foods contaminated following a nuclear or radiological emergency for use in
international trade were derived generically for application to low energy beta
emitters as a group. Significantly, different levels could result had they been
derived explicitly for tritium. Given the ubiquitousness of tritium and its
increasing importance in the context of fusion energy, consideration should be
given to tritium being addressed explicitly in any future revision of CODEX
Alimentarius – and of Euratom Council Regulation laying down maximum
permitted levels of radioactive contamination of foodstuffs and of feeding
stuffs following a nuclear accident or any other case of radiological
emergency.
CEA/DAM/VA UE Scientific Seminar on Emerging Issues on Tritium
Canadian and French conclusions
(routine emissions)
•
OBT activities measured in soils and plants have significantly higher variability than the
corresponding HTO concentrations, and the OBT/HTO ratios for soils, plants and animal products
have large variations;
•
Near nuclear sites, the average OBT/HTO ratios are a factor 2-3 for plant products and 10 for
animal products. These ratios are significantly higher than those predicted by the current
physiological models of HTO and OBT behaviour in plants and animals; it seems that imported
feed from areas contaminated with high tritium levels is an explanation for such OBT/HTO ratios
in animal products;
•
There is a need for a relatively simple dynamic model for OBT formation and retention in an
environment subject to fluctuating HTO concentrations, as it is encountered in practice;
•
An age dependent biokinetic model for the OBT retention should be developed for infants, children
and adults, which accounts for physiological and anatomical variation with age;
•
OBT levels in river sediments are always larger than those in plants and fish, which themselves are
larger than HTO concentrations in river water. This clearly demonstrates the existence of OBT
pools in the environment with slow turnover rates and low bioavailability;
•
High OBT in soil is not a significant secondary source of tritium, even for humic soils with a large
decomposition rate of OBT;
•
The case of high OBT in fish (in Cardiff Bay, for example) needs more clarification and the effect of
organic precursors must be studied;
•
The state of modelling reflects the present knowledge and more efforts must be done concerning
the OBT.
Tritium results in EMRAS I
Modelling of Tritium and Carbon-14 transfer to biota and man working group
The activities of the WG focused on the assessment of models for organically
bound tritium (OBT) formation and translocation in plants and animals, the
area where model uncertainties are largest. Environmental 14C models were
also addressed because the dynamics of carbon and OBT are similar
The uncertainty in the predictions of environmental tritium and 14C models can
be reduced by:
•
Ensuring that the air concentrations used to drive the models are of high quality and
match the resolution and averaging requirements of the scenario. Performance was
better for models that were driven by air concentrations averaged over the OBT or
14C residence time in the compartment of interest;
•
incorporating as much site-specific information as possible on land use, local soil
properties and predominant plant cultivars and animal breeds;
•
implementing realistic growth curves for the plant cultivars of interest;
•
basing all sub-models on the physical approaches available for the disciplines in
question. For example, knowledge from the agricultural sciences should be used to
improve models for crop growth, photosynthesis and translocation;
•
recognizing and accounting for any unusual conditions (water stress, an uncommon
cultivar or breed) in the model application.
IAEA EMRAS I, WG2 - 3H &14C
Scenario
Type
Scenario Leaders
Participants
Soybean
H-3, Accidental, soybean plant
KAERI Korea
Perch Lake
H-3 Routine, aquatic
AECL Canada
Russia, France, Germany, Romania,
Japan, UK, Lithuania
Pickering
H-3 Routine, terrestrial
AECL Canada
Germany, USA, Lithuania, UK,
Romania, Japan, France
Pine tree
H-3, routine, tree, groundwater
NIRS Japan
Japan, USA, Romania, France
Rice
C-14, routine, rice
JAEA Japan
Canada, France, Romania, Japan
Hypothetical
H-3, accidental, terrestrial
CEA France
Canada, Romania, Korea, Japan,
France, Germany, India
Mussel
H-3, accidental, aquatic - mussel
AECL Canada
Germany, France, Japan, Romania
C-14 potato
C-14, accidental, potato plant
NIPNE Romania
France, UK, Romania, Japan
Pig
H-3 (OBT) - complex - pig
NIPNE Romania
Japan, Romania, France, Canada, UK
Canada, France, Germany, Japan,
Korea, Romania, Russia, UK, USA
Modelling the transfer of 3H and 14C into the environment - lessons learnt from IAEA’s
EMRAS project, A. Melintescu, D. Galeriu, Radioprotection, Vol. 44, No. 5, (2009), 121 – 127
