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Reduction of radon progeny concentration in ordinary room due to a mixing fan
Nucl. Tracks Radiat. Meas., Vol. 15, Nos. 1-4, pp. 629.-632,1988 Int. Y. Radiat. Appl. lnstrum., Part D
0191-278X/89 $3.00 + .00 ~) 1989PergamonPresspie
Printed in Great Britain
R E D U C T I O N OF R A D O N P R O G E N Y CONCENTRATION IN O R D I N A R Y R O O M D U E TO A MIXING F A N F.
ABU-JARAD*
AND R . G .
SEXTRO**
*ENERGY RESOURCES D I V I S I O N , RESEARCH I N S T I T U T E KING FAHD UNIVERSITY OF PETROLEUM AND MINERALS DHAHRAN 3 1 2 6 1 , SAUDI ARABIA **APPLIED SCIENCE D I V I S I O N , LAWRENCE BERKELEY LABORATORY UNIVERSITY OF CALIFORNIA, BERKELEY,CALIFORNIA 9 4 7 2 0 , U.S.A.
ABSTRACT Three experiments were carried out at the Indoor Air Quality Research Rouse (IAQNH) a t Lawrence Berkeley Laboratory,University of California, to study the effect of operating a mixing fen on the radon progeny. In every experiment, about 15 K B q . • - 3 of radon was injected into a 36 • 3 o r d i n a r y room. Measurements were conducted with three different aerosol particle concentrations of about 1 0 2 , 104 a n d l 0 s p e r c • 3 . Real-time measurements of radon and progeny concentrations, particles,and environmental parameters were made through out the experiments. Measurements of plated-out activity on the surfaces of internal walls of the room were measured directly by filter papers and CR-39 nuclear track detectors, while on fan blades CR-39 detectors were used. The ratio of plated-out activity to the total progeny activity in the room varied fro• 17~ t o 8 4 Z . M o r e t h a n 9 9 ~ o f t h e p l a t e d - o u t activity w a s f o u n d on w a l l s a n d l e s s t h a n l Z on f e n b l a d e s . INTRODUCTION The e f f e c t of air turbulence by e mixing fan on the radon progeny was studied earlier in different cases, such as uranium mines z-2 , radon chambers ~-s and ordinary rooms 7-9. Generally, a reduction in the Working L e v e l (NL) w a s o b s e r v e d in all okses when the fen was on. The fate of the reduced radon progeny was mostly due to plate-out on to internal surfaces of the test space. The r a t i o of plate-out activity of radon progeny to the internal surfaces and to fan blades has always been s matter of debate among different authors. Measurements of plate-out activity on to internal surfaces was measured by filters, Aluminum foils zo and Nuclear Track Detectors s,11,12. Measurements of plate-out radon progeny in ordinary rooms are •ore representative of residence rooms than in chambers and mines, either because of the volume difference or internal surfaces materials. Different size containers showed different plate-out contributions la also different degree of plat-out was observed on various materials x3-14. This paper presents data on the experimental determination o f WL a n d t h e degree of plate-out on internal surfaces in ordinary rooms with walls ordinary building materials while e f a n was on e n d o f f w i t h t h r e e different aerosol particle concentrations. EXPERIMENTAL METHOD AND APPARATUS A-.....~fi~.~.....