# Recommended Proceduresfor Measuring Radon Fluxesfrom Disposal SitesofResidual Radioactive Materials

ManuscriptCompleted: February 1983 DatePublished: March 1983

Prepared by J.A. Young,V. W.Thomas, P. 0.Jackson

PacificNorthwest Laboratory Richland,WA99352

Preparedfor Division ofWasteManagement OfficeofNuclearMaterialSafetyandSafeguards U.S. NuclearRegulatoryCommission Washington, D.C.20565 NRCFIN 82216 

### NUREG/CR-3166 PNL-4597ABSIP.P.CT

This report recornmenrls instrurr,entc.tion and metr,ods suitable for measuring radon fluxes t·manatinq h·om**co·n~red** d·isoosai sites of residual radioactive**matedal~.** such as urc.rdum mill**tan·in~rs.** Problems of spatial and temporal var·iahons 1n radon flux are discussed and the advantages and disadvantages of severa·l instriJments ar·e examin<:1L /\year-long measurement program and
·3. two rnonth**measurem(~fl~** rnethodoloq:; ore then oresented based on the inherent difficulties of measufii·:q avenqP r·c:.don**flu;~.** O'J8r**;:~cover** using the recorrrnenJed instrumer:t,J+_ion.

l.'TABLE OF CONTENTS

]. Introduction

•••••••••••••••••••• 0 • 0 • 0 • 0 • 0 • 0 •••••••••••••••••••• 1

II. Spatial and Temporal Variations in the Radon Flux .•.•.•.......................... 2

1. Spatial Variations

2. Temporal Variations



### A. Introduction



### B. Moisture Content ••••••••••• 0 0 0 0 ••••••••••••••• 0 •••••••••• 2

3

3

3

C. Ice

. . . . . . . . . . . . . . . . . . . .•

.•

.. . . . . . .•

.•

.. . . . . . . . . . . . .•

.•

.• 4

D. Pressure

E. Wind Speed

• 0 0 ••••••••• 0 • 0 •••••••••• 0 •••••••••••• 0 ••••••
F. Season

•••••••• 0 0 ••••• 0 • 0 •• 0 •••••••••••••••••••••• 0 0 0 ••• 

### G. Diurnal Variations

••••••• 0 • 0 •••••••••• 0 • 0 •••••••••• 0 0 ••
H. 

### Trends with Time

III. Radon Flux Measurement Techniques

•••••• 0 0 •••••••••• 0 ••••••• 0 • 0 • 1. Introduction

•• 0 0 0 ••••••••• 0 •••••••••• 0 •••• 0 •••••••••••••••• 2. The Charcoal Canister Method



# ............................... 3. The Flow Method



# ............................................ 4. The Accumulation Method



## .................................... 5. Track Etch® and Thermoluminescent 5

5

5

6

6

7

7

7

8
10

Dosimeter (TLD) Detectors .........•..•................. 11

IV. Procedures for Conducting Radon Flux Surveys

1. Summary of Recommended Procedures



## .......................... 2. Gamma-Ray Surveys



# .......................................... 3. Radon Flux Sampling Grid



# ................................... 4. Time Schedule ofFlux Measurements



## ......................... A. Year-Long Measurement Series



# ...........................

v 

### 12

12

13

13



### 14

14B. Two-"'lonth Measurement Series

........................" 17



## ,, '

. Ca"Iibriltlr;n of Radon Flux**r~eaSUl'ing** iJev**~**ces

Reference<:.

vi l.7

20J. A.**Young~** V. W. Thomas anG P. 0. Jackson

1. lntroductian

The U. S. Environmental ProtecUo11 Agency (EPA) inter·im environrner1tal stanaards for the dis;Josal of residual radioactiVE: materials from inactive uranium ;:>rocessing sites were publi"shed in the Fedc:··ai**Reg·i~,ter** in January 193) (tJ.O CFR.**192)~.** P,lthough the Department of F.:1ergy (DOE) has tt\e primary respons·ibility for the implementation of thesE: EPr1 st:J.?"IdiFds,**PL~-9S-604** requires that the**i~uclear** Regulatory Comfilissi,Jn**U~RC)** concur in remedial actions. One of the requirements of the**interi~l st~ndards**  is that disposal of r·esHua1 rad:Jactive materials from inactive uranium processing sites shall be conducted in away that provides areasonable fxpectation t'nat the average annual l'elease of radon-222 from the disposal sites to t.he**atmosp~1er0** by residuai radioactive materials fcd.lovJing -jispJSal will not exceed 2 pCi/mLsec for at ·!east 1000 years**fullm~·in~,** disposal. Howc.-.'er, the EPA h<lS recently proposed t1at the starHjad be changed to requ'1re that the flux shall not exceed 20 pCi/rn2·-sec fol" at least 200 yr::ars, dfld to the extent practlcable, 1000 Y<':!lil'S.**r~~** lS fC:JI.pectJ:d that the radon flux standard will be interpreted to reqJir'e**t~1at** t'Je a.nnual avc;ragt: flux from a tailhgs pile, rathe·r tha:1 t.re f·r,lx ;lt any location

on the pile, snalI nc·t ex,:eed the st::..ndard.

It is anticipated ·that the reduction Jf rcH;or. E!iTJiss·;c;ns from disposa1**sitt~s** will be accr;mp1ishec! by covering the taiL:-.qs vlith a layer, or layers, of earthen material. Hm1ever·, it is**pos~ibie** that a layer crF materia·! such as asphalt will also be laid down w act as a radon b.J.rrier·, The cover will decrease the em·ission of radon into the atmosphere because of the rall"ioactive aecay sf the radon during its**difFu:~·(cn** through t.he cov,;r. Tht; radr)n**emiss~on** will also be decreased because the cover**w~**ll reduce**t~12** concEntration gradier1t and**therefo~e** the rate af**diff~sion** of radon fl-.:Jnl the**ta'r1ing-~;.**
The ra.don f1ux T'r·om a.**co·vl~red** ta1·1ings piie \vi11 cor.:e from both th2 tai1ings JJ"l'j t.hE· covering mater-iai. The radon emission standard w"ill r;e**consid~1·e~** to**b~ sati~fien**  for a disposal site**,~** the radon flux is less than 1)r eqi1il.i to the**~::andat'd p~us** **th~~** exhalation rate of the cover fl"ID.tl'ria';. r'•ut:es f'·onl natural**soli~:** ere**ty~lica11y** 0.5 to 1pCi/rn2-sec, nut**f1~.;xes** up to**sr:ve~'a.l** tlrr1es thest: values ai--r; ;·J,.,t : . mustEl.·l. Therefore, the radon fluxes from possiblE: cover· n;,YJ:e(ie:ls at F:Ci"'1 disposai site :,•wuld be determiqed as paft of the**di~[E·""~l ~,·:,,;·.**  Tile f"ind·!**~-Pi\ ~;t..:;..,clard** **cor:cc,~.1**ing radon f"luJ:(:; :e.-_'1 t••.: ':: L11: form .)f either d perforwance standard or a design objective. 