IAEA Technical Reports Series No. 472
Handbook of Parameter Values for the
Prediction of Radionuclide Transfer in
Terrestrial and Freshwater Environments
Chapter 10. SPECIFIC ACTIVITY MODELS AND PARAMETER VALUES FOR
TRITIUM, 14C AND 36Cl
incorporate:
Modelling H-3 and C-14 transfer to farm animals and their products
under steady state conditions
D. Galeriu, A. Melintescu, N.A. Beresford, N.M.J. Crout, R. Peterson H. Takeda
Journal of Environmental Radioactivity, 98 (2007) 205 - 217
IAEA-EMRAS II (on going, 2009 - 2012)
Reference Approaches for Human Dose Assessment
Working Group 7 “Tritium” Accidents
Aims and Objectives:
• To develop a standard conceptual dynamic model for tritium dose
assessment for acute releases to atmosphere and water bodies;
• To start to develop a new model for any air or water concentration
(HT or HTO) and the duration of the exposure - The operational
model will be developed by each major user considering available
best Atmospheric Transport Models for the site in question;
• To agree on common sub-models, based on understanding of the
processes and agreed key parameters (interdisciplinary approach),
based on recent findings in Life Sciences;
• To define the framework for an operational model;
• To obtain quality assured sub-models and harmonize approaches in
order to get confidence in the predictions (moderate conservatism);
• To have capability to assimilate real data from measurements
Task groups and few results
Task Group I – Wet deposition
•
Sensitivity analysis of rain characteristics on HTO concentration in drops, L.
Patryl, D. Galeriu, P. Armand, L. Vichot, Ph. Guétat, this conference
•
Rain scavenging of tritiated water vapour: A numerical Eulerian stationary
model, D. Atanassov, D. Galeriu, J. Environ. Radioact.,
doi:10.1016/j.jenvrad.2010.09.001
•
Tritium profiles in snowpacks, D. Galeriu, P. Davis, W. Workman, J. Environ.
Radioact., 101 (10), p. 869-874, October 2010
Task Group II Aquatic pathways (EDF,IFIN, Brazil)
•
•
Modelling tritium flux from freshwater to atmosphere: application to the Loire
river, L. Marang, F. Siclet, et al., this conference
Organically bound tritium in freshwater ecosystems : long term trends in the
environment of nuclear power stations, F. Siclet, G. Gontier, this conference
Task Group III - Terrestrial pathway (atmospheric source)
• All WG 7 participants
• P. Guetat, P. Cortez, N. Momoshima, A. Melintescu, L. Patryl, L. Vichot, S.B.
Kim, V. Korolevich – papers at this conference
Hydrological model for tritium dispersion after a release of 37 PBq
Dispersion of HTO plume after 3 days following the accident in the scenario 1
F. Lamego, Institute of Nuclear Engineering, Rio de Janeiro, Brazil
Regulatory requirements for a model
•
•
•
•
Relatively simple;
Transparent ;
Easy to program;
Results should be conservative (but not too
much);
• Deterministic calculations possible (worst case
assessments);
• Probabilistic calculations possible (95%
percentile as worst case);
• Is this possible for Tritium?
Tritium Modelling Overview, W. Raskob, EMRAS January 2010
How to obtain an useful model?
SPECIFIC CAUSES OF UNCERTAINTY
Simple model - Keum et al.,
Health Physics, January 2006,
Volume 90, p.42
Very complex model,
M. Ota &H. Nagai, EMRAS WG 7
presentation
- Missing communication;
- Experiments and OBT modelling at AECL undisclosed;
- Cardiff case - experiments - undisclosed (but
reports from Environmental Agency and FSA
are available on request);
- Many reports, PhD thesis difficult to access or
delayed for accessing;
- Incomplete documentation – ignoring past
achievements (BIOMOVS, EMRAS I, selective
uptake of DOT);
- No common knowledge data base due to
copyright restriction;
- Missing appreciation – S Strack case - lost
information for T in wheat;
- Limits in allocation of time and budget
- Missing dedication - only a job
- Missing peer review
- Insufficient parameter uncertainty
Overview
of ETMOD and Environmental Tritium Research
September 28-29, 2009
Ph.D. S.B. Kim
Research Scientist
Environmental Technologies Branch
Chalk River Laboratories
Chalk River, Ontario
Canada
UNRESTRICTED / ILLIMITÉ
S. Strack, Experiments with Tritium in Wheat
Vergleich OBT Feld-6
250
25 MBq
200
26.06.1995
22d nach Blüte
23:00 - 24:00 Nacht
T = 17°C
r.F. = 89 %
PPFD = 0 µmol/m²s
A(außen)= -0,7 µmol CO2/m²s
rel.TWT-Aufn.Bl.= 18 %
rel.OBT-Einb.Bl.= 0,44 %
Bq/g
150
100
50
0
1
10
100
time after exposure (h)
leaf measured
leaf calculated
1000
List of publications related to D2O experiments
•
•
•
•
•
•
•
•
•
•
•
Deposition of D2O from air to plant and soil during an experiment of D2O vapor release into a vinyl house,
Mariko Atarashi, Hikaru Amano, Michiko Ichimasa, Yusuke Ichimasa, Fusion Engineering and Design 42
(1998) 133–140
Formation and retention of organically bound deuterium in rice in deuterium water release experiment, M.
