Nguyen Tuan Khai, PhD

Institute for Nuclear Science and Technology (INST)

Assessment on Environmental Impact caused by

Radioactive Substances Released from Ninh Thuan 1

NPP in Normal Working Conditions and in Scenarios

of Severe Accident

INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)

Technical meeting on Towards Nuclear Energy

System Sustainability - waste Management and

Environmental Stressors

IAEA, 24-26 May 2016

Contents:

1. Motivation of the Study

3. Building Data Input and Radiation Safety Assessment in

Routine Operation of Ninh Thuan 1 NPP

4. Scenario and Assessment for Severe Accident at Level 7

5. Concluding Remarks

2. Defence in Depth

2

1. Motivation of the study

- In November, 2009 the National Assembly of Vietnam approved the resolution on

the first two NPP projects, Ninh Thuan 1&2, with a total capacity of 2,000 MW for

each. At present, the Government has decided the foreign partner for the Ninh Thuan

1 project is RF and for Ninh Thuan 2 is Japan.

- For the Ninh Thuan 1 project the VVER-AES2006 reactor technology was

proposed for selection and the site was decided at Phuoc Dinh village, Thuan Nam

district, Ninh Thuan province.

- NPP release radioactive nuclides into the

environment. Dispersion of radioactive substances

and their deposition on ground will cause impact to

the environment. Therefore, study on transport and

assessment for radiation dose to publics are of

essential requirements for a NE project

- Calculation results provide the necessary data for

Report on EIA and support for regulatory organization

(VARANS) in reviewing the Safety Analysis Report

(SAR)

3

2. Defence in Depth

- The first barrier is the fuel pellet;

- The final barrier to

preventing FP release is the

reactor containment.

For the FPs generated within the core to

reach the environment they must pass

through 4 FP barriers:

- The second is the fuel pellet cladding;

- The third one is the RCS;

There are two main resources in producing radioactive nuclides in NPP which

are fission products and activation ones

4

b. phần mềm GALE86:

This code is used to estimate the released source term based on inputing the

technical parameters of the NPP technology

c. phần mềm RASCAL4.3:

This code is used to estimate the released source term and dose distribution within

radius 80 km from the plant in scenarios of nuclear incident/accident.

d. phần mềm LAMER (Provided by Japan Atomic Energy Agency):

This code is used to estimate the source term and dose distribution from release to

the water in scenario of incident/accident.

3. Building data input and radiation safety assessment

in routine operation of NPP Ninh Thuan 1

a. Gói phần mềm NRCDose72 (XOQDOQ, GASPAR2, LADTAP2):

The NRCDose72 package is developed by the USNRC and used to assess the

radioactive routine release and population dose in radius 80 km from NPP site in

normal operation conditions.

3.1 Overview on NRCDose72 package (provided by USNRC)

5

Fig.1 : Dose assessment to public from all exposure pathways caused by

radioactive releases from NPP

6

XOQDOQ is used to model the

concentration and deposition for routine

radioactive release to the atmosphere;

XOQ is defined as the average

concentration normalized by source

strength;

DOQ is defined as the average relative

deposition per unit area.

XOQDOQ

Meteo.

Terrain

X/Q(s/m3)

D/Q(s/m2)

GASPAR

Output

XOQDOQ

Poula-

tion

Pop.

dose

Indiv.

Dose

Produc-

tion

Source

term GASPAR2 is used to estimate radiation

dose to individuals and population

groups for radioactive release from a

LWR during routine operation.