~ce.D.escr.i~t.ion.L The experiments were carried sut in e room which had been extensively weatherized to reduce the air infiltration rate below 0.1 ach. k floor plan of this room is shown in Figure 1. The interior of the room, measuring 3.4 x 4.6 x 2.3 • high, was constructed of plasterboard for three wails and ceiling, and plywood sheathing for the fourth wall. B._~9.mentat~on:The instrumentation employed in these tests was comprised of a highly automated data acquisition, monitoring, and control system installed at IAQRH. It is designed to yield real-time data on p a r t i c l e , radon, and radon progeny concentrations, and environmental parameters and to provide programmable control over the operatios of the experi•ent ¢ls-ls). Tests were conducted using tobacco smoke as a source of combustion particles because it is the most prevalent indoor particulate contamination. C...~R~_3~._.N~Gl.e.ar....Track..Detec.t.or: T h e C R - 3 9 n u c l e a r track detectors were used to register the alpha tracks from the plate-out activity on the internal walls surfaces, on f a n b l a d e s and on other exposed CR-39-detectors. Revealing 629
630
F. A B U - J A R A D and R. G. SEXTRO Table
: 1
Redan end proRsnv c o n c e n t r a t i o n in a i r of the t e s t roaB in the t h r e e d i f f e r e n t different experisante, Different particle c o n c e n t r a t i o n s ~are used in d i f f e r e n t R e l a t i v e h u m i d i t y and fan a p e r n t l u n c o n d i t i o n s oe eho~n in t h e t a b l e ,
phases i~ three expsrDnsnte, i
EXP~ PHASE NO. I
1
PERIOD (HAS)
FAN
: O N O E N S A T I O N RELATIVE CONCENTRATION ( P C I I L ) NEUCLI PER CC HUMIOITY X Rn-222 Pa-216 Pb-2lq I - 2 ) 10
MORKINGLEVEL (HI USING CRN CRAB SFLMP
PO-21q
1
5.0
OFF
37
319
130
90
55
0,84
0.~
2
4. t
ON
~1
257
100
17
12
0,21
3
5, 5
OFF
q3
199
110
50
32
0.23 (0.6) 0.49
r
E2
t
i 2
I
1
5,0
OFF
Yt
319
220
220
215
2
4, 0
ON
93
259
t30
55
50
3
5.0
OFF
q4
216
150
140
tqO
3
(8-'10) 10 53
•
,
4@- 10) I 0 Eq
2,14
2,t
0.59 (1,8) I.q
0.7
1
5,0
OFF
37
319
250
255
255
2.51
2.5
2
3, 9
ON
q2
250
215
205
205
2.1
3
5.5
OFF
93
214
190
190
185
2,02 (2.5) 1.85
t Radon and praRunv c o n c a n t r a t i o n a Found f a r the t h r e e phosaa at 3. 7 i 11,5 h r s f r a n the l i s a of s t o r t 0 n 9 the o a p o r l n o n t . t t The value o f gL on the b r a c k e t s , is the p r s d 0 c t n d v a l u e i f t h e fan ~oa nat on Jn the second phase c a l c u l a t e d from e x t r a p o l a t i o n o f fin and praRanv decoy curves and a i r oxchnnQo r a t e ,
Table
: 2
The e q u i v a l e n t volume a c t i v i t y f o r the t o t a l s u r f a c e n a t i v i t y af the rana and fan at end of f l r l t and ascend phases of each o x p o r 0 n e n t , c a l c u l a t e d from f ~ l t o r ' e r e s u l t s placed on q N o l l e end CR-39 t r a c k d e t e c t o r s r e s u l t s pIn©ed an 6 M o l l a (©ullll~lfl~ olfld F l o o r i n c l u d e d )ii. and an f n n blades, EXP. I
PHASE FAN I
TRRCKICM ON
TIME OF!THE EQUIVALENT EXPOSUR ;N SURFACES IN MALL SURFACES (HAS) (FAN BLADES) FILTER RESULTS (TRACK RESULTS Po-213
.
Pb-21Y
OF RADIOACTIVITY ROOM VOLUME FROM
FROM TRACK RESULTS
ON MALLS "RV, OF q" OH MALLS RV, OF l q ) Po-21q
ML
t
OFF
59Y9
5.0
150 121)
212 (173)
229 (165)
2,08 (I.70)
2
ON
3510 (31577)
q,I
122 71)
225 (t32)
2qO (140)
2.15 (1.25)
3
OFF
2577
5.5
1
OFF
1645
5.0
55 (50)
57 (53)
50 (qb)
0,53 (0,49)
2
ON
3q17 (21q57)
q.O
97 (95)
130 (125)
127 4122)
1,23 (I.19)
3
OFF
1851
5.0
I
OFF
1t91
5,0
3q (33)
25 42q)
qO 439)
0,31 (0, 30)
2
ON
1335 (28q0)
3.9
2q (25)
qO (HE)
56 (55)
0.52 (0.50)
3
OFF
1572
5.5 ~,.