### A)trT0rlndnce stanoatd l·iould require that radon f1Jx**rneasur?rnPnt:~** tle perL·l''IIC!:i t'.J v-2r

..**1f~J** compliance. 1\ desi:_;r1**obj~:ctive** wo,1ld r""Cil.•-;t'f. c;nly tha.t U:c covtJ

1be designed to lower the calculated radon flux below agiven value. Flux measurements would not be required to verifycompliance with a design objective. However, radon flux measurements would still be useful for the experimental purpose of verifying that the design cover is functioning as planned.

This report has been prepared for NRC to recommend procedures for measuring radon fluxes from disposal sites of residual radioactive material after theyhave been covered to reduce the radon flux. It will recommend sampling programs, instrumentation, analytical procedures, data reporting formats, and statistical analysis of the data that should be used in the determination of radon fluxes.

II. Spatial and Temporal Variations in the Radon Flux

1. Spatial Variations

The determination of average radon fluxes from disposal sites is complicated by the fact that theremay be large spatial and temporal variations in the flux from agiven disposal site. The flux from atailings pile varieswith location on the pilebecause of variations in thickness of the pile and variations in the particle size, 226Ra concentration, moisture content, and emanating power of the material added to the pile (the emanating power is the fraction of the radon atoms produced by 226Ra that escapes the crystal lattice and is free to diffuse). Measured radon fluxes have varied by
more than an order ofmagnitude with location on tailings piles (Silker and Heasler, 1979; Ford, Bacon and Davis Utah Inc., 1981). According to Leggett, et al. (1978), the number of locations at which aparameter must be measured to determine its average value with aprecision of 25% at the 95% confidence level is given by

Number**~** 45(coefficient of variation) 2 ( l )
The coefficientof variation of the radon flux measurements made by Silker and Heasler (1979) at several locations on the Grants, New Mexico tailings pilewas 0.74. Freeman (1981) found that the coefficient of variation with location was 0.84 for the Grand Junction tailings pile. The coefficients of variation of the radon flux measurements made by Ford, Bacon and Davis Utah Inc. (1981) also averaged 0.84for several uncovered tailings piles. According to Equation (1), the number of locations at which the flux would have to be measured to determine the average within 25% at the 95% confidence level would be 25 if the coefficient of variation were 0.74, and 32 if itwere 0.84.

The variation of the radon flux across acovered tailings pile could be somewhat less than that across an uncovered pile because horizontal diffusion of radon in the cover material would be expected

2to lower horizontal concentration gradients. However, if the cover material were not uniform, or ifcracks developed in it, the spatial variation ofthe flux from acovered tailings pile could be greater. The coefficientof variation of the radon flux measurements made by Ford, Bacon and Davis Inc. (19Bl) averaged 0.66 for several tailings piles covered by about six inches of soil. According to Equation (1), measurements at only 20 locations would be required for this coefficientof variation. However, Leggett, et al. (1978) also recommends thatmeasurements be made at aminimum of 30 locations. It therefore appears that in most cases flux measurements should be made at 30 locations, although in some cases measurements ofmore locations would be required because of higher variations in the radon flux.

2. Temporal Variations

A. Introduction

The radon flux from agiven location at adisposal site will also show considerable variation with time as aresult of changes in meteorological conditions, moisture content of the tailings, and perhaps settlingofthe cover material. According to Baver (1956), the meteorological factors influencing the radon flux are, in order of decreasing importance, rainfall, variations in barometric pressure, variation of soil and atmospheric temperature, and wind speed. He estimated that together these factors are responsiblefor less than 10%ofnormal soil aereation.

B. Moisture Content

The radon flux will depend greatlyupon the moisture content ofthe tailings and cover material. The fraction of radon atoms produced by 226Ra decay that escape the crystal lattice increases with moisture content. When a 226Ra atom decays by alpha particleemission the radon atom that is formed recoils in adirection opposite from that taken by the alpha particle. If the recoiling atom comes torest inside agrain of the material, it is very likelyto remain entrapped, but if it
comes to rest in apore itwill be free to diffuse into the atmosphere. However, the pores of compacted natural materials
are likelytobe smaller than the recoil range ofradon atoms in agas, so arecoiling atom that enters agas-filled pore is very likelyto cross the pore and become entrapped in aneighboring grain (Tanner, 1980). The recoil range in water is about
one hundred times less than that in air, so the probability that arecoiling atomwill stop in a pore is greatlyenhanced if the pore is water-filled.

3The rate of diffusion ir: ,,·utei' is rr.:ucl: le5:;; t!.dn th.1t in air so the rate of diffusion into the <J.t.n::.;·.srl-]ere of the. radon atoms that have escaped tn2 uystctl lattice .vll"i be lower-ed by increasing the moisture ccr:te:n. of e1thE.r thl:.' tJilings cr**th·~** cover material. Therefc.re, inuec\se::l moistur·e content could either· raise or lower the ;ad,Jr Fiu:<. .!\cco"'c.ling to**~1om~ni~** .c:t al. {1979), the radon flu:( f·:·orr: dornf'·;-:;ic utcrdum ore.s v;::,r·i2s only slightly with rnoistur·e c-nL-::Tr**b:;t.,t~~t~n** lO% and 81,;% s;;t;;- ration. On the other hand, \\oqv';, et. ,,·1. (1979) -round that the flux from tailings decreJsed 11y i1**~--i:l.ct,_H'** of 100 when**tb~** moisture content increased from dry to saturatitJn. The ?PPM'f'nt contradiction of these teS'J:t') is exp1ain-c:c! b_y th: nbser-

..at.-ions of Strong and Levins (1982}, wno 1r03sureJ**l~e** f1ux**a~** radon from a column of mill taflillClS**as~** LJn(tion of moisture CtJrit.enl.-, They found that the fl1•x lnCrt:aS·2d by c.**~act,)r** of 3.5 wilcn the moistut'e c0ntent increased f:or.·, 1 J.2 to 5.7% hy ',·;e-19ht r:.**t.~u::~** increased only s10w:.Y ·H·iti, in::r·e.a·;**:l'l~; rnn·is~~·.:re**  ccntent unt-il saturation was**reache~**.. ot**·,..,~\lich t-i-~1::'** **~-:~** dccru·;eG sharp-!:y. They estimated that tf-!e r·a.Jnn flux f;'.:X·' an infinit2ly**th~ck** tailings pile :hat was**s~t~rdted ~itn** **:._,~~r ~st:l~**  l>e**1nl~ ~~**  0f that from a one**contain-~r:''l** 5.7%**··<~-:.t::·,·.** According to**Mc~eni,** et**~:.** (1Q7?],**-f~~~~.:r~** content of 0.2% is typic<1l for dry**Li:·;r,~s** ir; a :