Fig.2: Calculation scheme of GALE86 and NRCDose72

GALE86VVER-

2006Source

term

GALE86 is used to evaluate the source

term released in routine operation of

NPP;

7

A. Meteorological data

Meteorological data is processed as a joint frequency table during a given time

period including atmospheric stability class, wind direction, and wind speed class

Wind speed

classWind speed (m/s)

1

(gió lặng)

0.4

2 0.4 – 1.7

3 1.7 – 3.5

4 3.5 – 5.7

5 5.7 – 8.4

6 8.4 – 10.6

7 > 10.6

- Atmospheric stability is grouped into seven categories from extremely unstable to

extremely stable: A to G according to the vertical temperature gradient

Pasquill

Stability

class

∆T/∆Z

A ∆T/∆Z < -1.9

B -1.9 ≤∆T/∆Z <-1.7

C -1.7 ≤∆T/∆Z < -1.5

D -1.5 ≤∆T/∆Z < -0.5

E -0.5 ≤∆T/∆Z < 1.5

F 1.5 ≤∆T/∆Z <4 .0

G ∆T/∆Z ≧ 4.0

8

3.2 Building data input

Fig. 4: Frequency distribution

of wind classes

DATABASE PROVIDED BY PHANRANG STATION IN

FIVE YEARS (1/1/2009 – 31/12/2013)

Fig.3: The wind rose distribution

obtained from the database of

the Phan Rang station

9

B. Terrain data

The terrain is divided into 10 zones

following 16 directions to create the

sectors.

Contour map with a 1:250000 passes

through 6 provinces including Phú

Yên, Khánh Hòa, Ninh Thuận, Đắk

Lắk, Lâm Đồng and Bình Thuận

provided by Department of Survey

and Mapping Vietnam.

Fig. 5: Terrain map in radius 80 km from NPP Ninh Thuận 1

Terrain elevation (in meters, compared

to the factory floor) is the maximum

height in the topographic data collected

in the 80 km radius from the NPP site;

The direction and distance from the

source are included in the terrain

elevation data

10

C. Data on population distribution

- The population distribution is one of the important database for the NRCDose72

package in assessing the impact of radioactive release to publics living around the

NPP Ninh Thuan 1.

- Building the population distribution was performed based on establishing the

maps on population distributions in the ranges: 0-2, 2-4, 4-6, 6-8, 8-10, 10-16,16-

40, 40-60 và 60-80 km. Hence, we can see in a scope of 80 km the population data

are included 4 provinces: Ninh Thuận, Bình Thuận, Lâm Đồng and Khánh Hòa.

- The total population and population distributions have been processed for four

age groups: infant, children, teenager and adult in each sector;

D. Data on agricultural production activities

Crop and cattle breeding: Data on production and distributions of meat, milk and

agricultural products within 80 km around the NPP site

11

Radio. Nuclide Ci/Unit/Year Radio. Nuclide Ci/Unit/Year

H-3 1.00E+03 MN-54 5.70E-05

C-14 7.30E+00 CO-57 8.20E-06

Ar41 3.40E+01 CO-58 4.80E-04

I-131 1.80E-02 CO-60 1.10E-04

I-133 5.50E-02 FE-59 2.80E-05

KR-85M 6.20E+01 SR-89 1.60E-04

KR-85 2.10E+03 SR-90 6.30E-05

KR-87 2.10E+01 ZR-95 1.00E-05

KR-88 7.60E+01 NB-95 4.20E-05

XE-131M 1.70E+03 RU-103 1.70E-05

XE-133M 1.10E+02 RU-106 7.80E-07

XE-133 5.20E+03 SB-125 6.10E-07

XE-135M 7.00E+00 CS-134 4.80E-05

XE-135 5.70E+02 CS-136 3.30E-05

XE-138 7.00E+00 CS-137 9.00E-05

CR-51 9.70E-05 BA-140 4.20E-06

CE-141 1.30E-05

Source term released in routine operation by GALE86

3.3 Calculation Results

12

Fig.6: X/Q distribution in radius 80 km

The X/Q and D/Q distributions which are dominant in North East and South West;

This is consistent with the obtained wind rose distribution.

