a study on the tritium distribution characteristics in the environment
DESCRIPTION
2006 RETS. A STUDY ON THE TRITIUM DISTRIBUTION CHARACTERISTICS IN THE ENVIRONMENT. 2006. 6. 27 Goung-Jin Lee, Hee-Geun Kim. Introduction Measurement Procedure Measurement of Environmental Tritium Activity Level Conclusions. Topics for Presentation. INTRODUCTION. - PowerPoint PPT PresentationTRANSCRIPT
A STUDY ON THE TRITIUM DISTRIBUTION CHARACTERISTICS IN THE ENVIRONMENT
2006. 6. 27
Goung-Jin Lee, Hee-Geun Kim
2006 RETS
2006 RETS
Introduction Measurement Procedure Measurement of
Environmental Tritium Activity Level
Conclusions
Topics for Presentation
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Nuclear Power Plants in Operation in Korea
INTRODUCTION
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INTRODUCTION
Nuclear Power Plants under Construction or Planning in Korea
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Multiple Nuclear Power Plants in Each Site
Can cause much environmental impacts to the environment
Calculated Maximum Individual Doses may exceed the limiting value required by Regulatory Body
Public concerns can be increased
Make it difficult to construct or operate NPPs
INTRODUCTION
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INTRODUCTION
Maximum Individual Dose Calculation Procedures
MEASURE the amount of annually released radioactive effluents
CALCULATE Dilution Factor using weather data : Gaussian Plume Model
CALCULATE Air Concentration and Ground Deposition of radioactive isotopes• Exposure from Inhalation, Plume Shine, Ground Shine Pathway
Transfer Model to Food Chain• Exposure from Ingestion Pathway
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INTRODUCTION
Conservatisms included in the Calculated Individual Dose
In our experiences, the calculate Maximum Individual Doses
are very high compared to the measured Actual Doses
because of the Conservatism included in
• Dilution Factor or x/Q calculation
• Transfer model to Food Chain
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INTRODUCTION
The Purposes of This Paper Is
by measuring the tritium radioactivity around a nuclear power
plant
to quantitatively investigate the conservatism included in the
Calculated Dilution Factor
to suggest new approach of maximum dose calculation based
on the measured data
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INTRODUCTION
Why Tritium Is Selected ?
In Korean NPPs, 60~90% of total off-site Maximum Individual
Doses are due to the gaseous tritium release
Tritium is easy to measure in the points of
• Activity Level
• Simple pre-treatment process of samples
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The Measurement Procedures
The Measurement System
• a low background Quantulus 1220TM LSC
• Optiphase HisafeTM 3 Scintillant
The Measurement Procedures
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The Selection of an Effective Window
The Measurement Procedures
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The Selection of an Effective Window
Lose 10% of tritium counts in each tail
Greatly reduce background counts
61~165 channel minimizes MDA
about 1.5 Bq/L MDA was obtained by using 61~165 channel, with
480min detection time
EVT
BMDA
2/1466
The Measurement Procedures
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The Calculation of a Sample Activity
Comparison of total counting rates in an effective window between the sample and the standard source
ASMPL = (CPMSMPL - CPMBKG) / CPMSTD × ASTD
• ASMPL = the calculated activity of sample(Bq/L)
• ASTD = the activity of standard source(Bq/L)
• CPM = the counting rate in the window(61~165)
The Measurement Procedures
2006 RETS The Measurement Procedures
The Calculation of a Sample Activity
Weighting by tritium spectrum
CPM SMPL,i = the counting rate of sample at channel i
CPM BKG, i = the counting rate of background sample at channel i
CPM STD, i = the counting rate of standard source sample at
channel i
STD
iiSTD
iiSTDiBKGiSMPL
SMPL ACPM
CPMCMPCPMA
165
61
2,.
165
61,,, )(
2006 RETS The Measurement Procedures
The measured Background Spectrum
The Measured Spectrum of 5 Bq/L Tritiated Water Sample
2006 RETS The Measurement Procedures
TABLE.1 The Relative Errors of Three Spectrum Analysis Method
Analysis
Sample
1~200 ChTotal Counts
61~165 ChTotal Counts
61~165 ChWeighting Method
5 Bq/L 12.8 % 4.5 % 1.7 %
10 Bq/L -5.7 % -2.1 % -0.9 %
2006 RETS Measurement of The Environmental Tritium Activity Level
Sample Selection
HTO in the water, river, ground water, underground water
: very low Specific Activity due to dilution
HTO in the rain : much fluctuations due to the variations of the weather conditions
HTO in the air : comparatively high Specific Activity and
gives stable value
2006 RETS Measurement of The Environmental Tritium Activity Level
Sampling Method
HTO in the air was Condensed, by using commercially available electric dehumidifier
Relative humidity and the Temperature were measured to determine the Absolute Humidity
4 measuring points, 2 seasons, eight samples in each season
2006 RETS Measurement of The Environmental Tritium Activity Level
TABLE 2. The Location of Sampling Points
Direction Distances(Km) Name
Point A NE 2.1 Hongnong
Point B SSE 6.0 Bupsung
Point C SSE 16.7 YongGwang
Point D ESE 44.0 Gwangju
2006 RETS Measurement of The Environmental Tritium Activity Level
TABLE 3. The Measured Average Specific Activity of Atmospheric Tritium
Aug.2005
(Bq/Kg)
Feb.2005
(Bq/Kg)
Annual Average
(Bq/Kg)
Point A 2.67 6.39 4.53
Point B <1.35 <0.89 <1.12
Point C <1.73 <1.12 <1.43
Point D <1.27 <0.98 <1.13
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Comparison of the Tritium Concentration in the Air
= tritium concentration in the air(Bq/m3) = measured tritium specific activity (Bq/kg) = absolute humidity in the air (kg/m3).
= average tritium release rate(Bq/sec)
Measurement of The Environmental Tritium Activity Level
absSMPLSMPL HA
SMPLSMPLAabsH
elHel QQ modmod )/(3
3HQ
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TABLE 5. The Comparison of the xSMPL and xmodel
Measurement of The Environmental Tritium Activity Level
Xmodel
(Bq/m3)
xSMPL (Bq/m3)
Xmodel /X SMPL
Aug.2005 Feb.2005
Point A 1.32 0.0672 0.0317 19.7~41.6
Point B 0.49 0.0159 0.0064 30.8~76.6
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We developed measurement procedures for environmental tritium(HTO) in the air
Within about 2.0 Km from the NPPs, there is measurable
tritium level increases compared with the natural backguound
Results show that the presently used DF of gaseous effluents are overestimated more than 20 times.
Conclusions