.. Y'th,;>:st:.:.r'n**~lirnat2.** Increasing the moisture**1:Jnt~~~ ~t** **~~~~e ~2il** **i~gs w~uld**  tc**(~X·** pected to incr9ase the flux. 1-IO"'iitv'ei) n th<; tai'lin9s**,~-~~rc~** covered by a ;a._yt;r of**eor-til~n** rn3.teria.·1, i**ncr~ac; in~** **th!~** n;<J,**s- ~utc**  content of the cover rr,ateriG.1 ,_._.:-_,,.;id dt::::n;3.52 the rate of 'jiffusion of radon throtl9h the cover" J::c! Lil!l'i' the f:ux.**~\** he:;vy rainfall**mig~1t** not**immediat~~Y** it.crease**th~** moisture**contetl~** cr the tailings, but it would**i~cre5S2** the mo1stute content of**th~** cover material, thereby greatly**decr~as1ng** the**ra~on** fllil. Therefore, flux mf.:a:;vre111ents**mac::~ f·~'** **hw~**n,J ct 1-'.ea\'Y n.jn sh:)u**~**d not be used t0 .jr·t,=rmine avE-rage**f\:::~:s.** C. Ice

Several investigator5 have dlss**ot~t-r-v2n tn~t**  a**cav~r** :1f ice will sharply reduce the radDn fl'ix**-(r-~>rl** ,·;rlJst.al sur·f.K25, Pearson a.'ld Jones (1965, 1966)**o:;s\:rv,~d** t:"-etl. the flux inc:-easc-d by a factor of two or more when a w:r.ter·**:f;c~w r~sulted**  ·ir, t!",e disappearance of iln ice coJer.**Count~~s** (lq77) observed ti,Bt

a 1000-fold reductior1 in the flt!X fror" J tQi1ings pile persisted for several weeks fcllmv·,'r1g the formt-i'_jr; ftf an ·i.-:-t.· cover on the plle.**Therefov--~,** the**aw~·:cqr;** i··:>·**f-~_..,,** •J ,._,;_iJ',ngs ;:;i> should not be deterrr·inecl by f 1dx**"'·C\3.',.~r-:•!H!1.S :1·:d·~** **wh"'~~** ,;hr: pile is coverecl with**~ct.**D. Pressure Decreasing atmospheric pressure draws interstitial gas toward the surface. thereby increasing the radon flux; and increasing pressure pumps it away from the surface, thereby decreasing the flux. According to Clements and Wilkening (1974) atmospheric pressure changes of 1% or less cause 50 to 100% changes in the exhalation rate of soil, with the actual change depending upon the rate of change of the pressure and the duration ofthe change. Afrequently quoted figure is that a 1% atmospheric pressure change will cause approximately a60% change in the radon flux (Colle, et al., 1981). Bogoslovskaya, et al. (1932) found that the flux from uranium ore would vary by an order ofmagnitude with atmospheric pressure, even if the ore were buried five meters below the surface.

E. Wind Speed

It is not known for certain how significant arole wind speed plays in determining radon fluxes. The uncertainty is partlydue to the fact that radon flux measuring devices interrupt the flow of air across the material whose flux is being measured. Therefore, it is not possible to be certain that the flux from the material is the same as it 'Nould be if the flux measuring device were not there. Pearson and Jones (1966) found
no obvious correlationbetween wind speed and the radon flux from grass-covered soil in Illinois at the very low wind speeds that normally occurred near the scil surface. However, at abnormally high wind velocities the flux increased linearly with velocity. Kraner, et al. (1964) measured higher fluxes on unstable days with higher wind speeds. They postulated that the increase occurred because the microoscillations in barometric pressure that are associated with wind gave rise to turbulent pumping that resulted in the exchange of a layer of soil gas with radon free air from above the surface. Israel and Harbert (1970) measured about afour-fold increase in the radon flux from soil when the wind speed increased from 1to 13 msec-1. However, their measurements were performed on moist soil, and they concluded that the increase in the flux was due to adecrease in the soil moisture content at higher wind speeds. Because of the possibilitythat radon fluxes increase with increasingwind speed, fluxes should not be measured during high winds.

F. Season

The radon flux can be expected to show seasonal variations at locations that show seasonal variations in factors such as soil moisture or ice cover. Megumi and Mamuro (1973), however, found little seasonal variation at Osaka

.. Bakulin (1969) found

5that the seasonal variations were not more than 10%, with maximums occurring in summer. Because of the possibilityof systematic seasonal variations, the radon flux should be measured at uniform intervals throughout the course of ayear in order to obtain areliable value for the average flux.

G. Diurnal Variations

The radon flux may be expected to show diurnal variations because of (1) the diurnal pressure wave, which produces aminimum in the pressure in the afternoon; (2) turbulent mixing in the atmosphere which leads to an increase in the flux during the day; and (3) changes in convective flow due to temperature differences in the soil between day and night. Pearson and Jones (1966) found that the flux from soil in Illinois was highest near sunrise and in themid-afternoon when the atmosphere
was most turbulent near the soil surface. The maximum (hourly) radon fluxes during the day were around seven times the fluxes measured during the stable nighttime. Duwe (1976) concluded 'f"rom a study of the measurements by seve11 investigators that the most likely pattern of radDn flux is abroad nighttimeminimum, an increase during themorning to an average value of about 2.5 times theminimum, adecrease during the early afternoon, and a second increase during the late afternoon to an average value of about 1.5 times the minimum. Duwe also concluded from model calculations that soils with low permeabilitywould show lower diurnal flux variations. Because of the likelihood of diurnal**variation~** in the radon flux, radon flux measurements should, if possible, be made over time periods that are multiples of 24 hours.

H. Trends with Time

Radon fluxes from stabilized tailings piles could show systematic trends with time because of factors such as (1) changes in the moisture content of the tailings and cover material. (2) development offissures in the cover, (3) erosion, (4) the action of burrowing animals, and (5) the growth of vegetation. Changes in the moisture content would be particularly likelyto
cause significant trends. If the cover material were sprinkled with water during its addition, the radon flux might be expected to increase rapidlywith time at first, and then change more slowly after that as equilibriummoisture content was approached. This author is not aware of any available data that could be used to determine the time period required for moisture content and radon fluxes to approach equilibrium leve1s. The time required would depend upon the climate and the nature of the cover material. Therefore, radon flux measurements at afew locations on at least two tailings piles should be made at least once amonth for about ayear-to determine the time that should be allowed

6for the fluxes to approach equilibrium values before extensive measurements to determine the average flux are initiated. After the fluxes have approached equilibrium values on these two piles, the flux measurements should be continued on aonce ayear sampling schedule for as long as possible to determine the nature of any long-term trends.

III. Radon Flux Measurement Techniques

1. Introduction
Several investigators have used various types of accumulators
or charcoal canisters to measure radon fluxes. However, at the present time there existsno facility that can be used to accuratelycalibrate these flux measuring devices under varying meteorological conditions. The flux is generally calculated by dividing the total quantityof radon collected in the device by the area covered by the device and by the sampling time. Therefore, it is not really possible at the present time to compare the accuracies with which the various devices
measure the radon flux.

