Assessment of (222)Rn emanation from ore body and backfill tailings in low-grade underground uranium...

RESEARCH ARTICLE

Assessment of 222Rn emanation from ore body and backfilltailings in low-grade underground uranium mine

Devi Prasad Mishra & Patitapaban Sahu &

Durga Charan Panigrahi & Vivekanand Jha &

R. Lokeswara Patnaik

Received: 7 July 2013 /Accepted: 5 September 2013 /Published online: 21 September 2013# Springer-Verlag Berlin Heidelberg 2013

Abstract This paper presents a comparative study of 222Rnemanation from the ore and backfill tailings in an undergrounduranium mine located at Jaduguda, India. The effects ofsurface area, porosity, 226Ra and moisture contents on 222Rnemanation rate were examined. The study revealed that thebulk porosity of backfill tailings is more than two orders ofmagnitude than that of the ore. The geometric mean radonemanation rates from the ore body and backfill tailings werefound to be 10.01×10−3 and 1.03 Bq m−2 s−1, respectively.Significant positive linear correlations between 222Rn emana-tion rate and the 226Ra content of ore and tailings wereobserved. For normalised 226Ra content, the 222Rn emanationrate from tailings was found to be 283 times higher than theore due to higher bulk porosity and surface area. The relativeradon emanation from the tailings with moisture fraction of0.14 was found to be 2.4 times higher than the oven-driedtailings. The study suggested that the mill tailings used as abackfill material significantly contributes to radon emanationas compared to the ore body itself and the 226Ra content andbulk porosity are the dominant factors for radon emanationinto the mine atmosphere.

Keywords Underground uraniummine . Ore body . Backfilltailings . 222Rn emanation rate . 226Ra content . Porosity

Introduction

Uranium is the backbone of any programme which aims atexploiting nuclear energy for peaceful purposes. Generally,uranium ore contains natural uranium comprising of 238U(99.275 %), 235U (0.72 %) and 234U (0.005%). Due to highestabundance of 238U in nature, the major quantity of radioactiv-ity is due to 238U and its decay products. Radiological hazardsassociated with uranium mining arise mainly from externalexposure to beta and gamma radiations from the ore body andinternal exposure to radon and its short-lived daughter prod-ucts. In addition, the long-lived alpha and beta emitters causeradiological hazards. However, in low-grade uranium mines(U3O8 content<0.1 %), the hazards due to external exposureand long-lived activity are not significant (Raghavayya 1976).The increased risk of lung cancer due to the exposure of short-lived decay products of 222Rn has been reported elsewhere(Darby et al. 2005; Gulson et al. 2005). Monitoring of radonconcentration inside uranium mines and in the environmenthas been a matter of concern since last several decades tominimise the extent of inhalation exposure of occupationalworkers (IAEA 1992; ICRP 2010).

Latest studies pertaining to the radon emanation in uraniummining and milling facilities of different parts of the worldsuch as USA, Australia, Canada, China, India and Japan areavailable elsewhere (Jha et al. 2000; Ferry et al. 2001; Mudd2008; Sahoo et al. 2010; Bochiolo et al. 2012; Tan et al. 2012).However, studies on radon emanation from in situ ore bodyand backfill material in underground uranium mines incorpo-rating the parametric effects have rarely been reported in thepast literatures. Archibald and Nantel (1984) used a method inwhich a steel chamber provided with several valves wascemented on the mine walls and radon samples were drawnfrom the chamber at intervals of several hours up to 50 h forcomputation of emanation rate from the in situ rock inCanadian uranium mine. Raghavayya and Khan (1973)

Responsible editor: Philippe Garrigues

D. P. Mishra (*) : P. Sahu :D. C. PanigrahiDepartment of Mining Engineering, Indian School of Mines,Dhanbad 826 004, Indiae-mail: [email protected]

V. Jha : R. L. PatnaikEnvironmental Assessment Division, Bhabha Atomic ResearchCentre, Trombay, Mumbai 400 085, India

Environ Sci Pollut Res (2014) 21:2305–2312DOI 10.1007/s11356-013-2137-4

studied the radon emanation rate from the mill tailings used asbackfill material in an Indian uraniummine using a steel drumattached with a stopcock through which the accumulatedradon sample in the drum was collected after a time lapsevarying between 7 and 65 h. However, the aforementionedtechniques had some drawbacks. The former is very complex,expensive and time consuming for making the arrangement ofexperimental setup, whereas the latter may have high uncer-tainties in the results due to the longer period of measurementand back diffusion. Dwaikat et al. (2010) investigated thespecific radon exhalation from mine rocks based on the radonmeasurements by means of CR-39 detectors in which theuncertainty of measurements depends on several factors, suchas exposure period, etching process and calibration.