13

Pathway Annual total population dose (person-mSv)

Effective Gi-lli Bone Liver Kidney Thyroid Lung Skin

Plume 5.16E-2 5.16E-2 5.16E-2 5.16E-2 5.16E-2 5.16E-2 5.70E-02 5.44E-1

27.33% 27.26% 27.94% 28.30% 28.31% 18.88% 30.39% 79.77%

Ground 5.78E-3 5.78E-3 5.78E-3 5.78E-3 5.78E-3 5.78E-3 5.78E-03 1.16E-2

3.06% 3.06% 3.13% 3.17% 3.17% 2.12% 3.08% 1.70%

Inhalation 2.18E-2 2.16E-2 2.16E-2 2.16E-2 2.16E-2 2.72E-2 2.16E-02 2.16E-2

11.59% 11.40% 11.70% 11.84% 11.84% 9.98% 11.51% 3.16%

Rice,

Vegetable 7.48E-2 7.80E-2 7.54E-2 7.32E-2 7.32E-2 7.66E-2 7.32E-02 7.44E-2

39.65% 41.28% 40.90% 40.20% 40.19% 28.07% 39.01% 10.90%

Cow milk 5.01E-3 3.45E-3 3.24E-3 3.21E-3 3.21E-3 3.87E-2 3.21E-03 3.25E-3

5.31% 3.65% 3.51% 3.53% 3.53% 28.35% 3.43% 0.95%

Meat 2.46E-2 2.52E-2 2.36E-2 2.36E-2 2.36E-2 3.44E-2 2.36E-02 2.40E-2

13.05% 13.36% 12.82% 12.97% 12.97% 12.61% 12.58% 3.52%

Total 1.89E-1 1.89E-1 1.85E-1 1.82E-1 1.82E-1 2.74E-1 1.88E-01 6.82E-1

Table 1: Annual Total Population Dose

14

Radio-

nuclides

Annual total population dose (person-mSv)

Effective Gi-lli Bone Liver Kidney Thyroid Lung Skin

3H 4.20E-2 4.20E-2 4.20E-2 4.20E-2 4.20E-2 4.20E-2 4.20E-2 4.20E-2

22.28% 22.21% 22.77% 23.06% 23.07% 15.39% 22.40% 6.16%14C 8.44E-2 8.90E-2 8.26E-2 8.26E-2 8.26E-2 8.26E-2 8.26E-2 8.44E-2

44.74% 47.02% 44.75% 45.32% 45.34% 30.24% 44.02% 12.37%41Ar 3.12E-3 3.12E-3 3.12E-3 3.12E-3 3.12E-3 3.12E-3 3.12E-3 1.48E-2