THE EQUIVALENT OF RADIO. ON FAN BLADES IN ROOM SOL
Pa-216~Pb-21H Po-2I~
0,84
1.55
0.77
l
0.03
,
0,13
ML
1.55
0,015
I
O.OI
0,!9
~ ,
O, OOI
,j
r|) Rash a u r f o e a a a r l a : 5 0 , 5 0 ~ 2) Ran! ¥oluoa : 3G,57 ~ 3) T o t a l area of f a n ' s blades f r a a bath sldoo :150m5:900 ¢(4) The praQsnv c o n c e n t r a t i o n s d e t e r m i n e d 5r a ~ o t g h t a d l e n t t square aothad(Raabe Sores) 5) The aquas, s o l , n c t l v t ( v af the f i l t e r ' : ( A c t . on F o l t a r s ) t ( F l l t a r ores c i ) X 4665600 c i ) 1 ( 3 5 5 7 0 I) ~5) CR-39 d e t e c t o r s e f f i c i e n c y f o r qoonstv : O.T. 7) The s u r f a o s a l p h a n a t . at the end af each phase ¢aneldarad in e q u a l , ( p o r t e d q - 5 ~ r ¢ ) .
REDUCTION OF R A D O N PROGENY CONCENTRATION
631
Room inside dimensions
~1.~'1 ,~~~~ ,--, I
Radon and eernsol sampling i~m Radon i,~ectmn 1. Range led range hood 2. Rldon dlugltlM CltOUlieI Iftd llrOlol pllill iYlO(11to¢ 3. Atr.clelnlr location 4. AllormlliVe eir-cleener locatM~1 S. Cigafene-srnoldng mlcOinO
r -l,
2
~IIIIIIIIT;IIIA Figure In
t : F l o o r p l a n o f t h e room t e s t the Indoor fllr QualltT Roleorch
i
'm
epoce Houem.
(2)
(1) tq CR-39 dotottoro I q filtar¢ frocked on H o l l o e u r f o t e o
In
~"ill~lil~
(3)
5 hro
r
4 hre Fan on
Fen o F T ct
o
Rn
(q)
NoN I q C R - 3 9 o t l t k e d on N o l l e t I0 CR-38 cricked to~ord Noll'¢ turfocoe I0 CR-39 otltked toNord eurfotee oF C R - 3 9 on H o l l o * 6 CR-39 cricked t o N o r d Fen b l o d e ¢ ourfoteo, e 6 CR-39 ttzckod on C R - 3 9 Room v e n t . on Fen b l o d e o Hith mech. J 5-6 hr, Iven!:.t~!:
NoN I q C R - 3 9 t LI F i l t o r e etzckod on H o l l o t2 CR-39 tricked on f o n b l o d e ¢
Fen T ro Fen o f t and t o o k outelde oF
o
on Fan
FICURE: 2 P r o t o c o l
oF moth e x p e r l s o n t ,
fill
computerized
the
~notrueont¢
off
~ Fluoh Rn
out
Here t o n t ~ n u o u e l r
on (¢ee t e x t ) ,
room
. . . , • . . I
~
[xper+,,.ent =el
FIGURE 3: R l o u l t e of Contlnoul Rodon M o n l t o r (CRM) e n d Rodeo D o u g h t e r C o r o u t ¢ l (RDC) In the throe different oxporlnent¢ (toe tobl¢ I). 6.00
'... =.
11.00
. 16.00
21.00 Time (hi'S)
28.OO
~ • • • t . • • i • • ' i • • " Experiment 4 2 .
31.00
36.00
Experiment W3 ca
4"
'~
~ i
,
G.O0
,
,
i
t|.00
,
,
,
i
,
la.O0
,
,
i
,
,
21.00 T|me fhPs)
,
i
2B.O0
•
31.00
•
•
36.00
6.00
11.00
~
!
lG.O0
21.00 Time IIIPsl
/
, 28.00
1]..