2. The Charcoal Canister Method

Several investigators have employed various types ofpassive charcoal canisters to measure the radon flux. The canister containing charcoal is placed directly in contact with the surface. The charcoal adsorbs the emanating radon, and after aperiod of time ranging from afew hours to afew days the charcoal is removed and the average flux determined from the quantityof radon adsorbed on the charcoal. The radon is usuallymeasured by sealing the charcoal in an air tight container, allowing the charcoal to sitfor afew hours to allow the short-lived radon daughters to come to equilibrium with the radon, and countingthe gamma-rays emitted by the shortlived radon daughter,**21 ~Bi,**  using either aNai(Tl) or agermanium diode gamma-ray spectrometer. However, the radon can also be desorbed from the the charcoal and counted in aZnS scintillation detector cell. The charcoal canistermethod has the advantage that manymeasurements can be made inexpensively because of the low cost of the canisters and the ease with which theycan be deployed and recovered.

Countess (1977) has used amodified U.S. Army Mll gas mask charcoal canisterto measure radon fluxes. This canister covers an area of 87 cm2 and contains 148 gof activated charcoal. Countess (1977) reports that a lower limit ofdetection of 0.03 pCi/m2-sec can be obtained for afour-day exposure using this canister. This detection limit should be more than adequate for determining whether the flux is greater than 2pCi/m2-sec. Mine SafetyAppliance Co. manufactures an activated charcoal cartridge type GMA No. 459315 that is suitable for measuring radon fluxes. It will cover an area

7of 41 cm2 and contains 36 gof charcoal (Countess, 1977). It is also quite easy to construct charcoal canisters using PVC pipe or similarmaterial.
MacBeth, et al. (1978) reported that the prec1s1on and accuracy of the charcoal canistermethod is ±15%. This figure may be optimistic, however, because atwo-laboratorycomparison study performed to determine whether the actual analysis of the charcoal canister is a major contributor to variations in measured fluxes found that the average difference in the measurements between the two laboratories
was 16% (Horton, 1979). However, with careful counter calibration it should be possible to measure the radon with aconsiderably better precision than this.

Charcoal canisters have the drawback that they can on'ly be used tomeasure the flux over avery limited area for alimited period of time. Therefore, they should be used to measure the flux at several locations and at several times at each location to determine the average radon flux. Magum1 and Mamuro (1972) increased the measurement area to 2,450 cm2 by spreading the charcoal over anetting laid on the ground. The charcca1**~tJas** isolated from the atmosphere by covering 1twitr1 P'JC film. l<isleleski, et al. (1980) increased the area measured by attaching an army gas mask canister to the center of a collector lid covering an area of 2,300 cm2• However, the diffusion of the radon under the collector lid to the charcoal canistermay be too slow to prevent the radon concentration under the lid from rising to the level at which it lowers the net radon flux from the emanating surface, so this method could give results that are too**lo~;;.** Therefore) it should not be used to measure radon fluxes until it can be proved to provide accuratemeasurements. Any time the charcoal canister method is used, care should be taken to minimize the distance between the charcoal and the emanating surface to prevent the radon concentration from building up above the emanating surface.

3. The Flow Method

Several investigators have measured the average radon flux over arelatively large area by circulating the air under acollector through a**charco~l** bed. Pacific Northwest Laboratory (PNL) developed
arecirculating, pressure balanced, flow-tllrough radon flux measuring system that uses a76 X122 X 5r:m (9300 cm2 area) aluminum tent to
cover the areato be measured (Thomas, et al., 1982; Fr-eeman, 1981). Adiaphragm vacuum pump draws air through adrierite column to remove water vapor, through afilter to remove particulates, and then through
an activated carbon trap to remove radon. The carbon trap consists of a4.8 em diameter convoluted tube that is filled with 400g of Pittsburgh Carbon Company 8-12 mesh activated carbon. This trap has

8been shown to absorb 99.9% of the radon in air that is circulating through the trap at a rate of 2 liters per minute at atemperature of44°C (Hartley, et al., 1981). This sytem is sealed to tailings by pushing the lip of the tent into the tailings. It is sealed to asphalt by means of caulking compound. After about four hours of sampling, the charcoal is transferred to apetri dish and counted after afew hours delay for 214Bi using either aNai(Tl) or an intrinsic germanium gamma-ray spectrometer to obtain the radon concentration.

The coefficient of variation of the radon flux across the area covered by the PNL flux measuring system is expected to be much less than the coefficient of variation between the fluxes at widely separated locations on the tailings pile. Freeman (1981) found that the coefficient of variation of the fluxes measured at different locations on the Grand Junction tailings pile using the PNL system was 0.84. This is much larger than the coefficient of variation of 0.29 that Silker and Heasler (1981) measured between four locations within
an area of 200 crn2 using a41 cm2 area charcoal canister. Countess (1977) found an even smallercoefficient of variation between multiple measurements ofradon flux over aone to two square meter area on several test surfaces. He found that the coefficientof variation ranged from 0.06 for an outdoor location in the phosphate region of Florida to0.15 for measurements on soil in New Jersey. The variation in the flux across acovered tailings p"ile will be dependent upon the degree of heterogeneityof the tailings and cover material. However, if it is assumed that the coefficient of variation of the flux (as measured by acharcoal canister) across the PNL systemwill be 0.29, and the coefficientof variation in the flux (as measured bythe PNL system) across the entiretailings pilewill be 0.84, then it can be calculated that using acharcoal canisterrather than the PNL system will only increase the coefficient of variation of the measured fluxes from 0.84 to {0.842 +**0.29 )~** 

### =0.89. According to Equation (1), this would only increase from 32 to 36 the number of locations at which itwas necessary to measure the flux in order to determine the average flux with a25% accuracy at the 95% confidence level. It therefore appears that the averageflux over a large
area could be determined just as accuratelywith acharcoal canister
as with the PNL system, although afew more measurements might be required. It should be remembered also that acharcoal canister can be used to measure the radon flux over a longer time period than
can the flow system, so asinglemeasurement using acharcoal canister would probably provide abetterestimate of the temporal average than would a singlemeasurement using aflow system. In summary, comparisons between acharcoal canister system ard aflow system indicatethat charcoal canisters are more effect·ive in terms of cost and effort for measuring the average :aden flux across a large area such as a**rec~aimed** disposal site. However, the accuracies of the two**techniqu~s** must still be compared using acalibration facility**befon~** achoice can be made between them.

94. The Accumulation Method

The accumulation method involves the measurement of the radon that accumulates in an open-faced container that is inverted and sealed to the emanating surface. The accumulator is generally sealed to asoil surface using wet bentonite or by imbedding the rim of the accumulator several centimeters into the soil. The accumulator is sealed torigidsurfaces such as bui1ding materials using epoxy resins
or other caulking agents. Accumulators ofmany sizes and shapes have been used, with large barrel accumulators being popular.

The radon flux is determined by measuring the initial rate of change in the radon concentrations in samples of air that arewithdrawn periodicallyfrom the accumulator through asampling port. The air in the accumulator is generallymixed with a small fan to insure thatrepresentative samples are obtained. The flux is calculated using the equationE

## ~*(~~+An) (Z)

where E**~** radon flux (atoms/cm2-sec) 

## v**~** volume of accumulator (em') A**~** surface area of accumulator (em')
n**~** radon concentration (atoms/em') t**~** time (sec) A =radon decay constant (sec-1)

The rate of change in the radon concentration in the accumulator
can be used to calculatethe radon flux only until such time as the concentrationreaches a level that is asignificant fraction of the concentration in the emanating material. At that time back diffusion into the emanating material will decrease the concentration gradient in the emanating material and thereby lower the net flux into the accumulator. Wilkening, 

### et al. (1972) recommends that the concentration in the accumulator be kept below 10% of the soil gas concentration at adepth of 13 em. For most soils this concentration is reached in amatter ofhours.