1.65% 1.65% 1.69% 1.71% 1.71% 1.14% 1.66% 2.16%131I 4.54E-3 2.26E-4 2.08E-4 1.99E-4 1.98E-4 8.86E-2 2.08E-4 3.36E-4

2.41% 0.12% 0.11% 0.11% 0.11% 32.47% 0.11% 0.05%133I 2.34E-4 1.05E-4 1.05E-4 1.04E-4 1.04E-4 2.60E-3 1.06E-4 7.60E-4

0.12% 0.06% 0.06% 0.06% 0.06% 0.95% 0.06% 0.11%85mKr 8.34E-4 8.34E-4 8.34E-4 8.34E-4 8.34E-4 8.34E-4 8.74E-4 6.86E-3

0.44% 0.44% 0.45% 0.46% 0.46% 0.31% 0.47% 1.01%85Kr 1.23E-3 1.23E-3 1.23E-3 1.23E-3 1.23E-3 1.23E-3 2.88E-3 1.36E-1

0.65% 0.65% 0.67% 0.68% 0.68% 0.45% 1.54% 20.01%87Kr 1.05E-3 1.05E-3 1.05E-3 1.05E-3 1.05E-3 1.05E-3 1.10E-3 8.78E-3

0.56% 0.55% 0.57% 0.58% 0.58% 0.38% 0.58% 1.29%88Kr 1.29E-2 1.29E-2 1.29E-2 1.29E-2 1.29E-2 1.29E-2 1.30E-2 5.52E-2

6.83% 6.81% 6.98% 7.07% 7.07% 4.71% 6.90% 8.10%131mXe 1.45E-3 1.45E-3 1.45E-3 1.45E-3 1.45E-3 1.45E-3 2.24E-3 4.62E-2

0.77% 0.77% 0.79% 0.80% 0.80% 0.53% 1.19% 6.76%133mXe 3.38E-4 3.38E-4 3.38E-4 3.38E-4 3.38E-4 3.38E-4 4.04E-4 6.30E-3

0.18% 0.18% 0.18% 0.19% 0.19% 0.12% 0.21% 0.92%133Xe 1.68E-2 1.68E-2 1.68E-2 1.68E-2 1.68E-2 1.68E-2 1.90E-2 1.68E-1

8.89% 8.86% 9.08% 9.20% 9.20% 6.14% 10.14% 24.60%

Table 2: Annual Total Population Dose induced by radioactive nuclides

15

Table 3: Annual Effective Doses to 4 population groups

Location Direction Distance

(km)

Annual Effective dose (mSv) for 4 age groups

Adult Teenage Children Infant

Vĩnh Tường N 1.165 3.55E-04 4.69E-04 8.19E-04 9.03E-04

Sơn Hải S 2.18 6.35E-04 8.20E-04 1.40E-03 1.51E-03

Từ Thiện N 3.38 6.64E-05 8.60E-05 1.47E-04 1.59E-04

Bầu Ngứ NW 5.9 9.92E-05 1.30E-04 2.25E-04 2.46E-04

Hoà Thuỷ NNW 9.1 2.68E-05 3.31E-05 5.33E-05 5.41E-05

Phước Lập NW 11.25 4.81E-05 6.00E-05 9.76E-05 1.00E-04

Quán Thẻ W 12.5 1.90E-05 2.34E-05 3.74E-05 3.78E-05

Hiếu Thiên WNW 13.45 2.20E-05 2.81E-05 4.73E-05 5.04E-05

Thương Diêm SW 15.48 6.81E-05 8.94E-05 1.55E-04 1.69E-04

Lạc Tiến WSW 14.42 1.83E-05 2.29E-05 3.75E-05 3.87E-05

Cà Ná SW 16.79 6.12E-05 8.04E-05 1.39E-04 1.53E-04

Phan Rang N 14.2 1.51E-05 1.78E-05 2.68E-05 2.50E-05

Liên Hương SW 38.75 1.76E-05 2.22E-05 3.71E-05 3.90E-05

Phong Phú WSW 43.6 4.82E-06 5.73E-06 8.78E-06 8.28E-06

Phan Điền WSW 58.5 3.23E-06 3.80E-06 5.72E-06 5.27E-06

Chợ Lầu WSW 60.9 3.10E-06 3.64E-06 5.45E-06 5.02E-06

Thạnh Mỹ NW 66.3 3.96E-06 4.67E-06 7.07E-06 6.51E-06

Tô Hạp N 63.6 1.99E-06 2.28E-06 3.29E-06 2.84E-06

Cam Ranh NNE 62.4 2.75E-06 3.29E-06 5.09E-06 4.85E-06

Liên Nghĩa WNW 78 1.90E-06 2.27E-06 3.48E-06 3.27E-06

16

- The obtained results on the dose evaluation induced by radioactive nuclides

released from the NPP are much lower than the limit of 1.0 mSv for publics;

- From Table 1: The dose induced by plume gives the greatest contribution, from

about 20% for thyroid to about 80% for skin, to the annual integrated dose. This is

because the plume can cause a direct expose, especially for skin.

- From Table 2: The radioactive isotopes 14C and 3H cause the greatest contributions

to the annual population dose. This can be understandable, because these two

isotopes have very long half-lives and are produced by typical nuclear reactions in

moderator and core materials: 13C(n, γ)14C, 14N(n, p)14C, 15N(n, d)14C, 16O(n,3He)14C and 17O(n, α)14C for 14C, and 2H(n, γ)3H, 6Li(n, α)3H, 14N(n, 3H)12C and also

ternary fission mode for 3H

- Amongst the fission products the greatest contributions are from 133,135Xe;

In addition, it should be noted that 60Co induces a typical dose contribution

amongst the radioactive isotopes produced from neutron-induced activation;

17

Conclusion: Based on the calculation results for the annual dose

evaluations and analysis for the dose contributions within 80 km from the

plant we can conclude that the gaseous effluent release from the NPP Ninh

Thuan 1 in the normal working conditions satisfies the requirements on

radiation safety for the environment and publics.

