Mitglied der Helmholtz-Gemeinschaft Radon exhalation measurements at the uranium tailings dump Degmay M. Schläger, H. Dederichs, J. Höbig, P. Zoriy, B. Heuel-Fabianek (FZJ) Presented by P. Schmidt (Wismut GmbH)

Folie 2 Khujand (former Leninabad) Chkalovsk (suburb of Khujand) Taboshar (50 km N of Khujand) more than 40 years of uranium production 8 tailings ponds (total 51Mio. tonnes) TP Degmay, largest TMF left behind in Central Asia ( 36 Mio. t onnes )

Folie 3 Forschungszentrum (Research Centre) Jülich one of the biggest scientific institutions in Europe (4.800 staff in 2010) traditional fields of sciences: reactor physics, thermo- nuclear fusion, neutron physics, super computing in the last years turning towards new fields of investi- gations (inter alia health physics) since 2009: engagement in Tajikistan, - radiological investigations at former U mining and milling sites - collaboration with scientists from the Khujand State University, Vostokredmet and Chkalovsk Mining- Metallurgical Institute - project funded by Dr. Erich Schmitt Foundation and FZ Jülich

Folie 4 Degmay Tailings Management Facility

Folie 5 Degmay Tailings Management Facility

Folie 6 Measuring principle Radon exhalation rate means the radon activity which is emitted from the soil surface into the atmosphere per square meter and per second (Bq m -2 s -1 ) It can be measured by the accumulation method

Folie 7 The open face (area S ) of a dome-shaped accumulation container (volume V ) is placed on the surface to be investigated and the radon activity concentration within the container is measured by means of a radon monitor. In the initial phase of the accumulation process the increase of the radon activity concentration C can be approximated by a straight line. From the slope  C /  t of the best-fit curve the radon exhalation rate E (in Bq m -2 s -1 ) of the investigated surface can be calculated: Measuring principle

Folie 8 Measuring principle

Folie 9 Measuring equipment A new device for automatic long-term measurements of the radon exhalation rate was developed at the Research Centre Juelich Patent application in Germany (2011)

Folie 10 After each accumulation period (1 – 2 h) a ball valve in the air outlet of the accumulation container is opened and an external diaphragm pump replaces the radon-bearing air within the container by fresh ambient air until the radon activity concentrations inside and outside the container are nearly equal (ventilation period). After the ventilation period (1 – 3 h) the pump is turned off and the ball valve is closed to make the accumulation container gas-tight again and another accumulation period follows. The diaphragm pump and the ball valve are controlled by a microprocessor and the duration of accumulation and ventilation periods can be adapted to the expected exhalation rates by a programming device. Measuring equipment

Folie 11 Prototype (2011) Measuring equipment

Folie 12 Measuring equipment Improved model (2012)

Folie 13 Measuring equipment The „WISMUT version“) Automatic (continounusly working) Rn exhalation rate measurement equipment (Wismut „Klipp klapp“) Traditional method of Rn exhalation measurement

Folie 14 Long-term exhalation measurements Main aims of the project: 1)Analysis of the dependence of the radon exhalation rate on several influence quantities, such as air temperature, air pressure, soil temperature, soil moisture. 2)Estimation of the total annual radon emission of the Degmay tailings dump (Estimated order of magnitude: – Bq/a). 3)Estimation of the area contaminated by radon daughter products (Pb-210, Po-210) in consideration of wind direction, wind speed, precipitation.

Folie 15 Long-term exhalation measurements

Folie 16 Long-term exhalation measurements Estimated dispersion of radon daughter products (schematic)

Folie 17 Long-term exhalation measurements Installation of the measuring equipment in Degmay

Folie 18 Long-term exhalation measurements

Folie 19 Long-term exhalation measurements

Folie 20 Long-term exhalation measurements Measured quantities: radon activity concentration, air temperature, air pressure, soil temperature, humidity, wind speed, wind direction, precipitation (data from Khujand airport)

Folie 21 Long-term exhalation measurements Outlook: FZ Jülich will continue to measure on the site In the focus: - assessment of the Rn exhalation rate data - particle size specific dust measurements (impactor) [already started] - analysis of samples taken from groundwater investigation wells [already started] - exposure analysis taking all pathways into account

Folie 22 Long-term exhalation measurements Remarks (by P. Schmidt) - commendable initiative by FZ Jülich - promotes international co-operation between scientists (FZ Jülich, Khujand University, Vostokredmet and Chkalovsk Mining-Metallurgical Institute) - thereby a way to build awareness on side of young scientists (students) for protection of the environment - contribution to staff qualification