, 31.00
36.00
632
F. A B U - J A R A D a n d R . G . S E X T R O
the alpha tracks was p e r f o r m e d by chemical etching. The etching conditions w e r e 30% KOH, 70 oC, a n d 9 h o u r s w i t h s t i r r e r . The tracks were counted by an optical microscope. Fourteen CR-39 detectors were arranged on the different walls of the room including the ceiling and floor before injecting radon. Two o t h e r s were placed on the two windows in the room. Four filter papers w e r e p l a c e d on e v e r y s i d e w a l l v e r y c l o s e to CR-39 detectors on walls. D~._Mixing__Fan: A t h r e e b l a d e d , plastic oscillating fan was used in part of the experiments. Area of one blade,s f a c e = 150 cm z ( i . e . the total area of the three blades = 3 x 2 x 150 = 9 0 0 c m Z ) . A t o t a l o f 12 C R - 3 9 detectors were attached to them before operation. Two d e t e c t o r s were placed on each sides one near the outer edge and the other near the axis. The t o t a l 88 o f t r a c k d e t e c t o r s were used throughout all the different phases of the experiment. E.._PKotocolofthe_exp~riment: The protocol of the daily experiment is shown i n F i g u r e 2 . The e x p e r i m e n t was repeated three times on three successive days with the same protocol for three different aerosol particle concentrations w h i c h w e r e a b o u t 10 z , 1 0 4 , l0 s respectively. Throughout the whole period of the experiment continuous monitoring for relative humidity, temperature, radon and progeny concentration and particle concentration were performed. RESULTS AND DISCUSSIONS R~on and_ P r o g e n x _ C o n c e n t K a t i q n : The readings of the four continuous Radon Monitors (CRN) and the Radon Daughter Caracole (RDC) for the three experiments are shown in Figure 3. The drop in the radon progeny concentrations due to air turbulence by the mixing fan is very clear with the l o w a n d m e d i u m CN c o n c e n t r a t i o n compared to the high concentration. Table 1 shows the analysis of each phase of the experiments ( i.e. at after 3, 7 and 12 h r s f r o m t h e s t a r t i n g time). Plated out aetiy~ty: At t h e t i m e of ending each phase, the surface alpha activity will be in equilibrium. The filters were removed and counted directly with alpha spectrometers while the 14 C R - 3 9 d e t e c t o r s were removed from the room and the plated out activity on their surfaces continued to decay. The e q u i v a l e n t volume activity to the total internal surface activity on t h e w a l l s and the total surface activity on fan blades at the end of the first and second phase of every experiment are shown in table 2. Conclusion: WL b a l a n c e for 6 phases from activity in the air, wall surfaces and fan blades were summed together and compared with the predicted value. The m e a s u r e d values were between 72~ a n d 95~ o f t h e p r e d i c t e d values. Less than 1~ o f t h e plated out activity was found on the fan blades and the remainder w a s on t h e w a l l s u r f a c e s . The f i r s t University
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.
author would of Petroleum
ACKNOWLEDGMENT like to thank the Research Institute of the and Minerals for its support to present this
King Fahd paper.
REFERENCES M. E . W r e n n , e t a l . Health Physics, 17, 405- (]969). J.D. Shreve and J.E. Cleveland. Am. I n d . H y g . A s s o e . 5 . 33,304(1972). R.F. Houlb,et al. Health Physics 36,497(1979). J. Bigu. Health Physics, 44, 266- (1983). S.N. Rudnick,et al. Pres. Int. meeting on radon and radon progeny meas. devices, Montgomery, Alabama,27-28 Aug. (1981). W.C. R i n d s , a t al. pres. at the 75th annual meeting o f APCA, New Orleans, Louisiana,20-25 June (1982). N. J o n a s a e n . Pres. at Nat. Rad. in our Env.,Nordic soc. for Rad. Prot., Geilo,6-9 Jan. (1980). F. A b u - J a r a d , J.H. Fremlin. Health Physics, 42, 82- (1982). A. W i c k a n d 5 . P o r s t e n d o e r f e r . Presented at the 2nd special symp. Nat. Rad. Env. , Bombay, India, 19-23 Jan. (1981). A.C. George, E.O. Knutson and K.W.Tv. Health Physics,4_5_, 439- (1983). B.Kahn, Z.wang, and E.Sensintaffar, Nuc. Inst. Meth,219, 419- (1984). R.H. McCorkell a n d W.C. J e f f r e y . Geochem. Expl. 5., 10., 2 2 7 - ( 1 9 7 8 ) . 5. Bigu. Aerosol Science J. (1984). J. Bigu, to be published. W.W.Nazaroff,K.L.Revzan and A.W.Robb. pres. a t I n t . Symp. on I n d o o r Air PollutionsHealth and Energy Conser.,Amherst,MA,13-16 Oct. (1981). W.W. N a z a r o f f , M . L . B o e g e l , and A.V.Nero. LBL r e p . ( L B L - 1 2 4 8 4 ) , B e r k . CA. 5.W. Thomas and R.5. Countes. Health Physics, 36,734(1979). W.W. N a z a r o f f . Review of sientific Inst., 54,1227(1983).