In the present study, we investigated the in situ radonemanation rate from ore body and backfill tailings in a urani-um mine using comparatively simple, quick and cheapertechniques giving low uncertainties in the results. The influ-ence of several parameters such as 226Ra content, porosity,density, moisture content and surface area on radon emanationrate from ore body and backfill materials were also examined.

Materials and methods

Study area

This study was carried out in Jaduguda uranium mine locatedat Singhbhum shear zone in the eastern part of India. Figure 1shows the location of the investigated mine and the differentlithological units around it. The mine has two parallel mine-able lodes extending as thin veins from surface following thegeneral trend of schistosity with fairly uniform persistenceboth along the strike (600 m length) and dip (900 m depth).The Southern lode, known as foot-wall lode, spreads from eastto west. The Northern lode or hang-wall lode is traceable onlyin the east. Uranium bearing minerals in Jaduguda mine occurin the Precambrian meta-sedimentary rocks, which are highlyfolded and sheared. The principal lithological rock units ofJaduguda are autoclastic conglomerate (brecciated quartzite),quartz–chlorite–biotite–magnetite schist, biotite–chloriteschist and epidiorite, of which first two rock units host themineralisation (Sarangi and Singh 2006). The primary urani-um minerals of Jaduguda ore are uraninite and pitchblende,and the most common secondary mineral is autunite.

Horizontal cut-and-fill method using de-slimed coarserfraction mill tailings used as backfill is the principal stopingmethod adopted in Jaduguda mine. The tailings are pumpedinto the mine in the form of aqueous slurry for backfilling,which settle and consolidate by its own weight to stabilise theexcavations after draining out of water.

Twenty-two numbers of broken ore samples were collectedfrom different stopes for determination of physical and

radioactive properties in the laboratory. The samples of drillcuttings were collected from 17 drill holes made in the rockwalls where the radon emanation studies were carried out.Core samples of settled backfill tailings were collected from16 locations of eight backfilled stopes by inserting a stainlesssteel cylinder. The collected samples were placed in plasticvials marked with the location and date of sample collection.The physical and radioactive properties of the tailings weredetermined in the laboratory.

Measurement of physical properties

The moisture content of ore samples and backfill tailings wasdetermined by heating the samples at 105±5 °C for 24 h as perstandard ASTM D2216. The bulk density of the ore sampleswas determined by dividing the mass of the oven-dried sam-ples by their volume determined from water displacementmethod. For the bulk density determination of backfill tail-ings, an undisturbed core of backfill material was collectedinserting a stainless steel cylinder of known volume. Porosity(Φ ) of the tailings was estimated from

Φ ¼ 1−ρ=ρg ð1Þ

Where ρ is the bulk density of material (kg m−3) and ρg isthe specific gravity (kg m−3).

For determination of the uranium ore porosity, oven-driedore samples were dipped in distilled water for a time period>4 days to ensure maximum absorption. Porosity was thencalculated as the ratio of volume of water absorbed in the porespace to the volume of sample. The fraction of pore spacefilled with water or moisture saturation (m) was estimatedfrom (Rogers and Nielson 1991)

100m ¼ ρMw

ρwΦð2Þ

WhereMw is the water content in the material (dry weight,%) and ρw is the density of water (kg m−3).

The particle size analysis of the oven-dried tailings wascarried out with a standard sieve deck. The specific surfacearea of the tailings (A, cm2 g−1) was calculated with therelation (Raghavayya 1976)

A ¼ KS

MKVd

X

j¼1

nm j=X j

��ð3Þ

Where Ks is the surface area shape factor,Kv is the volumeshape factor, d is the true solid density (g cm−3), n is the totalnumber of groups, mj is the mass of backfill material fallinginto the j th group (g), Xj is the mean particle size in j th group(μm) andM is the total mass of sample (g). Since the backfilltailings predominantly consist of quartz, the volume (Kv) andsurface area (Ks) shape factors for quartz were taken as 0.24and 1.95, respectively (Saha 1972).