Errors may arise in the measurement ofradon fluxes using accumulators because oferrors in the measurement of the quantityof r'adon in the accumulator, and because the accumulator (1) changes the flux by disturbing the soil, (2) changes the soil temperature, which may change the thermal stabilityor the amount of radon adsorbed onto soil grains, (3) reduces the flux because 0f increased radon concentrations inside the accumulator and (4) changes the temperature, wind velocity, and turbulence above the soil surface (Duwe, 1976). However, the same difficulties are faced by the charcoal canister and flow methods.

10Wilkening (1977) reported that typical error limits for the accumulation method are 6 to 10%. Bernhardt, et al. (1975) performed the most extensive evaluation and verification of the accumulation method. They found that although the counting errors were generally less than 5%for each radon sample, the precision for replicateflux measurements was typically20% for**fluxe~** of 100 pCi/m2-sec and 50 to 100%for fluxes of less than 10 pCi/m -sec.
The accumulator has the advantage that it can be used tomeasure the radon flux over a larger area than is generallymeasured using a charcoal canister. However, sampling time is limited because of the build-up of radon in the accumulator. The accumulator is amuch
more complicated and expensive device than acharcoal canister, and themeasurement of radon is more complicated using the accumulator. It also appears that the precision of accumulator measurements at low radon fluxes is not very good. These factors would seem to indicate that the accumulator method would be aless satisfactorymethod for conducting radon flux surveys than is the charcoal canistermethod. However, the accumulator method could still be themethod of choice if it could be shown to provide more accurate flux measurements than other techniques.

5. l!:.<!C2t..£!:ch"' and Thermoluminescent**Do~i_me-t:_er** (TLD) Detectors

Radon fluxes show large temporal variations, so average annual fluxes should be determined from several measurements during the
course of ayear if ameasurement technique is used that is not capa- bleofmaking ameasurement over aperiod of longer than afew days. Therefore, itmight seemmore practical to measure the radon flux using aTrack Etch"' or TLD detector which was buried beneath the soi1surface, or attachedto the surface of amaterial such as asphalt
or concrete, and left in place for ayear or more. Extensive measurements of soil gas concentrations have been made using these devices by many investigators, especiallyduring the exploration for uranium deposits. However, the Track Etch® and TLD detectors measure the radon concentration rather than the flux. Therefore, the radon concentrations would have to be measured at several depths and the effective diffusion coefficientdetermined before fluxes could be calculated from these concentration measurements. Alternatively, it might be possible to derive approximate empirical factors relating singledepth radon concentrations to radon fluxes from simultaneous measurements of concentration and flux for var·ious materials. Wilkening, et al. (1972) found that there was agood correlation between radon flux and soil gas concentration near Socorro, New H'exico. However, the derived factors m·ight be expected to be differ·ent for different mat.eria 1s, and might be expected to change with meteorological conditions and soil moisture. Therefore, it appears that the measurement of radon fluxes using Track Etch"'or TLD detectors would not be practical until extensive simultaneous measurements of concentrations and fluxes had been made to derive empirical factors relating cJncentrations to fluxes for various materials and conditions.

11IV. Procedures for Conducting Radon Flux Surveys

1. Summary of Recommended Procedures

Agamma-ray survey should be performed using adetector system such as amicro-R-meter to measure the gamma-ray exposure rates at
an elevation of 80 to 140 em at the grid points of 350 by 350 em grid. If an increase in the exposure rate is detected at any location, a search around that location should be made at the surface for elevated contact readings. Radon fluxes should be measured at locations showing exposure rates greater than three standard deviations above the average for the tailings pile. Flux measurements should alsobe made at enough locations on arectangular grid to bring the total number ofmeasurements up to the number required by Equation {1) or to 30, whichever is greater.
Each flux measurement should be made over as long aperiod of time as is practical, preferablytwo or three days. The measurements should not be made after aheavy rain, when there is an ice cover, or during high winds. If the cover material has been sprinkled wlth water during application, then flux measurements should not be begun until the covered tailingspilehas dried out enough so that the radon fluxes have stopped increasing rapidlywith time. Repeated measurements at afew locations on at leasttwo of the first piles measured should be used to estimate how long atime should be waited. Ideally, the flux measurements should be made every other month over the course of at least one year. However, if the flux measurements
are being made to determine whether the flux exceeds aperformance standard, itmay be necessary to complete the measurements within a shorterperiod of time, so that adecision can be made as towhether further remedial action is required. In that case, flux measurements should be made once aweek for two months at each location.

If themeasurements are being made to determ1ne whether the average flux exceeds aperformance standard, they should be discontinued whenever it becomes possible to be reasonably certain whether
or not the average flux will exceed the standard. The measurements should be discontinued if at any time it is calculatedthat there is either aless than 5% probabilitythat the average net flux will be greater than the existingflux standard, or agreater than 95% probability that the average net flux wi11 exceed the standard (net flux equals total flux minus the flux from the cover material). After themeasurements have been completed, the average and the coefficient of variation of the measured fluxes should be used to calculate the probabilitythat the true average flux exceeds the standard.

On the other hand, if the flux measurements dre being made to determine whether the cover is performing as designed, fluxes from at least afew tailings piles should be measured every other month for at least one year, because the fluxes could change systematically

12with time as aresult of factors such as changes in soil moisture, erosion, settlingof the cover material, growth of vegetation, and the action ofburrowing animals. After the first year themeasurements should be made once ayear until it is certain that there are no significant long-term trends in the radon fluxes.

2. Gamma-Ray Surveys Considerably elevated radon fluxes could occur at isolated locations on acovered tailings pile because of (1) fissures in the material used to stabilize the tailings pile, (2) elevated exhalation rates from the underlying tailings material, or (3) variations in the thickness of the stabilizingmaterial. Elevated gamma-ray exposure rates could occur at these locations because of the emission of gamma-rays from radon daughters that would deposit on the cover material. It is quite 1ikely that at least some of these "hot spots" would be missed during aradon flux survey consisting of measurements at 30 or so locations. Therefore, itwould be desirable to determine the locations of these hot spots, and tomake flux measurements at these locations.

For the above reasons, gamma-ray surveys should be conducted before radon flux measurements aremade. The measurements should be made using micro-R-meters at an elevation of about 80 to 140 em at the grid points of about a 3.5 X3.5mgrid (Young, et al, 1982). This is aconsiderablydenser grid than is likelyto be used for the radon flux measurements. If an increase in the gamma-ray exposure rate is detected at any location, acareful search should be made at the surface around that location for elevated contact exposure rates. The average exposure rate and the coefficient of variation of the exposure rates should then be calculated from themeasurements at the grid points. Radon flux measurements should be made at locations showing exposure rates greater than three standard deviations above the average.