0191-278X/89 $3.00 + .00 ~) 1989PergamonPresspie
Printed in Great Britain
R E D U C T I O N OF R A D O N P R O G E N Y CONCENTRATION IN O R D I N A R Y R O O M D U E TO A MIXING F A N F.
ABU-JARAD*
AND R . G .
SEXTRO**
*ENERGY RESOURCES D I V I S I O N , RESEARCH I N S T I T U T E KING FAHD UNIVERSITY OF PETROLEUM AND MINERALS DHAHRAN 3 1 2 6 1 , SAUDI ARABIA **APPLIED SCIENCE D I V I S I O N , LAWRENCE BERKELEY LABORATORY UNIVERSITY OF CALIFORNIA, BERKELEY,CALIFORNIA 9 4 7 2 0 , U.S.A.
ABSTRACT Three experiments were carried out at the Indoor Air Quality Research Rouse (IAQNH) a t Lawrence Berkeley Laboratory,University of California, to study the effect of operating a mixing fen on the radon progeny. In every experiment, about 15 K B q . • - 3 of radon was injected into a 36 • 3 o r d i n a r y room. Measurements were conducted with three different aerosol particle concentrations of about 1 0 2 , 104 a n d l 0 s p e r c • 3 . Real-time measurements of radon and progeny concentrations, particles,and environmental parameters were made through out the experiments. Measurements of plated-out activity on the surfaces of internal walls of the room were measured directly by filter papers and CR-39 nuclear track detectors, while on fan blades CR-39 detectors were used. The ratio of plated-out activity to the total progeny activity in the room varied fro• 17~ t o 8 4 Z . M o r e t h a n 9 9 ~ o f t h e p l a t e d - o u t activity w a s f o u n d on w a l l s a n d l e s s t h a n l Z on f e n b l a d e s . INTRODUCTION The e f f e c t of air turbulence by e mixing fan on the radon progeny was studied earlier in different cases, such as uranium mines z-2 , radon chambers ~-s and ordinary rooms 7-9. Generally, a reduction in the Working L e v e l (NL) w a s o b s e r v e d in all okses when the fen was on. The fate of the reduced radon progeny was mostly due to plate-out on to internal surfaces of the test space. The r a t i o of plate-out activity of radon progeny to the internal surfaces and to fan blades has always been s matter of debate among different authors. Measurements of plate-out activity on to internal surfaces was measured by filters, Aluminum foils zo and Nuclear Track Detectors s,11,12. Measurements of plate-out radon progeny in ordinary rooms are •ore representative of residence rooms than in chambers and mines, either because of the volume difference or internal surfaces materials. Different size containers showed different plate-out contributions la also different degree of plat-out was observed on various materials x3-14. This paper presents data on the experimental determination o f WL a n d t h e degree of plate-out on internal surfaces in ordinary rooms with walls ordinary building materials while e f a n was on e n d o f f w i t h t h r e e different aerosol particle concentrations. EXPERIMENTAL METHOD AND APPARATUS A-.....~fi~.~.....