2306 Environ Sci Pollut Res (2014) 21:2305–2312

Determination of 222Rn emanation rate from the ore body

The radon emanation rate from in situ ore body in the minewas determined by making drill holes in ore body (Fig. 2),which act as chamber for accumulation of radon emanatedfrom the walls of the ore body. Wet drilling method wasadopted, and drill cuttings were collected for determination

of 226Ra content. The drill hole was then dried and cleanedwithcompressed air. It was sealed with the rubber cork throughwhich a glass tube fitted with stopcock was introduced. Theattached tube reached up to the middle of the hole. Sealant waxwas used in the gap between rubber cork and drill hole toprevent air leakage. The radon gas emanated from the rockwalls was allowed to accumulate in the drill hole chamber. Air

Singhbhum Shear Zone

JharkhandJharkhand

INDIA

Fig. 1 Location of the Jadugudamine and different lithologicalunits around it

Glass tube

Drill hole

Ore body

Ore body

Stopcock

Rubber cork

Wax seal

Filter holder

Filter paper

Scintillation cell

Swagelok quickconnector

Flexible tube

Fig. 2 Experimental setup for insitu measurement of radonemanation rate from uranium orebody

Environ Sci Pollut Res (2014) 21:2305–2312 2307

samples were drawn from the drill hole into evacuated scintil-lation cells through the glass tube fitted with filter paper atdifferent time intervals up to 6 days. The scintillation cells wereconnected to the photomultiplier assembly after a delay periodof about 200 min to ensure equilibrium between the radon andits progeny in the cell. Thereafter, the alpha counts were notedfor 10 min at 95 % confidence level to estimate the radonactivity concentration (C) of each sample using the equation(Raghavayya 1981; Panigrahi et al. 2005)

C ¼ 6:967� 10−5c

EVse−λτ 1−e−λTð Þ ð4Þ

Where c is the total counts obtained during counting dura-tion “T”, E is the efficiency of the system (%), Vs is thevolume of scintillation cell (m3), τ is the delay time afterend of the sampling (s) and T is the counting duration (s).The efficiency of the system was 74 %, which was calibratedwith a standard scintillation cell having activity of 21,500 cpm(counts per minute) and 75 % efficiency.

The curve of 222Rn activity concentration versus builduptime (accumulation curve) is shown in Fig. 3. In our study, thesampling for determination of 222Rn emanation rate werecarried out during the buildup periods varying from 87 to1445 min, which lie in the linear region of the accumulationcurve. The radon emanation rate (J ) from the ore body wascomputed by means of the relation

J ¼ λ Vs þ Vð Þ Ct−C0e−λt� �

A 1−e−λtð Þ ð5Þ

Where C0 is the initial radon concentration at t = 0(Bq m−3), Ct is the radon concentration after time “t”(Bq m−3), Vs is the volume of scintillation cell (m3), V is thedrill hole volume (m3) and λ is the decay constant of radon,s−1.

The experiment was repeated at 17 drill holes made in 12stopes of the Jaduguda mine. The drill holes were of 38 mmdiameter and 1.22 to 3.5 m length.

Determination of 222Rn emanation rate from backfill tailings

Radon emanation rate from the backfill materials inside themine was measured using a cylindrical accumulator (17 cm indiameter and 30 cm height). The accumulator was open at oneend, and the other end was closed with a circular disk throughwhich a glass tube provided with a stopcock was inserted asshown in Fig. 4. It was buried up to a depth of 5 cm over thesurface of tailings for proper sealing and care was taken toavoid any disturbance of the surface texture of the tailings. Theradon gas emanated from the backfill tailings was allowed toaccumulate in the accumulator. Air samples were drawn intothe scintillation cells though the glass tube fitted with filterpaper for preventing the entry of radon daughters. It has beenreported that at long buildup time, back diffusion is very mucheffective and correction factor becomes more significant. Insmall accumulation chamber, back diffusion correction factoris about two for accumulation period of 1.5 h, which reducesexponentially with decrease in buildup time (Mayya 2004). Theradon level reaches measurable activity concentration in theaccumulator within few hours (Jha et al. 2000). Thus, in ourstudy, the sampling for emanation studies was done during thebuildup periods varying from 27 to 55 min to minimise theback diffusion correction factor. The radon emanation rate fromthe tailings was computed using Eq. (5). This experiment wasrepeated at 16 locations in eight backfilled stopes of the mine.