- From Table 3: The effective dose for the children is about 1.7 and 2.3 times,

respectively, greater than those for the teenage and adult. This is due to the fact

that children are clearly more radiosensitive than adults. This conclusion was

found in UNSCEAR-2013 Report, where it is shown that for a given radiation

dose, children are generally at more risk of tumour induction than are adults.

18

4. Assessment for a Severe Accident at Level 7

4.1 Scenario of the accident

- It is assumed that two incidents occurred at

the same time at NPP Ninh Thuan 1: Station

Black Out (SBO) and a large break in the RCS

(LB LOCA). Consequently, both incidents made

the reactor core to be quickly uncovered

- It is assumed that:

Reactor shutdown at 0:00 on 17Jan. 2013;

Core uncovered at 03:00, i.e. only 3-hours

core covering;

It recovered at 09:00, i.e. 6-hours loss of

coolant;

RCS

- During 6 hours of uncovering the fuel rods was heated up and melt down due to decay

heat. This caused release of FPs from the core to the containment, and consequently to

increase temperature and pressure. As a result, the containment has failed and caused

radioactive release to atmosphere with a leakage rate of 10% per day.

- Also the containment sprays did not work, only natural circulation was used.

- The containment integrity was maintained within two hours before the leakage occurred

for 4 hours from 05:00 to 09:00;19

20

4.2 Building the data input

Event Type Nuclear Power Plant

Location Phuoc Dinh

Name: Ninh Thuan 1

City, country, state Ninh Phuoc, Vietnam, Ninh

Thuan

Lat/Long/Elev: 11.3963oN, 109.0037oE, 20 m

VVWR-1200 Reactor

parameters

Reactor power 3,200 MWt

Peak rod burn-up 60,000 MWd/MTU

Containment type PWR Dry Ambient

Containment volume 2.50E+06 ft3

Design pressure 72.52 lb/in2

Design leak rate 0.2%/day

Coolant mass 2.9E+05 kg

Assemblies in core 163

Steam generator U-type

SG water mass 52,220 kg

i. Data on VVER-1200 reactor

Source term

Type Time core is

uncovered

Shutdown 2013/01/17 at 0:00

Core uncovered 2013/01/17 at 3:00

Core recovered 2013/01/17 at 9:00

iii. Data for source term evaluation

ii. As mentioned above for scenario of accident

based on SBO incident and LOCA

iv. 6-hours release at a leakage rate: 10% per day

RCS

21

v. Data for Meteorology (48 hours)

iv.a: On 17 Jan. 2013 (Dry season)

iv.b: On 26 Sep. 2013 (Rainy

season)

Summary of data

at release point

Type Direction

Degree

Speed

(m/s)

Stability

Class

Precip. Temp. (oC)

2013/01/17 03:00 Obs 327 2 C None 23.0

2013/01/17 04:00 Obs 0 5 C None 23.2

2013/01/17 05:00 Obs 0 3 C None 23.0

2013/01/17 06:00 Obs 23 4 C None 23.8

2013/01/17 07:00 Obs 0 4 C None 24.8

2013/01/17 08:00 Obs 0 4 C None 26.9

. . .

2013/01/19 00:00 Obs 0 5 C None 22.9

Summary of data

at release point

Type Dir deg Speed

(m/s)

Stability

Class

Pricip Temp

(oC)

2013/09/26 03:00 Obs 225 1 D None 26.0

2013/09/26 04:00 Obs 225 0 D None 26.0

2013/09/26 05:00 Obs 335 1 D Rain 25.9

2013/09/26 06:00 Obs 295 2 D Light rain 25.8

2013/09/26 07:00 Obs 245 3 D None 25.6

2013/09/26 08:00 Obs 270 2 D Light rain 26.1

. . .