~ce.D.escr.i~t.ion.L The experiments were carried sut in e room which had been extensively weatherized to reduce the air infiltration rate below 0.1 ach. k floor plan of this room is shown in Figure 1. The interior of the room, measuring 3.4 x 4.6 x 2.3 • high, was constructed of plasterboard for three wails and ceiling, and plywood sheathing for the fourth wall. B._~9.mentat~on:The instrumentation employed in these tests was comprised of a highly automated data acquisition, monitoring, and control system installed at IAQRH. It is designed to yield real-time data on p a r t i c l e , radon, and radon progeny concentrations, and environmental parameters and to provide programmable control over the operatios of the experi•ent ¢ls-ls). Tests were conducted using tobacco smoke as a source of combustion particles because it is the most prevalent indoor particulate contamination. C...~R~_3~._.N~Gl.e.ar....Track..Detec.t.or: T h e C R - 3 9 n u c l e a r track detectors were used to register the alpha tracks from the plate-out activity on the internal walls surfaces, on f a n b l a d e s and on other exposed CR-39-detectors. Revealing 629
630
F. A B U - J A R A D and R. G. SEXTRO Table
: 1
Redan end proRsnv c o n c e n t r a t i o n in a i r of the t e s t roaB in the t h r e e d i f f e r e n t different experisante, Different particle c o n c e n t r a t i o n s ~are used in d i f f e r e n t R e l a t i v e h u m i d i t y and fan a p e r n t l u n c o n d i t i o n s oe eho~n in t h e t a b l e ,
phases i~ three expsrDnsnte, i
EXP~ PHASE NO. I
1
PERIOD (HAS)
FAN
: O N O E N S A T I O N RELATIVE CONCENTRATION ( P C I I L ) NEUCLI PER CC HUMIOITY X Rn-222 Pa-216 Pb-2lq I - 2 ) 10
MORKINGLEVEL (HI USING CRN CRAB SFLMP
PO-21q
1
5.0
OFF
37
319
130
90
55
0,84
0.~
2
4. t
ON
~1
257
100
17
12
0,21
3
5, 5
OFF
q3
199
110
50
32
0.23 (0.6) 0.49
r
E2
t
i 2
I
1
5,0
OFF
Yt
319
220
220
215
2
4, 0
ON
93
259
t30
55
50
3
5.0
OFF
q4
216
150
140
tqO
3
(8-'10) 10 53
•
,
4@- 10) I 0 Eq
2,14
2,t
0.59 (1,8) I.q
0.7
1
5,0
OFF
37
319
250
255
255
2.51
2.5
2
3, 9
ON
q2
250
215
205
205
2.1
3
5.5
OFF
93
214
190
190
185
2,02 (2.5) 1.85
t Radon and praRunv c o n c a n t r a t i o n a Found f a r the t h r e e phosaa at 3. 7 i 11,5 h r s f r a n the l i s a of s t o r t 0 n 9 the o a p o r l n o n t . t t The value o f gL on the b r a c k e t s , is the p r s d 0 c t n d v a l u e i f t h e fan ~oa nat on Jn the second phase c a l c u l a t e d from e x t r a p o l a t i o n o f fin and praRanv decoy curves and a i r oxchnnQo r a t e ,
Table
: 2
The e q u i v a l e n t volume a c t i v i t y f o r the t o t a l s u r f a c e n a t i v i t y af the rana and fan at end of f l r l t and ascend phases of each o x p o r 0 n e n t , c a l c u l a t e d from f ~ l t o r ' e r e s u l t s placed on q N o l l e end CR-39 t r a c k d e t e c t o r s r e s u l t s pIn©ed an 6 M o l l a (©ullll~lfl~ olfld F l o o r i n c l u d e d )ii. and an f n n blades, EXP. I
PHASE FAN I
TRRCKICM ON
TIME OF!THE EQUIVALENT EXPOSUR ;N SURFACES IN MALL SURFACES (HAS) (FAN BLADES) FILTER RESULTS (TRACK RESULTS Po-213
.
