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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
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