Atarashi-Andoh, H. Amano, H. Kakiuchi, M. Ichimasa and Y. Ichimasa, Heaoth Physics, 82, 863-868 (2002).
Uptake of heavy water vapor from atmosphere by plant leaves as a function of stomatal resistance, M.
Atarashi, H. Amano, M. Ichimasa, M. Kaneko and Y. Ichimasa, Proceedings of International Meeting on
Influence of Climatic Characteristics upon Behavior of Radioactive Elements, Rokkasho, Aomori, Japan,
October 14-16, 1997, Edited by Y. Ohmomo and N. Sakurai, IES, 236-242 (1997).
Conversion rate of HTO to OBT in plants, M. Atarashi-Andoh, H. Amano, M. Ichimasa and Y. Ichimasa,
Fusion Science and Technology, 41, 427-431 (2002).
Uptake kinetics of deuteriated water vapor by plants: Experiments of D20 release in a greenhouse as a
substitute for tritiated water, N. Momoshima, H. Kakiuchi, T. Okai, S. Yokoyama, H. Noguchi, M. Atarashi, H.
Amano, S. Hisamatsu, M. Ichimasa, Y. Ichimasa, Y. Maeda, Journal of Radioanalytical and Nuclear
Chemistry, Vol. 239, No. 3 (1999) 459-464
Uptake of deuterium by dead leaves exposed to deuteriated water vapor in a greenhouse at daytime and
nighttime, N. Momoshima, R. Matsushita, Y. Nagao and T. Okai, J. Environ. Radioactivity,88, 90-100 (2006).
Organically bound deuterium in soybean exposed to atmospheric D2O vapor as a substitute for HTO under
different growth phase, M. Ichimasa, T. Maejima, N. Seino, T. Ara, A. Masukura, S. Nishihiro, H. Tauchi and
Y. Ichimasa, Proceedings of the International Symposium: Transfer of Radionuclides in Biosphere –
Prediction and Assessment-, Mito, December 18-19, 2002, JAERI-Conf 2003-010, 226-232 (2003).
Heavy water vapor release experiment in a green house –Transfer of Heavy water to tomato and dishcloth
gourd—, M. Ichimasa, T. Hakamada, A. Li, Y. Ichimasa, H. Noguchi, S. Yokoyama, H. Amano and M.
Atarashi, Proceedings of International Meeting on Influence of Climatic Characteristics upon Behavior of
Radioactive Elements, Rokkasho, Aomori, Japan, October 14-16, 1997, Edited by Y. Ohmomo and N.
Sakurai, IES, 243-248 (1997).
Organically bound deuterium in rice and soybean after exposure to heavy water vapor as a substitute for
tritiated water, M. Ichimasa, C. Weng, T. Ara and Y. Ichimasa , Fusion Science and Technology, 41, 393-398
(2002).