Measurement of 226Ra content

The emanometry technique was used for measurement of226Ra content in the samples (Raghavayya 1990; Jha et al.2010). A known quantity (2 g) of the oven-dried powderedsample was subjected to repeat leaching using conc. HNO3

mixed carefully with a small quantity of H2O2 for removingorganic matter present in the samples. The mixture was thenfiltered and made up to 100 ml maintaining the resultant acid

020000400006000080000

100000120000140000160000180000200000

0 50 100 150 200

222 R

n ac

tivi

ty c

once

ntra

tion

(Bq

m-3

)

Buil-up time (Hours)

Fig. 3 Variation of 222Rn activity concentration with buildup time in drillhole

Scintillation cell

Swagelok Quick Connector

Flexible tube

Stopcock

Circular disk

Glass tube

Filter paper

Accumulator

Backfill material surface

Fig. 4 Setup for measurement of radon emanation rate from backfilltailings


normality at 4 N. Fifty milliliters of the leach aliquot wastransferred to a radon bubbler. At the beginning, a vacuumpump was used for sucking air through the sample solution toscrub it for about 5 min and purge the solution of dissolvedradon. The radon samples were drawn from the bubbler intoan evacuated scintillation cell after a suitable time period(preferably>20 days to ensure secular equilibrium between226Ra and 222Rn) depending on the expected 226Ra activity ofthe sample. The alpha activity in the cell was counted after adelay period of about 200 min to ensure secular equilibriumbetween radon and its short-lived progeny. The background ofthe cell was normally at 0.5 cpm, and average efficiency was85 %. Based on the alpha counts and sampling parametersactivity, 226Ra activity (Bq kg−1) in the ore samples wasestimated at 95 % confidence interval from the relation

226Ra ¼ cλ3Ee−λτ 1−e−λθð Þ 1−e−λTð Þ �

V ts � 1000

Vsb � mð6Þ

Where Vts is the total volume of solution prepared from thesample (100 ml), Vsb is the volume of the solution loaded inbubbler (50 ml), τ is the delay time after end of the sampling(s), T is the counting duration (s), θ is the buildup time inbubbler (s) and m is the weight of the powder sample (g).

Results and discussion

Physical properties of the ore and backfill tailings

The physical properties of the ore and backfill tailings aresummarised in Table 1. The bulk density, true density andporosity of the ore were found to be 2,770 kg m−3,2,778 kg m−3 and 0.31 %, respectively, whereas for backfilltailings, values were found to be 1,790 kg m−3, 2,700 kg m−3

and 33.3 %, respectively. The moisture content of the ore andtailings were determined as 1.32 and 11.48 %, respectively.The porosity of the tailings was found to be about 107 timesmore than that of the uranium ore. The particle size analysisrevealed that the backfill tailings are predominantly of >75 μm size with specific surface area of 460.42 cm2 g−1.The mass and surface area of 100 cm3 volume of ore wereestimated to be 277 g and 106.42 cm2, respectively. When thisore piece was crushed to the representative size of backfilltailings, the surface area of the crushed ore became127,500 cm2, i.e. the surface area was increased about 1,198times than the original ore piece.

Radon emanation rate from ore body

Table 2 presents the statistical parameters of 226Ra content andin situ radon emanation rate of ore, which vary from 363.3 to19,950.4 Bq kg−1 and 0.22 to 51.84×10−3 Bq m−2 s−1, respec-tively. The results showed that the two parameters are lessskewed, and the kurtosis in these two cases is much lesser thanthree. This reflects symmetrical nature of the distribution andprobably the distribution is normal. The geometric mean ofradium content and radon emanation rate were worked out tobe 3,205.72 Bq kg−1 and 10.01×10−3 Bq m−2 s−1, respective-ly. The 222Rn emanation rate of porous rock types such as