2013/09/28 00:00 Obs 270 0 D None 24.8

Table 4: The released source term: Total activity 9.06E+06 Ci

Nuclide Activity (Ci) Nuclide Activity (Ci) Nuclide Activity(Ci)

Am-241 1.40E-03 La-142 3.30E+02 Sr-91 6.50E+04

Ba-139 6.20E+03 Mo-99 5.80E+03 Sr-92 2.10E+04

Ba-140 1.70E+05 Nb-95 7.40E+03 Tc-99m 5.30E+03

Ce-141 7.40E+03 Nb-97 2.90E+02 Te-127 2.20E+04

Ce-143 5.80E+03 Nd-147 2.80E+03 Te-127m 3.50E+03

Ce-144* 6.00E+03 Np-239 8.80E+04 Te-129 1.10E+04

Cm-242 1.80E+02 Pm-147 6.00E-01 Te-129m 1.50E+04

Cs-134 1.20E+05 Pr-143 6.50E+03 Te-131 9.20E+03

Cs-136 2.40E+04 Pr-144 5.90E+03 Te-131m 4.10E+04

Cs-137* 8.30E+04 Pu-238 1.20E-03 Te-132 3.20E+05

Cs-138 5.90E+02 Pu-239 2.10E-03 Xe-131m 2.40E+04

I-131 3.90E+05 Pu-241 1.10E+03 Xe-133 3.50E+06

I-132 5.30E+05 Rb-86 8.60E+02 Xe-133m 1.00E+05

I-133 6.50E+05 Rb-88 2.00E+05 Xe-135 1.30E+06

I-134 1.10E+04 Rh-103m 5.30E+03 Xe-135m 1.90E+05

I-135 4.00E+05 Rh-105 3.40E+03 Xe-138 5.10E+00

Kr-83m 2.10E+04 Ru-103 5.40E+03 Y-90 6.20E+02

Kr-85 2.90E+04 Ru-105 1.40E+03 Y-91 5.20E+03

Kr-85m 1.60E+05 Ru-106* 3.00E+03 Y-91m 2.30E+04

Kr-87 3.50E+04 Sb-127 2.00E+04 Y-92 7.70E+03

Kr-88 2.50E+05 Sb-129 2.60E+04 Y-93 2.60E+03

La-140 1.20E+04 Sr-89 8.60E+04 Zr-95 7.20E+03

La-141 2.10E+03 Sr-90 1.30E+04 Zr-97* 5.20E+0322

- From the released source term the radiological equivalence to 131I for release to

atmosphere is calculated as (INES: International Nuclear Event Scale):

Atotal = (AiFi)= 60.8105Ci~ 2251015Bq = 225,000 TBq

This value shows that the accident

is graded at the INES level 7: Major

Accident

- Based on the source term

released, distribution of the

maximum dose values within a

radius of 25 miles (40.2 km) was

calculated (as a function of

dispersion time at 3, 10, 20, 30, 40

and 48 hours)

Fig.7: Contribution (%) from each nuclide

to the total radioactivity

23

Table 5: Variation of TEDE (mSv) as a function of time (hour)

and distance (km) for the dry season

Time (hour) 3 10 20 30 40

Distance (km)

0.1 21000.00 54000.00 54000.00 54000.00 54000.00

0.2 6600.00 16000.00 16000.00 16000.00 16000.00

0.3 3300.00 7500.00 7500.00 7500.00 7500.00

0.5 1400.00 3000.00 3000.00 3000.00 3000.00

0.7 840.00 1700.00 1700.00 1700.00 1700.00

1.0 500.00 930.00 930.00 930.00 930.00

1.5 290.00 490.00 490.00 490.00 490.00

2.0 210.00 320.00 320.00 320.00 320.00

4.8 60.00 78.00 78.00 78.00 78.00

6.4 39.00 49.00 49.00 49.00 49.00

8.0 28.00 35.00 35.00 35.00 35.00

11.3 19.00 24.00 24.00 24.00 24.00

16.1 7.30 10.00 10.00 10.00 10.00

24.1 2.20 4.40 4.40 4.40 4.40

32.2 0.28 3.30 3.30 3.30 3.30

40.2 0.01 2.80 2.80 2.80 2.80

TEDE (mSv)