Deposition of heavy water on soil and reemission to the atmosphere, Sumi Yokoyama, Hiroshi Noguchi,
Michiko Ichimasa, Yusuke Ichimasa, Satoshi Fukutani, Fusion Engineering and Design 42 (1998) 141–148
Re-emission of heavy water vapor from soil to the atmosphere, S. Yokoyama, H. Noguchi, Y. Ichimasa and
M. Ichimasa, Journal of Environmental Radioactivity, 71, 201-213 (2004).
N. Momoshima, WG 7, Paris meeting Sept 2009
Role of plant growth processes and physiology (14C example)
Gross photosynthesis
Assimilate accumulation
Growth and maintenance
Respiration
Partition to plant parts
Role of reserves
DEVELOPMENT STAGE
GP*Yo
grain
gresp
assim
Struct.
assim
body
reserve
maintenance
root
0.045
0.04
Rice, Japan
Controlled experiment B. Tani et al., IES 2007
Model for close genotype and Tokaimura weather
SAR ratio of specific activity
Specific activity of 14C (14C/total C, Bq/g C) in
the edible part of crops
specific activity of 14C in air (Bq/g C)
SARTANI
0.035
SARMY
SAR(grain/air)
0.03
0.025
0.02
0.015
0.01
0.005
0
-60
-10
40
DRA (d)
90
Land surface model SOLVEG2
OBT formation and translocation
19/18
Carbohydrate formation and translocation processes
based on experimental result (Fondy & Geiger 1982)
Daytime
Nighttime
CO2 assimilation rate An
OBT formation: EAn
1.00EAn
0.48EAn
sucrose
0.46EAn
OBT decomposition: ERd
0.26EAn
intermediates
Respiration rate Rd
structural
1.00ERd
intermediates
structural
0.19EAn
4.58ERd
starch
sucrose
starch
Translocation
5.23ERd
Translocation
Haruyasu Nagai, Masakazu Ota
7.07ERd
Heat and life: The ongoing scientific
odyssey (key for OBT in animals)
• The technocratic model stresses mind-body
separation and sees the body as a machine;
• The humanistic model emphasizes mind-body
connection and defines the body as an
organism;
• The holistic model insists on the oneness of
body, mind, and spirit and defines the body as
an energy field in constant interaction with other
energy fields.
Animals bioenergetics
•
•
•
•
•
•
•
•
Review of past results of 3H and 14C transfer
modelling in mammals → necessity to have
a common approach based on energy needs
and on the relation between energy and
matter Knowledge on animal metabolism
and nutrition
Metabolism = countless chemical processes
going on continuously inside the body that
allow life and normal functioning
These processes require energy from food
Gross energy, Digestible energy,
Metabolisable Energy, Net energy
Maintenance metabolism (basal+heat of
digestion), lost as heat
Heat needed for cold thermogenesis, activity
and losses in processes of growth,
production and reproduction
Energy stored (deposited, retained) in the
products of growth, lactation (egg) and
reproduction
Daily Energy Expenditure (Field Metabolic
Rate)
1 dE
1 dM



E dt
M dt
E=mc2 →
GE in food
GEf
DE
GEug
ME
Basal Met.
Maint. Met.
Heat of Dig.
Cold Therm.
Used for work,
Growth, re-prod
NE
The mean value of θ −1 gives the mean
residence time of chemical elements in the
living body
MAGENTC - MAmmal GENeral Tritium and Carbon transfer
• Complex dynamic model for H-3 and C-14 transfer in mammals, description in:
D. Galeriu, A. Melintescu, N. A. Beresford, H. Takeda, N.M.J. Crout, “The Dynamic transfer of
3H and 14C in mammals – a proposed generic model”, Radiat. Environ. Biophys., (2009) 48:29–
45
A. Melintescu, D. Galeriu Energy metabolism used as a tool to model the transfer of 14C and 3H
in animals Radiat. Environ. Biophys.(2010), DOI: 10.1007/s00411-010-0302-4
- 6 organic compartments;
- distinguishes between organs with high
transfer and metabolic rate (viscera),
storage and very low metabolic rate
(adipose tissue), and ‘muscle’ with
intermediate metabolic and transfer rates;
- Blood - separated into RBC and plasma
(plasma is the vector of metabolites in the
body and also as a convenient bioassay
media);
-The remaining tissues - bulked into
“remainder”;
- All model compartments have a single
component (no fast-slow distinction)
Model tests with experimental data - NO calibration (rat, cow, sheep, pig)
Complete database for 3H and 14C transfer, obtained from experiments with Wistar strain rats
thanks to H. Takeda (NIRS, Japan)
continuous 98 days intakes of 14C and OBT contaminated food or HTO;
acute intakes of HTO or 14C and 3H labelled glucose, leucine, glycine, lysine, and oleic
and palmitic acids.
Available data include 14C, OBT and HTO measurements in visceral organs, muscle, adipose
tissue, brain, blood and urine.
