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Radon Variations and Rock Stress at L-Vianden Pumping Station

Explore radon fluctuations in an underground gallery at the L-Vianden Pumping & Storage Facility. Learn about the unique rock stress conditions, geology, boreholes, radon signals, and water level correlations. Discover insights into gravitational effects on radon levels and the impact of fissure systems. Dive into the technical aspects of radon sensors, calibration methods, and computer maintenance recommendations for optimal data collection.

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Radon Variations and Rock Stress at L-Vianden Pumping Station

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  1. Radon and variable rock stress Radon variations in an underground galleryPumping Storage Facility, SEO, L-Vianden Francis Massen, Physics Lab, Lycée Classique DiekirchAntoine Kies, LPR, Université du Luxembourg

  2. Upper basins 1 & 2 basin 1 basin 2

  3. SEO main figures: Construction : 1959 to 1964 Maximum used volume of basins : 6.8 million m3 Maximum water level change : 16 m ~ 1.6 at Flow during power generation : 432.5 m3/s Mean daily power generation time: 4.25hMean daily pumping time: 7.25h www.seo.lu

  4. Water outlets

  5. Location of stations B2_stat1 B2_stat2 B1_stat2 B1_stat1 B1_stat3 B2_stat3( in use since July04) galleries

  6. Geology basin1 basin2

  7. Fractures and fillings (J. Bintz, 1964) Voids were filled with concreteduring construction work!

  8. Interior of gallery

  9. Boreholes ~16cm diameter 1m concrete 40cm rock

  10. Difference in radon signal between basin1 and basin2 21Nov02 – 13Dec02, 4 stations [100uRoe/h ~1uSv/h ~100 Bq/m3 EER]

  11. Basin1, station1: influence of atmospheric pressure variations May02 Possible anticorrelation with atmospheric pressure …. large voids in underground?

  12. Basin2 stat1: radon and water level (station1, 21Nov02-13Dec02)

  13. Basin2 stat2: radon and water level (station2, 02 – 30 Apr.04)

  14. Basin2: stations 1,2,3 : 04Aug-27Sep 2004Vanishing signal…. Autocorrelation of radon 24h stat1 190m stat2 245m stat3 why? approx.direction offissures

  15. Gravitational effects stat1stat2stat3

  16. Water level modulates existing radon background 24 hours Emptying basin 2: radon regains background level in ~24h

  17. Time lag between radon and water level: Basin2, station1 21Nov02 - 13 Dec02

  18. Time lag between radon and water level: Basin2, station2 21Nov02 - 13 Dec02

  19. Is the delay between radon and water level ~ constant?…. YES!

  20. More time lags between radon and water level: from…to days B2stat1 B2stat2 B2stat3 21Nov02-05Feb03 77 93 246 12-18Jun03 7 36 263 02-30Apr04 29 109 278 04Aug-27Sep04 55 205 240 (300)______________________________________________________ ? ?

  21. Relation between radon concentration and water level: B2 stat1

  22. Better fit: parabolic

  23. Relation between radon concentration and water level: B2 stat2

  24. Explication? Basin 1 B1_stat3 Basin 2 stat1 Stations 1 and 2 lie in a fissuresystem with one dominatingorientation  preferentialmigration path for radon  strong water level dependance stat2 Fissure system is random: no dominant migration path  no water level dependance stat3

  25. RM80 Aware counter “Pancake” Geiger tube (,,) Sensor driven by serial or parallelport of (notebook) computerSensor is not waterproof: usually will be sealed in PET bag with calcium chloride CaCl2 as desiccant.Many humidity related problems! Price: ~319 US$www.aw-el.com

  26. Calibration of RM80 Calibration was done in-situ , (in gallery with no ventilation)comparing readings of a RM80 and a Alphaguard: borehole

  27. RM80 and Radim sensor (borehole B2 stat2)

  28. Computer problems 1. Protection against humidity: never shut down! 2. Protection against fine dust: seal floppy drive by tape; install Laplink in case of floppy malfunction 3. Use only notebooks: power outage protection! 4. Save backlight tubes: shut off screen 5. Use surge protectors (many lightning impacts!) 6. Combat computer clock drift: RIGHTIME software 7. Use only old equipment!

  29. Software Very large data files ( > 150000 lines): use DADiSP

  30. DADiSP www.dadisp.com Price: 1995 US$ Same as full version, limited in number of windows and data size

  31. Merci de votre attention… antoine.kies@uni.lu francis.massen@education.lu et claude.boes@bigfoot.com http://meteo.lcd.lu/papers/http://www.speleo.lu

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