24

Table 6: Distribution of maximum dose values (mSv) as a function of release

time of 30 hours up to 25 miles (40.2 km) for the dry season

DistanceMile 3 4 5 7 10 15 25

Km 4.8 6.4 8 11.3 16.1 24.1 40.2

Dose

(mSv)

TEDE 78 49 35 20 10 4.4 2.8

Thyroid CDE 640 420 300 170 88 33 17

Inhalation CDE 60 38 27 15 7.9 3.4 2.0

Cloud shine 1.4 0.96 0.72 0.43 0.22 0.083 0.047

4-day ground

shine17 10 7.1 3.9 2.1 1.0 0.73

25

TEDE = Total Effective Dose Equivalent

CDE = Committed Dose Equivalent

Table 7: Distribution of maximum dose values (mSv) as a function of release

time of 30 hours up to 25 miles (40.2 km) for the rainy season

DistanceMile 3 4 5 7 10 15 25

Km 4.8 6.4 8 11.3 16.1 24.1 40.2

Dose

(mSv)

Total EDE 130 88 83 78 36 7.2 0.85

Thyroid CDE 510 330 240 160 110 57 3.8

Inhalation CDE 65 40 27 17 11 4.4 0.23

Cloud shine 1.4 0.87 0.62 0.4 0.27 0.14 0.016

4-day ground

shine78 62 63 64 26 2.8 0.6

26

TEDE = Total Effective Dose Equivalent

CDE = Committed Dose Equivalent

- In general, the dose decreases properly with respect to distance, the dose is

mainly distributed within about 10 km;

Fig.8: Attenuation of the TEDE (mSv) as a function of distance (km)

for the dry season (left) and rainy season (right)

- In the rainy season (right) the TEDE values near the plant are higher than

those in the dry season (left) within 24 km. This is due to strong deposition in the

rainy season.

27

- It is requested to establish National Emergency Response Board to manage

evolution of the accident and issue timely the appropriate response measures;

- People evacuation within 20 km must be planed.

- Consumption of food and milk in the region must be immediately stopped until

getting the results of sample testing. The public communication, procedure for

radiation emergency preparedness and people evacuation must be considered

and implemented under the guidance of Circular 25/2014/TT-BKHCN [9].

- TEDE value reaches to 1 mSv at about 40 km;

- Within 20 km the dose is about 10 to 15 times over the permitted limit.

This shows that the accident consequences are very serious;

28

Fig.9: Total activity distribution on the ground at 30 hours after the

accident, kBq/m2, within 20 km (left) and 80 km (right)

For the dry season

29

Fig.10: TEDE distribution, Sv, at 40 hours after the accident

Table 8: Affected area with TEDE ≧ 5 mSv

Time (hour) 3 10 20 30 40

Area (km2) 26 44.4 44.4 44.4 44.430

For the rainy season

Fig.11: Total activity distribution on the ground at 30 hours after

the accident, kBq/m2, within 20 km (left) and 80 km (right)

31

Fig.12: TEDE distribution, Sv, at 40 hours after the accident, kBq/m2

Table 9: Affected area with TEDE ≧ 5 mSv

Time (hour) 3 10 20 30 40

Area (km2) 15.3 77.6 103.1 103.1 103.132

- In the dry season the dispersion are mostly in the South direction concentrating in

horizontal narrow area.

- Also in the dry season the affected area is smaller than in the rainy one.

However, the dispersion is directed to the population zone, so impact to public

is still serious.

- The affected areas with TEDE ≧ 5 mSv are, respectively, 44.4 and 103.1 km2

for the dry and rainy seasons.