Itmay be that the garrrna-ray surveys will detect no signif·icant hot spots. If this is found to be the case for the first few tailings piles measured, then the gamma-ray surveys may be discontinued for subsequent piles.

3. Radon Flux Sampling Grid According to Leggett, et al. (1978), aparameter should be measured at 30 locations, or at anumber of locations equal to 45 times the square of the coefficient of variation of themeasurements between the sampling locations, whichever is greater. Therefore, in addition to the flux measurements made at locations of elevated gammaray exposure rates, measurements should be made at enough grid points
on arectangular grid to bring the total number ofmeasurements up to at least 30. The coefficient of variation of themeasurements

13should then be calculatedto determine from Equation (1) whether additional measurements should be made. If additional measurements
are required, they should be made at locations where the original measurements have indicated that elevated radon fluxes might be present. Itmay turn out to be cost-effective tomake more than 30 flux measurements initiallyto insure that it does not turn out to be necessary to go back later to make additional measurements.

4. Time Schedule of Flux Measurements

A. Year-Long Measurement Series

The radon flux at any location will fluctuate with time as aresult ofmeteorological conditions and the moisture content of the emanating material. Since the fluctuations could have a seasonal component, radon fluxes should be measured every other month throughout at least ayear to obtain the annual average. Ifthemeasurements are being conducted to determine whether the cover is performing as designed, then measurements should be made once ayear after the first year or so until it appears certain that the flux is not changing significantlywith time.

Each flux measurement should be made over as long atime period as is practical for the measurement techniques being used. If charcoal canisters are used, each measurement should be made over aperiod of at least one, and preferablytwo or three days because of the possibilityof diurnal and other shortterm variations. It is not practical to sample overmuch longer time periods than this because radon has only a 3.8 day halflife, so the radon originallycollected would mostly decay away beforemeasurement if longer sampling periods were used. Also, the saturation of the charcoal by moisture and radon during longer sampling periods might lower the adsorption efficiency of the charcoal. The adsorption efficiency of the charcoal canister system used should be determined as afunction of sampling time by making side-by-sidemeasurements on homogene-·
ous tailings material whose moisture content and radon flux is higher than would be expected for the actual covered tailings piles that are to be measured. The measured radon fluxes for given time periods should then be compared with fluxes measured simultaneously over shortertime periods to determine how long
atime it takes for the collection efficiencyto begin to decrease. The measurement periods for tailings piles should be kept short compared to this time.

Radon fluxes will be measured during only a small fraction of the total time even with an ambitious measurement program, so themeasurements should not be made at times when it is expected**~hat** the fluxes will depart considerablyfrom average values. lherefore, measurements should not be made following a

14heavy rain, when there is ice cover. or during high winds. It is also likelythat flux measurements should not be made for a period of time following the completion of the stabilization of the tailings pile. It is probable that the cover material will be sprinkledwith water following its placement on the tailings pile so that itcan be packed down more readily. Ifthis is done, the radon flux should remain below normal until the cover and tailings material dry out enough to approach equilibrium moisture conditions. Therefore, flux measurements should be made at intervals at agiven location on the tailings pile to determine when fluxes appear to stop changing systematically with time. At that time extensive measurements to determine the average flux at agiven location from the covered pilemay be begun. Aftermeasurements have been made on acouple of piles itmay be possible to estimate the time it takes fluxes to approach representative values, so that flux measurements may be begun following this delay period on subsequent piles. However, the time required for the cover material to approach equilibriummoisture content could vary greatlywith the nature of the cover material and climatic cond"itions.

The number of measur-ements that would be required to determine the average flux at agiven locdtion with aprecision of 25% at the 95% confidence level is given by Equation (1). There have been some repeated measurements at given locations on tailings piles over extended periods of time. On the average, the measurements of Silker and Heasler (1979), Marple and Clements (l9l7), and Clements, et al. (1978) show a coefficient of variationwith time of 0.4. According to Equation (1), sixmeasurements would be required ifthemeasurements showed this coefficient of variation. The variation would be expected to be different at different locations, so the total number of measurements that would be required at any location would have to be determined from the coefficient of variation of the first few measurements at that location.

Itmay be that the radon fluxes from agiven tailings pile will e·ither be so low V1at itwill be clear after afew measurements that the net flux will be less than the radon flux stan-**dard~** or so high that itwill be clear that the average will be greater than the standard. Therefore, if the flux measurements
are being conducted to determine whether the average flux exceeds
aperformance standard, the average and coefficient of variation of the flux should be calculated at each sampling location after the second (and each subsequent) measurement, and then be used to calculate the average and thecoefficieflt of variation of the flux for the lotal oile. If it is calculated that there is either a less than 5% or agreater than 95% probabilitythat the average flux will exceed the standard, theflux measurements should be discontinued.

15After the flux measurements have been completed, the average and coefficientof variation of the measured fluxes should be calculated to determine the probabilitythat the true average flux exceeds the standard. If the average flux exceeds the standard, and the decision is made to add additional cover material to locations showing fluxes greater than the standard, then additional flux measurements should be made at these loca-· tions following the addition of thecover material. These measurements should be continued until the probabilitythat the average flux from the pilewill exceed the standard is calculated to be less than 5% or greater than 95%, or until the total number of measurements required by Equation (1) is completed.

It is possible that themeasurements over an extended period of time will indicate that there is acontinued change in the flux with time. In that case, if an extrapolation of the data indicates that net flux could change from less than to greater than the standard (or vice versa) in the future, periodic measurements should be continued, ifpossible, until it is possible to be reasonably certain whether the final average net flux will be greater than the standard.

The average flux calculated in the above manner will probably be somewhat higher than the true average because sampling locations have been selectedwhere elevated fluxes are expected. The coefficient of variation of the measurements might also be expected to be greater because of this selection of sampling locations, so the number of required sampling locations calculated from Equation (1) would be expected to be greater than would be the case ifmeasurements were made only at grid points. However, there are significantexperimental errors in themea-· surements, and the temporal variations of the radon flux will limit the accuracy of the calculated average fluxes. Therefore, the bias in the calculated average flux caused by the selection of sampling locations should be useful in decreasing the prob-· ability that the true average flux will be greater than the standard even though the measured average flux is 'less than the standard.

The possibilitydoes exist, however, that tailings piles will have alarge enough number of small areas of high radon flux (hot spots) to cause the average flux, calculated in the above manner, to exceed the true average flux by an unacceptable amount. Model calculations by Mayer and Zimmerman (1981) indicatethat a 1.5 em diameter hole that extends completely through
a 100 em thick cover will increase the average flux over a 150
cm2 area by afactor of about 30. Therefore, if a large number of hot spots are detected, the areas of these hot spots should be estimated. Each flux measurement, including themeasurements at the grid po;nts, should then be weighted according to the
area it represents when the average flux is calculated.

16B. Two-Month Measurement Series

It is possible that itwill be decided that the requirement of ayear-long flux measurement series would produce an unacceptable delay in the verification of compliance with aperformance standard. In that case, the flux measurements should be made
once aweek for two months, even though this shortened measurement schedule would probably result in adecrease in the accuracy of the determination of the average flux. The flux measurements should not be begun until the radon flux has approached equilibrium values. Repeated measurements at afew locations on at least two piles should be used to estimate how long towait. If the measured fluxes change systematicallywith time, itmay be necessaryto continue themeasurements, perhaps with lower frequency, until it can be predictedwith reasonable certainty whether the average flux will be greater than the standard.

