A STUDY ON THE TRITIUM DISTRIBUTION CHARACTERISTICS IN THE ENVIRONMENT

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

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

3. INTRODUCTION Nuclear Power Plants in Operation in Korea

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

5. 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. 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 INTRODUCTION

7. 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 INTRODUCTION

8. 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 INTRODUCTION

9. 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 INTRODUCTION

10. The Measurement Procedures • The Measurement Procedures • The Measurement System • a low background Quantulus 1220TM LSC • Optiphase HisafeTM 3 Scintillant

11. The Measurement Procedures • The Selection of an Effective Window

12. 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. 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

14. 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 The Measurement Procedures

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

16. TABLE.1 The Relative Errors of Three Spectrum Analysis Method The Measurement Procedures

17. 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 Measurement of The Environmental Tritium Activity Level

18. 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 Measurement of The Environmental Tritium Activity Level

19. TABLE 2. The Location of Sampling Points Measurement of The Environmental Tritium Activity Level

20. TABLE 3. The Measured Average Specific Activity of Atmospheric Tritium Measurement of The Environmental Tritium Activity Level

21. 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

22. TABLE 5. The Comparison of the xSMPL and xmodel Measurement of The Environmental Tritium Activity Level

23. 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