Average and standard deviation of predicted to observed ratios in rat viscera, muscle, blood,
adipose tissue and whole body (except bone and skin) for the six forms of intake
Organ
14C
chronic
14C
acute
OBT chronic
OBT acute
HTO chronic
HTO acute
Viscera
1.12 ± 0.15
0.51 ± 0.4
1.06 ± 0.15
0.67 ±
0.56
0.43 ± 0.07
0.87 ± 0.34
Muscle
1.25 ± 0.14
0.81 ±
0.29
1.23 ± 0.21
0.90 ±
0.37
0.40 ± 0.09
1.02 ± 0.38
Adipose
1.11 ± 0.15
0.61 ±
0.12
0.97 ± 0.2
0.75 ±
0.13
0.3 ± 0.1
1.33 ± 0.3
Whole blood
1.12 ± 0.27
0.4 ± 0.1
0.88 ± 0.12
0.38 ±
0.03
0.37 ± 0.09
0.62 ± 0.18
Whole-body
1.18 ± 0.08
0.7 ± 0.1
1.08 ± 0.11
0.8 ± 0.1
0.36 ± 0.08
1.09 ± 0.18
Mass dependence (relative units) for viscera mass fraction, specific metabolic rates SMR ((MJ kg-1day-1) and partition fractions for maintenance metabolic energy of
growing ruminants
Specific metabolic rate (MJ kg-1day-1)
Partition fraction maintenance metabolism
liver
Liver+PDV
Adipose
Relative
body weight
(EBW/SRW)
Viscera
mass
fraction
normalized
to EBW
0.07
0.09
1.5
0.77
0.24
0.98
0.006
0.2
0.11
NA
NA
NA
NA
0.3
0.12
NA
NA
NA
0.41
NA*
NA
NA
0.48
NA
2.9
0.64
NA
0.77
1
PDV
HQ
viscera
muscle
remainder
0.47
0.42
0.104
0.023
0.61
0.27
0.097
NA
0.04
0.61
0.31
0.04
NA
NA
0.068
0.61
0.27
0.052
0.47
0.1
0.83
0.094
0.6
0.27
0.036
2.6
0.36
0.088
0.66
0.13
0.55
0.29
0.042
NA
2.4
0.3
0.084
0.55
0.15
0.5
0.31
0.04
0.08
NA
NA
NA
NA
0.19
0.47
0.3
0.04
Tests with growing pigs and veal
Few experiments
1. Pigs of 8 weeks old fed for 28 days with HTO:
Muscle P/O ~ 1
Viscera P/O ~1
2. Pigs of 8 weeks old fed for 28 days with milk powder contaminated with OBT:
Muscle P/O ~ 3
Viscera P/O ~ 2
3. Pigs of 8 weeks old fed for 21 days with boiled potatoes contaminated with
OBT:
Not quite sure about these values → Potential
Muscle P/O ~ 0.2
explanation: old and insufficiently reported
Viscera P/O ~ 0.3
experimental data
4. Two calves of 18 and 40 days old, respectively fed for 28 days with milk
powder contaminated with OBT:
Muscle P/O ~ 1
Viscera P/O ~ 2.5
Short term dynamics of 14C in whole body (generalised coordinates) - Wild animals
norm whole conc
lemming
chipmunk
chipmunkC
rabbit
redfox
reddeer
0.1
0.01
1
2
3
4
5
6
7
8
9
10
T*RMR
Generalised coordinates:
Normalised concentration=Whole body conc *Mature mass
T*RMR – non-dimensional time = time * mature RMR
Despite these shortcomings, the results presented above are less uncertain than
for many other radionuclides and can provide useful results for biota radioprotection.
Extension to birds - application to broiler
Transfer factor for tritium in broiler
Concentration ratio for tritium in broiler
100
1
OBT (HTO)
T (HTO)
OBT (OBT)
T (OBT)
Concentration ratio
Transfer factor (1/kg)
10
1
OBT (HTO)
0.1
T (HTO)
OBT (OBT)
T (OBT)
0.1
0.01
0.01
0
20
40
60
80
Time (d)
100
120
140
160
0
20
40
60
80
100
120
140
160
Time (d)
In the case of fast growing broiler, at the market weight of about 2 kg (42 days old) the model
predicts lower transfer factors (TF) than for the equilibrium case
The predicted concentration ratios (CR) for our fast growing broiler are close to those
obtained for “equilibrium” .
