Simulation of radioactive pollution of seawater as a result of the - - PowerPoint PPT Presentation

РОССИЙСКАЯ АКАДЕМИЯ НАУК Институт проблем безопасного развития атомной энергетики RUSSI AN ACADEMY OF SCI ENCES Nuclear Safety I nstitute (NSI RAS), Moscow

Simulation of radioactive pollution of seawater as a result of the accident at Fukushima-1 from the point of view of potential danger of radiation transportation on long distances

Sorokovikova O.S., Semenov V.N., Dzama D.A.(NSI RAS)

I RKUTSK, ENVI ROMI S-2012

This radioactive emission is the largest

• ne among emissions of artificial radio-

nucleus into water

11 march 2011 the earthquake was happened in Japan

1 2 3 4

Radioactive pollution in nearby seawater Fukushima Daiichi (1) NPP as a result of the accident was happened

TECHNI CAL CRI SI S CENTER of ROSATOM (locate in NSI RAS, Moscow)

• The TCC of ROSATOM has a collection of information-modeling systems for

decision support making, monitoring, forecasting and analysis of the radiation situation

Goals of the work

• The main goal of the work is to perform express analyses of hypothetically

radioactive contaminations in sea water nearby Russian coasts

• Forecast the radiation situation in sea water near Japan

I nformation-modeling computer system

• Express computer system, called NEPTUN-1 has been created especially for

the Pacific ocean aquatic and used to solve the problem

• The available region is
• The system uses two dimensional velocity streams in the upper layer above

the seasonal thermo wedge, distributed in space and time

• There was taken into account downward motion in the lower layers of the

seasonal thermo wedge and other processes

• The computer system NEPTUN-1 contains the database on more than 100

nuclides and their decay chains

110.5E 179.5E 30.5N 64.5N ÷   ÷ 

NEPTUN-1 transport equation

Transport equation:

2 2 2

( , ) cos ( , ) ( , ) ( , ) ( , ) cos cos ( , ) ( , ) cos ( , , ) cos cos H c H cu H cv t a a c H c H K K Q t a a

ϕ θ

∂ ϕ θ ∂ ϕ ϕ θ ϕ θ ∂ ϕ θ ϕ θ ∂ ϕ∂ ϕ ϕ∂ θ ϕ θ ϕ θ ∂ ϕ ∂ ϕ θ ϕ θ ϕ ∂ ϕ ϕ∂ θ + + − ∂ ∂ ∂ ∂ − =

H – depth of the layer above the seasonal thermo wedge

(mixed layer depth)

c – concentration of radionuclide's (Bq/

q/ m ^ 3)

u & v – longitude and latitude components of currents

Q – source term

φ & θ – longitude and latitude

Numerical solution of the transport equation by lagrange big particle stochastic movement

I nitial condition for the Lagrange particles: Convection part: Diffusion part: Size particle’s increasing:

1 1 1

cos cos

n n n n n n n n i i i i i i i i

a a u t a a v t ϕ ϕ ϕ θ ϕ θ

+ + +

= + ∆ = + ∆

1 1 1

2 cos cos 2

n n n n n n i i n i i i i n

a a K tb a a K tb

ϕ θ

ϕ ϕ ϕ θ ϕ θ

+ + +

= + ∆ = + ∆  

,

t t

X x Y y

= =

= =

( ) ( ) ( )

2 2 1

2

n n i i n n

R R K K t

+

= + − ∆ 

Downward motion in the lower layers

Mass (i.e. radioactivity) of the Lagrange particle reduces: Here m − particle mass (Bq)

H – mixed layer depth(seasonal thermo wedge depth)

( ) ( )

, , w dm m dt H θ ϕ θ ϕ = −

1 n n

m m dm

+ =

+

Velocit y dat a cell

( ) ( )

1/2 1/2 1/2 1/2 1/2 1/2 1 1 1/2 1 1 1/2 1/2 1/2 1/2

1/2

1 1

j j j j j i i i i i j j j j j i i i i

i

w u H u H dx v H v H dy

+ + + + + + + + + + + + + + +

+

= − + −

Horizontal turbulent diffusion model (Ozmidov)

We use the Ozmidov model to parameterize the horizontal diffusion of the contamination: Here Kτ − the horizontal diffusion coefficient (m2/ s) L − spatial scale of the contamination (m) ε − turbulent energy dissipation (m2/ s2) hτ − sea currents data grid size (m)

( ) ( ) ( )

1/3 4/3 1/3 4/3

m m c l l l h K l c h h l h

τ τ τ τ τ

ε ε  ≤  =  >  

( )

1e-8, 1e+4 m 1e-9, 1e+4 m l l l ε ≤  =  > 

March - mean ocean currents

March - mean ocean currents

Ocean currents (10 April 2011, data resolution - 1/ 32 degree)

Main nuclides contained in the release on Fucushima-1

Nuclide Half-life

131I

8 days

137Cs

30.15 years

134Cs

2.1 years

136Cs

13.1 days

132Te − 132I

78 hours

Time integrated concentration, conservative estimation (source – 1MCu of Cs-137)

East coast West coast

Concentration, conservative estimation (1MCu of Cs-137, east)

Instantaneous source 4 days source Critical concentration of Cs-137 is 350 Bq/m3

Concentration of Cs-137 & I -131 measurement points (MEXT, Japan)

Concentration, collected from all measurement points

Cs-137 I-131

Assessment source of Cs-137 and I -131 estimation

• Assessment of the maximum concentration at emission form the

atmosphere gives a much less values (5-10% of maximum

• bserved values)
• Therefore the main source of sea water pollution − is direct

emission from the NPP to the water area

• Comparison of sampling and model data
• Estimate of Cs-137 radioactivity gives 0.03MCu
• Estimate of I -131 radioactivity gives 0.07MСu

CONCLUSI ONS

• Analysis of simulation results has shown that as opposed to the
• n-ground ecosystems where residual radioactive pollution would

exist many years, the period of pollution of the seawater in the discussed region will few months

• There is no any potential danger to the Russian east coastal water

areas

• The contamination, which is the result of the main emission of the

radioactive water from NPP Fucushima-1 to the ocean, hasn’t been detected after ~ 1.5-2 month in the measurements points (MEXT, 30km form the coastline)

• Hypothetical secondary washout from the contaminated land can

be a problem only in the immediate vicinity of the coastline (for region closer 30km)

Thank You for attention!