V. Calibration of Radon Flux Measuring Devices

At the present time there exists no standard calibration facility that can be used to calibrate radon flux measuring devices. Such afacility is needed to determine whether these devices are providing accurate measurements of radon fluxes. The following paragraphs will describe the characteristics of afacility that cou-ld be constructed and used for calibratingradon flux measuring devices. It is based upon adesign proposed by Kearney and Kretz (1981).

The flux calibration facility should be constructed in an air-tight chamber having dimensions of at least 2x2x2 meters. Ahorizontal, perforated metal plate should be attached to the inside of the chamber about 30 em above the bottom of the chamber. The plate should extend completely
across the chamber. Asheet ofporous fabric should be laid on the plate and then covered by a layer of**s~nd** or other earthen material having low 226Ra content. Astandard NBS 2 6Ra source should be d·issolved in an acid solution and placed in abubbler in the air space underneath the layer of sand. Apump should be used to recirculate the air**undern~~th** the sand bed through the bubbler to transfer the radon produced by Ra decay into the airbeneath the sand**bed~ 26** **The** air should be bubbled through water before being bubbled through the Ra solution to prevent the 226Ra solution from evaporating away. After· leaving the bubbler the humidity of the air may be reduced by passing it through adessicant. Care must be taken to insure that the ·radon becomes well mixed in the space beneath the sand bed, but is not forced up through the bed.

The radon should diffuse up through the sand bed at aconstant rate to produce aconstant flux ofradon from the top of the bed. The radon emanating from the bed should be removed immediately to prevent radon concentrations from increasing above the bed and decreasing the radon flux. Therefore, the air above the bed should be circulated through a charcoal trap that is cooled with dry ice. The circulation system should

17be designed so that the speed of the air across the surface of the bed
can be varied and can be measured.

The radon flux will depend upon the strength of the 226Ra source and the fraction of the radon that decays before it diffuses through the bed. Different source strengths can be used to produce varying radon fluxes. The fraction of the radon that decays before passing through the bed can be calculated from the one-dimensional diffusion equation. It can be shown that for a 10 em thick layer of sand, more than 95% of the radon should pass through the sand before decaying.

The radon flux through the sand bed can also be determined by measuring the rate atwhich radon is collected in the charcoal trap through which the air above the bed is being circulated. The quantityofradon collected in the charcoal trap can be measured either by gamma-ray spec-- trometry or by heating the trap to desorb the charcoal into aZnS scintillation cell, and measuring the alpha particle emission rate with aphotomultiplier. The charcoal trap should be replaced periodically, and the radon concentration measured to determine whether the measured radon flux is constant. If it is not, the r·eason for the variationmust be discovered and eliminated.

The radon fluxes through the sand bed determined by the above two methods should agree within afew percent. Ifthey do not, then the
reason for the discrepancy should be determined before the chamber is used for calibrating the flux measuring devices.

It is important to insure that the radon flux through the sand bed does not vary with location on the bed, so caremust be taken to insure that the sand has aconstant thickness across the bed. The radon f1ux should be measured at several times and locations across the bed using charcoal cannisters to determine whether there is a spatial or temporal variation in the flux. If there is, the variation could, of course, be due to inaccuracies in themeasurements, but if there is no significant variation, then itcan be concluded that the flux is constant. If the measured flux does vary, the reason for the variation must be discovered before the chamber is used for calibratingflux measuring devices.

It could be that itwill not be possible to obtain sufficientlyconstantfluxes using the chamber described above. In that case, itmay be possible to obtain constant fluxes by placing layers of well-blended mixtures of sand and tailings on the floor of an air-tight chamber. The ratio of sand to tailings can be varied to give radon fluxes covering the range over whicn the flux measuring devices are expected to be used. The flux, and the temporal variation of the flux, can be measured by circulating the air above the tailings through acharcoal trap that is cooled with dry ice and measuring the rate atwhich radon is collected in the trap. The temporal and spatial variation in the flux from the bed would be determined by measuring the flux at different times and locations with charcoal cannisters. The objection to this method is that the radon flux could not be related to astandard source of radon.

18Once afacility has been constructed that will produce aconstant, known radon flux, it should be used to determine the rates at which the various radon flux measuring devices collect radon as afunction ofthe radon flux. The rate of collection should be given by

C = AF (3)

where

## c =rate ofradon collection (atoms/sec)

2 A =proportionalityconstant (em )

and F radon flux (atoms/em2 sec). = 

## .
It is expected that Awill approximately equal the area covered by the device. Each device should be used to measure the radon flux over a range of (1) radon flux, (2) air speed across the surface of the bed, {3) temperature and moisture content of the bed and the air, and (4) pressure to determine the magnitude of the variation ofA. If the variation is too great, then the device cannot be used to measure radon fluxes accurately. However, even ifAdoes not change with air speed in the calibration facility, it still may change with wind speed in the field because turbulencemay cause changes in the radon flux, and the turbulence spectrum of the atmosphere w'ill not be duplicated in the calibration faci1 ity.

19References

Baver, L. D., 1956. Soil Physics, 3rd ed. New York, John Wiley and Sons, pp 209-222. Bakulin, V. N., 1969. Dependance of Radon Exhalation and Its Concentration in the Soil on Meteorological Conditions (in Russian), Uch. Zap. Kirov. Gas. Pedagog. Inst., 30:70-79.
Bernhardt, D. E., F. B. Jones and R. F. Kaufmann, 1975. Radon Exhalation from Uranium Mill Tailings Piles: Description and Verification of the Measurement Method, U. 

## s·. Environmental Protection Agency, Technical Note ORP/LV-75-7(A). Bogoslovskaya, I. N., A. G. Grammakov, A. P. Kirkov and P. N. Tverskov, 1932. Report of the work of the Kavgolovo Experimental-Methodical Party in the Year 1931, Izu. Vses. Geol-Razved. Ob"yed 51:1283-1293. Caplan, P. E., 1972. Calibration of Air Sampling Instruments I -General Considerations and Flow Metering, in Air Sampling Instruments, American Conference of Governmental Industrial Hygienists, pp. H-1 to H-8.
Clemer1ts, W. E., S. Garr, and M. L. Marple, 1973. Uranium Mill Tailings Piles as Sources of Atmospheric Radon-222, Natural Radiation Environment III, pp 1559-1583.
Clements, W. E. and M. H. Wilkening, 1974. Atmospheric Pressure Effects
on 222Rn Transport Across the Earth-air Interface, Journal of Geophys;cal Research, 79:5025-5029.
Colle', R., R. J. Rubin, L. I. Khab, J. M. R. Hutchinson, 1981. Radon Transport Through and Exhalation from Building Materials, NBS Technical Note 1139.
Countess, R. J., 1977. Measurements of 222Rn Flux with Charcoal Canisters, Workshop on Methods for Measuring Radiation in and Around Uranium Mills, Albuquerque, New Mexico, pp. 139-147.
Duwe, M. F., 1976. The Diurnal Variation in Radon due to Atmospheric Pressure Change and Turbulence. ofWisconsin

