Mit

glie

d d

er

Helm

holt

z-G

em

ein

sch

aft

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. tonnes)

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:

S

V

t

CE

Measuring principle

Folie 8

Measuring principle

Folie 9

Measuring equipment

A new device for automatic long-term measurements of the radon exhalation ratewas developed at theResearch 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 11Prototype (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: 1013 – 1014 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

Frequency distribution of the wind direction at Khujand airport (2011)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

North NNE NE ENE East ESE SE SSE South SSW SW WSW West WNW NW NNW

Wind direction

Fre

qu

en

cy

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

Radon exhalation measurements, Degmay uranium tailings dump, 13./14.05.2012

0

50000

100000

150000

200000

250000

300000

350000

400000

450000

500000

0 60 120

180

240

300

360

420

480

540

600

660

720

780

840

900

960

1020

1080

1140

1200

1260

1320

1380

1440

1500

1560

1620

1680

1740

1800

Time (min)

Act

ivit

y co

nce

ntr

atio

n R

n-2

22 (

Bq

/m3 )

measured valuesbest-fit straight lines

4.1 Bq m -2 s -1

04:28

7.2 Bq m -2 s -1

07:28

14.7 Bq m -2 s -1

10:28

9.1 Bq m -2 s -1

13:28

Folie 19

Long-term exhalation measurements

Radon exhalation measurements, Degmay uranium tailings dump, 22. - 25.09.2012

0,00

0,50

1,00

1,50

2,00

2,50

3,00

22.9.12 12:00 23.9.12 0:00 23.9.12 12:00 24.9.12 0:00 24.9.12 12:00 25.9.12 0:00 25.9.12 12:00

Date/time

Ra

do

n e

xh

ala

tio

n r

ate

(B

q m

-2 s

-1)

Radon exhalation measurements, Degmay uranium tailings dump, 18. - 21.06.2012

0,00

0,50

1,00

1,50

2,00

2,50

3,00

18.6.12 12:00 19.6.12 0:00 19.6.12 12:00 20.6.12 0:00 20.6.12 12:00 21.6.12 0:00 21.6.12 12:00

Date/Time

Rad

on

exh

alat

ion

rat

e (

Bq

m-2 s

-1)

Folie 20

Long-term exhalation measurements

18

20

22

24

26

28

0 5 10 15 20 25 30 35 40 45

Time (h)

So

il te

mp

era

ture

(°C

)

Soil temperature (10 cm depth)

Soil temperature (25 cm depth)

12.05.2012 15:23

13.05.2012 08:23

13.05.2012 18:23

14.05.2012 08:23

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