Table 1 Physical properties of the ore and backfill tailings

Parameters Ore Backfill tailings

True density, kg m−3 2,778 2,700

Bulk density, kg m−3 2,770 1,790

Porosity, % 0.31 33.3

Moisture content, % 1.32 11.48

Particle size, μm – >75

Specific surface area, cm2 g−1 – 460.42

Table 2 Statistical parameters of226Ra content and radon emana-tion rate of ore and backfilltailings

Parameters Ore Backfill tailings

226Ra content(Bq kg−1)

222Rn emanation rate(×10−3 Bq m−2 s-1)

226Ra content(Bq kg−1)

222Rn emanation rate(Bq m−2 s−1)

Minimum 363.3 0.22 124 0.12

Maximum 19,950.36 51.84 5,166 9.53

Mean 5,816.60 18.11 1,719.75 2.04

Median 3,612.24 13.34 1,522.5 1.43

Standard deviation 5,807.98 15.66 1,639.52 2.60

Kurtosis 0.77 −0.19 0.54 4.38

Skewness 1.24 0.86 1.19 2.15

Geometric mean 3,205.72 10.01 1,019.64 1.03

Geometricstandarddeviation

3.50 4.17 3.20 3.51


sandstone and shale in American uranium mines were foundto be 18.5 and 5 Bq m−2 s−1, respectively (Thompkins 1982).Franklin et al. (1982) reported the 222Rn emanation rate of0.185 Bq m−2 s−1 for conglomerate rock in a Canadian urani-um mine. Mudd (2008) reported the 222Rn exhalation rate inthe range of 0.15–1.94 Bq m−2 s−1 from Australian uraniumbearing rocks. Comparatively, the radon emanation rate fromJaduguda ore was found to be much lower than the valuesreported by the aforementioned studies. This is mainly due tolow ore grade and nonporous (compact and high density)meta-sedimentary characteristic of Jaduguda mine rock. Itmay also be due to the lower radioactivity of quartz presentin the bulk ore (Sakoda et al. 2010).

The variation of radon emanation rate with 226Ra content ofore presented in Fig. 5 showed a very good correlation(r = 0.99). Therefore, it is evident that 226Ra content has moresignificant impact on the radon emanation. The empiricalrelationship between 222Rn emanation rate and 226Ra contentobtained from Fig. 5 can be used for quick prediction of 222Rnemanation rate from uranium ores of petrophysical character-istics similar to those of the Jaduguda mine.

222Rn emanation rate from backfill tailings

The statistical parameters of 226Ra content and radon emana-tion rate of 16 backfilled locations in eight stopes arepresented in Table 2. The results revealed that the 226Racontent and radon emanation rate are skewed depicting asym-metrical natures of the distribution. However, for log-transformed data set, the skewness was found to be −0.3 for226Ra content and −0.01for radon emanation rate and kurtosisin these two cases were far less than three. The results thusreflect log normal distribution of the data set. 226Ra contentand 222Rn emanation rate over the surface of the backfill are inthe ranges of 124–5,166 Bq kg−1 and 0.12–9.53 Bq m−2 s−1,respectively, with geometric mean values of 1,019.64 Bq kg−1

and 1.03 Bq m−2 s−1. The radon emanation rate values werefound to be significantly higher as compared to the values(0.47–1.53 Bq m−2 s−1) reported for the same mine earlier byRaghavayya and Khan (1973). This variation may be due tovariation of in situ 226Ra content, variation in surface textureand inherent characteristics of the tailings.

Bernhardt et al. (1975) reported that the radon emanationrate from the tailings in Southern Utah mines in the USAwerein the range of 4.8–24 Bq m−2 s−1. Franklin et al. (1982)reported the radon emanation rate of 203.5 Bq m−2 s−1 fromthe backfill material in a Canadian uranium mine. Mudd(2008) reported that the 222Rn emanation rate from the tailingsin an Australian uranium mine varied in the range of 2.80–14.17 Bq m−2 s−1. As compared to these earlier reportedvalues, the radon emanation rate from backfill tailings inJaduguda mine was found to be much lower. This is mainlydue to the lower ore grade, and hence, lesser 226Ra content intailings.