33

For the dry season

MAP ON 137Cs and 131I RADIOACTIVITY DISTRIBUTIONS

Fig.13: 137Cs radioactivity distribution (> 10 kBq/m2) on

the ground at 30 hours after the accident 34

Fig.14: 131I radioactivity distribution (> 10 kBq/m2) on

the ground at 30 hours after the accident

35

Table 10: Area with 131I radioactivity concentration ≧ 10 kBq/m2

Time (hour) 3 10 30

Area (km2) 342 342 1145

Table 9: Area with 137Cs radioactivity concentration ≧ 10 kBq/m2

Time (hour) 3 10 30

Area (km2) 237 885 885

36

For the rainy season

Fig.15: 137Cs radioactivity distribution (> 10 kBq/m2) on

the ground at 30 hours after the accident 37

Fig.16: 131I radioactivity distribution (> 10 kBq/m2) on

the ground at 30 hours after the accident

38

Table 11: Area with 137Cs radioactivity concentration ≧ 10 kBq/m2

Time (hour) 3 10 30

Area (km2) 58 325 831

Table 12: Area with 131I radioactivity concentration ≧ 10 kBq/m2

Time (hour) 3 10 30

Area (km2) 106 723 1558

39

- For the rainy season after 30 hours most of the amount of the 137Cs radioactivity

is dispersed to the sea by the wind, the affected area with the 137Cs

radioactivity greater than 500 kBq/m2 is about 218 km2

- Dispersion of radioactive substances strongly depends on meteorological

conditions, especially the wind direction plays very important role for the impact

of radioactive dispersion to public.

- In the rainy seasons the radioactive pollution from the release is more serious

than in the dry one due to the stronger deposition. However, in the rainy season

the dispersion is directed to the sea by the wind, so, the impact to public may be

decreased.

40

We accept value of 500 kBq/m2 as a limit for radioactive

pollution of 137Cs and 100 kBq/m2 for 131I as specified by USNRC:

5. Concluding remarks

Structure and functions of the software package NRCDose72 were well

investigated. An input database was built to assess radioactive releases and

environmental impacts using NRCDose72;

Assessments on the released sourced term and public dose distribution within

80 km have been performed for NPP Ninh Thuan 1 under normal working

conditions;

Accident scenarios from the INES levels 4 to 7 were built, based on which the

released source terms, radioactivity and dose distributions have been evaluated;

The calculation results are necessary for considering the emergency response

plan;

The results can support National Regulatory Organization (VARANS) in

reviewing Safety Analysis Report (SAR) for the Ninh Thuan 1 NP project.

41

REFERENCES

[1]. Regulatory Guide 1.109 – Calculation of Annual Doses to Man from Routine Releases of

Reactor Effluents for the Purpose of Evaluating Compliance with 10 CFR Part 50, Appendix I;

U.S. Nuclear Regulatory Commission, 1977.

[2]. INES, The international Nuclear and Radiological Event Scale, User’s Manual, 2008

Edition, IAEA.

[3]. RASCAL42 – Workbook, August 2012

[4]. XOQDOQ: Computer Program for the Meteorological Evaluation of Routine Releases at

Nuclear Power Stations; NUREG/CR-2919; J. F. Sagendorf, J. T. Goll, and W. F. Sandusky,

U.S. Nuclear Regulatory Commission; Washington, D.C; 1982.

[5]. Status report 108-VVER-1200 (V-491).

[6]. Generic Source Term and the Radiological Consequences of Severe Accidents, Jozef

Misak, Safety Assessment Advisory Programme, Malaisia, 9-13, Dec. 2012.

[7]. Subpart D-Radiation Dose Limits for Individual Members of the Public; Part 20-Standards

for protection against radiation; NRC Regulations (10 CFR).

[8]. Thông tư số 19/2012/TT-BKHCN ngày 08/11/2012 của Bộ khoa học và Công nghệ Quy

định về kiểm soát và bảo đảm an toàn bức xạ trong chiếu xạ nghề nghiệp và chiếu xạ công

chúng.

[9]. Thông tư số 25/2013/TT-BKHCN ngày 08/10/2014 của Bộ khoa học và Công nghệ Quy

định về việc chuẩn bị ứng phó và ứng phó sự cố bức xạ và hạt nhân, lập và phê duyệt kế

hoạch ứng phó sự cố bức xạ và hạt nhân.

…42

43