In absence of any experimental data or previous modelling assessments, our results give
a first view on the transfer of 3H and 14C in birds.
CONCLUSIONS - MAGENTC
• The model is apparently research grade, but it is tested
with experimental data without calibration;
• It is continuously improved in parallel with literature
search on animal nutrition and metabolism;
• Input parameters need only a basic understanding of
metabolism and nutrition and the recommended values
can be provided;
• Results give arguments for distinction between
subsistence and intensive farming (observed also for Cs137 post-Chernobyl);
• Model provides robust results for all intake scenarios of
interest
AQUAtic TRITium, an update (in reply to Livre Blanc Tritium)
The models used in 1980s were based on the assumption that the OBT SA in fish
is directly linked with the HTO in water or the OBT in fish food →
fully valid if the water contamination is due only to an initial HTO source → CF ≤ 1
CF = concentration per unit mass of biota at equilibrium /
dissolved concentration per unit volume in ambient water
CFs in marine biota at Cardiff Bay (UK) much higher in flounder and mussels (McCubbin et
al., 2001; Williams et al., 2001)
CFs ≥4 × 103 (fw equivalent) → attributed to uptake of tritium in organically bound forms,
due to the existence of organic species of tritium in a mixture of compounds in the
authorised releases of wastes to the Bristol Channel from the Nycomed-Amersham (now
GE Healthcare) radiopharmaceutical plant at Whitchurch, Cardiff, UK
The extremely high CFs can’t be explained by analytical errors (Hunt et al., 2010)
Advanced hypotheses:
- concentration of organic tritium by bacteria and subsequent transfer in the food chain;
- ingestion of contaminated sediment;
- ingestion of contaminated prey;
- direct uptake of DOT (DISOLVED ORGANIC TRITIUM) from the sea water;
- bioaccumulation occur via a pathway for the conversion of the organic compounds
labelled with dissolved 3H into particulate matter (via bacterial uptake / physico-chemical
sorption) and the subsequent transfer to the foodchain (McCubbin et al., 2001) →not valid, because
monitoring data on sediment and suspended matter compared with data on tritium in benthic fauna
show that the ingestion of sediment or particulate matter is not a reasonable explanation
AQUAtic TRITium - an update (see Dynamic model for tritium transfer in aquatic food chain, A.
Melintescu, D. Galeriu, submitted to Radiat. Environ. Biophys.)
• We introduced the direct uptake of DOT in the dynamic eqs. for autotrophes
(phytoplankton, benthic algae) and consumers (invertebrates, fishes):
dCo, phpl
dt
 0.4    Dryf  0.001 CW  VDOT * C DOT    Co, phpl
dCorg , x
= a x C f , x (t ) + bx C w (t)  VDOT  CDOT - K 0.5, x C org , x
dt
CW - HTO concentration in water (Bq m-3);
CDOT - the dissolved organic tritium concentration (Bq L-1);
VDOT - the uptake rate of DOT (L kg -1fw day-1)
Simplification of Michaelis Menten equation in practical application
The growth rate μ depends on nutrients, light and temperature
The coefficients a and b depends on SAR and OBT loss rate K05
(reflects processes when only HTO is primary source)
Cf depends on prey preference and availability
K05 depends on species, mass, temperature and pray availability
The dynamics of OBT concentration in different aquatic organisms, considering a
tritium release in Danube of 3.7 PBq on August 1 and a river flow of 6000 m3s-1,
1000
OBT concentration (Bq/kg fw)
100
10
phytoplankton
1
zooplankton
zoobenthos
0.1
benthic algae
molluscs
carp
0.01
pike
roach
0.001
0.1
1
10
time (d)
100
1000
In practice, an incident with tritium loss in Danube River can occur any time and it
will be useful to understand the seasonal effect of the release impact on human
ingestion coming from fish. Across the years, the Danube River’s flow and temperature
vary and for the same release of 3.7 PBq of tritium for 6 hours, the fish contamination
varies also
Date of release
River flow (m3s-1)
River temperature (°C)
Ingested activity of fish (Bq)a
% OBTb
February 15
3000
3
22844
3
April 15
5000
10.5
14348
7.3
May 15
3500
17
21831
13
July 15
1500
24
63377
30
September 15
1000
20
92430
28
October 15
1500
15
53790
17.5
December 15
1500
5.5
46415
4.4
a
b
0.5 kg of a mixture of carp and zander
The percentage of OBT coming from the ingested fish activity
Water temperature has a large influence on the OBT content in fish and the highest
impact is in late summer (September 15).