- Madison. Flux from the Soil PhD Thesis, University

Ford, Bacon and Davis Utah, Inc., 1981. Engineering Assessment of Inactive Uranium Mill Tailings.
(a) Durango, Colorado, DOE/UMT 103, FBDU-360-06 (b) Shiprock, New Mexico, DOE/UMT 104, FBDU-360-02 (c) Grand Junction, Colorado, DOE/UMT 105, FBDU-360-09 (d) Riverton, Wyoming, DOE/UMT 106, FBDU-360-19

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Krarer, h.**~.,** C. W. Schraeder, ar1d R. D.**~vans,** 1964.**~rbsurrments** of tire**E'fL:Lt~** cf**,~ti1'0Spherlc** Variab'lcs on Radon-222 Flux :1nJ Sojl :-;a<; C('n--**rentr~t1ors. T~e**  Natt1ral Radl6tior**E1viron~Ent,** pp 1Yl-215.**[.f~\r:ett, i~.** **~~·.,H.** W.**[h~:kst:.n** and 

### r. !". HC.J'lt!Ofld, H7fL /•**S'ti'EI~-T,i(.(1.1 ~-·'.-_ct~~'dOl:JSJ;t**  fL'lr**Rttd-iolr:.~ical ~ur·vE:yirrq,**  ]At;\**~~ymposi~Hil** ur; _-\ch;:,'.<·,.,_.; in**:-:.-~~!·ioJ,**i(w Prct.r;cti')n**~tnr:itorinq, Jr-\Ei\·5i·~** ..2:_!Y/**:O~L**Macbeth, P. J., C. M. Jensen, V. C. Rogers and R. F. Overmeyer, 1978. Laboratory Research on Tailings StabilizationMethods and Their Effectiveness in Radiation Containment, Department of Energy report GJT-21. Marple, M. L. and Clements, 1977. Measurements of Radon-222 Flux from Inactive Uranium Mill Tailings Piles, ERDA Report LA-6898-PR, Los Alamos Scientific Laboratory, NTIS. Mayer, D. W. and D. A. Zimmerman, 1981. Radon Diffusion Through Uranium Mill Tailings and Cover Defects, NUREG/CR-2457, PNL-4063. Megumi, K. and T. Mamuro, 1972. AMethod for Measuring Radon and Thoren Exhalation from the Ground, Journal of Geophysical Research, 77:3052- 3056. Megumi, K. and T. Mamuro, 1973. Radon and Thoron Exhalation from the Ground, Journal of Geophysical Research, 78:3357-3360.
Momeni, M. H., W. E. Kisieleski, S. Tyler, A. Zielen, Y. C. Yuan, and J. Roberts, 1979. Radiological Impact of Uranium Tailings and Alternatives for their Management, presented at the Health Physics SocietyTwelfth Midyear Topical Symposium on Low Level Radioactive Waste Management, February ll, 1979.
Pearson, J. E. and G. E. Jones, 1965. Emanation of Radon-222 from Soils and its Use as aTracer, Journal of Geophysical Research, 70:5279-5290.
Pearson, J. E. and G. E. Jones, 1966. Soil Concentrations of "Emanating Radium-226" and the Emanation of Radon-222 from Soils and Plants, Tellus 18:655-662. Rogers, V., R. F. Overmeyer, C. M. Jensen and E. Canon, 1979. Characterization of Uranium Tailings Cover Material for Radon Flux Reduction, prepared byArgonne National Laboratory for Ford, Bacon and Davis Utah, Inc., FBONI-218-l. Silker, W. B., and P. G. Heasler, 1979. Diffusion and Exhalation of Radon from Uranium Tailings, NUREG/CR-1138, PNL-3207.
Silker, W. B. and P. G. Heasler, 1979. Diffusion and Exhalation of Radon from Uranium Tailings, NUREG/CR-1138, PNL-3207. Styra, B. I., 1968. Se1fpurging of theAtmosphere of Radioactive Contamination. Hydrometeorological publication, Leningrad, English translation by M. Lang. Strong, K. P. and D. M. Levins, 1982. Effect ofMoisture Content on Radon Emanation from Uranium Ore and Tailings, Health Physics, 42:27-32.
Tanner, A. B., 1980. Radon Migration in the Ground: review, in Natural Radiation Environment III, Vol. 1,

22 Asupplementary pp l-56.

### Thomas, V. W., K. K. Nielson, and M. L. Mauch, 1982, Radon and Aerosol Release from Open PitUranium Mining, NUREG/CR-2407, PNL-4071. Wilkening, M. H., W. E. Clements, and D. Stanley, 1972. Radon-222 Flux Measurements in Widely Separated Regions, The Natural Radiation Environment II, Proceedings of the Second International Symposium on the Natural Radiation Environment, Houston, Texas, pp. 717-730. Wilkening, M., 1977. Measurement ofRadon Flux bythe Accumulation Method, Workshop on Methods for Measuring Radiation in and Around Uranium Mills, Albuquerque, New Mexico, May 23-26, 1977, pp. 131-138.

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4.TITLEANDSUBTITLE/AddV_,_No.,iffiPProprN•I z.tu-bllltk} Recommended Procedures forMeasuring Radon Fluxes from Disposa1Sites of Residual Radioactive Materials 1 RECIPIENT'SACCESSION NO.

7.AUTHORIS) &.DATE REPORTCOMPLEJC.O 

### J.A. Young, 

## v.w. Thomas, and P.O. Jackson MONTH**~!lEA"** Februarv 1983
.
9.PERFORMING ORGANIZATION NAME AND MAILINGADDRESS (lrJChldeZip Co*) DATE REPORTISSUED
MONTH 

# 1rm Pacific Northwest Laboratory March Richland, 

### WA 99352 6.

### fL•-bl.nt)

8.a..- bl.nk)

12.SPONSORINGORGANIZATION NAME ANDMAILINGADDRESS (Inch/deZip Co*) 10.PROJECTfTASKIWORKUNITNO. Division ofWaste Management Off.ice ofNuclear Material Safety and Safeguards 11.CONTRACTNO. US Nuclear Regulatory Commission Washington, DC 20555 FIN 82216 

## 1"£"100 COVl,.EOUncJu,r,.IU,;rJ . 

### .. 13.TYPE OF REPORT Fina1 Report Sept., 1980 to March, 1983

15.SUPPLEMENTARY NOTES 14.**IU-I:Jir~ttl**

16.ABSTRACT QOOwonlrorltu} This report recommends instrumentation and methods '!'tlitable for measuring radon fluxes emanating from covered disposa1 sites ofresidual radioactive materials such

as uranium mill tailings. Problems of spatial and tempera1 variations in radon flux are discussed and the advantages Jnd disadvantages of several instruments are examined. Ayear-long measurement program and a two month measurement methodology
are then presented based on the inherent difficulties ofmeasuring average radon flux over a cover using the recommended inStrumentation.

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