The variation of radon emanation rate with 226Ra content inbackfill tailings shown in Fig. 6 indicates a significant positivecorrelation. However, the correlation coefficient (r = 0.95)between the 222Rn emanation rate and 226Ra content obtainedin this case was comparatively lesser than the coefficient of0.99 obtained in the case of ore body. This may be attributeddue to the higher bulk porosity, moisture content and 222Rnadsorption of the tailings.

The relative change of radon emanation rate from the back-fill tailings with the moisture fraction is shown in Fig. 7. Therelative radon emanation rate from the tailings havingmoisturefraction of 0.14 was found to be 2.4 times higher than the driedtailings. Similar findings have also been reported in the litera-ture elsewhere (Strong and Levins 1982; Bossew 2003).However, Fig. 7 clearly shows that beyond a moisture contentof 0.14, the emanation rate gradually started declining withsaturation. This may be due to the low diffusion coefficient of

J= 0.0027 226Ra+ 2.5649r = 0.99

0

10

20

30

40

50

60

0 5000 10000 15000 20000 25000

222R

n em

anat

ion

rate

(×10

-3B

q m

-2s-1

)

226Ra content (Bq kg-1)

Fig. 5 Relationship of radon emanation rate with 226Ra content of ore

J = 0.0015 226Ra - 0.5493r = 0.95

0

2

4

6

8

10

12

0 1000 2000 3000 4000 5000 6000

222R

n em

anat

ion

rate

(Bq

m-2

s-1)

226Ra content (Bq kg-1)

Fig. 6 Relationship of radon emanation rate with 226Ra content ofbackfill tailings

0

0.5

1

1.5

2

2.5

3

0 0.2 0.4 0.6 0.8 1

Rel

ativ

e 22

2R

n em

anat

ion

Moisture fraction

Fig. 7 Variation of relative 222Rn emanation with moisture fraction inbackfill tailings


radon in the saturated tailings (Meslinn et al. 2010). Mudd(2008) also reported the radon emanation rate for dry, moistand saturated mill tailings in Australian uranium mine of 7.82,14.17 and 2.80 Bq m−2 s−1, respectively. Therefore, it isevident that the presence of low moisture content may enhancethe radon emanation. Further, it may be mentioned that whenthe pores in the material are filled with water, the recoiling ionescaping into the pores encounters a dense absorber and has agreater probability of remaining in the pores. Hence, it causesreduction in radon emanation from the material.

Comparison of 222Rn emanation rate from ore bodyand backfill tailings

The mean specific radium content of the tailings was found tobe 1,719.75 Bq kg−1, which is about one third of the meanspecific radium content of the Jaduguda uranium ore(5,816.60 Bq kg−1). In spite of low radium content, the meanradon emanation rate of backfill material (2.04 Bqm−2 s−1) wasfound to be much higher than the mean radon emanation rate ofthe ore (18.11×10−3 Bq m−2 s−1). From Fig. 5, the radonemanation rate from the ore body with specific radium contentequivalent to that of backfill tailings (1,719.75 Bq kg−1) wascomputed to be 7.2×10−3 Bq m−2 s−1. On the other hand, theradon emanation rate from backfill tailings corresponding to thesame radium content was found to be 2.04 Bq m−2 s−1, i.e.about 283 times higher than the ore. Franklin et al. (1982) alsoreported that in Canadian uranium mine the backfill materialemanates radon at a rate approximately 1,000 times greater thanthe exposed ore. This is mainly due to the increase in the totalsurface area offered for emanation (Garver and Baskaran 2004;Somlai et al. 2008; Sakoda et al. 2010) and the higher bulkporosity (Tanner 1980) of the tailings as compared to the ore.Apart from this, the atmospheric pressure and temperature alsoaffect the release of radon gas from the porous matrix (Iskandaret al. 2004; Lawrence 2005; Zhuo et al. 2008). When there is apressure drop in the mine environment, the radon emanationfrom the porous tailings is enhanced. Clements and Wilkning(1974) found that the radon emanation rate changes from 60 to80%with a pressure change of 1 to 2% in the pore space of thematerial. Washington and Rose (1990) reported that change intemperature has less effect on radon concentration in dry soilsthan in moist soils. This is due to desorption of radon fromsolids into the interstitial space. Therefore, bulk porosity of thematerials is the dominant factor that affects the rate of radon gasemanation from rock surfaces into the mine openings unless theore grade is high.