Pb-21Y
OF RADIOACTIVITY ROOM VOLUME FROM
FROM TRACK RESULTS
ON MALLS "RV, OF q" OH MALLS RV, OF l q ) Po-21q
ML
t
OFF
59Y9
5.0
150 121)
212 (173)
229 (165)
2,08 (I.70)
2
ON
3510 (31577)
q,I
122 71)
225 (t32)
2qO (140)
2.15 (1.25)
3
OFF
2577
5.5
1
OFF
1645
5.0
55 (50)
57 (53)
50 (qb)
0,53 (0,49)
2
ON
3q17 (21q57)
q.O
97 (95)
130 (125)
127 4122)
1,23 (I.19)
3
OFF
1851
5.0
I
OFF
1t91
5,0
3q (33)
25 42q)
qO 439)
0,31 (0, 30)
2
ON
1335 (28q0)
3.9
2q (25)
qO (HE)
56 (55)
0.52 (0.50)
3
OFF
1572
5.5 ~,.
THE EQUIVALENT OF RADIO. ON FAN BLADES IN ROOM SOL
Pa-216~Pb-21H Po-2I~
0,84
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REDUCTION OF R A D O N PROGENY CONCENTRATION
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F. A B U - J A R A D a n d R . G . S E X T R O
the alpha tracks was p e r f o r m e d by chemical etching. The etching conditions w e r e 30% KOH, 70 oC, a n d 9 h o u r s w i t h s t i r r e r . The tracks were counted by an optical microscope. Fourteen CR-39 detectors were arranged on the different walls of the room including the ceiling and floor before injecting radon. Two o t h e r s were placed on the two windows in the room. Four filter papers w e r e p l a c e d on e v e r y s i d e w a l l v e r y c l o s e to CR-39 detectors on walls. D~._Mixing__Fan: A t h r e e b l a d e d , plastic oscillating fan was used in part of the experiments. Area of one blade,s f a c e = 150 cm z ( i . e . the total area of the three blades = 3 x 2 x 150 = 9 0 0 c m Z ) . A t o t a l o f 12 C R - 3 9 detectors were attached to them before operation. Two d e t e c t o r s were placed on each sides one near the outer edge and the other near the axis. The t o t a l 88 o f t r a c k d e t e c t o r s were used throughout all the different phases of the experiment. E.._PKotocolofthe_exp~riment: The protocol of the daily experiment is shown i n F i g u r e 2 . The e x p e r i m e n t was repeated three times on three successive days with the same protocol for three different aerosol particle concentrations w h i c h w e r e a b o u t 10 z , 1 0 4 , l0 s respectively. Throughout the whole period of the experiment continuous monitoring for relative humidity, temperature, radon and progeny concentration and particle concentration were performed. RESULTS AND DISCUSSIONS R~on and_ P r o g e n x _ C o n c e n t K a t i q n : The readings of the four continuous Radon Monitors (CRN) and the Radon Daughter Caracole (RDC) for the three experiments are shown in Figure 3. The drop in the radon progeny concentrations due to air turbulence by the mixing fan is very clear with the l o w a n d m e d i u m CN c o n c e n t r a t i o n compared to the high concentration. Table 1 shows the analysis of each phase of the experiments ( i.e. at after 3, 7 and 12 h r s f r o m t h e s t a r t i n g time). Plated out aetiy~ty: At t h e t i m e of ending each phase, the surface alpha activity will be in equilibrium. The filters were removed and counted directly with alpha spectrometers while the 14 C R - 3 9 d e t e c t o r s were removed from the room and the plated out activity on their surfaces continued to decay. The e q u i v a l e n t volume activity to the total internal surface activity on t h e w a l l s and the total surface activity on fan blades at the end of the first and second phase of every experiment are shown in table 2. Conclusion: WL b a l a n c e for 6 phases from activity in the air, wall surfaces and fan blades were summed together and compared with the predicted value. The m e a s u r e d values were between 72~ a n d 95~ o f t h e p r e d i c t e d values. Less than 1~ o f t h e plated out activity was found on the fan blades and the remainder w a s on t h e w a l l s u r f a c e s . The f i r s t University
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.
author would of Petroleum
ACKNOWLEDGMENT like to thank the Research Institute of the and Minerals for its support to present this
King Fahd paper.
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