1. A STUDY ON THE TRITIUM DISTRIBUTION CHARACTERISTICS IN THE ENVIRONMENT 2006. 6. 27 Goung-Jin Lee, Hee-Geun Kim 2006 RETS

2.  Introduction  Measurement Procedure  Measurement of Environmental Tritium Activity Level  Conclusions Topics for Presentation

3. 2006 RETS Nuclear Power Plants in Operation in Korea INTRODUCTION

4. 2006 RETS INTRODUCTION Nuclear Power Plants under Construction or Planning in Korea

5. 2006 RETS  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

6. 2006 RETS 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

7. 2006 RETS 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

8. 2006 RETS 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

9. 2006 RETS 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

10. 2006 RETS  The Measurement Procedures  The Measurement System a low background Quantulus 1220 TM LSC Optiphase Hisafe TM 3 Scintillant The Measurement Procedures

11. 2006 RETS  The Selection of an Effective Window The Measurement Procedures

12. 2006 RETS  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 The Measurement Procedures

13. 2006 RETS  The Calculation of a Sample Activity  Comparison of total counting rates in an effective window between the sample and the standard source  A SMPL = (CPM SMPL - CPM BKG ) / CPM STD × A STD A SMPL = the calculated activity of sample(Bq/L) A STD = the activity of standard source(Bq/L) CPM = the counting rate in the window(61~165) The Measurement Procedures

14. 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

15. 2006 RETS The Measurement Procedures The measured Background Spectrum The Measured Spectrum of 5 Bq/L Tritiated Water Sample

16. 2006 RETS The Measurement Procedures TABLE.1 The Relative Errors of Three Spectrum Analysis Method Analysis Sample 1~200 Ch Total Counts 61~165 Ch Total Counts 61~165 Ch Weighting Method 5 Bq/L12.8 %4.5 %1.7 % 10 Bq/L-5.7 %-2.1 %-0.9 %

17. 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

18. 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

19. 2006 RETS Measurement of The Environmental Tritium Activity Level  TABLE 2. The Location of Sampling Points DirectionDistances(Km)Name Point ANE2.1Hongnong Point BSSE6.0Bupsung Point CSSE16.7YongGwang Point DESE44.0Gwangju

20. 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 A2.676.394.53 Point B<1.35<0.89<1.12 Point C<1.73<1.12<1.43 Point D<1.27<0.98<1.13

21. 2006 RETS  Comparison of the Tritium Concentration in the Air = tritium concentration in the air(Bq/m 3 ) = measured tritium specific activity (Bq/kg) = absolute humidity in the air (kg/m 3 ). = average tritium release rate(Bq/sec) Measurement of The Environmental Tritium Activity Level

22. 2006 RETS  TABLE 5. The Comparison of the x SMPL and x model Measurement of The Environmental Tritium Activity Level X model (Bq/m 3 ) x SMPL (Bq/m 3 ) X model /X SMPL Aug.2005Feb.2005 Point A1.320.06720.031719.7~41.6 Point B0.490.01590.006430.8~76.6

23. 2006 RETS  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