Conclusions

In this study, we investigated the radon emanation from the insitu ore body and backfill tailings in an underground, low-

grade uranium mine. The effects of different parameters suchas 226Ra content, moisture content, porosity and surface areaon the radon emanation rate from the ore body and backfilltailings were studied. It was found that the radon emanationrate is largely dependent on 226Ra content and porosity. Asignificant relationship between in situ radon emanation rateand 226Ra content was obtained. The empirical relationobtained through regression analysis may be used for theprediction of radon emanation rate from uranium ores ofsimilar nature. The radon emanation from backfill tailingsincreases with the moisture fraction up to 0.14, after which itgradually starts declining with moisture saturation due to thedramatic reduction of diffusion coefficient of radon in thesaturated tailings. The radon emanation rate from the backfilltailings was found to be 283 times higher than the ore for theequal 226Ra content due to higher bulk porosity and enhancedsurface area. Due to high emanation rate, the mill tailings usedas backfill material for stabilising worked out stopes maysignificantly increase radon concentration inside undergrounduranium mines.

Acknowledgments The authors wish to express their sincere thanks toMr. D. Acharya, Chairman andManaging Director, UraniumCorporationof Indian Ltd. for granting necessary permission to carry out the researchwork in Jaduguda uranium mine. Authors are also thankful to the admin-istration of Health Physics Unit, BARC, Jaduguda for extending all kindsof supports for carrying out the experiments.

References

Archibald JF, Nantel JH (1984) Prediction of radiation levels and venti-lation requirements in underground uranium mines. CIM Bull77(861):60–64

Bernhardt DE, Jones FB, Kaufmann RF (1975) Radon exhalation fromuranium mill tailings piles. Technical note ORP/LV/-75-7(A), USEnvironmental Protection Agency, Las Vegas, NV, 89114.

Bochiolo M, Verdoya M, Chiozzi P, Pasquale V (2012) Radiometricsurveying for the assessment of radiation dose and radon specificexhalation in underground environment. J Appl Geophys 83:100–106. doi:10.1016/j.jappgeo.2012.05.004

Bossew P (2003) The radon emanation power of building materials, soilsand rocks. Appl Radiat Isot 59:389–392

Clements WE, Wilkning MH (1974) Atmospheric pressure effects on222Rn transport across the earth-air interface. J Geophys Res 79:5025–5029. doi:10.1029/JC079i033p05025

Darby S, Hill D, Auvinen A, Barros-Dios JM, Baysson H, Bochicchio Fet al (2005) Radon in homes and risk of lung cancer: collaborativeanalysis of individual data from 13 European case–control studies.Br Med J 330:223–226

Dwaikat N, El-hasanM, SueyasuM,KadaW, Sato F, Kato Y, Saffarini G,Iida T (2010) A fast method for the determination of the efficiencycoefficient of bare CR-39 detector. Nucl InstrumMethods Phys ResB 268:3351–3355

Ferry C, Richon P, Beneito A, Robe MC (2001) Radon exhalation fromuranium mill tailings: experimental validation of a 1-D model. JEnviron Radioact 54:99–108

Franklin JC, Washington RA, Kerkering JC, Montone H, Regan R(1982) Radon emanation from stopes backfilled with cemented


http://dx.doi.org/10.1016/j.jappgeo.2012.05.004

http://dx.doi.org/10.1029/JC079i033p05025

uranium mill tailings. US Department of the Interior, Bureau ofMines, pp 1–6

Garver E, BaskaranM (2004) Effects of heating on the emanation rates ofradon- 222 from a suite of natural minerals. Appl Radiat Isot 61:1477–1485

Gulson BL, Mizon KJ, Dickson BL, Korsch MJ (2005) The effect ofexposure to employees from mining and milling operations in auranium mine on lead isotopes—a pilot studies. Sci Total Environ339:267–272

IAEA (1992) Measurement and calculation of radon releases from ura-nium mill tailings. Technical Report Series No-333.

ICRP (2010) Lung cancer risk from radon and progeny and statement onradon. ICRP Publication 115, Annals of ICRP, vol. 40 (1).