DOT- The Cardiff case
For the Cardiff case it should be noted that the tritated waste from GE Healthcare
(former Amersham) includes not only the HTO and the by-product, but also the high
bio available tritiated organic molecules (i.e. hydrocarbons, amino acids, proteins,
nucleotides, fatty acids, lipids, and purine / pyrimidines).
For the model application, the input data as: the annual average of total tritium and
organic tritium releases from GE Healthcare, tritium concentration in sea water and
the monitoring data for mussel and flounder have been taken from literature
Using the available input data, the model successfully predicts the trend for tritium
concentration in mussels and flounders
1000000
mussel (model)
Tritium concentration (Bq/kg fw)
flounder (model)
mussel (exp)
flounder (exp)
100000
10000
1000
0
2000
4000
6000
time (day)
8000
10000
12000
CONCLUSIONS
•
In the late 1980, the aquatic pathways after releases of tritium (HTO)
were not considered of relevance (Blaylock et al., 1986) and simple
models were used based on specific activity approach.
•
The occurrences of high concentration factors in Cardiff area generate
debate and public concern for the development of nuclear
pharmaceutical production.
•
The present model intends to be more specific than a screening model,
including a metabolic approach and the direct uptake of DOT in marine
phytoplankton and invertebrates.
•
The high concentration factors found in Cardiff area are not a general
problem of nuclear industry. The Cardiff case reflects a specific
biological process in marine invertebrates and the consequences were
ignored in the past.
•
In order to have a better control of tritium transfer into the environment,
not only tritiated water must be monitored, but also the other chemical
forms and mainly, OBT in food chain.
To address the retention of OBT in children and the effect of organ growth on OBT
retention, an age-dependent biokinetic model for dietary intakes of OBT should be
developed. This model would need to include all age groups, including the nursing
infant, and account for physiological and anatomical variations associated with age
CNSC Tritium Studies Project Synthesis Report June 2010
Retention of tritium in reference persons: a metabolic
model. Derivation of parameters and application of the
model to the general public and to workers
D. Galeriu and A. Melintescu
JOURNAL OF RADIOLOGICAL PROTECTION
30 (2010) 445–468 (31/08/2010)
Extension of
Reassessment of tritium dose coefficients for general public
A. Melintescu, D. Galeriu, H. Takeda
Radiation Protection Dosimetry, 127 (1-4):153-157, 2007
Energy Metabolism and Human Dosimetry of Tritium
D Galeriu, H Takeda, A. Melintescu, A Trivedi
Fusion Science and Technology, Vol. 48,
Number 1 – July/August 2005, P.795-798
Organ-specific metabolic rates (SMR) for
adults in basal state
Flowchart of model for humans
FBW→out
HTO
Intake
Body
Water
(BW)
Red Blood Cell (RBC)
FRBC→BP
FBP→BW
FBP→BR
FBP→VIS
Viscera (VIS)
FST→SI
Small Intestine
Content (SI)
brain
1.008
liver
0.84
heart
1.841
kidney
1.841
muscle
0.055
adipose
0.019
bone
0.00963
lung
0.5
GIT
0.35
Skin
0.025
Residual*
0.014
Brain (BR)
FBR→BP
FSI→BW
SMR (MJ kg-1 fw d-1)
FBP→RBC
FBW→BP
OBT
Intake
Stomach Content
(ST)
Organ
Blood
Plasma
(BP)
FVIS→BP
FBP→MUS
Muscle (MUS)
FMUS→BP
FSI→BP
FBP→AD
Adipose Tissue (AD)
FSI→LI
FAD→BP
Large Intestine
Content (LI)
FBP→REM
Remainder (REM)
FREM→BP
FBP→uo
Excretion of OBT in urine
ROLE OF BRAIN
Glucose utilization (metabolic rate)
for cortex region at various human ages
