|
Summary
The
present report summarises the results obtained by the execution of the
project “Box Model Improving (Phase 1)” as a part of the programme
“Transport and Fate of Contaminants in the Northern Seas”.
The
approach for box modelling, including terms for describing the
dispersion of radionuclides
into oceanic space with time, was developed. The analysis of
innovation features for the model indicates the significance of the
present approach for evaluation of the distribution of radionuclides
in the oceanic space. The ice module was developed and added to the
marine model. Execution of the model showed that ice transport of
radionuclides can be a significant factor for radionuclides with high
sediment distribution coefficients.
The
sensitivity analysis for selected parameters has indicated that both
local and global parameters, as well as scenarios, can be significant
for the results of modelling. Validation of the model with independent
data set shows a satisfactory comparison with experimental data
concerning dispersion of 99Tc in oceanic space.
Because
the present model includes terms for describing the dispersion of
radionuclides into oceanic space with time, it is possible to
describe time-depended processes in more detail by comparison with the
“traditional” approach for box modelling.
Information
for later model development is collected, areas for improving of the
model
box
structure is identified and the structure of the Arctic ocean waters
with regards to surface, Atlantic and dep waters is developed and can
be used for future calculations by the box model. Boxes for the Ob and
Yenisey Bays with corresponding graph structure are incorporated to
the present model.
Scientific
results
The
present report summarises the results obtained by the execution of the
project “Box Model Improving (Phase 1)” as a part of the programme
“Transport and Fate of Contaminants in the Northern Seas”.
The
approach for box modelling, including terms for describing the
dispersion of
radionuclides into oceanic space with time, was developed.
The analysis of
innovation features for the model indicates the significance of the
present approach for evaluation of the distribution of radionuclides
in the oceanic space. Results of calculations indicate significant
differences of up to orders of magnitude during the initial time of
dispersion because of the instantaneous spread of radionuclides
according to traditional modelling. It is indicated significant
differences even for calculation of world collective doses in the long
term (up to 1000 years) for some scenarios. There are, also, important
differences for sea areas contributions to doses to man.
The
sensitivity analysis for selected parameters indicates that results of
calculations are sensitive for changing global parameters (concentration
factors for seafood, sediment distribution coefficient) as well as
local parameters for initial boxes (the sedimentation rate, the
suspended sediment load, the water flux) and scenarios of dispersion
of radionuclides. It is, also, shown that the sensitivity index for
some radionuclides and scenarios depends of time.
The
ice module was developed and added to the marine model. Execution of
the model showed that ice transport of radionuclides can be a
significant factor for radionuclides with high sediment distribution
coefficients. According to the results of calculations, effect of the
ice transport of radionuclides to the distribution of radioactivity
differs widely and can significantly increase the concentration of
radionuclides in sea water, as well as, doses distribution for the
radionuclides with high Kd (241Am, 60Co),
with this, the dose impact from some sea areas can increase up to
factor three. It
is necessary to note that the content and structure of the sediment
load in ice vary within wide limits, and therefore, sensitivity and
uncertainty analysis can improve the possibility to represent model
results satisfactorily.
Validation
of the model with independent data set shows a satisfactory comparison
with experimental data concerning dispersion of 99Tc from
Sellafield and La Hague facilities in oceanic space.
The
preliminary evaluation of the consequences
after potential releases of radionuclides from the submarine
“Kursk” indicates that during the first time of the potential
dispersion of the radionuclide, 137Cs concentration in fish
varies widely depending on the habitat of fish, because during the
beginning of the dispersion the Barents Sea contains regions with
relatively high contamination and without contamination in the same
time. Results of the preliminary calculations of the collective doses
show that doses to man is dominated by dose from 137Cs and
from the Barents Sea.
Information
for following model development was collected, areas for improving of
the model box structure were identified, and the structure of the
Arctic Ocean waters with regards to surface, Atlantic and deep waters,
was developed. Boxes for the Ob and Yenisey Bays with corresponding
graph structure are incorporated to the present model.
The improved box structure can be used for future calculations
by the box model.
Relevance
for monitoring (only in Norwegian)
Statens
strålevern sin modell gir oss kunnskap om oppførsel
av radionuklider i havet med hensyn til distribusjon av
radionuklider i haveområder, vann-sediment interaksjon av
radionuklider,
forurensing i flora og fauna i havet og vurdering av doser til
befolkningen.
Det
ble funnet følsomhet av resultater for
forskelige parametre. Med målinger og evalueringer av disse
parametrene er det mulig å vurdere følsomhet av aktuelle havområder
for utslipp av radionuklider.
Det
ble oppdaget at istransport kan være betydelig for enkelte
radionuklider og havområder og ubetydelig for andre. Disse resultater
kan hjelpe med å optimalisere ressurser til overvåkningsprogrammer.
Preliminær
vurdering av konsekvenser etter potensielle utslipp fra den
sunkne ubåten “Kursk” viser at overvåkning av Barentshavet
er aktuelt på grunn av mulig økning av konsentrasjon av
radionuklider i fisk.
|