Iskandar D, Yamazawa H, Iida T (2004) Quantification of the dependen-cy of radon emanation power on soil temperature. Appl Radiat Isot60:971–973

Jha S, KhanAH,Mishra UC (2000) A study of the 222Rn flux from soil inthe U mineralised belt at Jaduguda. J Environ Radioact 49:157–169

Jha VN, Tripathi RM, Sethy NK, Sahoo SK, Shukla AK, Puranik VD(2010) Bioaccumulation of 226Ra by plants growing in fresh waterecosystem around the uranium industry at Jaduguda, India. JEnviron Radioact 101:717–722

Lawrence C (2005) Measurement of 222Rn exhalation rates and 210Pbdeposition rates in a tropical environment. PhD thesis, QueenslandUniversity of Technology.

Mayya YS (2004) Theory of radon exhalation into accumulators placed atthe soil atmosphere interface. Radiat Prot Dosim III 3:305–318

Meslinn PY, Adler PM, Sabroux JC (2010) Diffusive transport of gases inwet porous media. Soil Sci Soc Am J 74:1871–1885

Mudd GM (2008) Radon releases from Australian uranium mining andmilling projects: assessing the UNSCEAR approach. J EnvironRadioact 99:288–315

Panigrahi DC, Gupta R, Bhowmik SC (2005) Modelling of the ventila-tion system of a deep uranium mine. In: Gillies ADS (ed)Proceedings of 8th International Mine Ventilation Congress.Brisbane, Australia, pp 439–445

Raghavayya M (1976) A study of the distribution of radioactivity inuranium mines. University of Bombay, MSc thesis

Raghavayya M (1981) An inexpensive radon scintillation cell. HealthPhys 40:894–896

Raghavayya M (1990) Environmental radonmetry and emanometry.Workshop on Environmental Radioactivity, Kaiga

Raghavayya M, Khan AH (1973) Radon emanation from uranium milltailings used as backfill in mines. Noble gases, Op. cit., pp 269 –273.

Rogers VC, Nielson KK (1991) Multiphase radon generation and trans-port in porous materials. Health Phys 60:807–815

Saha SC (1972) Evaluation of different parameters of airborne dust and itsapplication in mining and milling of uranium. University ofBombay, MSc thesis

Sahoo BK, Mayya YS, Sapra BK, Gaware JJ, Banerjee KS, KushwahaHS (2010) Radon exhalation studies in an Indian uranium tailingspile. Radiat Measur 45:237–241

SakodaA, NishiyamaY, Hanamoto K, Ishimori Y, Yamamoto Y, KataokaT, Kawabe A, Yamaoka K (2010) Differences of natural radioactiv-ity and radon emanation fraction among constituent minerals of rockor soil. Appl Radiat Isot 68:1180–1184

Sarangi AK, Singh AS (2006) Vein type uranium mineralisation inJaduguda uranium deposit, Singhbhum, India. In: Proceedings12th Quadrennial IAGOD symposium, Moscow.

Somlai J, Jobbágy V, Somlai K, Kovács J, Neméth CS, Kovács T (2008)Connection between radon emanation and some structural proper-ties of coal-slag as building material. Radiat Meas 43:72–76

StrongK, Levins D (1982) Effect of moisture content on radon emanationfrom uranium ore and tailings. Health Phys 42:27–32

Tan K, Liu Z, Xia L, Lv J, Hu H (2012) The influence of fractal sizedistribution of covers on radon exhalation from uranium mill tail-ings. Radiat Measur 47:163–167

Tanner AB (1980) Radon migration in the ground: A supplementaryreview. In: Proceedings of Natural Radiation Environment III.Conf-780422, Houston TX, pp. 5–56.

Thompkins RW (1982) A manual of radon gas emission characteristicsand techniques for estimating ventilation air requirements. Radiationin uranium mines, Queen's University, Kingston, Ontario.

Washington JW, Rose AW (1990) Regional and temporal relations ofradon in soil gas to soil temperature and moisture. Geophys Res Lett17:829–832

Zhuo W, Guo Q, Chen B, Cheng G (2008) Estimating the amount anddistribution of radon flux density from the soil surface in China. JEnviron Radioact 99:1143–1148


Assessment of (222)Rn emanation from ore body and backfill tailings in low-grade underground uranium...

Documents

Transcript of Assessment of (222)Rn emanation from ore body and backfill tailings in low-grade underground uranium...