mass fraction
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
muscle
brain
adipose
remainder
viscera
NB
1
5
10
15f 15m
age, gender
af
am
Reconstruction of basal metabolic rate
energy fraction basal
12
10
BMR exp
8
6
4
2
0
0
1
2
3
4
5
BMR model
6
7
8
9
10
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
muscle
brain
adipose
remaider
Viscera
NB
1
5
10
15f 15m
age, gender
af
am
TESTS with human experimental data; HTO intake (left), OBT intake (right)
LT301 OBT in urine
OBT_exp
10
OBT_model
1.E+05
exp
model
1
Percent of intake
OBT concentration (Bq/L)
1.E+06
1.E+04
1.E+03
0.1
0.01
1.E+02
0
50
100
150
200
250
300
0.001
350
0
20
40
60
Time (d)
100
120
140
OBT in urine
1.E+06
OBT_conc_exp
10
OBT_conc_mod
1.E+05
exp
Percent of intake
OBT concentration (Bq/L)
80
Time (d)
1.E+04
1.E+03
1.E+02
model
1
0.1
0.01
0.001
0
50
100
150
200
Time (d)
250
300
350
0
50
100
Time (d)
NO other model was tested with OBT experimental data
150
Integrated concentrations for model compartments (Bq d kg-1 fw) after a single unit intake
Case
HTO*
OBT#
Adipose
Muscle
Viscera
Residual
RBC
Brain
3 months OBT
1.21
2.87
9.28
0.948
2.13
1.69
1.95
0.710
10 years OBT
0.469
0.831
2.37
0.365
0.552
0.415
0.463
0.466
adult female OBT
0.348
0.909
2.01
0.339
0.513
0.429
0.431
0.433
adult male OBT
0.307
0.551
1.52
0.256
0.387
0.305
0.325
0.327
adult male HTO
0.341
0.0327
0.09
0.0152
0.023
0.0181
0.0193
0.0194
* Tritium concentration in body water;
# Tritium concentration in all organic compartments
Tritium concentration (Bq kg-1 fw) after 3000 days of continuous HTO intake (1 kBq d-1)
T conc. (Bq kg-1 fw)
blood plasma
RBC
adipose
muscle
viscera
residual
brain
whole
OBT
5
19
88
15
23
19
19
32.1
HTO
330
220
73
270
250
160
270
205
Total T
340
240
160
290
270
180
290
237.1
Predicted doses for a single OBT intake (10
values
age
ICRP
H (uniform, RBE=1)
-11 Sv
Bq-1) using different RBE
E (non-uniform, RBE=1)
E (non-uniform, RBE>1)
5%
50%
95%
5%
50%
95%
5%
50%
95%
3 months
12
26.4
28.9
31.4
19.4
21.4
23.5
61.6
69.5
77.4
1 year
12
16.6
18.1
19.7
12.4
13.8
15.2
38.7
43.8
48.6
5 years
7.3
9.5
10.5
11.5
7.7
8.6
9.7
23.7
26.8
29.7
10 years
5.7
8
8.7
9.5
5.7
6.2
7.0
17.3
19.5
21.7
15years
4.2
6.4
7
7.6
5.8
5.4
6.2
14.5
17.1
19.2
adult
4.2
6.7
7.2
7.7
4.4
4.9
5.2
13.9
15.6
17.4
H - uniform distribution, no wT; E – non uniform distribution to be compared with ICRP
Moderate increase, but infant a factor 2
Use bioassay
Dynamics of OBT in blood plasma and red blood
Total T and OBT in urine after HTO or OBT intake
cells OBT after an OBT intake of 1000 Bq
1.E+03
1
totT_hto
0.1
totT_obt
OBT_hto
0.01
OBT-obt
0.001
0.0001
-1
19
39
59
79
99
time (d)
Conc. (Bq/kg dm)
% excreted per day
10
O_bloodpl(OBT)
O_RBC(OBT)
1.E+02
1.E+01
1.E+00
1.E-01
0.1
1
10
time (d)
SATISFIES THE RECENT REQUIREMENTS
100
1000
CONCLUSIONS
“Tritium is one of the most benign of radioactive materials
that I’ve worked with in my career, and I’ve worked with
many of them. But on the other hand, the perception of
tritium as a potential risk in the environment to the public
is huge; it is absolutely huge. It is the industry’s biggest
problem since the Three Mile Island accident in 1979.”
Dr. John E. Till, Author of
Risk Analysis for Radionuclides Released to
the Environment - Oxford University Press 2008
(but Chernobyl?)
TODAY CHALENGES:
NIGHT FORMATION OF OBT IN CROPS
HARMONIZATION FOR CONCEPTUAL MODEL
PREGNANT WOMEN AND FOETUS
OPERATIONAL MODEL DESIGN - GENERAL CONCEPT
Welcoming China, USA, Russia
Budget!
Acknowledgments - huge list
Thank you for your attention!